Fish M a n a g e m e lil ■■'•v. ■••. • ^■. m:mm Department of the Interiof U.S. Fish and Wildlife Service Fish Hatchery Management Third printing, with corrections, 1986 ISBN 0-913235-03-2 This publication has, been reprinted by the American Fisheries Society in cooperation with the Fish and Wildlife Service but at no expense to the U.S. Government. Trade and company names mentioned in this publication are for informational purposes only. It does not imply U.S. Government endorsement of the product. All uses of fishery compounds must be registered by appropriate State and/or Federal agencies. Only those uses described on the label are permitted and only at the rates listed. /-r A Fish Hatchery Management Robert G. Piper Ivan B. McElwain Leo E. Orme Joseph P. McCraren Laurie G. Fowler John R. Leonard \ Special Advisors Arden J. Trandahl Vicky Adriance United States Department of the Interior Fish and Wildlife Service Washington, D. C. 1982 4:" ^ O O O MARINE BIOLOGICAL UBORATORY LIBRARY VV. H. 0 i 1930 J. T. Bowen Jack Bess This publication is dedicated to J. T. Bowen Jack Bess whose initial efforts and dedication inspired us all to accomplish the task. Contents Preface xv Abbreviations Used in the Text xix Common and Scientific Names of Fish Species Cited in the Text xxi 1: Hatchery Requirements Water Quality 3 Temperature 3 Dissolved Gases 4 Oxygen 5 Nitrogen 8 Carbon Dioxide 9 Toxic Gases 10 Dissolved Gas Criteria 70 Suspended and Dissolved Solids JO Suspended Solids 70 Acidity 7 7 Alkalinity and Hardness 11 Total Dissolved Solids 12 Toxic Materials 12 Heavy Metals 13 Salinity 13 Turbidity 14 vi IISH HAiCllKRV MANAGEMENT Pesticides 15 Water Supply and Treatment 16 Treatment of Incoming Water 16 Temperature Control 16 Aeration / 7 Sterilization / 7 Treatment of Water for Reuse 19 Ammonia Toxicity 20 Biological Removal of Ammonia 21 Ion Exchange Removal of Ammonia 22 Other Ammonia Removal Techniques 23 Estimation of Ammonia 24 Treatment of Effluent Water and Sludge 25 Hatchery Pollutants 26 Sedimentation Basins 27 Solid Waste Disposal 30 Hatchery Design 32 Buildings 33 Egg Incubation 39 Rearing Facilities 40 Circular Rearing Units 40 Swedish Pond 43 Rectangular Tanks and Raceways 43 Rectangular Circulation Rearing Pond 46 Earthen Ponds 47 Cage Culture 48 Pen Rearing 50 Selection of Rearing Facilities 50 Biological Design Criteria 51 Application of Biological Criteria 54 Bibliography 55 2: Hatchery Operations Production Methods 60 Length- Weight Relationships 60 Growth Rate 61 Growth at Variable Water Temperatures 62 Carrying Capacity 63 Flow Index 67 Density Index 71 Warmwater Fish Rearing Densities 75 Largemouth Bass 75 CONTENTS vu Bluegill 76 Channel Catfish 16 High-Density Catfish Culture 11 Striped Bass 11 Northern Pike and Walleye 11 Inventory Methods 18 Intensive Culture 19 Extensive Culture 81 Fish Grading 83 Fish Handling and Harvesting 84 Rearing Unit Management 88 Sanitation 88 Water Supply Structures 90 Screens 57 Pond Management 91 Preseason Preparation 5/ Wild- Fish Control 93 Fertilization Procedures 94 Organic Fertilizers 91 Inorganic Fertilizers 98 Combining Fertilizers 707 Aquatic Vegetation Control 702 Special Problems in Pond Culture 705 Dissolved Oxygen 705 Acidity 7 70 Turbidity 7 72 Hydrogen Sulfide 7 72 Water Loss 7 13 Problem Organisms 7 7J Recordkeeping 114 Factors to be Considered 7 74 Production Summary 116 Lot History Production Charts 7 7 7 Definitions 7 75 Instructions 7 75 Totals and Averages 122 Hatchery Production Summary 722 Definitions 722 Instructions 72J Totals and Averages 124 Warmwater Pond Records 126 Bibliography 725 viii FISH HATCHERY MANAGEMEN 1 3: Broodstock, Spawning, and Egg Handling Broodstock Management 131 Aquisition of Broodstock 1 32 Care and Feeding of Broodfish 1 32 Forage Fish 140 White Sucker 140 Fathead Minnow 141 Goldfish 142 Golden Shiner 143 Tilapia 144 Improvement of Broodstocks 1 44 Selective Breeding 144 Hybridization and Crossbreeding 148 Spawning 149 Natural Spawning Method 149 Salmonid Fishes 750 Warmwater Fishes 750 Artificial Spawning Method 756" Factors Affecting Fertilization 76^7 Gamete Storage 168 Anesthetics 76^5 Artificial Control of Spawning Time 7 70 Photoperiod 7 70 Hormone Injection 7 71 Egg Incubation and Handling 173 Egg Development 7 74 Sensitive Stage 7 75 Eyed Stage 7 75 Enumeration and Sorting of Eggs 7 75 Egg Disinfection 1 89 Incubation Period 189 Factors Affecting Egg Development 1 90 Light 190 Temperature 757 Oxygen 752 Transportation of Eggs 1 93 Types of Incubators 1 93 Hatching Trays 1 93 Clark- Williamson Trough 1 94 Catfish Troughs 755 Hatching Baskets 755 Hatching Jars 755 CONTENTS ix Montana Hatching Box 196 Vertical-Tray Incubators 75 7 Simulated Natural Conditions and Rearing Pond Incubation 1 99 Bibliography 200 4: Nutrition and Feeding Nutrition 208 Factors Influencing Nutritional Requirements 270 Water Temperature 270 Species, Body Size, and Age 27 7 Physiological Changes 27 7 Other Environmental Factors 272 Digestion and Absorption of Nutrients 2 72 Oxygen and Water Requirements 213 Protein Requirements 214 Protein in Salmonid Feeds 2 75 Protein in Catfish Feeds 2 7 6^ Protein in Coolwater Fish Feeds 27 7 Carbohydrate Requirements 27 7 Carbohydrates in Salmonid Feeds 2 75 Carbohydrates in Catfish Feeds 2 75 Lipid Requirements 220 Lipid Requirements for Salmonids 22 7 Lipid Requirements for Catfish 224 Energy Requirements 224 Energy Requirements for Salmonids 225 Energy Requirements for Catfish 226 Vitamin Requirements 227 Mineral Requirements 229 Nonnutritive Factors 2J7 Fiber 2J7 Pigment-Producing Factors 232 Antioxidants 232 Materials Affecting Fish Quality and Flavor 232 Organic Toxicants in Feeds 233 Sources of Feeds 233 Natural Foods 233 Formulated Feeds 234 Feed Manufacturing 234 Open- and Closed- Formulated Feeds 235 Handling and Storing Procedures 236 Feed Evaluation 238 X riSlI 11 AltllKKV MANACr.MKNT Feeding 238 Feeding Guides for Salmonids 239 Feeding Guides for Coolwater Fishes 248 Feeding Guides for Warmwater Fishes 249 Catfish 249 Largemouth and Smallmouth Bass 252 Striped Bass 254 Time of Initial Feeding 254 Feeding Frequency 255 Feed Sizes 257 Feeding Methods 259 Bibliography 260 5: Fish Health Management Disease Characteristics 264 Disease-Causing Organisms 264 Disease Recognition 264 Stress and Its Relationship to Disease 265 Disease Treatment 266 Treatment Methods 268 Dip Treatment 270 Prolonged Bath 271 Indefinite Bath 2 77 Flush Treatment 2 72 Constant-Flow Treatment 272 Feeding and Injection 273 General Information on Chemicals 274 Chemicals and Their Uses 275 Salt Baths and Dips 275 Formalin 275 Copper Sulfate 276 Potassium Permanganate (KMnO,) 277 Quaternary Ammonium Compounds 278 Terramycin" 279 Nitrofurans 280 Sulfonamides 281 Acriflavine 281 Calcium Hydroxide 282 lodophores 282 Di-«-Butyl Tin Oxide 282 Masoten® 282 Equipment Decontamination 283 Facility Decontamination 284 CONTENTS xi Elimination of Fish 284 Preliminary Operations 284 Decontamination 285 Maintenance of the Hatchery 285 Defense Mechanisms of Fishes 286 Immunization of Fishes 288 Vaccination Methods 288 Fish Disease Policies and Regulations 289 Diseases of Fish 294 Viral Diseases 294 Infectious Pancreatic Necrosis (iPN) 294 Viral Hemorrhagic Septicemia (VHS) 295 Infectious Hematopoietic Necrosis (IHN) 296 Channel Catfish Virus Disease (CCV) 298 Herpesvirus Disease of Salmonids 298 Lymphocystis Disease 299 Bacterial Diseases 300 Bacterial Gill Disease 300 Columnaris Disease 302 Peduncle Disease 303 Fin Rot 304 Furunculosis 304 Enteric Redmouth (ERM) 306 Motile Aeromonas Septicemia (MAS) 307 Vibriosis 310 Kidney Disease 312 Fungus Diseases 314 Protozoan Diseases 315 External Protozoan Diseases 315 Ichtyobodo 315 Ichthyophthirius 316 Chilodonella 319 Epistylis 319 Trie hod ina 320 Ambiphrya 321 Trichophrya 323 Internal Protozoan Diseases 323 Hexamita 323 Henneguya 324 Ceratomyxa 326 Myxosoma 32 7 Pleistophora 328 Trematode Diseases (Monogenetic) 329 Gyrodactylus 330 xii 115.11 iiAiciii.RV manac;i:mi:ni Dactylogyrus 330 Cleidodiscus 330 Trematode Diseases (Digenetic) 332 Sanguinkola 332 Copepod Parasites 333 Argil lus 334 Lernaea 334 Packing and Shipping Specimens 335 Shipping Live Specimens 340 Shipping Preserved Specimens 341 Fish Disease Leaflets 342 Bibliography 344 6: Transportation of Live Fishes Transportation Equipment 348 Vehicles 348 Tank. Design 350 Circulation 352 Aeration 353 Water Quality 355 Oxygen 355 Temperature 356 Ammonia 357 Carbon Dioxide 357 Buffers 358 Handling, Loading, and Stocking 358 Stress 358 Anesthetics 359 Carrying Capacity 360 Trout and Salmon 361 Channel Catfish 362 Largemouth Bass, Bluegill, and Other Centrarchids 363 Striped Bass 363 Northern Pike, Muskellunge, and Walleye 364 Stocking Fish 364 Shipping Fish in Small Containers 366 Bibliography 368 Appendices Appendix A: English-Metric and Temperature Conversion Tables 375 CONTENTS Xlll Append Append Append Append Append Append Append X B: X C: X D: X E: X F: X G: X H: Appendix I: Ammonia Ionization 378 Volumes and Capacities of Circular Tanks 383 Use of Weirs to Measure Flow 384 Hatchery Codes for Designating Fish Lots 387 Nutritional Diseases and Diet Formulations 390 Chemical Treatments: Calculations and Constant Flow Delivery 401 Drug Coatings for Feed Pellets 405 Length-Weight Tables 406 Glossary 469 Index 503 Preface The most recent Fish Cultural Manual published by the United States Fish and Wildlife Service was authored by Lynn H. Hutchens and Robert C. Nord in 1953. It was a mimeographed publication and was so popular that copies were jealously sought by fish culturists across the country; it soon was unavailable. In 1967, the Service's Division of Fish Hatcheries began to develop a Manual of Fish Culture, with J. T. Bowen as Editor. Several sections were published in ensuing years. Efforts to complete the manual waned until 1977 when, due to the efforts of the American Fisheries Society and of the Associate Director for Fishery Resources, Galen L. Buterbaugh, a task force was established to develop and complete this publication. As task- force members, our first business was to identify the audience for this publication. We decided that we could be most helpful if we pro- duced a practical guide to efficient hatchery management for practicing fish culturists. Research and hatchery biologists, bioengineers, and micro- biologists will not find the in-depth treatment of their fields that they might expect from a technical publication. For example, we offer a guide that will help a hatchery manager to avoid serious disease problems or to recognize them if they occur, but not a detailed description of all fish diseases, their causative agents, treatment, and control. Similarly, we out- line the feed requirements and proper feeding methods for the production of healthy and efficiently grown fish, but do not delve deeply into the biochemistry or physiology of fish nutrition. XV xvi FISH HAICHERV MANAGEMENT The format of Fisli Hatchery Management is functional: hatchery require- ments and operations; broodstock management and spawning; nutrition and feeding; fish health; fish transportation. We have tried to emphasize the principles of hatchery culture that are applicable to many species of fish, whether they are from warmwater, coolwater, or coldwater areas of the continent. Information about individual species is distributed through the text; with the aid of the Index, a hatchery manager can assemble detailed profiles of several species of particular interest. In the broad sense, fish culture as presented in Fish Hatchery Management encompasses not only the classical "hatchery" with troughs and raceways (intensive culture), but also pond culture (extensive culture), and cage and pen culture (which utilizes water areas previously considered inappropriate for rearing large numbers of fish in a captive environment). The coolwater species, such as northern pike, walleye, and the popular tiger muskie, tradi- tionally were treated as warmwater species and were extensively reared in dirt ponds. These species now are being reared intensively with increasing success in facilities traditionally associated with salmonid (coldwater) species. We have no pretense of authoring an original treatise on fish culture. Rather, we have assembled existing information that we feel is pertinent to good fish hatchery management. We have quoted several excellent litera- ture sources extensively when we found we could not improve on the author's presentation. We have avoided literature citations in the text, but a bibliography is appended to each chapter. We have utilized unpublished material developed by the United States Fish and Wildlife Service; Dale D. Lamberton's use of length-weight tables and feeding rate calculations, and his procedures for projecting fish growth and keeping hatchery records have been especially useful. Thomas L. Wellborn's information on fish health management greatly strengthened the chapter on that subject. Many people have helped us prepare this manual. Our special recogni- tion and appreciation go to Ms. Florence Jerome whose dedication and diligent efforts in typing several manuscript drafts, and in formating tables and figures, allowed us to complete the book. Roger L. Herman and the staff of the National Fisheries Research and Development Laboratory, Wellsboro, Pennsylvania, supported the project and assisted in preparation of the manuscript. We greatly appreciate review comments contributed by federal, state, university, and private people: James W. Avault; Jack D. Bayless; Claude E. Boyd; Earnest L. Brannon; Carol M. Brown; Keen Buss; Harold E. Cal- bert; James T. Davis; Bernard Dennison; Lauren R. Donaldson; Ronald W. Goede; Delano R. Graff; William K. Hershberger; John G. Hnath; Shyrl E. Hood; Donald Horak; Janice S. Hughes; William M. Lewis; David O. Locke; Richard T. Lovell; J. Mayo Martin; Ronald D. Mayo; PREFACE xvii David W. McDaniel; Fred P. Meyer; Cliff Millenbach; Edward R. Miller; Wayne Olson; Keith M. Pratt; William H. Rogers; Raymond C. Simon; Charlie E. Smith; R. Oneal Smitherman; Robert R. Stickney; Gregory J. Thomason; Otto W. Tiemeier; Thomas L. Wellborn; Harry Westers. All these people improved the manual's accuracy and content. Carl R. Sul- livan, Executive Director of the American Fisheries Society, helped to stimulate the creation of our task force, and his continued interest in this project has been a source of strength. There was much encouragement and effort by many other people who have gone unmentioned. To all those who took any part in the develop- ment and publication of the Fish Hatchery Management, we express our grat- itude. Lastly, I would like to recognize the guidance, perserverance, tact, and friendship shown to the task force by Robert Kendall, who provided edi- torial review through the American Fisheries Society. Without his involve- ment, the task force would not have accomplished its goal. Robert G. Piper, Editor-in-Chief Abbreviations Used in the Text BHA butylhydroxyanisole BHT butylhydroxytoluene BOD biochemical oxygen demand BTU British thermal unit C condition factor (English units) °C degrees centigrade or Celsius cal calories cc cubic centimeter CFR Code of Federal Regulations cm centimeter cu ft cubic foot D density index DO dissolved oxygen EPA Environmental Protection Agency et al. and others F flow index °F degrees Fahrenheit ft foot FWS Fish and Wildlife Service g gram(s) gal gallon(s) gpm gallon(s) per minute XIX FISH HArCIIF.RV MANAGF.MKM' GVW gross vehicle weight HCG human chorionic gonadotrophin / water inflow i.m. intramuscular i.p. intraperitoneal lU international units K condition factor (metric units); insulation factor kcal kilocalorie L length (total) lb pound lbs pounds LHP Lot History Production Chart m meter(s) mg milligram(s) min minute ml milliliter mm millimeter MS-222 tricaine methane sulfonate N nitrogen NRC National Research Council O.D. outside diameter oz ounce P phosphorous P.C. Public Code PCB polychlorinated biphenols ppb part(s) per billion ppm part(s) per million ppt part(s) per thousand psi pound(s) per square inch SET standard en\ ironmental temperatures sp. species sq ft square foot (feet) T.H. total hardness TU temperature units Mg microgram US United States USP United States Pharmaceutical V volume of raceway in cubic feet w total weight W.P. wettable powder Wt weight Zn zinc Common and Scientific Names of Fishes Cited in the Text American eel American shad Arctic char Atlantic salmon Black bullhead Blueback salmon Blue catfish Bluegill Brook trout Brown bullhead Brown trout Buffalo Chain pickerel Channel catfish Chinook salmon Chum salmon Coho salmon Common carp Cutthroat trout Dog salmon Fathead minnow Flathead catfish Anguilla rostra ta Alosa sapidissima Salvelinus alpinus Salmo salar Ictalurus melas see sockeye salmon Ictalurus furcatus Lepomis niacrochirus Salvelinus fontinalis Ictalurus nebulosus Salmo trutta Ictiobus spp. Esox niger Ictalurus punctatus Oncorhynchus tshawytscha Oncorhynchus keta Oncorhynchus kisutch Cyprinus carpio Salmo clarki see chum salmon Pimep hales promelas Pylodictis olivaris XX! XXll FISH HAICIIKKV M ANAGKMKN I Grass carp Golden shiners Goldfish Green sunfish Guppy Herring Lake trout Largemouth bass Muskellunge Northern pike Pink salmon Pumpkinseed Rainbow trout Redbreast sunfish Redear sunfish Sauger Sea lamprey Sculpin Smallmouth bass Sockeye salmon Steelhead Striped bass Tench Threadfin shad Tilapia Walleye White catfish Whitefish White sucker Yellow perch Ctenopharyngodon idella Nolemigonus crysoleucas Carassius auratus Lepomis cyanellus Poecilia reticulata Clupea harengus Salvelinus namaycush Micropterus salmoides Esox masquinongy Esox lucius Oncorhynchus gorbuscha Lepomis gibbosus Salmo gairdneri Lepomis auritus Lepomis micro lop bus Stizostedion canadense Petromyzon marinus Cottus spp. Micropterus dolomieui Oncorhynchus nerka see rainbow trout Morone saxatilis Tinea tinea Dorosoma petenense Tilapia spp. Stizostedion vitreum vitreum Ictalurus cat us Coregonus spp. Catostomus commersoni Perca flavescens Fish Hatchery Management 1 Hatchery Requirements The efficient operation of a fish hatchery depends on a number of factorb. Among these are suitable site selection, soil characteristics, and water qual- ity. Adequate facility design, water supply structures, water source, and hatchery effluent treatment must also be considered. This chapter will identify the more important hatchery requirements and the conditions necessary for an efficient operation. Water Quality Water quality determines to a great extent the success or failure of a fish cultural operation. Physical and chemical characteristics such as suspended solids, temperature, dissolved gases, pH, mineral content, and the potential danger of toxic metals must be considered in the selection of a suitable wa- ter source. Temperature No other single factor affects the development and growth of fish as much as water temperature. Metabolic rates of fish increase rapidly as tempera- tures go up. Many biological processes such as spawning and egg hatching 4 FISH HATCHF.RY MANAGKMF.NI' are geared to annual temperature changes in the natural environment. Each species has a temperature range that it can tolerate, and within that range it has optimal temperatures for growth and reproduction. These op- timal temperatures may change as a fish grows. Successful hatchery opera- tions depend on a detailed knowledge of such temperature influences. The temperature requirements for a fish production program should be well defined, because energy must be purchased for either heating or cool- ing the hatchery water supply if unsuitable temperatures occur. First con- sideration should be to select a water supply with optimal temperatures for the species to be reared or, conversely, to select a species of fish that thrives in the water temperatures naturally available to the hatchery. It is important to remember that major temperature differences between hatchery water and the streams into which the fish ultimately may be stocked can greatly lower the success of any stocking program to which hatchery operations may be directed. Within a hatchery, temperatures that become too high or low for fish impart stresses that can dramatically affect production and render fish more susceptible to disease. Most chemical sub- stances dissolve more readily as temperature increases; in contrast, and of considerable importance to hatchery operations, gases such as oxygen and carbon dioxide become less soluble as temperatures rise. Some suggested temperature limits for commonly cultured species are presented in Chapter 3, Table 17. Dissolved Gases Nitrogen and oxygen are the two most abundant gases dissolved in water. Although the atmosphere contains almost four times more nitrogen than oxygen in volume, oxygen has twice the solubility of nitrogen in water. Therefore, fresh water usually contains about twice as much nitrogen as oxygen when in equilibrium with the atmosphere. Carbon dioxide also is present in water, but it normally occurs at much lower concentrations than either nitrogen or oxygen because of its low concentration in the atmos- phere. All atmospheric gases dissolve in water, although not in their atmospher- ic proportions; as mentioned, for example, oxygen is over twice as soluble as nitrogen. Natural waters contain additional dissolved gases that result from erosion of rock and decomposition of organic matter. Several gases have implications for hatchery site selection and management. Oxygen must be above certain minimum concentrations. Other gases must be kept below critical lethal concentrations in hatchery or pond water. As for other aspects of water quality, inappropriate concentrations of dissolved gases in source waters mean added expense for treatment facilities. HATCHERY REQUIREMENTS Corr«cl>Ofl F»c ors 'O' O ■ ygen Saiu' ai.on at V ■ rous Alt (•Jo<> Oxygen mgm per liter (PPM) 5 6 7 8 9 10 11 12 13 H 15 16 17 iJijji|i,iul||i,iii;ii|l|i,i|ii|i|iJrii|i|i;iNlMi|i ||lMl|lll^|lM|I^Nil»^lM|||ll|lM|l||||;|||^||l||^|;l^lMlM|||l^||^l|P|||^ I'l'I'M^'i'l'i' 5 6 7 Oxygen cc per liter 10 11 12 Figure 1. Rawson's nomagram of oxygen saturation values at different tempera- tures and altitudes. Hold ruler or dark-colored thread to join an observed tem- perature on the upper scale with the observed dissolved-oxygen value on the lower scale. The values or units desired are read at points where the thread or ruler crosses the other scale. The associated table supplies correction values for oxygen saturation at various altitudes. For example, if 6.4 ppm of oxygen is observed in a sample having an altitude of approximately 500 m (l,640 feet), the amount of oxygen that would be present at sea level under the same cir- cumstances is found by multiplying 6.4 by the factor 1.06, giving the product 6.8; then the percentage saturation is determined by connecting 6.8 on the lower scale with the observed temperature on top scale and noting point of intersection on the middle (diagonal) scale. OXYGEN Oxygen is the second-most abundant gas in water (nitrogen is the first) and by far the most important — fish cannot live without it. Concentrations of oxygen, like those of other gases, typically are expressed either as parts per million by weight, or as percent of saturation. In the latter case, satura- tion refers to the amount of a gas dissolved when the water and atmos- pheric phases are in equilibrium. This equilibrium amount (for any gas) f) FISH HATCHERY MANAGEMENT decreases — that is, less oxygen can be dissolved in water — at higher alti- tudes and, more importantly, at higher temperatures. For this reason, the relationship between absolute concentrations (parts per million) and rela- tive concentrations (percent saturation) of gases is not straightforward. Special conversion formulae are needed; in graphical form these can be depicted as nomograms. A nomogram for oxygen is shown in Figure 1. Dissolved oxygen concentrations in hatchery waters are depleted in several ways, but chiefly by respiration of fish and other organisms and by chemical reactions with organic matter (feces, waste feed, decaying plant and animal remains, et cetera). As temperature increases the metabolic rate of the fish, respiration depletes the oxygen concentration of the water more rapidly, and stress or even death can follow. Fluctuating water tempera- tures and the resulting change in available oxygen must be considered in good hatchery management. In ponds, oxygen can be restored during the day by photosynthesis and at any time by wind mixing of the air and water. In hatchery troughs and raceways, oxygen is supplied by continu- ously flowing fresh water. However, oxygen deficiencies can arise in both ponds and raceways, especially when water is reused or reconditioned. Then, chemical or mechanical aeration techniques must be applied by cul- turists; these are outlined below for raceways, and on pages 108-110 for ponds. Aeration devices are shown in Figures 2 and 3. In general, water flowing into hatcheries should be at or near IOO"'!i oxy- gen saturation. In raceway systems, where large numbers of fish are cul- tured intensively, oxygen contents of the water should not drop below 80% saturation. In ponds, where fish densities are lower (extensive culture) than Figure 2. A simple aeration device made of perforated aluminum can add oxy- gen to the water and restrict fish from jumping into the raceway above. (FWS photo.) HATCHERY REQUIREMENTS 7 Figure 3. Electric powered aerators midway in a series of raceways can provide up to 2 ppm more oxygen for increased fish production. This type aerator is operated by a 1 horsepower motor and sprays approximately 1 cubic foot per second of water. Note the bulk storage bins for fish food in the center back- ground. (Courtesy California Department of Fish and Game.) in raceways, lower concentrations can be tolerated for short periods. How- ever, if either raceway or pond fish are subjected to extended oxygen con- centrations below 5 parts per million, growth and survival usually will be reduced (Figure 4). The lowest safe level for trout is approximately 5 parts per million. Reduced food consumption by fingerling coho salmon occurs at oxygen 8 FISH HATCHERY MANA(;KMKNT o >- X o o CO Op SMALL FISH SURVIVE SHORT EXPOSURE 0.3 1.0 2.0 3.0 4.0 5.0 LETHAL IF EXPOSURE PROLONGED FISH SURVIVE, BUT GROWTH SLOW FOR PROLONGED EXPOSURE DESIRABLE RANGE Figure 4. Effects of dissolved oxygen on warm water pond fish. Milligrams/liter = parts per million. (Source: Swingle 1969.) concentrations near 4-5 parts per million, and these fish will die if it drops below 3 parts per million. Walleye fry do not survive well in water contain- ing 3 parts per million dissolved oxygen or less. Low levels of dissolved oxygen below 5 parts per million can cause deformities of striped bass dur- ing embryonic development. NITROGEN Molecular nitrogen (N;) may be fixed by some aquatic bacteria and algae, but it is biologically inert as far as fish are concerned. Dissolved nitrogen may be ignored in fish culture so long as it remains at 100% saturation or below. However, at supersaturation levels as low as 102"^ it can induce gas bubble disease in fish. HATCHKR^ REQUIREMENTS 9 Theoretically, gas bubble disease can be caused by any supersaturated gas, but in practice the problem is almost always due to excess nitrogen. When water is supersaturated with gas, fish blood tends to become so as well. Because oxygen is used for respiration, and carbon dioxide enters into the physiology of blood and cells, excess amounts of these gases in the water are taken out of solution in the fish body. However, nitrogen, being inert, stays supersaturated in the blood. Any reduction in pressure on the gas, or localized increase in body temperature, can bring such nitrogen out of solution to form bubbles; the process is analogous to "bends" in human divers. Such bubbles (emboli) can lodge in blood vessels and restrict respiratory circulation, leading to death by asphyxiation. In some cases, fish may develop obvious bubbles in the gills, between fin rays, or under the skin, and the pressure of nitrogen bubbles may cause eyes to bulge from their sockets. Gas supersaturation can occur when air is introduced into water under high pressure which is subsequently lowered, or when water is heated. Wa- ter that has plunged over waterfalls or dams, water drawn from deep wells, or water heated from snow melt is potentially supersaturated. Air sucked in by a water pump can supersaturate a water system. All fish — coldwater or warmwater, freshwater or marine species — are sus- ceptible to gas bubble disease. Threshold tolerances to nitrogen supersat- uration vary among species, but any saturation over 100"" poses a threat to fish, and any levels over 110"n call for remedial action in a hatchery. Nitro- gen gas concentrations in excess of 105% cannot be tolerated by trout fingerlings for more than 5 days, whereas goldfish are unaffected by con- centrations of nitrogen as high as 120% for as long as 48 hours and 105% for 5 days. Whenever possible, chronically supersaturated water should be avoided as a hatchery source. CARBON DIOXIDE All waters contain some dissolved carbon dioxide. Generally, waters sup- porting good fish populations have less than 5.0 parts per million carbon dioxide. Spring and well water, which frequently are deficient in oxygen, often have a high carbon dioxide content. Both conditions easily can be corrected with efficient aerating devices. Carbon dioxide in excess of 20 parts per million may be harmful to fish. If the dissolved oxygen content drops to 3-5 parts per million, lower car- bon dioxide concentrations may be detrimental. It is doubtful that freshwa- ter fishes can live throughout the year in an average carbon dioxide con- tent as high as 12 parts per million. A wide tolerance range of carbon dioxide has been reported for various species and developmental stages of fish. Chum salmon eggs are relatively 10 MSH HAICHKRY MANAGEMENT resistant to high levels of carbon dioxide but 50'^ mortality can occur when carbon dioxide concentrations reach 90 parts per million. However, concentrations of 40 ppm carbon dioxide have little affect upon juvenile coho salmon. TOXIC GASES Hydrogen sulfide (H^S) and hydrogen cyanide (HCN) in very low concen- trations can kill fish. Hydrogen sulfide derives mainly from anaerobic decomposition of sulfur compounds in sediments; a few parts per billion are lethal. Hydrogen cyanide is a contaminant from several industrial processes, and is toxic at concentrations of 0.1 part per million or less. DISSOLVED GAS CRITERIA As implied above, various fish species have differing tolerances to dissolved gases. However, the following general guidelines summarize water quality features that will support good growth and survival of most or all fish species: Oxygen 5 parts per million or greater Nitrogen 100% saturation or less Carbon dioxide 10 parts per million or less Hydrogen sulfide 0.1 part per billion or less Hydrogen cyanide 10 parts per billion or less In general, oxygen concentrations should be near 100"ii saturation in the incoming water supply to a hatchery. A continual concentration of 80"ii or more of saturation provides a desirable oxygen supply. Suspended and Dissolved Solids "Solids" in water leave tangible residues when the water is filtered (suspended solids) or evaporated to dryness (dissolved solids) Suspended solids make water cloudy or opaque; they include chemical precipitates, flocculated organic matter, living and dead planktonic organisms, and sedi- ment stirred up from the bottom on a pond, stream, or raceway. Dissolved solids may color the water, but leave it clear and transparent; they include anything in true solution. SUSPENDED SOLIDS "Turbidity" is the term associated with the presence of suspended solids. Analytically, turbidity refers to the penetration of light through water (the HATCHERY REQUIREMENTS 11 lesser the penetration, the greater the turbidity), but the word is used less formally to imply concentration (weight of solids per weight of water). Turbidities in excess of 100,000 parts per million do not affect fish directly and most natural waters have far lower concentrations than this. However, abundant suspended particles can make it more difficult for fish to find food or avoid predation. To the extent they settle out, such solids can smother fish eggs and the bottom organisms that fish may need for food. Turbid waters can clog hatchery pumps, filters, and pipelines. In general, turbidities less than 2,000 parts per million are acceptable for fish culture. ACIDITY Acidity refers to the ability of dissolved chemicals to "donate" hydrogen ions (H^). The standard measure of acidity is pH, the negative logarithm of hydrogen-ion activity. The pH scale ranges from 1 to 14; the lower the number, the greater the acidity. A pH value of 7 is neutral; that is, there are as many donors of hydrogen ions as acceptors in solution. Ninety percent of natural waters have pH values in the range 6.7—8.2, and fish should not be cultured outside the range of 6.5-9.0. Many fish can live in waters of more extreme pH, even for extended periods, but at the cost of reduced growth and reproduction. Fish have less tolerance of pH extremes at higher temperatures. Ammonia toxicity becomes an important consideration at high pH (Chapter 2). Even within the relatively narrow range of pH 6.5-9.0, fish species vary in their optimum pH for growth. Generally, those species that live natural- ly in cold or cool waters of low primary productivity (low algal photosyn- thesis) do better at pH 6.5-9. Trout are an example; excessive mortality can occur at pH above 9.0. The affected fish rapidly spin near the surface of the water and attempt to leave the water. Whitening of the eyes and complete blindness, as well as fraying of the fins and gills with the frayed portions turning white, also occur. Death usually follows in a few hours. Fish of warmer climates, where intense summer photosynthesis can raise pH to nearly 10 each day, do better at pH 7.5-9. Striped bass and catfish are typical of this group. ALKALINITY AND HARDNESS Alkalinity and hardness imply similar things about water quality, but they represent different types of measurements. Alkalinity refers to an ability to accept hydrogen ions (or to neutralize acid) and is a direct counterpart of acidity. The anion (negatively charged) bases involved mainly are car- bonate (CO3 ) and bicarbonate (HCO3 ) ions; alkalinity refers to these 12 FISH HATCHERY MANAGEMENT alone (or these plus OH ) and is expressed in terms of equivalent concen- trations of calcium carbonate (CaCO^). Hardness represents the concentration of calcium (Ca^^) and magnesium (Mg"^"^) cations, also expressed as the CaCOi-equivalent concentration. The same carbonate rocks that ultimately are responsible for most of the alkalinity in water are the main sources of calcium and magnesium as well, so values of alkalinity and hardness often are quite similar when all are expressed as CaCO^ equivalents. Fish grow well over a wide range of alkalinities and hardness, but values of 120-400 parts per million are optimum. At very low alkalinities, water loses its ability to buffer against changes in acidity, and pH may fluctuate quickly and widely to the detriment of fish. Fish also are more sensitive to some toxic pollutants at low alkalinity. TOTAL DISSOLVED SOLIDS "Dissolved solids" and "salinity" sometimes are used interchangeably, but incorrectly. The total dissolved solids in water are represented by the weight of residue left when a water sample has been evaporated to dryness, the sample having already been filtered to remove suspended solids. This value is not the same as salinity, which is the concentration of only certain cations and anions in water. The actual amount of dissolved solids is not particularly important for most fish within the ranges of 10-1,000 parts per million for freshwater species, 1-30 parts per thousand for brackish-water species, and 30-40 parts per thousand for marine fish. Several species can live at concentra- tions well beyond those of their usual habitats; rainbow trout can tolerate 30, and channel catfish at least II, parts per thousand dissolved solids. However, rapid changes in concentration are stressful to fish. The blood of fish is either more dilute (marine) or more concentrated (fresh water) than the medium in which they live, and fish must do continual physiological work to maintain their body chemistries in the face of these osmotic differ- ences. Hatchery water supplies should be as consistent in their dissolved solid contents as possible. TOXIC MATERIALS Various substances toxic to fish occur widely in water supplies as a result of industrial and agricultural pollution. Chief among these are heavy met- als and pesticides. HATCHERY RE(^LTREMENTS 13 Heavy Metals There is a wide range of reported values for the toxicity of heavy metals to fish. Concentrations that will kill 50"o of various species of fish in 96 hours range from 90 to 40,900 parts per billion (ppb) for zinc, 46 to 10,000 ppb for copper, and 470 to 9,000 ppb for cadmium. Generally, trout and salmon are more susceptible to heavy metals than most other fishes; minute amounts of zinc leached from galvanized hatchery pipes can cause heavy losses among trout fry, for example. Heavy metals such as copper, lead, zinc, cadmium and mercury should be avoided in fish hatchery water supplies, as should galvanized steel, copper, and brass fittings in water pipe, especially in hatcheries served by poorly buffered water. Salinity All salts in a solution change the physical and chemical nature of water and exert osmotic pressure. Some have physiological or toxic effects as well. In both marine and freshwater fishes, adaptations to salinity are necessary. Marine fishes tend to lose water to the environment by diffusion out of their bodies. Consequently, they actively drink water and get rid of the excess salt by way of special salt-excreting cells. Freshwater fishes take in water and very actively excrete large amounts of water in the form of urine from the kidneys. Salinity and dissolved solids are made up mainly of carbonates, bicar- bonates, chlorides, sulphates, phosphates, and possibly nitrates of calcium, magnesium, sodium, and potassium, with traces of iron, manganese and other substances. Saline seepage lakes and many impounded waters situated in arid regions with low precipitation and high rates of evaporation have dissolved solids in the range of 5,000-12,000 parts per million. Fish production in saline waters is limited to a considerable extent by the threshold of toler- ance to the naturally occurring salt. Rainbow trout, as an example, gen- erally tolerate up to 7,000 parts per million total dissolved solids. Survival, growth and food efficiency were excellent for rainbow trout reared in brackish water at an average temperature of 56°F. The trout were con- verted from fresh water to 30 parts per thousand over a 9-day period and were reared to market size at this salinity. Mineral deficiencies in the water may cause excessive mortality, particu- larly among newly hatched fry. Chemical enrichment of water with calcium chloride has been used to inhibit white spot disease in fry. Brook trout can absorb calcium, cobalt, and phosphorous ions directly from the water. 14 FISH HAICHKRY MANAGEMENT ABl.F. 1. SUGGESTED WATER qUAl-ITY CRITERIA lOR OI'IIMIJM HEAl.IH OK SAL- MONIl) FISHES. CONCENl'RAIIONS ARE IN PARIS I'ER Mil. I. ION (PPM). (SOURCE: WEDEMEYKR 1!)77.) CHEMICAL UPPER LIMITS FOR CONTINUOUS EXPOSURE Ammonia (NH3) Cadmium Cadmium Chlorine Copper Hydrogen sulfide Lead Mercury (organic or inorganic) Nitrogen Nitrite (NO2") Ozone Polychlorinated biphenyls (PCB's) Total suspended and settleable solids Zinc 0.0125 ppm (un-ionized form) 0.0004 ppm (in soft water < 100 ppm alkalinity) 0.003 ppm (in hard water > 100 ppm alkalinity) 0.0;-i ppm ().00() ppm in soft water 0.002 ppm 0.03 ppm 0.002 ppm maximum, O.OOOO.'i ppm average Maximum total gas pressure 1 10"n of saturation 0.1 ppm in soft water, 0.2 ppm in hard water (0.03 and 0.06 ppm nitrite-nitrogen) (LOO.""! ppm 0.002 ppm 80 ppm or less 0.03 ppm To protect salmonid eggs and fry. For non-salmonids, 0.004 ppm is acceptable. To protect salmonid eggs and fry. For non-salmonids, 0.03 ppm is acceptable. '^Copper at O.OO.") ppm may supress gill adenosine triphosphatase and compromise smoltifica- tion in anadromous salmonids. Walleye fry hatched in artesian well water containing high levels of cal- cium and magnesium salts with a dissolved solid content of 1,563 parts per million were twice the size of hatchery fry held in relatively soft spring fed water. This rapid growth was attributed to the absorption of dissolved solids. Channel catfish and blue catfish have been found in water with salinities up to 11.4 parts per thousand. Determination of salinity tolerance in catfish is of interest because of possible commercial production of these species in brackish water. Turbidity Clay turbidity in natural waters rarely exceeds 20,000 parts per million. Waters considered "muddy" usually contain less than 2,000 parts per mil- lion. Turbidity seldom directly affects fish, but may adversely affect pro- duction by smothering fish eggs and destroying benthic organisms in HATCHERY REQUIREMENTS 15 Table 2. suggested chemical values for hatchery water supplies, concen- tration ARE IN PARTS PER MILLION (PPM). (SOURCE: HOWARD N. LARSEN, UNPUB- LISHED.) VARL\BLK TROUT \V.\RM V\ A IKR Dissolved oxygen 5-saturation 5-saturation Carbon dioxide 0-10 0-15 Total alkalinity (as CaC03) 10-400 50-400 % as phenolphthalein 0-25 0.40 % as methyl orange 75-100 60-100 % as ppm hydroxide 0 0 % as ppm carbonate 0-25 0-40 "(1 as ppm bicarbonate 75-100 75- 100 PH 6.5-8.0 6.5-9.0 Total hardness (as CaC03) 10-400 50-400 Calcium 4-160 10-160 Magnesium Needed for buffer system Manganese 0-0.01 0-0.01 Iron (total) 0 0.15 0-0.5 Ferrous ion 0 0 Ferric ion 0.5 0-0.5 Phosphorous 0.01-3.0 0.01-3.0 Nitrate 0-3.0 0-3.0 Zinc 0-0.05 same Hydrogen sulfide 0 0 ponds. It also restricts light penetration, thereby limiting photosynthesis and the production of desirable plankton in earthen ponds. Pesticides Many pesticides are extremely toxic to fish in the low parts- per- billion range. Acute toxicity values for many commonly used insecticides range from 5 to 100 microgram/liter. Much lower concentrations may be toxic upon extended exposure. Even if adult fish are not killed outright, long- term damage to fish populations may occur in environments contaminated with pesticides. The abundance of food organisms may decrease, fry and eggs may die, and growth rates of fish may decline. Pesticides sprayed onto fields may drift over considerable areas, and reach ponds and streams. If watersheds receive heavy applications of pesticides, ponds usually are not suitable for fish production. Suggested water quality criteria for salmonid and warmwater fishes are presented in Tables 1 and 2. 16 FISH HATCHERY MANAGEMENT Water Supply and Treatment An adequate supply of high quality water is critical for hatchery opera- tions. Whether fish are to be cultured intensively, requiring constant water flow, or extensively, requiring large volumes of pond water, the water supply must be abundant during all seasons and from year to year. Even hatcheries designed to reuse water need substantial amounts of "make-up" flow. Among other criteria, hatchery site selection should be based on a thorough knowledge of local and regional hydrology, geology, weather, and climate. Groundwater generally is the best water source for hatcheries, particu- larly for intensive culture. Its flow is reliable, its temperature is stable, and it is relatively free of pollutants and diseases. Springs and artesian wells are the cheapest means of obtaining groundwater; pumped wells are much less economical. Spring-fed streams with a small watershed can give good water supplies. They carry little silt and are not likely to flood. The springs will ensure a fairly steady flow, but there still will be some seasonal changes in water temperature and discharge; storage and control structures may have to be built. It is important that such streams not have resident fish populations, so that disease problems can be avoided in the hatchery. Larger streams, lakes, and reservoirs can be used for fish culture, but these vary considerably in water quality and temperature through the year, and may be polluted. They all have resident fish, which could transmit disease to hatchery stocks. Even though the water supply may be abundant and of high quality, most hatcheries require some type of water treatment. This may be as sim- ple as adjusting temperatures or as involved as treating sewage. Excluding management of pondwater quality, discussed in Chapter 2, and medication of diseased fish (Chapter 5), water may have to be treated at three points as it passes through a hatchery system: as it enters; when it is reused; and as it leaves. Treatment of Incoming Water Water reaching a hatchery may be of the wrong temperature for the fish being cultured, it may have too little oxygen or too many suspended solids, and it may carry disease pathogens. These problems often are seasonal in nature, but sometimes are chronic. TEMPERATURE CONTROL The control of water temperature is practical when the amount of water to be heated or cooled is minimal and the cost can be justified. Temperature HATCHERY REQUIREMENTS 17 control generally is considered in recycle systems with supplemental make- up water or with egg incubation systems where small quantities of water are required. A number of heat exchange systems are available commer- cially for heating or chilling water. AERATION Water from springs and wells may carry noxious gases and be deficient in oxygen; lake and river sources also may have low dissolved oxygen con- tents. Toxic gases can be voided and oxygen regained if the water is mechanically agitated or run over a series of baffles. STERILIZATION Any water that has contained wild fish should be sterilized before it reaches hatchery stocks. Pathogens may be killed by chemical oxidants or by a combination of sand filtration (Figure 5) and ultraviolet radiation. BACKWASH TROUGHS BACKWASH OUTFLOW FILTER TANK COLLECTION MAIN FOR CLEAN WATER DISCHARGE AND BACKWASH INFLOW Figure 5. Diagram of a sand filter. The water supply is clarified as it flows down through the sand and gravel bed, and is then collected in the perforated lateral pipes and discharged from the filter. The filter is backwashed to clean it by pumping water up through the gravel and sand; the collected waste material is washed out the backwash outflow. 18 FISH HATCHERY MANAGEMENT Figure 6. Micro-screen filters consist of a rotating drum covered with woven fabric of steel or synthetic material with various size openings. The raw water enters the center of the drum and passes through the fabric as filtered water. As the fabric becomes clogged, the drum rotates and a high- pressure water spray (arrow) removes the filtered material from the screen into a waste trough. Micro-screen fabric is available with openings as small as 5 microns. (FWS photo.) Filtration followed by ultraviolet radiation is a proven method for steri- lizing hatchery water. For example, 125 gallons per minute of river water containing large numbers of fish pathogens can be sterilized by passage through two 30-inch diameter sand filters, then through an 18-lamp ultra- violet radiation unit. The sand filter removes particles as small as 8-15 microns and the ultraviolet radiation kills organisms smaller than 15 microns. It is important that pathogens be exposed to an adequate amount of ultraviolet intensity for the required effective contact time. Treated water must be clear to permit efficient ultraviolet light penetration. Maintenance of sand filters includes frequent backflushing and ultra- violet equipment requires periodic cleaning of the quartz glass shields and lamp replacement. Commercially available microscreen filters can be used as an alternative to sand filters (Figure 6). Chlorine gas or hypochlorite can be used as sterilants, but they are toxic to fish and must be neutralized. Ozone is a more powerful oxidizing agent HATCHERY REQUIREMENTS 19 than hypochlorite, and has been used experimentally with some success. It is unstable and has to be produced on site (from oxygen, with electrical or ultraviolet energy). Ozonated water must be reaerated before fish can live in it. Although very effective against microorganisms, ozone is extremely corrosive and can be a human health hazard. Treatment of Water for Reuse Often it is feasible to reuse water in a hatchery; some operations run the same water through a series of raceways or ponds as many as ten times. Any of several reasons can make it worthwhile to bear the added cost of reconditioning the water. The quantity of source water may be low; the cost of pollution control of hatchery effluent may be high. The price of en- ergy to continuously heat large volumes of fresh source water may limit production of fish; continuous quality control and sterilization may be expensive. A hatchery that uses water only once through the facility is called a "single- pass" system. Hatcheries that recycle water for additional passes by pumping and reconditioning it are termed "reuse-reconditioning" systems. In either system, water that passes through two or more rearing units is termed "reused." Most practical water-reconditioning systems recycle 90-95% of the water, the supplement of make-up water coming from the source supply. To be practical, the system must operate for long periods without problems and carry out several important functions (Figure 7). As water passes through or within a hatchery, fish remove oxygen, give off carbon dioxide, urea, and ammonia, and deposit feces. Uneaten food accumulates and water temperatures may change. This decline in water quality will lower growth and increase mortality of fish if the water is recy- cled but not purified. A water-reconditioning system must restore original temperatures and oxygen concentrations, filter out suspended solids, and remove accumulated carbon dioxide and ammonia. Urea is not a problem for fish at the concentrations encountered in hatcheries. Temperatures are controlled, and suspended solids filtered, in ways out- lined above for incoming water. Oxygen is added and excess carbon diox- ide removed by mechanical aeration. The removal of ammonia is more involved, and represents one of the major costs of recycling systems. The advantage of manipulating rearing environments in a recycle system has been demonstrated in the rearing of striped bass fry and fingerlings. They have been reared to fingerling size with increased success when the salinity of the recycled water was raised to 47 parts per thousand during the rearing period. Channel catfish also have been successfully reared in recycled-water systems. 20 FISH HATCHERY MANAGEMENT WATER SUPPLY (INPUT) FILTER STERILIZE HEAT OR COOL HATCHERY REARING PONDS REMOVE WASTE SOLIDS REMOVE AMMONIA REMOVE CARBON DIOXIDE ADD OXYGEN (AERATION) TEMPERATURE CONTROL pH CONTROL WASTE SOLIDS DISPOSAL BOD REDUCTION WASTE WATER (EFFLUENT) RECONDITIONED WA ER Figure 7. Schematic diagram of a fish hatchery water reuse system. (Modified from Larmoyeux 1972.) AMMONIA TOXICITY When ammonia gas dissolves in water, some of it reacts with the water to produce ammonium ions, the remainder is present as un-ionized ammonia (NH .). Standard analytical methods' do not distinguish the two forms, and The books by Claude E. Boyd and the American Pubhc Health Association et al., listed in the references, give comprehensive procedures for analyzing water quality. HATCHERY REQUIREMENTS 21 both are lumped as "total ammonia." Figure 8 shows the reaction that occurs when ammonia is excreted into water by fish. The fraction of total ammonia that is toxic ammonia (NH J varies with salinity oxygen concen- tration and temperature, but is determined primarily by the pH of the solution. For example, an increase of one pH unit from 8.0 to 9.0 increases the amount of un-ionized ammonia approximately 10-fold. These propor- tions have been calculated for a range of temperatures and pH and are given in Appendix B. Note that the amount of NH^ increases as tempera- ture and pH increase. From Appendix B and a measurement of total ammonia (parts per million: ppm), pH, and temperature, the concentration of un-ionized ammonia can be determined: Ppm un-ionized ammonia=(ppm total ammonia x percent un-ionized ammonia) ^ 100. When un-ionized ammonia levels exceed 0.0125 part per million, a decline in trout quality may be evidenced by reduction in growth rate and damage to gill, kidney, and liver tissues. Reduced growth and gill damage occur in channel catfish exposed to 0.12 part per million or greater un- ionized ammonia. Ammonia rapidly limits fish production in a water-recycling system un- less it is removed efficiently. Biological filtration and ion exchange are the best current means of removing ammonia from large volumes of hatchery water. BIOLOGICAL REMOVAL OF AMMONIA Biological removal of ammonia is accomplished with cultures of nitrifying bacteria that convert ammonia to harmless nitrate ions (NOj"). These bac- teria, chiefly species of Nitrosomonas and Nitrobacter can be grown on almost any coarse medium, such as rocks or plastic chips. The best culture mate rial contains calcium carbonate, which contributes to the chemical reac- tions and buffers pH changes; oyster shells often are used for this purpose. By the time water reaches the biological filter, it should be already well- aerated (oxygen is needed for the process) and free of particulate matter FISH "-NHg + HO " Z^ NH^OH." „ NH^^ OH \ UNIONIZED pH IONIZED TOXIC FORM DEPENDENT NONTOXIC FORM Figure 8. Reaction of ammonia excreted into water by fish. 22 FISH HATCHERY MANAGEMENT (which could clog the filter). It is important that the water be pathogen- free, because an antibiotic or other drug that has to be used in the hatchery can kill the nitrifying bacteria as well. Settling chambers and clarifiers can extend the life of biofilters and reduce clogging by removing particulate matter. Filter bed material with large void spaces also can reduce clogging, and foam fractionation will remove dissolved organic substances that accumulate. These foaming devices are also called "protein skimmers," which refers to their ability to remove dissolved organic substances from the water. The foam is wasted through the top of the device and carries with it the organic material. In a small system, air stones can be used to create the foam. The air produces numerous small bubbles that col- lect the organic material onto their surface. Because foam fractionation does not readily remove all particulate organic material, it should follow the set- tling or clarifying unit in a reconditioning system. Nitrite (NO7 ) is an intermediate product of nitrification, and a poorly operating biofilter may release dangerous amounts of this toxic ion to the water. A more rapid growth rate of Nitrosomonas in the biological system can lead to accumulation of nitrite, which is highly toxic to freshwater fishes. Nitrite oxidizes blood hemoglobin to methemoglobin, a form which is incapable of carrying oxygen to the tissues. Methemoglobin is chocolate-brown in color, and can be easily seen in the fish's gills. Yearling trout are stressed by 0.15 part per million and killed by 0.55 part per million nitrite. Channel catfish are more resistant to nitrite, but 29 parts per million can kill up to 50'!'() of them in 48 hours. Nitrite toxicity decreases slightly as the hardness and chloride content of water increases. ION EXCHANGE REMOVAL OF AMMONIA Ion exchange for removal of ammonia from hatchery water can be accom- plished by passing the water through a column of natural zeolite. Zeolites are a class of silicate minerals that have ion exchange capacities (they are used in home water softeners). Among these, clinoptilolite has a partic- ularly good affinity for ammonium ions. It is increasingly being used in hatcheries, where it effects 90 97"o reductions in ammonia (Figure 9). Clinoptilolite does not adsorb nitrate or nitrite, nor does it affect water hardness appreciably. It can be regenerated by passing a salt solution through the bed. The ammonia is released from the salt solution as a gas and the solution can be reused. Any ion exchange unit can develop into a biofilter if nitrifying bacteria become established in it. This may lower exchange efficiencies and cause production of nitrite, so periodic disinfec- tion may be necessary. HATCHERY REQUIREMENTS 23 WASTE WATER SOLIDS REMOVAL CLINOPTILOLITE BED T AERATION BRINE I BRINE REGENERANT RECOVERY AMMONIA RECONDITIONED WATER Figure 9. Schematic diagram of ion exchange removal of ammonia from hatchery waste water. OTHER AMMONIA REMOVAL TECHNIQUES Several procedures for removing ammonia from hatchery water have been tried. Many of them work, but are impractical in most circumstances. When the pH of water is raised to 10 or 11 with calcium or sodium hy- droxide, most of the ammonia goes to the gaseous form (NH^) and will dis- sipate to the air if the water is sprayed in small droplets. This "ammonia stripping" does not work well in cold weather, and the water has to be reacidified to normal pH levels. Chlorine or sodium hypochlorite added to water can oxidize 95-99% of the ammonia to nitrogen gas (Figure lO). "Breakpoint chlorination" creates hydrochloric acid as a byproduct, which must be neutralized with lime or caustic soda, and residual chlorine must be removed as well. This is an uneconomical process, although future technological advances may improve 24 FISH HATCHERY MANAGEMENT CHLORINE WASTE WATER SOLIDS REMOVAL " BREAKPOINT CHLORINATION 1 ' ACTIVATED CAR ADSOF BUIN iPTlON WASTE SLUDGE NITROGEN GAS CHLORAMINES, EXCESS CHLORINE AND DISSOLVED ORGANICS AERATION RECONDITIONED WATER Figure 10. Schematic diagram of breakpoint chlorination remov- al of ammonia from hatchery waste water. its practicality in hatcheries. An advantage of this system is that all treated v^ater is sterilized. Oxidation ponds or lagoons can remove 35-85% of the ammonia in v^astewater through microbial denitrification in the pond bottom and through uptake by algae. This method requires considerable land area and extended retention time of the wastewater in the lagoon. Oxidation lagoons work best in southern chmates. Cold weather significantly reduces biological activity. ESTIMATION OF AMMONIA Because of the importance of ammonia to fish production total ammonia in hatchery water should be measured directly on a regular basis. However, rough estimates of total ammonia can be made from an empirical formula, if necessary. Although ammonia can be contributed by source water and by HATCHERY REQUIREMENTS 25 microbial breakdown of waste feed, most of it comes from fish metabolism. The amount of metabolism, hence the amount of ammonia excreted, is conditioned by the amount of food fish eat. For each hatchery and feed type, an ammonia factor can be calculated: ppm total ammonia x ,^pm water inflow ammonia factor = — - — , . , ; lbs food ted per day Here, ppm is parts per million concentration, gpm is gallons per minute flow, and lbs is pounds. To establish the ammonia factor, total ammonia should be measured in raceways, tanks, and ponds several times over one day. Once the factor is established, the formula can be turned around to give estimates of total ammonia: lbs food/day x ammonia factor ppm total ammonia = ~ gpm flow Then, by reference to Appendix B with the appropriate temperature and pH, the concentration of un-ionized ammonia can be estimated. Example: Three raceways in a series have a water flow of 200 gallons per minute. Fish in the first raceway receive 10 pounds of food per day, 5 pounds of feed per day go into the second raceway, and 20 pounds of feed per day go into the third. The ammonia factor for these raceways is 3.0. In the absence of any water treatment, what is the expected concentration of total ammonia nitrogen at the bottom of each raceway? Raceway 1: = 0.15 ppm ^ 200 ^ (10+5)X3 ^^„ Raceway 2: = 0.23 ppm ^ 200 ^ _ (10 + 5 + 20) X 3 Raceway 3: = 0.53 ppm ^ 200 ^ Treatment of Effluent Water and Sludge The potential of hatchery effluent for polluting streams is very great. Like any other source of waste water, hatcheries are subject to federal, state, and local regulations regarding pollution. The United States Environmental Protection Agency requires permits of hatcheries that discharge effluent into navigable streams or their tributaries. Hatchery operators are responsi- ble for knowing the regulations that apply to their facilities. Some treat- ment of hatchery effluent is required of almost every hatchery. This is true even for systems that recycle and treat water internally; their advantage 26 KlSll HATCHERY MANAGEMKNT lies in the greatly reduced volume of effluent to be treated compared with single-pass hatcheries. HATCHERY POLLUTANTS Generally, three types of pollutants are discharged from hatcheries: (l) pathogenic bacteria and parasites; (2) chemicals and drugs used for disease control; (3) metabolic products (ammonia, feces) and waste food. Pollution by the first two categories is sporatic but nonetheless important. If it occurs, water must be sterilized of pathogens, disinfected of parasites, and detoxified of chemicals. Effluent water can be sterilized in ways outlined for source water (page 17). Drug and chemical detoxification should follow manufacturers' instructions or the advice of qualified chemists and patholo- gists. Standby detoxification procedures should be in place before the drug or chemical is used. The third category of pollutants — waste products from fish and food — is a constant feature of hatchery operation, and usually requires permanent facilities to deal with it. Two components — dissolved and suspended solids — need consideration. Dissolved pollutants predominantly are ammonia, nitrate, phosphate, and organic matter. Ammonia in the molecular form is toxic, as already noted. Nitrate, phosphate, and organic matter contribute to eutrophication of receiving waters. For the trout and salmon operations that have been stud- ied, each pound of dry pelleted food eaten by fish yields 0.032 pound of total ammonia, 0.087 pound of nitrate, and 0.005 pound of phosphate to the effluent (dissolved organic matter was not determined separately). The feed also contributes to Biological Oxygen Demand (BOD), commonly used as an index of pollution; it is the weight of dissolved oxygen taken up by organic matter in the water. More serious are the suspended solids. These can, as they settle out, completely coat the bottom of receiving streams. Predominantly organic, they also reduce the oxygen contents of receiving waters either through their direct oxidation or through respiration of the large microbial popula- tions that use them as culture media. For the trout and salmon hatcheries mentioned above, each pound of dry feed results in 0.3 pound of settleable solids — that part of the total suspended solids that settle out of the water in one hour. Most of these materials have to be removed from the effluent before it is finally discharged. Typically, this is accomplished with settling basins of some type. It should be noted that except for ammonia, the pollutants listed can be augmented from other sources such as waste food and organic material in the incoming water. The fish culturist should not assume that the total pol- lutant concentrations in the effluent are derived only from food eaten by the fish. hatchery requirements 27 Table 3. pollutant levels in the effluent frcjm earthen catfish rearing ponds during fish seining and draining of the pond. (after boyd li»79.) I'ONI) USH POLLLTANl'' ORAIMNG SF.INING Settleable solids (ppm) O.OH 28. .1 Settleable oxygen demand (ppm) 4.31 28. i) Chemical oxygen demand (ppm) 30.2 342 Soluble orthophosphate (ppb as P) Hi .'J9 Total phosphorus (ppm as P) 0.11 0.49 Total ammonia (ppm as N) 0.98 2.34 Nitrate (ppm as N) O.Hi 0.14 Concentrations (parts per million or per billion) are on a weight basis except for settleable solids, which are on a volume basis. The levels of pollutant in a hatchery effluent can be determined with the following general equation: ,, pollutant factor X lbs food fed Average ppm pollutant = -. ^ water flow Igpmj The following pollutant factors should be used in the equation: Total ammonia 2.67 Nitrate 7.25 Phosphate 0.417 Settleable solids 25.0 BOD 28.3 Example: A trout hatchery in which fish are fed 450 pounds of food per day and which has a water flow of 1,500 gallons per minute has a total ammonia concentration of 0.8 parts per million in the hatchery effluent. . 2.67 X 450 ppm ammonia = -: = O.o ^^ 1500 Studies in warmwater fish culture have shown that there is no consistent relationship between the weight of fish harvested in earthen ponds and the amount of settleable solids discharged in the effluent. In general, an increase in fish weight results in an increase in settleable solids. Pollutant levels in the discharge from earthen ponds vary with the volume of water being discharged and the pond design. Some pollutant levels that have been reported in the effluent of catfish ponds are presented in Table 3. SEDIMENTATION BASINS The principle of sedimentation basins is to spread flowing hatchery effluent out in area, thus slowing it down, so that suspended solids will settle out of 28 KISH HATCHERY MANAGEMENT Q 100 FT ^ PERFORATED SCREEN TT^^. ^^ Q _i O C/3 CO 100 50 FT PROFILE OF SOLIDS SETTLING 85% 100 FT Figure 11. A characteristic settling profile for settleable waste solids is shown for a 30 ft X IGQ ft tank with a 4-ft water depth and a water velocity (V) of 0.056 ft/second. (Source: Jensen 1972.) their own weight under conditions of reduced water turbulence (Figure ll). The design of settling basins should take four interrelated factors into account: (l) retention time; (2) density of waste solids; (3) water velocity and flow distribution; (4) water depth. Retention time is the average period that a unit of water stays in the basin before it is swept out. Depending on the quantity of wastes carried by the water, retention time can be anywhere from 15 minutes to 2 hours. In general, retention time increases as the area and depth of the basin increase. If flow currents are not managed correctly, however, some of the water passes rapidly through even a larger structure while other water lingers in backwater areas; the average retention time may seem adequate, but much waste will still leave the basin. Therefore, it is important that flow be directed evenly through the structure, and a system of baffles may have to be incorporated in the design. If water is too shallow, it constantly scours the bottom, suspends wastes, and carries solids out to receiving waters. Conversely, if water is too deep, solids do not have time to settle from top to bottom before water leaves the basin. A water depth of 1^ feet is a practical compromise in most circumstances. HATCHERY REQUIREMENTS 29 Sedimentation basins can take several forms. One is a modified concrete raceway, called a linear clarifier (Figures 12, 13, and 14). Water entering a linear clarifier should do so through a screen — preferably through a series of two or more screens — at the head end of the unit. Such screens, which should be more than 50% open area, distribute flow and reduce turbulence much better than dam boards, which cause turbulence near them and a stronger surface than bottom flow. Perhaps the most common settling basins are outdoor earthen ponds or "lagoons." These can be of varying sizes and configurations. Obviously, the bigger the pond, the more effluent it can accommodate. Because of the amount of land settling ponds occupy, there usually are practical limita- tions on lagoon size. Several commercially produced settling systems incorporate baffles and settling tubes. These are quite efficient and require less space and retention time than either linear clarifiers or lagoons. However, they can be quite expensive. Figure 12. Effluent treatment system at the Jordan River National Fish Hatchery consists of two linear clarifiers (top), 30 ft x 100 ft with a water depth of 4 feet. The system will handle up to 600 gpm divided equally between the two bays. The bays are cleaned by drawing off the top water and moving the sludge with a garden tractor to collection channels. The sludge is then removed with a truck-mounted vacuum liquid manure spreader (bottom). (FWS photos.) 30 FISH HATCHERY MANAGEMENT Figure 13. Three linear clarifiers located at the Jones Hole National Fish Hatchery, 114 f t x 41 ft and 6 ft deep. Each unit has a sludge scraper system for sludge removal. These are long redwood boards attached by chain to move and deposit sludge into the sumps at the upper ends of the clarifiers. This system is designed to pump sludge to drying chambers. (FWS photo.) A warmwater fish rearing pond acts as its own settling basin. Except when the water level is so low that any water movement scours the bottom, draining a pond usually does not cause much waste escapement. However, during seining operations when the bottom is disturbed, levels of suspend- ed solids in the effluent can increase several hundred times. Special atten- tion should be given to discharges at such times. If water flow through the pond cannot be stopped until solids can resettle, the effluent may have to be filtered or diverted away from receiving streams. Likewise, pollutant loads from other hatchery operations can increase sharply at times. Periods of raceway cleaning are examples, and there should be means available to handle the added waste concentrations. Sometimes, raceways and tanks can be vacuumed before they are disturbed, although this is labor-intensive work (Figure 15). SOLID WASTE DISPOSAL Over half of the total nutrients produced by hatchery operations are in the form of settleable solids. They must be removed frequently from lagoons and clarifiers, because they rapidly decompose and would otherwise pollute the receiving waters with dissolved nutrients. The "solid" wastes from settling basins and various filtration units around a hatchery, being 90% water, can accumulate into large volumes that must be disposed of. Hatchery sludge has considerable value as a fer- tilizer. In warm climates and seasons, it can be spread directly on the HATCHERY REQUIREMENTS 31 ground; winter storage at northern hatcheries may be a problem, however. If transportation is available, or on-site mechanical separators and vacuum filters can be justified, the sludge can be reduced to moist cakes and sold to commercial fertilizer manufacturers; some municipal sewage plants dispose of sludge this way. Alternatively, if the hatchery is near an urban area, it may be possible to dispose of solid waste in the municipal system. Incineration of sludge is the least desirable means of disposal, as dewatering and drying the material is costly, and the process merely exchanges air pollution for water pollution. Figure 14. Sludge is collected from the linear clarifiers into storage lagoons at the Jones Hole National Fish Hatchery, Utah. The lagoons are periodically dewatered and the sludge dried for removal. 32 FISH HATCHERY MANAGEMENT Figure 15. (l) A vacuum liquid manure spreader with a modified hose connec- tion can be used to remove settleable waste solids from fish rearing units. (2) Water flow is controlled with a j-turn ball valve (arrow). The valve is shut off whenever the cleaning wand is not actually drawing up waste. Note the set- tling area provided at the lower end of the raceway. (3) The collected waste solids are then spread on agriculture lands or lawn areas away from residences. (FWS photos.) Hatchery Design In judging the suitability of a site for a fish hatchery, the primary purpose of the hatchery should be considered. If egg production is an important function, somewhat lower temperatures may be desirable than if the hatchery is to be used primarily for rearing fish to catchable size. Where no eggs are handled even higher water temperatures may be desirable to afford maximum fish growth. For efficient operation of a hatchery, the site should be below the water source. This will afford sufficient water head to provide aeration and ade- quate water pressure without pumping. Site considerations should also in- clude soil characteristics and land gradient. An impervious soil will hold water with little seepage. Land that is sloped provides drainage and allows the construction of raceways in a series for reuse of water by gravity flow. Possible pesticide contamination of the soil and the presence of adjacent land use that may cause agricultural or industrial contamination should be investigated. Flood protection is also essential. HATCHERY REQUIREMENTS 33 If earthen ponds are being considered, sandy or gravel soils should be avoided. Soils that compact well should be considered where concrete structures are proposed. Hatchery labor is an expensive item in rearing fish and good hatchery design, including use of mechanized equipment, can eliminate a large per- centage of the labor. Many items of equipment are available today that can dramatically reduce hand labor in the fish hatchery. Consideration should be given for automatic feeding, loading and unloading fish, transporting fish between fish rearing units and access to rearing units with vehicles and motorized equipment. As an example, raceways can be designed so that vehicles have access to all points in the facility. Raceways built in pairs provide a road- way on each side so that vehicle- drawn feeding equipment can be utilized. A suitable hatchery site should include sufficient land area for potential expansion of the facilities. Hatchery planners often overestimate the pro- duction capacity of the water supply and underestimate the facility requirements. Buildings The principal buildings of a fish hatchery include an office area for record- keeping, a hatchery building, garages to protect equipment and vehicles, a shop building to construct and repair equipment, crew facilities and a lab- oratory for examining fish and conducting water analyses. The hatchery building should include facilities for egg incubation and fry and fingerling rearing and tanks for holding warmwater pond- reared fish prior to shipment. Storage facilities must also be considered for feed, which may require refrigeration. Separate facilities should also be provided for chemical storage. A truck driveway through the center or along one side of building is convenient for loading and unloading fish. Primary con- sideration should be given to the design and location of buildings and storage areas to create a convenient and labor saving operation. Table 4 provides a summary of suggested standards for fish hatchery site selection and water requirements along with hatchery design criteria. 34 fish hatchery management Table 4. suggested standards for fish hatchery development, these standards will change as new construction materials and more effi- cient designs become available. hatchery symbol: t = trcjut and salmon (cold water); c = cool water; w = warm water HATCHERY ITEM SYMBOL CRIIERI.\ Land Area required Y C W Enough for facilities, protection of water su[j- ply, and future expansion; treatment ol effluent; future water reuse and recirculation systems. Topography V C W Sufficient elevation between water source and production facilities for aeration and gravity flow. Land should have gentle slopes or moderate relief that can be graded to pro- vide adequate drainage. Avoid areas subject to flooding. Water supply Source T C 1 he water supply should be considered in this order of preference: spring; well; stream; river; lake or reservoir. An underground water source should be investigated. W Lake or reservoir water preferred over creek or stream supply. Qj/aiility T C Water requirements are dictated by the size future of the unit planned. The supply should provide A changes per hour through each unit and no less than 1 change per hour through the entire system. Where water reconditioning is planned, require- ments should be adjusted to the capabilities of the system. Weirs or water meters should be installed to measure total inflow. Allow for future expansion. Prospective sources should undergo long-term chemical analysis and biological or live fish tests, with emphasis on periods of destratification when reservoir or lake supply is contemplated. Studies should include examination of watershed for potential sources of pollution including turbidity. Consider equipment to filter and sterilize water. W Dependent upon acreage involved and require- ments. Temperature T 45-f)5°F for fish, 4.')-,'J,')°F for eggs. Plan equip- ment to cool or heat water to temperature desired. C fi()~7()°F desirable for walleye and northern pike culture. W 70-8()°F preferred during growing season. IIAICHKin RKUriRKMF.NTS 35 Table 4. continued. ITEM HATCHERY SYMBOL CRI 1 KRIA Water supply [continued) Availability T Turbidity T Supply lines Siie T Type C c c earing facilities Type T C Size T C Floor slope T C Intake control T C W Gravity or artesian flow preferred. Clear. W Clear or only slightly turbid. Adequate to carry Ij times quantity of water required. Consider future hatchery expan- sion when sizing supply lines. W Main supply lines adequate to fill 1-acre pond in 2 days and all ponds in 14 days or less. W Cast iron, concrete, or steel, unless size or soil conditions make other materials desirable. Teflon, nylon, or other proven, durable inert substances are acceptable. Under no condi- tions should copper, brass, or zinc galvan- ized pipe be used. RacewaNS and circular pools. W Earthen ponds. Rectangular raceways: 8' x 80' x 30" or 6' X 60' X 18"; Burrows recirculation ponds: 17' X 7.5' X 3'; Swedish-type ponds: 3f)' X 36'; circular ponds: varying from 6 to 50 feet diameter, concrete or fiberglass con- struction. W Earthen ponds: 0.75 to 1.0 acre preferred; 1 to 4 acres allowable; 0.1 to 0.5 acre for special purposes. Minimum depth of 3 feet at shal- low end, (i feet at deep end for rearing ponds. Deeper ponds (10-12 feet) may be desirable in northern areas, and for channel catfish rearing regardless of climate. A 2:1 slope is standard with riprap on sides and 3:1 slope without riprap. Dyke tops should be 12 feet wide with gravel surface. Core wall mandatory. Seed banks to grass. 0.6" to 1.0" in 10', except bottom of recircula- tion ponds, which should be level. Headbox with concrete overflow wall and adjustable metal weir plate control for indi- vidual raceways, or pipe discharging above the pond water surface; inlet should be full width of raceway. W Cast iron pipe with shutoff valve for take-off to ponds. It may be desirable to have two supplies: the main suppl> at the outlet to 3() KISH HAICUKKV MANAGEMENT Table 4. continued. ITEM HATCHERY SYMBOL CRH ERIA Rearing facilities {continued) Outlet control T Screen slots Freeboard Water changes T C Arrangement T C Electric lines Screens Walks T T C C provide fresh water in the catch basin when pond is harvested; and a supplemental sup- ply at the opposite end from the outlet structure. The supplies should enter the pond above the water surface or not lower than the top of the drain structure. Overflow full width of raceway, with standpipe or valve that is tamperproof. W Standard plans are available, and may be modified to include concrete baffle and valve where pumping is necessary. Struc- tures located in the bank should have ade- quate wing-walls to prevent sloughing of embankments. Outside catch basins should be used where practicable and serve as many ponds as feasible. Provide steps and walk- way around the catch basin. A minimum of 10"'ii slope in pipeline from the pond kettles to the outside catch basin is required. Out- side catch basins must have a fresh water supply available. Kettle chimneys should have 1" X 3" key way for safety covers. W Double slots in walls and floor at drain end, either 2-inch double angle or 2-inch channel of noncorrosive metal. 6-12 inches in raceways, pools. W In earthen ponds, 18 inches is sufficient. Ponds should be oriented to limit sweep of prevailing winds. W Minimum of 3 per hour, except one for Bur- rows recirculation ponds. W Double in series or in rows. Provide 14 feet or wider driveways between series. Allow suffi- cient fall between series for aeration; 18-24 inches is recommended, up to 14 feet is acceptable. W To be laid at the time of construction either in raceway walls or alongside with outlets spaced to satisfy operational requirements. Consider automatic feeder installations, floodlights, raceway covers, etc. W Perforated noncorrosive metal. W 14-16-inch concrete walkways, broom finish; aluminum skid-proof grating. For safety all open flumes, control structures, etc., should be covered with nonslip grating. HAICHERV REC^UIRLMENTS 37 Table 4. con tinued. ITEM HATCHERY SYMBOL CRITERL\ Rearing facilities [continued) Type of soil T C Troughs Type Screens Arrangement Tanks Type and size Egg incubation Buildings General layout T C T C T T T W W W W W Screens T C w Water changes T C w Arrangement T c w w Effluent treatment T C W W General construction T C W Avoid rocky terrain or unstable soil conditions such as swamps and bogs. Obtain subsoil information during site investigations. Con- duct test borings prior to selecting pond site. Avoid rocky soil, gravel, limestone substrata, or old stream beds. Seek solid ground rea- sonably impervious to water for earthen ponds. Fiberglass, metal, wood; rectangular, 14' X 14" X 8" deep or rectangular 16' X 16" X 16" double, deep-type. Perforated metal. Double with individual supply and drains. If used in series, allow fall between tanks of at least 12 inches and an aisle between tanks. Circular 4-8 feet diameter, sloped bottoms J inch per foot of radius; rectangu- lar, 3'x3'x30' double arrangement. Perforated aluminum. Five per hour. For convenience, with sufficient aisle space for handling and removing fish. Commercial incubators such as Heath or equivalent recommended. Jar culture or hatching boxes may be adaptable in some instances. Provide settling basin of size and design that will effectively settle out solids from used water prior to its release from the hatchery proper. Arrange buildings to expedite work, to present a pleasing appearance, and to be compatible with topography and approach routes. Con- sideration of local architecture is desirable. Provide adequate spacing between buildings for fire control. Design for economical heating; steam or hot water is preferred for large buildings. Avoid condensation problems in the tank room by providing adequate insulation, ventilation, and heating. 38 FISH HATCHERY MANAGEMKNT Table 4. continued. ITEM HATCHERY SYMBOL CRITERIA Hatchery buildings Arrangement Tank Incubation area Feed storage General storage Office Laboratory W W c w w T C W T C W T C W Hatchery room, incubation area, feed storage, material storage, crew's room, toilet facilities, and small office area. Administrative offices and visitor facilities are not recommended for inclusion in hatchery building proper. Allow 2.,')-foot aisles between tanks and 4-fi feet around ends. Floor: concrete with broom finish, slope (l" in 10') for drainage. Walls and ceilings should be cement asbes- tos or other waterproof material. Water sup- ply and drain systems should be designed for flexibility and alteration. Buried lines should be kept to a minimum. A fish tran- sport system (pipe) from tank room to out- side ponds is desirable. Portals in the walls are convenient for moving fish out of the hatchery building. Separate room or designated area in the tank room should be provided for egg incubation. Use of stacked commercial incubators is recommended. Permit flexibility in arrang- ing incubators, small troughs, or tanks within the room. A separate storage area for dry feed is recom- mended because of undesirable odors. It should be located convenient to use area. Consider bulk feed storage and handling where more than 50 tons of feed is required annually. Provide storage for one-fourth of annual dry feed requirements with protec- tion against moisture and vermin. There should be proper ventilation and tempera- ture control. The delivery area should have turnaround room for large trucks. Include elevation loading dock or mechanical unloading equipment. If moist pellets are used, cold storage (lO°F) for fiO-days supply should be provided. Locate convenient to tank room, provide ample size for intended purpose, and design for maximum utilization of wall space with shelves and storage lockers. Main offices should be located in a separate administration building. Equipped and sized in accordance with antici- pated needs. HATCHERY REQUIREMENTS 39 Table 4. continued. ITEM HATCHERY SYMBOL CRITERIA Hatchery buildings {continued) Crew room T C Garage and storage building Shop Oil and paint storage Fertilizer and chemical storage W w w w w Room should provide locker space for each employee, and be adequate to serve as a lunch room. Shower facilities should be pro- vided. Size of building or buildings is dependent upon the number of truck stalls required and the amount of material to be stored. Concrete floors should be broom finish with a 1" in 10' slope to doors. Minimum of 300 square feet, floor 1" in 10' slope to door or center drain. Provide heat- ing and electrical systems to satisfy require- ments, including 220-volt outlets; overhead door should be at least 10 feet wide and 9 feet high. Build in cabinets for tool storage and adequate work bench area. Provide a separate building, or materials may be stored in another building if a special room rated for a '2-hour fire, with outside access, is provided. The electrical installa- tion should be explosion- proof. Provide heat if storage of water base paints is con- templated. Explosion-proof electrical fittings and positive ventiliation must be provided. Egg Incubation Incubation equipment is being modified constantly and several different types are available commercially. There are basically two concepts for the incubation of fish eggs. One method involves the use of wire baskets or rectangular trays suspended in existing hatchery troughs to support the eggs. The hatched fry drop through the wire mesh bottom of the basket or tray to the bottom of the trough. This method does not require additional building space because existing facilities are utilized. Other methods of egg incubation are jar culture or vertical tray incubation. Additional space in the hatchery building is required for this equipment. Control of water tem- perature should be part of any hatchery design involving egg incubation and hatching of fry. Heating or chilhng of water for optimum incubation 40 FISH HAICIIKKY MANAGEMENT temperature is practical with today's equipment, which requires relatively less water flow than older methods of egg incubation. Various types of egg incubation are described in detail in Chapter 3. Rearing Facilities Rearing units for intensive fish culture include starting tanks or troughs for swim- up fry, intermediate rearing tanks for fingerlings, and large outdoor rearing ponds or raceways. Rearing units should be constructed so they can be drained separately and quickly. They should be adequate not only for the normal operating flow in the hatchery but also for increased volumes of water needed during draining and cleaning of the facilities. Much personal opinion and preference is involved in the selection of a rearing unit. Fish can be raised successfully in almost all types of rearing units, although some designs have distinct advantages in certain applica- tions. Adequate water flow with good circulation to provide oxygen and flush metabolic waste products are of paramount importance in the selec- tion of any facility. Ease of cleaning also must be considered. CIRCULAR REARING UNITS Limited water supplies make semiclosed water recycling systems highly desirable. The most efficient involve circular units and pressurized water systems. By common acceptance, circular "tanks" refer to portable or semi- portable units up to 12 feet in diameter, while "pools" refer to permanently installed units up to 40 feet in diameter. There are basic criteria for construction and design of circular tanks and pools that are essential for their satisfactory operation. Double-walled or in- sulated tanks reduce external condensation and eliminate dripping water. Adequate reinforcement must be incorporated in the bottom of the tank to support the filled units. There is no need for a sloping bottom except to dry out the tank. Flat-bottomed tanks will self-clean well if proper water velocities are established. The walls should be smooth for easy cleaning. In the case of portable tanks, the preferred material is fiber glass, but good tanks can also be constructed of wood or metal. Large circular pools are usually constructed of masonry. Without proper equipment, removal of fish from larger circular tanks is difficult. Crowding screens facilitate the removal of fish (Figures 16 and 17). Some types of pools have inside collection wells for the accumulation of waste and removal of fish. HATCHERY REQUIREMENTS 41 Figure 16. Crowding screen used in smaller circular tanks. Large circular tanks and pools can be modified with a flat center bottom screen and an outside stand pipe to control water depth for ease of opera- tion. An emergency screened overflow is advisable in the event the bottom effluent screen becomes clogged. Horizontal slots in the drain screens allow better cleaning action and are not as easily clogged as round holes. They also provide more open screen area. Cylindrical center screens used in 4-6-foot diameter tanks provide better cleaning action if they are not per- forated in the upper portion, so that all effluent leaves the tank through the bottom portion. Self-cleaning properties of the pool are dependent on the angle at which inflowing water enters. The angle of inflow must be adjusted according to the volume of water being introduced and the water pressure (Figure 18). The carrying capacity (number or weight of fish per volume of con- tainer) of circular tanks and pools is superior to those of troughs, rectangu- lar tanks, and raceways if there is sufficient water pressure for reaeration. 42 FISH HATCHERY MANAGEMENT '?*i;|ii^i^uit/iialiji;. Figure 17. A fish crowder for large- diameter circular pools, (l) Screens are inserted into the thret -sided frame, after it is placed in the pool. (2) One end of the frame is anchored to the pool wall with a retaining rod, and the other end is carefully guided around the circumference of the pool, herding the fish ahead of the crowder. (3) The fish can be readily netted from the rectangular enclosure formed by the three sides of the crowder and weighed. Note the hanging dial scale and dip net (see inventory methods in Chapter 2). (4) The crowder also can be used for grading fish when appropriately spaced racks are inserted in the frame. Small fish will swim through the racks, leaving the larger ones entrapped. Aluminum materials should be used to construct the crowder to reduce weight. (FWS photo.) Air, driven into the water by the force of the inflowing water, provides ad- ditional oxygen as the water circulates around the tank or pool. Water in- troduced under pressure at the head end of rectangular troughs or race- ways does not have the same opportunity to reaerate the water flowing through those units. An example of the effect of water pressure on circular tank environments is presented in Table 5. At low pressures, the amount of dissolved oxygen limits the carrying capacity; at high pressures the buildup of metabolites (ammonia) limits production before oxygen does. There must be a compromise between velocity and the flow pattern best suited for feed distribution, self-cleaning action of the tank and the energy requirement of continuously swimming fish. This environment may not be suitable for such fish as northern pike, which do not swim actively all of the time. When properly regulated, the flow pattern in a circular tank will effectively keep feed particles in motion and will eventually sweep uneaten hatchery requirements 43 Table 5. ammonia and oxygen concentrations in identical circular tanks with high- and low-pressure water systems. tank diameters are 6 feet, tank volumes are ,'i30 gallons, flows are 10 gallons per minute (gpm), water changes are 1.13 per hour, fish size is 8.5 inches, and oxygen content of inflow water 8.5 parts per million (ppm). water pressures are pounds per square inch (psi). WATER PRESSURE HIGH (29 PSI) LOW (1..5 PSI) Fish weight (pounds) 100 200 250 300 100 200 250 Pounds/cubic foot 1.4 2.8 3.5 4.3 1.4 2.8 3.5 Pounds/gpm 10 20 25 30 10 20 25 Total ammonia (ppm) 0.21 0.44 0.80 0.89 0.21 0.44 0.74 Dissolved oxygen (ppm) 7.5 6..T 5.2 5.1 5.8 4.3 3.2 food and excrement toward the center for removal through the outlet screen. Velocity should never be great enough to cause fish to drift with the current. Velocities for small fry may be so low ttiat the tank does not self-clean and it will be necessary to brush accumulations of waste to the center screen. Oxygen consumption per pound of fish is higher in circular tanks than in troughs and raceways. This difference may be due to the increased ener- gy demand created by the higher water velocity in the circular tank. SWEDISH POND The Swedish Pond was developed specifically for Atlantic salmon. It is square with rounded corners and its operation is very similar to that of a circular tank. Water is supplied through a pipe at the surface of the water. Waste water leaves the tank through a perforated plate in the center of the unit and the water level is controlled by a standpipe outside the wall of the tank. This design provides a large ratio of surface area to water volume; some fish culturists feel that Atlantic salmon require more surface area as they do not stack over each other like other salmonids. RECTANGULAR TANKS AND RACEWAYS Originally rectangular raceways were elongated earthen ponds. Such ponds required considerable maintenance because weeds and plants grew along the banks and the pond walls eroded. Irregular widths and depths resulted in poor water flow patterns. Rectangular tanks or troughs generally are used for rearing small fry and fingerlings in the hatchery building (Figure 19). These can be made of aluminum, fiber glass, wood, or concrete. Potentially toxic material such as 44 FISH HATCHERY MANAGEMENT A Figure 18. Piping and water flow arrangement in (A) 20-ft and (B) 5-ft diame- ter circular tanks. The velocity and direction of water flow can be changed by swinging the horizontal pipe toward or away from the tank wall, and twisting the pipe clockwise to change the angle of inflow. The velocity is lowest when the water is directed downward into the tank, as shown in (B). The bottom screen plate and external head-box (arrow) eliminate vertical screens and standpipes in the center of the tank. Note that only one automatic feeder is required per tank. (FWS photo.) HATCHERY REQUIREMENTS 45 galvanized sheet metal should be avoided. Dimensions of raceways vary, but generally a length:width:depth ratio of 30:3:1 is popular. Properly con- structed raceways have approximately identical water conditions from side to side, with a gradual decline in dissolved oxygen from the head end to the lower end. Levels of ammonia and any other metabolic waste products gradually increase towards the lower end of the unit. Although this represents a deterioration of water quality, some hatchery workers feel that a gradient in water quality might be better for the fish because it attracts them to the higher quality water at the inflow end of the raceway. In circu- lar ponds, there is no opportunity for the fish to select higher oxygen and lower ammonia levels. FlGlRF. 1!). Rectangular aluminum troughs (background) and concrete tanks. Small swim-up fry generally are started on feed in the troughs and then transferred to the tanks when they are 1-1 j -inch fingerlings. (FWS photo.) 46 FISH HATCHERY MANAGEMENT Figure 20. Rectangular circulation rearing pond ("Burrows pond"). Water is recirculated around the pond with the aid of turning vanes (arrow). Waste water flows out through floor drains located in the center wall (not shown). (FWS photo.) Raceways should not vary in width, since any deviation can cause eddies and result in accumulation of waste materials. It is desirable to have ap- proximately one square foot of screen area at the outflow of the raceway for each 25 gallons per minute water flow. The percent open area of the screen material must also be considered. Raceways have some disadvantages. A substantial supply of water is required and young fish tend to accumulate at the inflow end of the unit, not utilizing the space efficiently. The raceway is believed by many hatchery operators to be the best suited for mass-producing salmon finger- lings. Its ease of cleaning, feeding, and fish handling make it desirable where ample water supplies are available. RECTANGULAR CIRCULATION REARING POND The rectangular circulation rearing pond is commonly known as the "Burrow's Pond" (Figure 20). Its basic design incorporates a center wall partly dividing a rectangular pond into two sections of equal width. Water is introduced into the pond under pressure and at relatively high velocities, through two inflow pipes located at opposite ends of the pond. The flow pattern is controlled with HATCHERY REQUIREMENTS 47 vertical turning vanes at each pond corner. The water generally flows parallel to the outside walls of the unit, gradually moves toward the center wall, and leaves the pond through the perforated plates in the pond bottom at opposite ends of the center wall. The rectangular pond operates well at a water depth of either 30 or 36 inches, depth being controlled by a removable standpipe in the waste line. An advantage of the rectangular circulation pond is that fish are well dis- tributed through the pond and the water current carries food to the fish. This reduces concentrations of fish at feeding time. It is relatively self- cleaning due to the water path created by the turning vanes at inflows of 400 gallons per minute or greater. The water flow and turbulence along the center wall carry debris and waste material to the outlet. Pond dimensions and water flows are very specific, and any change in the design criteria of this rearing unit may drastically alter the hydraulic performance. This can prove a distinct disadvantage when flexibility of fish loads and water flows is desired. EARTHEN PONDS There is general agreement that concrete raceways are cheaper to maintain and operate than earthen ponds. Many fish culturists contend, however, that fish reared in dirt raceways and ponds are healthier and more colorful, have better appearing fins, and are a better product. Rectangular earth ponds usually are more convenient and efficient, and may range in size from | acre to 3 acres or more. Large ponds of irregular shapes are more difficult to clean, and it is harder to feed and harvest fish and to control disease in them. It is doubtful that fish production will become as intensive in large earthen ponds as in smaller types of rearing units that have more water changeovers. Earth ponds do have relatively low water requirements and produce some natural food. Successful culturing of trout and salmon have been accomplished in this type of facility and use of supplemental aeration has increased catfish production dramatically in recent years. Harvest methods must be considered in the design of an earthen pond. Ponds must be drainable and contain a basin or collection area for harvest- ing the fish (Figures 21 and 22), although many of the fish can be seined from the pond before it is drained. The bottom of the pond should slope gradually toward the outlet from all sides. Pond banks should be built with as steep a slope as possible to avoid shallow-water areas along the edge of the ponds. Shallow areas collect waste material and allow dense growths of vegetation to develop. Topography for construction of earthen ponds should be gently sloping and should have only moderate relief that can be economically removed. 48 FISH HATCHERY MANAGEMENT DRAIN PIPE < ^ CATCH BASIN CREEN 7T^^ » = ♦ \\ * « «»"="// ■(■=://., «« Figure 21. Pond outlet with catch basin. (Source: Davis 1953) The soil type is extremely important; clay soil or subsoil is best. Seepage tests at the pond sites are highly desirable. Seepage loss is not as important in intensive salmon or trout culture where abundant quantities of water flow through the pond, but is important in warmwater fish culture where circulating water flows are not required. Pond banks must be stable and well drained, because heavy tractors and feed trucks must have access to the ponds preferably along gravelled road- ways. Cement or transite material is best for water supply lines and drain lines. CAGE CULTURE There is growing interest in cage culture of warmwater species such as cat- fish. This involves rearing fish in small enclosures built of wire or plastic netting stretched over a frame. The cages are attached in series to floating platforms and anchored in rivers, lakes, and ponds or in protected areas along coastal shores (Figure 23). Water currents and wind action carry HATCHERY REQUIREMENTS 49 ^HAMttmmaimm:^ i* J Figure 22. A pond catch basin should have a supply line (arrow) to provide fresh water to the fish when they are collected in the basin. This pond outlet also has a valve to open the pond drain. away wastes and provide fresh water. Cage culture is readily adapted to areas that cannot be drained or from which fish cannot be readily har- vested. However, good water circulation must be assured, as an oxygen depletion in water around cages can cause catastrophic fish losses. Disease control is very difficult in cage culture and labor requirements are high. Feeding and treatment for disease must be done by hand. Largemouth bass fingerlings have been experimentally grown in cages. Cylindrical instead of rectangular containers were used to prevent crowd- ing in corners, which might cause skin damage to active fish such as bass. Moist trout pellets were fed to the fish; a retaining ring kept the food in- side the cage until it could be eaten. Figure 23. Cage culture of catfish. IFWS photo.) 50 FISH HATCHERY MANAGEMENT PEN REARING Marine culture of salmon and trout in cages is called "pen rearing." Pen culture developed in Scandinavia and Japan, and commercial operations began recently in Washington state. Rainbow trout and Atlantic, chinook, and coho salmon have been cultured in sea water. Coho salmon have been the most popular in the United States because they are relatively resistant to disease and can be fed formulated feeds. After initial rearing in fresh water, the juvenile fish complete their growth to marketable size in saltwa- ter pens. The term "sea ranching" is used when hatchery-reared salmon are released as smolts and allowed to migrate to the ocean to complete the ma- rine portion of their life cycle. Pen rearing relies on tidal currents to supply oxygen and flush out meta- bolic wastes. The pens and floating structures cost less than a fish hatchery on land, but must be protected from storms and high winds, and some type of breakwater may be necessary. Some freshwater facilities must be avail- able on land, however, to incubate the salmon eggs and initially rear the fry. Water temperatures should not fluctuate greatly during pen culture; 50— 57°F are best for salmon. Prolonged higher temperatures lead to disease problems. Although disease has been a serious problem in saltwater farm- ing, recent developments in immunization of fish with vaccines show great promise for overcoming this (Chapter 5). SELECTION OF REARING FACILITIES No single pond type will meet all requirements of fish hatcheries under all rearing conditions. Topography of the land, water source, species of fish being reared, and availability of funds and material will influence the selec- tion of the rearing unit. There is a wealth of literature describing the strong and weak points of various hatchery rearing facilities, much of it conflicting. Personal preference based on experience tends to play a key roll in making a selection. As pointed out previously, all of the types of rearing units described successfully raise fish. In any hatchery construction there are several important objectives that must be kept in mind: (l) to provide a compact rearing unit layout that will allow future development of the hatchery; (2) to provide adequate intake and outlet water supply facilities to meet the special requirements of pond cleaning, treatment of fish for disease, and collection and handling of fish; (3) to allow sufficient slope on pond bottoms for complete drainage and provide for a practical and efficient means of collecting fish for removal, sorting, or treating; and (4) to provide adequate water and rearing space to safely accommodate the anticipated production of the hatchery. HATCHERY REQUIREMENTS 51 Table 6 summarizes some of the characteristics of the various rearing units that have been described. Biological Design Criteria Every species of fish has basic environmental requirements and each has optimum conditions under which it thrives and can be efficiently cultured. Biological criteria are essential in the design of any fish culture facility and these criteria must be recognized before a successful fish rearing program can be developed. The following comments are abstracted from Nightingale (1976). Information required in designing a facility includes fishery management needs, fish physiology, chemical requirements, disease, nutrition, behavior, genetics, and fish handling and transportation. These criteria must be developed for each species to be cultured. The fishery management criteria include identification of the species to be reared, desired sizes for production, and desired production dates. Manage- ment criteria are usually listed as the number and length (or weight) of fish that are required on certain dates. Physiological criteria include oxygen consumption for various fish sizes and optimum temperatures for broodstock holding, egg incubation, and rearing. Required rearing space, water flows, and spawning and incubation methods are included in these criteria. Chemical criteria include water quality characteristics that affect the species of fish to be reared, such as tolerable gas saturation, pH, and water hardness. Disease criteria include methods for disease prevention and treatment. Nutrition criteria involve the types of feeds, feeding rates, and expected food conversions at different temperatures and fish sizes. Behavior criteria are needed to identify special problems such as cannibal- ism and excessive excitability; for example, a decision may be made to use automatic feeders to avoid a fright response. Genetic criteria involve selection of specific strains and matching of stocks to the environment. Transportation and handling criteria involve the acceptable procedures and limitations for handling and moving the fish. The application of these criteria to the particular circumstances at each hatchery can result in a biologically sound culture program. A program can be developed by combining the management and physiological criteria with the particular species and water temperatures to be utilized. Rearing space and water flow requirements can be defined and combined with the other criteria to establish a suitable hatchery design. Good program development for fish hatchery design should include, in addition to biological criteria, adequate site evaluation, production alterna- tives, and layout and cost estimates. 52 I-ISH HAICHEKY MANAGEMENT Table 6. summary of rearing unit characteristics for fish hatcheries. TYPE UA 1 KR SLl'I'l.V I()I'(K.KA1'II^ Various sizes available in a variety of materi- als. Can be used for small or large groups of fish. Circular tanks and ponds Pump or high-pressure gravity; low flow volume. Level or sloped. Fairly restricted to one size; used e.xtensively with large groups of production fish. Reitangular-circ II latum rearing ponds Same as above. Same as above. Various sizes; used for small or large groups of fish. Larger units made of concrete. Swedish ponds Same as above. Same as above. Small tanks made with a variety of materials; used for small or large groups of fish. Race- ways generally made of concrete for large groups of production fish. Rectangular tanks and raceways High- or low pressure gravity; high flow volume preferred. Slope preferred for reaeration ol water between units. Generally for large groups of production fish. Ear/hen ponds High- or low pressure gravity; high or low flow volume. Level preferred. Consid- erable area of land required. Various net materials; can be built in various sizes. Generally smaller units than raceways or ponds. Cage culture and pen rearing Lake or pond with some current or protected coastal or stream area. Protected shoreline. HATCHERY REQUIREMENTS 53 DISKASE CON IROl, SPFXIAL FEATLRKS Circular tanks and pond ^ Can be a problem bee ause of recirculating Controlling velocities, self-cleaning. v\ater and low How rates. Reclangular-circulation rearing ponds Same as abo\e. Uniform velocity throughout; relatively self-cleaning. Expensive construction. Swedish ponds Same as abo\ e. Self-cleaning; large surface area to depth ratio. Moderate velocitv control. Rectangular tanks and raceways \'er> good if tank designed properly. Relatively ine.xpensi\e construction, readil) adaptable to mechanization (cleaning, feeding, crowding). Earthen ponds A problem because of flow patterns and Many attributes of a natural environment, buildup of wastes hc\m large groups of production fish. Cage culture and pen rearing Difficult Inexpensive facilitv ; water readily a\ail able. 54 FISH HATCHERY MANAGEMENT Table 7. typical biological data organized into a concise format to aid IN developing a rearing program and ultimately designing a hatchery. (SOURCE: KRAMER, CHIN AND MAYO 1976.) TEMP- AVERAGE TOTAL FLOW SPACE LOCA- ATURE NUMBER LENGTH WEIGHT NEEDED NEEDED DATE EVENT TION (T) (millions) (INCHES) (POUNDS) (gpm") March 1.^ 'Egg take Incub- tion 150 Jars 54 45 150 March 29 Hatch April 1 Begin feed 8 ST* 54 15 0.2 150 60 1,280 April 1 Release 54 3 0.2 300 May 1 3 RW' 60 1.3 1.0 520 380 4,730 June 1 4 RW' 66 1.1 2.0 3,780 700 7,000 June 15 Release 1.0 2.6 7,000 "Gallons per mi nute. Starter tanks. Raceways. APPLICATION OF BIOLOGICAL CRITERIA The following is a brief explanation of the methodology and format used by Kramer, Chin and Mayo, engineering consultants, in formulating a rear- ing program based on biological criteria. A typical program is used to demonstrate step-by-step planning. Table 7 illustrates how collected bio- logical data can be organized concisely. (1) Determine temperature. The first step in preparing a rearing program is to obtain either the ambient or adjusted monthly water temperature ex- pected for use in the hatchery system. Example: 54°F. (2) Determine date of event and length of fish. As a baseline for the program projection, the date of spawning of the stock that will serve as parents for the hatchery stocks should be determined. Example: March 15. Determine the date of hatching and initial feeding. Because water temperatures in this example will be approximately 54°F, calculate Daily Temperature Units (DTU) as follows: 54T-32°F = 22 DTU per day. (The standard basis for calculating temperature units is 32°F.) Determine days to hatch, if 300 DTU are required to hatch eggs: 300 DTU ^ 22 DTU = 14 days. Adding 14 days to March 15 makes the expected hatching date March 29. Deter- mine the day to begin feeding, if 40 DTU are required for hatched fry to develop to feeding stage: 40 DTU -^ 22 DTU = 2 days. This results in an anticipated feeding date of April 1. In this example, 12,000,000 fry are to be released immediately to begin natural feeding in a rearing pond, leaving HATCHERY REQUIREMENTS 55 3,000,000 fry in the hatchery. Final release in this example calls for 1,000,000, 2:7-inch fingerlings. Determine the date fish will reach this size. A search of the literature indicates that fry begin feeding at a length of 0.2 inch. By a method described in Chapter 2, the growth is projected; the fish will average 2.6 inches on June 15. (For convenience, all releases have been assumed to fall on either the first or fifteenth of a month.) (3) Determine weight. Fish lengths can be converted to pounds from the length/weight tables provided in Appendix I. (4) Determine the number of fish or eggs required to attain desired production. For example, to determine requirements on June 1 for a release of 1,000,000 on June 15, use one-half the monthly anticipated mortality (7.5% in our example). Convert this to survival: 100% — 7.5% = 92.5%, or 0.925. Divide the required number of fish at the end of the period by this survival to determine the fish needed on June 1: 1,000,000-0.925= 1,081,000. This can be rounded to 1.1 million for planning purposes. (5) Determine total weight. Total weight is determined by multiplying weight per fish (Appendix l) by the number of fish on that date. (6) Determine flow requirements. Adequate biological criteria must be developed for the species of fish being programmed before flow rates can be calculated. For this example a value of 1 gallon per minute per 10 pounds of fish was used. Because there is a total weight of 3,850 pounds, 3,850^10 = 385 gallons per minute are required. Flow requirements for in- cubation are based upon 1 gallon per minute per jar. (7) Determine rearing space. All density determinations follow the same method described for Density Index determinations in Chapter 2. Biologi- cal criteria must be developed for each species of fish being programmed. Bibliography American Public Health Association, American Water Works Association, and Water Pollu- tion Control Federation, 1971. Standard methods for the examination of water and wastewater, 13th edition. American Public Health Association, Washington, D.C. 874 P- Andrews, James W., Lee H. Knight, and Takeshi Mural 1972. Temperature requirements for high density rearing of channel catfish from fingerling to market size. Progressive Fish-Culturist 34(4):240-241. Banks, Joe L., Laurie G. Fowler, and Joseph W. Elliott. 1971. Effects of rearing tem- perature on growth, body form, and hematology of fall chinook fingerlings. Progressive Fish-Culturist 33(l):20-26. Baummer, John C, Jr., and L. D. Jensen. 1969. Removal of ammonia from aquarium water by chlorination and activated carbon. Presented at the 15th Annual Professional Aquarium Symposium of the American Society of Ichthyologists and Herpetologists. Bonn, Edward W., Willl\m M. Bailey, Jack D. Bavless, Kim E. Erickson, and Robert E. Stevens. 197fi. Guidelines for striped bass culture. Striped Bass Committee, South- ern Division, American Fisheries Society. 103 p. 56 FISH HATCHERY MANAGEMENT Bovi), Claude E. 1!)7;). Water quality in warmwater fish ponds. Agricultural Experimental Station, Auburn University, Auburn, Alabama. 3.')i) p. Brki I", J. R. \932. Temperature tolerance in young Pacific salmon, Genus Oncorhynchus. Jour- nal of the Fisheries Research Board of Canada 9(()):265-323. Burrows, Roger E. 19(i3. Water temperature requirements for maximum productivity of sal- mon. Pages 29"34 in Proceedings of the Twelfth Pacific Northwest Symposium on Water Pollution Research, US Department of Health Education and Welfare, Public Health Service, Corvallis, Oregon. 1972. Salmonid husbandry techniques. Pages 37.'J-402 in Fish nutrition. Academic Press, New York. , and Harry H. Chenoweth. 1970. The rectangular-circulating rearing pond. Progres- sive Fish-Culturist 3'2(2):fi7-8(). , and Bobby D. Combs. 1968. Controlled environments for salmon propagation. Pro- gressive Fish-Culturist 30(3):123-136. Buss, Keen and E. R. Miller. 1971. Considerations for conventional trout hatchery design and construction in Pennsylvania. Progressive Fish-Culturist 33(2):86^94. Chapman, G. 1973. Effect of heavy metals on fish. Pages 141-l(i2 in Heavy metals in the environment. Water Resources Research Institute Report SEMN WR 016.73. Combs, Bobby D. 196,5. Effect of temperature on the development of salmon eggs. Progressive Fish-Culturist 27(3);134-137. Croker, Morris C. 1972. Design problems of water re-use systems. Great Lakes Fishery Biology — Engineering Workshop (Abstracts), Traverse City, Michigan. Davis, H. S. 1953. Culture and diseases of game fish. University of California Press, Berkeley. 332 p. DeCola, Joseph N. 1970. Water quality requirements for Atlantic salmon. US Department of the Interior, Federal Water Quality Administration, Northeast Region, Needham Heights, Massachusetts. 52 p. Dennis, Bernard A., and M. J. Marchyshyn. 1973. A device for alleviating supersaturation of gases in hatchery water supplies. Progressive Fish-Culturist 3,5(1 ):,'i,'i-58. Dwyer, William P., and Howard R. Tisher. 1975. A method for settleable solids removal in fish hatcheries. Bozeman Information Leaflet Number 5, LIS Fish and Wildlife Service, Bozeman, Montana. 6 p. Eicher, George J., Jr. 1946. Lethal alkalinity for trout in water of low salt content. Journal of Wildlife Management 10(2):82-85. Ellis, James E., Dewey L. Tackett, and Ray R. Carter. 1978. Discharge of solids from fish ponds. Progressive Fish-Culturist 40(4): 165^166. Emig, John W. 1966. Bluegill sunfish. Pages 375-392 in Alex Calhoun, editor. Inland fisheries management. California Department of Fish and Game, Sacramento. Environmental Protection Agency (US). 1975. Process design manual for nitrogen control. US Environmental Protection Agency, Office of Technology Transfer, Washington, D.C. GoDBY, William A., Jack D. Larmoyeux, and Joseph J. Valentine. 197(i. Evaluation of fish hatchery effluent treatment systems. US Fish and Wildlife Service, Washington, D.C. .59 p. (Mimeo.) Hagen, William, Jr. 1953. Pacific salmon, hatchery propagation and its role in fishery man- agement. US Fish and Wildlife Service, Circular 24, Washington, D.C. 56 p. Herrmann, Roberi B., C. E. Warren, and P. Doudoroff. 1962. Influence of oxygen con- centration on the growth of juvenile coho salmon. Transactions of the American Fisheries Society 91 (2): 155-167. Hokanson, K. E. F., J. H. McCormigk, and B. R. Jones. 1973. Temperature requirements for embryos and larvae of the northern pike, Esox lucius (Linnaeus). Transactions of the American Fisheries Society 102(l) :89-100. HATCHERY REQUIREMENTS 57 , , , and J. H. TUCKER. 1973. Thermal requirements for maturation, spawning, and embryo survival of the brook trout, Salvelinus fontinalis. Journal of the Fisheries Research Board of Canada 30(7):97.S-984. Hunter, Garry. 1977. Selection of water treatment techniques for fish hatchery water sup- plies. Baker Filtration Company, .53,52 Research Drive, Huntington Beach, California. HUTCHENS, Lynn H., and Robert C. Nord. 1953. Fish cultural manual. US Department of the Interior, Albequerque, New Mexico. 220 p. (Mimeo.) International Atlantic Salmon Found.^tion. 1971. Atlantic salmon workshop. Special Publication Series 2(l). 88 p. Jensen, Raymond. 1972. Taking care of wastes from the trout farm. American Fishes and US Trout News, lfi(5): 4-6, 21. Jones, David, and D. H. Lewis. 197fi. Gas bubble disease in fry of channel catfish ktalurus punctatus. Progressive Fish-Culturist 38(l):41. Kelley, John W. 1968. Effects of incubation temperature on survival of largemouth bass eggs. Progressive Fish-Culturist 30(3):1.59-163. Knepp, G. L., and G. F. Arkin. 1973. Ammonia toxicity levels and nitrate tolerance of chan- nel catfish. Progressive Fish-Culturist 35(4):221-224. KOENST, Walter M., and Lloyd L. S.MITH, Jr. 1976. Thermal requirements of the early life history stages of walleye, Stizostedion vitreum vitreum, and sauger, Stizosledion canadense. Journal of the Fisheries Research Board of Canada 33:1130-1138. KoNIKOFF, Mark. 1973. Comparison of clinoptilolite and biofilters for nitrogen removal in recirculating fish culture systems. Doctoral dissertation. Southern Illinois University, Carbondale. 1975. Toxicity of nitrite to channel catfish. Progressive Fish-Culturist 37(2):96-98. Kramer, Chin and Mayo, Incorporated. 1972. A study for development of fish hatchery water treatment systems. Report prepared for Walla Walla District Corps of Engineers, Walla Walla, Washington. 1976. Statewide fish hatchery system, State of Illinois, CDB Project Number 102-010- 006. Seattle, Washington. 1976. Statewide fish hatchery program, Illinois, CDB Project Number 102-010-006. Seattle, Washington. 1976. Washington salmon study. Prepared for the Washington Department of Fisheries. Seattle, Washington. KWAIN, WeN-HWA. 1975. Effects of temperature on development and survival of rainbow trout, Salmo gairdneri, in acid water. Journal of the Fisheries Research Board of Canada 32(4):493-497. Lagler, Karl L. 1956. Freshwater fishery biology. William C. Brown, Dubuque, Iowa. 421 p. Larmoyeux, Jack D. 1972. A review of physical-chemical water treatment methods and their possible application in fish hatcheries. Great Lakes Fishery Biology-Engineering Workshop (Abstracts), Traverse City, Michigan. , and R. G. PiPER. 1973. Effects of water re-use on rainbow trout in hatcheries. Progres- sive Fish-Culturist 35(l):2-8. _, and H. H. Chenoweth. 1973. Evaluation of circular tanks for salmonid produc- tion. Progressive Fish-Culturist 35(3):122-131. Leitritz, Earl, and Robert C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of Fish and Game, Fish Bulletin 164. 197 p. LlAO, Paul. 1970. Pollution potential of salmonid fish hatcheries. Technical Reprint Number 1-A, Kramer, Chin and Mayo, Consulting Engineers, Seattle, Washington. 7 p. li)7(). Salmonid hatchery wastewater treatment. Water and Sewage Works, December: 439-443. 58 FISH HAIX'HKRY MANAGEMENT , and Ronald D. Mayo. 1972. Salmonid hatchery water re-use systems. Technical Reprint Number 23, Kramer, Chin and Mayo, Consulting Engineers, Seattle, Washing- ton. () p. , and 1974. Intensified fish culture combining water reconditioning with pollu- tion abatement. Technical Reprint Number 24, Kramer, Chin and Mayo, Consulting Engineers, Seattle, Washington. \'A p. MacKinnon, Daniel F. 1!)()9. Effect of mineral enrichment on the incidence of white-spot disease. Progressive Fish-Culturist 3l(2):74-7H. Mahnken, Ct)NRAD V. W. 197r). Commercial salmon culture in Puget Sound. Commercial Fish Farmer and Aquaculture News 2(l):H 14. Mayo, Ronald D. 1!)74. A format for planning a commercial model aquaculture facility. Technical Reprint Number 30, Kramer, Chin and Mayo, Consulting Engineers, Seattle, Washington, l.j p. McCoRMiCK, J. Howard, Kenneth E. F. Hokan.son, and B. R. Jones. 1!)72. Effects of temperature on growth and survival of young brook trout, Salveli/ius fonttnalis. Journal of the Fisheries Research Board of Canada 29(H): 1 107- 1 1 12. McKee, Jack E., and Harold Wolf. 19<)3. Water quality criteria. California State Water Quality Control Board, Publication Number 3-A, Sacramento. .')4K p. McNeil, William J., and Jack E. Bailey. 197.'J. Salmon rancher's manual. National Marine Fisheries Service, Northwest Fisheries Center, Auke Bay Fisheries Laboratory, Auke Bay, Alaska, Processed Report. 9.') p. MirCHUM, Doi c:la,S L. 1971. Effects of the salinity of natural waters on various species of trout. Wyoming Game and Fish Commission, Cheyenne. Nighiingale, John W. 197(). Development of biological design criteria for intensive culture of warm and coolwater species. Technical Reprint Number 44, Kramer, Chin and Mayo, Consulting Engineers, Seattle, Washington. 7 p. Novotny, Anihony J., and Conrad V. W. Mahnken. 1971. Farming Pacific salmon in the sea. Fish Farming Industries, Part 1, 2(,S);()-9. Parker, Nick C, and Bill A. SlMCo. 1974. Evaluation of recirculating systems for the cul- ture of channel catfish. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 27: 474-487. Rhodes, W., and J. V. Merriner. 1973. A preliminary report on closed system rearing of striped bass sac fry to fingerling size. Progressive Fish-Culturist 3,') (4): 199 201. Rosen, Harvey M. 1972. Ozone generation and its economical application in wastewater treatment. Water and Sewage Works 119(9): 114. Ro.senlcnd, Bruce D. 197.'i. Disinfection of hatchery influent by ozonation and the effects of ozonated water on rainbow trout. In Aquatic applications of ozone. International Ozone Institute, Syracuse, New York. Rucker, Robert R. 1972. Gas-bubble disease of salmonids: a critical review. Technical Paper Number .t8, US Fish and Wildlife Service, Washington, D.C. 11 p. Russo, R. C, C. E. Smith, and R. V. Thurston. 1974. Acute toxicity of nitrite to rainbow trout [Salmo gairdneri). Journal of the Fisheries Research Board of Canada 3l(lO);l(ir)3-l(i,''K). Shannon, Eiigene H. 1970. Effect of temperature changes upon developing striped bass eggs and fry. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 23:2f)5-274. Smith, C. E., and Warren G. Williams. 1974. Experimental nitrite toxicity in rainbow trout and chinook salmon. Transactions of the American Fisheries Society 103(2) :389- 390. Snow, J. R., R. O. Jones, and W. A. Rogers. 19f)4. Training manual for warmwater fish cul- ture, 3rd revision. US Department of Interior, Bureau of Sport Fisheries and Wildlife, Warm Water In-service Training School, Marion, Alabama. 244 p. HATCHERY REQUIREMENTS 59 SpeecE, Richard E. 1973. Trout metabolism characteristics and the rational design of nitrifi- cation facilities for water re- use in hatcheries. Transactions of tlie American Fisheries Society 102(2) :323-334. , and W. E. Leyendecker. 19fi!). Fish tolerance to dissolved nitrogen. Engineering Experimental Station Technical Report, New Mexico State University, Technical Report Number 59, Las Cruces. Spotte, Stephen H. 1970. Fish and in\ertebrate culture. John Wiley and Sons, New York. 14,5 p. Stickney, Robert R., and B. A. Sl.MCO. 1971. Salinit> tolerance of catfish hybrids. Transac- tions of the American Fisheries Society 100(4) :790-792. Swingle, H. S. 19.57. Relationship of pH of pond waters to their suilabiiitv of fish culture. Proceedings of the Pacific Scientific Congress 10:72 7."). WeDEMEYER, G.\RY a. 1977. Environmental requirements for fish health, Pages 41 ,5.") in Proceedings of the International Symposium on Diseases of Cultured Salmonids, Tavolek, Inc., Seattle, Washington. Wedemeyer, G.-^RY a., and J.\mks W. Wood. 1974. Stress as a predisposing factor in fish diseases. US Fish and Wildlife Service, Fish Disease Leaflet 38, Washington, D.C. H p. Westers, Harry, and Keith M. Pratt. 1977. Rational design of hatcheries for intensive sal- monid culture, based on metabolic characteristics. Progressive Fish-Culturist 39 (4): 157- 165. WiLLOUGHBY, HaRVEY, HOWARD N. Lar.SEN, and J. T. BowEN. 1972. The pollutional effects of fish hatcheries. American Fishes and US Trout News 17(3):6-7, 20-21. 2 Hatchery Operations Production Methods The information presented in this chapter will enable the fish culturist to employ efficient management practices in operating a fish hatchery. Proper feeding practices, growth projections, and inventory procedures are a few of the essential practices for successful management. Although particular species are used in examples, the concepts and procedures presented in this chapter can be applied to warmwater, coolwater, and coldwater fish cul- ture. Length- Weight Relationships Increase in fish length provides an easily measured index of growth. Length data are needed for several aspects of hatchery work; for example, production commitments are often specified by length. On the other hand, much hatchery work, such as feed projections, is based on fish weight and its changes. It is very useful to be able to convert back and forth between length and weight without having to make measurements each time. For this purpose, standardized length-weight conversion tables have been avail- able for several years. These are based on the condition factor, which is the ratio of fish weight to the length cubed. A well-fed fish will have a higher 60 HATCHERY OPERATIONS 61 ratio than a poorly fed one of the same length; it will be in better condi- tion, hence the term condition factor. Each fish species has a characteristic range of condition factors, and this range will be small if fish do not change their bodily proportions as they grow (some species do change, but not the commonly cultured ones). Rel- atively slim fish, such as trout, have smaller typical condition factors than do stouter fish such as sunfish. The value for a condition factor varies according to how length is meas- ured and, more importantly, according to the units of measurement, English or metric. For purposes of this book, lengths are total lengths, measured from the tip of the snout (or lower jaw, whichever projects farther forward) to the tip of the tail when the tail is spread normally. When measurements are made in English units (inches and pounds), the symbol used is C. For metric measurements (millimeters, grams), the sym- bol is K. The two types of condition values can be converted by the for- mula C = 36.13/r. In either case, the values are quite small. For example, for one sample of channel catfish, condition factors were C = 2918 x 10 ' (0.0002918) and A' = 80.76 x 10"^ Once C is known, the tables in Appendix I can be used to find length- weight conversions. The eight tables are organized by increasing values of C, and representative species are shown for each. Because not all species are listed, and because C will vary with strains of the same species as well as with diet and feeding levels, it is wise to establish the condition factor independently for each hatchery stock. Weigh a sample of 50-100 fish together, obtaining a total aggregate weight. Then anesthetize the fish and measure their individual lengths. Finally, calculate the average length and weight for the sample, enter the values in the formula C (or A') = W/L', and consult the appropriate table in Appendix I for future length-weight conversions. Growth Rate Growth will be considered as it relates to production fish, generally those less than two years of age. The growth rate of fish depends on many factors such as diet, care, strain, species, and, most importantly, the water tem- perature (constant or fluctuating) at which they are held. Knowing the potential growth rates of the fish will help in determining rearing space needs, water-flow projections, and production goals. The abil- ity to project the size of the fish in advance is necessary for determining feed orders, egg requirements, and stocking dates. A key principle underly- ing size projections is that well-fed and healthy fish grow at predictable rates determined by water temperature. At a constant temperature, the 62 FISH HATCHERY MANAGEMENT daily, weekly, or monthly increment of length is nearly constant for some species of fish during the first 1^ years or so of life. Carefully maintained production records will reveal this growth rate for a particular species and hatchery. Example: On November 1, a sample of 240 fish weighs 12.0 pounds. The water temperature is a constant 50°F. From past hatchery records, it is known that the fish have a condition factor C of 4,010 x lO'^ and that their average monthly (30-day) growth is 0.66 inches. Will it be possible to produce 8-inch fish by next April 1? (1) The average weight of the fish is 12 pounds/240 fish = 0.05 pounds per fish. From the length-weight table for C — 4,000 x 10^ (Appendix l), the average fish length on November 1 is 5.00 inches. (2) The daily growth rate of these fish is 0.66 inch/30 days — 0.022 inch/day. (3) From November 1 through March 31, there are 151 days. (4) The average increase in fish length from November 1 through March 31 is 151 days x 0.022 inch/day = 3.32 inches. (5) Average length on April 1 is 5.00 inches + 3.32 inches = 8.32 inches. Yes, 8-inch fish can be produced by April 1. GROWTH AT VARIABLE WATER TEMPERATURES In the previous example a growth of 0.660 inch per month at 50°F was used. If all factors remain constant at the hatchery, growth can be ex- pected to remain at 0.660 inch per month and growth can readily be pro- jected for any given period of time. Not all hatcheries have a water supply that maintains a constant temperature from one month to the next. Unless water temperature can be controlled, a different method for projecting growth must be used. Growth can be projected if the average monthly water temperature and increase in fish length are known for several months. The Monthly Tem- perature Units (MTU) required per inch of growth must first be deter- mined. Monthly Temperature Units are the average water temperature for a one-month period, minus 32°F (the freezing point of water). Thus, a hatchery with a monthly average water temperature of 50°F would have 18 MTU (50° — 32°F) available for growth. To determine the number of MTU required for one inch of growth, the MTU for the month are divided by the monthly gain in inches (available from past records). Consider a hatchery with a water temperature that fluctuates from a low of 41°F in November to a high of 59°F during June. June would have 27 MTU (59°-32°F) but November would have only 9 MTU (41°-32°F). HATCHERY OPERATIONS 63 Let US assume from past records that the fish grew 0.33 inch in November and 1.00 inch in June. How many MTU are required to produce one inch of growth? (1) In November, 9 MTU ^ 0.33-inch gain = 29 MTU per inch of growth. (2) In June, 27 MTU ^ 1.0-inch gain = 27 MTU per inch of growth. Once the number of MTU required for one inch of growth is determined, the expected growth for any month can be calculated using the equation: MTU for the month ^ MTU required per inch growth = monthly growth in inches. Example: From past hatchery records it is determined that 27 MTU are required per inch of growth, and the average water temperature for the month of October is expected to be 48°F. What length increase can be expected for the month of October? (1) The MTU available during the month of October will be 16 (48°-32°F). (2) Since 27 MTU are required for one inch of growth, the projected in- crease for October is 0.59 inch (16 -^ 27). If fish at this hatchery were 3.41 inches on October 1, the size can be pro- jected for the end of October. The fish will be 4 inches long (3.41 + 0.59). Generally, monthly variation occurs in the number of MTU required per inch of growth, and an average value can be determined from past records. Carrying Capacity Carrying capacity is the animal load a system can support. In a fish hatchery the carrying capacity depends upon water flow, volume, exchange rate, temperature, oxygen content, pH, size and species of fish being reared, and the accumulation of metabolic products. The oxygen supply must be sufficient to maintain normal growth. Oxygen consumption varies with water temperature and with fish species, size, and activity. When swimming speed and water temperature increase, oxygen consumption increases. As fish consume oxygen they also excrete metabolic products into the water. If the fish are to survive and grow, ammonia and other metabolic products must be diluted and removed by a sufficient flow of water. Because metabolic products increase with increased fish growth and overcrowding, the water flow must be increased. Low oxygen in rearing units may be caused by insufficient water flow, overloading with fish, high temperature which lowers the solubility of 64 I'lSH HATCHERY MANAGEMENT oxygen in water, or low oxygen concentration in the source water. At hatcheries with chronic low oxygen concentrations and comparatively high water temperatures, production should be held down to levels that safely utilize the available oxygen, or supplemental aeration will be required. A depleted oxygen supply can occur at night in ponds that contain large amounts of aquatic vegetation or phytoplankton, and fish kills may occur after the evening feeding. Here again, aeration may be necessary to increase the oxygen supply. The carrying capacity of a rearing unit is usually stated as pounds of fish per cubic foot of water. Reference is also made to the pounds of fish per gallon per minute water inflow. In warmwater fish culture the carrying capacity as well as production is usually expressed in pounds per acre. Although these criteria are commonly used to express carrying capacity, they are often used without regard for each other. This can be misleading. The term Flow Index refers to the relationship of fish weight and size to water inflow and the term Density Index refers to the relationship of fish weight and size to water volume. There are clear distinctions in the affects of these two ex- pressions. The Flow Index deals specifically with the amount of oxygen available for life support and growth. The Density Index indicates the spa- cial relationship of one fish with another. Even though water flows may be adequate to provide oxygen and flush wastes, too much crowding may cause behavioral and physical problems among the fish. 1— o 2i^ ^ o DQ 3 y^^''^ ^ O ^1 n mn9 908 z / 30 / ?n (s 0 5 ^ \ 1 3 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 AVERAGE WEIGHT IN GRAMS Figure 24. Effect of fish size on maximum loading density of salmon, expressed as pounds of fish per cubic foot of water. (From Burrows and Combs 1968.) 451 401 5 o 351 E 30 o < o X CO 251 20L 15 CO Q 101 o Q. 0 HATCHERY OPERATIONS 65 co: ^^: 5g. lOg. 91/lb 45/lb FISH SIZE 15g. 30/lb Figure 25. Carrying capacity of oxygen- saturated water at normal activity level of fingerling chinook salmon as affected by water temperature and fish size. (Source: Bur- rows and Combs 1968.) Catastrophic fish losses because of overloaded rearing facilities are an ever-present danger in fish hatcheries. Many successful managers have operated a fish hatchery as an art, making judgements by intuition and ex- perience. However, there are several quantitative approaches for estimating carrying capacities in fish hatcheries. Experience has shown that fish density can be increased as fish increase in size. Figure 24 demonstrates the increase in density that is possible with chinook salmon. The carrying capacity of oxygen-saturated water at five water temperatures and several sizes of chinook salmon fingerlings is presented in Figure 25. Oxygen is usually the limiting factor at warmer 66 FISH HATCHERY MANAGEMENT 400^ 2 4 6 FISH LENGTH IN INCHES 8 Figure 26. The weight of different sized fish that would receive the same quantity of food (5 pounds) at a Hatchery Constant of 10. (Source: Piper 1972.) water temperatures. These two graphs do not depict optimum stocking rates but rather what we believe to be the maximum loading or density that must not be exceeded if normal growth rates are to be maintained. There is a relationship between the amount of feed that can be metabo- lized in a given rearing situation and the pounds of fish that can be carried in that rearing unit. There is much support for two major premises presented by David Haskell in 1955: 1. The carrying capacity is limited by (A) oxygen consumption, and (B) accumulation of metabolic products. 2. The amount of oxygen consumed and the quantity of metabolic prod- ucts produced are proportional to the amount of food fed. Haskell postulated that the accumulation of metabolic products and the consumption of oxygen are the factors that limit the carrying capacities of rearing units. If this is true, metabolism is the limiting factor because both the utilization of oxygen and production of metabolic products are HATCHERY OPKRATIONS 67 regulated by metabolism. If the carrying capacity of a unit is known for a particular size and species of fish at any water temperature, then the carry- ing capacity for another size of the same species held at other water tem- peratures will be the weight of fish that would consume the same amount of feed. FLOW INDEX The feeding guide developed by Buterbaugh and Willoughby demonstrates a straight line relationship between the length of fish in inches and percent body weight to feed (Figure 26). At a Hatchery Constant of 10, 100 pounds of 2-inch fish will receive the same quantity of food (5 pounds) as 200 pounds of 4-inch fish, or 400 pounds of 8-inch fish. (The Hatchery Con- stant is explained on page 245.) Haskell states, "if the carrying capacity of a trough or pond is known for any particular size of fish at a particular temperature, then the safe carry- ing capacity for other sizes and temperatures is that quantity of fish which will require the same weight of feed daily." By Haskell's premise, if 100 pounds of 2-inch fish is the maximum load that can be held in a rearing tank, then 200 pounds of 4- inch fish, 300 pounds of 6-inch, or 400 pounds of 8-inch fish also would be maximum loads. The following formula was derived for a Flow Index, where fish size in inches was used instead of weight of food fed to calculate the safe carrying capacity for various sizes of trout. F=W ^[L XI) F = Flow Index W = Known permissible weight of fish L = Length of fish in inches / = Water inflow, gallons per minute To determine the Flow Index [F], establish the permissible weight of fish in pounds [W) at a given water inflow (/) for a given size fish [L). The Flow Index [F) reflects the relationship of pounds of fish per gallons per minute water flow to fish size. As an example, 900 pounds of 4- inch trout can be safely held in a race- way supplied with 150 gallons per minute water. What is the Flow Index? /■ = 900-(4x 150) F = 1.5 How do you establish the initial permissible or maximum weight of fish when calculating the Flow Index? A Flow Index can be estimated by 68 FISH HATCHERY MANAGEMENT adding fish to a rearing unit with a uniform water flow until the oxygen content is reduced to the minimum level acceptable for the species at the outflow of the unit (.5 parts per million recommended minimum oxygen level for trout). The information required for calculating the Flow Index can also be determined with an existing weight of fish in a rearing unit by adjusting the water inflow until the oxygen content is reduced to 5 parts per million at the outflow of the unit. The Flow Index can then be used to determine the permissible weight of any size fish ( W), by the formula: W = F x L x /. Example: In the previous example, a Flow Index of 1.5 was determined for a raceway safely holding 900 pounds of 4-inch trout in 150 gallons per minute water flow, (l) How many pounds of 8-inch trout can be safely held? (2) How many pounds of 2-inch trout? (1) W = 1.5X8X 150 W = 1,800 pounds of eight-inch trout (2) W = 1.5 X2X 150 W = 450 pounds of two-inch trout Furthermore, when weight of fish is increased or decreased in a raceway, the water inflow requirement can be calculated by the formula: 1= W ^[F X L). For example, if 450 additional pounds of 8-inch trout are added to the above raceway containing 1800 pounds of 8-inch trout, what is the re- quired water inflow? / = (1800 + 450) ^(1.5x8) / = 188 gallons per minute water inflow The Flow Index shown in the example should not be considered a recommended level for all hatcheries, however, because other environmen- tal conditions such as water chemistry and oxygen saturation of the water may influence the holding capacities at various hatcheries. Table 8, with an optimum Flow Index of 1.5 at 50°F, considers the ef- fects of water temperature and elevation on the Flow Index. This table is useful in estimating fish rearing requirements in trout and salmon hatcheries. For example, a trout hatchery is being proposed at a site 4,000 feet above sea level, with a 55°F water temperature. Production of 4- inch rainbow trout is planned. How many pounds of 4-inch trout can be safely reared per gallon per minute water inflow (if the water supply is near 100% oxygen saturation)? HATCHERY OPERA IIONS 69 Table 8. flow index related to water temperature and elevation for trout and salmon, based on an optimum index of f = 1.3 at .'>0°f and '),000 feet elevation. oxygen concentration is assumed to be at or near 100% saturation. (source: bruce b. cannady, unpublished.) WATER TEMPER ATURE ELEVATION (FEET) ("F) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 40 2.70 2.61 2.52 2.43 2.34 2.25 2,16 2.09 2,01 1.94 41 2.61 2.52 2.44 2.35 2.26 2.18 2,09 2.02 1.94 1.87 42 2.52 2.44 2.35 2.27 2.18 2.10 2,02 1.95 1.88 1.81 43 2.43 2.35 2.27 2.19 2.11 2.03 1,!)4 1.88 1.81 1.74 44 2.34 2.26 2.18 2.11 2.03 l.!)5 1,87 1.81 1,74 1.68 45 2.25 2.18 2.10 2.03 1.95 1.88 1,80 1.74 1,68 1.61 46 2.16 2.09 2.02 1.94 1.87 1.80 1,73 1,67 1.61 1.55 47 2.07 2.00 1.93 1.86 1.79 1.73 1,66 1,60 1,54 1.48 48 1.98 1.91 1.85 1.78 1.72 1.65 1,58 1,53 1,47 1.42 49 1.89 1,83 1.76 1.70 1.64 1.58 1.51 1,46 1,41 1.36 50 1.80 1.74 1.68 1.62 l.,56 7.50 1.44 1,39 1,34 1.29 51 1.73 1.67 1.62 1.56 1.50 1.44 1.38 1,34 1,29 1.24 52 1.67 1.61 1.56 1.50 1.44 1.39 1,33 1,29 1,24 1.19 53 1.61 1.55 1.50 1.45 1.39 1.34 1,29 1,24 1,20 1.15 54 1.55 1.50 1.45 1.40 1.34 1.29 1.24 1,20 1,16 1.11 55 1.50 1.45 1.40 1.35 1.30 1.25 1,20 1,16 1,12 1.07 56 1.45 1.40 1.35 1.31 1.26 1.21 1,16 1,12 1,08 1.04 57 1.41 1.36 1.31 1.27 1.22 1.17 1,13 1,09 1.05 1.01 58 1.36 1.32 1.27 1.23 1.18 1,14 1,09 1 ,05 1.02 0.98 59 1.32 1.28 1.24 1.19 1.15 1,10 1,06 1 ,02 0.99 0.95 60 1.29 1.24 1.20 1.16 1.11 1,07 1.03 0,99 0.96 0.92 61 1.25 1.21 1.17 1.13 1.08 1,04 1.00 0,97 0.93 0.90 62 1.22 1.18 1.14 1.09 1.05 1,01 0.97 0,94 0.91 0.87 63 1.18 1.14 1.11 1.07 1,03 0,99 0.95 0,92 0.88 0.85 64 1.15 1.12 1.08 1.04 1.00 0,96 0.92 0,89 0.86 0.83 (1) The Flow Index [F] is 1.30 (Table 8, 4,000 feet elevation, 55°F tem- perature). (2) We can now estimate the permissible weight of trout that can be held per gallon per minute, by the formula W = F >^ L x /, where F=1.30, L = A inches, and / = 1 gallon per minute. Approximately 5.2 pounds of trout can be safely reared per gallon per minute water inflow (l.SO x 4 x l). The effect of water temperature on the Flow Index can readily be seen in the table. For instance, a hatchery at a 5,000- foot elevation having a water 70 FISH HATCHERY MANAGEMENT temperature drop from 50° to 46°F would have an increase in Flow Index from 1.50 to 1.80, because the metabolic rate of the fish normally would drop and the oxygen concentration would increase with a drop in water temperature. The reverse would be true with a rise in water temperature. Although Table 8 is useful for planning and estimating preliminary carrying capa- city in a trout or salmon hatchery, it should be considered only as a guide and specific Flow Indexes ultimately should be developed at each individual hatchery. The table is based on oxygen levels in the inflowing water at or near 100% saturation. If a rise or drop in oxygen occurs, there is a correspond- ing rise or drop in the Flow Index, proportional to the oxygen available for growth (that oxygen in excess of the minimum concentration acceptable for the species of fish being reared). Example: There is a seasonal drop in oxygen concentration from 11.0 to 8.0 parts per million (ppm) in the water supply of a trout hatchery, and the minimum acceptable oxygen concentration for trout is 5.0 ppm. The Flow Index has been established at 1.5 when the water supply contained 11.0 ppm oxygen. What is the Flow Index at the lower oxygen concentration? (1) With 11 ppm oxygen in the water supply, there is 6 ppm available oxygen, since the minimum acceptable level for trout is 5 ppm (ll ppm — 5 ppm). (2) With 8 ppm oxygen in the water supply, there is 3 ppm available ox- ygen (8 ppm — 5 ppm). (3) The reduction in Flow Index is the available oxygen at 8 ppm divid- ed by the available oxygen at 11 ppm or a 0.5 reduction (3 ^ 6). (4) The Flow Index will be 0.75 at the lower oxygen concentration (1.5x0.5). Table 9 presents dissolved oxygen concentrations in water at various tem- peratures and elevations above sea level. The percent saturation can be cal- culated, once the dissolved oxygen in parts per million is determined for the water supply. Many hatcheries reuse water through a series of raceways or ponds and the dissolved oxygen concentration may decrease as the water flows through the series. As a result, if aeration does not restore the used oxygen to the original concentration, the carrying capacity will decrease through a series of raceways somewhat proportional to the oxygen decrease. The car- rying capacity or Flow Index of succeeding raceways in the series can be calculated by determining the percent decrease in oxygen saturation in the water flow, but only down to the minimum acceptable oxygen concentration for the fish species. Calculations of rearing unit loadings should be based on the final weights and sizes anticipated when the fish are to be harvested or loadings hatchery operations 71 Table 9. dissolved oxygen in parts per million for fresh water in equili- brium WITH air. (SOURCE: LEITRITZ AND LEWIS 1976.) TEMPER- ELEVATION IN FEET ATURE ("F) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 40 13.0 12.5 12.1 11.6 11.2 10.8 10.4 10.0 9.6 9.3 9.0 45 12.1 11.7 11.2 10.8 10.5 10.1 9.7 9.3 9.0 8.7 8.4 46 11. ;» 11..') 11.1 10.7 10.3 9.9 9.6 9.2 8.9 8.() 8.3 47 n.8 11.3 10.9 10.5 10.2 9.8 9.4 9.1 8.8 8.5 8.2 48 11. (i 11.2 10.8 10.4 10.0 9.7 9.3 9.0 8.7 8.3 8.0 49 11.5 11.1 10.6 10.3 i).9 9.5 9.2 8.9 8.6 8.2 7.9 50 11.3 10.9 1U.5 10.1 9.8 9.4 9.1 8.7 8.4 8.1 7.8 51 11.2 10.8 10.4 10.0 9.7 9.3 9.0 8.6 8.3 8.0 7.7 52 11.0 10.6 10.2 9.9 9.5 9.2 8.9 8.5 8.2 7.9 7.6 53 10.9 10.5 10.1 9.8 9.4 9.1 8.7 8.4 8.1 7.8 7..") 54 lO.K 10.4 10.0 9.6 9.3 9.0 8.6 8.3 8.0 7.7 7.4 55 10.() 10.3 9.9 9.5 9.2 8.9 8.5 8.2 7.9 7.6 7.3 60 10.0 9.6 9.3 8.9 8.6 8.3 8.0 7.7 7.4 7.1 6.8 65 9.4 9.1 8.8 8.4 8.1 7.8 7.5 7.2 7.0 6.7 6.4 70 9.0 8.7 8.4 8.0 7.8 7.4 7.2 6.9 6.7 6.4 6.1 75 8.6 8.3 8.0 7.7 7.4 7.1 6.8 6.5 6.3 6.1 5.8 reduced. In this way, maximum rearing unit and water flow requirements will be delineated and frequent adjusting of water flows or fish transfers can be avoided. Generally, these methods are limited to intensive culture of fish in situa- tions where oxygen availability is regulated by the inflowing water. In ex- tensive culture systems involving large ponds, oxygen availability depends to a greater extent on oxygen replacement through the surface area of the water. Water inflow in such situations is not as significant as pond surface area and water volume in determining carrying capacity. Estimates of oxygen consumption under intensive cultural conditions have been determined for channel catfish. Oxygen consumption rates de- cline as the available oxygen decreases, and there is a straight- line (semi- log) relationship between fish size and oxygen consumption; smaller fish require more oxygen per unit size than larger fish (Figure 27). The data in Figure 27 can be used to estimate the carrying capacity for channel catfish if the available oxygen in a rearing unit is determined. Ox- ygen consumption will change proportionately as the water temperature in- creases or decreases. DENSITY INDEX Carrying capacity has been discussed in relation to water inflow or, more specifically, oxygen availability. What affect does density, as pounds of fish 72 FISH HATCHERY MANAGEMENT >- < Q X to C/5 OQ O O 4.5 4.0 3.5 3.0 2.5 2.0 1.5 o CO 0.51 _L _L 4 5 6 LENGTH IN INCHES 10 Figure 27. Oxygen consumption of well-fed and fasted channel catfish at 79°F water temperature. Environmental oxygen levels were 6-7 ppm. (Modified from Andrews and Matsuda 1975.) per cubic foot of rearing space, have on carrying capacity? Economic con- siderations dictate that the loading density be maintained as high as is practical. However, a reduction in density of fish has been reported by some fish culturists to result in better quality fish, even though there was no apparent environmental stress in their original crowded situation. Most carrying capacity tables are based on the maximum fish load possi- ble without excessive dissolved oxygen depletion, and ignore the pathogen load of the water supply. It is known that in steelhead rearing ponds, parasites apparently cannot be controlled by formalin treatments if the loading exceeds seven to eight pounds of fish per gallon of water per minute at 60-70°F. Carrying capacities that include disease considerations and are conducive to optimum health of spring chinook and coho salmon are shown for standard 20 x 80- foot raceways in Table 10. This information supports the principle that as fish size increases, fish loading can be increased proportionally. An example of this principle is shown HATCHERY OPERATIONS 73 in Figure 28. There is no effect on the rate of length increase or food conversion of rainbow trout as fish density increases from less than I to 5.6 pounds per cubic foot. A rule of thumb that can be used to avoid undue crowding is to hold trout at densities in pounds per cubic foot no greater than 0.5 their length in inches (i.e., 2-inch fish at one pound per cubic foot, 4-inch fish at two pounds per cubic foot, etc.). A density index can be established that is the proportion of the fish length used in determining the pounds of fish to be held per cubic foot of rearing space. Fish held at densities equal to one- half 00 cc CO CD CO o CJ) co' LlJ 53 C3 ^/ / / / /■ ^y V .^v ^ 5^ / X' y .-'\ r ^ y \ CONVERSION j_ _L 8 12 16 20 BIWEEKLY GROWTH PERIODS 24 Figure 28. Relationship of cumulative length increase, food conversion, and pounds per cubic foot (ft ) of rainbow trout reared in aluminum troughs for 10 months. (Source: Piper 1972.) 74 fish hatchery management Table 10. recommended hatchery pond loadings (pounds of fish per gal- lon PER MINUTE INFLOW), BASED ON DISEASE CONSIDERATIONS, FOR CHINOOK AND COHO SALMON HELD IN 80 x 2()-FOOT PONDS. THE VALUES REPRESENT FINAL POND OR RACEWAY LOADINGS AT TIME OF RELEASE OR HARVEST FOR FISH SIZES OF 1000 FISH PER POUND AND LARGER. LOADINGS SHOULD NOT EXCEED THE TABLE VALUE BEFORE TIME OF RELEASE. INFORMATION IS NOT AVAILABLE FOR OTHER TEMPERATURES, SIZES, OR SPECIES OF FISH. (SOURCE: WEDEMEYER AND WOOD 1974.) WATER FISH SIZE (NUMBER PER POUND) TEMPERA- TURES (°F) 1,000 500 100 50 33 25 15 Coho salmon 38 3.5 5.0 8.0 11.0 15.0 20.0 25.0 48 2.7 4.0 6.0 10.0 14.0 16.0 18.0 58 2.2 3.0 4.5 7.0 10.0 12.0 15.0 63 2.0 3.5 5.0 7.0 9.0 10.0 68 1.5 2.0 3.0 3.0 4.0 Fall and spring chinook salmon 38 3.0 4.0 6.0 8.0 11.0 12.0 13.0 48 2.5 3.0 5.0 6.5 9.0 10.0 11.0 58 2.0 2.2 3.5 4.5 6.0 7.5 9.0 63 1.2 3.0 3.5 4.0 5.0 5.5 their length have a density index equal to 0.5. A useful formula to avoid overcrowding raceways is: W = D X FXZ. Where W = Permissible weight of fish D = Density index (0.5 suggested for trout) V = Volume of raceway in cubic feet L = Fish length in inches Raceway or pond volume requirements can be calculated with the for- mula: V=W^{D XL). Volumes of circular tanks can be determined from Table C- 1 in Appendix C. This concept of space requirement assumes that the Density Index remains constant as the fish increase in length. In reality, larger fish may be able to tolerate higher densities in proportion to their length. This method has proved to be a practical hatchery management tool, nonethe- less, and can be used with any species of fish for which a Density Index has been determined. HATCHERY OPERATIONS 75 Warmwater Fish Rearing Densities Channel catfish have been reared at densities of up to eight pounds per cu- bic foot of water. Stocking density and water turnover both had substantial effects on growth and food conversion. Reduced growth due to the increase in stocking density was largely compensated by increased water exchange, and growth rate data indicated that production of over 20 pounds per cu- bic foot of water was possible in a 365-day period. High-density culture of catfish in tanks or raceways can be economical if suitable environmental conditions and temperatures are maintained. Fish weight gain, food utilization, and survival may decrease as fish den- sity increases, but faster water exchanges (inflow) will benefit high stocking densities. The best stocking densities and water exchange rates will take into consideration the various growth parameters as they affect the economics of culturing channel catfish. Stocking densities between five and 10 fish per cubic foot have been suggested as feasible and production can be increased to higher densities by increasing the oxygen content with aeration, if low oxygen concentration is the limiting factor. Acceptable stocking densities for warmwater fish are related to the type of culture employed (intensive or extensive) and the species cultured. The appropriate density is influenced by such factors as desired growth rate, carrying capacity of the rearing facility, and environmental conditions. Most warmwater fish, other than catfish, normally are cultured extensively. The following paragraphs cover representative species of the major groups of commonly cultured warmwater and coolwater fishes. Stocking rates for related species can be estimated from these examples. LARGEMOUTH BASS Production methods used for largemouth bass are designed to supply 2- inch fingerlings. Fry are stocked in prepared rearing ponds at rates varying from 50,000 to 75,000 per acre. If a fingerling size larger than 2 inches is desired, the number of fry should be reduced. Normal production of small bass ranges from 30 to 150 pounds per acre depending on the size fish reared, the pro- ductivity of the rearing pond, and the extent to which natural food has been consumed and depleted. The length of time required for the transferred fry to grow to a harvest- able size depends mainly upon the prevailing water temperature and the available food supply. Normally, it is 20-30 days in southeastern United States at a temperature range of 65-75°F. A survival rate of 75 to 90% is acceptable. A higher survival suggests that the number of fry stocked was estimated inaccurately. Less than 75% survival indicates a need for 7fi FISH HATCHERY MANAGEMENT improved enumeration technique, better food production, or control of disease, predators, or competitors. Production of 3- to 6-inch bass fingerlings requires careful attention to size uniformity of the fry stocked. The number of fry stocked is reduced by 75 to 90"(i below that used for 2-inch bass production. Growth past a size of 2 inches must be achieved mainly on a diet of immature insects, mainly midges. If a size larger than 4 inches is needed, it will be necessary to pro- vide a forage fish for the bass. There are no standard procedures for this, but one method is to stock 17-inch bass at a rate of 1,000 per acre into a pond in which fathead minnows had been stocked at a rate of 2,000 per acre 3 or 4 weeks previously. The latter pond should have been fertilized earlier with organic fertilizer and superphosphate so that ample zooplank- ton will have developed to support the minnows. The minnows are allowed to grow and reproduce to provide feed for the bass when they are stocked. If weekly seine checks show that the bass are depleting the supply of forage fish, additional minnows must be added to the pond. Variable growth among bass fingerlings is common but if some fingerlings become too much larger than others, cannibalism can cause heavy losses. If this occurs, the pond must be drained and the fingerlings graded. BLUEGILL Numerically, bluegills and redear sunfish are the most important of the cul- tured warmwater fishes. Generally, spawning and rearing occurs in the same pond, although some fish culturists transfer fry to rearing ponds for one reason or another. In previously prepared ponds, broodstock bluegills 1 to 3 years old are stocked at a rate of 30 to 40 pairs per acre. Spawning- rearing ponds for bluegills can be stocked in the winter, spring, or early summer. About 60 days are required to produce harvestable-size fingerlings under average conditions. CHANNEL CATFISH Channel catfish reared in ponds are stocked at a rate of 100,000 to 200,000 fry per acre. At these rates, survival should be 80%, and 3- to 4- inch finger- lings can be produced in 80 to 120 days if there is adequate supplemental feeding. Stocking at a higher rate reduces the growth rate of fingerlings. A stocking rate of 40,000 to 50,000 per acre yields 4- to 6- inch fingerlings in 80-120 days if growth is optimum. Although channel catfish can be reared on natural food, production is low compared to that obtained with supplemental feeding. A well- fertilized pond should produce 300-400 pounds of fingerling fish per acre, with no HATCHERY OPERATIONS 77 supplemental feeding. Up to 2,000 pounds or more of fingerling fish per acre can be reared with supplemental feeding. If fish larger than 4 inches are desired, stocking rates must be reduced. Experimental evidence suggests that 1,500, 3- to 6-inch fingerlings per acre will produce 1- pound fish in 180 days. HIGH-DENSITY CATFISH CULTURE Specialized catfish culture systems have received much publicity in recent years, and several high-density methods are currently under investigation. These include the use of cages; earthen, metal, or concrete raceways; vari- ous tank systems; and recirculation systems. High-density fish culture demands not only highly skilled and knowledgeable management but also requires provision of adequate amounts of oxygen, removal of wastes, and a complete high-quality diet. The methods used for calculating carrying capacity in salmonid hatcheries can readily be used for intensive culture of catfish. STRIPED BASS At present, most striped bass rearing stations receive fry from outside sources. Eggs are collected and usually hatched at facilities located near natural spawning sites on the Atlantic coast. Fry are transferred to the hatchery at 1 to 5 days of age. There they are either held in special tanks or stocked in ponds for rearing, depending on the age of the fry and whether or not they have sufficiently developed mouth parts to allow feeding. Earthen ponds are fertilized before stocking to produce an abundance of zooplankton. In these prepared ponds, striped bass fry are stocked at a rate of 75,000 to 125,000 per acre. A stocking density of 100,000 fry per acre, under normal growing conditions, yields 2-inch fingerlings in 30 to 45 days. Survival is very erratic with this species, and may vary from 0 to 100% among ponds at the same hatchery. As with most pond-cultured fish, the growth rate of striped bass increases as the stocking density decreases. If a 3- inch fingerling is needed, the stocking density should be reduced to 60,000 to 70,000 fry per acre. Culture of striped bass larger than 3 inches usually requires feeding for- mulated feeds. Striped bass larger than 2 inches readily adapt to formulat- ed feeds, and once this has taken place most of the procedures of trout cul- ture can be applied. NORTHERN PIKE AND WALLEYE These coolwater species represent a transition between coldwater and warmwater cultural methods. A combination of extensive and intensive 78 FISH HATCHERY MANAGEMENT culture is applied. Fry are usually stocked in earthen ponds that have been prepared to provide an abundance of zooplankton. Fry are stocked at den- sities of 50,000 to 70,000 per acre to produce 2- inch fingerlings in 30 to 40 days. Because of the aggressive feeding behavior of these species, especially northern pike, care must be taken not to let the zooplankton decline or cannibalism will occur and survival will be low. At a size of 2 to 3 inches these fish change from a diet of zooplankton and insect larvae to one predominantly of fish. At this stage, the fingerlings usually are harvested and distributed. If fish larger than 2 to 3 inches are desired, the fingerlings can be restocked into ponds supplied with a forage fish. Stocking rates do not normally exceed 20,000 per acre, and generally average about 10,000 to 15,000. As long as forage fish are present in the pond, northern pike and walleyes can be reared to any size desired. As the fish become larger, they consume more and larger forage fish. Northern pike and walleyes are stocked at lower densities if they are to be raised to larger sizes. Stocking densities of 10,000 to 20,000 fingerlings per acre are used to rear 4- to 6- inch fingerlings; 5,000 to 10,000 per acre for 6- to 8-inch fish; and usually less than 4,000 per acre for fish 8 inches or larger. This method of calculating carrying capacities of ponds or raceways ig- nores the effects of accumulative metabolic wastes. Where water is reused through a series of raceways, the Flow Index would remain fairly constant, but metabolic products would accumulate. Inventory Methods The efficient operation of a fish hatchery depends on an accurately main- tained inventory for proper management. Whether weight data are applied directly to the management of fish in the rearing units or used in an ad- ministrative capacity, they are the criteria upon which most hatchery prac- tices are based. Hatchery procedures that are based upon fish weight include feed calcu- lations, determination of number per pound and fish length, loadings of distribution trucks for stocking, calculations of carrying capacities in rear- ing units, and drug applications for disease control. Administrative functions based upon weight of fish include preparation of annual reports, budgeting, estimating production capability of rearing fa- cilities, recording monthly production records, feed contracting, and plan- ning for distribution (stocking). Some managers inventory every two or three months to keep their pro- duction records accurate; others use past record data to project growth for several months and obtain a reasonable degree of accuracy. An inventory is essential after production fish have been thinned and graded, and one HATCHERY OPERATIONS 79 should be made whenever necessary to assure that records provide accurate data. In any inventory, it is imperative that fish weights be as accurate as possible. INTENSIVE CULTURE Fish can be weighed either by the wet or dry method. The wet method in- volves weighing the fish in a container of water that has been preweighed on the scale. Care must be exercised that water is not added to the preweighed container, nor should water be splashed from it during weigh- ing of the fish. This method is generally used with small fish. Dry weigh- ing is a popular method of inventorying larger fish. The dip net is hung from a hook at the bottom of a suspended dial scale. The scale should be equipped with an adjusting screw on the bottom, so the weight of the net can be compensated for. Dry weighing eliminates some fish handling and, with a little practice, its accuracy is equal to that of wet weighing. The most common ways to determine inventory weights are the sample- count, total-weight, and pilot-tank methods. In the sample-counting method, the total number of fish is obtained ini- tially by counting and weighing the entire lot. In subsequent inventories, a sample of fish is counted and weighed and either the number per pound or weight per thousand is calculated (Figure 29). To calculate the number per pound, divide the number of fish in the sample by the sample weight. To calculate the weight per thousand, divide the sample weight by the number of fish (expressed in thousands). The total weight of fish in the lot then is estimated either by dividing the original total number of fish (adjusted for recorded mortality) by the number per pound or by multiplying it (now expressed in thousands) by the weight per thousand. This method can be inaccurate, but often it is the only practical means of estimating the weight of a group of fish. To assure the best possible accuracy the following steps should be followed: (1) The fish should be crowded and sampled while in motion. (2) Once a sample of fish is taken in the dip net, the entire sample should be weighed. This is particularly true if the fish vary in size. The practice of weighing an entire net full of fish will obtain more representa- tive data than that of weighing preset amounts (such as 5 or 15 pounds). Light net loads should be taken to prevent injury to the fish or smothering them. (3) When a fish is removed from water it retains a surface film of water. For small fish, the weight of the water film makes up a larger part of the observed weight than it does for larger fish. The netful of fish should be carefully drained and the net bottom wiped several times before the fish are weighed. 80 FISH HATCHERY MANAGEMENT Figure 29. Muskellunge fry being sample-counted for inventory. (Courtesy Wisconsin Department of Natural Resources.) (4) Several samples (at least five) should be taken. If the calculated number of fish per pound (or weight per 1,000) varies considerably among samples, more samples should be taken until there is some consistency in the calculation. Then the sample values can be averaged and applied to the total lot; all samples should be included in the average. Alternatively, the counts and weights can be summed over all the samples, and an overall number per pound computed. Larger samples are required for large fish. Even with care, the sample-count method can be as high as 15-20% inac- curate. Some fishery workers feel it is necessary to weigh as much as 17% of a population to gain an accuracy of 5-10%. Hewitt (l948) developed a quarter-sampler that improved the accuracy of the sample count method (Figure 30). In the total-weight method, as the name implies, all of the fish in a lot are weighed, thus sampling error is avoided. Initial sample counting must be conducted during the first weighing to determine the number of fish in the lot, but this is done when the fish are small and more uniform in size. This method involves more work in handling the fish, but is the most accu- rate method of inventorying fish. HATCHERY OPERATIONS 81 The pilot- unit method utilizes a tank or raceway of fish maintained to correspond to other tanks or raceways of the same type. The pilot unit is supplied with the same water source and flow, and the fish are fed the same type and amount of food per unit of body weight. All the fish reared in the pilot unit are weighed and the gain in weight is used to estimate the fish weight in the other rearing units. This method is more accurate than sample counting for fish up to six inches long. EXTENSIVE CULTURE Fish grown in ponds are relatively inaccessible and difficult to inventory accurately before they finally are harvested. Pond fish still are sampled fre- quently, as they are in raceway culture, but the value of such sampling is Figure 30. A quarter- sampler can be used to accurately estimate the number of fish per pound or weight per thousand fish, (l) A framed net with four remov- able pockets in the bottom is designed to fit snugly in a large tub of water. (2) Several netfuls of fish are put in the tub and when the frame is removed the fish are divided into four uniform samples. (3) Only one-quarter of the" fish are actu- ally used in the sampling. The fish are counted and then weighed. (4) A modi- fied frame design has one of the net pockets closed (arrow) and the other three open. As the frame is lifted out of the tub the fish in the closed pocket are retained for counting. It is felt that a sample taken in this manner, from several netfuls of fish, reduces bias in sampling. (FWS photos.) 82 FISH HATCHERY MANAGEMENT Figure 31. Pond fish being sampled with a lift net. The fish are attracted to the area with bait. as much to determine the condition and health of the fish, to adjust feed applications, and to estimate harvest dates, as it is to estimate growth and survival. Usually, it is impractical to concentrate all fish in a pond to- gether, so sampling is done on a small fraction of the population. Numeri- cal calculations based on such small samples may be biased and unreliable except as general guidelines. One way to sample pond fish is to attract them with bait and then cap- ture them, as with a prelaid lift net (Figure 3l). The problem with this technique is that fish form dominance hierarchies, and the baited area quickly becomes dominated by the larger and more vigorous individuals. This will bias the sample. Most pond samples are taken with seine nets. Such samples can be ex- trapolated to the whole pond if the seine sweeps a known area, if few fish escape the net, and if the population is distributed uniformly throughout the pond. The area swept by the net can be calculated with little difficulty; HATCHERY OPERATIONS 83 however, fish over 3 inches long can outrun the pulled seine, and are likely to escape, leaving a nonrepresentative sample. This problem can be partial- ly overcome by setting the net across, or pulling it into, a corner of the pond instead of pulling it to a straight shore. The uniformity of fish distri- bution is the most difficult aspect to determine. Many species form aggre- gations for one reason or another. A seine might net such a cluster or the relatively empty space between them. It helps to sample several areas of the pond and to average the results, although this is time-consuming, and seines rarely reach the pond center in any case. Fish can be concentrated for sampling if the pond is drawn down. This wastes time — it can take two or three days to empty a pond of several acres — and a lot of water. It also can waste a lot of natural food production in the pond. Unless fish have to be concentrated for some other purpose, such as for the application of disease-control chemicals, ponds should not be drawn down for sampling purposes. In summary, pond fish should be sampled regularly, but the resulting in- formation should be used for production calculations only with caution. Fish Grading Fish grading — sorting by fish length — makes possible the stocking of uni- formly sized fish if this is necessary for fishery management programs. Also, it reduces cannibalism in certain species of fish; some, such as striped bass and northern pike, must be graded as often as every three weeks to prevent cannibalism. Grading also permits more accurate sample counting and in- ventory estimates by eliminating some of the variation in fish size. An ad- ditional reason for grading salmon and steelhead is to separate smaller fish for special treatment so that more of the fish can be raised to smolt size by a specified time for management purposes (Figure 32). In trout culture, good feeding procedure that provides access to food by less aggressive fish can minimize the need for grading. However, grading of fish to increase hatchery production by allowing the smaller fish to increase their growth rate is questionable. Only a few studies have demonstrated that dominance hierarches suppress growth of some fish; in most cases, segregation of small fish has not induced faster growth or better food utili- zation. In any fish population there are fish that are small because of their genetic background and they will remain smaller regardless "of opportuni- ties given them to grow faster. In warmwater culture — and extensive culture generally — fish usually cannot be graded until they are harvested. Pond-grown fish can vary great- ly in size, and they should be graded into inch-groups before they are dis- tributed. Products of warmwater culture often are sold in small lots to 84 FISH HATCHERY MANAGEMENT several buyers, who find them more attractive if the fish are of uniform size within each lot. A number of commercial graders are available. Mixed sizes of fish may require grading through more than one size of grader. Floating grading boxes with panels of metal bars on the sides and bottom are commonly used in fish hatcheries. Spacing between the bars determines the size of fish that are retained; fish small enough to pass between the bars escape. The quantity of fish in the grader at any one time should not exceed five pounds per cubic foot of grader capacity. Small fish can be driven from the grader by splashing the water inside the grader with a rocking motion. Recommended grader sizes for such warmwater fish as minnows and channel catfish are as follows: Minnows Channel catfish Spacing Length Spacing Length between offish between offish bars held bars held (inches) (inches) (inches) (inches) ±1 u 27 3 M I (i4 (>4 4 11 (i4 4 11 64 2 40 (i4 5 ii (i4 21 4 Al 1)4 6 Al M 21 2 11 fi4 7 ill (i4 21 4 (i4 8 A lT;-inch grader will retain j-1-pound channel catfish. Catfish pass most readily through the bottom of a grader and minnows through the sides. Fish Handling and Harvesting Handling of fish should be kept to a minimum to avoid injury and stress that can lead to disease or death. Losses from handling can be substantial, but they do not always occur immediately and can go unnoticed after the fish have been stocked in natural waters. An adequate supply of oxygen must be provided in the raceway or pond during harvest, and during transit in containers. Silt and waste material such as feed and feces in the water should be avoided or kept to a minimum. Overloading nets or containers will abrade the skin of the fish. Extremes in water temperature should be avoided in the hauling containers and between rearing units. Sudden changes in water temperature of 6°F or HATCHERY OPERATIONS 85 Figure 32. A mechanical crowder used in concrete rearing ponds with an adjust- able Wilco grader mounted on the crowder frame. (Courtesy California Department of Fish and Game.) greater have adverse effects on most fishes. The use of l-3'/^i saline solution for handling and moving fish has been recommended by some fishery workers to reduce handling stress. Containers should be full of water. If the water cannot slosh, fish will not be thrown against the sides of the container. A dip net and tub can be used to avoid physical damage when small poundages of fish are moved. Large- meshed nets should be avoided, partic- ularly when scaled fish are involved. Nets used for catfish commonly are treated with asphaltum or similar substances to prevent damage due to spine entanglement. Many warmwater fish hatcheries comprise a number of earthen ponds that normally are harvested through a combination of draining and seining (Figure 33). When large poundages of fish are present, a substantial portion is removed by seining before the pond is lowered. The remainder are then easily harvested from collection basins (Figure 34). Small fihgerlings are harvested by lowering the pond water level as rapidly as possible without stranding the fish or catching them on the outlet screen. If the contents of a pond cannot be removed in one day, the pond should be partially refilled for overnight holding. Holding a partially har- vested pond at a low level for long periods of time should be avoided 86 FISH HATCHERY MANAGEMENT Figure 33. Marketable size catfish being graded and harvested from a large earthen pond (Fish Farming Experimental Station, Stuttgart, Arkansas). because this increases loss to predators and the possibility of disease. Crowding and the lack of food also will reduce the ability of small fish to withstand handling stress. A fresh supply of water should be provided while the fish are confined to the collection basin. Although harvesting the fish crop by draining the pond has the major advantage of removing the entire crop in a relatively short time, trapping is another popular harvesting technique. The advantages associated with trap- ping include better overall condition of the fish, because they are collected in silt-free water; reduced injury, because the fish are handled in small numbers; avoidance of pond draining; successful harvesting in vegetated ponds; avoidance of nuisance organisms such as tadpoles and crayfish; and reduced labor, as one person can operate a trap successfully. The major disadvantage to trapping is it does not supply a reliably large specified number of fish on a given date. The most widely used trap on warmwater fish hatcheries is the V-trap (Figure 35). Successful trapping requires knowledge of the habits of the fish and proper positioning of the device. The trap usually is used in com- bination with pond draining; it is positioned in front of the outlet screens and held away from them, against the water current, by legs or some other means. The trap is constructed so it floats with about 10% above the water HATCHERY OPERATIONS 87 surface and 90% below. As the pond is drained the trap simply falls with the water level. Fish are attracted to the outlet screen for a number of rea- sons, the two main ones being the water current and the abundance of food organisms that are funneled there. Some species of fish are attracted to fresh cool water, and a small stream of this should be introduced near the trapping area if possible. The fish attracted to the area have to swim against the outgoing current to keep from being pulled against the outlet screen. They rest behind a glass plate that shields them from the current; following this glass they come into the trap, from which they can periodi- cally be harvested with a small net. The trap is used in another manner for harvesting small fish. The advanced fry and early fingerlings of many species, such as largemouth bass, smallmouth bass, and walleye run the shoreline of ponds in schools of varying numbers. To collect them, the trap is fixed far enough out in the pond that the fry swim between it and the shore. A wire screen lead run- ning from the mouth of the trap to the shore, and extending from the water surface to the pond bottom, intercepts the fish. As they attempt to get around the lead, the fish follow it toward deep water and into the trap. Four such traps set around a pond have caught up to 80% of the available largemouth bass fry. Figure 34. Removing fish from a collection basin in an earthen pond. 88 FISH HATCHERY MANAGEMENT Figure 35. Diagram of a V-trap. Fish follow the wire screen into the V and enter the cage, where it is difficult for them to find a way back out through the narrow opening in the V. Physical characteristics of earthen ponds play an important part in the efficient harvest of fish. Removal of all stumps, roots, and logs is necessary for harvesting with seines. The pond bottom should be relatively smooth to provide adequate and complete drainage. Low areas that will not drain to- wards the collection basin should be avoided. Rearing Unit Management Sanitation Sanitation is an important phase of any animal husbandry. A number of undesirable situations can arise when waste feed and fecal material collect in rearing units. If fish feed falls into waste material on the pond or race- way bottoms, fish will generally ignore it and it will be wasted. Excessive feces and waste food harbor disease organisms and can accumulate in the mucus of the gills, especially during disease outbreaks. Disease treatment is also difficult in filthy rearing units because treatment chemicals may react with the organic matter, reducing the potency of the chemical. The waste material may become stirred up as the chemical is mixed in the water; this can be hazardous to the gills of the fish. Tanks, troughs, and raceways must be cleaned frequently, whatever species — cold-, cool-, or warm- water — is grown in them. In large earthen ponds, accumulated waste may reduce the oxygen con- tent of the water. This can become a severe problem during periods of re- duced water flow in the warm summer months. HATCHERY OPERATIONS 89 Most fish diseases are water-borne and are readily transferred from one rearing unit to another by equipment such as brushes, seines, and dip nets. All equipment used in handling and moving fish can be easily sanitized by dipping and rinsing it in a disinfectant such as Roccal, Hyamine, or so- dium hypochlorite. Solutions of these chemicals can be placed in containers at various locations around the hatchery. Separate equipment should be provided for handling small fish in the hatchery building and should not be used with larger fish in the outside rearing units. Detailed procedures for decontaminating hatchery facilities and equipment are presented in Chapter 5. Dead and dying fish are a potential source of disease organisms and should be removed daily. Empty rearing units should be cleaned and treated with a strong solution of disinfectant and then flushed before being restocked. Direct sunshine and drying also can help sanitize rearing units. If possible, ponds and raceways should be allowed to air-dry in the sun for several weeks before they are restocked. To prevent long-term buildup of organic matter, ponds typically are dried and left fallow for two to five months after each harvest. Many times, the pond bottoms are disked, allowing the organic matter to be oxidized more quickly. After the pond soil has been sun-baked, remaining organic material will not be released easily when the pond is reflooded. Disinfection of warmwater fish ponds is a process by which one or more undesirable forms of plant and animal life are eliminated from the environ- ment. It may be desirable for several reasons: disease control; elimination of animal competitors; destruction of aquatic weeds, among others. Disin- fection may be either partial or complete, according to the degree to which all life is eliminated. It is impractical, if not impossible, to achieve com- plete disinfection of eathern ponds. Disinfection of ponds with lime is a common practice, especially in Eu- rope. This is particularly useful for killing fish parasites and their inter- mediate hosts (mainly snails), although it will also destroy insects, other in- vertebrates, and shallow rooted water plants for a few weeks. Calcium ox- ide or calcium hydroxide are recommended; the latter is easier to obtain and less caustic. Lime may be applied either to a full or dewatered pond (so long as the bottom is wet); in either case, the lime penetrates the pond soil less than an inch. It is most important that the lime be applied evenly across the pond, and mechanized application is better for this than manual distribution. Except for the smallest ponds, equipment for applying lime must be floated. This means that at least some water must be in the ponds, even though lime is most effective when spread over dewatered soils. Lime makes water alkaline. If the pH is raised above 10, much aquatic life will be killed; above 11, nearly all of it. Application rates of 1,000 to 2,500 pounds of lime per acre will achieve such high pH values. Appropri- ate rates within this range depend on the water chemistry of particular 90 FISH HATCHERY MANAGEMENT ponds, especially on how well the water is naturally buffered with bicar- bonates. Agricultural extension agents and the Soil Conservation Service can provide detailed advice about water chemistry and lime applications. Normally, a limed pond will be safe for stocking within 10 days after treatment, or when the pH has declined to 9.5. However, a normal food supply will not be present until three to four weeks later. Chlorine has been used by fish culturists as a disinfecting agent. Ten parts per million chlorine applied for 24 hours is sufficient to kill all harm- ful bacteria and other organisms. Several forms of chlorine can be obtained. Calcium hypochlorite is the most convenient to apply. It contains 70% chlorine and is readily available. It can be applied to either flooded or dewatered ponds. A 600 parts per million solution of Hyamine 1622, Roccal, or Hyamine 3500 may be used for disinfecting ponds. Twice this strength may be used to disinfect equipment and tools. The strength of the disinfecting solution is based on the active ingredient as purchased. Water Supply Structures The water supply for a fish hatchery should be relatively silt-free and de- void of vegetation that may clog intake structures. For this reason, an earthen ditch is not recommended for conveying water because of algal growth and the possibility of aquatic vegetation becoming established. At hatcheries with a silt problem, a filter or settling basin may be necessary. The water intake structure on a stream should include a barred grill to ex- clude logs and large debris and a revolving screen to remove smaller debris and stop fish from entering the hatchery. There are a vast number of methods used to adjust and regulate water flows through fish rearing units. Some of these include damboards, head- boxes with adjustable overflows, headgates, headboards with holes bored through them, molasses valves, faucet- type valves, and flow regulators. Each type has advantages. Generally, damboards and headboxes will not clog, and they provide a safe means of regulating water flows. They are particularly useful with gravity water supplies, but they are not easily adjusted to specific water flows. Valves and flow regulators are readily adjustable to specific water flows and are preferred with pressurized water supplies, but are prone to clogging if any solid material such as algae or leaves is present in the water. Water flows can be measured with a pail or tub of known volume and a stop watch when valves or gates are used to regulate the water flow. Dam boards can be modified to serve as a rectangular weir for measuring flows (Appendix D). HATCHERY OPERATIONS 91 Screens Various materials have been used to construct pond or raceway screens. Door screening and galvanized hardware cloth can be used, but clog easily. Wire screening fatigues and breaks after much brushing and must be re- placed periodically. Perforated sheet aluminum screens are used commonly in many fish hatcheries today. They can be mounted on wood or metal an- gle frames. Redwood frames are easier than metal ones to fit to irregular concrete slots in raceway walls. Perforated aluminum sheets generally can be obtained from any sheet metal company. Some suggested sheet thicknesses are 16 gauge for large screens (ponds, raceways: 30x96 inches) and 18-20 gauge for small screens (troughs: 7 x 13 inches). Round holes and oblong slots are available in a number of sizes (Figure 36). Horizontal oblong slots are preferred by some fish culturists who feel they are easier to clean and do not clog as readily as round holes. They can be used with the following fish sizes: Slot size Fish size _\_ 111 j_ s \_ 4 J_ 2 Perforated aluminum center screens can also be used in circular rearing tanks, but only the bottom 2-3 inches of the cylinder should be perforated. These provide some self-cleaning action for the tank and prevent short- circuiting of water flows by drawing waste water off the bottom of the tank. Pond Management PRESEASON PREPARATION Proper management of earthen ponds begins before water is introduced into them. During the winter it is advisable to dry and disk ponds to pro- mote aerobic breakdown of the nutrient-rich sediments. Although some nu- trients are desirable for fingerling culture, because they promote algal growth on which zooplankton graze, an overabundance tends to produce more undesirable blue-green and filamentous algae. Relatively new ponds with little buildup of organic material, or those with sandy, permeable bot- toms that allow nutrients to escape to the groundwater, are less likely than older or more impermeable ponds to require drying and disking. They may xi fry up to 1,000/lb XT 1,000-200/lb xi 200-30/lb x| 30/lb and larger 92 FISH HATCHERY MANAGEMENT Figure 36. Perforated aluminum screens showing (l) round holes, (2) staggered slots, and (3) nonstaggered slots. (Courtesy California Department of Fish and Game.) actually leak if the bottom is disturbed, and it may be necessary to com- pact their bottom with a sheepsfoot roller, rather than to disk them. If a pond is to remain dry for several months it should be seeded around the edges with rye grass (8-10 pounds per acre). This cover prevents ero- sion of pond dikes and it can be flooded in the spring to serve as a source of organic fertilizer. The grass should be cut and partially dried before the pond is reflooded, or its rapid decay in water may deplete dissolved oxygen. Application of 1,000 pounds per acre of agricultural lime during the fal- lowing period, followed by disking, may improve the buffering capacity of HATCHERY OPERATIONS 93 a soft-water pond. Fertilizers are often spread on the pond bottom prior to filling, and nuisance vegetation may also be sprayed at this time. WILD-FISH CONTROL Wild fish must be kept from ponds when they are filled, as they compete with cultured species for feed, complicate sorting during harvest, may in- troduce diseases, or confound hybridization studies. Proper construction of the water system and filtration of inlet water can prevent the entrance of wild fish. A sock filter is made by sewing two pieces of 3- foot- wide material into a 12-foot-long cylinder, one end of which is tied closed and the other end clamped to the inlet pipe (Figure 37). It can handle water flows up to 1,000 gallons per minute. This filter should be used only on near-surface discharges, to prevent excessive strain on the screening. A box filter consists of screen fastened to the bottom of a wooden box eight feet long, three feet wide, and two feet deep (Figure 38), and is suit- able for water flows up to 1,000 gallons per minute. The screen bottom is supported by a wooden grid with 1 x 2 foot openings, which prevents ex- cessive stress and stretching. The filter may be mounted in a fixed position or equipped with floats. If the inlet water line is not too high above the pond water level, a floating filter is preferred. This allows the screen to remain submerged, whatever the water level, which reduces damage caused by falling water. If the water supply contains too much mud or debris and cannot be ef- fectively filtered, ponds can be filled and then treated with chemicals to kill wild fish. Rotenone is relatively inexpensive and is registered and la- beled for this purpose. It should be applied to give a concentration of 0.5 to 2.0 parts per million throughout the pond. Rotenone does not always control some fishes, such as bullheads and mosquitofish, and it requires up to two weeks to lose its toxicity in warm water and even longer in cold wa- ter. However, 2 to 2.5 parts per million potassium permanganate (KMn04) can be added to detoxify rotenone. Antimycin A is a selective poison that eliminates scaled fishes in the presence of catfish. It does not kill bullheads, however, which are undesir- able in channel catfish ponds. The chemical varies in activity in relation to water chemistry and temperature; the instructions on the label must be closely followed. Expert advice should be sought in special cases. Chlorine in the form HTH, used at concentrations of 5 parts per million for as little as one hour, will kill most wild species of fish that might enter the pond. Chlorine deteriorates rapidly and usually loses its toxicity after one day at this concentration. Chlorine can be neutralized if need be with sodium thiosulfate. Chlorine is a nonspecific poison, and will kill most of the organisms in the pond, not only fish. 94 FISH HATCHERY MANAGEMENT FERTILIZATION PROCEDURES Fertilization promotes fish production by increasing the quantity and qual- ity of food organisms. Bacteria are important in the release or recycling of nutrients from fertilizers. Once in solution, nutrients stimulate growth and reproduction of algae which, in turn, support populations of zooplankton. PIPE CLAMPS SUPPLY LINE SOCK FILTER, WATER SURFACE LEVEE SARAN SOCK ATTACHED TO THE WATER LINE Figure 37. Sock- type filters with saran screen for pond inflows. (Diagram from Arkansas Game and Fish Commis- sion; photo courtesy of Fish Farming Experimental Station, Stuttgart, Arkansas.) HATCHERY OPERATIONS 95 SUPPLY LINE BOX FILTER 1 H —fEiiiii LEVEE SCREEN BOX FILTER ^s:3i I Figure 38. Box- type filters mounted in fixed positions. (Diagram from Arkansas Game and Fish Commission; photo courtesy of Fish Farming Experimental Station, Stuttgart, Arkansas.) Depending on the fish species, either algae or zooplankton (or both) supply food to fry and fingerlings. A number of factors effect the use of fertilizers, and responses are not predictable under all conditions. Physical influences include area and depth of the pond, amount of shoreline, rate of water exchange, turbidity, 9() FISH HATCHERY MANAGEMENT and water temperature. Biological influences include type of plant and an- imal life present and the food habits of the fish crop. Chemical elements al- ready present in the water supply, composition of the bottom mud, pH, calcium, magnesium, and chemical interactions have significant effects on fertilizer response. Not all ponds should be fertilized; fertilization may be impractical if a pond is too large or too small. Turbid or muddy ponds with light penetra- tion less than six inches should not be fertilized, nor those having a high water exchange rate. Ponds having low water temperatures may not give a good return for the amount of fertilizer applied. If the species of fish being reared is not appreciably benefited by the type of food produced, fertiliza- tion should not be considered. In cold regions where winterkill is common in shallow productive ponds, fertilization may be undesirable. Ponds should be thoroughly inspected before they are fertilized. Includ- ed in the inspection may be a secchi disc reading to determine the water turbidity; close examination for the presence of filamentous algae, rooted aquatic vegetation, and undesirable planktonic forms; oxygen determina- tions on any pond where low oxygen concentrations are suspected, and ob- servation of nesting locations in spawning ponds. Fertilizer to be applied should be weighed or measured on platform or hanging scales, or with precalibrated buckets. It is necessary to calibrate a bucket for each type of fertilizer used, because fertilizers vary considerably in density. Small amounts of fertilizer may be dispensed with a metal scoop, large amounts with a shovel or a mechanical spreader. Distribution of the fertilizer in the pond will vary with wind direction, size of the pond, whether organic or inorganic materials are used, and the particular reason for fertilizing. On a windy day (which should be avoided when possible), fertilizers should be distributed along the windward side of the pond. In general, organic fertilizers (especially heavy forms such as manure) should be given a more uniform distribution than the more solu- ble inorganic ones. However, when insufficient phosphorus is thought to be responsible for plankton die-off, an inorganic phosphate fertilizer should be evenly distributed over most of the pond. Ordinarily, inorganic fertilizer need not be spread over any greater distance than about half the length of the pond on one side. If a pond is being filled or if the water level is being raised, it may be advantageous to apply fertilizer near the inlet pipe. Avoid wading through the pond while spreading fertilizers, if possible. Wading stirs up the bottom mud and some of the fertilizer nutrients, par- ticularly phosphates, may be adsorbed on the mud and temporarily re- moved from circulation. A wader may destroy fish nests, eggs, and fry. Fer- tilizer should not be spread in areas where nesting activity is underway or into schools of fry. Larger fingerlings can swim quickly away from areas of fertilizer concentration. hatchery operations 97 Table 11. composition of several organic fertilizer materials, (source: snow et al. 1964.) CARBO FERTILIZER NITROGEN PHOSPHORUS POTASSIUM PROTEIN HYDRATES Alfalfa hay 2.37 0.24 2.05 14.8 33.5 Grass hay 1.12 0.21 1.20 Peanut vine hay l.(i2 0.13 1.25 lO.I 38.5 Cottonseed meal 36% 5.54 0.83 1.22 34.6 24.5 Cottonseed meal 43"o 7.02 1.12 1.45 43.9 15.8 Fish meal 10.22 2.67 0.40 63.9 2.1 Peanut meal 6.96 0.54 1.15 43.5 31.3 Meat scrap 8.21 5.15 51.0 3.5 Soybean oil meal 7.07 0.59 1 .90 44.2 29.0 Horse manure 0.49 0.26 0.48 Cow manure 0.43 0.59 0.44 Chicken manure 1.31 0.40 0.54 Sheep manure 0.77 0.39 0.59 Cladophera sp. 2.90 0.32 Potamogeton sp. 1.30 0.13 2.08 Najas flexilis 1.90 0.30 2.19 Chara sp. 0.70 0.27 0.58 Wood yeast (Torula) 6.9" 8.6 0.82 1.96 43 ,54 37.4 43.9 Green Italian ryegrass 0..50 0.09 0.40 3.1 11.5 Green rye 0.42 0.10 2.6 12.9 Green oats 0.42 0.09 0..50 2.6 13.5 Green vetch 0.67 0.07 0.41 4.2 8.1 Green, white clover 0.82 0.09 0.38 5.1 6.6 "Calculated by dividing protein content by 6.25. ORGANIC FERTILIZERS Organic materials such as composted plant residues, manure, stable drainage, slaughterhouse waste, and municipal sewage are very good sources of nitrogen. They also contain a large percentage of organic carbon as well as other minerals in small amounts. Typical analyses are shown in Table 11. Values may vary slightly depending on the conditions under which the crops were grown or the products were processed. Organic fertilizers are recommended for only fingerling fish production to accelerate the production of zooplankton in rearing ponds, particularly in new or sterile ponds. Their use is limited by cost and labor requirements for application. The advantages of organic fertilizers are their (l) shorter cycle for plankton production than inorganic fertilizers, (2) decomposition to liberate CO^, which is used by plants for growth, (S) aid in clearing silt-laden waters, and (4) use as a supplemental feed. Their disadvantages are that they (l) are more expensive than inorganic fer- tilizers, (2) may deplete the oxygen supply, (3) may stimulate filamentous algae growth, and (4) require more labor to apply than inorganic fertilizers. 98 FISH HATCHERY MANAGEMENT INORGANIC FERTILIZERS Inorganic fertilizers are relatively inexpensive sources of nitrogen, phos- phorus, and potassium, which stimulate algal growth, and calcium, which helps to control water hardness and pH. In nitrogen- free water, 0.3 to 1.3 parts per million of nitrogen must be ad- ded to stimulate phytoplankton growth, and to sustain this growth about one part per million must be applied at weekly intervals. In a normal hatchery pond this comes to about eight pounds of nitrogen per surface acre. Because nitrogen can enter the pond system from the atmosphere, watershed, and decomposing organic matter, it is not always necessary to add more. For the operation of warmwater hatchery ponds, it is recommended that nitrogen be included in the fertilizer applications during the late spring and summer months for all ponds except those which have been weed- free for at least three years. If development of phytoplankton is delayed longer than four weeks, nitrogen should be added. Forms of nitrogen available for pond fertilization are listed on Table 12. Phosphorus is an active chemical and cannot exist alone except under very specialized conditions. It is generally considered to be the most essen- tial single element in pond fertilization and the first nutrient to become a limiting factor for plant growth. Plankton require from 0.018 to 0.09 part per million as a minimum for growth. Several workers have recommended applications of about 1.0 part per million phosphorus pentoxide (P^OrJ periodically during the production season. Table 12. nitrogen fertilizers for pond enrichment. pH OF CHEMICAL PERCENT AQUEOUS SOURCE MAIERIAL FORMULA NITROGEN SOLUTION Ammonium metaphosphate (NHJ3PO, XT' Ammonium nitrate NH4NO3 33.5 4.0 Ammonium phosphate (NH^j.PO^ 11* 4.0 Ammonium sulfate (NHjj.SO, 20 5.0 Anhydrous ammonia NH3HP 82 Aqua-ammonia NH3H2O 40-50 Calcium cyanamide CaCN,, 22 Diammonium phosphate (NH,)^HP03 21' 8.0 Urea H^HCONH^ 46 7.2 Sodium nitrate NaNO^ 16 7.0 "Also contains 73",i P^r,. 'Also contains 48", 1 P^O-,. 'Also contains 48-52"(i P^Or,. HATCHERY OPERATIONS 99 Table 13. sources of p^o, in commercial phosphate fertilizers SOURCE MATERIAL CHEMICAL FORMULA ' P;0-, AVAILABILTIY Ammonium metaphosphate Basic slag Bone meal Calcium metaphosphate Defluorinated rock Diammonium phosphate Enriched superphosphate Monoammonium phosphate Potassium metaphosphate Rock phosphate Triple (NHjaPO., (CaO-P^ySiO.^ Ca(P03)2 CalPOj^ (NHjaHPO^ Ca(H,P04), NH^H^PO, Ordinary Ca(H^P04)^ superphosphate Phosphoric acid H3PO4 KPO. (Ca3(P04),)3-CaF, (Ca(H,P04),)3 15 60-65 73 Variable solubility; has 17"" nitrogen 9 Poor in calcium-rich waters Not readily available Equal to superphosphate in acid and neutral soil 41.3 Used primarily in live- stock feeds; insoluble in water 53 Completely water solu- ble has 21" nitrogen 32 About the same as ordi- nary superphosphate 48 CompleteH water- soluble in form of ammophosphate; has 1 1" I nitrogen 18-20 Not completely water- soluble 72.5 Water-soluble and acid in reaction 55-58 Equal to or superior to ordinary superphos- phate; has 35-38','u 32 Least soluble of calcium salts; availability var- ies from 0 to 15"» 44-51 A major portion is water-soluble Phosphorus will not exist for long in pondwater solution. Although both plants and animals remove appreciable amounts of the added phosphate, the majority of applied phosphorus eventually collects in the bottom mud. Here, phosphorus may be bound in insoluble compounds that are per- manently unavailable to plants. Some 90-95% of the phosphorus applied to field crops in fertilizers becomes bound to the soil, and the same may hold true in ponds. 100 FISH HATCHERY MANAGEMENT A number of phosphate fertilizers are available for use in ponds. Ordi- nary superphosphate is available commercially more than any other form and is satisfactory for pond use. More concentrated forms may save labor in application, however. Sources of P^O-, in commercial phosphate fertiliz- ers are listed in Table 13. When nitrogen also is desired, ammoniated phos- phates are recommended as they are completely water-soluble and gen- erally should give a more rapid response. An application rate of 8 pounds P2O-, per surface acre is normal in pond fertilization. This amount supplies about 1 part per million in a pond averaging about 3 feet deep. In the United States, the usual practice is to supply the needed phosphorus periodically throughout the growing season. In Europe, however, the sea- sonal phosphorus requirements are supplied in one or two massive applica- tions either before or shortly after pond is filled, or at the beginning and middle of the fish production cycle. A 50-100"'i) increase over normal applications is justified in ponds with unusually hard waters, large amounts of iron and aluminum, or high rates of water exchange. Potassium generally is referred to as potash, a term synonomous with po- tassium oxide (K2O). The most common sources are muriate of potash (KCl) and potassium nitrate (KNO3). Potassium sulfate (K2SO4) also is a source of potassium. Potassium is less important than nitrogen or phosphorus for plankton growth, but it functions in plants as a catalyst. Increased phytoplankton growth occurs with increases in potassium from 0 to 2 parts per million; above 2 parts per million there is no additional phytoplankton growth. Many waters have an ample supply of potassium for plant growth, but where soils or the water supply are deficient or where heavy fertilization with nitrogen and phosphorus is employed, addition of potassium is desirable. It can be applied at the beginning of the production cycle, or periodically during the cycle. It is quite soluble and unless ad- sorbed by bottom deposits or taken up by plants, it can be lost by seepage or leaching. Calcium is essential for both plant and animal growth. It seldom is defi- cient to the point that it exerts a direct effect on growth. Many of its ef- fects are indirect, however, and these secondary influences contribute sig- nificantly to the productivity of a body of water. Waters with hardness of more than 50 parts per million CaC03 are most productive, and those of less than 10 parts per million rarely produce large crops. Calcium ac- celerates decomposition of organic matter, establishes a strong pH buffer system, precipitates iron, and serves as a disinfectant or sterilant. In some cases, fish production can be increased 25-100% by adding lime at the rate of 2 to 3 tons per acre. Calcium is available in three principal forms. It is 71"o of calcium oxide (CaO) or quicklime, 54% of calcium hydroxide (Ca(OH)2) or hydrated lime, and up to 40"ii of calcium carbonate (CaCO^) or ground limestone. HATCHERY OPERATIONS 101 The form of calcium to apply depends upon the primary purpose for which it is used. Unless bottom mud is below pH 7, lime is not recom- mended except for sterilization purposes. For general liming, calcium hy- droxide or ground limestone are the forms most suitable. Each has certain advantages and disadvantages which make it desirable in specific situa- tions. Waters softer than 10 parts per million total hardness generally require applications of lime, whereas waters harder than 20 parts per million sel- dom respond to liming. The need for lime may be indicated when inor- ganic fertilization fails to produce a substantial plankton bloom. However, analysis of the water or, preferably, of the bottom mud should be made for total hardness and alkalinity before lime is applied. A state agricultural experiment station or extension service can assist with these (and other) analyses. Liming can be done with the pond either dry or filled with water. Suit- able mechanical equipment is needed to assure uniform dispersion. A boat- mounted spreader can be used for ponds filled with water. If the pond contains water, additional amounts of lime may be added to satisfy the needs of the water as well as of the bottom mud. It may take 3 to 6 months before the pond responds. In some situations, limed ponds revert to an acid condition within two years after the initial application. COMBINING FERTILIZERS In making a decision on whether to use organic or inorganic fertilizers, the advantages and disadvantages should be carefully considered. Comparative tests have been attempted but conclusive answers as to which material is best often will depend upon the individual situation or production cycle in- volved. Combining organic and inorganic fertilizers is a common practice. Many workers have found that a combination of an organic meal and superphos- phate, in a ratio of 3:1, gave higher fish production than the organic material alone. In hatchery rearing ponds where draining is frequent and time for development of a suitable food supply often is limited, combining organic and inorganic fertilizers appears to be advantageous. While the cost of such a procedure is greater than with inorganic fertilization, the high value of the fish crop involved normally justifies the added cost, particu- larly in the case of bass and catfish rearing. The ratio of 4-4-1, N2-P20-,-K20, is needed to produce favorable plankton growth for fish production ponds. The fertilizer grade most com- monly used is 20-20-5, which gives the 4-4-1 ratio with relatively little filler. The type of fertilizer program chosen will be determined by such factors as species of fish reared, time of year, cost, availability of product, and past 102 FISH HATCHERY MANAGEMENT experience. If the species to be reared is a predator species such as large- mouth bass, striped bass, or walleye, a typical program might be as follows. In spring, while the pond is still dry, disk the pond bottom. Apply lime if needed to bring pH into a favorable range. The fertilizer can be spread on the dry pond bottom and the pond then filled, or the pond filled and then the fertilizer spread; the following example assumes it is on the pond bottom. Spread: 500 pounds per acre chopped alfalfa hay; 200 pounds per acre meat scraps; 200 pounds per acre ground dehydrated alfalfa hay; 50 pounds per acre superphosphate; 10 pounds per acre potash; 1,000 pounds per acre chicken manure. Fill the pond and wait 3 to 5 days before stock- ing fish. This fertilizer program for sandy loam soils and slightly acid waters will produce an abundance of zooplankton needed for rearing the predator species. Usually this amount is added only one time and will sustain the pond for 30-40 days. If the fish crop is not of harvest size by that time, a second application of all or part of the components may be needed. If the species to be reared is a forage species such as bluegill, redear sun- fish, goldfish, or tilapia, the following program might be used: 100 pounds per acre ammonium nitrate; 200 pounds per acre superphosphate; 50 pounds per acre potash; 100 pounds per acre chopped alfalfa hay; 300 pounds per acre chicken manure. This fertilizer program will produce more phytoplankton than the one outlined for predators. As with the one above, this program will have to be repeated about every 30-45 days. The type of fertilizer program that works best at any particular station will have to be developed at that station. The program that works best at one station will not necessarily work well at another. The examples given above are strictly guidelines. AQUATIC VEGETATION CONTROL Aquatic plants must have sunlight, food, and carbon dioxide in order to thrive. Elimination of any one of these requirements inhibits growth and eventually brings about the death of the plant. The majority of the com- mon water weeds start growth on the bottom. Providing adequate depth to ponds and thus excluding sunlight essential to plant growth may prevent weeds from becoming established. Water plants are most easily controlled in the early stages of development. Control methods applied when stems and leaves are tender are more effective than those applied after the plant has matured. In most cases, seeds or other reproductive bodies are absent in early development and control at this time minimizes the possibility of reestablishment. The first step in controlling aquatic vegetation is to identify the plant. After the problem weed has been identified, a method of control can be HATCHERY OPERATIONS 103 selected. Control methods may be mechanical, biological, or chemical, depending upon the situation. Mechanical control consists of removal of weeds by cutting, uprooting, or similar means. While specialized machines have been developed for mow- ing weeds, they are expensive and not very practical except in special cir- cumstances. In small ponds, hand tools can be employed for plant removal. Even in larger bodies of water, mechanical removal of weeds may be feasi- ble provided that work is begun when the weeds first appear. Biological weed control is based on natural processes. Exclusion of light from the pond bottom by adequate water depth and turbidity resulting from phytoplankton is one method. Production of filamentous algae that smother submerged rooted types of weeds is another. The most inexpensive form of weed control for many ponds is control or prevention through the use of fertilizers. When an 8-8-2 grade fertilizer is applied at a rate of 100 pounds per acre, every 2 to 4 weeks during the warm months of the year, microscopic plants are produced that shade the bottom and prevent the establishment of weeds. Although 8 to 14 applica- tions are needed each season, fish production is increased along with the weed control achieved. Generally, most aquatic weeds may be controlled by fertilization in properly constructed ponds. However, such a program of fertilization will be effective in controlling rooted weeds only if the secchi disk reading already is 18 inches or less. Winter fertilization is a specialized form of biological control effective on submerged rooted vegetation if the ponds cannot be drained. An 8-8-2 grade fertilizer or equivalent is applied at a rate of 100 pounds per acre every 2 weeks until a dense growth of filamentous algae covers the sub- merged weed beds. Once the algae appears, an application of fertilizer is made at 3- to 4-week intervals until masses of algae and rooted weeds be- gin to break loose and float. All fertilization is then stopped until the plants have broken free and decomposed. This will start in the late spring and generally takes from four to six weeks. Phytoplankton normally re- place the filamentous algae and rooted weeds and should be mantained by inorganic fertilization with 100 pounds of 8-8-2 per acre applied every 3 to 4 weeks. Lowering the water level of the pond in the late fall has been helpful in achieving temporary control of watershield. This practice also aids in the chemical control of alligator weed, water primrose, southern water grass, needlerush, knotgrass, and other resistant weeds that grow partially sub- merged and have an extensive root system. Plant-eating fish that convert vegetation to protein have been considered in biological control. Among these are grass carp, Israeli carp (a race of common carp), and tilapia. Experiments have indicated that the numbers of Israeli carp and tilapia required to control plants effectively are so large 104 FISH HATCHERY MANAGEMENT that these fish would compete for space and interfere with the production of other, more desirable species. Extensive development of herbicides in recent years makes chemical con- trol of weeds quite promising in many instances. When properly applied, herbicides are effective, fast, relatively inexpensive, and require less labor than some of the other control methods. Chemical control, however, is not a simple matter. Often the difference in toxicity to weeds and to fish in the pond is not great. Some chemicals are poisonous to humans or to livestock and they may have an adverse effect on essential food organisms. Decay of large amounts of dead plants can exhaust the oxygen supply in the water, causing death of fish and other aquatic animals. It is essential that discretion regarding treatment be followed if satisfactory results are to be obtained. An important aspect of vegetation control is the rate of dilution of ap- plied herbicides and the effect of substances present that may neutralize the toxicity of the chemical used. The rate of water exchange by seepage or outflow and the chemical characteristics of the water and pond bottom also affect the success of chemical control measures. Often the herbicide must reach a high percentage of the plant surface before a kill is obtained; the chemical must be applied carefully if good results are to be achieved. The herbicide is applied directly on emergent or floating weeds and to the water where submerged weeds are growing. The first type of treatment is called a local treatment, the second is termed a solution treatment ap- plied either to a plot or to the entire pond. Conventional sprayers are used to apply the local treatments and in some instances may be suitable for solution treatments. Chemicals for solu- tion treatment are sometimes diluted with water and poured into the wake of an outboard motor, sprinkled over the surface of the pond, or run by gravity into the water containing the weed beds. Crystalline salts may be placed in a fine woven cotton bag and towed by boat, allowing the herbi- cide to dissolve and mix with the pond water. Some herbicides are prepared in granular form for scattering or broadcasting over the areas to be treated. Generally, the more rapidly the chemical loses its toxicity the more uniformly it must be distributed over the area involved for effective results. Also, if the chemical is at all toxic to fish, it must be uniformly dis- tributed. Emergent or floating vegetation receiving local treatments applied with spray equipment should be uniformly covered with a drenching spray applied as a fine mist. A number of precautions should always be taken when herbicides are used. Follow all instructions on the label and store chemicals only in the original labeled container. Avoid inhalation of herbicides and prevent their repeated or prolonged contact with the skin. Wash thoroughly after han- dling herbicides, and always remove contaminated clothing as soon as pos- sible. Prevent livestock from drinking the water during the post- treatment period specified on the label. Do not release treated water to locations that HATCHERY OPERATIONS 105 may be damaged by activity of the chemical. Avoid overdoses and spil- lages. Avoid use near sensitive crops and reduce drift hazards as much as possible; do not apply herbicides on windy days. Clean all application equipment in areas where the rinsing solutions will not contaminate other areas or streams. Fish culturists must also be aware of the current registration status of herbicides. Continuing changes in the regulation of pesticide and drug use in the United States has created confusion concerning what chemicals may be used in fisheries work. Table 14 lists those chemicals that presently pos- sess registered status for use in the presence of food fish only, a food fish being defined as one normally consumed by humans. Special Problems in Pond Culture DISSOLVED OXYGEN Because adequate amounts of dissolved oxygen are critical for good fish growth and survival, this gas is of major concern to fish culturists (Figure 39). On rare occasions, high levels of oxygen supersaturation — caused by intensive algal photosynthesis — may induce emphysema in fish. Virtually all oxygen- related problems, however, are caused by gas concentrations that are too low. Tolerances of fish to low dissolved oxygen concentrations vary among species. In general, fish do well at concentrations above 4 parts per million. They can survive extended periods (days) at 3 parts per million, but do not grow well. Most fish can tolerate 1-2 parts per million for a few hours, but will die if concentrations are prolonged at this level or drop even lower. In ponds that have no flowing freshwater supply, oxygen comes from only two sources: diffusion from the air; and photosynthesis. Oxygen dif- fuses across the water surface into or out of the pond, depending on whether the water is subsaturated or supersaturated with the gas. Once oxygen enters the surface film of water, it diffuses only slowly through the rest of the water mass. Only if surface water is mechanically mixed with the rest of the pond — by wind, pumps, or outboard motors — will diffused oxygen help to aerate the whole pond. During warmer months of the year when fish grow well, photosynthesis is the most important source of pond oxygen. Some photosynthetic oxygen comes from rooted aquatic plants, but most of it typically comes from phy- toplankton. Photosynthesis requires light; more occurs on bright days than on cloudy ones. The water depth at which photosynthesis can occur depends on water clarity. Excessive clay turbidity or dense blooms of phy- toplankton can restrict oxygen production to the upper foot or less of wa- ter. Generally, photosynthesis will produce adequate amounts of oxygen for 106 FISH HATCFIKRY MANAGEMENT TaBI.K 14. HERBICIDES REGISTERED HY IHE UNH KD S I'A 1 ES FOOD AND DRUG AL. 1976; SNOW ET AL. U)64.) COMPOUND FORMll.Al ion" VEGETATION AFTECrED ToxicTTV ro ANIMALS Copper sulfate Crystals, 100"n Algae and submerged rooted plants Moderate to high Diquat Liquid, 35"'ii Emergent, terrestrial, Low (bromide) submerged Endothal Liquid, 35"ii Submerged, rooted Low Simazine Powder, 80"(i Algae, submerged, terrestrial Low 2,4- D' Granular, 10"n Floating, emergent, Low salt, 80"n terrestrial ester, 37-42% amine, 28-42"(i granular, 20"" Low or moderate "Percentages are percent actual ingredient. Consult product labels for limitations on use. 'Only for use by federal, state, and local public agencies. fish to a depth of two to three times the secchi disk visibility. Penetration of oxygen below this depth depends on mechanical mixing. Two processes use up dissolved oxygen: chemical oxidation and respira- tion. Both occur throughout the water column and in the top layer of pond sediments. The first involves chiefly inorganic compounds and elements, and rarely is of major significance in ponds. Respiration is the main cause of oxygen depletion. All aquatic organisms respire — not only fish, but plants, phytoplankton (even during photosynthesis), zooplankton, bottom animals (such as crayfish), and perhaps most importantly, the bacteria that live off nitrogenous and organic material. Over the whole year, but especially during the growing season, the oxy- gen concentration in a pond is determined primarily by the balance of pho- tosynthesis and respiration. For pond fish culture to succeed, photosyn- thesis must stay ahead of respiration. Pond management techniques involve manipulation of both components. Of all the physical variables that affect dissolved oxygen concentrations, temperature is by far the most important. It has direct influences on the oxygen balance: photosynthesis, respiration, and chemical oxidation all proceed faster at higher temperatures. It has a direct influence on a pond's A I en IK Y OI'KRAIIONS 107 AUMIMSIRAI 1U.\ lOR LSI. Willi lool) MSll. ll.BKl AK'l, I!i7i. SOIRC'K MKVF.R i: I AI'PLICAIION RATES MODL t)K ACTION COM MEN is" 0.1 -.").(> ppm 2-3 pounds/acre ()..')-2.() ppm 1-3 ppm 0.3-2.0 ppm (10-40 pounds/ (acre) 3-l,T pounds/acre Nonsystemic Nonsystemic Probably nonsystemic Systemic Systemic Limit is one part per million for copper complexes, but CuS04-5H20 and basic copper carbonate are exempted from the limit Interim limit in potable water is 0.01 part per million Interim limit in potable water is 0.2 part per million Upper limits are 12 parts per mil- lion in raw fish and 0.01 part per million in potable water. Upper limit in raw- fish and shellf- ish is 1 part per million. oxygen capacity: less oxygen dissolves in water at higher temperatures. It has an indirect effect on oxygen circulation: as temperature rises, water be- comes more difficult to mix. If temperatures rise high enough, and the wa- ter is deep enough, the pond may stratify into an upper, warmer, wind- mixed layer and a lower, cooler, poorly circulated layer. In such cases, lit- tle water moves across the thermocline separating the two layers. The upper layer receives, and keeps, most of the new oxygen (chiefly from pho- tosynthesis by phytoplankton); the lower layer receives little new oxygen, and loses it — sometimes completely — to respiration (chiefly by bacteria). Several pond management techniques attempt to overcome the effects such temperature- induced stratification has on the oxygen supply. It is easy to see why pond-oxygen problems are more acute in summer than in autumn, winter, and spring. When the water is cool, it can dissolve more oxygen, and it is more easily mixed by wind action to the pond bot- tom. Photosynthesis is less, but so is respiration, and photosynthetic oxy- gen is kept in the pond. In contrast, vr-ater circulation is constrained in summer. In the upper layers, especially in stratified ponds, photosynthesis may be so intense that the water becomes supersaturated with oxygen so that much of the gas is 108 FISH HATCHERY MANAGEMENT Figure 39. An essential instrument in any fish rearing opera- tion is an oxygen meter. Catastrophic fish losses can be avoided if oxygen concentrations are checked periodically and the optimum carrying capacity of the hatchery can be deter- mined. Several brands of meters are available commercially. (FWS photo.) lost to the air. The water has a lower capacity for oxygen, and little of it may reach the pond bottom. Planktonic animals have short life spans; as more are produced during warm weather, more also die and sink to the bottom, where bacteria decompose them — utilizing oxygen in the process. Respiration levels are high, meaning that more metabolism is occurring and more wastes produced. These also are stimulants to bacterial produc- tion. So is any uneaten food that may be provided by the culturist. Both oxygen production and consumption are very rapid, and the balance is HATCHERY OPERATIONS 109 vulnerable to many outside influences: a cloudy day that slows photosyn- thesis; a hot still day that causes stratification; a miscalculated food ration that is too large for fish to consume before it decomposes. Typically the summer oxygen content in a pond follows a 24- hour cycle: highest in the late afternoon after a day of photosynthesis; lowest at dawn after a night of respiration. It is the nighttime oxygen depletion that is most critical to pond culturists. Pond managers can take several precautions to prevent, or reduce the severity of, dissolved oxygen problems. (1) Most ponds are fertilized to stimulate plankton production for natur- al fish food. Suitable plankton densities allow secchi disk readings of 12-24 inches. Fertilization should be stopped if readings drop to 10 inches or less. Special care should be taken if the pond is receiving supplemental fish food, as this can stimulate sudden plankton blooms and subsequent die- offs. (2) Because the frequency of dissolved oxygen problems increases with the supplemental feeding rate, fish should not be given more than 30 pounds of food per acre per day. (3) If algicides are used to control plankton densities, they should be ap- plied before, rather than during, a bloom. Otherwise, the accelerated die- off of the bloom will worsen the rate of oxygen depletion. (4) During critical periods of the summer, the oxygen concentration should be monitored. This is most easily accomplished at dusk and two or three hours later. These two values can be plotted against time on a graph, and the straight line extended to predict the dissolved oxygen at dawn. This will allow emergency aeration to be prepared in advance. Dissolved oxygen problems may arise in spite of precautions. Corrective measures for specific problems are suggested below. (1) If there has been an excessive kill of pond weeds or plankton that are decaying, add 20'/o superphosphate by midmorning at a rate of 50-100 pounds per acre. Stir the pond with an outboard motor or otherwise mix or circulate water to rapidly distribute phosphate and add atmospheric oxy- gen; 1 to 2 hours of stirring a 1-acre pond should suffice. Dilute the oxygen- deficient water with fresh water of about the same temperature. Distribute, as evenly as possible, 100-200 pounds of hydrated lime, Ca(OH)2, per acre in the late afternoon if CO2 levels are 10 parts per mil- lion or higher. Then stir for another one to two hours. (2) Low dissolved oxygen may be caused by excessive rooted vegetation and a lack of phytoplankton photosynthesis. If the pond is unstratified, add P2O5 and stir or circulate as in (l) above. Add fresh water if available. If the pond is stratified, which is the usual case in warm months, aerate the surface waters by agitation, draw off the cool oxygen- deficient bottom wa- ter, or add colder fresh water. 1 10 FISH HATCHERY MANAGEMENT (3) If the problem is caused by too much supplemental feed, drastically reduce or eliminate feeding until the anaerobic condition is corrected. Drain off foul bottom water. Refill the pond with fresh water and add P^Or, to induce phytoplankton growth. (4) Summer stratification of ponds often is inevitable. During its early stage of development, when cool anaerobic water is less than 20-25% of the total pond volume and upper waters have a moderate growth of green plants, top and bottom water can be thoroughly mixed. Aerate the pond with special equipment or an air compressor, or vigorously stir it with an outboard- powered boat or with a pump. If the layer of anaerobic water is more than ^ the total pond volume, drain off the anaerobic water, refill with fresh water, and fertilize to re-establish the phytoplankton bloom. (5) Low dissolved oxygen may result from excessive application of organic fertilizers, which overstimulates plankton production. Treat this problem as in example (l), above. Two to six parts per million potassium permanganate (KMnO,) may be added to oxidize decaying organic matter, freeing the available oxygen for the pond fish. Quite often, oxygen depletion is caused by two or more of the above fac- tors acting simultaneously. In such cases, a combination of treatments may be needed. If a substantial amount of foul bottom water exists, the pond should never be mixed, because the oxygen deficit in the lower water layer may exceed the amount of oxygen available in the surface layer. Drain off the anaerobic water and replace it with fresh water from a stream, well, or adjacent pond. An effective technique is to pump water from just below the surface of the pond and spray it back onto the water surface with force. Small spray- type surface aerators are in common use. These aerators are most effective in small ponds or when several are operated in a large pond. More powerful aerators such as the Crisafulli pump and sprayer and the paddlewheel aerator supply considerably more oxygen to ponds than the spray- type surface aerators. However, Crisafulli pumps and paddlewheel aerators are expensive and must be operated from the power take-off of a farm tractor. The relative efficiency of several types of emergency aeration appears in Table 15. ACIDITY Fish do not grow well in waters that are too acid or too alkaline, and the pH of pond waters should be maintained within the range of 6.5 to 9. The pH of water is due to the activity of positively charged hydrogen ions (H ), and pH is controlled through manipulation of hydrogen ion concen- trations: if the pH is too low (acid water), H^ concentrations must be de- creased. The treatments for low pH (liming) were discussed on pages 108-109. The principle involved is to add negatively charged ions, such as carbonate hatchery operations 1 1 1 Table 15. amounts of oxygen added to pond waters by different tech- niques OF emergency aeration. (SOURCE: BOYD 1979.) OXYGEN RELATIVE ADDED EFFICIENCY TYPE OF EMERGENCY AREATION (LB/ACRE) ("..) Paddlewheel aerator 48.9 100 Crisafulli pump with sprayer 31.2 64 Crisafulli pump to discharge oxy- 19.0 39 genated water from adjacent pond Otterbine aerator (3.7 kilowatts) 15.2 31 CrisfuUi pump to circulate pond 11.8 24 water Otterbine aerator (2.2 kilowatts) 11.3 23 Rainmaster pump to circulate 10.7 22 pond water Rainmaster pump to discharge 6.0 12 oxygenated water from adjacent pond Air-o-later aerator (0.25 kilowatt) 3.9 8 (CO3") or hydroxyl (OH ), that react with H^ and reduce the latter's con- centration. Excessively high pH values can occur in ponds during summer, when phytoplankton are abundant and photosynthesis is intense. As carbon diox- ide is added to ponds, either by diffusion from the atmosphere or from respiration, it reacts with water to form a weak carbonic acid. The basic reaction involved is: CO^ + H^O ^ H^C03 ^ H+ + HCOr ^ 2H+ + C03=. As more CO2 is added, the reaction moves farther to the right, generating first bicarbonate and then carbonate ions; H"*^ is released at each step, increasing the acidity and lowering the pH. Photosynthesizing plants reverse the reaction. They take CO2 from the water, and the HC03~ and CO3" ions bind hydrogen; acidity is reduced and pH rises — often to levels above ten. Two types of treatment for high pH can be applied. One involves addi- tion of chemicals that form weak acids by reacting with water to release H^; they function much like CO^ in this regard. Examples are sulfur, fer- rous sulfate, and aluminum sulfate, materials also used to acidify soils. The action of sulfur is enhanced if it is added together with organic matter, such as manure. A second treatment for high pH is the addition of positively charged ions that bind preferentially with COa^; they keep the carbonate from 1 12 FISH HATCHERY MANAGEMENT recombining with hydrogen and prevent the above reaction from moving to the left, even though plants may be removing CO^ from the water. The most important ion used for this purpose is calcium (Ca ), which usually is added in the form of gypsum (calcium sulfate, CaSOj. The two types of treatments may be combined. For example, sulfur, manure, and gypsum together may be effective in reducing pond alkalinity. TURBIDITY Excessive turbidity in ponds obstructs light penetration; it can reduce pho- tosynthesis and make it more difficult for fish to find food. Much turbidity is caused by colloids — clay particles that remain suspended in water because of their small size and negative electric charges. If the charges on colloidal particles can be neutralized, they will stick together — flocculate — and precipitate to the bottom. Any positively charged material can help flocculate such colloids. Organic matter works, although it can deplete a pond's oxygen supply as it decomposes, and is not recommended during summer months. Weak acids or metallic ions such as calcium also can neutralize colloidal charges, and many culturists add (depending on pH) limestone, calcium hydroxide, or gypsum to ponds for this purpose. HYDROGEN SULFIDE Hydrogen sulfide, H^S, is a soluble, highly poisonous gas having the characteristic odor of rotten eggs. It is an anaerobic degradation product of both organic sulfur compounds and inorganic sulfates. Decomposition of algae, aquatic weeds, waste fish feed, and other naturally deposited organic material is the major source of H^S in fish ponds. The toxicity of H^S depends on temperature, pH, and dissolved oxygen. At pH values of five or below, most of the H^S is in its undissociated toxic form. As pH rises the H7S dissociates into S and H^ ions, which are nontoxic. At pH 9 most of the H^S has dissociated to a nontoxic form. Its toxicity increases at higher temperatures, but oxygen will convert it to nontoxic sulfate. H^S is toxic to fish at levels above 2.0 parts per billion and toxic to eggs at 12 parts per billion. It is a known cause of low fish survival in organi- cally rich ponds. If the water is well oxygenated, H^|S will not escape from the sediments unless the latter are disturbed, as they are during seining operations. Hydrogen sulfide mainly is a problem during warm months, when organic decomposition is rapid and bottom waters are low in dis- solved oxygen. Hydrogen sulfide problems can be corrected in several ways: (l) remove excess organic matter from the pond; (2) raise the pH of the water (see above); (3) oxygenate the water; (4) add an oxidizing agent such as potas- sium permanganate. HATCHERY OPERATIONS 113 WATER LOSS Water loss by seepage is a problem at many hatcheries. A permanent solu- tion is to add a layer of good quality clay about a foot thick, wetted, rolled, and compacted into an impervious lining, (in small ponds, the same effect can be achieved with polyethylene sheets protected with three to four inches of soil.) Bentonite can be used effectively to correct extreme water loss when applied as follows: (1) Disk the bottom soil to a depth of six inches, lapping cuts by 50%. (2) Harrow the soil with a spike- tooth harrow, overlapping by 50%. (3) Divide treated area into 10-foot by 10-foot squares. (4) Uniformly spread 50 pounds of bentonite over each square (20,000 pounds per acre). (5) Disk soil to a depth of three inches. (6) Compact soil thoroughly with a sheepsfoot roller. This procedure has reduced seepage over 90% in some cases. Evaporation is a problem in farm and hatchery ponds of the southwest. Work in Australia indicates that a substantial reduction in evaporation (25%) can be reduced by a film of cetyl alcohol (hexadecanol), applied at a rate of about eight pounds per acre per year. The treatment is only effec- tive in ponds of two acres or less. PROBLEM ORGANISMS Most plants, animals, and bacteria in a pond community are important in fish culture because of their roles as fish food and in photosynthesis, decomposition, and chemical cycling. However, some organisms are un- desirable, and sometimes have to be controlled. Some crustaceans — members of the Eubranchiopoda group such as the clam shrimp {Cyzicus sp.), the tadpole shrimp {Apus sp.) and the fairy shrimp [Streptocephalus sp.)— compete with the fish fry for food, cause ex- cessive turbidity that interfers with phytosynthesis, clog outlet screens, and interfere with fish sorting at harvest. They usually offer no value as fish food, because of their hard external shell and because of their fast growth to sizes too large to eat. These shrimp need alternating periods of flooding and desiccation to perpetuate their life cycles, and they can be controlled naturally if ponds are not dried out between fish harvests. However, they usually are con- trolled with chemicals. Formalin, malathion, rotenone, methyl parathion, and others have been used with varying degrees of success; many of these are very toxic to fish. The best chemicals today are dylox and masoten, which contain the active ingredient trichlorfon and which have been re- gistered for use as a pesticide with nonfood fish. Treatments of 0.25 part per million dylox will kill all crustaceans in 24 hours, without harming 114 FISH HATCHERY MANAGEMENT fish. Most of the desirable crustacean species will repopulate the pond in two or three days. Most members of the aquatic insect groups Coleoptera (beetles) and Hemiptera (bugs) prey on other insects and small fish. In some cases, members of the order Odonata (dragonflies) cause similar problems. Most of these insects breath air, and can be controlled by applying a mixture of one quart motor oil and two to four gallons diesel fuel per surface acre over the pond. As insects surface, their breathing apertures become clogged with oil and they may get caught in the surface film. The treatment is harmless to fish but supplemental feeding should be discontinued until the film has dissipated. Nonsurfacing insects can be killed by 0.25 part per mil- lion masoten. Large numbers of crayfish in rearing ponds may consume feed intended for the fish, inhibit feeding activity, cause increased turbidity, and interfere with seining, harvesting, and sorting of fish. Baytex is an effective control; 0.1-0.25 part per million Baytex will kill most crayfish species in 48 hours or less without harming the fish. Vertebrates that prey on fish may cause serious problems for the pond- fish culturist. Birds, otters, alligators, and turtles, to name a few, are impli- cated annually. Some can be shot, although killing of furbearing mammals generally requires a special license or permit issued by the states. Fences can keep out some potential predators, but nonlethal bird control (several forms of scaring them away) do not produce long-lasting results. Adult and immature frogs have long plagued the warmwater culturist. The adults are predaceous and may transmit fish diseases; the immature frogs consume feed intended for fish and must be removed by hand from fish lots awaiting transport. Adults usually are controlled with firearms, whereas attempts to control the young are limited to physical removal of egg masses from ponds or by treating individual masses with copper sulfate or pon's green. Although some laboratory success has been achieved with formalin, there still is no good chemical control available for frog tadpoles. Recordkeeping Factors to be Considered Recordkeeping, in any business or organization, is an integral part of the system. It is the means by which we measure and balance the input and output, evaluate efficiency, and plan future operations. Listed below are factors that should be considered in efficient record- keeping. These factors are particularly applicable to trout and salmon hatcheries, but many of them pertain to warmwater hatcheries as well. HATCHERY OPERATIONS 1 15 Water (1) Volume in cubic feet for each rearing unit and for the entire hatchery. (2) Gallons per minute and cubic feet per hour flow into each unit and for the entire hatchery. (3) Rate of change for each unit and for the total hatchery. (4) Temperature. (5) Water quality. Mortality (1) Fish or eggs actually collected and counted (daily pick-off). (2) Unaccountable losses (predation, cannibalism) determined by com- parison of periodic inventories. Food and Diet (1) Composition. (2) Cost per pound of feed and cost per pound of fish gained. (3) Amount of food fed as percentage of fish body weight. (4) Pounds of food fed per pound of fish produced (conversion). Fish (1) Weight and number of fish and eggs on hand at the beginning and end of accounting period. (2) Fish and eggs shipped or received. (3) Gain in weight in pounds and percentage. (4) Date eggs were taken, number per ounce, and source. (5) Date of first feeding of fry. (6) Number per pound of all lots of fish. (7) Data on broodstock. Disease (1) Occurrence, kind, and possible contributing factors. (2) Type of control and results. Costs (other than fish food): (1) Maintenance and operation. (2) Interest and depreciation on investment. (3) Analysis of all cost and production records. IKJ FISH HATCHERY MANAGEMENT Production Summary Some additional records that should be considered for extensive (pond) culture follow. Water (1) Area in acres of each pond. (2) Volume in acre-feet. (3) Average depth. (4) Inflow required to maintain pond level. (5) Temperatures. (6) Source and quality. (7) Weed control (dates, kind, amount, cost, results). (8) Fertilization (dates, kind, amount, cost, results). (9) Algae and zooplankton blooms (dates and secci visibility in inches; kinds of plankton). Fish (1) Broodstock (a) Species, numbers. (b) Stocked for spawning (species, numbers, dates). (c) Replacements (species, numbers, weights). (d) Feeding and care (kind, cost, and amounts of food, including data on forage fish production). (e) Diseases and parasites (treatments, dates, results). (f) Fry produced per acre and per female. (2) Fingerlings (a) Species (numbers stocked, size, weight, date) (b) Number removed, date, total weight, weight per thousand, number per pound. (c) Supplemental feeding (kind, amount, cost). (d) Disease and predation (including insect control, etc.). (3) Production per acre by species (numbers and pounds). (4) Days in production. (5) Weight gain per acre per day. (6) Cost per pound of fish produced at hatchery. (7) Cost per pound including distribution costs. A variety of management forms are in use at state, federal, and commercial hatcheries today. The following examples have been used in the National Fish Hatchery system of the Fish and Wildlife Service. These forms, or variations of them, can be helpful to the fish culturist who is designing a recordkeeping system. HATCHERY OPERATIONS 117 Lot History Production Charts Production lots of fish originating from National Fish Hatcheries are iden- tified by a one- digit numeral that designates the year the lot starts on feed and a two-letter abbreviation that identifies the National Fish Hatchery where the lot originated. When production lots are received from sources outside the National Fish Hatchery system the following designations ap- ply: (l) the capital letter "U" designates lots originating from a state hatchery followed by the two-letter abreviation of the state; (2) the capital letter "Y" and the appropriate state abbreviation designates lots originating from commercial sources; (3) the letter "F" followed by the name of the country identifies lots originating outside the United States. For example: Lot 7-En designates the 1977 year class originating at the Ennis National Fish Hatchery. Lot 7-UCA designates the 1977 year class originating at a California state fish hatchery. Lot 7-YWA designates the 1977 year class originating from a commercial hatchery in the state of Washington. Lot 7-F-Canada designates the 1977 year class originating in Canada. Lots from fall spawning broodstock that begin to feed after November 30th are designated as having started on January 1st of the following year. The practice of maintaining sublots is discouraged but widely separated shipments of eggs result in different sizes of fish and complicated record keeping. When sublots are necessary, they are identified by letters (a, b, c, etc.) following the hatchery abbreviation. Lot 7-En-a and 7-En-b designate two sublots received in the same year from the Ennis National Fish Hatchery. Identification of fish species should be made on all management records. The abbreviations for National Fish Hatcheries and the states are present- ed in Appendix E. Lot History Production charts should be prepared at the end of each month for all production lots of fish reared in the hatchery. This chart pro- vides valuable accumulated data on individual lots and is useful in evaluat- ing the efficiency and the capability of a hatchery. Information recorded on the chart will be used in completing a quarterly distribution summary and a monthly cumulative summary. These forms were developed for salmon and trout hatcheries. Parts of them are readily adaptable to intensive cul- ture of coolwater and warmwater fishes. Presently, information needed to estimate the size of fry at initial feeding (which allows projections of growth and feed requirements from this earliest stage) is lacking for species other than salmonids. For the time being, cool- and warmwater fish cultu- rists should ignore that part of the production chart, and pick up growth 118 IISII HATCHERY MANAGEMENT and feed projections from the time fry become large enough to be handled and measured without damage. The following definitions and instructions relate to the Lot History Pro- duction form used in National Fish Hatcheries (Figure 40). DEFINITIONS Date of initial feeding: This is the day the majority of fry accept feed or, in the case of fish transferred in, the day the lot is put on feed. Number at initial feeding: If lots are inventoried at initial feeding, this number will be used. If lots are not inventoried, the number of eggs re- ceived or put down for hatching, minus the number of egg or fish deaths recorded prior to initial feeding, will determine the number on hand at ini- tial feeding. Weight at initial feeding: The weight on hand at initial feeding should be recorded by inventory when possible. Otherwise, multiply the number at initial feeding, in thousands, by the weight per thousand: (thousands on hand) x (weight/1,000 fish) = weight on hand. Length at initial feeding: The length of fish at initial feeding, in inches, can be found from the appropriate length-weight table in Appendix I cor- responding to the size (weight per 1,000 fish). Size at initial feeding: For this chart, sizes of fish will be recorded as weight in pounds per 1,000 fish (Wt/M). When sample counts are not available, the size at initial feeding can be determined from Table 16. INSTRUCTIONS Column 1: Record the number of fish on hand the last day of the month. This is the number of fish in Column 1 of the previous month's chart, minus the current month's mortality (Column 4), minus the number of fish shipped out during the current month (Column 5), plus the additions for the current month (Column 7). This figure may be adjusted when the lot is inventoried. Report in 1,000's to three significant figures, i.e., 269, 200, 87.8, etc. Column 2: Record the inventory weight of the lot on the last day of the current month. When inventory figures are not available, the number on hand the last day of the current month (Column l), multiplied by the sam- ple count size (Column 3), equals the weight on hand at the end of the current month. Column 3: Record the size of the fish on hand the last day of the current month as determined by sample counts. Weight offish in sample , ^_,. x.r . , /, ^^^ r. i — — ^ ^ — X 1,000 = Weight/ 1,000 fish Number of fish in sample Column 4: Record the total deaths of feeding fish in the lot for the current month. HATCHERY OPERATIONS 119 STATION LOT HISTORY PRODUCTION LOT NUMBER SPECIES INITIAL FEEDING DATE NUMBER OF FISH WEIGHT OF FISH LENGTH WEIGHT PER 1000 FISH M 0 FISH ON HAND END OF MONTH WEIGHT PER 1000 MORTAL ITY FISH SHIPPED FISH ADDED WEIGHT GAIN (POUNDS! FOOD FED (POUNDS) FEED COST CONVERSION UNIT FEED COST TO DATE N T H NUMBER 1000s WEIGHT POUND NUMBER NUMBER WEIGHT NUMBER WEIGHT MONTH TO DATE MONTH TO DATE TO DATE MONTH TO DATE PER POUND PER 1000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 TOTAL DAY OF YEAR (JUL- IAN) M 0 N T H DIET IDENTIFICATION LENGTH ON LAST DAY OF MONTH CURRENT MONTHS LENGTH INCREASE NO DAYS SINCE INITIAL FEEDING AVERAGE DAILY LENGTH INCREASE (INCHES) LENGTH INCREASE 30 DAY MONTH TEMPERATURE UNITS TEMPERATURE UNITS PER INCH GAIN INCHES INCHES FOR MO TO DATE FOR MO TO DATE FOR MO TO DATE 18 19 20 21 22 23 24 25 26 27 28 TOTAL PERCENT SURVIVAL UNTIL TRANSFERRED. RELEASED OR DISTRIBUTED SAC FRY . REMARKS FEEDING FRY . FISH. Figure 40. Production form for recording lot history data. Temperature units are monthly temperature units, which equal TF above 32°F for the average monthly water temperature. 120 I ISH HATCHERY MANAGEMENT Table 16. the size of salmonid fry at initial feeding, based on the size of THE eyed egg listed AND THE CORRESPONDING WEIGHT PER 1,000 FRY. INITIAL FEEDING EYED EGG INITIAL FEEDING EYED EGG WEIGHT PER WEIGHT PER (NUMBER 1,000 FRY LENGTH (NUMBER 1,000 FRY LENGTH PER OUNCE) (POUNDS) (INCHES) PER OUNCE) (POUNDS) (INCHES) 200 0.53 1.10 460 0.23 0.83 210 0..50 1.08 470 0.22 0.82 220 0.48 1.06 480 0.22 0.81 230 0.46 1.05 490 0.21 0.81 240 0.44 1.03 500 0.21 0.80 2.50 0.42 1.02 510 0.21 0.75 260 0.40 1.00 520 0.20 0.79 270 0.39 0.99 530 0.20 0.79 280 0.38 0.98 540 0.19 0.78 290 0.36 0.96 5.50 0.19 0.78 300 0.35 0.96 560 0.19 0.75 310 0.34 0.95 570 0.18 0.77 320 0.33 0.94 580 0.18 0.77 330 0.32 0.93 590 0.18 0.76 340 0.31 0.92 600 0.18 0.76 350 0.30 0.91 610 0.17 0.75 360 0.29 0.90 620 0.17 0.74 370 0.28 0.89 630 0.17 0.74 380 0.28 0.88 640 0.16 0.74 390 0.27 0.88 6.50 0.16 0.74 400 0.26 0.87 660 0.16 0.73 410 0.26 0.86 670 0.16 0.73 420 0.25 0.85 680 0.15 0.73 430 0.24 0.84 690 0.15 0.72 440 0.24 0.84 700 0.15 0.72 450 0.23 0.83 Column 5: Record the total number of fish shipped from the lot for the current month. Column 6: Record the total weight of the fish shipped during the current month. Column 7: Record the total number of fish added to the lot in the current month. Column 8: Record the total weight of the fish added to the lot in the current month. Column 9: Record the gain in weight for the current month. This is equal to Column 2 (this month) — Column 2 (last month) + Column 6 — Column 8. Column 10: Record total weight gain to date. This is equal to Column 10 (last month) + Column 9 (this month). HATCHERY OPERATIONS 121 Column 11: Record the total food fed for the current month from daily records. Column 12: Record the total food fed to date. This is equal to Column 12 (last month) + Column 11 (this month). Column 13: Record the cumulative cost of fish food fed to date. This is equal to Column 13 (last month) + cost for this month. Report to the nearest dollar. Column 14: Record feed conversions for this month. This is equal to Column 1 1 -^ Column 9. Record conversion to two decimal places. Column 15: Record the conversion to date. This is Column 12 -i- Column 10. Column 16: Record to the nearest cent, the unit feed cost per pound of fish reared. This is Column 13 ^ Column 10. Column 1 7: Record, to the nearest cent, the unit feed cost to date per 1,000 fish. This is (Column 3 — the weight per 1,000 fish reported at initial feeding) x Column 16. Column 18: Identify the type of diet fed for the current month including the cost per pound. Column 19: Record, to two decimal places, the length of the fish on hand the last day of the current month. This comes from the length-weight table appropriate for Column 3. Column 20: Record the increase in fish length for this month. For new lots, this is Column 19 — the length at initial feeding. For pre-existing lots, this is Column 19 (this month) — Column 19 (last month). Column 21: Record the number of days since the date of initial feeding. Column 22: Record, to two decimal places, the average daily increase in fish length. For new lots, this is Column 20 ^ the number of days the lot was on feed. For pre-existing lots, this is Column 20 ^ the number of days in the month. Column 23: Record, to two decimal places, the average daily length in- crease to date. This is Column 19 — length at initial feeding -^ Column 21. Column 24: Record, to two decimal places, the length increase during a 30-day unit period. This is Column 22 x 30. Column 25: Record the monthly mean water temperature in degrees Fahrenheit. Monthly Temperature Units (MTU) available per month are the mean water temperature minus 32°F. If a lot of fish was started part way through the month, the MTU reported for this column must reflect the actual days the lot was on feed. For example, if fish were on feed from June 16th through June 30th, the MTU available to the lot must reflect 15 days. A detailed explanation of Monthly Temperature Units is given on page 62. Column 26: Record, to one decimal place, the temperature units available to date. This is Column 26 (last month) + Column 25 (this month). 122 FISH HATCHERY MANAGEMENT Column 27: Record the Monthly Temperature Units per inch of gain for the current month. For new lots, this is Column 25 ^ Column 20. For pre- existing lots, this is Column 25 ^ Column 24. Column 28: Record the Monthly Temperature Units required per inch of gain to date. This is Column 26^ (Column 19 — length at initial feeding). TOTALS AND AVERAGES Totals in Columns 4, 5, 6, 7, and 8 are the sums of entries in their respec- tive columns. The last entry for Columns 10, 12, 13, 15, and 16 is used as the total for the respective column. For Column 17, the aggregate feed cost per 1,000 fish is Column 13 H- Column 5. Totals or averages for Columns 18 through 28 have been omitted for this form. Hatchery Production Summary The Hatchery Production Summary is prepared at the end of each month (Figure 4l). Entries on this form are taken from the Lot History Produc- tion (LHP) chart. Hatchery Production Summaries provide cumulative monthly information for all production lots reared at the hatchery on an annual basis. Once a lot has been entered on this form, the lot should be carried for the entire year. When a lot is closed out during the year, entries in Columns 2, 3, 4, 13, and 14 will be omitted for the month the lot was closed out and for the remaining months in that fiscal year. DEFINITIONS Density index is the relationship of the weight of fish per cubic foot of water to the length of the fish. Flow index is the relationship of the weight of fish per gallon per minute flow to the length of fish. Weight of fish is the total weight on hand from Column 3. Length of fish is the average length of fish on hand from Column 4. Cu ft water is the total cubic feet of water in which each lot is held the last day of the month. GPM flow is the total hatchery flow used for production lots the last day of the month. Water being reused though a series of raceways is not con- sidered; however, reconditioned water (e.g., through a biological filter) is included in the total flow. HATCHERY OPERATIONS 123 STATION HATCHERY PRODUCTION SUMMARY PERIOD COVERED OCT 1, 19 through DENSITY INDEX FLOW INDEX TOTAL FLOW SPECIES FISH ON HAND END OF MONTH FISH SHIPPED THIS FY GAIN THIS FY FISH FEED EXPENDED CONVER SION UNIT FEED COST TU PER INCH TU TO DATE LENGTH INCREASE AND LOT PER LB PER 1000 30 DAY MONTH NUMBER WEIGHT LENGTH NUMBER WEIGHT POUNDS COST INCHES 1 2 3 4 5 6 7 8 9 lO 11 12 13 14 TOTAL AVERAGE Figure 41. The hatchery production summary is used to record the monthly total and average production data. T.U. denotes temperature units; F.Y. is fiscal year. INSTRUCTIONS Compute the following indexes. Density Index weight of fish Flow Index = (average length of fish) (cu. ft. water) weight of fish (average length of fish) (GPM flow) Column 7: List the species of fish and the lot number. Column 2: Record the number of fish on hand at the end of the month for the individual lots from Column 1 of the LHP Chart. Column 3: Record the weight of fish on hand at the end of the month for the individual lots from Column 2 of the LHP chart. Column 4: Record the size of the fish on hand at the end of the month for the individual lots from Column 19 of the LHP chart. Column 5: Record the total number of fish shipped from the individual lots during the year, from Column 5 of the LHP chart. Column 6: Record the gain in weight to date for the individual lot during the year, from Column 10 of the LHP chart. 124 FISH HAICHERY MANAGEMENT Column 7: Record the total food fed to date for the individual lot for the fiscal year only, from Column 12 of the LHP chart. Column 8: Record the total cost of food fed to date for the individual lot during the year, from Column 13 of the LHP chart. Column 9: Record the feed conversion to date. This is Column 7 (this form) -^ Column 6 (this form). Column 10: Record the unit feed cost per pound of fish to date. This is Column 8 (this form) -^Column 6 (this form). Column VI: Record the unit feed cost per 1,000 fish for the individual lot during the year, from Column 17 of the LHP chart. If a lot is carried over for two years, subtract the size (weight/ 1,000) recorded at the end of the year in Column 3 of the LHP chart from the size (weight/1,000) recorded the last day of the current month and multiply the difference by the unit feed cost per pound recorded in Column 10 of the Hatchery Production Summary form. Column 12: Record the current month entry from Column 28 of the LHP chart. Column 13: Record the current month entry from Column 26 of the LHP chart. Column 14: Record the current month entry from Column 24 of the LHP chart. TOTALS AND AVERAGES Column 2: Record the total number of fish on hand at the end of the current month. Column 3: Record the total weight of fish on hand at the end of the current month. Column 4: Record the weighted average length of fish on hand at the end of the current month. Multiply each entry in Column 2 by the correspond- ing entry in Column 4. Add the respective products and divide this sum by the total number on hand from Column 2. Column 5: Record the total number of fish shipped this fiscal year. Column 6: Record the total gain in weight for the hatchery for this fiscal year. Column 7: Record the total pounds of fish food fed for this fiscal year. Column 8: Record the total cost of fish food fed for this fiscal year. Column 9: Record the food conversion to date. This is Column 7 ^ Column 6. Column 10: Record the cost per pound gain to date. This is Column 8 -^ Column 6. Column 11: Record the average unit feed cost per 1,000 fish reared to date. This is Column 8 -^ (Column 2 + Column 5). HATCHERY OPERATIONS 125 POND NO AREA. POND .ACRE FT RECORD STATION . . YEAR . Date Pond Species Stocked STOCKED SHIPPED Date Applied N P Organic Resu fs Cost Filled Date Number Weight Date Number Weight Total Total Fertilizer COST PER POUND FISH PRODUCED Hprhiride TRANSFERRED TO OTHER UNITS FOR FURTHER REARING & NOT CHARGED TO FISH SHIPPED Date Number Size Weight To Pond No AMOUNT & KINDS OF MATERIALS USED FOR WEED & PEST CONTROL DATE Applied Trade Name Strength Amount Method Results Cost Total Total POND RECORD SPECIES PRODUCTION PER ACRE TOTAL FOR POND NUMBER PER POUND FOR BROOD POND RECORD NUMBER WEIGHT NUMBER WEIGHT Niimhor "f fry harvo^tod Niimhpr nf fry harup<;tpri ppr fpm^lp REMARKS TOTAL DISEASE CONTROL DATA DATE TYPE TREATMENT COST EST. MORTALITY • TOTAL Figure 42. Pond record form used to record fish production, chemical treat- ments, and disease control data. 126 FISH HATCHERY MANAGEMENT Column 12: The sum of the entries in this column divided by the number of entries gives the average Temperature Units (TU's) required per one inch of growth to date. Column 13: The sum of the entries in this column divided by the number of entries gives the average Temperature Units (TU's) to date. Column 14: The sum of the entries in this column divided by the number of entries is the average length increase to date. Warmwater Pond Records Important recordkeeping information for warmwater fish pond manage- ment is shown in Figure 42. Accurate historical data concerning fertiliza- tion and pond weed control can be useful in evaluating the year's production. Bibliography Allen, Kenneth O. 1974. Effects of stocking density and water exchange rate on growth and survival of channel catfish Iclalurus punctatus (Rafinesque) in circular tanks. Aquacul- ture 4:29-39. Andrews, James W., Lee H. Knight, Jimmy W. Page, Yoshiaki Matsuda, and Evan Brown. 1971. Interactions of stocking density and water turnover on growth and food conversion of channel catfish reared in intensively stocked tanks. Progressive Fish- Culturist 33(4):197-203. , and Y(JSHIAKI Matsuda. 197,5. The influence of various culture conditions on the ox- ygen consumption of channel catfish. Transactions of the American Fisheries Society l()4(2):322-327. , and Jimmy W. Page. 1975. The effects of frequency of feeding on culture of catfish. Transactions of the American Fisheries Society 104(2):317-321. Bardach, John E., John H. Ryther, and William O. McLarney. 1972. Aquaculture, the farming and husbandry of fresh water and marine organisms. Wiley Interscience, Divi- sion of John Wiley and Sons, New York. 868 p. Bonn, Edward W., William M. Bailey, Jack D. Bayless, Kim E. Erick-son and Robert E. Stevens. 1976. Guidelines for striped bass culture. Striped Bass Committee, Southern Division, American Fisheries Society. 103 p. , and Billy J. Follis. 1967. Effects of hydrogen sulfide on channel catfish, Ictalurus punctatus. Transactions of the American Fisheries Society 9f)(l);31-36. Boyd, Claude E. 1979. Water quality in warmwater fish ponds. Agricultural Experimental Station, Auburn University, Auburn, Alabama. 359 p. , E. E. Prather, and Rcjnald W. Parks. 1975. Sudden mortality of a massive phyto- plankton bloom. Weed Science 23:(il-67. Broussard, Meryl C, Jr., and B. A. Simcq. 1976. High-density culture of channel catfish in recirculating system. Progressive Fish-Culturist 38(3) : 138-141 . Brown, M.xrgaret E. 1957. The physiology of fishes, volume 1, metabolism. Academic Press, New York. 447 p. HATCHERY OPERATIONS 127 Bryan, Robert D., and K. O. Allen. 1969. Pond culture of channel catfish fingerlings. Pro- gressi\e Fish-Culturist 3 1 (l):38-4l^. Bl LLCJCK, G. L. 1972. Studies on selected myxobacteria pathogenic for fishes and on bacterial gill disease in hatchery- reared salmonids. US Fish and Wildlife Service Technical Paper fiO. Blrrow.'^, Roger E. I!(ri4. Effects of accumulated excretory products on hatchery-reared sal- monids. US Fish and Wildlife Service Research Report 66. and Bobby D. Combs. 1968. Controlled environments for salmon propagation. Pro- gressive Fish-Culturist 30 (3): 123- 136. Bl TERBAfGH, Galen L., and Harvey Willoughby. 1967. A feeding guide for brook, brown and rainbow trout. Progressive Fish-Culturist 29(4) : 2 10-21."). Carikr, Ray R., and K. O. Allen. 1976. Effects of flow rate and aeration on survival and growth of channel catfish in circular tanks. Progressive Fish-Culturist 38(4) :204-206. Colt, John, George Tghobanoglois, and Brian Wong. 197,'). The requirements and maintenance of environmental quality in the intensive culture of channel catfish. Department of Civil Engineering, University of California, Davis. 119 p. Deuel, Charles R., Da\ h:) C. Haskell, D. R. Brockway, and O. R. Kingsblry. 19.-)2. New York State fish hatchers feeding chart, 3rd edition. New York Conservation Department, .Alban\ , New York. Dexter, Ralph W., and D. B. McCarraher. 1967. Clam shrimps as pests in fish rearing ponds. Progressive Fish-Culturist 29(2):10.t-107. Downing, K. M., and J. C. Merkens. 19.t."). The influence of dissolved oxygen concentration on the toxicity of unionized ammonia to rainbow trout [Salmo gairdnen Richardson). Annals of Applied Biology 43:243246. Ellioit, J. M. 197.5. Weight of food and time required to satiate brown trout, Saimo trutta. Freshwater Biology ,t:,51 64. Emerson, Kenneth, Rosemarie C. Rlsso, Richard E. Lend, and Robert V. Thurston. 197.T. Aqueous ammonia equilibrium calculations: effect of pH and temperature. Jour- nal of the Fisheries Research Board of Canada 32(l2):2379-2383. ExERHARi, W. Harry, Alfred D. Eipper, and Willl\m D. Youngs. 197,"). Prmciples of fishery science. Comstock Publishing Associates, Ithaca, New York. 288 p. Flick, Willla.M. 1968. Dispersal of aerated water as related to prevention of winterkill. Pro- gressive Fish-Culturist 3()(l):13-18. Freeman, R. I., D. C. Haskell, D. L. Longacre, and E. W. Stiles. 1967. Calculations of amounts to feed in trout hatcheries. Progressive Fish-Culturist 29(4):194- 209. Gr.-yfe, Delano R. 1968. The successful feeding of a dry diet to esocids. Progressive Fish- Culturist 30(3):1.52. , and Leroy Sorenson. 1970. The successful feeding of a dr\ diet to esocids. Progres- sive Fish-Culturist 32fl);31-3,5. Greenland, Donald C, and R. L. Gill. 1974. A diversion screen for grading pond- raised channel catfish. Progressive Fish-Culturist 36(2):78-79. Hackney, P. A. 1974. On the theory of fish density. Progressive Fish-Culturist 36(2):66-71. Haskell, Da\ id C. 19,5.5. Weight of fish per cubic foot of water in hatchery troughs and ponds. Progressive Fish-Culturist 17(3):1 17- 1 18. 1959. Trout growth in hatcheries. New York Fish and Game Journal 6(2):20.5-237. Heutit, G. S., and Burrows, R. E. 1948. Improved methods of enumerating hatchery fish populations. Progressive Fish-Culturist 10(l):23-27. Hornbeck, R. G., W. White, and F. P. Meyer. 196,5. Control of Apus and fairy shrimp in hatchery rearing ponds. Proceedings of the Annual Conference Southeastern Associa- tion of Game and Fish Commissioners 19:401-404 HuTCHENS, Lynn H., and Robert C. Nord. 1953. Fish cultural manual. US Department of Interior, .Mbuquerque, New Mexico. 220 p. (Mimeo.) 128 1 ISIl HATCHERY MANAGEMENT Inslek, TnKormi.us I), 1977. Starting smallmouth bass fry and fingerlings on prepared diets. Project completion report (FH-4312), Fish Cultural Development Center, San Marcos, Texas. 7 p. Kennedy, Mary M. lf)72. Inexpensive aerator saves fish. Farm Pond Harvest f)(3):(). Kramkr, Chin and M.wo. l!)7fj. Washington Salmon Study. Kramer, Chin and Mayo, Con- sulting Engineers, Seattle, Washington. 197fi. Statewide fish hatchery program, Illinois. CDB Project Number 102-()l()-()0f). Kramer, Chin and Mayo, Inc., Consulting Engineers, Seattle, Washington. Lagler, Karl F. 195fi. Fresh water fishery biology, 2nd edition. William C. Brown, Du- buque, Iowa. 421 p. Lamberton, Dale. 1977. Feeds and feeding. Spearfish In-Service Training School, US Fish and Wildlife Service, Spearfish, South Dakota. (Mimeo.) 1977. Hatchery management charts. Spearfish In-Service Training School, US Fish and Wildlife Service, Spearfish, South Dakota. (Mimeo.) Larmoyeux, J.'^CK D., and Rcjbert G. Piper. 1973. Effects of water re-use on rainbow trout in hatcheries. Progressive Fish-Culturist 3.)(l):l-8. Lay, Bill A. 1971. Applications for potassium permanganate in fish culture. Transactions of the American Fisheries Society 100(4) :813-81(i. Lehritz, Earl, and Robert C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of Fish and Game, Fish Bulletin l(')4. 197 p. LlAO, Pall. 1974. Ammonia production rate and its application to fish culture system plan- ning and design. Technical Reprint Number 35, Kramer, Chin and Mayo, Inc., Con- sulting Engineers, Seattle, Washington. 7 p. LloyI), R., and D. W. M. Herbert. 1960. The influence of carbon dioxide on the toxicity of un-ionized ammonia to rainbow trout [Salmo gairdneri Richardson). Annals of Applied Biology 48(2) :399- 404. , and Lydia D. Orr. 1969. The diuretic response by rainbow trout to sublethal con- centrations of ammonia. Water Research 3(5):33.')-344. Lowman, Fred G. 1965. A control for crayfish. Progressive Fish-Culturist 27(4): 184. Mazuranich, John J. 1971. Basic fish husbandry. Spearfish In-Service Training School, US Fish and Wildlife Service, Spearfish, South Dakota. 61 p. (Mimeo.) McCraren, J. P. 1974. Hatchery production of advanced largemouth bass fingerlings. Proceedings of the 54th Annual Conference, Western Association of Game and Fish Commissioners: 260-270. , and R. M. Jones. 1974. Restoration of sock filters used to prevent entry of wildfish into ponds. Progressive Fish-Culturist 36(4) :222. , J. L. Millard, and A. M. Woolven. 1977. Masoten (Dylox) as a control for clam shrimp in hatchery production ponds. Proceedings of the Annual Conference Southeastern Association of the Fish and Wildlife Agencies 31:329-331. , and T. R. Phillips. 1977. Effects of Masoten (Dylox) on plankton in earthen ponds. Proceedings of the Annual Conference Southeastern Association of the Fish and Wildlife Agencies 31:441448. , and Roberi G. Piper. Undated. The use of length-weight tables with channel cat- fish. US Fish and Wildlife Service, San Marcos, Texas, typed report. 6 p. McNeil, William J., and Jack E. Bailey. 1975. Salmon rancher's manual. National Marine Fisheries Service, Northwest Fisheries Center, Auke Bay Fisheries Laboratory, Auke Bay, Alaska, Processed Report. 95 p. Merna, James W. 1965. Aeration of winterkill lakes. Progressive Fish-Culturist 27(4):199-202. Meyer, Fred P., R. A. Schnick, K. B. Gumming, and B. L. Berger. 1976. Registration status of fishery chemicals. Progressive Fish-Culturist 38(l):3-7. HATCHERY OPERATIONS 129 , Kermit E. Sneed, and Paul T. Eschmever, editors. l!)7:i Second report to the fish farmers. US Fish and Wildlife Service Resource Publication IKl MoRio.N, K. E. 1953. A new, mechanically adjustable three-way grader. Progressive Fish- Culturist 15(3) :99- 103. 1956. A new mechanically adjustable multi-size fish-grader. Progressive Fish- Culturist 18(2):62-66. Pecdr, Charles H. 1978. Intensive culture of tiger muskellunge in Michigan during 197fi and 1977. American Fisheries Society Special Publication 11:202- 209. Phillips, Arthur M., Jr. 1970. Trout feeds and feeding. Manual of Fish Culture, Part 3.b.5, Bureau of Sport Fisheries and Wildlife, Washington, D.C. 49 p. Piper, R(JBERT G. 1970. Know the proper carrying capacities of your farm. American Fishes and US Trout News 15(l):4-6, 30. 1972. Managing hatcheries by the numbers. .American Fishes and US Trout News 17 (3): 10, 25-26. , Janice L. Blumberg, and Jamieson E. Holuay. 1975. Length-weight relationships in some salmonid fishes. Progressi\e Fish-Culturist 37(4) : 181- 184. Pyle, Earl A. 1964. The effect of grading on the total weight gained by brown trout. Pro- gressive Fish-Culturist 26(21:70-75. Glen Hammer, and A. M. Phillips, Jr. 1961. The effect of grading on the total weight gained by brook trout. Progressive Fish-Culturist 23(4) :162 168. Ray, Johnny, and Verl Stexens. 1970. Using Baytex to control crayfish in ponds. Progres- sive Fish-Culturist 32(l):58-60. ROBINETTE, H. Randall. 1976. Effect of selected sublethal levels of ammonia on the growth of channel catfish [ictalurus punctatus). Progressive Fish-Culturist 38(l):26-29. Satchell, Donald P., S. D. Crawford, and W. M. Lewis. 1975. Status of sediment from catfish production ponds as a fertilizer and soil conditioner. Progressive Fish-Culturist 37(4):191-193. Schultz, Ronald F., and C. David Varnicek. 1975. Age and growth of largemouth bass in California farm ponds. Farm Pond Harvest 9(2):27-29. Smith, Charlie E. 1972. Effects of metabolic products on the quality of rainbow trout. Amer- ican Fishes and US Trout News 17(3):7-8, 21. , and Robert G. Piper. 1975. Lesions associated with chronic exposure to ammonia. Pages 497-514 in William E. Ribelin and George Migaki, editors. The pathology of fishes. The University of Wisconsin Press, Madison. , and 1975. Effects of metabolic products on the quality of rainbow trout. Bozeman Information Leaflet Number 4, Fish Cultural Development Center, Bozeman, Montana. 10 p. Snow, J. R. 1956. Algae control in warmwater hatchery ponds. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 10:80-85. , R. O. Jones, and W. A. Rogers. 1964. Training manual for warmwater fish culture, 3rd revision. US Department of Interior, Warmwater In-Service Training School, Marion, Alabama. 244 p. SORENSON, Leroy, K. Buss, and A. D. Bradford. 1966. The artificial propagation of esocid fishes in Pennsylvania. Progressive Fish-Culturist 28(3): 133- 141. Stickney, R. R., and R. T. Lovell. 1977. Nutrition and feeding of channel catfish. Southern Cooperative Series, Bulletin 218, Auburn University, Auburn, Alabama. 67 p. TaCKETT, Dewey L. 1974. Yield of channel catfish and composition of effluents from shallow-water raceways. Progressive Fish-Culturist 36(l):46-48. Thurston, R. V., R. C. Russo, and K. Emerson. 1974. Aqueous ammonia equilibrium cal- culations. Technical Report 74-1, Fisheries Bioassay Laboratory, Montana State Universitv, Bozeman, Montana. 130 FISH HATCHERY MANAGEMENT Tkisski.I., K. 1'. 1M72. The j)ercent un-ionizcd ammonia in aquee)us ammonia solutions at dif- ferent pH levels and tem{)eratures. Journal of the Fisheries Research Board of Canada 2<)(l()):ir)0.'') l.'>()7. Tl CKKR, Craig S., and Ci.ai dk E. Bovd. 1!)77. Relationships between potassium perman- ganate treatment and water quality. Transactions of the American Fisheries Society l()fi(5):481 488. TUNISON, A. V. 1945. Trout feeds and feeding. Cortland Experimental Hatchery, Cortland, New York. (Mimeo.) TwoNGO, Tl.MOTHY K., and H. R. MacCrimmon. 1!)7(). Significance of the timing of initial feeding in hatchery rainbow trout, Sabno fiairdruri. Journal of the Fisheries Research Board of Canada 33 (i)) : 1 !) 1 4 1 92 1 . US Bureau of Sport Fisheries and Wildlife. 1!)7(). Report to the fish farmers. US Fish and Wildlife Service Resource Publication 83. Wedf.MEYER, Gary A., and James W. Wood. 1974. Stress as a predisposing factor in fish diseases. Fish Disease Leaflet 38, US Department of Interior, Fish and Wildlife Serv- ice, Washington, D.C. 8 p. Westers, Harry. 1970. Carrying capacity of salmonid hatcheries. Progressive Fish-Culturist 32(l):43-4fi. , and Kei I H Pr.MI. 1977. Rational design of hatcheries for intensive salmonid culture, based on metabolic characteristics. Progressive Fish-Culturist 39(4) : 1.57-1(1.5. WlELOLGHBY, Harvey. 19(i8. A method for calculating carrying capacities of hatchery troughs and ponds. Progressive Fish-Culturist 3()(3) : 173- 174. , Howard N. Larsen, and J. T. Bowen. 1972. The pollutional effect of fish hatcheries. American Fishes and US Trout News 17(3):(i-7, 20-21. Wood, Jame.S W. 1968. Diseases of Pacific salmon, their prevention and treatment. State of Washington, Department of Fisheries, Olympia, Washington 7fi p. Broodstock, Spawning, and Egg Handling Broodstock Management Portions of this chapter have been quoted extensively from Bonn et al. (1976), Kincaid (1977), Lannan (1975), Leitritz and Lewis (l976), McNeil and Bailey (1975), and Snow et al. (1968). These and other sources are listed in the references. The efficient operation of a fish rearing facility requires a sufficient quantity of parent or broodfish of good quality. The quantity of broodfish needed is determined by the number of eggs needed to produce the fry re- quired, with normal losses taken into account. Quality is a relative term that is best defined by considering the use of the product. Persons produc- ing fish for a restaurant or supermarket use different measurements of qual- ity than a hatchery manager rearing fish for use in research "or stocking. Most work defining fish quality has focused on performance in the hatchery, broodfish reproduction, and progeny growth and survival under hatchery conditions. In the future more emphasis will be placed on the ability of hatchery fish to survive after release and their contribution to a particular fishery program. 131 132 FISH HATCHERY MANAGEMENT Acquisition of Broodstock Stock for a hatchery's egg supply may be wild stock, hatchery stock, a hy- brid of two wild stocks, a hybrid of two hatchery stocks, a hybrid of wild and hatchery stock, or purchased from a commercial source. Currently, broodstocks of most trout and warmwater species are raised and main- tained at the hatchery, whereas Pacific and Atlantic salmon, steelhead, and striped bass broodfish are captured as they ascend streams to spawn. Cap- ture and handling of wild fish populations should utilize methods that min- imize stress. The installation of fishways or traps has proved successful in capturing mature salmon and steelhead as they complete their migratory run. Broodfish of coolwater species, such as northern pike, muskellunge, and walleye, usually are wild stock captured for egg- taking purposes. Wild muskellunge broodstock have been captured in trap nets set in shallow bays. As the nets are checked, the fish are removed and tested for ripe- ness. Some hatcheries sort the fish and take the eggs at the net site, while others transport the fish to the hatchery and hold the fish in tanks or race- ways until they are ripe. Walleye and sauger broodfish are collected in the wild with Fyke nets, gill nets with 1.5 or 2.0- inch bar mesh, and electrical shockers. Most suc- cessful collections are made at dusk or at night when the water tempera- ture is about 36°F. Gill nets fished at night should be checked every two or three hours to prevent fish loss and undue stress before spawning. Mature sauger and walleye females can be identified by their distended abdomens and swollen reddish vents which change to purple as they ripen. In trans- porting broodfish to the hatchery, at least 2 gallons of water should be pro- vided per fish. Wild northern pike broodstocks can be caught in trap nets, pound nets or Fyke nets (Figure 43). When pike are trapped, they become unusually active and are highly prone to injury. The use of knotless nylon nets will reduce abrasion and loss of scales. Catfish, largemouth and smallmouth bass, and sunfish broodstock may be captured in the wild by netting, electroshocking, or trapping. However, spawning of wild broodstock is often unreliable during the first year. Con- sequently, most warmwater species are reared and held as broodstock in a manner similar to that used for salmonids. Spawning information and temperature requirements for various species of fish are presented in Table 17. Care and Feeding of Broodfish Proper care of domestic broodstock is very important for assuring good production of eggs, fry, and fingerlings. Methods differ with species, but BROODSTOCK, SPAWNING, AND EGG HANDLING 133 Figure 43. Wild northern pike broodstock are trapped for egg- taking purposes. the culturist must provide conditions as optimum as possible for such things as pond management, disease control, water quality, and food sup- ply. The salmonid fishes generally reduce their feeding activity prior to spawning, and Pacific salmon discontinue feeding entirely during the spawning run. Trout broodfish usually are fed formulated trout feeds in quantities of 0.7-1.0% of body weight per day at water temperatures averaging 48-53°F, and then fed ad libitum as spawning season approaches. Food intake can drop as low as 0.3-0.4% of body weight per day during ad libitum feeding, when the fish are fed high- protein diets containing 48-49% protein and 1,560-1,600 kilocalories per pound of feed. In some cases, coolwater species are held at the hatchery and a domesti- cated broodstock developed. Coolwater fishes all are predators and must be provided with suitable forage organisms. There has been some recent suc- cess in developing formulated diets that cool- and warmwater predators will accept, and in developing new strains or hybrids of these species that will accept formulated feeds. For predator species such as largemouth bass, providing a suitable food or- ganism for growth and maintenance in the amount needed is very impor- tant. The rapid growth and development of largemouth bass makes raising 134 fish iiaix-hi-.rv management Table 17. spawning informaiion and temperaflre requirements for is expressed in "e. SI' EC IKS SPAWNING TEMPKRATIRK EGGS PER POUND FREQUENCY RANGE OPTIMUM SPAWNING OF FISH Chinook salmon Once per life span 33-77' .50-57° 4.5-5.5° 3.50 Coho salmon Once per 33-77° 48-58° life span Sockeye salmon Once per 33-70° .50-,59° life span Atlantic salmon Annual- 33-75° 50-62° Biennial 4.5-55° 45-.54° 42-50° 400 500 800 Rainbow trout Annua! 33-78° 50-60° 50-55° 1,000 Brook trout Annual 33-72° 4.5-.55° 4.5-.5.5° 1,200 Brown trout Annual 33-78° 48-60° 48-5,5° 1,000 Lake trout Annual 33-70° 42-.58° 48-52° 800 Northern pike Annual Muskellunge Annual Walleye Annual 33-80° 33-80° 40-65° 4.5-65° 33-80° 4.5-60° 40-48° 4.5-5.5° 48-55° y,ioo 7,000 25,000 Striped bass Annual 3.5-90° 5.5-75° 5.5-71' 100,000 Channel catfish Annual 33-95° 70-85° 72-82° 3,7.50 Flathead catfish Annual 33-95° 65-80° 70-80° 2,000 BROODSTOCK, SPAWNING, AND EGG HANDLING 135 VARIOUS SPECIES OF FISH AS REPORTED IN THE LITERATURE. TEMPERATURE REMARKS Upstream migration and maturation, 4.')-()() , eggs that had developed to the 128-cell stage in 42.5° water could tolerate water at 3.")° for the remainder of the incubation period. The 128- cell stage was attained in 144 hours of incubation. Eggs reached the 128-cell stage in 72 hours at 42. .5° but required an additional 24 hours of development at that temperature before they could withstand 35° water. Temperatures in excess of 54° affect maturation of eggs and sperm in adults; normal growth and development of eggs does not proceed at temperatures above 49°; at least 50" mortality at 54° can be expected. Broodfish should not be held in water temperatures exceeding 56°, and preferably not above 54° for at least six months before spawning. Rainbow trout eggs will not develop normally in the broodfish if constant water temperatures above 56° are encountered prior to spawning. The eggs cannot be incubated in water below 42° without excessive loss. Broodfish can tolerate temperatures greater than 66° but the average water temperature should be 48-50° for optimal spawning activity and embryo survival. Eggs will develop normally at the lower temperatures, but mortalities are likely to be high. Eggs do exceptionally well in hard water at 50° Water temperatures should not drop during the spawning season. Temperatures near an optimum of 54° are recommended in northern pike management. The optimum temperature ranges for fertilization, incubation, and fry survival are 43-54°, 48-59°, 59-70°, respectively. If unusually cold weather occurs after the fry hatch, fry survival may be affected. Feeding of fry may also be reduced when temperatures are low. Temperature shock between 65° and higher temperatures may have a more deleterious affect on freshly fertilized eggs than if the eggs are incubated for 16 to 44- hours at 65° before transfer to the higher water temperatures. 136 FISH HATCHERY MANAGEMENT Table 17. continued. SPECIES SPAWNING TEMPERATURE EGGS PER POUND •REQUENCY RANGE OPTIMUM SPAWN IN(; (JF FISH Largemouth bass Annual 33-95° 55-80° 60-65° 13,000 Smallmouth bass Annual 33-90° 50-70° 58-62° 8,()()() Bluegill Intermittent 33-95° 55-80° 65-80° 50, ()()() Golden shiner Intermittent 33-90° 50-80° 65-80° 75,000 Goldfish Intermittent 33-95° 45-80° 55-80° 50,000 American shad Annual 33-80° 45-70° 50-65° 70,000 Common carp Intermittent 33-95° 55-80° 55-80° 60,000 Semi-annually broodfish of this species relatively simple. Eggs can be obtained from one- year-old fish that have reached a size of 0.7-1.0 pounds. Brood bass can be expected to spawn satisfactorily for three to four seasons and should be between 3 and 4 pounds at the end of this time. It is suggested that one- third of the broodstock be replaced each year. The food organism can be reared on the station or purchased from outside sources. As a minimum standard, enough food should be provided to produce a weight gain in the broodstock of 50'^ per year. For largemouth bass, as an example, 5 pounds of forage food produce about 1 pound of fish gain, in addition to the 3 pounds of forage per pound of bass required for body maintenance. Thus, a 1-pound bass being held for spawning should be provided a minimum of 5.5 pounds of forage fish. Fish typically lose 10-20% of their body weight during the spawning season. Much of this is due to the release of eggs and sperm, and is most pronounced in females. Feeding may be interrupted during courtship or during periods when the nest and fry are protected against predators. Not all species protect their young, but male largemouth bass, bluegill, and oth- er sunfishes do. This weight loss must be regained before subsequent eggs and sperm are developed. Feeding schedules should reflect the nutritional status of the fish and be tailored to their respective life histories. Close attention should be given to the quality and availability of the forage fish provided. The forage should be acceptable to the cultured fish BROODSTOCK, SPAWNING, AND EGG HANDLING 137 REMARKS Eggs can be successfully incubated at constant temperatures between 55° and 75°. Hatching success may be lower at 50° and 80°. The eggs may be especially sensitive to sharp changes in temperature during early development. and small enough to be easily captured and consumed. The pond should be free of filamentous algae or rooted vegetation that might provide cover and escape for the forage fish. Pond edges with a minimum depth of 2 feet permit the predator fish to range over the entire pond and readily capture the food provided. The holding pond should be inspected at 2- to 3-week intervals, and seine samples of forage fish should be taken throughout the summer, fall, and spring months. When samples taken with a 15-foot seine contain fewer than 15-25 forage fish of an appropriate size, the forage should be replen- ished. Tadpoles, crayfish, bluegills, and miscellaneous other fishes that may accidentally develop in the pond cannot be depended upon to satisfac- torily feed the hatchery broodstock. Instead, a suitable forage species should be propagated in adequate quantities to assure both maintenance and growth of the cultured species. Maintenance of broodstock represents the first phase of activity that must be accomplished in channel catfish culture. Broodfish in most situa- tions are domesticated strains that have been hatchery-reared.. Dependable spawning cannot be obtained until female fish are at least 3 years old, although 2-year-old fish that are well-fed may produce eggs. Females weighing 1-4 pounds produce about 4,000 eggs per pound of body weight. Larger fish usually yield about 3,000 eggs per pound of body weight. Fish in poor condition can be expected to produce fewer eggs and lower quality spawn. 138 FISH HATCHERY MANAGEMENT Channel catfish broodstock usually are maintained in a holding pond and fed a good quality formulated diet. The density of broodfish should not exceed 600-800 pounds per acre. The amount of food provided depends on water temperature; above 70°F feed 3-4% of body weight per day; from 50°-70°F, 2% per day; below 50°, 2% twice per week. Spawning success and the quality of eggs and fry are improved, in many cases, if the fish are provided a diet including natural food. For this reason, many cul- turists supplement a formulated diet with cultured forage fish. Another practice is to supplement a diet once or twice a week with liver fed at a rate of 4% of fish weight. Differentation between male and female channel catfish also can be a problem. The secondary sex characters are the external genitalia. The fe- male has three ventral openings — the anus, the genital pore, and the uri- nary pore — whereas the male has only an anus and urogenital pore. In the male, the urogenital pore is on a papilla, while in the female the genital and urinary openings are in a slit, without a papilla. Experienced breeders can discern the sex of large broodfish and detect the papilla by rubbing in a posterior to anterior direction or by probing the urogenital opening with an instrument such as a pencil tip. Tertiary sex characteristics develop with approaching sexual maturation. In the male, they include a broad muscular head wider than the body, a darkening of the body color, and a pronounced grayish color under the jaws. Females have smaller heads, are lighter in color, and have distended abdomens at spawning time. Brood bluegills generally are obtained by grading or selecting larger fingerlings from the previous year's crop. These replacements may either be mixed with adults stocked in spawning- rearing ponds or stocked alone in production ponds. The preferred procedure is to keep year classes of broodfish separate so that systematic replacement can be carried out after the broodfish have been used for three spawning seasons. Distinctive sexu- al characteristics differentiate male bluegills from females (Figure 44). Special holding ponds normally are established for keeping broodfish. If the stocking density is below 200 pounds per acre, the broodstock can be sustained by natural food organisms, provided the pond has had a good fer- tilization program. If more than 200 pounds per acre are held, a supple- mental formulated diet usually is fed. The feeding rate is "iX of body weight at water temperatures above 70°F, and 2.5% of body weight at tem- peratures from 70-50°F. Below 50°F, feeding can be suspended entirely. Redear sunfish do not adapt to formulated feed as readily as bluegills be- cause they are more predatory. Diets can be fed at 0.5—2%) of body weight, depending on temperature, but suitably sized organisms also should be pro- vided. Redear sunfish eat shelled animals and a holding pond should sup- port a good crop of mollusks. BROODSTOCK, SPAWNING, AND EGG HANDLING 139 '«:•;!:■:'■ 'v?i^>\- MM ;';'';.'''^, ;'.••;•:■ >://.'.;j(t : i'/.-'-jfeSI l^fc" •"'•'•••' l^Bt-'t^!':;*;' M:ii^::::i:il:i Figure 44. Sexual dimorphism develops in mature broodfish. The male blue- gill becomes much darker than the female and changes body shape (upper panel). Male salmon also show changes in color and the jaw becomes hooked, forming a kype (lower panel). 140 FISH HATCHERY MANAGEMENT Forage Fish Forage species cultured as feed for predatory broodfish vary depending on the species of broodfish being maintained. Several factors must be con- sidered when a forage organism is selected. The forage must not be too large for the predator to consume nor too small to provide adequate nour- ishment, and should be able to reproduce in adequate numbers at the time v^hen it is needed. Forage species should have the right shape and behavior to attract the predator, be easily captured by the broodfish, and require little pond space to rear. If the forage can be obtained commercial- ly at a reasonable cost, production space and time will be saved at the hatchery. Species of forage fish propagated as food include suckers, fathead min- nows, goldfish, golden shiners and Tilapia. Shad, herring, bluegills, and trout are used to a lesser degree as forage fish. Suckers, fathead minnows, and goldfish usually are used with coolwater broodfish. These species are early spawners, making them available as forage when needed by the broodfish. Northern pike, walleye, and muskellunge prefer a long slender fish with good body weight, such as the sucker. Culture of forage fish varies with the species; some notes about the most frequently utilized species follow. WHITE SUCKER White suckers occur east of the Great Plains from northern Canada to the southern Appalachian and Ozark mountains. They prefer clearwater lakes and streams. In early spring, they run upstream to spawn in swift water and gravel bottoms, although they also will spawn to some extent in lakes if there are no outlets and inlets. White suckers have diversified feeding habits, but prefer planktonic crustaceans and insect larvae. Broodfish usually are taken from streams during the natural spawning run. These fish are hand-stripped and the eggs are hatched in jars. After hatching, the fry are stocked in ponds prepared for the production of zoo- plankton. Stocking rates vary with the size of the desired forage: 40,000-60,000 per acre for 1-2-inch fish; 20,000-40,000 for 2-4-inch fish; 5,000-20,000 for 4-6- inch fish. Ponds of moderate fertility usually produce the most suckers. Sterile ponds do not produce enough food for white suckers and excessively fertile ponds often produce too much aquatic vegetation. Ponds with large popu- lations of chironomid fly larvae (bloodworms) in the bottom muds will produce good sucker crops year after year. Loam and sandy- loam soils pro- duce the best chironomid populations; peat and peat-loam ponds are ade- quate for this purpose, but silt and clay- loam ponds are poor. Ponds with BROODSTOCK, SPAWNING, AND EGG HANDLING 141 heavy, mosslike growths of filamentous algae over the bottom do not pro- duce good crops of suckers. After the suckers attain a length of 1-2 inches, an organic fertilizer such as manure can be added to increase the production of natural food. Suck- ers will adapt to formulated feeds as a supplemental diet. FATHEAD MINNOW The fathead minnow occurs throughout southern Canada and in the United States from Lake Champlain west to the Dakotas and south to Kentucky and the Rio Grande River. It feeds mainly on zooplankton and insects. The spawning season extends from May until the latter part of August. The eggs are deposited on the underside of objects in a pond, and hatch in 4.5 to 6 days. Mature fathead minnows range in length from 1^ to 4 inches, the male being consistently larger than the female. The life span of hatchery-reared fathead minnows is 12 to 15 months, depending on the size of the fish at maturity. During the early spawning season a large majority of the males usually die within 30 days after the onset of spawn- ing activities, and a large percentage of the gravid females will die within 60 days. One- to two-inch immature fatheads, even though only a year old, die shortly after they become gravid at an age of about 15 months. Thus, the older fish in a pond should be used as forage after they have spawned. Ponds for fathead minnows should have flowing, cool water from a spring or well. The ponds should not be larger than one acre or smaller than 0.25 acre. The water depth should average about 3 feet and range from 2 feet at the shallow end to 6 feet at the drain. The pond should be equipped with a controllable water inlet and drain. Ponds to be used for reproduction should be lined along two banks with rocks ranging in size from 6 to 12 inches in diameter, or with tile, extending from six inches above the planned water level to two feet below it. This material provides spawning surfaces for the minnows. The brood ponds should be stocked in early April with about 60% adult minnows and 40"n immature fish. Both adults and juveniles are used as breeders because of the species' short life span. In this way, one can be sure of a continuous, uninterrupted supply of newly hatched fry. The brood ponds should be stocked at the rate of 15,000 to 25,000 fish per acre. Fathead minnows normally start spawning activities during the latter part of April or at a time when the pondwater temperature reaches 65°F. They spawn intermittently throughout the summer, provided the water temperature does not rise above 85°F. When this temperature is reached, spawning ceases, and is not resumed until the pond is cooled by a weather change or by an increased flow of spring water. Within a few days of spawning activity, small fry will be seen swimming near the surface, a few 142 FISH HATCHERY MANAGEMENT feet out from shore. As soon as fry become numerous, they can be captured with a small fry seine and transferred to rearing ponds at the rate of 300,000 to 600,000 fry per acre. From this stocking rate, a harvest of about 150,000 fathead minnows can be expected. During the first few weeks of life following transfer to the rearing pond, fry grow very rapidly. Within 4 to 8 weeks, many of these fish will mature and begin to spawn. When this occurs, the pond may become overstocked and the fish become stunted. The excess fry should be transferred to another pond or destroyed. A productive pond should have a good plankton density; a Secchi disk reading of about 12 inches should be maintained. Fathead minnows readily accept a formulated diet, usually in the form of meal. The amount recom- mended is 2% of body weight per day, not to exceed 25 pounds per day per acre. In 6 to 10 weeks this procedure will produce 2-inch forage organ- isms. GOLDFISH Goldfish are good forage fish. This is a hardy species that prospers during hot weather. Goldfish feed largely on plankton, but will take insects and very small fish. They reproduce in large numbers and grow rapidly. Goldfish normally start spawning when the water reaches 60°F and con- tinue to spawn throughout the summer if the temperature remains above 60°F and the fish are not overcrowded. The favorite spawning time is right after sunrise on sunny days. The females lay their eggs on grass, roots, leaves, or similar objects. A female goldfish may lay 2,000 to 4,000 eggs at one time and may spawn several times during the season. The eggs are adhesive and stick to any object they touch. The live eggs are clear and turn brown as they develop; dead eggs are cloudy and opaque. The eggs hatch in 6 to 7 days at a water temperature of 60°F. Goldfish averaging 0.25 to 0.75 pound reproduce well and should be used for broodstock. Broodstock overwintered in crowded ponds will not spawn in the ponds. Maximum egg production is obtained by keeping the broodfish in the overwintering pond until after the last spring frost. Then the fish are stocked in the production ponds at the rate of 100-200 adults per acre without danger of frost damaging the eggs or fry. Goldfish will ac- cept formulated feeds and feeding rates should be set to produce 2-3-inch fish in the shortest time. Broodstock ponds should be fertilized to insure that phytoplankton pro- duction is sustained all summer. Secchi disk readings should be 18 inches or less. Ponds should contain suitable natural vegetation or artificial spawning material. The water level is commonly dropped in early spring to en- courage the growth of grass along the shoreline. When the ponds are filled, BROODSTOCK, SPAWNING, AND EGG HANDLING 143 this grass provides spawning sites. Aquatic plants are also utilized as spawning sites. If natural vegetation is absent or scarce, hay, straw, or mats of Spanish moss may be anchored in shallow areas for spawning purposes. If the eggs are allowed to hatch in the ponds where they are laid, the adults will stop spawning when the pond becomes crowded with young fish. If the eggs are removed and transferred to clean ponds to hatch, the uncrowded adults will continue to spawn all summer. In general, ponds containing both young and adults should produce up to 100,000 fingerlings per acre. In intensive situations, where a heavily stocked brood pond pro- vides fry for eight or ten rearing ponds, production will reach 200,000 to 300,000 goldfish per acre. GOLDEN SHINER Golden shiners are widely distributed from eastern Canada to Florida, and westward to the Dakotas and Texas. They prefer lakes and slack-water areas of rivers. Young golden shiners eat algae and cladocerans. Adults will consume a variety of organisms, from algae and zooplankton to mollusks and small fish. Eggs are adhesive and are scattered over filamentous algae and rooted aquatic plants. Golden shiner breeders should be at least 1 year old, and 3-8 inches long. About 50% of the broodstock should be shorter than 5 inches in length; otherwise the stock might be predominantly females, as the males are consistently smaller than females. The stocking rate in large ponds, where the fry will remain with the adults, should range from 2,000 to 3,000 fish per acre. In ponds where egg or fry removal is planned, the stocking rate should be 4,000-8,000 adults per acre. Golden shiners start spawning activity when the water temperature rises above 65°F, but if the temperature exceeds 80°F, spawning ceases. During this period, at least four or five distinct spawning cycles occur, separated by periods of about 4 or 5 days. Spawning usually starts early in the morn- ing and terminates before noon. The females deposit their eggs on any type of submerged plants or debris. At temperatures of 75-80°F, fertilized eggs hatch within four days. Shortly thereafter, fry congregate in schools near the surface along the shoreline, where they can be collected with a fine- mesh net and transferred to growing ponds. Because adults often cannibalize the young if the two age groups are left together, the fry should be transferred to other ponds at the rate of 200,000-300,000 fry per acre. Successful production will yield 75,000-150,000 2-3- inch fish per acre. In ponds where the fry remain with the adults, 60,000 shiners per acre is considered good production. Golden shiners, like most other forage species, can be fed a supplemental formulated diet to increase growth rate. 144 FISH HATCHERY MANAGEMENT When golden shiners are seined from a pond, the seine should be of cot- ton or very soft material because the scales are very loose on this species. Harvesting at water temperatures below 75°F will reduce stress. TILAPIA Fish of the genus Tilapia are native to Africa, the Near East, and the Indo-Pacific, but are presently widely distributed through the world. Tila- pia are cichlids, and most species are mouth brooders; females incubate eggs and newly hatched fry in their mouth for 10-14 days. When the fry are free- swimming they begin feeding on algae and plankton. Tilapia tolerate temperatures in excess of 100°F, but do not survive below 50-55°F. Consequently, their culture as forage fish is restricted to the southern United States. Even there, broodfish usually need to be overwintered in water warmer than 55°F. Most tilapia are very durable and tolerant, able to survive low oxygen and high ammonia concentrations. Tilapia are excellent forage species in areas where culture is possible: easy to propagate; prolific; rapid growing; disease-resistant; and hardy for transferring in hot weather. Rearing ponds should be prepared and fertil- ized to produce an abundance of phytoplankton. If 200-250 adults are stocked in a pond after the water temperature is 75°F or above, they will produce 100,000 juveniles of 1-3 inches in 2-3 months. The adults will spawn and rear a new brood every 10-14 days throughout the summer. Tilapia accept dry food, and supplemental feeding will increase the growth rate. Improvement of Broodstocks Fish stocks may be improved by several methods, some of which are: selec- tive breeding, the choosing of individuals of a single strain and species; hy- bridization, the crossing of different species; and crossbreeding, the mating of unrelated strains of the same species to avoid inbreeding. SELECTIVE BREEDING Selective breeding is artificial selection, as opposed to natural selection. It involves selected mating of fish with a resulting reduction in genetic varia- bility in the population. Criteria that often influence broodfish selection for selective breeding include size, color, shape, growth, feed conversion, time of spawning, age at maturity, reproductive capacity, and past survival rates. These may vary with conditions at different hatcheries. No matter what type of selection BROODSTOCK, SPAWNING, AND EGG HANDLING 145 program is chosen, an elaborate recordkeeping system is necessary in order to evaluate progress of the program. Inbreeding occurs whenever mates selected from a population of hatchery broodfish are more closely related than they would be if they had been chosen at random from the population. The extent to which a partic- ular fish has been inbred is determined by the proportion of genes that its parents had in common. Inbreeding leads to an increased incidence of phenotypes (visible characteristics) that are recessive and that seldom occur in wild stocks. An albino fish is an example of a fish with a recessive phenotype. Such fish typically are less fit to survive in nature. Animals with recessive phenotypes occur less frequently in populations where mat- ing is random. Problems that can arise after only one generation of brother-sister mat- ing include reduced growth rate, lower survival, poor feed conversion, and increased numbers of deformed fry. Broodstock managers must be aware of the problems that can result from inbreeding and employ techniques that will minimize potential breeding problems. To avoid inbreeding, managers should select their broodstocks from large, randomly mated populations. Significant differences have been found in rainbow trout between females of different ages in egg volume, egg size, and egg numbers per female. Three-year-old females provide a higher percentage of eyed eggs and larger, more rapidly growing fingerlings than two-year-old females. Growth of the fingerlings is influenced by the age of the female broodfish and is directly related to the size of the egg. The egg size is dependent on the age and size of the female broodfish. Generally, the egg size increases in fe- males until the fifth or sixth year of life and then subsequently decreases. If inbreeding is avoided, selective breeding is an effective way to im- prove a strain of fish. A selective breeding program for rainbow trout at the Manchester, Iowa National Fish Hatchery resulted in fish 22% heavier than fish hatched from unselected individuals. Selective breeding in trout has increased growth rate, altered the age of maturation, and changed the spawning date. A system has been developed for maintaining trout broodstocks for long periods with lower levels of inbreeding than might be experienced in ran- dom mating. It requires the maintenance of three or more distinct breeding lines in a rotational line-crossing system. The lines can be formed by: (a) an existing broodstock arbitrarily subdivided into three groups; (b) eggs taken on three different spawning dates and the fry reared separately to adulthood; or (c) three different strains or strain hybrids. Rotational line- crossing does nothing to reduce the level of inbreeding in the base broodstock, but serves only to reduce the rate at which further inbreeding occurs. Consequently, it is essential that a relatively high level of genetic diversity be present in the starting broodstock. The use of three different 146 FISH HATCHERY MANAGEMENT 0 < \, s s s N S z o } .*- 1— < cc 1 UJ 2 LU CJ V s s N S V s ' ' 2 :^==T Figure 45. Rotational line-crossing system based on three lines. Each box represents a pool of fish belonging to a specific line. Solid lines show the source of females used to produce the next generation. The dotted lines represent the males used in the mating system. Generations of offspring from the original lines are presented on the left of the columns. (Source: Kincaid 1977.) strains or the subdivision of a first generation strain hybrid is the preferred method for line formation, because either of these tends to maximize the initial genetic diversity within the base population. After the three lines have been formed, the rotational line-crossing system can be implemented. At maturity, matings are made between lines. Females of line A are mated to males of line C to advance line A. Females of line B are mated to males of line A to advance line B, and females of line C are mated to males of line B to advance line C. Each succeeding generation is advanced by re- peating this procedure (Figure 45). The rotational line-crossing system is flexible enough to fit into most broodstock operations. At least 300 fish (50 males and 50 females from each of the three lines) are needed for maintenance of the population, but this number could be set at any level necessary to meet the egg production needs of a particular hatchery operation. BROODSTOCK, SPAWNING, AND EGG HANDLING 147 One potential problem with the system is the amount of separate holding facilities required for maintaining up to 15 groups if each line and year class are held separately. This problem sometimes can be overcome by us- ing marks such as fin clips, brands, or tags to identify the three lines and then combining all broodfish of each year class in a single rearing unit. The total number of broodfish to be retained in each year class would be determined by the production goals of the particular station, but equal numbers of fish should come from each line. This method will not only slow down inbreeding, but will also make a selection program more effec- tive. Studies have been conducted on the growth and survival of progeny from mating of hatchery and wild steelheads to determine if hatchery fish differ from wild fish in traits that affect the survival of wild populations. They indicated that wild fish x wild fish had the highest survival, and wild fish X hatchery fish had the highest growth rates. In the hatchery, how- ever, fish from a hatchery x hatchery cross had the highest survival and growth rates. With salmon, where the adult returns to the hatchery exceed the number of fish required to maintain the run, it has been possible to select that por- tion of the population having the most desirable characteristics. Through selective breeding, it has been possible to develop stocks of salmon that are better adapted to the needs of both fisheries management and commercial aquaculture. Changes in timing of spawning runs through selection have resulted in delayed or advanced fish spawning when water in the spawning streams has cooled or warmed to more desirable temperatures. In some in- stances, fish that are much larger than most have been selectively bred to produce many more eggs than the ancestoral stock. Greater temperature tolerance and disease resistance of selectively bred fish can also increase survival. Rapid growth of selectively bred fish shortens the rearing period so that facilities may be used more efficiently, and earlier maturity de- creases the rearing period for broodfish. Information on selective breeding of cool- and warmwater fish is limited. Some work has been done toward improving the commercial value of these fish, increasing their resistance to low dissolved oxygen concentrations, im- proving feed conversion, and developing hybrid strains. Selective breeding of catfishes is relatively new. Some goals to be achieved by selective breeding include resistance to low dissolved oxygen levels, more efficient food conversion, and development of fish with smaller heads in proportion to body size. Albino channel catfish have been report- ed to possess the smaller head characteristic. However, albino channel cat- fish fry have a significantly lower survival rate than normal fish. The following guidelines should be followed when catfish are managed and selected: 148 FISH HATCHERY MANAGEMENT (1) Avoid inbreeding, which includes father- daughter, mother-son and brother-sister mating. Current practice is to keep the same broodstock 4 to 10 years, with replacement broodstock coming from progeny produced on the farm. Furthermore, a beginning producer may have unknowingly started a broodstock with full brothers and sisters having a narrow genetic base. Catfish should be marked in some manner to identify broodstock for pen mating to avoid inbreeding. The stocks can be clearly identified by heat branding, applied when water temperature is 72°F or above, so that healing proceeds rapidly. (2) Enrich bloodlines through the addition of unrelated stock. This can be effective in correcting deterioration in quality of broodstock common to inbreeding. The need to enrich bloodlines might be suspected if a high percentage of deformed progeny, low hatchability of eggs, low survival of fry, or poor growth becomes evident. (3) Crossbreed unrelated stocks. Stocks orginating from different river systems and commercial sources are usually quite diverse, and may com- bine with resulting hybrid vigor, especially in growth and disease resist- ance. (4) Select broodstock carefully; as males grow faster than females in channel catfish, blue catfish, and white catfish, rigorous selection by grad- ing in ponds probably will result in practically all males. More properly, a random sample should be taken at the first selection at 6 months of age, with selection for growth and broodstock occurring at 18-24 months of age. Select equal numbers of males and females. HYBRIDIZATION AND CROSSBREEDING Hybridization between species of fish and crossbreeding between strains of the same species have resulted in growth increases as great as 100%, im- proved food conversions, increased disease resistance, and tolerance to en- vironmental stresses. These improvements are the result of hybrid vigor — the ability of hybrids or strain crosses to exceed the parents in perform- ance. Most interspecific hybrids are sterile. Those that are fertile often produce highly variable offspring and are not useful as broodstock themselves. Hy- brids can be released from the hatchery if they cause no ecological prob- lems in the wild. Several species of trout have been successfully crossed, the more notable being the splake, a cross between brook and lake trout. Hybridization of the chain pickerel and northern pike in a study in Ohio did not produce hybrid vigor and the resulting offspring grew at an inter- mediate rate to the parents. A cross between northern pike males and muskellunge females has yielded the very successful tiger muskie. BROODSTOCK, SPAWNING, AND EGG HANDLING 149 A hybrid striped bass was developed by fertilizing striped bass eggs with sperm from white bass. The hybrids had faster growth and better survival than striped bass. The chief advantage of the reciprocal hybrid, from white bass eggs and striped bass sperm, is that female white bass are usually more available than striped bass females and are easier to spawn. Under artificial propagation, the reciprocal mature hybrids can be produced in 2 years, while 4—5 years are required to produce hybrids when female striped bass are used. White bass and most male striped bass mature in 2 years, but female striped bass require 4—5 years to mature. Both hybridization and crossbreeding of various species of catfish have been successfully accomplished at the Fish Farming Experimental Station, Stuttgart, Arkansas. Hybrid catfishes have been tested in the laboratory for improved growth rate and food conversion. Two hybrids, the white catfish X channel catfish and the channel catfish x blue catfish, performed well. The channel catfish x blue catfish hybrid had a 22% greater growth rate than the parent channel catfish and 57% greater growth rate than the parent blue catfish. When the hybrids were mated among themselves, spawning usually was incomplete and spawn production was relatively small. Growth of the second generation channel catfish x blue catfish hy- brid was inferior to that of the parent hybrid. Various hybrids of sunfish species also have been successful and some are becoming important sport fish in several states. The most commonly produced hybrid sunfish are crosses of male bluegill x female green sunfish and male redear sunfish x female green sunfish. They are popular for farm- pond stocking because they do not reproduce as readily as the purebred parental stocks and grow much larger than their parents. It is advisable for any hatchery manager to consult a qualified geneticist before starting either a selective breeding or hybridization program. Spawning Obtaining eggs from fish and fertilizing them is known as spawning, egg taking, or stripping. The two basic procedures utilized for spawning fish commonly are referred to as the natural and artificial methods. Natural spawning includes any method that does not entail manually extracting sexual products from the fish. Natural Spawning Method Fish are placed in prepared ponds or allowed to enter channels resembling their natural habitat to carry out their reproductive activities naturally. 150 FISH HAICHERY MANAGEMENT The fish are allowed to prepare nests or spawning sites as they might in the wild. SALMONID FISHES In salmonid culture, spawning channels have been used in conjunction with natural spawning. In a spawning channel, mature fish are allowed to spawn naturally. The channel has a carefully constructed bottom type and a controllable water flow. Typically, the channel has a carefully graded bottom of proper gravel types, approximately 1 foot thick. Over this, there will be a minimum water level of 1.5 to 2.5 feet. The size of gravel used for the spawning or incubation areas should pass a 4-inch screen but not a 0.75-inch screen. Siltation can kill large numbers of eggs and fry so proper silt entrapment devices must be provided. The gravel bottom must be loosened and flushed periodically in order to maintain proper water veloci- ties and percolation through the gravel. Invert controls or sills placed at intervals across the bottom of the channel also are important. These prevent the gravel from shifting downstream and also help to maintain proper percolation of water through the gravel. The density of eggs in a spawning channel is controlled by the spawning behavior of each species. For example, spawning pink salmon use 10 square feet of bottom per pair of fish; sockeye or chum salmon use 20 square feet per pair. Densities of spawners that are too high will lead to wastage of eggs through superimposition of redds (nests). The final number of newly fertilized eggs deposited in a spawning channel will not exceed 200 eggs per square foot of surface area and may be considerably less than this number, even with an optimum density of spawners. A typical spawning channel requires at least 1 cubic foot per second wa- ter flow per foot of channel width during incubation of eggs and fry. The volume of flow should be approximately doubled during the spawning period to provide adult fish with adequate water for excavation of redds. Spawning channels are not suited for small streams or locations with little relatively level land that can be easily shaped with heavy machinery. In general, channels have been most successful with pink, chum, and sockeye salmon. Chinook and coho salmon do not fare as well. Improved results with chinook salmon have been reported when emerging fry are retained in the channel and fed artificial diets prior to their release. Exper- iments with Arctic char suggest that this species also might adapt to spawn- ing channels. WARMWATER FISHES Natural spawning methods are used extensively with warmwater species of fish such as bass, sunfish, and catfish. Pond-water depth is 3-5 feet in the BROODSTOCK, SPAWNING, AND EGG HANDLING 151 middle and 1 foot or less around the perimeter. In the case of bass and sunfish, the males either prepare nesting sites at random in the pond or use gravel nests or beds provided by the fish culturist. Following spawning, the males guard the nests until the eggs hatch and the fry swim up. Fry are left in the pond and reared in the presence of the adults. Less labor is involved in this method but its use usually is restricted to nonpredatory species such as bluegills, because predation by adult fish can be extensive. Other disad- vantages include the possible transfer of disease organisms from broodfish to fry and lack of control over rearing densities. A more popular method involves the transfer of eggs or fry to prepared rearing ponds. This method commonly is used in the culture of bait, forage, tropical, and ornamental fishes, as well as with several predatory species. The production of largemouth bass fry for transfer to rearing ponds should begin with the selection of ponds. A desirable pond is of moderate depth, protected from wind action, and 0.75 to 1.5 acres in size, and does not ordinarily develop weeds or dense phytoplankton blooms. If possible, the pond should be thoroughly dried before it is flooded and stocked. Growth of terrestrial vegetation or a green manure crop will provide food for the fry and inhibit undesirable aquatic plants. Careful attention must be given to oxygen levels if such crops are used, however. It is desirable to flood the pond about 2 weeks before bass fry are expected to begin feeding unless a residual supply of food from a previous cycle is present, as it would be if the pond had been drained and immediately refilled. The 2 weeks provide enough time for natural food organisms to develop for the small bass. Preparation of ponds for production of food organisms is dis- cussed in Chapter 2. Most bass culturists prefer to leave the spawning pond unfertilized to avoid a phytoplankton bloom that will hinder observation of the fish. If there is not ample residual fertility to allow a natural food chain to develop, the pond may be fertilized lightly to produce a zooplankton bloom. The spawning pond can be stocked any time after the last killing frost, and preferably near the average date of spawning activity in previous years. At this time, the broodfish should be examined and the ripe fish stocked in the pond. Ripe females have an obviously distended, soft, pendulous ab- dominal region and a swollen, red, protruding vent. Unripe fish can be re- turned to the holding pond for one to two weeks before being examined and stocked. It is preferable to keep various age groups separate when spawning ponds are stocked, although this often cannot be done at small hatcheries. Generally the older, larger fish ripen and spawn first. The number of bass broodfish to stock depends upon the number of fry desired, the size and condition of the spawners, and the productivity of the 152 FISH HATCHERY MANAGEMENT pond. Federal warmwater hatcheries usually stock 40 to 85 adults per acre. This stocking rate is recommended if the fry are to be transferred to a rear- ing pond. If the fry are to be left in the spawning pond, lower stocking rates of 20 to 30 bass per acre are used. When ripe fish are stocked into clean ponds containing water approxi- mately 65°F, spawning usually begins within 72 hours, and often within 24 hours. Fry will generally hatch within 72-96 hours after spawning, depend- ing on water temperature. They leave the nest after 8 to 10 days and then can be transferred. For handling ease and accuracy in estimating numbers stocked, fry should not be handled until they reach 0.6 to 0.8 inch total length. This may be offset by the greater difficulty of collecting entire schools of small bass, because fry may scatter by the time they are 0.8 inch in length. This size is reached in 3 to 4 weeks after spawning during the first half of the spawning period, and in as little as 10 days during the later portion, depending on water temperatures. If fry are moved while very small, the water must be clear. Phytoplank- ton, rooted vegetation, filamentous algae, and turbidity can limit visibility and reduce capturing success. Larger fry can be harvested quite readily in spite of these adverse conditions, because they migrate to the edge of the ponds, move parallel to the shoreline near the surface, and can be seined or trapped. Smallmouth bass spawning operations are unique in that special equip- ment and techniques often are used for the purpose of collecting fry. The fry do not school well, and scatter in the spawning ponds following swim- up. Smallmouth bass spawning ponds may be equipped with gravelled nest- ing sites or elaborate structures containing gravel in a box enclosed by one to three walls for protection of the nesting fish. Each nesting site is marked by a stake that extends out of the water. The sites should be located 20 to 25 feet apart in the shallow two- thirds of the pond so males will not fight. The spawning pond can be filled as water temperature rises above 60°F and broodfish are stocked at a rate of 40 to 120 adults per surface acre. Smallmouth bass usually spawn about 10 days to two weeks earlier than largemouth, when water temperature reaches 62 to 63°F. They are more prone to desert their nests during cold weather than largemouth bass. If fry are to be transferred, the spawning pond should not be fertilized, because observation of the nesting sites is necessary. When spawning activity is not- ed, nests must be inspected daily with an underwater viewing glass. This consists of a metal tube 3-4 inches in diameter, fitted with a glass in one end. When eggs are noted on a nest, the stake is tagged or marked in some way to indicate when the fry will hatch. After hatching, a retainer screen is placed around the nest before the fry swim up. They will be confined and BROODSTOCK, SPAWNING, AND EGG HANDLING 153 Figure 46. Spawning and rearing of smallmouth bass in ponds, (l) Male small- mouth bass guarding eggs (arrow) on the gravel nest. (2) Nests are inspected daily with an underwater viewing glass, and (3) a retaining screen is placed around the nest after the eggs hatch. (4) The fry are transferred to a rearing pond after they swim up. (FWS photos.) can be readily captured for transfer to rearing ponds (Figure 46). A period of 14 to 21 days normally can be expected between the time eggs are depo- sited and the time fry rise from the nest. Most fish culturists transfer small- mouth bass fry to rearing ponds, although good results have been obtained when they were reared in the spawning pond. An alternative approach to smallmouth bass spawning involves the use of portable nests within a pond. These nests are constructed from 1 x 4-inch lumber, 24 inches square with a window screen bottom. A nest of 1-3-inch diameter rocks, held in a 16 x 16 x 2-inch hardware cloth basket, is placed on the screen frame bottom. Fry are harvested by lowering the pond level, and gently moving the baskets up and down in the water, washing the fry through the rocks and onto the screen bottomed frame. The fry are then rinsed into a container for transfer to a rearing pond. This technique also 154 FISH HATCHERY MANAGEMENT ^ ,r^:' \ Figure 47. Spawning receptacles for channel catfish are placed in the pond before it is filled with water. requires close inspection of nests with an underwater viewer. The method allows the fish culturist to collect eggs, if so desired, for subsequent hatch- ing under controlled conditions. It has the added advantage of allowing the culturist to respawn broodfish during the height of the season. Culture of bluegills and other sunfishes is relatively simple. The spawning-rearing pond method almost always is used for culturing these species, although a few hatcheries transfer fry to rearing ponds. Best spawning success with bluegills is obtained by using mature broodfish weighing 0.3 to 0.6 pound. However, good production has been obtained with 1-year-old fish averaging 0.10—0.15 pound at spawning time. When broodstock of this latter size is used, an increased number of fish per acre is needed to adequately stock the pond. Use of yearling broodstock gen- erally results in less uniform spawning, which tends to cause greater size variation in the fingerlings produced. Bluegills spawn when water tempera- tures approach 80°F and several spawns can be anticipated during the sum- mer. Catfish generally are spawned by either the open- pond or pen method. In the open-pond method, spawning containers such as milk cans, nail kegs, or earthenware crocks, are placed in the pond with the open end to- ward the center of the pond (Figure 47). It is not necessary to provide a spawning receptacle for each pair of fish, because not all fish will spawn at the same time. Most culturists provide two or three receptacles for each four pairs of fish. Fish will spawn in containers placed in water as shallow as 6 inches and as deep as 5 feet. The receptacles are checked most easily if they are in water no deeper than arm's length. Frequency of examination of spawning containers depends on the BROODSTOCK, SPAWNING, AND EGG HANDLING 155 number of broodfish in the pond and the rate at which spawning is prog- ressing. In checking a container, the culturist gently raises it to the surface. If this is done quietly and carefully, the male usually is not disturbed. Cau- tion should be used, because an attacking male can bite severely. If the wa- ter is not clear, the container can be slowly tilted and partly emptied. Catfish eggs may be handled in different ways. The eggs may be re- moved, or left in the spawning pond to hatch and the fry reared in the ponds. Removal of the eggs has several advantages. It minimizes the spread of diseases and parasites from adults to young, and provides for egg disinfection. The eggs are protected from predation and the fry can be stocked in the rearing ponds at known rates. The pen method of spawning catfish utilizes pens about 10 feet long and 5 feet wide located in a row in the spawning ponds (Figure 48). They are constructed of wood, wire fencing, or concrete blocks. They should be en- closed on all four sides but the bank of the pond may be used as one side. The sides should be embedded in the pond bottom and extend at least 12 inches above the water surface to prevent fish from escaping. Water should be 2-3 feet deep. Location of the spawning container in the pen is not critical, but gen- erally it faces away from the pond bank. Broodfish are sexed and paired in the pens. Usually the best results occur when the male is equal in size to, or slightly larger than, the female. This discourages the female from eating the eggs that are being guarded by the male. After spawning, eggs and parent fish may be removed and another pair placed in the pen. Some- times, the female is removed as soon as an egg mass is found, and the male is then allowed to hatch the eggs. Usually, containers are checked daily and the eggs removed to a hatching trough. A male may be used to spawn several females. Figure 48. Channel catfish spawning pens. Note spawning receptacle (arrow). (FWS photo.) 156 FISH HATCHERY MANAGEMENT The pen method has several advantages. It provides close control over the time of spawning, allows the pairing of selected individuals, facilitates removal of spawned fish from the pond, protects the spawning pair from intruding fish, and allows the injection of hormones into the broodfish. The aquarium method of spawning catfish is a modification of the pen method. A pair of broodfish is placed in a 30- to .50-gallon aquarium with running water. The broodfish are induced to spawn by the injection of hor- mones. Tar-paper mats are placed on the bottom of the aquarium. As the eggs are deposited and fertilized, they form a large gelatinous mass, and adhere to the mat. The eggs readily can be removed with the mat. It is an intensive type of culture; many pairs of fish can be spawned successfully in a single aquarium during the breeding season. Each spawn is removed im- mediately to a hatching trough for incubation. In methods involving the use of hormones, only females ready to spawn should be used. Males need not be injected with hormones, but should be about the same size or larger than the females with which they are paired. If the male attacks the female, he should be removed until after the female has been given one to three additional hormone injections. He then may be placed with the female again. Males may be left to attend the eggs in the aquarium or, preferably, the eggs are removed to a hatching trough. Striped bass have been spawned in circular tanks. This method generally requires a water flow of 3 to 10 gallons per minute per tank. Six-foot diam- eter tanks are most desirable. Broodfish are injected with hormones and at least two males are put in a tank containing one female. After spawning, the broodfish are removed. Striped bass eggs are free-floating, and if the males have participated in spawning, the water will appear milky. The eggs can be left circulating in the tank until they hatch or removed with a siphon to aquaria for hatching. Some egg loss can be expected due to mechanical damage if they are transferred from tank to aquaria. When fer- tilized eggs are allowed to hatch in the tank, the fry will become concen- trated around the edge of the tank after 4 or 5 days and they can then be dipped out and transferred to rearing facilities. Artificial Spawning Method The artificial method of spawning consists of manually stripping the sex products from the fish, mixing them in a container, and placing the fertil- ized eggs in an incubator. The following description of egg stripping and fertilization is widely applicable to many species of fish, including coolwa- ter and warmwater species (Figure 49). Any spawn- taking operation should be designed to reduce handling of the fish. Anesthetics should be used when possible to reduce stress. In hand- stripping the eggs from a female, the fish is grasped near the head with the right hand, and the left hand grasps the body just above the tail. BROODSTOCK, SPAWNING, AND EGG HANDLING 157 Figure 49. Equipment used for spawning wild coolwater fishes (trap net shown in background). The males and females are held separately in holding tanks con- taining an anesthetic (A, B). A bench with a spawning pan (C) is provided for the spawn taker. (FWS photo.) The fish is then held with the belly downward over a pan, and the eggs are forced out gently by a massaging movement beginning forward of the vent and working back toward it. Care should be taken to avoid putting pres- sure too far forward on the body as there is danger of damaging the heart or other organs (Figure 50). After the eggs have been extruded, a small amount of milt (sperm) is added from a male fish. Milt is expressed from a ripe male in much the same manner as the eggs are taken from a female (Figure 5l). If either eggs or milt do not flow freely, the fish is not suffi- ciently ripe and should not be used. The fish should be examined frequent- ly, as often as twice a week, to determine ripeness. Fish rarely spawn of their own accord under hatchery conditions, and, if they are not examined for ripeness frequently, overripe eggs will result. Muskellunge, however, will often spawn on their own accord. The two generally accepted procedures for handling eggs during fertili- zation are often referred to as the wet and dry methods. In the dry method of fertilization, water is not introduced before the eggs are expressed into the pan, and all equipment is kept as dry as possible. Sperm and eggs are thoroughly mixed and usually left undisturbed for 5 to 15 minutes before 158 FISH HATCHERY MANAGEMENT Figure 50. Eggs being spawned from a northern pike female. (FWS photo. Figure 51. Sperm being expressed from a northern pike male. (FWS photo. BROOUSTOCK, SPAWNING, AND EGG HANDLING 159 water is added to wash the eggs for incubation. In the wet method, a pan is partially filled with water before the eggs are expressed from the female fish. The milt from a male is then added. Because the sperm will live less than 2 minutes in water after being activated, considerable speed is neces- sary by the spawn takers. The dry method generally is accepted as the best procedure. Eggs are washed or rinsed thoroughly after they have been fertilized and before they are placed in the incubator. In some species, the eggs are allowed to water- harden before being placed in an incubator. Water- hardening is the process by which water is absorbed by the eggs and fills the perivitelline space between the shell and yoke, causing the egg to become turgid. Precau- tions should be taken to protect eggs from exposure to direct rays of bright light, because both sunlight and artificial light are detrimental. Some species, such as walleye and northern pike, have eggs that are ex- tremely adhesive. Often during the water- hardening process of adhesive eggs, an inert substance is added to prevent the eggs from sticking togeth- er. Starch, black muck, clay, bentonite clay, and tannin have been used as separating agents. Starch, because it is finely ground, does not have to be specially prepared, but muck and regular clay must be dried and sifted through a fine screen to remove all coarse particles and then sterilized be- fore they can be used. Starch or clay first must be mixed with water to the consistency of thick cream. One or two tablespoons of this mixture is ad- ded to each pan of eggs after fertilization is completed. When the separat- ing agent has been mixed thoroughly with the eggs, the pan is allowed to stand for a minute. Water is then added, the separating agent is washed from the eggs, and the eggs placed in a tub of water to harden. Constant stirring during water hardening helps prevent clumping. The water should be changed at least once an hour until the eggs are placed in the hatchery. Striped bass also may be hand-stripped as an alternative to tank spawn- ing. Both males and females of this species usually are injected with hor- mones, as described in a later section of this chapter. An egg sample should be taken and examined between 20 and 28 hours after a hormone injection. Egg examination and staging requires microscopic examination. The catheter used for extraction of the egg sample is made of glass tub- ing, 3 millimeter O.D., with fire- polished ends. The catheter is inserted ap- proximately 2 inches into the vent and removed with a finger covering the end of the tube to create a vacuum that holds any eggs in place in the tube. Extreme care is needed while the catheter is inserted into the ovary. The catheter should be instantly removed if the fish suddenly thrashes; such thrashing usually is immediately preceded by a flexing of the gill cov- ers. Careful manipulation will permit the catheter to be inserted into the vent with a minimum of force, preventing damage to the sphincter muscles. If these muscles are torn, eggs at the posterior end of the ovary will water- harden. The plug thus formed will prevent the flow of eggs. 160 FISH HATCHERY MANAGEMENT The egg sample is placed on a clean glass slide with a small amount of water. Magnification of 20 x provides a sufficiently wide field for examina- tion of several eggs with enough magnification for detailed viewing of indi- vidual eggs. Egg samples should be taken between 20 and 28 hours after hormone in- jection. Approximately 16 hours are required for the effects of the hormone to be detected in egg development. Early in the spawning season, it is advisable to wait 28 hours before sampling because it usually requires about 40 hours for ovulation, and eggs taken more than 15 hours before ovulation cannot be accurately staged. Near the peak of the natural spawn- ing season, ovulation may occur within 20 hours following injection and it is prudent to sample earlier. It is impractical to predict ovulation in striped bass that are more than 15 hours from spawning as the eggs are very opaque and no difference can be detected between 30- hour and 17- hour eggs. If opaque eggs are found, the ovary should be resampled 12 hours later. At about 15 hours before ovulation, the ova assume a grainy appearance and minute oil globules appear as light areas in individual ova. This is the first visible indication of ripening. At 14 hours, the globules in some of the ova have become somewhat en- larged while very small globules are evident in others. No distinct progress can be detected in a few eggs. This mixed development may be confusing, but in order to avoid over-ripeness, a prediction of spawning time should be based primarily on the most advanced eggs. Uneven maturation persists to some degree until approximately the 10- hour stage, after which develop- ment progresses more uniformly. At 13 hours, the majority of ova will have enlarged globules and cleared areas occupy over one- half of the surface of most eggs. At 12 hours, the first evidence of polarization of what eventually will be- come the oil globule is apparent. The small globules begin fusion to form a single globule. At 10 hours, polarization of the oil globule is complete. The entire egg is more translucent than in earlier stages. At 9 hours, eggs begin to show more transparency in the yolk, although the majority of the yolk remains translucent. It is difficult to describe differences between eggs that are 6, 7, or 8 hours from spawning. There is a continued clearing of the nucleus, and with experience, the worker will be able to pinpoint the exact stage. How- ever, to avoid over- ripeness, it is best to classify eggs in any of these stages as the 6-hour stage and attempt to hand-strip the eggs. From 5 hours until ovulation, the ova continue to clear; at 1 hour, no opaque areas can be detected. For more detailed information describing this process consult the publication by Bayless 1972 (Figures 52-55). BROODSTOCK, SPAWNING, AND EGG HANDLING 161 •*_'^^'' k i * Immature Eggs 15 hrs. before Ovulation 14 hrs. before Ovulation 13 hrs. before Ovulation 12 hrs. before Ovulation 11 hrs. before Ovulation Figure 52. Development of striped bass eggs from immaturity to 1 1 hours before ovulation. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources Department.) 162 FISH HATCHERY MANAGEMENT 10 hrs. before Ovulation Polarization Complete 9 hrs. before Ovulation Nucleus Clearing i C Ji^ 8 hrs. before Ovulation ^W. 7 hrs. before Ovulation o 6 hrs. before Ovulation 5 hrs. before Ovulation Figure 53. Development of striped bass eggs from 10 to 5 hours before ovula- tion. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources Department.) BROODSTOCK, SPAWNING, AND EGG HANDLING 163 4 hrs. before Ovulation 3 hrs. before Ovulation V 2 hrs. before Ovulation I V .. 1 hr. before Ovulation ^ Ripe Eggs at Ovulation \ Ripe Eggs at Ovulation (SOX) Figure 54. Development of striped bass eggs from 4 hours before ovulation to ripeness. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources Department.) 164 FISH HATCHERY MANAGEMENT Overripe Eggs 1 hr. (50X) Note Breakdown at Inner Surface of Chorion / V Overripe Eggs 2 hrs. (50X) Note Deterioration Confined to One-Half of Egg Overripe Eggs 1^2 hrs. (50X) Breakdown at Inner Surface of Chorion Persists Overripe Egg 16 hrs. (20X) (Dark Areas Appear White Under Microscope) Figure 55. Development of striped bass eggs that become overripe before ovula- tion. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources Department.) As ovulation occurs, eggs of striped bass become detached from the ovarian tissue. They are deprived of parental oxygen supply, and anoxia can result in a short period of time if the eggs remain in the body. (This also is true for grass carp.) If eggs flov^ from the vent when pressure is ap- plied to the abdomen, at least partial ovulation has occurred. The max- imum period between ovulation and overripeness is approximately 60 minutes. The optimum period for egg removal is between 15 and 30 minutes following the first indication of ovulation. Eggs obtained 30 minutes after initial ovulation are less likely to hatch. Prior to manual stripping, female striped bass should be anesthetized with quinaldine sprayed onto the gills at a concentration of 1.0 part per BROODSTOCK, SPAWNING, AND EGG HANDLING 165 thousand. The vent must be covered to prevent egg loss. Fish will become sufficiently relaxed for removal of eggs within 1 to 2 minutes. Workers should wear gloves to prevent injury from opercular and fin spines. Strip- ping follows the procedure previously described in this chapter. Because the broodfish of anadromous species of Pacific salmon die after spawning, no advantage is obtained by stripping the female. Females are killed and bled. Bleeding can be accomplished by either making an inci- sion in the caudal peduncle or by cutting just below the isthmus and between the opercula to sever the large artery leading from the heart to the gills. The females are allowed to bleed for several minutes before being spawned. A mechanical device is in common use that effectively kills and bleeds the fish by making a deep cut through the body behind the head. Bleeding reduces the chance of blood mixing with the eggs and reducing fertilization. The point of the spawning knife is placed in the vent to prevent the loss of eggs and the fish is lifted by the gill cavity and held vertically over a bucket, such that the vent is 7-I inch above the lip of the bucket. The fish can be held securely in this position by bracing the back of the fish between the spawner's knees. An incision is made from the vent to a point just below the ventral fin, around the ventral fin, back to the center line, and upward to a point just beneath the gill cavity. If the fish is ripe, most of the eggs will flow freely into the bucket (Figure 56). The remaining ripe eggs can be dislodged by gently shaking the viscera. If the fish is not ripe, gentle shaking will not dislodge the eggs and such females should be discarded. Eggs that can only be dislodged by greater force will be underdeveloped and infertile. The spawning knife needs a sharp blade, but should have a blunt tip to avoid damage to the eggs during the incision. Linoleum knives have been used for this purpose, but personal preference usually determines the choice of the knife. Male salmon also are killed prior to spawning. Milt is hand stripped directly onto the eggs in the bucket. The eggs and milt are gently mixed by hand. In the case of Atlantic salmon or steelhead, which may return to spawn more than once, females should not be killed to obtain eggs. A female fish can be spawned mechanically by placing her into a double walled, rubber sack with the tail and vent of the fish protruding. The sack can be adjust- ed to fit each fish. Water entering between the walls of the sack causes a pressure against the entire fish, and will express the eggs if they are ripe. Female fish handled in this way seem to recover more rapidly than from other methods of stripping. Milt is collected from the males and stored in test tubes. A male fish is held upside down and the milt is gently pressed out and drawn into a glass tube with suction. Reduction of damage to broodstock and increased efficiency are factors of prime importance in any spawning operation. The use of air pressure 166 FISH HATCHERY MANAGEMENT systems, as introduced by Australian workers and used on some trout species in this country, have made spawning fast, easy, and efficient (Fig- ure 57). Two to four pounds of air pressure injected into the body cavity by means of a hollow needle will expel the eggs. The needle is inserted in the area between the pectoral and ventral fins midway between the mid- ventral line and the lateral line. The possibility of damage to the kidney by needle puncture is reduced if the posterior section of this area is used. The needle should be sterilized in alcohol for each operation to reduce the pos- sibility of infection. It is imperative that a female be ripe if the eggs are to flow freely. When a fish is held in the normal spawning position, a few eggs should flow from the fish without pressure on the abdomen. It is important that the fish be relaxed before the air pressure method is attempted. An anesthetic should be used. The fish should be rinsed and wiped fairly dry to prevent anesthetic dripping into the egg- spawning pan. Air should be removed from the body cavity before the fish is returned to the water. This is best done by installing a two-way valve and a suction line to the needle. A supplemental line may be used to draw off the air by mouth, or the air may be forced out by hand when a check is made for remaining eggs, although these methods are generally not as effective. Figure 56. Spawning Pacific salmon. Left, female is opened with a spawning knife (cutting edge indicated by arrow). Right, milt is hand-stripped from a male directly onto the eggs. BROODSTOCK, SPAWNING, AND EGG HANDLING 167 Figure 57. Spawning of salmonids with air pressure. Urine-free sperm can be collected through a pipette inserted about 0.5 inch into the sperm duct. If the male trout is gently stripped by hand, suc- tion on the pipette will draw clean sperm out of the fish. Sperm and eggs are then mixed together. Factors Affecting Fertilization Several factors may have an adverse affect on fertilization during the spawning process at a hatchery. The contamination of either eggs or sperm can result in low levels of fertility. In the case of most salmonids, pro- longed exposure of either sperm or eggs to water will reduce fertility. Sperm mixed with water are highly active for up to 15 seconds; after that, motility declines and usually no activity is recorded after 2 minutes. Eggs rapidly begin absorption of water shortly after contact with it and may be- come nonviable if they have not been fertilized. 168 FISH HATCHERY MANAGEMENT The activation of sperm, however, does require exposure to either water or female ovarian fluid. The sperm are active for a longer period when di- luted with an isotonic salt solution or ovarian fluid than they are in water. Sperm activated in ovarian fluid without the addition of water will fertilize the egg readily and have the additional benefit of prolonged viability. This is of particular importance when large volumes of eggs must be fertilized with small quantities of sperm. Contaminants associated with the spawning operation also may have a significant effect on egg fertility. Although skin mucus itself has not been shown to reduce fertility, there is a good possibility that it can carry a con- taminant such as the anesthetic used. Therefore, mucus should be kept out of the spawning pan. Occasionally, blood will be ejected into the spawning pan from an injured female; fish blood clots quickly and may plug the mi- cropyle of the eggs, through which the sperm must enter. Occasionally, broken eggs will result from the handling of females either prior to or dur- ing spawning. Protein from broken eggs will coagulate and particles of coagulated protein may plug the micropyle, thus reducing fertilization. If large numbers of ruptured eggs occur, fertility sometimes may be increased by placing the eggs in a 0.6% salt solution. This will cause the protein to go back into solution. Fertilization can be estimated by microscopically examining a sample of eggs during the first day or two after fertilization. The early cell divisions form large cells (blastomeres) that readily can be distinguished from the germinal disk of unfertilized eggs at 10 x magnification. To improve the examination of embryos, a sample of eggs can be soaked in a 10% acetic acid solution for several minutes. Unfertilized germinal disks and the em- bryos of fertilized eggs will turn an opaque white and become visible through the translucent chorion. A common procedure is to examine the eggs when the four- cell stage is reached. The rate of embryonic develop- ment will vary with temperature and the species of fish. This method may not be suitable on eggs of some warmwater species. Gamete Storage Sperm of rainbow trout and northern pike have been stored and transport- ed successfully. The sperm, with penicillin added, is placed in dry, sterile bottles and then sealed. The temperature is maintained at approximately 32°F in a thermos containing finely crushed ice. Undiluted brook trout sperm has been stored with some success for as long as 5 days. The sperm should be taken under sterile conditions, kept free from all contaminants, chilled immediately to 35°F, and refrigerated until needed. This procedure also has been used to store rainbow trout sperm for a 7-day period. Some workers, however, prefer to store brook trout milt for not more than 24 BROODSTOCK, SPAWNING, AND EGG HANDLING 169 hours at 34°F and to warm the stored milt to the ambient water tempera- ture before fertilization. Cryopreservation (freezing) of sperm from several warm- and coldwater species has been successful for varying length of times and rates of fertility. These procedures generally require liquid nitrogen and extending agents, and are reviewed by Horton and Ott (1976). At 46° to 48°F, sockeye salmon eggs with no water added maintained their fertility for 12 hours after being stripped, and a few were still fertile after 175 hours. Sockeye milt maintained its fertility for 11 hours and fertil- ized a few eggs after 101 hours. Pink salmon eggs have maintained their fertility for 8 hours, and some were still fertile at 129 hours. Milt of pink salmon maintained its fertility for 33 hours after being stripped from the male, and fertilized 65"i of the eggs after 57 hours; none were fertilized after 81 hours. Some fish culturists have obtained 90"(i fertilization with pink salmon eggs and sperm stored for periods up to 20 hours at 43°F. Storage of chum salmon eggs for 108 hours at temperatures of 36° to 42°F maintained an 80"() fertility when fertilized with fresh sperm. Chum salmon sperm stored under similar conditions for 36 hours maintained a 90% fertil- ity when applied to fresh eggs. Experiments with fall chinook salmon eggs and sperm have shown that the eggs are more sensitive to storage time and temperature than sperm. After 48 hours storage at 33°F, egg mortality was approximately 47%. Mor- tality was 100"o after 48 hours storage at 56°F. Forty-eight-hour storage of sperm at 56°F resulted in about a 12"n mortality. The stored eggs were fer- tilized with freshly collected sperm and the stored sperm was used to fertil- ize freshly spawned eggs. Anesthetics Anesthetics relax fish and allow increased speed and handling ease during the spawning operation. In general, the concentration of the anesthetic used must be determined on a trial and error basis with the particular species of fish being spawned, because such factors as temperature and chemical composition of the water are involved. Fish may react differently to the same anesthetic when exposed to it in a different water supply. Be- fore any anesthetic is used, it is advisable to test it with several fish. At least 15 anesthetic agents have been used by fish culturists. Of the anesthetics reported, quinaldine (2-methylquinoline), tricaine methane sul- fonate (MS-222), and benzocaine are the most popular fish anesthetics currently in use. Only MS-222 has been properly registered for such use. There are various stages of anesthesia in fish (See Chapter 6, Table 39). When placed in the anesthetic solution, the fish often swim about for several seconds, attempting to remain in an upright position. As they lose 170 FISH HATCHERY MANAGEMENT equilibrium they become inactive. Opercular movement decreases. When the fish can no longer make swimming movements, the respiration becomes quite rapid, and opercular movements are difficult to detect. At this point, the fish may be removed from the water and spawned. If gasping and mus- cular spasms develop while a fish is being spawned, it should be returned to fresh water immediately. If the fish has been overexposed to the drug, respiratory movements will cease. Rainbow trout placed in a 264 parts per million solution of MS-222 require 30 to 45 seconds to become relaxed. Concentrations of 0.23 gram of benzocaine per gallon of water or 0.45 gram of MS-222 per gallon of water are commonly used to anesthetized fingerling Pacific salmon. Use of MS-222 as an anesthetic for spawning operations is widespread. However, concentrations as low as 18.9 parts per million have reduced sperm motility. Therefore, the anesthetizing solution should not come in contact with the reproductive products. Adult Pacific salmon have been anesthesized with a mixture of 40 parts per million MS-222 and 10 parts per million quinaldine. Carbon dioxide at concentrations of 200-400 parts per million, is used in some instances for calming adult Pacific salmon. It can be dispersed into the tank from a pressurized cylinder through a car- borundum stone. Both ether and urethane have been used in the past, but both should be discontinued due to the high flammability of ether and the possible carci- nogenic properties of urethane. Artificial Control of Spawning Time Management requirements and availability of hatchery facilities often make it desirable to spawn fish at times different from the natural spawning date. Several methods have been used with success. PHOTOPERIOD Controlled light periods have been used with several species of fish to manipulate spawning time. The Fish and Wildlife Service's Salmon Cultur- al Laboratory, Entiat, Washington, conducted a 3-year study to determine the effect of light control on sockeye salmon spawning. The study showed that salmon exposed to shortened periods of light spawn appreciably ear- lier. Egg mortalities can be significantly higher, however. Light, not tem- perature, is apparently the prime factor in accelerating or retarding sexual maturation in this species; although temperatures varied from year to year, salmon receiving no light control spawned at essentially the same time each year. BROODSTOCK, SPAWNING, AND EGG HANDLING 171 Artificial light has been used successfully to induce early spawning in brook, brown, and rainbow trout. The rearing facilities are enclosed and lightproof, and all light is provided by overhead flood lamps. Broodstock should have had at least one previous spawning season before being used in a light-controlled spawning program. Eggs produced generally are small- er and fewer eggs are produced per female. The following light schedule is used to induce early spawning in trout. An additional hour of light is pro- vided each week until the fish are exposed to nine hours of artificial light in excess of the normal light period. The light is maintained at this schedule for a period of four weeks and then decreased one hour per week until the fish are receiving four hours less light than is normal for that period. By this schedule, the spawning period can be advanced several months. Use of broodfish a second consecutive year under light-controlled conditions does not always prove satisfactory, and a controlled-light schedule must be started at least six months prior to the anticipated spawning date. Most attempts at modifying the spawning date of fish have been to accelerate rather than retard the maturation process. However, spawning activity of eastern brook trout and sockeye salmon have been delayed by extending artificial light periods longer than normal ones. Temperature and light control are factors in manipulating spawning time of channel cat- fish. Reducing the light cycle to 8 hours per day and lowering the water temperature by I4°F will delay spawning for approximately 60-150 days. The spawning period of largemouth bass has been greatly extended by the manipulation of water temperature. For example, moving fish from 67° to 61°F water will result in a delayed spawning time. HORMONE INJECTION Spawning of warmwater and coolwater species can be induced by hormone injection. This method has not proven to be as successful with coldwater species. Fish must be fairly close to spawning to have any effect, as the hormones generally bring about the early release of mature sex products rather than the promotion of their development. Both pituitary material ex- tracted from fish and human chorionic gonadotropin have been used suc- cessfully. Use of hormones may produce disappointing results if broodfish are not of high quality. Under such conditions, a partial spawn, or no spawn at all, may result. It also appears that some strains of fish do not respond to hor- mone treatment in a predictable way, even when they are in good spawn- ing condition. Injection of salmon pituitary extract into adult salmon hastens the de- velopment of spawning coloration and other secondary sex characteristics, 172 FISH HATCHERY MANAGEMENT ripens males as early as three days after injection, and advances slightly the spawning period for females, but may lower the fertility of the eggs. Injec- tion of mammalian gonadotropin into adult salmon fails to hasten the development of spawning characteristics, and there is no change in the time of maturation. Acetone-dried fish pituitaries from common carp, buffalo, flathead cat- fish, and channel catfish have been tested and all will induce spawning when injected into channel catfish (Figure 58). Carp pituitary material also induces ovulation in walleye. The pituitary material is finely ground, suspended in clean water or saline solution, and injected intraperitoneally at a rate of two milligrams of pituitary per pound of broodfish (Figure 59). One treatment is given each day until the fish spawns or shows resistance to the hormone. Generally the treatment should be successful by the third or fourth day. Goldfish have been injected with human chorionic gonadotropin (HCG) in doses ranging from 10 to 1,600 International Units (lU) but only those females receiving 100 lU or more have ovulated. One hundred lU of HCG is comparable to 0.5 milligram of acetone-dried fish pituitary. In some in- stances goldfish will respond to two injections of HCG as low as 25 lU, when given 6 days apart. White crappies injected with 1,000, 1,500, and Figure 58. Collection of pituitary gland (arrow) from a common carp head. The top of the head has been removed to expose the brain. (Fish Farming Experi- mental Station, Stuttgart, Arkansas.) BROODSTOCK, SPAWNING, AND EGG HANDLING 173 Figure 59. Injection of hormone intraperitoneally into female channel catfish. (Fish Farming Experimental Station, Stuttgart, Arkansas.) 2,000 lU spawned three days after they were injected. Female crappies in- jected with 1,000 lU spawned 2 days later at a water temperature of 62°F. Channel catfish, striped bass, common carp, white crappies, and large- mouth bass, injected with 1,000 to 2,000 lU of HCG, also have been in- duced to spawn. Hormone injection of striped bass has proven to be effective for spawn- ing this species in rearing tanks. Females given single intramuscular injec- tions at the posterior base of the dorsal fin with 125 to 150 lU of HCG per pound of broodfish show the best results. Multiple injections invariably result in premature expulsion of the eggs. Injection of males is recommend- ed for obtaining maximum milt production. Fifty to 75 lU per pound of broodfish should be injected approximately 24 hours prior to the anticipat- ed spawning of the female. Channel catfish also can be successfully induced to spawn by intraperi- toneal injections of HCG. One 800- lU injection of HCG per pound of broodfish normally is sufficient. Two 70-IU injections of HCG per pound of broodfish, spaced 72 hours apart, will induce ovulation in walleyes. Egg Incubation and Handling Eggs of commonly cultured species of fish are remarkably uniform in their physiology and development. A basic understanding of the morphology and physiological processes of a developing fish embryo can be of value to 174 FISH HATCHERY MANAGEMENT the fish culturist in providing an optimum environment for egg develop- ment. Egg Development During oogenesis, when an egg is being formed in the ovary, the egg's fu- ture energy sources are protein and fat in the yolk material. At this early stage, the egg is soft and low in water content, and may be quite adhesive. The ovum, or germ cell, is enclosed in a soft shell secreted by the ovari- an tissue. This shell, or chorion, encloses a fluid-filled area called the perivitelline space. An opening (the micropyle) provides an entryway for the sperm. Inside the perivitelline space is a vitelline membrane; the yolk is retained within this membrane (Figure 60). Trout eggs are adhesive when first spawned because of water passing through the porous shell. This process is called water- hardening, and when it is complete, the egg no longer is sticky. The egg becomes turgid with water, and the shell is separated from the yolk membrane by the perivitelline space filled with fluid. This allows the yolk and germinal disc to rotate freely inside the egg, with the disc always being in an upright position. The micropyle is open to permit entry of the sperm when the egg is first spawned. As the egg water- hardens, the micropyle closes and there is no MICROPYLE VITELLINE MEMBRANE YOLK GERMINAL DISC SHELL PERIVITELLINE SPACE OIL DROPLET Figure 60. Diagrammatic section of a fertilized trout egg. (Source: Davis 1953.) BROODSTOCK, SPAWNING, AND EGG HANDLING 175 further chance for fertiUzation. In salmonids, water- hardening generally takes from 30 to 90 minutes, depending on water temperature. The sperm consists of a head, midpiece, and tail, and is inactive when it first leaves the fish; on contact with water or ovarian fluid, it becomes very active. Several changes take place when the sperm penetrates the egg. Nu- clear material of the egg and sperm unite to form the zygote. This zygote, within a few hours, divides repeatedly and differentiates to form the em- bryo. Schematic drawings of trout and salmon egg development (Figure 6l) can be applied in general to other species as well. SENSITIVE STAGE Trout and salmon eggs become progressively more fragile during a period extending roughly from 48 hours after water- hardening until they are eyed. An extremely critical period for salmonid eggs exists until the blastopore stage is completed. The eggs must not be moved until this critical period has passed. The eggs remain tender until the eyes are sufficiently pigment- ed to be visible. EYED STAGE As the term implies, this is the stage between the time the eyes become visible and hatching occurs. During the eyed stage, eggs usually are shocked, cleaned, measured and counted, and shipped. At hatching, the weight of the sac fry increases rapidly. Water content of the fry increases until approximately 10 weeks after hatching, when it is approximately 80"(i of the body weight. Water content remains fairly uni- form in a fish from this point on. As the embryo develops, there is a gradual decrease in the protein con- tent of the egg. The fat content remains fairly uniform, but there is a gra- dual decrease in relative weight of these materials as water content increases. There is no significant difference in the chemistry of large and small eggs. However, several studies have shown that larger eggs generally produce larger fry and this size advantage continues throughout the growth and development of the fish. Enumeration and Sorting of Eggs A number of systems for counting eggs are in general use. Enumeration methods should be accurate, practical, and should not stress the eggs. 176 FISH HATCHERY MANAGEMENT .GERMINAL DISC A. ONE DAY AFTER FERTILIZATION, 55.9°F AVERAGE TEMPERATURE (23.9 T.U.). BLASTODISC B. TWO DAYS AFTER FERTILIZATION, 53.9°F AVERAGE TEMPERATURE (43.9 T.U.). EDGE OF BLASTODISC EMBRYO C. FIVE DAYS AFTER FERTILIZATION, 51 .7°F AVERAGE TEMPERATURE (98.4 T.U.). Figure 61. Schematic development of trout and salmon eggs. One temperature unit (TU) equals 1°F above 32°F for a 24-hour period. See Glossary: Daily Tem- perature Unit. (Source: Leitritz and Lewis 1976.) When small numbers of eggs are involved, counting can be done by hand or by the use of a counting board that will hold a known number of eggs. A paddle- type egg counter is constructed of plexiglass by drilling and countersinking a desired number of holes spaced in rows. The diameter of the hole will depend on the size of eggs being counted. The paddle is BROODSTOCK, SPAWNING, AND EGG HANDLING 177 THICKENED EDGE OF BLASTODERM EMBRYO D. SIX DAYS AFTER FERTILIZATION, 51.5°F AVERAGE TEMPERATURE (117.0 T.U.). EDGE OF BLASTODERM EMBRYO E. SEVEN DAYS AFTER FERTILIZATION, 51.2°F AVERAGE TEMPERATURE (134.4 T.U.). LIP OF BLASTOPORE F. EIGHT DAYS AFTER FERTILIZATION, 51.7°F AVERAGE TEMPERATURE (157.5 T.U.). Figure 61. Continued. 178 FISH HATCHERY MANAGEMENT SOMITE G. NINE DAYS AFTER FERTILIZATION, 51.4°F AVERAGE TEMPERATURE (174.5 T.U.). FUTURE OPTIC LOBE HIND BRAIN H. TEN DAYS AFTER FERTILIZATION, 51,5°F AVERAGE TEMPERATURE (195,4 T.U.). OLFACTORY CAPSULE FUTURE OPTIC LOBE HIND BRAIN I. ELEVEN DAYS AFTER FERTILIZATION, 51, 7T AVERAGE TEMPERATURE (216,6 T,U,). Figure 61. Continued. BROODSTOCK, SPAWNING, AND EGG HANDLING 179 OPTIC LOBE OTIC CAPSULE FUTURE PECTORAL FIN J, THIRTEEN DAYS AFTER FERTILIZATION, 51. 7T AVERAGE TEMPERATURE (225.8 T.U.) .MYOMERE NOTOCHORD -VENT K. FOURTEEN DAYS AFTER FERTILIZATION, 51.5°F AVERAGE TEMPERATURE (273.2 T.U.). FUTURE CAUDAL FIN ANAL FIN FOLD ORSAL FIN FOLD MYOMERE FUTURE ANAL FIN L. SIXTEEN DAYS AFTER FERTILIZATION, 51. 7T AVERAGE TEMPERATURE (315.9 T.U.). Figure 61. Continued. 180 FISH HATCHERY MANAGEMENT HIRD VENTRICLE QPTIC LOBE ENS OF EYE DOE OF MANDIBLE IND BRAIN OTIC CAPSULE ,GILL BAR FUTURE PECTORAL FIN HEAD-VENTRA M. SIXTEEN DAYS AFTER FERTILIZATION, 51. 7T AVERAGE TEMPERATURE (315.9 T.U.). N. EIGHTEEN DAYS AFTER FERTILIZATION, 51.8°F AVERAGE TEMPERATURE (357.4 T.U.). ORSAL FIN CEREBRAL HEMISPHERE, OPTIC LOBE HIND BRAIN FUTURE FOURTH VENTRICLE FUTURE CEREBELLUM, ORSAL FIN FOLD NAL FIN NAL FIN FOLD VENTRAL FIN 0. TWENTY-SIX DAYS AFTER FERTILIZATION, 51. 2T AVERAGE TEMPERATURE (500.4 T.U.). Figure 61. Continued. dipped into the egg mass and eggs fill the holes as the paddle is lifted through them. Three commonly used procedures for counting trout and salmon eggs are the Von Bayer, weight, and water-displacement methods. The Von Bayer method employs a 12- inch, V-shaped trough (Figure 62). BROODSTOCK, SPAWNING, AND EGG HANDLING 181 NUMBER OF EGGS 12 INCH TROUGH NUMBER OF EGGS PER OUNCE Figure 62. Diagrammatic plan view of a Von Bayer V-trough for estimating numbers and volumes of eggs. 182 FISH HATCHERY MANAGEMENT A sample of eggs is placed in a single row in the trough until they fill its length. The number of eggs per 12 inches is referred to Table 18, which converts this to number of eggs per liquid ounce or quart. All eggs then are placed in a water-filled, 32-ounce (quart) graduated cylinder, the sub- merged eggs being leveled to the 32-ounce mark. The total number of eggs is the number per quart (or ounce) x the number of quarts (or ounces). The weight method is based on the average weight of eggs in a lot. Several 100-egg samples are drained and weighed to the nearest 0.1 gram. The average egg weight then is calculated. The entire lot of eggs is drained in preweighed baskets and weighed on a balance sensitive to 1 gram. Divi- sion of the total weight of the eggs by the average weight of one egg deter- mines the number of eggs in a lot. There are two sources of error in the weight method; variation in the amount of water retained on the eggs in the total lot and variation in sample weights due to water retention. Differ- ences in surface tension prevent consistent removal of water from the eggs. Blotting pads of folded cloth or paper toweling should be used to remove the excess water from the eggs. In the displacement method, water displaced by the eggs is used to meas- ure the egg volume. This provides an easily read water level rather than an uneven egg level when volume is determined. Small quantities of eggs can be measured in a standard 32-ounce graduated cylinder. For larger quanti- ties, a container with a sight gauge for reading water levels is most con- venient. A standard 25-milliliter burette calibrated in tenths of milliliters makes an excellent sight gauge. A table, converting gauge readings to fluid ounces, is prepared by adding known volumes of water to the container and recording the gauge readings. The eggs are drained at least 30 seconds in a frame net, and the underside of the net is wiped gently with a sponge or cloth to remove excess water. The total volume of eggs then is measured by changes in gauge readings (converted to volume) when eggs are added to the container. The amount of water initially placed in the container should be sufficient to provide a clearly defined water level above the eggs. The volume of water displaced by a known number of eggs is then determined by sample-counting; the more numerous and represen- tative the samples, the more accurate the total egg count will be. One or more random samples should be prepared for each volume measurement and a minimum of five samples for the total lot of eggs. For sampling, count out 50 eggs into a burette containing exactly 25 milliliters of water. Determine the exact number of milliliters of water displaced. The number of eggs per fluid ounce can then be determined from Table 19. The accuracy of these three methods has been compared, and only the Von Bayer technique showed a significant difference from actual egg counts, with the displacement method being the most accurate. However, the weight technique is so much faster and efficient that it is considered broodstock, spawning, and egg handling 183 Table 18. modified von baver table for the estimation of the numbers of fish eggs in a liquid quart. NO. OF EGGS DIAMETER OF EGGS NO. OF EGGS PER NO. OF EGGS PER PER 12 TROUGH (INCHES) LIQUID QUART LIQUID OUNCE 35 0.343 1,677 52 36 0.333 1,833 57 37 0.324 1,990 62 38 0.316 2,145 67 39 0.308 2,316 72 40 0.300 2,606 78 41 0.292 2,690 84 42 0.286 2,893 90 43 0.279 3,116 97 44 0.273 3,326 104 45 0.267 3,556 111 46 0.261 3,806 119 47 0.255 4,081 128 48 0.250 4,331 135 49 0.245 4,603 144 50 0.240 4,895 153 51 0.235 5,214 163 52 0.231 5,490 172 53 0.226 5,862 185 54 0.222 6,185 193 55 0.218 6,531 204 56 0.214 6,905 216 57 0.211 7,204 225 58 0.207 7,630 238 59 0.203 8,089 253 60 0.200 8,459 264 61 0.197 8,851 277 62 0.194 9,268 290 63 0.191 9,712 304 64 0.188 10,184 318 65 0.185 10,638 334 66 0.182 11,225 351 67 0.179 11,799 359 68 0.177 12,203 381 69 0.174 12,348 401 70 0.171 13,533 423 71 0.169 14,020 438 72 0.167 14,529 454 73 0.164 15,341 479 74 0.162 15,916 497 75 0.160 16,621 516 76 0.158 17,157 536 77 0.156 17,825 557 78 0.154 18,528 579 79 0.152 19,270 602 184 FISH HATCHERY MANAGEMENT Table 19. mh.lii, iters of water displaced by m eggs converted to number OF eggs per fluid ounce. MILLI- NUMBER MILLI- NUMBER MILI.I- NUMBER LITERS PER LITERS PER LHERS PER DISPLACED OUNCE DISPLACED OUNCE DISPLACED OUNCE 3.0 492.88 7.1 208.25 11.2 132.00 3.1 477.00 7.2 205.35 11.3 130.89 3.2 462.10 7.3 202.55 11.4 129.70 3.3 448.10 7.4 199.80 11.5 128.60 3.4 434.90 7.5 197.15 11.6 127.45 3.5 422.45 7.6 194.55 11.7 126.40 3.6 410.75 7.7 192.05 11.8 125.30 3.7 399.65 7.8 189.55 11.9 124.25 3.8 389.10 7.9 187.15 12.0 123.20 3.9 379.15 8.0 184.83 12.1 122.20 4.0 369.65 8.1 182.55 12.2 121.20 4.1 360.65 8.2 180.30 12.3 120.20 4.2 352.05 8.3 178.15 12.4 119.25 4.3 343.85 8.4 176.05 12.5 118.30 4.4 336.05 8.5 173.95 12.6 117.35 4.5 328.60 8.6 171.95 12.7 116.45 4.6 321.45 8.7 169.95 12.8 115.50 4.7 314.60 8.8 168.05 12.9 114.60 4.8 308.05 8.9 166.15 13.0 113.75 4.9 301.75 9.0 164.30 13.1 112.85 5.0 295.75 9.1 162. .50 13.2 112.00 5.1 289.95 9.2 160.70 13.3 111.20 5.2 284.35 9.3 159.00 13.4 110.35 5.3 279.00 9.4 157.30 13.5 109.55 5.4 273.80 9.5 155.65 13.6 108.70 5.5 268.85 9.6 154.05 13.7 107.95 5.6 264.05 9.7 152.45 13.8 107.15 5.7 259.40 9.8 150.90 13.9 106.40 5.8 254.95 9.9 149.35 14.0 105.60 5.9 250.60 10.0 147.85 14.1 104.85 6.0 246.45 10.1 146.40 14.2 104.15 6.1 242.40 10.2 144.95 14.3 103.40 6.2 238..50 10.3 143.55 14.4 102.70 6.3 234.70 10.4 142.15 14.5 102.00 6.4 231.05 10.5 140.80 14.6 101.30 6.5 227. ,50 10.6 139.. 50 14.7 100.60 6.6 224.05 10.7 138.20 14.8 99.90 6.7 220.70 10.8 136.90 14.9 99.25 6.8 217.45 10.9 135.65 15.0 98.60 6.9 214.30 11.0 134.40 7.0 211.25 11.1 133.20 BROODSTOCK, SPAWNING, AND EGG HANDLING 185 the best of the methods evaluated. The displacement method takes twice the time required by either of the other methods. The weight method is recommended when large lots of eggs must be enumerated, while the dis- placement method is more desirable with small lots of eggs. Another method of egg inventory, which differs from other volumetric methods basically in egg measuring technique, sometimes is used by fish culturists. Eggs are measured in a container, such as a cup or strainer filled to the top, and an equal number of containerfuls of eggs are put in each egg incubator tray or jar. Sample counting consists of counting all the eggs held in one measuring container. To get accurate egg inventories, the same measuring unit must be used for the sample counts as for measuring the eggs into the incubator. Measurement by filling the container to the top eliminates errors in judgment. This method gives a good estimate of the total number of eggs, but does not estimate the number of eggs per fluid ounce. Several methods have been used for the estimating number of striped bass eggs. Estimates can be made by weighing the eggs from each female and calculating the number of eggs on the basis of 25,000 per ounce. The eggs can also be estimated volumetrically on the basis of Von Bayer's table. Largemouth bass and catfish eggs are measured by weight or volumetric displacement. Various mechanical egg counting devices have been developed that use photoelectric counters (Figure 63). The eggs are counted as they pass a light source. Velocities producing count rates of up to 1,400 eggs per minute have proven to be accurate. Air bubbles, dirt, and other matter will interfere with accurate counting and must be avoided. Salmonid eggs should be physically shocked before egg picking (removal of dead eggs) commences, after the eggs have developed to the eyed stage. Undeveloped or infertile eggs remain tender and they will rupture when shocked. Water enters the egg and coagulates the yolk, turning the egg white; these eggs then are readily picked out. Shocking may be done by striking the trays sharply, siphoning the eggs from one container to another, or by pouring the eggs from the incubator trays into a tub of water from a height of 2 or 3 feet. Care should be taken to make sure that the eggs are not shocked too severely or normally developing eggs also may be damaged. (Figure 64). Numerous methods for removing dead eggs have been in use in fish cul- ture for many years. Before the introduction of satisfactory chemical fungi- cides, it was necessary to frequently remove (pick) all dead eggs to avoid the spread of fungus. In some instances where exposure to chemical treat- ments is undesirable, it still is necessary to pick the dead eggs. One of the earliest and most common methods of egg picking was with a large pair of tweezers made either of metal or wood. If only small numbers of eggs are picked, forceps or tweezers work very well. Another device in 186 FISH HATCHERY MANAGEMENT Figure 63. A mechanical egg counter used with salmon eggs. (FWS photo.) Figure 64. Salmon eggs being shocked. (FWS photo.) BROODSTOCK, SPAWNING, AND EGG HANDLING 187 use is a rubber bulb fitted to a short length of glass tubing. The diameter of the tubing is large enough to allow single eggs to pass through it and dead eggs are removed by sucking them up into the tube. A more ela- borate egg picker can be constructed of glass and rubber tubing and dead eggs are siphoned off into an attached glass jar (Figure 65). A flotation method of separating dead from live eggs still is used in many hatcheries, and particularly in salmon hatcheries. Eggs are placed in a container of salt or sugar solution of the proper specific gravity, so that live eggs will sink and dead eggs will float because of their lower density. A sugar solution is more efficient than salt because the flotation period is longer. The container is filled with water, and common table salt or sugar is added until the dead eggs float and live eggs slowly sink to the bottom. The optimum concentration of the solution may vary with the size and developmental stages of the eggs. Floating dead eggs are then skimmed off with a net. Best results are obtained if the eggs are well eyed because the more developed the embryo, the more readily the eggs will settle. Several electronic egg sorters are commercially available that separate the opaque or dead eggs from the live ones. Manufacturers of these machines claim a sorting rate of 100,000 eggs per hour. Another commer- cial sorter works on the principle that live eggs have a greater resiliency and will bounce (whereas dead eggs will not) and drop into a collecting tray. This sorter has no electrical or moving parts. Enumeration and transfer of fry are important facets of warmwater fish culture, because the eggs cannot be counted in many instances. The fry of many species, such as largemouth bass, smallmouth bass, and catfish, are spawned naturally in ponds, and then transferred to a rearing pond. To as- sure the proper stocking density, fry must be counted or their numbers es- timated accurately. Many methods are used, and vary in complexity and style. The simplest, but least accurate, is the comparison method. A sample of fry are counted into a pan or other similar container. The remaining fry are then distributed into identical containers until they appear to have the same density of fry as the sample container. The sample count is then used to estimate the total number of fry in all the containers. Other methods in- volve the determination of weight or volume of counted samples and then estimating the number of fry from the total weight or volume of the group. The most accurate methods require greater handling of the fry but, when they are small, handling should be kept to a minimum to reduce mortality. In catfish culture, a combination of methods is used. The number of eggs can be estimated by weight or from records on the parent fish. The gelatinous matrix in which catfish eggs are spawned makes the volumetric method of egg counting impractical. There are approximately 3,000 to 5,000 catfish eggs per pound of matrix, and the number of eggs can be estimated from the weight of the mass of eggs. After the eggs hatch, fry are 188 FISH HATCHERY MANAGEMENT SELF-SEALING MASON FRUIT JAR 1/4" COPPER TUBE -♦-DOUBLE-ENDED RUBBER BULB GLASS TUBE- 1/4" COPPER TUBE SMALL NOTCH Figure 65. Construction of a siphon egg picker. (Source: Davis 1953.) BROODSTOCK, SPAWNING, AND EGG HANDLING 189 enumerated volumetrically if they are to be moved immediately to rearing ponds. If they are held in rearing tanks or troughs until they accept formu- lated feed, their numbers are estimated from weighed and counted samples. Egg Disinfection Eggs received from other hatcheries should be disinfected to prevent the spread of disease. Disinfection should be carried out in separate facilities in order to prevent contamination of the hatchery by eggs, water, trays, and packing material from the shipping crate. The iodophor Betadine, can be used to disinfect most fish eggs. Eggs are treated at 100 parts per million active ingredient (iodine) for 10 minutes. A 100 parts per million iodine concentration is obtained by adding 2.6 fluid ounces of 0.5X Betadine per gallon of water. Betadine also is available in a 1% iodine solution. In soft water below 35 parts per million alkalinity, pH reduction can occur, causing high egg mortality. Sodium bicarbonate may be added as a buffer at 3.7 grams per gallon if soft water is encountered. Should a precipitate be formed from the sodium bicarbonate it will not harm the eggs. The eggs should be well rinsed after treatment. An active iodine solution is dark brown in color. A change to a lighter color indicates an inactive solution and a new solution should be used. Do not treat eggs within 5 days of hatching as premature hatching may result, with increased mortality. Tests should be conducted on a few eggs before Betadine is considered safe for general use as an egg disinfectant. Largemouth bass eggs can be treated with acriflavine at 500 to 700 parts per million or Betadine at 100 to 150 parts per million for 15 minutes. Roccal and formalin are not effective disinfectants at concentrations that are not injurious to fish eggs. Incubation Period Several methods have been devised for determining the incubation period of eggs. One method utilizes temperature units. One Daily Temperature Unit (DTU) equals 1° Fahrenheit above freezing (32°F) for a 24-hour period. For example, if the water temperature for the first day of incuba- tion is 56°F, it would contribute 24 DTU (56°-32°). Temperature units required for a given species of fish are not fixed. They will vary with dif- ferent water temperatures and are affected by fluctuating temperatures. However, DTU can be used as a guide to estimate the hatching date of a 190 FISH HATCHERY MANAGEMENT Table 20. number of days and daily lEMi'ERAruRE units required for TROUT EGGS TO HATCH". (SOURCE: LEITRITZ AND LEWIS l<)7(i.) WATER TEMPERATURE, T SPECIES 35 40 45 50 55 60 Rainbow trout Number of days to hatch Daily temperature units Brown trout Number of days to hatch Daily temperature units Brook trout Number of days to hatch Daily temperature units Lake trout Number of days to hatch Daily temperature units — 80 48 31 24 19 — 640 624 558 552 532 156 100 64 41 468 800 832 738 — — 144 103 68 44 35 _ 432 824 884 799 805 — 162 108 72 49 486 864 936 882 Spaces without figures indicate incomplete data rather than a proven inability of eggs to hatch at those temperatures. group of eggs at a specific temperature. The required temperature units to hatch several species of fish are presented in Tables 20 through 23. Factors Affecting Egg Development Three major factors that affect the development of the embryos are light, temperature, and oxygen. LIGHT Direct light may have an adverse effect on developing fish eggs. The most detrimental rays are those in the visible violet-blue range produced by cool white fluorescent tubes. Pink fluorescent tubes, which emit light in the yel- low to red range, are best suited for hatchery use. The best practice is to keep eggs covered and away from direct light. In general, embryos of fishes subjected to bright artificial light before the formation of eye pigments will suffer high mortality at all stages of growth. Affected eggs exhibit retarded development and accelerated hatch and, if they do hatch, the fingerlings often have reduced growth and severe liver damage. Eggs exposed to artificial light after formation of eye pig- ments are less susceptible to light rays but still exhibit increased mortality and reduced growth, or both. BROODSTOCK, SPAWNING, AND EGG HANDLING 191 Table 21. daily temperature unit REquiRED for egg development of Pacific salmon. DAILY TEMPERATURE UNITS SPECIES TO EYE TO HATCH TO EMERGE Chinook salmon Coho salmon Chum salmon Pink salmon Sockeye salmon 450 450 750 750 900 750 750 1,100 900 1,200 1,600 1,750 1,450 1,450 1,800 TEMPERA ri' RE Chinook salmon eggs have been incubated at temperatures as high as 6\°F without significant loss. When incubated at 4()°F and below, they have a much higher mortality than those incubated at temperatures of 57 to (iO°F. However, if chinook salmon eggs are allowed to develop to the 128-cell stage in 42°F water, they can tolerate 35°F water for the remainder of the incubation period. Lower temperatures have been experienced by sockeye and chinook in natural spawning environments with fluctuating tempera- tures without adverse affects. The lower threshold temperature for normal development of sockeye salmon is between 40 and 42°F, with an upper threshold temperature between 55 and 57°F. Water temperature appears to be a primary factor in causing yolk-sac constriction in landlocked Atlantic salmon fry. It apparently is triggered by both constant temperature or an excessively warm temperature. Fry raised in cold water with fluctuating temperature do not develop the constriction unless they are moved into a warmer constant temperature. Table 22. required daily temperature units for initial development of VARIOUS COOL- and WARMWATER SPECIES. incubation stage HATCH TO ACTIVE SWIMMING EGG TAKE .ACTIVE TO START OF SPECIES to HATCH SWIMMING FEEDING TOTAL Channel catfish 350 50 100 500 Largemouth bass 140 90 80 310 Smallmouth bass 130 100 80 310 Hybrid sunfish 75 90 100 265 Bluegill 75 100 100 275 Redear sunfish 100 100 100 300 Northern pike 180 50 100 330 Muskellunge 235 260 100 595 Walleye 300 20 20 340 Striped bass 100 90 130 320 192 fish hatchery management Table 23. time-temperature relationship and daily temperature units req^uired for hatching muskellunge eggs, DAILY TEMPERATURE UNITS TEMPERAI'URE °F DAYS TO HATCH TO HATCH (F) 45 21 273 47 20 300 49 19 323 51 18 342 53 16 336 55 14 322 57 12 300 59 10 270 61 9 261 63 8 248 65 7 231 67 6 210 Eggs and fry of walleye tolerate rapid temperature fluctuations. Approx- imately 390 daily temperature units are required for eggs to hatch in fluc- tuating water temperatures, while only 230 daily temperature units general- ly are required at more constant temperatures (see Table 22). Low water temperatures during spawning and incubation of largemouth bass eggs can cause high egg losses. Chilling of the eggs does not appear to be the direct cause of egg loss. Rather, it causes the male fish, which nor- mally guards and fans the eggs, to desert the nest. As a result, the eggs are left without aeration and die from suffocation. This is a common cause of egg losses in areas that are marginal for largemouth bass production. Data gathered at the Weldon Striped Bass Hatchery, Weldon, North Carolina, indicate that the optimum spawning temperature range for striped bass is between 62 and 67°F. The minimum recorded temperature at which spawning will occur is 55°F and the maximum temperature is yiT. OXYGEN Sac fry from eggs incubated at low oxygen concentrations are smaller and weaker than those from eggs incubated at higher concentrations. The best conditions for the optimal development of embryos and fry are at or near 100% oxygen saturation. As the development of an egg progresses, oxygen availability becomes increasingly important. Circulation of water is vital for transporting oxygen to the surface of the chorion and for removing meta- bolites from the vicinity of the developing egg. Eggs provided with insuffi- cient oxygen will develop abnormalities and their hatching may be either delayed or premature, depending on the species. BROODSTOCK, SPAWNING, AND EGG HANDLING 193 Transportation of Eggs Eggs can be shipped at four developmental stages: as immature eggs in the living female; as mature unfertilized eggs; as recently fertilized and water- hardened eggs; and as eyed eggs. Live females may be shipped, but this method requires more extensive transportation facilities than is required to ship eggs. Transportation of live fish is covered in Chapter 6. The shipping of mature unfertilized eggs requires some precautions. Sperm should be shipped separately in sealed plastic bags with an air space in the sperm container of at least 10 parts air to 1 part sperm. No air re- quirements are necessary for eggs. Both eggs and sperm should be kept re- frigerated. With these techniques, the fertility of Pacific salmon sperm and eggs is not affected by storage for 4 hours at temperatures of 47-52°F be- fore they are mixed. Eggs that are fertilized and then shipped under the same conditions can suffer high losses. When newly spawned and fertilized eggs are shipped the eggs must not be shaken in transit. Therefore, no air space should be allowed in the container. Eggs should not be shipped during the tender stage. They may be shipped over long distances after the eyed stage is reached, if they are kept cool and shipped in properly insulated boxes (Figure 66). Types of Incubators Many systems have been developed for incubating fish eggs. Basically, all of them provide a fresh water supply with oxygen, dissipate metabolic products, and protect the developing embryo from external influences which may be detrimental. HATCHING TRAYS Hatching trays are perhaps the simplest type of incubation unit used. They have been used successfully for many species of fish. The screened hatching tray is sized to fit inside a rearing trough. The screening has rec- tangular openings that will retain round eggs but permit newly hatched fry to fall through. The wire mesh may be obtained in a variety of sizes and is called triple warp mesh cloth. The triple warp cloth should have nine meshes per inch for eggs that are 400 to 700 per ounce; seven meshes per inch for eggs 240 to 390 per ounce; six meshes per inch for eggs 120 to 380 per ounce; and five meshes per inch cloth for eggs that are 60 to 90 per ounce. Eggs are placed on the tray no more than two layers deep, and the tray is inclined and wedged at an angle of approximately 30 degrees, slanting to- ward the incoming water in the trough. When all the eggs have hatched 194 FISH HATCHERY MANAGEMENT Figure 66. Commercially available shipping boxes can be used to transport fish eggs. The boxes should be constructed to keep the eggs moist and cool without actually carrying them in water, (l) A wet cloth is placed in the shipping tray and the eggs are carefully poured into the tray. (2) The tray should not be filled to the point where the next succeeding tray will compress the eggs and put pres- sure on them. The cloth is then carefully folded over the eggs and the next tray put in place. (3) The top tray is filled with coarsely crushed ice or ice cubes to provide cooling during shipping. The melting ice also will provide water to keep the eggs moist. Ice should never be used directly from the freezer and should be allowed to warm until it starts to melt before it is placed with the eggs. (4) The insulated lid is put in place, and the box is sealed and properly labeled for shipping. (FWS photos.) and the fry have fallen through the mesh cloth, the trays are removed with the dead eggs that remain on them. These units are relatively cheap and easy to maintain, and egg picking is relatively simple. The disadvantages are that rearing troughs must be available, there must be some means of excluding light from the troughs while the eggs are being incubated, and there is always a danger of improper water flow through the trays. CLARK-WILLIAMSON TROUGH The Clark- Williamson trough is a tray-hatching system for incubating large numbers of eggs. The eggs are held on screen trays and are stacked vertically rather than being placed horizontally in the trough. Dam boards BROODSTOCK, SPAWNING, AND EGG HANDLING 195 are placed in slots in the trough to force the waterflow up through each stack. Many eggs can be handled in this type of unit, but it is difficult to ob- serve egg development during incubation, and all trays in a stack must be removed in order to examine the eggs on any individual tray. Possible air locks within the stack can cause poor water circulation through the eggs. CATFISH TROUGHS Channel catfish eggs, which are deposited in a cohesive mass, require spe- cial devices when they are moved to a hatching trough for artificial incuba- tion. The large egg masses usually are broken up into smaller pieces to enhance aeration and then placed in suspended baskets similar to the trays described in the previous section. When catfish eggs are hatched in troughs, they must be agitated by pad- dles supported over the trough and driven by an electric motor or a water wheel (Figure 67). The agitation must be sufficient to gently move the whole egg mass. Paddles are constructed of galvanized tin or aluminum and attached to a rotating shaft. The paddles are commonly 4 inches wide and long enough to dip well below the bottom of the baskets as they turn. The pitch of the paddles is adjusted as required to insure movement of spawns in the baskets. The preferred speed is about 30 revolutions per minute. HATCHING BASKETS Hatching baskets are quite similar to hatching trays, except that they are approximately 6 to 12 inches deep and suspended in the trough to permit a horizontal water flow. In many cases, deflector plates are installed ahead of each basket in such a way as to force the flowing water up through the baskets for better circulation. In the case of Pacific salmon, as many as ,50,000 eggs may be placed in a single basket. HATCHING JARS Hatching jars usually are placed in rows on racks with a manifold water supply trough providing inlets to each jar and a waste trough to catch overflow water (Figure 68). A simple unit can be fabricated from 2-inch supply pipe with taps and an ordinary roof gutter as the waste trough. An open tee usually is installed between the supply line and the pipe to the bottom of the jar to aid in the elimination of gas bubbles during incuba- tion of salmonid eggs, which must not be distrubed. The open tee may also be used to introduce chemicals for treating eggs. The diameter of the tee 196 FISH HATCHERY MANAGEMENT Figure 67. Channel catfish trough for egg incubation. Paddles (arrow) gently circulate the water in the trough. (FWS photo.) should be larger than the pipe entering the jar to prevent venturi action from sucking air bubbles into the jar. Hatching jars are designed to provide an upward flow of water intro- duced at the bottom of the jar. When rolling of the eggs is desired, as in the case of some coolwater species, the bottom of the jar is concave, with the water introduced at the center. When used for incubating trout or sal- mon eggs, the jar is modified with a screen-supported gravel bottom, and the water is introduced underneath the gravel. This provides a uniform, upward water flow, and the eggs are stationary. These systems also have been used for striped bass and channel catfish egg incubation. Some fry will swim out of the jar and into the waste trough if a cover screen is not provided. Coolwater species are allowed to swim from the jars and are collected in holding tanks. MONTAN./>k HATCHING BOX The Montana Hatching Box operates essentially like a hatching jar. The box is constructed of waterproof plywood or fiberglass and is approxi- mately 1 foot square by 2 feet high. A vertical water flow is provided by a BROODSTOCK, SPAWNING, AND EGG HANDLING 197 manifold of pipes beneath a perforated aluminum plate in the bottom of the box. A screened lip on the upper edge of the box provides an overflow and retains the eggs or fry. The box commonly is used in bulk handling of eggs to the eyed stage for shipping, but it can also be used to rear fry to the feeding stage (Figure 69). A problem with the hatching box is the tendency for gas bubbles to build up below the perforated plate, shutting off the water flow to portions of the box. As with other systems, it is good practice to aerate any water supply used for this type of incubation. VERTICAL-TRAY INCUBATORS The vertical- tray incubator is widely used for developing salmonid eggs (Figure 70). The eggs are allowed to hatch in the trays and fry remain there until ready to feed. Water is introduced at one end of the top tray and flows under the egg basket and up through the screen bottom, circulat- ing through the eggs. Water, upwelling through the bottom screen helps prevent smothering of hatched fry. The water then spills over into the tray below, and is aerated as it falls. Figure 68. Jar incubation of muskellunge eggs. (Courtesy Wisconsin Depart- ment of Natural Resources.) 198 FISH HATCHERY MANAGEMENT Figure 69. Trout eggs being poured into a Montana hatching box. These incubators can be set up as either 8- or 16-tray units. Draining and cleaning of each tray is possible without removing it from the incuba- tor. Individual trays can be pulled out for examination without disturbing other trays in the stack. Screen sizes can be varied to accommodate the species of eggs being incubated. Accumulations of air bubbles can cause problems in water circulation, and care should be taken to de-aerate super- saturated water prior to use in this unit. Vertical incubators have several advantages over troughs. They require small amounts of water to operate, and use relatively little floor space. Fungus can be controlled easily with chemicals due to the excellent flow pattern through the eggs. The small quantities of water required for these incubators make it feasible to heat or cool the water as required. BROODSTOCK, SPAWNING, AND EGG HANDLING 199 SIMULATED NATURAL CONDITIONS AND REARING POND INCUBATION Salmon and steelhead eggs have been incubated successfully between layers of gravel, simulating natural spawning conditions. An incubation box that has proved successful is made of 7-inch marine plywood, 8 feet long, 2 feet wide, and 15 inches deep. Water, which is first filtered through crushed rock, is supplied to the box by four 1-inch diameter aluminum conduit pipes placed full length in the bottom of the box. Use of such a device for anadromous fish permits the incubation of eggs in the stream system in which the fish are to be released. A similar type of system involves incubation channels. Incubation chan- nels differ from previously discussed spawning channels in that eyed eggs are placed in prepared trenches. Fish reared under these conditions are generally hardier than those reared in the hatchery. Plastic substrates can be added to incubation units (such as vertical incubators) to simulate the environment provided by gravel. Plastic sub- strate fabricated from artificial grass also has been used successfully in sal- monid incubation systems to provide a more natural environment for newly hatched fry and has resulted in larger and more hardy fish. The state of Washington has developed a method for incubating salmon eggs utilizing specially designed trays placed in raceways. These units are Figure 70. Salmon eggs being measured into a vertical- tray incubator. A screen lid is placed on top of the tray to prevent loss of eggs and hatched fry. 200 FISH HATCHERY MANAGEMENT similar to hatchery trays but are much larger. The raceways are filled with water, eggs are placed in the trays, and the hatched fry are allowed to exit into rearing ponds at their own volition. Bibliography Alderdice, D. F., W. p. Wickett, and J. R. Brett. 1958. Some effects of temporary expo- sure to low dissolved oxygen levels on Pacific salmon eggs. Journal of the Fisheries Research Board of Canada 15(2):229-249. Allbaugh, Clyde A., and Jerry V. Manz. 1964. Preliminary study of the effects of tempera- ture fluctuations on developing walleye eggs and fry. Progressive Fish-Culturist 26(4): 175- 180. Allison, Leonard N. 1951. Delay of spawning in eastern brook trout by means of artificially prolonged light intervals. Progressive Fish-Culturist 13(3) : 1 1 1- 1 16. 1961. The effect of tricaine methanesulfonate (MS-222) on the motility of brook trout sperm. Progressive Fish-Culturist 23(l):46-48. Amend, Donald F. 1974. Comparative toxicity of two iodophors to rainbow trout eggs. Transactions of the American Fisheries Society 103(l):73-78. Anderson, Richard O. 1964. A sugar-flotation method of picking trout eggs. Progressive Fish-Culturist 26(3):124-126. Anonymous. 1951. Plastic hatching box for stocking trout and salmon. Progressive Fish- Culturist 13(4):228. 1954. Char spawning in observation tank in Swedish laboratory. Progressive Fish- Culturist 16(2) :59. 1955. Bentonite and largemouth bass eggs. Progressive Fish-Culturist 17(l):19. 1967. Temperatures for hatching walleye eggs. Progressive Fish-Culturist 29(l):20. Armbruster, Daniel. 1966. Hybridization of the chain pickerel and northern pike. Progres- sive Fish-Culturist 28(2):76-78. Bailey, Jack E. 1964. Russian theories on the inferior quality of hatchery-reared chum sal- mon fry. Progressive Fish-Culturist 26(3): 130. , and William R. Heard. 1973. An improved incubator for salmonids and results of preliminary tests of its use. National Oceanic and Atmospheric Administration Techni- cal Memorandum, National Marine Fisheries Service, Auke Bay Fishery Laboratory, Number 1. 7 p. , Jerome J. Pella, and Sidney G. Taylor. 1976. Production of fry and adults of the 1972 brood of pink salmon, Oncorhynchus gorbuscha, from gravel incubators and natural spawning at Auke Creek, Alaska. National Marine Fisheries Service Fishery Bulletin 74(4):961-971. , and Sidney G. Taylor. 1974. Plastic turf substitute for gravel in salmon incubators. National Marine Fisheries Service Marine Fisheries Review 36(l0) :35-38. Banks, Joe L. 1975. Methods of handling and transporting green fall chinook eggs. Proceed- ings of the 26th Annual Northwest Fish Culture Conference, December 3-5. 176 p. Barrett, L 1951. Fertility of salmonid eggs and sperm after storage. Journal of the Fisheries Research Board of Canada 8(3):12.5-133. Bayless, Jack D. 1972. Artificial propagation and hybridization of striped bass, Roccus saxa- tilis. South Carolina Wildlife and Marine Resources Department, Columbia, South Carolina. 135 p. Beaver, John A., Kermit E. Sneed, and Harry K. Dupree. 1966. The difference in growth of male and female channel catfish in hatchery ponds. Progressive Fish-Culturist 28(0:47-50. BROODSTOCK, SPAWNING, AND EGG HANDLING 201 Bishop, R. D. 197.t. The use of circular tanks for spawning striped bass (Morone saxatilis). Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 28:35-44. Blosz, John. 1952. Propagation of largemouth black bass and bluegill sunfish in federal hatcheries of the southeast. Progressive Fish-Culturist 14(2):f)l-()f). Bonn, Ed\s ard W., Willi.\m M. Bailey, Jack D. Bavllss, Klm E. Erickson, and Robert E. Stevens. 1976. Guidelines for striped bass culture. Striped Bass Committee, South- ern Division, American Fisheries Society, Bethesda, Maryland. 103 p. Brannon, E. L. 1965. The influence of physical factors on the development and weight of sockeye salmon embryos and alevins. International Pacific Salmon Fisheries Commis- sion Progress Report 12, New Westminster, British Columbia, Canada. 25 p. Braschler, E. W. 1975. Development of pond culture techniques for striped bass (Morone saxatilis) (Walbaum). Proceedings of the Annual Conference Southeastern Association of Game Fish Commissioners 28:44-48. BraL'HN, James L. 1971. Fall spawning of channel catfish. Progressive Fish-Culturist 33 (3): 150- 152. 1972. A suggested method for sexing bluegills. Progressive Fish-Culturist 34(l):17. Bryan, Robert D., and Kenneth O. Allen. 1969. Pond culture of channel catfish fmger- lings. Progressive Fish-Culturist 3l(l):38-43. Bl'RROWS, Roger E. 1949. Recommended methods for fertilization, transportation, and care of salmon eggs. Progressive Fish-Culturist 1 1 (3) :175-178. 1951. A method for enumeration of salmon and trout eggs by displacement. Progres- sive Fish-Culturist 13(l):25-30. 1951. An evaluation of methods of egg enumeration. Progressive Fish-Culturist 13(2):79-85. 1960. Holding ponds for adult salmon. US Fish and Wildife Service Special Scientific Report- Fisheries 357. 13 p. , and David D. Palmer. 1955. A vertical egg and fry incubator. Progressive Fish- Culturist 17(4):147-155. and H. William Newman. 1952. Effects of injected pituitary material upon the spawning of blueback salmon. Progressive Fish-Culturist 14(3):1 13-1 16. Buss, Keen. 1959. Jar culture of trout eggs. Progressive Fish-Culturist 2l(l):26-29. - , and Kenneth G. Core. 1966. The viability of trout germ cells immersed in water. Progressive Fish-Culturist 28(3):152-153. and Howard Fo.X. 1961. Modifications for the jar culture of trout eggs. Progressive Fish-Culturist 23(3):142-144. , and Dixon Waite. 1961. Research units for egg incubation and fingerling rearing in fish hatcheries and laboratories. Progressive Fish-Culturist 23(2):83-86. , and James E. Wright. 1957. Appearance and fertility of trout hybrids. Transactions of the American Fisheries Society 87:172^181. _, and 1956. Results of species hybridization within the family Salmonidae. Pro- gressive Fish-Culturist 18(4):149-158. Canfield, H. L. 1947. Artificial propagation of those channel cats. Progressive Fish-Culturist 9(l):27-30. Carlson, Anthony R. 1973. Induced spawning of largemouth bass (Micropierus salmoides). Transactions of the American Fisheries Society 102(2) :442-444. Carter, Ray R., and Allen E. Thomas. 1977. Spawning of channel catfish in tanks. Progres- sive Fish-Culturist 39(l):13. Ch.^STAIN, G. a., and J. R. Snow. 1966. Nylon mats as spawning sites for largemouth bass, Micropierus salmoides. Proceedings of the Annual Conference Southeastern A.ssociation of Game and Fish Commissioners 19:405-408. 202 FISH HATCHF.RY MANAGEMENT Clark, Minor. ly^O. Bass production in a Kentucky fish hatchery pond. Progressive Fish- Culturist 12(l):33-34. Cl.AY, C. H. 19()1. Design of fishways and other fish facilities. Department of Fisheries, Ot- tawa, Ontario. 301 p. Cli:mmkns, H. P., and K. E. Sneed. 19.')7. The spawning behavior of the channel catfish. US Fish and Wildlife Service Special Scientific Report Fisheries 21i). II p. Combs, Bobby D. 1965. Effect of temperature on development of salmon eggs. Progressive Fish-Culturist 27(3):134-137. , and Roger E. Bl;rrows. 19.')7. Threshold temperatures for the normal development of chinook salmon eggs. Progressive Fish-Culturist l9(l):3-6. , and 19.'J9. Effects of injected gonadotrophins on maturation and spawning of blueback salmon. Progressive Fish-Culturist 21 (4) : KiS-lfiH. , , and Richard G. Bigej. 1959. The effect of controlled light on the maturation of adult blueback salmon. Progressive Fish-Culturist 2l(2):63-69. CORSCJN, R. W. 1955. Four years' progress in the use of artificially controlled light to induce early spawning of brook trout. Progressive Fish-Culturist 17(3) :99-102. Dahlberg, Michael L., Jack E. Bailey, and William S. Pinette. 1978. Evaluation of three methods of handling gametes of sockeye salmon for transport to incubation facili- ties. Progressive Fish-Culturist 40(2) :7 1-72, Davis, Allen S., and Gerald J. Paulik. 1965. The design, operation, and testing of a pho- toelectric fish egg counter. Progressive Fish-Culturist 27(4):185-192. Davis, H. S. 1953. Culture and diseases of game fish. University of California Press, Berkley, California. 332 p. Dill, L. M. 1969. Annotated bibliography of the salmonid embryo and alevin. Department of Fisheries, Vancouver, British Columbia. 190 p. DoBiE, John O., Lloyd Meehean, S. F. Snieszko, and George N. Washburn. 1956. Rais- ing bait fishes. US Fish and Wildlife Service Circular 35. 124 p. Donaldson, Lauren R. 19()H. Selective breeding of salmonoid fishes. LIniversity of Washing- ton College of Fisheries, Contribution 315, Seattle, Washington. , and Deb MenaSVETA. 1961. Selective breeding of chinook salmon. Transactions of the American Fisheries Society 90(2): 160- 164. Dumas, Richard F. 196(). Observations on yolk sac constriction in landlocked Atlantic sal- mon fry. Progressive Fish-Culturist 28(2):73-75. EiSLER, Ronald. 1957. Some effects of artificial light on salmon eggs and larvae. Transactions of the American Fisheries Society 87:151-162. 1961. Effects of visible radiation on salmonid embryos and larvae. Growth 25(4):281-346. Embody, G. C. 1934. Relation of temperature to the incubation periods of eggs of four species of trout. Transactions of the American Fisheries Society (i4:281-292. Emig, John W. 1966. Largemouth bass. Pages 332-353 in Alex Calhoun, editor. Inland Fisheries Management. California Department of Fish and Game, Sacramento. Fish, Frederic F. 1942. The anaesthesia of fish by high carbon dioxide concentrations. Transactions of the American Fisheries Society 72:25-29. Fish, G. R., and G. D. Ginnelly. 1966. An adverse effect of coelomic fluid on unspawned ova in trout. Transactions of the American Fisheries Society 95(l):104-107. Fowler, Laurie G. 1972. Growth and mortality of fingerling chinook salmon as affected by egg size. Progressive Fish-Culturist 34(2):66-69. Gall, G. A. E. 1972. Rainbow trout broodstock selection program with computerized scoring. California Department of Fish and Game, Inland Fisheries Administration Report 72-9, Sacramento. 20 p. 1974. Influence of size of eggs and age of female on hatchability and growth in rain- bow trout. California Fish and Game 60(l):26-36. BROODSTOCK, SPAWNING, AND EGG HANDLING 203 1975. Genetics of reproduction in domesticated rainbow trout. Journal of Animal Sci- ence 40(1): 19-29. Geibel, G. E., and P. J. Murray. 1961. Channel catfish culture in California. Progressive Fish-Culturist 23(3):99-105. Hagen, William, Jr. 1953. Pacific salmon; hatchery propagation and its role in fishery man- agement. US Fish and Wildlife Service Circular 24. 56 p. Hamano, Shigerl'. 1961. On the spermatozoa agglutinating agents of the dog salmon and the rainbow trout eggs. Bulletin of the Japanese Society of Scientific Fisheries 27 (3): 225-251. Haskell, D. C. 1952. Egg inventory: enumeration with the egg counter. Progressive Fish- Culturist 14(2):81-82. Hendersu.N', Harmon. 1965. Observation on the propagation of flathead catfish in the San Marcos State Fish Hatchery, Texas. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 17:173-177. Henderson, Nancy E., and John E. Dewar, 1959. Short-term storage of brook trout milt. Progressive Fish-Culturist 21 (4):169-171. Henderson, W. H., and S. Winckler. 1968. A winning combination. Texas Parks and Wildlife 26(10) :27-28. HiNER, L.ALRENCE. 1961. Propagation of northern pike. Transactions of the American Fisheries Society 90(3):298-302. HORTON, Howard F., and Alxin G. Ott. 1976. Cryopreservation of fish spermatozoa and ova. Journal of the Fisheries Research Board of Canada 33(4,2)995-1000. HOURSTON, W. R., and D. MacKinnon. 1956. Use of an artificial spawning channel by sal- mon. Transactions of the American Fisheries Society, 86:220-230. Ihssen, Peter. 1976. Selective breeding and hybridization in fisheries management. Journal of the Fisheries Research Board of Canada 33(2):316-321. Inslee, Theophilas D. 1975. Increased production of smallmouth bass fry. Pages 357-361 in H. Clepper, editor. Black bass biology and management. Sport Fishing Institute, Washington, D.C. Islam, Md. Aminul, Ylkio Nose, and Fujio Y.^SUDA. 1973. Egg characteristics and spawn- ing season of rainbow trout. Bulletin of the Japanese Society of Scientific Fisheries 39(7):741-751. Jackson, U. Thomas. 1979. Controlled spawning of largemouth bass. Progressive Fish- Culturist 4l(2):90-95. Johnson, H. E., and R. F. Brice. 1953. Effects of transportation of green eggs, and of water temperature during incubation, on the mortality of chinook salmon. Progressive Fish- Culturist 15(3):104-10H. Johnson, Leon D. 1954. Use of urethane anesthesia in spawning eastern brook trout. Progres- sive Fish-Culturist 16(4):182-183. Jones, Irving W., and Carl H. Copper. 1965. An accurate photoelectric egg counter using a jet pump. Progressive Fish-Culturist 27(l):52-54. JURGENS, K. C, and W. H. Brown. 1954. Chilling the eggs of the largemouth bass. Progres- sive Fish-Culturist 16(4):172-175. Kalman, Sumner M. 1959. Sodium and water exchange in the trout egg. Journal of Cellular and Comparative Physiology 54(2): 153-162. Kelly, Willl\m H. 1962. Dye-induced early hatching of brown trout eggs. New York Fish and Game Journal 9(2) :137-141. KincaiI), H. L. 1976. Effects of inbreeding on rainbow trout populations. Transactions of the American Fisheries Society 105(2):273-280. 1976. Inbreeding in rainbow trout (Salmo gairdnerO- journal of the Fisheries Research Board of Canada 33(l l):2420-2426. 204 FISH HATCHERY MANAGEMENT .. 1977. Rotational line crossing; an approach to the reduction of inbreeding accumula- tion in trout broodstocks. Progressive Fish-Cuiturist 39(4):179-181. Kloniz, Georgk W. I9()4. Anesthesia of fishes. Proceedings of the Symposium on Experi- mental Animal Anesthesiology, Brooks Air Force Base. (Mimeo.) K.MGHI, Ai.K.xi.s E. 1!)()3. The embryonic and larval development of the rainbow trout. Trans- actions of the American Fisheries Society 92(4):344-3,5,'). KWAIN, Wen HWA. 197,'). Embryonic development, early growth, and meristic variation in rainbow trout (Salmo gairdneri) exposed to combinations of light intensity and tempera- ture. Journal of the Fisheries Research Board of Canada 32(3) :397-402. Lagler, K. F., J. E. Bardach, and R. R. Miller. 1962. Ichthyology, the study of fishes. John Wiley and Sons, New York. 545 p. Lannan, James E. 1975. Netarts Bay Chum Salmon Hatchery, an experiment in ocean ranch- ing. Oregon State University Sea Grant College Program Publication ORESU-H-75-001. 28 p. Leitritz, Earl, and Roberi C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of Fish and Game, Fish Bulletin 1()4. 197 p. Leon, Kenneth A. 1975. Improved growth and survival of juvenile Atlantic salmon (Salmo salar) hatched in drums packed with a labyrinthine plastic substrate. Progressive Fish- Culturist 37(3):158-163. Lessm.AN, Charles A. 1978. Effects of gonadotropin mixtures and two steroids on inducing ovulation in the walleye. Progressive Fish-Culturist 40(l):3-5. Lucas, K. C. 1960. The Robertson Creek spawning channel. The Canadian Fish Culturist 27:3-23. McClary, Denny. 1967. Development and use of an egg counter. Proceedings of the Northwest Fish Culture Conference. 22 p. McCraREN, J. P. 1!)73. lodophor controls microorganisms on catfish eggs. Fish Health News 2(4):1. McNeil, William J., and Jack E. Bailey. 1975. Salmon rancher's manual. National Marine Fisheries Service, Northwest Fisheries Center Auke Bay Fisheries Laboratory, Auke Bay, Alaska. Processed Report. 95 p. Mead, R. W., and W. L. Woodall. 1968. Comparison of sockeye salmon fry produced by hatcheries, artificial channels and natural spawning areas. Progress Report 20, Interna- tional Pacific Salmon Fisheries Commission, New Westminster, British Columbia. 41 p. Meyer, Fred P., Kermit E. Sneed, and Pall T. Eschmeyer, Editors. 1973. Second Report to the Fish Farmers. Resource Publication 113, Bureau of Sport Fisheries and Wildlife, Washington, D.C. 123 pp. Miller, Jack G. 1965. Advances in the use of air in taking eggs from trout. Progressive Fish-Culturist 27(4):234-237. Nelson, Ben A. 1960. Spawning of channel catfish by use of hormone. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 14:145-148. Nomura, Minoru. 1962. Studies on reproduction of rainbow trout, Salmo gairdneri, with spec- ial reference to egg taking. III. Acceleration of spawning by control of light. Bulletin of the Japanese Society of Scientific Fisheries 28(l l):1070-1076. 1964. Studies on reproduction of rainbow trout, Salmo gairdneri, with special reference to egg taking. VI. The activities of spermatozoa in different diluents, and preservation of semen. Bulletin of the Japanese Society of Scientific Fisheries 30(9) :723-733. Nursall, J. R., and A. D. Hasler. 1952. A note on experiments designed to test the viability of gametes and the fertilization of eggs by minute quantities of sperm. Progressive Fish-Culturist 14(4):165-168. Ogino, Chinkichi, and Setsuko Yasuda. 19r)2. Changes in inorganic constituents of developing rainbow trout eggs. Bulletin of the Japanese Soceity of Scientific Fisheries 28(8):788-791. BROODSTOCK, SPAWNING, AND EGG HANDLING 205 Olson, P. A., and R. F. Foster. 1955. Temperature tolerance of eggs and young of Columbia River chinook salmon. Transactions of the American Fisheries Society 8."):203-207. OSEID, DoNAVON M., and Lloyd L. Smith, Jr. 1971. Survival and hatching of vk'aileye eggs at various dissolved oxygen levels. Progressive Fish-Culturist 33(2)81-85. Palmer, D.'Wtd D., Roger E. Burrows, O. H. Rcjbertson, and H. William Newman. 1954. Further studies on the reactions of adult blueback salmon to injected salmon and mammalian gonadotrophins. Progressive Fish-Culturist 16(3):99-107. PaRKHURST, Z. E., and M. A. Smith. 1957. Various drugs as aids in spawning rainbow trout. Progressive Fish-Culturist 19(l):39. Pecor, Charles H. 1978. Intensive culture of tiger muskellunge in Michigan during 1976 and 1977. American Fisheries Society Special Publication 11:202-209. Perlmutter, Alfred, and Edward White. 1962. Lethal effect of fluorescent light on the eggs of the brook trout. Progressive Fish-Culturist 24(l):26-30. Phillips, A. M. 1957. Cortland in-service training school manual. US Fish and Wildlife Serv- ice, Cortland, New York. 271 p. Phillips, Arthur M., Jr., and Richard F. Dumas. 1959. The chemistry of developing brown trout eyed eggs and sac fry. Progressive Fish-Culturist 21 (4):161-164. Phillips, Raymond A. 1966. Walleye propagation. US Fish and Wildlife Service, Washing- ton, D.C. 13 pp. Pisarenkova, A. S. 1958. Storage and transportation of sperm of rainbow trout and pike. (Khranenie I Transportirovka Spermy Raduzhnoi Foreli I Shchuki.) Rybnaya Pro- myshlennost' Dal'nego Vostoka 34:47-50. Plosila, Daniel S., and Walter T. Keller 1974. Effects of quantity of stored sperm and water on fertilization of brook trout eggs. Progressive Fish-Culturist 36(l):42-45. , and Thomas J. McCartney. 1972. Effects of sperm storage and dilution on fer- tilization of brook trout eggs. Progressive Fish-Culturist 34(3):179-181. PooN, Derek C, and A. Kenneth Johnson. 1970. The effect of delayed fertilization on transported salmon eggs. Progressive Fish-Culturist 32(2):81-84. PrescOTT, David M. 1955. Effect of activation on the water permeability of salmon eggs. Journal of Cellular and Comparative Physiology 45(l):l-12. Ramaswami, L. S., and B. L Sundararaj. 1958. Action of enzymes on the gonadotrophic ac- tivity of pituitary extracts of the Indian catfish, Heteropneustes. Acta Endocrinologica 27(2):253-256. Reisenbichler, R. R., and J. D. McIntyre. 1977. Genetic differences in growth and survival of juvenile hatchery and wild steelhead trout, (Salmo gairdneri). Journal of the Fisheries Reseach Board of Canada 34(l):123-128. RicKER, W. E. 1970. Hereditary and environmental factors affecting certain salmonid popula- tions. In Raymond C. Simon and Peter A. Larkin, editors. The stock concept in Pacific salmon. H. R. MacMillan lectures in fisheries. University of British Columbia, Vancouver. RiCKETT, John D. 1976. Growth and reproduction of largemouth bass and black bullheads cultured together. Progressive Fish-Culturist 38(2):82-85. Robertson, O. H., and A. P. Rinfret. 1957. Maturation of the infantile testes in rainbow trout (Salmo gairdneri) produced by salmon pituitary gonadotrophins administered in cholesterol pellets. Endocrinology 60(4):559-562. RuCKER, R. R. 1961. The use of merthiolate on green eggs of the chinook salmon. Progressive Fish-Culturist 23(3):138-141. , J. F. Conrad, and C. W. Dickeson. 1960. Ovarian fluid; its role in fertilization. Pro- gressive Fish-Culturist 22(2):77-78. RuCKER, Robert R. 1949. Fact and fiction in spawntaking addenda. Progressive Fish- Culturist ll(l):75-77. Saksena, V. P., K. Yamamoto, and C. D. RiGGS. 1961. Early development of the channel catfish. Progressive Fish-Culturist 23(4): 156-1 61. 206 FISH HATCHERY MANAGEMENT Salter, Frkdkrick H. 1!)7"). A new incubator for salmonids designed by Alaska laboratory. National Marine P'isheries Service Marine Fisheries Review 37(7). Senn, Harry G., Jack H. Paiiie., and John Clayton. li)7;-i. Washington jjond trays as a method for incubating salmon eggs and fry. Progressive Fish-Culturist 3.5(S):132-137. Shannon, El gene H., and William B. Smith. 1968. Preliminary observations of the effect of temperature on striped bass eggs and sac fry. Proceedings of the Annual Conference Southeastern Assocation of Game Commissioners, 21 :2,')7-'2()(). SheltoN, Jack M. 1955. The hatching of chinook salmon eggs under simulated stream ( ondi- tions. Progressive Fish-Culturist 17(l):20-35. , and R. D. Pollock. 19f)(i. Siltation and egg survival in incubation channels. Transac- tions of the American Fisheries Society 95(2):183- 187. Shumway, Dean L., Charles E. Warren, and Peter Doldorofe. 1964. Influence of oxy- gen concentration and water movement on the growth of steelhead trout and coho sal- mon embryos. Transactions of the American Fisheries Society 93(4):342-35f). Silver, Stuart J., Charle.s E. Warren, and Peter Doldorofe. li)63. Dissolved oxygen re- quirements of developing steelhead trout and chinook salmon embryos at different wa- ter velocities. Transactions of the American Fisheries Society 92(4):327-343. Smitherman, R. O., Hls.'SEIN El-Ibiary, and R. E. Reagan. 1978. Genetics and breeding of channel catfish. Alabama Agricultural Experimental Station Bulletin 223, Auburn University, Auburn, Alabama. 34 p. Sneed, K. E., and H. P. Clemens. 1956. Survival of fish sperm after freezing and storage at low temperatures. Progressive Fish-Culturist 18(3):99~ 103. , and 1959. The use of human chorionic gonadotrophin to spawn warmwater fishes. Progressive Fish-Culturist 21 (3):117-12(). , and 1960. Hormone spawning of warmwater fishes: its practical and biological significance. Progressive Fish-Culturist 22(3):109- 113. and Harry L. Dupree. 1961. The effect of thyroid stimulating hormone combined with gonadotrophic hormones on the ovulation of goldfish and green sunfish. Progres- sive Fish-Culturist 23(4):179- 182. Sniesko, S. F., and S. B. Fiddle. 1948. Disinfection of rainbow trout eggs with sul- fomerthiolate. Progressive Fish-Culturist 10(3):143- 149. Snow, J. R. 1959. Notes on the propagation of the flathead catfish, Pylodictis olivaris (Rafinesque). Progressive Fish-Culturist 21 (2) :75-8(). , R. O. Jones, and W. A. Rogers. 1964. Marion in-service training school manual. US Fish and Wildlife Service, Marion, Alabama. 460 p. Stenion, J. E. 1952. Additional information on eastern brook trout x lake trout h>brids. Canadian Fish Culturist, Issue 13:15-21. Stevens, Roberi E. 19f)6. Hormone-induced spawning of striped bass for reservoir stocking. Progressive Fish-Culturist 28(l):19-28. 19()7. Striped bass rearing. North Carolina Cooperative Fishery Unit, North Carolina State University, Raleigh. 14 p. (Mimeo.) 197!). Striped bass culture in the United States. Commercial Fish Farmers and Aqua- culture News 5(3):10:14. Slppes, Charles V. 1972. Jar incubation of channel catfish eggs. Progressive Fish-Culturist 34(l):48. Taylor, W. G. 1967. Photoelectric egg sorter. Proceedings of the Northwest Fish Culture Conference: 1 4-16. Thomas, Allan E. 1975. Effect of egg concentration in an incubation channel on survival of chinook salmon fry. Transactions of the American Fisheries Society 104(2) :335-337. 1975. Migration of chinook salmon fry from simulated incubation channels in relation to water temperature, flow and turbidity. Progressive Fish-Culturist 37(4) :2 19 223. BROODSTOCK, SPAWNING, AND EGG HANDLING 207 -. 1975. Effect of egg development at planting on chinook salmon survival. Progressive Fish-Culturist 37(4):231-2;«. _, and J. M. Shelton. 1968. Operation of Abernathy channel for incubation of salmon eggs. US Bureau of Sport Fisheries and Wildlife, Technical Paper 23. 19 p. TrojN.-xr, John R. 1977. Egg hatchability and tolerance of brook trout (Salvelinus fontinalis) fry at low pH. Journal of the Fisheries Research Board of Canada 34(2):.574-579. US Fish and Wildlife Service. 1970. Report to the fish farmers. Resource Publication 83, US Bureau of Sport Fisheries and Wildlife, Washington, D.C. 124 p. ViBF.RT, RiCH.ARD. 1953. Effect of solar radiation and of gravel cover on development, growth, and loss by predation in salmon and trout. Transactions of the American Fisheries So- ciety 83:194-201. Von B.'XYER, H. 1908. A method of measuring fish eggs. Bulletin of the US Bureau of Fisheries 28(2):1009-1014. WaITE, Di.XON, and Keen Buss. 1963. A water filter for egg- incubating units. Progressive Fish-Culturist 25(2): 107. Wales, J. H. 1941. Development of steelhead trout eggs. California Fish and Game 27(4):250-260. Waltemeyer, David L. 1976. Tannin as an agent to eliminate adhesiveness of walleye eggs during artificial propagation. Transactions of the American Fisheries Society 105(6):731-736. Weithman, a. Stephen, and Richard O. Anderson. 1977. Evaluation of flotation solutions for sorting trout eggs. Progressive Fish-Culturist 39(2):76-78. Wharton, J. C. F. 1957. A preliminary report on new techniques for the artificial fertilization of trout ova. Fisheries and Game Department, Fisheries Contribution 6, Victoria, Aus- tralia. WiTHLER, F. C, and R. M. Hl.mphreys. 1967. Duration of fertility of ova and sperm of sock- eye (Oncorhynchus nerka) and pink (0. gorbuscha) salmon. Journal of the Fisheries Re- search Board of Canada 24(7):1573-1578. Wood, E. M. 1948. Fact and fiction in spawntaking. Progressive Fish-Culturist 10(2):67-72. Wright, L. D., and J. R. Snow. 1975. The effect of six chemicals for disinfection of large- mouth bass eggs. Progressive Fish-Culturist 37 (4) :2 13-2 17. ZiMMER, P.\UL D. 1964. A salmon and steelhead egg incubation box. Progressive Fish- Culturist 26(3):139-142. ZiRGES, Malcolm H., and Lyle D. Curtis. 1972. Viability of fall chinook salmon eggs spawned and fertilized 24 hours after death of female. Progressive Fish-Culturist 34(4):190. ZOTIN, A. I. 1958. The mechanism of hardening of the salmonid egg membrane after fertiliza- tion or spontaneous activation. Journal of Embryology and Experimental Morphology 6(4):546-568. 4 Nutrition and Feeding Nutrition Nutrition encompasses the ingestion, digestion, and absorption of food. The rearing of large numbers of animals in relatively restricted areas, whether they be terrestrial or aquatic, requires a detailed knowledge of their nutritional requirements in order that they can be provided a feed adequate for their growth and health. There has not been the emphasis on rearing cultured fish as a major human food source that there has been for other livestock. Also, the quantity of fish feed required by hatcheries and commercial fish farms has not been sufficient to justify feed companies or others to spend more than a minimal amount of money for fish nutrition research. As a result, an understanding of fish nutrition has advanced very slowly. Biologists first approached the problem of feeding cultured fish by inves- tigating natural foods. Several species still must be supplied with natural foods because they will not eat prepared feeds. However, as large numbers of fish were propagated and more and more fish culture stations estab- lished, it became uneconomical or impractical to use natural feeds. Because of the limited supply and uncertain nature of artificially cultured natural food organisms, fish culturists turned to more readily available and reliable food supplies. Glandular parts of slaughtered animals were among the first ingredients used to supplement or replace natural feeds. 208 NUTRITION AND FEEDING 209 Hatchery operators also started feeding vegetable feedstuffs separately or combined with meat products to provide greater quantities of finished feed. One of the major problems was how to bind the mixtures so they would hold together when placed in the water. In the early days of fish culture, a large portion of artificial feed was leached into the water and lost. This resulted in poor growth, increased mortality, water pollution, and increased labor in cleaning ponds and raceways. The use of dry meals in the diet to reduce feed costs compounded the problem of binding feeds to prevent loss. The use of certain meat products such as spleen and liver mixed with salt resulted in rubber-like mixtures, called meat-meal feeds, that were suitable for trough and pond feeding. These were mixed in a cement or bread mixer and extruded through a meat grinder. This type of feed pro- duced more efficient food utilization, better growth, and a reduction in the loss of feeds. However, considerable labor was involved in the preparation of the meat-meal feeds. In addition, the use of fresh meat in the diet required ei- ther frequent shipments or cold storage. The ideal hatchery feed was one that would combine the advantages of the meat-meal feed, but would elim- inate the labor involved in preparation and reduce the expense of cold storage facilities. In 1959, the Oregon State Game and Fish Commission began to use a pelleted meat-meal fish feed called Oregon moist pellet (OMP), now com- mercially manufactured. .These pellets were developed because salmon would not take dry feed. Use of this feed in production was preceded by six years of research. The formula is composed of wet fish products and dry ingredients; it has a moist, soft consistency and must be stored frozen until shortly before feeding. Many hatcheries use the Oregon moist pellet as a standard production feed because it provides satisfactory feed conversion, and good growth and survival, at a competitive price. The disadvantage of the Oregon moist pel- let is that it must be transported, stored, and handled while frozen. When thawed, it deteriorates within 12 hours. By the mid 1950's, development and refinement of vitamin fortifications had made possible the "complete" dry pelleted feeds as we know them to- day. Fish feeds manufactured in the form of dry pellets solved many of the problems of hatchery operations in terms of feed preparation, storage, and feeding. There are several additional advantages to pellet feeding. Pellets require no preparation at the hatchery before they are fed. They can be stored for 90-100 days in a cool, dry place without refrigeration. When a fish swallows a pellet, it receives the ingredients in proportions that were formulated in the diet. There is evidence that fish fed dry pellets are more similar in size than those fed meat-meal. The physical characteristics of the 210 FISFi HATCHERY MANAGEMENT pellets provide for more complete consumption of the feed. Feeding rates of 0.v5 to 10% of fish weight per day reduce the chance for feed wastage. Less feed wastage results in far less pollution of the water during feeding and a comparable reduction in cleaning of ponds and raceways. Pelleted feeds are adaptable for use in automatic feeders. Many combinations of feedstuffs were tested as pelleted feeds; some failed because the pellets were too hard or too soft; others did not provide the nutrient requirements of the fish. Along with the testing and development of dry feeds, fish nutrition researchers, relying largely on information concerning nutrition of other an- imals such as chicken and mink, began utilizing and combining more and more feedstuffs. Commercial fish feeds were pelleted and marketed in advance of open- formula feeds. A few commercial feeds failed to produce good, economical growth and to maintain the health of the fish but, by and large, most were very satisfactory. Several items must be considered in developing an adequate feeding pro- gram for fish. These include the nutrient requirements for different fish sizes, species, environmental conditions, stress factors, types of feed, and production objectives. General feeding methods are important and will be discussed extensively in the last part of this section. It would be difficult to determine which factor has the greatest effect on a hatchery feeding program. In all probability, no one factor is more im- portant than another, and it is a combination of many that results in an ef- ficient feeding program. Application of the available knowledge of fish nu- trition and feeding will result in healthy, fast- growing fish and low produc- tion costs. A fish culturist must be able to recognize the factors affecting feed utilization and adapt a feeding program accordingly. Factors Influencing Nutritional Requirements The physiological functions of a fish (maintenance, growth, activity, repro- duction, etc.) govern its metabolism and, in turn, determine its nutritional requirements. Metabolism is the chemical processes in living cells by which energy is provided for vital processes and activities. WATER TEMPERATURE Apart from the feed, water temperature is probably the single most impor- tant factor affecting fish growth. Because fish are cold-blooded animals, their body temperatures fluctuate with environmental water temperatures. Negligible growth occurs in trout when the temperature decreases to 38°F. The lower limit for catfish is about 50°F. As the temperature rises, growth NUTRITION AND FEEDING 211 rate, measured as gain in wet body weight or gain in length, increases to a maximum and then decreases as temperatures approach the upper lethal limit. The best temperature for rapid, efficient growth is that at which ap- petite is high and maintenance requirements (or the energy cost of living) are low. For every 18°F increase in water temperature, there is a doubling of the metabolic rate and, as a result, an increase in oxygen demand. At the same time that oxygen demand is increasing at higher temperatures, the oxygen carrying capacity of the water decreases. The metabolic rate of the fish in- creases until the critical oxygen level is approached. Just below this point, the metabolic rate decreases. Temperature is a very important factor in establishing the nutrient re- quirements of fish. To deal with this problem, the National Research Council (NRC) reports Standard Environmental Temperatures (SET) for various species of fish. Suggested Standard Environmental Temperatures are 50°F for salmon, 59°F for trout, and 85°F for channel catfish. At these temperatures the metabolic rate for these fish is 100"o. Caloric needs increase with rising water temperatures, resulting in an increase in the fishes' appetite. The fish culturist must, therefore, adjust the feeding rate or caloric content of the feed to provide proper energy levels for the various water temperatures. Failure to make the adjustment will result in less than optimal growth and feed wastage. SPECIES, BODY SIZE, AND AGE Within the ranges of their optimal water temperatures, the energy require- ments of warmwater fish are greater than those of equally active coldwater fish of the same size. At the same water temperature, coldwater fish con- sume more oxygen than warmwater fish, indicating a higher metabolic rate and greater energy need. Carnivorous fish have a higher metabolic rate than herbivorous fish because of the greater proportion of protein and minerals in their diet. Even though fish efficiently eliminate nitrogenous wastes through the gills directly into the water, more energy is required for the elimination of wastes from protein utilization than from fats and car- bohydrates. Species that are less active have lower metabolic rates and energy requirements for activities than more active ones. In general, the energy requirements per unit weight are greater for smaller than for larger fish. Fish never stop growing, but the growth rate slows as the fish becomes older. The proportional increase in size is greatest in young fish. PHYSIOLOGICAL CHANGES Spawning, seasonal, and physiological changes affect the rate of metabo- lism. Growth rate becomes complicated with the onset of sexual maturity. 212 FISH HATC'HF.RY MANAGKMENT At this point, energy, instead of being funneled into the building of body tissues, is channeled into the formation of eggs and sperm. When sex prod- ucts are released a weight loss as much as 10-I5"/ii occurs. Fish also have high metabolic rates during the spawning season, associated with the spawning activities. Conversely, during winter, resting fish have very low metabolic rates. Fish suffering from starvation have 20% lower metabolic rates than actively feeding fish. Excitement and increased activity elevate the metabolic rates. All these affect the amount of energy which must be supplied by the feed. OTHER ENVIRONMENTAL FACTORS Factors such as water flow rates, water chemistry, and pollution can put added stresses on fish, and result in increased metabolic rates in relation to the severity of the stress. Water chemistry, oxygen content, and amount of other gases, toxins, and minerals in the water all affect the metabolic rate. For many species, darkness decreases activity and energy requirements. These fish grow better if they have "rest periods" of darkness than they do in constant light. Crowding, disease, and cultural practices also can have an affect on the metabolism and well being of fish. Digestion and Absorption of Nutrients Feed in the stomach and intestine is not in the body proper because the lining of these organs is merely an extension of the outer skin. Feed com- ponents, such as simple sugars, can be absorbed as eaten. The more com- plex components such as fats, proteins, and complex carbohydrates, must be reduced to simpler components before they can be absorbed. This breaking- down process is termed digestion. Feeds cannot be utilized by the animal until they are absorbed into the body proper and made available to the cells. Absorption of nutrients from the digestive system and movement of the nutrients within the body is a complicated process and not fully under- stood. For nutrients to be available for biochemical reactions in the cell, they must be absorbed from the digestive system into the blood for trans- port to the cells. At the cellular level, they must move from the blood into the cell. Fish also are able to obtain some required elements directly from the wa- ter, this being especially true for minerals. A brief anatomical review of a fish's digestive tract will illustrate the sites of feed digestion and absorption. The mouth is used to capture and take in feeds. Most fish do not chew NUTRITION AND FEEDING 213 their food, but gulp it down intact. Pharyngeal teeth are used by some species to grind feed. The gizzard serves as a grinding mechanism in some species of fish. The stomach is for feed storage and preliminary digestion of protein. Very little absorption occurs in the stomach. The finger-like pyloric ceca at the junction of the stomach and small intes- tines are a primary source of digestive juices. The small intestine is the major site of digestion and receives the digestive juices secreted by the liver, pancreas, pyloric ceca, and intestinal walls. The absorption of the nutrients occurs in this area. Some water absorption occurs in the large intestine, but its primary function is to serve as a reservoir of undigested materials before expulsion as feces. Oxygen and Water Requirements Oxygen and water normally are not considered as nutrients, but they are the most important components in the life-supporting processes. All vital processes require energy, which is obtained from the oxidation of various chemicals in the body. The utilization of oxygen and resulting production of carbon dioxide by the tissues is the principal mechanism for the liberation of energy. Oxygen consumption by a fish is altered by size, feed, stress, water temperature, and activity. The oxygen requirement per unit of weight decreases as fish size increases. High- nutrient feeds, density, stress, elevated water temperatures, and increased activity all increase oxy- gen requirements of fish. As a consequence, adequate oxygen must be sup- plied to assure efficient utilization of the feed and optimal growth. Water is involved in many reactions in animal systems either as a reac- tant or end product. Seventy- five percent of the gain in weight during fish growth is water. Water that is not provided in the feed itself must be taken from the environment. Because water always diffuses from the area of weakest ionic concentration to the strongest, water readily diffuses through the gills and digestive tract into freshwater fish. In saltwater fish, the blood ion concentration is weaker than that of marine water, so that the fish loses water to the environment. This forces the fish to drink the water and ex- crete the minerals in order to fulfill their requirements. A nutritionally balanced feed must contain the required nutrients in the proper proportion. If a single essential nutrient is deficient, it will affect the efficient utilization of the other nutrients. In severe cases, nutrient defi- ciencies can develop, affecting different physiological systems and produc- ing a variety of deficiency signs (Appendix F). Because all essential nu- trients are required to maintain the health of fish, there is no logic to rank- ing them in terms of importance. However, deficiencies of certain nutrients have more severe effects than of others. This is exemplified by a low level 214 FISH HATCHERY MANAGEMENT of protein in the feed resulting only in reduced growth, whereas the lack of any one of several vitamins produces well described deficiency signs. Nu- trients such as protein and vitamins should be present in feeds at levels to meet minimum requirements, but not in an excess which might be wasted or cause other health problems. The nutrients to be discussed in this chapter include (l) protein, (2) car- bohydrates, (3) fats, (4) vitamins, and (5) minerals. Protein Requirements The primary objective of fish husbandry is to produce fish flesh that is over 50% protein on a dry weight basis. Fish digest the protein in most na- tural and commercial feeds into amino acids, which are then absorbed into the blood and carried to the cells. Amino acids are used first to meet the requirements for formation of the functional body proteins (hormones, enzymes, and products of respiration). They are used next for tissue repair and growth. Those in excess of the body requirements are metabolized for energy or converted to fat. Fish can synthesize some amino acids but usually not in sufficient quan- tity to satisfy their total requirements. The amino acids synthesized are formed from materials released during digestion and destruction of proteins in the feed. Certain amino acids must be supplied in the feed due to the inability of fish to synthesize them. Fish require the same ten essential a- mino acids as higher animals: arginine; histidine; isoleucine; leucine; lysine; methionine; phenylalanine; threonine; tryptophan; valine. Fish fed feeds lacking dietary essential amino acids soon become inactive and lose both appetite and weight. When the missing essential amino acids are replaced in the diet, recovery of appetite and growth soon occurs. In fish feeds, fats and carbohydrates are the primary sources of energy, but some protein is also utilized for energy. Fish are relatively efficient in using protein for energy, deriving 3.9 of the 4.65 gross kilocalories per gram from protein, for an 84'a) efficiency. Fish are able to use more protein in their diet than is required for maximum growth because of their effi- ciency in eliminating nitrogenous wastes through the gill tissues directly into the water. Nutritionists must balance the protein and energy com- ponents of the feed with the requirements of the fish. Protein is the most expensive nutrient and only the optimal amount should be included for maximum growth and economy; less expensive digestible fats and carbohy- drates can supply energy and spare the protein for growth. Several factors determine the requirement for protein in fish feeds. These include temperature, fish size, species, feeding rate, and energy con- tent of the diet. Older fish have a lower protein requirement for maximum NUTRITION AND FEEDING 215 growth than young fish do. Species vary considerably in their require- ments; for example, young catfish need less gross protein than salmonids. The protein requirements of fish also increase with a rise in temperature. For optimal growth and feed efficiency, there should be a balance between the protein and energy content of the feed. The feeding rate determines the daily amount of a feed received by the fish. When levels above normal are fed, the protein level can be reduced, and when they are below normal it should be increased to assure that fish receive the proper daily amount of protein. Fish culturists can reduce feed costs if they know the exact pro- tein requirements of their fish. The quality, or amino acid content, is the most important factor in op- timizing utilization of dietary proteins. If a feed is grossly deficient in any of the ten essential amino acids, poor growth and increased feed conver- sions will result, despite a high total protein level in the feed. The dietary protein that most closely approximates the amino acid requirements of the fish has the highest protein quality value. Animal protein sources are gen- erally of higher quality than plant sources, but animal proteins cost more. Vegetable proteins do not contain an adequate level of certain amino acids to meet fish requirements. Synthetic free amino acids can be added to feed, but there is still some question as to how well fish utilize them. Thus, ami- no acid balance at reasonable cost is best achieved by using a combination of animal proteins, particularly fish meal, and vegetable proteins. Fish meal seems to be the one absolutely essential feed item. Most of the ingredients of standard catfish feed formulas can be substituted for, but whenever fish meal has been left out poorer growth and food conversion have resulted. Fish cannot utilize nonprotein nitrogen sources. Such nonprotein nitro- gen sources as urea and di-ammonium citrate, which even many non- ruminant animals can utilize to a limited extent, have no value as a feed source for fish. They can be toxic if present in significant levels. The chemical composition of fish tissue can be altered significantly by the levels and components of ingredients in feeds. Within limits, there is a general increase in the percentage of protein in the carcass in relation to the amount in the feed. Furthermore, there is a direct relation between the percentage of protein and that of water in the fish body. A reduction of body protein content in fish is correlated with increased body fat; fish fed lower- protein feeds have more fat and less protein. PROTEIN IN SALMONID FEEDS The protein and amino acid requirements for salmon and trout are similar. The total protein requirements are highest in initially feeding fry and de- crease as fish size increases. To grow at the maximum rate, fry must have a 216 FISH HATCHERY MANAGEMENT feed that contains at least 50''] protein; at 6—8 weeks the requirement de- creases to 40*: of the feed and to about 35% of the feed for yearling sal- mo nids. Recor :ein levek in trout feeds as percent of the diet are: Starter feed fi:y 45—55% Grower feed fingerlings 35-5% Production feed (older fish 30-40% The level of protein required in feed varies with the quality- and propor- tions :: -^ -:i. r:::e:rLi ihat make up the feed. Between 0.5 and 0.7 pound ;tary- protein is re: _ ri :o produce a pound of trout fed a balanced jjatcherv rf £ The requireiiient for protein is also temperature- dependent. The opcLn^ prote:- 'rr'. :- :'-e fe^d for chinook salmon is 4-0 ai 47"F ?? : rzrv rv catts:-: 7zzds T-r 7^\^:^ :::i5 ;: ri::-;- ire rich •'- T-r-ein. Catfish may mecaboiize 5-:me i r.^r i:::f - :;: r'rrr- Prcte.r .. .:zarion is affected by the pro- -r - ;:_.-:f i.-i ■• i:f: :-rmrer3.r.:rr. L'-'-t :-:::5h convert the best animal z:.- 7 ::_::t ::;- —.-.- : : :. — r; z-..-: :-iz :hey do the best plant --rzr. soyiea.- mei.. I: li - r ::hy thai a combination of protein ii-rirs T I: iT-r: wrs- "zziwz. Tites :L=.- a.- • wz.z-- source. In catfish :eeas. a: --'. ' :: .-r iir.ir. i- "r - tt:. :t — t-: should be animal reins w-e- :-r;. ire red a: cem.- '"'F cr ce.i'A. Hc-rt'e% er. a mix- . _-.^v at both extremies. The pax- - "r pr::rm z-z . Z'—.rri ::: :i:::3- i:^ i : size-rr.i:^ Frv :: : 'irz - z\ \'-^'i 1 Fi-r : - .:- :s 25-^5^ \^rT- :i -r t1 ii mu:- 2^ me- «;!. ea.i. izi -t reed is bala.i:- xununojc axd feeding 217 beneficial in this regard. The amino acid requirements for catfish have not been established, but appear to be similar to those for salmonids. Catfish feeds — or any feeds fed in extensive culrure — are classified as either complete or supplemental diets. Complete feeds are formulated to contain all the \"itamins. minerals, protein, and energ^" needed by the fist. Usually these complete feeds contain 30 to -iO'i total crude protein, of which fish meal may make up 10 to 25^': of the feed. Complete feeds are more expensive than supplemental feeds. Complete feeds are fed to fry, and also to larger fish raised intensively in race\*"ays, cages, or other en\ixonments where the intake of natural feeds is restricted. Supplemental feeds are formulated to pro\ide additional protein, energy, and other nutrients to fish utilizing natural food. Generally, the fish are expected to eat natural food organisms to supply ifce essential growth fac- tors absent in the feed. Usually supplemental feeds contain a lower level of crude protein than complete feeds, and soybean meal is the principal pro- tein source. Low stocking rates and low standing crops of fish result in more natural food and protein being available to each fish. The above factors and oth- ers, such as season, fish size, feeding rate, water temf>erature, oxygen lev- els, and disease influence the dietary- protein levels required for maximum efficiency in growth. Consequently, no one protein level in feeds "v*"ill meet all conditions and it remains for the fish culturist to choose the feed viith a protein level that \*ill satisfy' production needs. PROTEIN IN COOLW.\TER FISH FEEDS Feeding trials \*ith northern pike, chain pickerel, muskellunge, vt-alle\-e, and the hybrid tiger muskellunge showed that the hybrid and. to a lesaer degree, northern pike v^ill accept a dr\ pelleted, formulated feed. A 50'*- protein e.xperimental feed Appendix F formulated specifically for cool- water fish provided the highest survival and growth •with fingerlings. Trout feeds and exf)erimental feeds that contain less protein were inadequate. Therefore, ii appears that the protein requirement for the fingerlings of these species is about 50*t of the feed. It is also noteworthy that 60-SO V of the dietarx protein was supplied by animal protein sources in feeds that proved satisfiactor>\ Only limited testing has been conducted on feeding advemced fingerlings of coolwater species, but indications are that the pro- tein level of the feed can be reduced. This follows the similar pattern for trout and catfish. Car bo hydra U Rfquirfmrnts Carbohydrates are a major source of energy to man and domestic animals, but not to salmonids or catfish. Onlv limited information is av^ailable on 218 FISH HATCHF.RY MANAGEMF.NT the digestibility and metabolism of carbohydrates by fish. All of the neces- sary enzymes for digestion and utilization of carbohydrates have been found in fish, yet the role of dietary carbohydrates and the contribution of glucose to the total energy requirement of fishes remain unclear. There is little carbohydrate (usually less than 1.0"/ii of the wet weight) in the fish body. After being absorbed, carbohydrates are either burned for energy, stored temporarily as glycogen, or formed into fat. Production of energy is the only use of carbohydrates in the fish system. No carbohydrate requirements have been established for fish because carbohydrates do not supply any essential nutrients that cannot be obtained from other nutrients in the feed. The energy requirement of a fish may be satisfied by fat or protein, as well as by carbohydrate. If sufficient energy nutrients are not available in the feed the body will burn protein for energy at the expense of growth and tissue repair. The use of carbohydrate for energy to save protein for other purposes is known as the "protein- sparing effect" of carbohydrate. Carbohydrate energy in excess of the immediate energy need is convert- ed into fat and deposited in various tissues as reserve energy for use during periods of less abundant feed. Quantities in excess of needed levels lead to an elevated deposition of glycogen in the liver, and eventually will cause death in salmonids. Fat-infiltrated livers and kidneys in salmonids are a result of fat deposi- tion within the organ, resulting in reduced efficiency and organ destruc- tion. This condition results primarily from excess levels of carbohydrates in the feed. Carbohydrates also may serve as precursors for the various metabolic in- termediates, such as nonessential amino acids, necessary for growth. Thus, in the absence of adequate dietary carbohydrates or fats, fish may make inefficient use of dietary protein to meet their energy and other metabolic needs. In addition to serving as an inexpensive source of energy, starches improve the pelleting quality of fish feeds. Dietary fiber is not utilized by fish. Levels over 10% in salmonid feeds and over 20% in catfish feeds reduce nutrient intake and impair the digesti- bility of practical feeds. CARBOHYDRATES IN SALMONID FEEDS Carbohydrates are an inexpensive food source, and there is a temptation to feed them at high levels. However, trout are incapable of handling high dietary levels of carbohydrates. The evidence for this is the accumulation of liver glycogen after relatively low levels of digestible carbohydrate are fed. Trout apparently cannot excrete excessive dietary carbohydrate. In higher animals, excessive carbohydrate is excreted in the urine. Such ex- cretion does not occur in trout even though the blood sugar is greatly in- NUTRITION AND FEEDING 219 creased. In trout, the accumulation of blood glucose follows the same pat- tern as that in diabetic humans. No absolute carbohydrate requirements have been established for fish. Trout nutritionists have placed maximum digestible carbohydrate values for feeds at 12-20"o. Digestible carbohydrate values are determined by multiplying the total amount of carbohydrate in the feed by the digestibil- ity of the carbohydrates. Digestibility values of various carbohydrates are: simple sugars, 100%; complex sugars, 90%; cooked starch, 60%; raw starch, 30%; fiber, 0%. Digestible carbohydrate levels over 20''o in trout feeds will cause an ac- cumulation of glycogen in liver, a fatty infiltrated liver, fatty infiltrated kidneys, and excess fat deposition, all of which are detrimental to the health of the fish. Levels of carbohydrates up to 20"ii can be tolerated in trout feeds in 55-65°F water. These same feeds fed in water below 50°F will cause exces- sive storage of glycogen in the liver and can result in death. Carbohydrates should, therefore, be limited in trout feeds. However, there are definite beneficial effects from the carbohydrate portion of the feed. It can supply up to 20"i) of the available calories in a feed, thus sparing the protein. The energy from carbohydrates available to mammals is 4 kilocalories per gram, whereas the value for trout is only 1.6 kcal/g, a 40%i relative efficiency. Most trout feeds do not contain excessive amounts of digestible carbohy- drate. A balance between plant and animal components in the feeds gen- erally will assure a satisfactory level of digestible carbohydrate. The major sources of carbohydrate in trout feeds are plant foodstuffs, including soy- bean oil meal, cereal grains, flour by-products, and cottonseed meal. Most animal concentrates such as meat meals, fish meals, tankage, and blood meals, are low in carbohydrate (less than 1.0%). The high percentages of milk sugar in dried skim milk, dried buttermilk, and dried whey may cause an increase in blood sugar and an accumulation of glycogen in the liver if fed at levels greater than lO"" of the feed. Pacific salmon have been reported to tolerate total dietary carbohydrate levels as high as 48"(i, with no losses or liver pathology. The digestible car- bohydrate value would be lower, depending on the forms of the carbohydrate. CARBOHYDRATES IN CATFISH FEEDS Dietary carbohydrates are utilized by catfish, but only limited information is available on their digestibility and metabolism. Channel catfish utilize starches for growth more readily than sugars. In feeds containing adequate protein, fish weight increases with the level of starch, but remains essential- ly the same regardless of the amounts of sugar in the feed. Liver abnormal- ities, poor growth, and high mortality observed in salmonids due to high levels of dietary carbohydrates have not been found in catfish. 220 FISH HAICIIKRV MANAGEMENT No carbohydrate requirements have been estabHshed for catfish; how- ever, carbohydrates can spare protein in catfish feeds. In the absence of adequate dietary carbohydrates or fats, catfish make inefficient use of dietary protein to meet their energy and other metabolic needs. In channel catfish, lipids and carbohydrates appear to spare protein in lower-energy feeds but not in higher-energy feeds. Fiber is an indigestible dietary material derived from plant cell walls. Fiber is not a necessary component for optimum rate of growth or nutrient digestibility in channel catfish production rations. Fiber levels as high as 21% reduce nutrient intake and impair digestibility in feeds for channel catfish. Fiber in concentrations of less than 8% may add structural integrity to pelleted feeds, but larger amounts often impair pellet quality. Most of the fiber in the feed ultimately becomes a pollutant in the water. Lipid Requirements Lipids comprise a group of organic substances of a fatty nature that in- cludes fats, oils, waxes, and related compounds. Lipids are the most con- centrated energy source of the food groups, having at least 2.25 times more energy per unit weight than either protein or carbohydrates. In addition to supplying energy, lipids serve several other functions such as reserve ener- gy storage, insulation for the body, cushion for vital organs, lubrication, transport of fat-soluble vitamins, and maintenance of neutral bouyancy. They provide essential lipids and hormones for certain body processes and metabolism, and are a major part of reproductive products. Although each fish tends to deposit a fat peculiar to its species, the diet of the fish will alter its type. The fat deposited tends to be similar to the fat ingested. The body fat of fish consuming natural foods contains a high degree of polyunsaturated (soft) fats similar to those in the food. Because natural fats are soft fats that are mobilized and utilized by the fish more ef- ficiently than hard (saturated) fats, soft fats are beneficial for efficient pro- duction and fish health. Preliminary studies have indicated that some hard fats can be used by warmwater fish. The effect of water temperature on the composition of the body fat of fish is difficult to define clearly due to its influence on the digestibility of hard and soft fats. Soft fats are digested easily in both warm and cold wa- ter, but hard fats are digested efficiently only in warm water. Fish living in cold water have body fats that are highly unsaturated with a low melting point. These fish are able to more readily adapt to a low environmental temperature. Factors to be considered in evaluating dietary lipids for fish feeds in- clude digestibility, optimal level in the feed, content of fatty acids essential NUTRITION AND FKEDING 221 for the fish, presence of toxic substances, and the quality of the lipid. Fish and vegetable oils that are polyunsaturated are more easily digested by fish than saturated fats such as beef tallow, especially at colder temperatures. The optimal level of dietary lipid for fish feeds has not been established. Protein content of the feed, and type of fat need to be considered in deter- mining the amount to be used in the feed for a given fish species. Lipids are a primary source of energy for fish and have a protein- sparing effect. Therefore high levels in the feed would be beneficial. However, high fat levels in the feed can hamper the pelleting of feeds and cause rapid spoilage of feed during storage. Rancidity of lipids, especially of polyunsaturated oils, due to oxidation can be a problem in fish feeds. Rancid lipids have a disagreeable odor and flavor and can be toxic to fish. The toxic effects may be due to products of the oxidation of the lipid itself or to secondary factors such as destruction of vitamins or mold growth. Oxidation of lipids in the feed often results in the destruction of vitamins, especially vitamin E. The oxidation process also produces conditions that favor mold growth and breakdown of other nutrients. Because rancid lipids in the feed are detrimental to fish, every ef- fort should be made to use only fresh oils protected with antioxidants. Feeds should be stored in a cool, dry area to minimize oxidation of the lipids in the feeds. Contamination of fish feeds, especially those for fry and broodstock, with pesticides and other compounds such as polychlorinated biphenols (PCB) cause many health problems and may be lethal in fish. Fish oil is a com- mon source of contaminants in fish feeds. Because most contaminants are fat-soluble they accumulate in the fatty tissues of fish. When fish oil is ex- tracted from fish meal, these compounds are concentrated in the oil. Fish used in the production of fish meal and oil pick up these compounds from their natural foods in a contaminated environment. Feed manufacturers should select only those fish oils that contain low levels or none of these compounds. Vegetable oils, which are naturally free of these compounds, also can be used. LIPID REQUIREMENTS FOR SALMONIDS When there is little or no fat in the feed, a trout forms its own fat from car- bohydrates and proteins. The natural fat of a trout is unsaturated with a low melting point. Practical-feed formulators use fish oil and vegetable oil in trout feeds as the primary energy source. These oils are readily digested by the trout and produce the desired soft body fat. Hard fats such as beef tallow are not as readily digested because they are not emulsified easily, especially in cold temperatures. Hard fats can coat other foods and reduce their digestibility, thus lowering the performance of the feed. Very hard fats may plug the intestines of small trout. 222 FISH HATCHERY MANAGEMENT Body fat of a hatchery trout fed production feeds is harder (more satura- ted) than that of a wild trout, but after stocking the body fat gradually changes to a softer (unsaturated) type. This can be attributed to both the change in environment and feed. Linolenic fatty acids (omega-3 type) are essential for trout and salmon, and should be incorporated at a level of at least 1% of the feed for max- imum growth response. This may be supplied by the addition of 3-5% fish oil or 10% soybean oil. The level of dietary lipid required for salmon or trout depends on such factors as the age of the fish, protein level in the feed, and the nature of the supplemental lipid. The influences of age of the fish and protein level of the diet are interrelated; young trout require higher levels of both fat and protein than older trout. For best performance, the recommended per- centage of fat and protein for different ages of trout and salmon should be as follows: % protein % fat Starter feeds (fry) 50 15 Grower feeds (fingerlings) 40 12 Production feeds (older fish) 35 9 Hatchery personnel can check the protein and fat content of trout feeds ei- ther on the feed tag for brand feeds or in the feed formulation data for open-formula feeds to determine if these recommended nutrient levels are being supplied by the feed they are using. High levels of dietary fat and, to a lesser degree, excess protein or car- bohydrates can cause fatty infiltration of the liver. Fatty infiltrated livers are swollen, pale yellow in color, and have a greasy texture. The level of fat in affected livers may be increased to several times greater than normal. This condition usually is accompanied by fatty infiltration of the kidney and can lead to edema and death by reducing the elimination of wastes through the urinary system. Fatty infiltrated livers should not be confused with fatty degeneration of the liver or viral liver degeneration. Fatty degeneration of the liver is caused by toxins from rancid feeds, chemical contaminates, certain algae, or natural toxins. This condition is typified by acute cellular degenerative changes in the liver and kidney. The liver is swollen, pale yellow in color with oil droplets in the tissue, but does not feel greasy (Figure 7l). Rancid fats in feeds stored for long periods (more than six months) or under warm, humid conditions are the primary cause of this disorder in hatchery- reared trout. Rainbow trout are most severely affected and brook trout to a lesser degree, but brown trout are rarely affected by rancid oils in the feed. Viral liver degeneration differs from the others by the presence of small hemor- rhagic spots in the liver and swelling of the kidney. Anemia is characteris- tic of advanced stages of all three liver disorders. NUTRITION AND FEEDING 223 Figure 71. Rainbow trout with liver lipoid degeneration (ceroidosis) of increasing severity from top to bottom. Note yellowish- brown coloration of livers of middle and bottom fish. (Courtesy Dr. P. Ghittino, Fish Disease Laboratory, Tonino, Italy.) Figure 72. Folic acid-deficient (top) and control (bottom) coho salmon. Note the extremely pale gill, demonstrating anemia, and exophthalmia in folic acid-deficient fish. (Courtesy Charlie E. Smith, FWS, Bozeman, Montana.) 224 FISH HAICHKRY MANAGEMENT LIPID REQUIREMENTS FOR CA lEISH Lipid level and content of essential fatty acids have received little con- sideration in diets for channel catfish, because little is known about the ef- fects of, and requirements for, these nutrients in catfish. In practice, the dietary requirements have been met reasonably well by lipids in the fish meal and oil-rich plant proteins normally used in catfish feeds and those in natural food organisms available in ponds. Weight gain and protein deposition increase as the level of fish oil is elevated to 15'^ of the dry feed. At the 20'}(i level, the gain decreases. Cat- fish fed corn oil did not gain as well as those fed fish oil in the feed, show- ing that fish oil is a better source of dietary lipid. Beef tallow, safflower oil, and fish oil were evaluated at temperatures from 68 to 93°F. Maximum growth was obtained at 86°F by catfish fed each lipid supplement. Highest gains and lowest food conversion rates were obtained with fish oil, followed by beef tallow and safflower oil. As with salmonids, catfish have little or no requirement for linoleic (omega-6) fatty acids in the feed. No requirements for essential fatty acids in catfish feeds have been determined. Commercial catfish feeds contain less than 8% dietary lipids. Test feeds with 10% lipid provided the best growth, whereas 167(1 in the feed did not improve growth or enhance protein deposition. Lipids have the most effect on taste and storage quality of fish products. Tests with animal and vegetable fats showed that fish oil has a significant adverse effect on the flavor of fresh and frozen fish. Beef tallow also influ- enced the flavor, but did not induce the "fishy" flavor produced by the fish oil. Fish reared on safflower oil or corn oil have a better flavor than those fed beef tallow or fish oil. Catfish producers may be able to use an- imal fats and oils in fingerling feeds to obtain rapid growth and efficient deposition of protein, then change to a finishing diet made with vegetable oils to improve the flavor as the fish approach market size. Energy Requirements Energy is defined as the capacity to do work. The work can be mechanical (muscular activity), chemical (tissue repair and formation), or osmotic (maintenance of biological salt balance). Fish require energy for growth, ac- tivity, reproduction, and osmotic balance. Energy requirements of species differ, as do their growth rates and activities. Other factors that alter the energy requirements are water temperature, size, age, physiological activity, composition of the diet, light exposure, and environmental stresses. Food energy is usually expressed as kilogram calories (kcal or Cal). It is released in two forms, heat energy and free energy, in animal systems. Heat energy has the biological purpose of maintaining body temperature in NUIRITION AND FEEDING 225 warm-blooded animals, but this is of less importance to fish because a fish's body temperature corresponds to environmental water temperatures. Usual- ly, the body temperature of a resting fish will be at or near the environ- mental water temperature. Free energy is available for biological activity and growth and is used for immediate energy and for formation of body tis- sue or is stored as glycogen or fat. Fish adjust their feed intake according to their energy needs. An exces- sively high energy level in a feed may restrict protein consumption and subsequent growth. Except for the extremes, fish fed low-energy feeds are able to gain weight at a rate comparable to those fed high-energy feeds by increasing their feed intake. If a feed does not contain sufficient nonprotein energy sources to meet the fish's energy requirements then the protein nor- mally used for growth will have to be used for energy. Therefore, it is diffi- cult to determine a specific energy or protein requirement without consid- ering the relative level of one to the other. Absolute figures on optimum energy requirements are difficult to state in fish nutrition because fish can be maintained with little growth on a low-energy intake or be forced to produce more weight by feeding them in excess. To maintain optimum growth and the efficiency of a feeding program, the feeding level should be adjusted if energy levels of the feeds vary significantly. The feeding level should be increased for low-energy feeds and decreased for high-energy feeds. Energy needs for maintenance increase with rising water tempera- tures and decrease when temperatures are reduced, thus requiring changes in the feeding rates. However, more energy is required to produce weight gains of fish at lower temperatures than at high temperatures. Fish normally use about 70"" of the dietary energy for maintenance of their biological systems and activity, leaving about 30"o available for growth. Energy requirements for vital functions must be met before energy is available for growth. A maintenance- type feeding program is designed to supply the minimum energy and other essential nutrients for the vital func- tions and activity, with no allowance for growth. Dietary efficiency or feed conversion are terms used to designate the practical conversion of food to fish flesh. In this concept of estimating gross energy requirements, the amount of food (energy) required to produce a unit of weight gain is deter- mined. In general, if the conversion of food to fish flesh is two or less, en- ergy requirements are being met. This is because energy for biological maintenance of fish must be supplied before energy is available for growth. ENERGY REQUIREMENTS FOR SALMONIDS Brook, brown, rainbow, and lake trout have similar energy requirements. Between 1,700 and 1,800 available dietary kilocalories are required to pro- duce a pound of trout, depending upon the feed being fed and conditions under which the fish are reared. The amount of available calories from fish feeds depends upon the digestibility of nutrients by the fish. 226 FISH HATCHERY MANAGEMENT Gross Available kcal Digestibility kcal Nutrient (per gram) (percent) (per gram) Protein 5.6 70 3.9 Fat 9.4 85 8.0 Carbohydrate 4.1 40 1.6 The values above show that salmonids make more efficient use of energy from fats than from proteins, and least efficient use of carbohydrates. There is evidence that trout must use some protein for energy. In trout feeds, between 55 and 65% of the total available dietary calories are from the pro- tein. The available calories in 100 grams of a salmon or trout production feed can be calculated as follows: Percent Available Energy Nutrient of feed kcal content Protein 45% X 3.9 175.5 kcal Fat 10% X 8.0 80.0 kcal Moisture 10% X 0 0.0 kcal Ash 10% X 0 0.0 kcal Carbohydrates 25% X 1.6 40.0 kcal Total = 295.5 kcal/100 grams or 1,341 kcal/pound An estimated conversion can be calculated for salmonids by using the energy requirement to produce a pound of fish and the available calories in the feed. kcal to rear a pound of trout (l,700) , 0-7 r i ' -. r = 1.27 teed conversion Available kcal per pound of feed (1,341) ENERGY REQUIREMENTS FOR CATFISH Available kilocalories required to produce a pound of catfish vary from 881 to 1,075, depending on the feed and size of fish. Growth and feed conver- sions demonstrate that larger catfish require lower levels of protein and higher levels of energy than smaller catfish. Nutrient digestibility and en- ergy values for catfish are: Gross Available kcal Digestibility kcal Nutrient (per gram) (percent) (per gram) Protein 5.6 80 4.5 Fat 9.4 90 8.5 Carbohydrate 4.1 70 2.9 NUTRITION AND FEEDING 227 The available calories in catfish feeds and estimated feed conversions can be calculated by the same procedures as for salmonid feeds, with appropri- ate values for catfish being substituted. Vitamin Requirements Vitamins are not nutrients, but are dietary essentials required in small quantities by all forms of plant and animal life. They are catalytic in na- ture and function as part of an enzyme system. For convenience, vitamins are broadly classified as fat-soluble vitamins or water-soluble vitamins. The fat-soluble vitamins usually are found asso- ciated with the lipids of natural foods and include vitamins A, D, E, and K. The water soluble vitamins include vitamin C and those of the B com- plex: thiamine (B,), riboflavin (B^), biotin, folic acid, cyanocobalamin (B12) and inositol. Vitamins are distributed widely in ingredients used in fish feeds. Some, such as yeast, contain high levels of several vitamins. The level of vitamins supplied by the ingredients in the feed usually is not adequate to meet the fishes' requirements. These requirements are presented in Table 24. Most Table 24. vitamin requirements expressed as milligrams or interna- tional UNITS (lU) PER POUND OF DRY FEED FOR SALMONIDS AND WARMWATER FISHES. (SOURCE: NATIONAL RESEARCH COUNCIL 1973, 1977.) WARMWATER FISHES SUPPLEMENTAL COMPLETE vitamin SALMONIDS FEED FEED A (lU) 908 908 2,497 DgdU) n 100 454 E (lU) 13.6 5 22.7 K 36.3 2.3 4.5 Thiamine 4.5 0 9.1 Riboflavin 9.1 0.9-3.2 9.1 Pyridoxine 4.5 5 9.1 Pantothenic acid 18.2 3.2-5 22.7 Biotin 0.45* 0 0.04 Choline 1362 200 250 Vitamin B12 0.009 0.0009-0.004 0.009 Niacin 68 7.7-12.7 45.4 Ascorbic acid 45.4 0-45.4 13.6-45.4 Folic acid 2.3 0 2.3 Inositol 182 0 45.4 Required level is not established. Brown trout require twice the level presented. 228 FISH HATCHERY MANAGEMENT vitamins can be manufactured synthetically; these are both chemically and biologically the same as naturally occurring substances. Synthetic vitamins can be added to feeds with great precision as a mixture (referred to as a premix) to complement the natural vitamins and balance the vitamin con- tent of the finished feed. Calculations of the vitamin levels to be placed in feeds should provide for an excess, for several reasons: (l) the efficiency with which fish use the vitamins in ingredients is unknown; (2) vitamins in fish feeds are destroyed by heat and moisture primarily during manufacturing but also during storage; (3) breakdown of other substances in the feed (such as oxidation of oils) may destroy some vitamins; and (4) vitamins react with other com- pounds and become inactive. Several vitamins show moderate to severe losses when incorporated into feeds and stored at different temperatures and relative humidities. Among them are vitamins A, D, K, C, E, thiamine, and folic acid. Vitamin C (as- corbic acid) has received considerable attention. Typical losses of vitamin C in feeds are: Storage Feed Temperature Duration Loss Catfish feeds (dry) 70°F 3 months 50% Oregon moist pellet — 14°F 3 months None 40-46°F 3 days 85% 70°F 11 hours 81% Assays performed on Oregon moist pellet that had been stored 5 months and then thawed for 14 hours showed reductions of vitamin levels as fol- lows: Change in Vitamin concentration (mg/kg diet) C 893 to 10 E 503 to 432 K 18.6 to 2.0 Folic acid 7.1 to 5.3 Pantothenic acid 106 to 99 Vitamin E is reduced continually from the time the feed is manufactured until it is fed, due to oxidative rancidity of oils in the feed; vitamin E serves as an antioxidant. For these reasons, all feeds should be used within NUTRITION AND FEEDING 229 a 3-month period if at all possible. It is important to store fish feed in a cool dry place and to avoid prolonged storage if fish are to be provided with levels of vitamins originally formulated into the feed. Steps can be taken to help preserve the vitamins in the feed. Some synthetic vitamins can be protected by a coating of gelatin, fat, or starch. The addition of an- tioxidants reduces the oxidation of oils and its destructive effect on vita- mins. Maintaining cool, dry storage conditions to eliminate spoilage and mold growth preserves the feed quality and vitamins. Because the metabolic processes and functions of biological systems of fish are similar to those of other animals, it is safe to assume that all vita- mins are required by all species. However, the recommended amounts of the vitamins for different fishes vary. The required levels of vitamins must be added to the ration routinely in order to prevent deficiencies from oc- curring (Figures 72 and 73). Deficiencies of most known vitamins have been described (Appendix F). The total amount of vitamins required by a fish increases as the fish grows. Conversely, food intake decreases as a percent of body weight as the fish increases in size, which can cause a vitamin deficiency if the feed con- tains only the minimum level of vitamins. Therefore, feeds for older fish also need to be fortified with vitamins. As temperature decreases, so does food intake. However, the vitamin re- quirements of fish do not decrease proportionally. A vitamin deficiency can occur with low intake of diets containing marginal levels of vitamins. Complete catfish feeds are formulated to contain all of the essential vita- mins in amounts required by the fish and are designed to provide normal growth for fish that do not have access to natural feeds. Supplemental feeds contain the vitamins supplied by the feed ingredients plus limited supple- mentation, as the fish are expected to obtain vitamins from natural foods in the pond. Mineral Requirements As nutrients in fish feeds, minerals are difficult to study. Absorption and excretion of inorganic elements across the gills and skin have an osmoregu- latory as well as a nutritional function. Absorption of inorganic elements through the digestive system also affects osmoregulation. The specific qualitative and quantitative dietary needs will, therefore, depend upon the environment in which the fish is reared and on the type of ration being fed. Dietary requirements for most minerals have not been established for fish, but fish probably require the same minerals as other 230 FISH HATCHERY MANAGEMENT ^-"'^ Figure 73. Gill lamellae from (l) a normal and (2) a pantothenic acid-deficient rainbow trout. Hyperplasia of the epithelium has resulted in fusion of most lamellae (arrow) on two filaments of the pantothenic acid-deficient trout. (Cour- tesy Charlie E. Smith, FWS, Bozeman, Montana.) animals for growth and various metabolic processes. As mentioned, fish also use mineral salts and ions to maintain osmotic balance between fluids in their body and the water. Many minerals are essential for life, but not all are needed in the same amount. Seven major minerals are required in large amounts and constitute 60 to 80% of all the inorganic materials in the body. The seven are calci- um, phosphorus, sulfur, sodium, chlorine, potassium, and magnesium. NUTRITION AND FEEDING 231 Trace minerals are just as essential as major minerals, but are needed only in small amounts. The nine essential trace minerals are iron, copper, iodine, manganese, cobalt, zinc, molybdenum, selenium, and fluorine. Mineral elements, both major and trace, are interrelated and balance each other in their nutritional and physiological effects. The minerals that form the hard and supporting structures of a fish's body (bone and teeth) are principally calcium and phosphorus. Very small amounts of fluorine and magnesium also are essential for the formation of bones and teeth. For normal respiration iron, copper, and cobalt are required in the red cell and deficiencies of any of these trace elements may cause anemia. Sodium, chlorine, and potassium play an important role in regulating body processes and osmotic pressure. Minerals also are required for reproduc- tion. They are removed from the female system during egg production and must be replenished by adequate amounts in the feed. Most researchers agree that fish require all of the major and trace ele- ments. Under normal conditions, chloride ions are exchanged very rapidly from both food and water. Calcium and cobalt are absorbed efficiently from the water but are utilized poorly from feeds. The level of calcium in the water influences the uptake of the calcium from the food, and vice versa. Feeds are a major source of phosphorus and sulfur. Inorganic phosphorus is absorbed efficiently from the stomach and intestine of trout. The skin (including the scales) in trout is a significant storehouse for calcium and phosphorus. Only one mineral deficiency is recognized definitely in trout; as in higher animals, a deficiency of iodine causes goiter. The study of the mineral requirements of fish is incomplete, but it is apparent that both dis- solved and dietary minerals are important to the health and vigor of fish. Nonnutritive Factors Although nonnutritive factors do not contribute directly to the mainte- nance, growth, or reproduction of fish, they should be considered in the formulation of rations as they can affect feed efficiency and the quality of the final marketable product. Three nonnutritive factors — fiber, pigment- producing factors, and antioxidants — warrant discussion concerning fish nutrition. FIBER Due the simple structure of the gastrointestinal tract of fish, the digestibil- ity of fiber in fish is extremely low, less than 10"o. Very little microbial 232 FISH HATCHERY MANAGEMENT breakdown of fiber has been noted. Herbivorous fish can tolerate higher amounts of fiber than carnivores. It is recommended that crude fiber not exceed 10% in fish feeds and preferably not more than 5 or 6%. Some fiber is useful, however, because it supplies bulk and facilitates the passage of food through the fish. PIGMENT-PRODUCING FACTORS Often, producers wish to add color to fish in order to make their product more attractive to the consumer. This can be achieved through food addi- tives. Paprika fed at Tin of the feed will improve the coloration of brook trout. Xanthophylls from corn gluten meal, dried egg products, and alfalfa meal will increase yellow pigmentation of brown trout skin. Shrimp or prawn wastes, which contain carotinoids, produce a reddish coloration when fed to trout. Where regulations allow, canthaxanthin can be incor- porated into trout feeds to impart a red color to the flesh and eggs. Species differences have been observed, and it is possible to develop color in one species of fish, but not another. ANTIOXIDANTS Fish feeds contain high levels of unsaturated oils which are easily oxidized, resulting in breakdown of oils and other nutrients. This can be controlled by the addition of antioxidants such as butylhydroxytoluene (BHT), bu- tylhydroxyanisole (BHA), ethoxyquin, and vitamin E. The levels of BHT, BHA, and ethoxyquin allowed in feeds by regulations often are not ade- quate to control oxidation of the high levels of unsaturated oils in fish feeds. Therefore, feed formulators should add antioxidants to the levels permitted by the regulations to protect the oils in fish feeds and supple- ment with vitamin E if additional antioxidation is needed. Ethoxyquin and vitamin E are biological antioxidants that function in the fish's physiologi- cal system as well as in feed preservation. The level of vitamin E in fish feeds must be adequate to prevent oxidation of oils and still meet the nu- tritional requirement of the fish. Materials Affecting Fish Quality and Flavor Fish fed wet feeds containing meat or fish products tend to deposit higher levels of body fat and have soft textured flesh, whereas those fed dry feeds have a more desirable flavor and firmer flesh. Fresh fish in feeds can im- part an off- flavor to the flesh of the fish eating it. NUTRITION AND FEEDING 233 Other substances such as algal blooms, muskgrass, chemicals, and organic compounds can produce undesirable flavors in fish. When the water tempera- ture is high, as it is in late summer, there is a greater chance that off-flavors will occur in fish flesh. Organic Toxicants in Feeds Numerous naturally occurring and synthetic organic compounds produce toxic responses in fish. Tannic acid, aflatoxin, and cyclopropenoid fatty acids all induce liver cancer in fish. Gossypol, a toxin present in untreated cot- tonseed meal, causes anorexia and ceroid accumulation in the liver. Phytic acid, which ties up zinc in the feed, and growth inhibitors found in soybean meal can be destroyed by proper heating during processing. Chlorinated hydrocarbons occur as contaminants of fish meal and can cause mortality when present in fry feeds. Broodfish transfer these compounds from the feed to their eggs, resulting in low hatchability and high mortality of swim- up fry. Toxaphene affects the utilization of vitamin C in catfish and can cause the "broken back syndrome." The environment and feed should be free of toxi- cants to maintain the health and efficient production of fish. Symptoms of some organic toxicants are given in Appendix F. Sources of Feeds NATURAL FOODS As the name implies, natural foods are obtained from the immediate en- vironment. Small fish feed upon algae and zooplankton. As the carnivorous fish grow, they devour progressively larger animals — insects, worms, mol- lusks, crustaceans, small fish, tadpoles, and frogs. Many fish remain her- bivorous throughout their lives. Pondfish culturists take advantage of the natural feeds present in still waters. The composition of insects, worms, and forage fish used as fish food is mostly water (75-80"o). The remaining components are protein (l2-15%), fat (3-7%), ash (l-4"(i), and a little carbohydrate (less than 1%). During warm weather when insects hatch and bottom organisms are abundant, a pond can provide a considerable amount of feed for fish. This production can be increased by pond fertilization. Because the environment tends to be highly variable in its production of biomass, natural methods of provid- ing food are inefficient unless the producer is utilizing large bodies of wa- ter. Natural food organisms are relied upon to provide nutrients lacking in the supplemental feeds used in pond culture. 234 FISH HMCHERY MANAGEMENT FORMULATED FEEDS Formulated feeds are a mixture of ingredients processed into pellets, granules, or meals and may be either supplemental or complete rations. Supplemental feeds are formulated to contain adequate protein and en- ergy, but may be deficient in vitamins and minerals which the fish are ex- pected to obtain from natural foods. Such feeds are fed to catfish and other fish reared at low densities in ponds. Complete feeds are formulated to provide all essential vitamins and nu- trients required by fish and are designed to provide optimal growth. If high densities of fish are being reared, a complete feed must be provided, as na- tural feeds will be limited or absent. Such feeds must be of a physical con- sistency that will allow them to be fed in the water without breaking down, but still be easily ingested and digested by the fish. Properly sized feeds are required for different sizes of fish because fish normally do not chew their food. The feed must be palatable to the fish so that it will be readily consumed and not left to dissipate into the water. Dust and fine particles that may occur in the large-sized feeds will create problems because they are not efficiently consumed and, if present in excess, cause water pollution and gill disease. Feed Manufacturing Formulated feeds are manufactured in the forms of meals, granules, compressed pellets (sinking), expanded pellets (floating), and semimoist pellets. The use of dry pelleted feeds provides several advantages over oth- er feeding programs. Such feeds are available at all times of the year in any quantity. Fish producers can select the size of feed satisfactory for feeding fish through the rearing cycle. Pelleted feeds give lower feed conversions and lower feed cost per unit of weight gain than natural or wet feeds and cause less waste and contamination of the rearing water. No hatchery labor is required to prepare the feed. Pelleted feeds purchased in bulk provide additional efficiency in lower costs of handling and storage. The conven- ience of using automatic feeding equipment is also possible with bulk feeds. Compressed or sinking pellets are made by adding steam to the feed as it goes into the pellet mill. The steam increases the moisture content by 5 to 6% and raises the temperature to 150-I80°F during processing. The mix- ture is forced through a die to extrude a compressed, dense pellet. The pel- lets are air- dried and cooled immediately after pelleting. The moisture con- tent of pellets must be sufficiently low (less than 10%) to prevent mold growth during storage. NUTRITION AND FEEDING 235 The manufacture of expanded or floating pellets requires higher tem- peratures and pressures. Under these conditions, raw starch is quickly gela- tinized. Bonds are formed within the gelatinized starch to give a durable, water-stable pellet. The sudden release of pressure following extrusion al- lows water vapor to expand and the ensuing entrapment of gas creates a buoyant food particle. The additional cost of producing floating feeds must be carefully compared to the advantages of using a floating feed. Many catfish producers prefer the floating feeds because they can observe the fish feeding. This aids in pond management and reduces feed wastage due to overfeeding and loss of pellets that sink into the bottom muds. Recent studies with catfish have shown that feeding 15°<) of the ration as floating feed and 85% as sinking feed gives better feed utilization and is more economical than feeding either alone. Although the extrusion of feeds may result in the destruction of certain vitamins, amino acids, and fats, the lost materials can be replaced by spray- coating the pellets before packaging. Color may also be added at this time. A moist, pelleted fish feed containing 30-35% water can be made with special ingredients and equipment. No heat is required in pelleting moist feeds. Mold inhibitors, hygroscopic chemicals, or refrigeration must be used to protect moist feeds against spoilage. After extrusion the pellets are quick- frozen and stored at — 14°F. If properly handled, the pellets will remain separate without lumping. Moist pelleted feed spoils rapidly when thawed and a major loss of vitamins will result within a few hours. Moist feeds cost more to manufacture, ship, and store than dry pelleted feeds because they must be kept frozen. But they are beneficial in feeding fish that do not accept dry formulated feeds. Fingerlings of some species prefer the soft moist feeds because they are similar in texture to natural feeds. Moist feeds have been used successfully as an intermediate stage in converting fish from natural food to dry formula feeds. Salmon producers are the major users of moist feeds. The Oregon moist pellet can be obtained at a competitive price from several commercial feed companies in the northwest. Open- and Closed-Formulated Feeds There are open and closed formula feeds. An open- formula feed is one for which the complete formula is disclosed. Generally, such feeds have been developed by state or federal agencies or universities. An open- formula feed has the following advantages. (l) The producer knows exactly what is in the feed, including the level of vitamin supplementation. 23fi FISH HATCHF.RY MANAGEMENT (2) Because the same formulation and quality of ingredients are used, the feed will be consistent from one production season to the next. (3) Competitive bidding is possible for the specified feed. (4) The feed can be monitored through a quality-control program. In using open- formula feeds, however, the buyer assumes full responsi- bility for feed performance because the manufacturer has followed contract- ed instructions. This requires the buyer to have concise manufacturing and formula specifications, which must be updated periodically. Formula specif- ications for various diets are presented in Appendix F. A closed-formula feed is one in which the feed formulation is not dis- closed to the buyer. These feeds are sold by private manufacturers and are also referred to as "brand name" or proprietary feeds. The advantages of these feeds follow. (1) The manufacturer is responsible for the formulation. (2) The feed is generally a shelf item available at any time. (3) The diet may be lower in cost due to large-quantity production and the option of ingredient substitution. (4) The manufacturer is liable for problems of poor production related to the diet. However, the buyer has no control of the feed quality and the content of the feed largely is unknown. There may be unexpected variations between batches of feed due to ingredient substitutions or formulation changes. Handling and Storing Procedures Formulated fish feeds contain high levels of protein and oil with little fiber. These feeds are soft, fragile, and prone to rapid deterioration, especially if optimum handling and storage are not provided. Normally, the feeds are packaged in multiwalled paper bags to protect the flavor, aroma, and color. The bags also reduce exposure to air, mois- ture, and contamination. Plastic liners are used in bags for feeds containing oil levels over 12% to eliminate oil seepage through the paper bags and to retard moisture uptake. Many fish producers receive their feed in bulk, storing it in large bulk bins (Figure 74). Whether feed is in bags or bulk, proper handling and storage procedures must be followed to protect the quality of the feed. Be- cause fish feeds are very fragile in comparison to feeds for other animals, up to 3% fines can be expected from normal handling. Excess fines are the result of rough handling or poor physical characteristics of the feed. Do not NUTRITION AND FEEDING 237 t ^ Figure 74. Bulk storage of pelleted fish feeds. Dust and "fines" are screened out and collected (arrow), and can be repelleted. This type of storage is preferred to bins that require angering the feed up into a truck, because angering breaks up the pellets. (FWS photo.) throw, walk on, or stand on bagged feed. A motorized belt- type bag con- veyor causes the least damage to bagged feed. Close- spaced roller gravity conveyers work well, but the wide-spaced rollers or wheel rollers used for boxes are not suitable for bags and cause breakage of the granules and pel- lets. For handling bulk feed, a bucket elevator is preferred, followed by air lift systems; screw- type augers are least satisfactory. If proper storage conditions are not maintained, fish feed will spoil ra- pidly. During storage several factors can cause deterioration of the feed: 238 FISH HATCHF.RY MANAGEMENT physical conditions (moisture, heat, light); oxidation; micro-organisms (molds, bacteria, yeast); and enzymatic action. Feed in bags or bulk should be stored in a cool, dry area. Low humidity must be maintained because moisture enhances mold growth and attracts insects. Molds, which grow when the moisture is 13% or above, cause feed spoilage and may produce toxins. High temperatures may cause rancidity of oils and deterioration of vitamins. Rancid oils can be toxic, may destroy other nutrients, will cause off- flavor of the feed, and will produce an un- desirable flavor in fish eating the feed. The storage area should be kept clean and adequately ventilated. The stored feed should be protected from rodents, insects, and contamination. Ideal conditions for storing bagged dry feed include stacking the bags not over ten high on pallets so the bags are 3 to 4 inches off the floor. Space should be provided between the stacks for air circulation and rodent control. Low relative humidity and low temperature in the storage area reduce the rate of deterioration in feeds. The recommended maximum storage time for dry pelleted feeds is 90-100 days. If less than optimal storage conditions exist, the storage time should be shortened. Bulk feed should be stored in clean bins free of contaminants or spoiled feed. The bins must be in good condition to protect the feed from water and weather elements. Bins located in shaded areas remain cooler. Bins can be fitted with a screening unit on the discharge to remove dust and fines from the pellets. In many cases the fines can be returned to the feed mill for repelleting or be used to fertilize ponds. Moist pellets should be stored in the freezer at temperatures below 0°F until they are to be fed, then thawed just prior to feeding. Feed Evaluation The performance of feeds often is measured to evaluate or compare them. The measurements used to evaluate feeds at production hatcheries are: (l) fish growth (weight and length); (2) feed conversion; (3) cost to rear a pound of fish; (4) protein and calories required to rear a pound of fish; and (5) mortality and dietary deficiency symptoms. Feeding Feeding once was considered a simple task and was usually assigned to the least experienced fish culturist. The chore consisted of merely feeding all NUTRITION AND FEEDING 239 that the fish would consume, and then giving a little more to assure an abundant supply. Even though given more feed than necessary, the fish often were underfed because much of the feed was lost as it dispersed in the water. Nutrition is not solely a matter of feed composition. While it is true that fish cannot grow if essential elements are lacking in the feed, it is equally true that a feed cannot efficiently produce fish unless it can be consumed. The conversion of food into fish flesh is the measure that commonly is used to judge the efficiency of a feeding program in a hatchery. If the conver- sion factor is to be regarded as a measure of efficiency, what can be done to insure good food conversions? The most common errors in hatcheries are either to overfeed or to un- derfeed. Overfeeding is wasteful in terms of unconsumed food, but underfeeding is just as wasteful in terms of lost production. To obtain max- imum production and feed efficiency during a growing season, careful at- tention must be given, on a daily basis, to the amount of food the fish are receiving. The quantity of food required is expressed conveniently in terms of per- cent body weight per day. Because the metabolic rate per unit weight of fish decreases as the fish grow larger, the percent of body weight to be fed per day also decreases. Feeding Guides for Salmonids There are several methods for estimating feeding rates. Although differing in complexity, all produce efficient results if properly used. Table 25 may be used to estimate the amount of dry pelleted feed need- ed for rainbow trout. For a given fish size, the amount of food increases with increasing water temperature; for a given water temperature the amount of feed decreases with increasing fish size. Table 26 was developed by Oregon Fish and Wildlife Department for es- timating the amount of moist feed to give to coldwater species. A higher percent of body weight must be fed than in the case of dry pellets because of the greater water content in moist feed. Feeding tables provide a guide for determining the amount of feed to give salmonids. In general, these yield good results. However, there are si- tuations in which the amounts should be increased or reduced. When the water begins to warm in the spring, the fish indicate an accelerated meta- bolism by their increased activity and by the vigor with which they feed. At this time of the year, when the photoperiod also is increasing, it is pos- sible to feed in excess of (up to twice) the amounts in the tables and obtain 240 FISH HATCH F.RV MANAGEMENT Table 25. recommended amounts of dry feed for rainbow trout per day, OF different temperatures (or pounds feed per 100 POUNDS of fish), in 1976.) NUMBER OE FISH PER PUl Nl) 2,542- 304- 88.3- 37.8- WATER 2,542 + 304 88.3 37.8 19.7 TEMPERATURE (°F) APPRO.XIMATE SIZE IN INCHES UNDER 1 1-2 2-3 3-4 4-5 36 2.7 2.2 1.7 1.3 1.0 37 2.7 2.3 1.8 1.4 1.1 38 2.9 2.4 2.0 1.5 1.2 39 3.0 2.5 2.2 1.7 1.3 40 3.2 2.6 2.2 1.7 1.3 41 3.3 2.8 2.2 1.8 1.4 42 3.5 2.8 2.4 1.8 1.4 43 3.6 3.0 2.5 1.9 1.4 44 3.8 3.1 2.5 2.0 1.5 45 4.0 3.3 2.7 2.1 1.6 46 4.1 3.4 2.8 2.2 1.7 47 4.3 3.6 3.0 2.3 1.7 48 4.5 3.8 3.0 2.4 1.8 49 4.7 3.9 3.2 2.5 1.9 50 5.2 4.3 3.4 2.7 2.0 51 5.4 4.5 3.5 2.8 2.1 52 5.4 4.5 3.6 2.8 2.1 53 5.6 4.7 3.8 2.9 2.2 54 5.8 4.9 3.9 3.0 2.3 55 6.1 5.1 4.2 3.2 2.4 56 6.3 5.3 4.3 3.3 2.5 57 6.7 5.5 4.5 3.5 2.6 58 7.0 5.8 4.8 3.6 2.7 59 7.3 6.0 5.0 3.7 2.8 60 7.5 6.3 5.1 3.9 3.0 61 7.8 6.5 5.3 4.1 3.1 62 8.1 6.7 5.5 4.3 3.2 63 8.4 7.0 5.7 4.5 3.4 64 8.7 7.2 5.9 4.7 3.5 65 9.0 7.5 6.1 4.9 3.6 66 9.3 7.8 6.3 5.1 3.8 67 9.6 9.1 6.6 5.3 3.9 68 9.9 9.4 6.9 5.5 4.0 NUTRITION AND FP:F.DING 241 GIVEN AS PERCENT BODY WEIGHT. FOR DIFFERENT SIZE GROUPS HELD IN WATER RELATION TO FISH SIZE AND WATER TEMPERATURE. (SOURCE: LEITRITZ AND LEWIS NUMBER OK FISH PER POUND 19.7- 11.6- 7.35- 4.94- 3.47- Under 11.6 7.35 4.94 3.47 2.53 2.53 WATER TEMPERATURE APPRO.XIMATE SIZE IN INCHES (°F) 5-6 6-7 7-8 8-9 9-10 10 + 0.8 0.7 0.6 0.5 0.5 0.4 36 0.9 0.7 0.6 0.5 0.5 0.4 37 0.9 0.8 0.7 0.6 0.5 0.5 38 0.9 0.8 0.7 0.6 0.6 0.5 39 1.0 0.9 0.8 0.7 0.6 0.5 40 1.1 0.9 0.8 0.7 0.6 0.5 41 1.2 0.9 0.8 0.7 0.6 0.5 42 1.2 1.0 0.9 0.8 0.7 0.6 43 1.3 I.O 0.9 0.8 0.8 0.6 44 1.3 1.1 1.0 0.9 0.8 0.7 45 1.4 1.2 1.0 0.9 0.8 0.7 46 1.4 1.2 1.0 0.9 0.8 0.7 47 1.5 1.3 1.1 1.0 0.9 0.8 48 1.5 1.3 1.1 1.0 0.9 0.8 49 1.7 1.4 1.2 1.1 1.0 0.9 50 1.7 1.5 1.3 1.1 1.0 0.9 51 1.7 1.5 1.3 1.1 1.0 0.9 52 1.8 1.5 1.3 1.1 1.1 1.0 53 1.9 1.6 1.4 1.3 1.1 1.0 54 2.0 1.6 1.4 1.3 1.1 1.0 55 2.0 1.7 1.5 1.3 1.2 1.0 56 2.1 1.8 1.5 1.4 1.2 1.1 57 2.2 1.9 1.6 1.4 1.3 1.2 58 2.3 1.9 1.7 1.5 1.3 1.2 59 2.4 2.0 1.7 1.5 1.4 1.3 60 2.5 2.0 1.8 1.6 1.4 1.3 61 2.6 2.1 1.8 1.6 1.5 1.4 62 2.7 2.1 1.9 1.7 1.5 1.4 63 2.8 2.2 1.9 1.7 1.6 1.5 64 2.9 2.2 2.0 1.8 1.6 1.5 65 3.0 2.3 2.0 1.8 1.6 1.6 66 3.1 2.4 2.1 1.9 1.7 1.6 67 3.2 2.5 2.1 2.0 1.8 1.7 68 242 KISH llAICHKRY MANAGEMENT Table 26. recommended amounts of oregon moist pellet feed for sal- weight PER DAY (pounds FEED PER 100 POUNDS OF FISH), RELATED TO FISH SIZE unpublished.) NUMBER OF FISH PER POUND WATER TEMPERATURE START- 600- 420- 305- 230- 180- 140- 115- (Fi 600 420 305 230 180 140 115 ilO 40 3.2 2.9 2.6 2.3 2.0 1.9 1.8 1.6 41 3.5 3.2 2.8 2.5 2.2 2.1 2.0 1.8 42 3.9 3.5 3.0 2.7 2.4 2.3 2.2 2.0 43 4.3 3.8 3.2 2.9 2.6 2.5 2.4 2.2 44 4.7 4.1 3.5 3.1 2.8 2.7 2.6 2.4 45 5.1 4.4 3.8 3.4 3.1 2.9 2.8 2.6 46 5.5 4.8 4.2 3.8 3.4 3.2 3.0 2.9 47 6.0 5.2 4.6 4.1 3.7 3.5 3.3 3.1 48 6.4 5.6 5.0 4.5 4.0 3.8 3.5 3.4 49 6.9 6.0 5.4 4.8 4.4 4.1 3.8 3.6 50 7.3 6.4 5.8 5.2 4.7 4.4 4.1 3.8 51 7.7 6.7 6.1 5.5 5.0 4.7 4.3 4.0 52 8.0 7.0 6.4 5.8 5.2 4.9 4.5 4.1 53 8.3 7.3 6.6 6.0 5.4 5.0 4.7 4.3 54 8.6 7.6 6.8 6.2 5.6 5.2 4.8 4.4 55 8.9 7.9 7.0 6.4 5.8 5.3 5.0 4.6 56 9.3 8.2 7.3 6.7 6.1 5.5 5.2 4.8 57 9.6 8.5 7.6 6.9 6.3 5.7 5.4 5.0 58 9.9 8.8 7.8 7.1 6.5 5.9 5.6 5.2 59 10.2 9.1 8.1 7.3 6.7 6.1 5.8 5.4 60 10.5 9.3 8.3 7.5 6.9 6,3 5.9 5.5 excellent conversions and weight gains by the fish. Taking advantage of such situations increases the efficiency and production of a hatchery. By the same reasoning, as the temperature starts to fall, metabolism is depressed and less food than the amounts listed in the tables still will result in maximum efficiency of food conversion. As mentioned in Chapter 2, salmonids increase their length at a constant rate during their first 1^ years or so of life, so long as they are raised at a constant temperature (see page 6l). The rate of length increase (inches per day or month), of course, varies with temperature. For a given temperature, the amount of daily feed needed can be calculated from knowledge of fish growth and conversion at that temperature from the following formula: , , , ., Conversion x 3 x A Z, x IQQ rercent body weight to feed daily = NUTRITION AND FEEDING 243 MONIDS (BASED ON COHO SALMON) FED TWICE EACH DAY. GIVEN AS PERCENT BODY AND WATER TEMPERATURE. (SOURCE; OREGON FISH AND WILDLIFE DEPARTMENT, NUMBER OF FISH PER POUND WATER 90- 75- 65- 55- 45- 39- 34- 29- TEMPERATURE 75 65 55 45 39 34 29 25.5 (°F) 1.5 1.3 1.2 1.1 1.0 1.0 0.9 0.9 40 1.7 1.5 1.4 1.3 1.2 1.1 I.O 0.9 41 1.9 1.7 1.6 1.4 1.3 1.2 I.l 1.0 42 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2 43 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 44 2.5 2.3 2.2 2.0 1.9 1.8 1.7 1.6 45 2.7 2.5 2.3 2.2 2.1 2.0 1 .9 1.8 46 2.9 2.7 2.5 2.4 2.3 2.1 2.0 1.9 47 3.1 2.8 2.7 2.5 2.4 2.3 2.2 2.1 48 3.3 3.0 2.8 2.7 2.6 2.5 2.3 2.2 49 3.5 3.2 3.0 2.9 2.8 2.7 2.5 2.4 50 3.7 3.3 3.2 3.0 2.9 2.8 2.7 2.6 51 3.8 3.5 3.3 3.2 3.1 3.0 2.8 2.7 52 4.0 3.6 3.5 3.4 3.2 3.1 2.9 2.8 53 4.1 3.8 3.6 3.5 3.4 3.2 3.1 3.0 54 4.3 3.9 3.8 3.7 3.5 3.4 3.2 3.1 55 4.4 4.1 3.9 3.8 3.6 3.5 3.4 3.2 56 4.6 4.2 4.1 3.9 3.7 3.6 3.5 3.3 57 4.8 4.4 4.2 4.1 3.9 3.8 3.6 3.4 58 5.0 4.5 4.4 4.2 4.0 3.9 3.7 3.5 59 5.1 4.7 4.5 4.3 4.1 4.0 3.8 3.6 60 Here, A/, equals the daily increase in length in inches, and L equals the length in inches at the present time. To use this equation, an average monthly growth in inches is established from previous years' records for the same temperature. The daily increase in length is determined by dividing the average monthly growth by the number of days in the month. The daily growth then can be used to pro- ject fish size to any date needed. An expected feed conversion is obtained from previous hatchery records or calculated from the caloric content of the feed (see page 225). For example, on April 13, we have 210,000 fish on hand. Their feeding rate was last established on April I, when fish were 20 pounds per 1,000 fish, or 3.68 inches. We need to adjust the feeding rate again, knowing from past records that at this temperature the average length increase per 244 FISH hatchp:ry management Table 26. continued. NUMBER OF FISH PER POUND WATER 11.0 TEMPERATURE 25.5- 22.5- 20.0- 18.0- 16.0- 14.0- 13.0- 12.0- AND ("F) 22.5 20.0 18.0 16.0 14.0 13.0 12.0 11.0 FEWER 40 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 41 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 42 1.0 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 43 1.1 1.1 0.9 0.9 0.8 0.7 0.7 0.6 0.6 44 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.7 0.6 45 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.8 46 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 47 1.8 1.7 1.6 1.5 1.3 1.2 1.1 1.0 0.9 48 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.1 1.0 49 2.1 2.0 1.9 1.8 1.6 1.5 1.4 1.3 1.1 50 2.3 2.1 2.0 1.9 1.8 1.7 1.5 1.4 1.3 51 2.4 2.3 2.2 2.0 1.9 1.8 1.6 1.5 1.4 52 2.6 2.4 2.3 2.2 2.0 1.9 1.7 1.6 1.5 53 2.7 2.6 2.4 2.3 2.1 2.0 1.8 1.7 1.6 54 2.8 2.7 2.5 2.4 2.2 2.1 1.9 1.8 1.7 55 2.9 2.8 2.6 2.5 2.3 2.2 2.0 1.9 1.8 56 3.1 2.9 2.8 2.6 2.4 2.3 2.1 2.0 1.9 57 3.2 3.0 2.9 2.7 2.5 2.4 2.2 2.1 2.0 58 3.3 3.1 3.0 2.8 2.6 2.5 2.3 2.2 2.1 59 3.4 3.2 3.1 2.9 2.7 2.6 2.4 2.3 2.2 60 3.5 3.3 3.2 3.0 2.8 2.7 2.5 2.4 2.3 day (AL) is 0.019 inches per day during April, and expected feed conver- sion is 1.2 pounds of feed per pound of growth. What is our new feeding rate? Length, April 1st Growth, 13 days x 0.019 Length, April 13th 210,000 fish X 24.3 pounds/1,000 3x 1.2 X 0.019 X 100 % to feed daily 0.017X5,103 pounds 3.93 3.68 inches (20 pounds/1,000) 0.25 3.93 inches (24.3 pounds/1,000) 5,103 pounds of fish, April 13th 1.7% (0.017) 87 pounds of feed required daily, April 13th, for 210,000 fish. NUTRITION AND FEEDING 245 The proper use of this method helps assure optimum feeding levels. It determines the feeding level regardless of the caloric content of the feed, because this is considered in the feed conversion. When the water temperature, diet, and species remain constant, all numerator factors in the feeding formula remain constant. Multiplication of the numerator factors establishes a Hatchery Constant (HC): HC = 3x conversion x AI x 100. The percent of body weight to feed daily for any length of fish can be ob- tained by dividing the Hatchery Constant by the length of fish {L) in inches. FfC Percent of body weight feed daily = The Hatchery Constant {HC) is used in the following example to calculate feed requirements. We must calculate the amount of feed required on April 10th for 20,000 fish averaging 100 pounds per 1,000 fish or 6.3 inches on April 1st. The expected growth during April is 0.60 inches and the feed conversion is 1.2 pounds of feed per pound of growth. Length increase per day (AZ-) = 0.60 inches Length, April 1st = 6.30 inches (lOO pounds/1,000 fish) Growth, 10 days X 0.020 = 0.20 Length, April 10th = 6.50 inches (llO pounds/1,000 fish) 20,000 fish X 110 pounds/1,000 = 2,200 pounds offish April 10th //C= 3 X 1.2X0.020 X 100 =7.2 HC 7 2 Percent body weight to feed = = — ' — = 1.1% (O.Oll) L 6.50 2,200 pounds fish x 0.011 = 24.2 pounds of feed required on April 10th for the 20,000 fish. The above method of calculating feed can be used to project the amount of feed required for a raceway or pond for any period of time. Many sta- tions use this method to set up feeding programs for the coming month. 246 FISH HATCHF.RY MANAGEMENT A simplified method to calculate the amount of daily feed is based on monthly percent gain in fish weight. In conjunction with past records that establish both growth in inches and conversion, Table 27 can be used to project daily feed requirements on a monthly basis. To calculate the amount of feed required for a one month period two values must be deter- mined: (l) the gain in weight for the month; and (2) the percent gain for the month. (1) Gain in weight = weight of lot on hand at the end of the month minus the weight of lot on hand the start of the month. .s „ monthly gain in weight x 100 (2) Percent gain = f-^ ^ ; weight at start of month The feed requirement during the month of July for 100,000 fish averag- ing 100 pounds per 1,000 fish, or 6.30 inches, on July 1st can be calculated in the following manner. The expected growth for the month of July is 0.60 inches and the feed conversion is 1.3 pounds of feed per pound of growth. Length, July 1st 6.30 inches (lOO pounds/1,000 fish) Expected growth, July 0.60 Length, July 31st 6.90 inches (132 pounds/1,000 fish) 100,000 fish X 100 pounds/1,000 = 10,000 pounds July 1st 100,000 fish X 132 pounds/1,000 = 13,200 pounds July 31st Expected gain in fish weight, July = 3,200 pounds The expected gain in fish weight, multiplied by the food conversion determines the required pounds of feed for the month. Pounds of feed required for July = 3,200 pounds gain x 1.3 conversion = 4,160 pounds „ 3,200 pounds gain „„„, Percent gain= ■ ^ , ^ , ^ , = 32% 10,000 pounds on hand July 1 Table 27 shows that at the 30% rate of gain, fish should be fed 2.91% of the monthly feed total per day during the first 8 days; 3.13% during the second 8 days; 3.34% during the third 8 days; and 3.57% per day the remaining days of the month. NUTRITION AND FEEDING 247 Table 27. percent of total monthly feed to give trout daily for dif- ferent PERCENT GAINS, IF FEED IS TO BE ADJUSTED FOUR TIMES PER MONTH. (SOURCE: FREEMAN ET AL. 1967.) EXPECTED DAYS MDNTHI Y ivi yj 1^ 1 ri Li I PERCENT WEIGHT 1-8 9-16 17-24 25-31 GAIN (8 DAYS) (8 DAYS) (8 DAYS) (7 DAYS) 10 3.13 3.13 3.25 3.29 20 3.00 3.19 3.31 3.43 30 2.91 3.13 3.34 3.57 40 2.85 3.09 3.38 3.64 50 2.75 3.08 3.40 3.74 60 2.69 3.04 3.36 3.90 70 2.63 3.00 3.45 3.90 80 2..56 2.96 3.48 4.00 90 2.50 2.96 3.49 4.06 100 2.45 2.93 3.50 4.14 110 2.40 2.91 3.51 4.20 120 2.35 2.88 3.53 4.29 130 2.31 2.85 3.55 4.33 140 2.26 2.84 3.56 4.39 150 2.23 2.81 3.59 4.56 160 2.19 2.80 3.58 4.50 170 2.15 2.78 3.59 4.56 180 2.11 2.75 3.60 4.61 190 2.08 2.74 3.61 4.66 200 2.05 2.71 3.63 4.70 210 2.01 2.70 3.63 4.76 220 1.99 2.69 3.63 4.80 230 1.96 2.68 3.63 4.84 240 1.93 2.66 3.64 4.89 250 1.91 2.63 3.65 4.93 260 1.89 2.63 3.65 4.96 270 1.86 2.61 3.65 5.00 280 1.84 2.60 3.65 5.04 290 1.81 2.58 3.66 5.09 300 1.79 2.56 3.68 5.12 248 FISH HATCHERY MANAGEMENT The amounts to feed would be: July 1-8; 2.91% X 4,160= 121 pounds/day July 9-16; 3.13% x 4,160= 130 pounds/day July 17-24; 3.34% x 4,160 = 139 pounds/day July 25-31; 3.57% x 4,160= 149 pounds/day Under normal conditions, adjusting feeding levels four times during the month should prevent over- or under- feeding. The advantage of this method is its simplicity. Feeding Guides for Coolwater Fishes For many years, fish culture was classified into two major groups. "Coldwa- ter" hatcheries cultured trout and salmon, and "warmwater" hatcheries cul- tured any fish not a salmonid. Muskellunge, northern pike, walleye, and yellow perch prefer temperatures warmer than those suited for trout, but colder than those water temperatures most favorable for bass and catfish. The term "coolwater species" has gained general acceptance in referring to this intermediate group. Pond culture traditionally has been used to rear coolwater species. This method of extensive culture involves providing sufficient quantities of micro-organisms and plankton as natural foods through pond fertilization programs. If larger fingerlings are to be reared the fry are transferred, when they reach approximately 1.5 inches in length, to growing ponds where minnows are provided for food. A major problem in extensive pond culture is that the fish culturist is unable to control the food supply, diseases, or other factors. Many times it is extremely difficult to determine the health and growth of fish in a pond. In recent years the intensive culture of coolwater fishes in tanks has been successful. Zooplankton, primarily Daphnia, are cultured in ponds and each day a supply is placed in the rearing tanks. Fish reared in tanks can be observed readily and treated for parasites. Fish also can be graded to size to minimize cannibalism and to provide an accurate inventory. Pennsylvania fisheries workers successfully fed a diet of lOO'Si Daphnia to muskellunge for up to 5 months with no significant mortality, but after the fish attained a length of approximately 2 inches the Daphnia diet did not appear adequate. Fisheries workers in Pennsylvania and Michigan have reared coolwater fishes successfully on dry feed. The W-7 dry feed formulated by the Unit- ed States Fish and Wildlife Service specifically for coolwater fishes has given the best results. (See Appendix F for diet formulation.) Starter feed NUTRITION AND FEEDING 249 is distributed in the trough by automatic feeders set to feed at 5-minute in- tervals from dawn to dusk (Figures 75 and 76). Coolwater fish will not pick food pellets off the bottom of the tank so it is necessary to continually present small amounts of feed with an automatic feeder. In some situations, coolwater fry are started on brine shrimp and then converted to dry feed. Pennsylvania workers report that muskellunge are extremely difficult to rear on artificial feeds. However, the tiger muskie (northern pike male x muskellunge females) adapts readily to dry feeds. Northern pike will accept a dry feed and also adapt to culture in tanks. Walleye fry have been observed feeding on the W-7 diet, but did not survive well on it. Anemia developed in advanced fingerlings, indicating a deficiency of some nutrient. Tiger muskie fry aggressively feed on dry feeds. Fry often follow a food particle through the entire water column before striking it. Hand-feeding or human presence at the trough does not disrupt feeding activity. How- ever, when the fish attain a length of 5-6 inches, human presence next to a trough or tank can disrupt feeding activity completely. Cannibalism gen- erally is a problem only during the first 10-12 days after initial feeding, when the fish are less than 2-3 inches in length. The removal of weak and dying fry greatly reduces cannibalism. The methods developed for estimating feeding rates for salmonids can be adapted for use with coolwater species. Michigan workers use a Hatchery Constant of 40 to calculate feeding rates for tiger muskellunge raised in 70°F water. Feeding Guides for Warmwater Fishes CATFISH Newly hatched catfish fry live on nutrients from the yolk sac for 3-10 days, depending upon water temperatures, after which they accept food from a variety of sources. Generally, feed for trough- feeding of fry should be small in particle size, high in animal protein, and high in fat. Salmonid rations are well suited for this purpose. Palatability of lower-quality feed is enhanced by having a high percentage of fish meal, fish oil, chopped liver, egg yolk, or other ingredients that serve as attractants. Overfeeding in the troughs should be avoided and adequate water flows must be maintained to avoid fouling the water. The fry should be transferred to ponds with high zooplankton densities as soon as possible to efficiently utilize the natural food source. Supplemental feeding of fry in ponds should begin soon after stocking. A 250 FISH HATCHERY MANAGEMENT Figure 75. In recent years, intensive culture of coolwater fishes in tanks has been successful. The tanks are covered partially with black plastic to avoid dis- turbing the fish. Automatic feeders provide a continuous supply of dry feed from dawn to dusk at 5-minute intervals. (Courtesy Pennsylvania Fish Commission.) Figure 76. Walleye fingerlings are reared successfully in tanks, with automatic feeders to dispense dry feed. The fish first are started feeding on live brine shrimp or zooplankton and then are converted to dry feed. (Courtesy Pennsyl- vania Fish Commission.) NUTRITION AND FEEDING 251 high-quality, 36"o protein catfish feed (Appendix F) is an adequate supple- mental feed for fry and small fingerlings as they will get a large portion of their nutrients from natural pond organisms. Feed first should be pelleted or extruded before it is reduced to smaller particle sizes. Fat sprayed onto the feed after processing reduces the loss of water-soluble vitamins. Growth of channel catfish fingerlings is similar with either sinking or floating pellets, provided that the nutrient contents are the same. Floating feeds are a valuable management tool to help determine the effects of low dissolved oxygen content and low or high water temperature on feeding, general vigor, and health of fish during the feeding season. It also is help- ful in determining amounts of feed to give fish in special culture systems such as cage feeding, raceway feeding, and ponds having abundant rooted vegetation. Table 28 presents a feeding guide for channel catfish in ponds, and Table 29 offers one for catfish in raceways. The pond feed is a supplemen- tal, 36"o protein diet; that for raceways is a complete formulation. See Ap- pendix F for ingredients. Low dissolved oxygen levels depress feeding activity of catfish, and fish should not be fed in early morning for this reason. Neither should they be fed late in the day because their increased metabolic oxygen requirement during active feeding and digestion will coincide with the period of low dissolved oxygen in the pond during the night and early morning. The best times to feed are between mid- morning and mid- afternoon. The optimal temperature for catfish growth is approximately 85°F; as temperature decreases, food consumption decreases proportionally. Gen- erally, catfish do not feed consistently in ponds when the water tempera- ture drops below 60°F; below 50°F they will feed, but at greatly reduced levels and frequencies. Below 60°F, the efficiency of digestion and metabo- lism drops markedly. During colder months, feed catfish only on warm days and only what the fish will consume readily. A recommended guide for winter feeding of cat- fish in ponds is to feed the fish 0.75-1% of their estimated weight daily only when the water temperature is above 54°F, and not to feed at lower temperatures. There are no reliable data on the best feeds for catfish in the winter. Catfish do not respond as well to high- protein diets in cool weather as in warm weather. This may indicate that lower- protein feeds (below 32%) are more economical in cold water. Digestibility of carbohydrates is suppressed even more at low temperatures than the digestibility of proteins and fats, indicating that high-grain feeds are not utilized by catfish in cool weather. Therefore, winter rations should contain less protein and carbohydrates than those fed during the summer. WATER FISH PERCENT BODY TEMPERATURE SIZE WEIGHT TO FEED (T) (POUNDS) DAILY ()8 0.04 2.0 72 0.06 2.5 78 0.11 2.8 80 0.16 3.0 83 0.21 3.0 84 0.28 3.0 85 0.35 2.8 85 0.42 2.5 86 0.60 2.2 86 0.75 1.8 83 0.89 1.6 79 1.01 1.4 73 1.10 1.1 252 fish hatchery management Table 28. typical spring-summerfall supplemental feeding schedule for channel catfish in ponds, based on stocking rates of 2,000-3,000 fish per acre.'' (SOURCE: STICKNEY AND LOVELL 1977.) DATE April 15 April 30 May 15 May 30 June 15 June 30 July 15 July 30 August 15 August 30 September 15 September 30 October 15 The feed allowances are based on rations containing 36"ii protein and approximately 2.88 kcalories of digestible energy per gram of protein. If feeds of lower protein and energy con- centrations are used, daily allowances should be increased proportionally. Fish are fed 6 days per week. LARGEMOUTH AND SMALLMOUTH BASS As long ago as 1924, fish culturists attempted to increase yield and survival of smallmouth bass by providing a supplemental feed of zooplankton. Ground fresh- fish flesh also was successfully used but costs were prohibi- tive. These early attempts were discouraging but culturists have continued to rear bass fry to fingerling size on naturally occurring foods in fertilized Table 29. feeding rates (percent body weight fed per day) for channel CATFISH fed a COMPLETE FEED (25% FLOATING, 75% SINKING FEED) IN RACEWAYS. (SOURCE: KRAMER, CHIN AND MAYO 1976.) SIZE (INCHES) 1-2 2-5 5-1- WEIGHT (POUNDS) WATER TEMPERATURE 0.001-0.004 0.004-0.04 0.04 Below 55°F 1% 1% 1% At 55°F 3% 2% 1.5% Above 55T 5% 3% 2% NUTRITION AND FEEDING 253 earthen ponds. This method generally results in low yields and is unpredictable. Interest in supplemental feeding of bass has been renewed in recent years due to successful experimental use of formulated pelleted feeds with largemouth bass fingerlings. Attempts to train swim- up bass fry to feed exclusively on formulated feeds or ground fish flesh have been unsuccess- ful, despite the use of a variety of training techniques. The best success in supplemental feeding has been obtained by rearing bass fry on natural feed to an average length of 2 inches in earthen ponds before they are put on an intensive training program to accept formulated feed. A moist feed, such as the Oregon moist pellet, or a quality dry feed such as the W-7 coolwa- ter fish feed may be employed. The success of this program has been corre- lated with initial fingerling size, coupled with sound management practices. The following steps are suggested for an intensive feeding program with bass: By conventional techniques, rear bass fingerlings on natural feed in earthen ponds to an average total length of 2.0 inches. Harvest and move fish to raceways and tanks. Grade fish carefully to eliminate "cannibals," because uniformly sized fingerlings are needed. Stock the tanks at 0.15-0.4 pounds per cubic foot of water (3,000—7,500 fingerlings per tank). Treat the fish prophylactically with 4 parts per million acriflavine for 4 hours. Heavy parasite infestations may require treatment with formalin or a similar chemical. Provide ample aeration during treatment. Begin feeding a -j^-inch feed granule the following day. Feed at 1- to 2- hour intervals, five or more times daily. Feed slowly and carefully because bass will not pick up sunken food particles from the bottom of the tank. Automatic feeders are excellent for this purpose. If fish are reluctant to feed, supplement the granule with ground fresh or frozen fish. Clean tanks twice daily and remove all dead fish daily. Begin feeding a ^-inch granule as soon as the fingerlings are feeding well and able to ingest it. Perform grading as needed to reduce cannibalism. After 10-14 days, 65-75% of the fish should be on feed. Reports of 90-95% success are not unusual. The fish should double their weight dur- ing this 2-week period. At 2-3 weeks, remove all nonfeeders and move the fish to ponds or race- ways. Stock ponds at 10,000 per acre. Feed and maintain fish in a res- tricted area for 2-3 days, then release them to the remainder of the pond. Grow the bass to 4 inches on a ^-inch pellet. Table 30 presents a sug- gested feeding guide that can be used when formulated dry feeds are given to bass fingerlings in raceways or ponds. 254 fish hatciif.ry management Table 30. bass keeu chart: percent body weight fed per day in raceway CULTURE for FORMULATED DRY FEEDS.'^ (SOURCE: KRAMER, CHIN AND MAYO 197(i.) SIZE (INCHES) 1-2 2-3 3-4 4-5 5+ WEIGHT (POUNDS) WATER TEMPERATURE 0.002 0.002-.015 0.015-0.03 0.03-0.06 0.06 fi5°F 4.4'^ 4.0');, 3.2% 2.4% 1.6% 70°F 5.5'!i, 4.7% 2.5% 2.2"'(, 2.0'!{. 75°F 6.0% 5.0'^i, 4.0% s.o"-;. 2.0"/, .80°F 6.5% 5.4% 4.3% 3.3'!';, 2.2% 85°F 7.1% 5.9'},, 4.7% 3.5'!,, 2.4"/;, 90°F 7.5'!^, 6.3% 5.1% 3.9% 2.7% Feedings 4 4 2 1 1 per hour Winter feeding rate: l",, of body weight per day. STRIPED BASS Striped bass fingerlings often are fed supplemental diets in earthen ponds when zooplankton blooms have deteriorated or larger fish are desired. The fingerlings are fed a high- protein (40-50%) salmonid type of formulated feed at the rate of 5.0 pounds/acre per day. This is increased gradually to a maximum of 20.0 pounds/acre per day by the time of harvest. The fish are fed 2-6 times daily. When striped bass fingerlings reach a length of approximately 1.5 inches they will accept salmonid- type feeds readily. Good success can be antici- pated when a training program is followed, such as that described for largemouth and smallmouth bass. Striped bass fingerlings can be grown to advanced sizes in ponds, cages, or raceways. Attempts to rear swim-up fry to fingerling size on brine shrimp and for- mulated feeds under intensive cultural conditions have been relatively unsuccessful. Time of Initial Feeding There is considerable difference of opinion among fish culturists as to when fry should receive their initial feeding. The most common practice is to offer food when the fry swim up. Swim- up occurs when the fry have ab- sorbed enough of their yolk sac to enable them to rise from the bottom of NUTRITION AND FEEDING 255 the trough and maintain a position in the water column. A considerable amount of work has been conducted to determine when various salmonid fry first take food. Brown trout begin feeding food approximately 31 days after hatching in 52°F water, while food was first found in the stomachs of rainbow trout fry 21 days after hatching in 50°F water. The upper alimentary tract of rainbow trout fry remains closed by a tis- sue plug until several days before swim- up. Thus, feeding of rainbow trout fry before swim- up is useless. Some fish culturists have observed higher mortality in brook trout fed early than in those deprived of food for up to 5 days after swim-up. Yolk absorption is a useful visual guide to determine the initial feeding of most species of fish. Most studies reported in the literature (Table 3l) indicate that early feeding of fry during swim-up does not provide them with any advantage over fry that are fed later, after the yolk sac has been absorbed. Many culturists start feeding when 50% of the fry are swimming up because if fry are denied food much beyond yolk-sac absorption, some will refuse to feed. No doubt, starvation from a lack of food will lead to a weakened fry that cannot feed even when food is abundant. It is apparent that the initial feeding time for warmwater fishes is much more critical than for coldwater species because metabolic rates are much higher at warmer water temperatures. This will lead to more rapid yolk ab- sorption and a need for fish to be introduced to feed at an earlier date. Feeding Frequency The frequency at which fish should be fed is governed by the size of the fish and how rapidly they consume the feed. When fish are started on feed, it is desirable to give small amounts of small- sized particles at frequent in- tervals. Several factors influence how quickly fish consume feed. The type of feed, the way it is introduced, and the type of trough or pond in which it is fed all will affect the rate of consumption. Feeds that are heavier than water must be fed with more care than those that float. Once a sinking feed reaches the bottom many fish will ignore it. To avoid their prolonged exposure to water, sinking feeds should be fed slowly and at greater fre- quency. Trout and salmon generally are fed small amounts at hourly intervals throughout an 8- hour day when they first start to feed. Some fish culturists feed fry at half- hourly intervals and gradually reduce the number of feed- ings as the fish increase in length. The general practice has been to feed trout three times a day until they are 5 inches long (20/pound). Larger trout are fed twice daily and broodfish are usually fed once each day. 256 FISH HATCHERY MANAGEMENT Table 31. initial feeding times for various species of fish. INITIAL WATER FEEDING TEMPER- (DAYS post- ATURE SPECIES hatching) rF) Brook trout 23-35" 52 REMARKS Brown trout Cutthroat trout Rainbow trout Channel catfish Tiger muskie Northern pike, walleye, muskellunge 31 23 20-30" at swim-up at swim-up Several fry had food in gut on 23rd day; all fry were feeding on the 35th day. 52 Evidence of food in stomach on 27th day; all fry feeding on 31st day. 47-51 Evidence of food in stomach on 14th day; all fry feeding on 23rd day. 47 Evidence of food in stomach on 21st day (16 days at 50°F). — 5 to 10 days after hatching, depending on water tempera- ture. 68 Food presented at swim- up; most of yolk sac absorbed after 8 days. 50-70 Food presented at swim-up, up to 12 days post-hatching. Various reports include a range of initial feeding times and water temperatures. It is important to note that in some instances, evidence of food in the stomach did not occur until several days after swim- up. Table 32 presents feeding frequencies for trout and Pacific salmon finger- lings. Successful feeding of dry feeds to coolwater fishes, such as northern pike and tiger muskie, requires initial feeding of fry at 5- minute intervals, at 10-minute intervals when fry are 2 inches long, and at 15-minute intervals when they are 4 inches long, from automatic feeders during the daylight hours. A rule of thumb used by some fish culturists is to feed iJo of the body weight per feeding. Therefore, if the fish are being fed at a rate of 10% of nutrition and feeding 257 Table 32. suggested feeding frequencies for salmonids. (source; washing- ton DEPARTMENT OF FISHERIES, UNPUBLISHED.) FiSH SIZE (NUMBER/POUND) SPECIES 1,500 1,000 750 500 250 125 75 30 10-LARGER TIMES PER DAY Coho salmon 9 8 7 6 5 3 3 Fall chinook salmon 8 8 8 6 5 4 3 Trout 8 8 6 6 6 4 4 body weight, they would receive 10 feedings per day; if they receive T'o of body weight in feed per day it would be fed in one feeding. Channel catfish reared in raceways produce more gain when fed twice daily than when they are fed only once daily. In some situations, more than two feedings per day will not improve the feed consumption or growth rate in pond fed catfish. The following statements relate to feeding frequency: The feeding frequency does not significantly influence the mortality of fry once they pass the initial feeding stage. Frequently fed fingerlings utilize their feed more efficiently than those fed less frequently, resulting in better feed conversion. Frequent feeding of fingerlings reduces starvation and stunting of the small fish in a group. Generally, more frequent feeding results in greater uniformity in fish size. The accumulation of waste feed on the bottom of a rearing unit due to the infrequent feeding of large amounts of feed is a principal factor caus- ing inefficient utilization of feed. When uneaten feed lies on the bottom of the tank, water-soluble nu- trients are leached out, resulting in poor utilization of the feed. In general, the number of feedings per day should be greater for dry feed than for soft moist feeds. A rule of thumb is that 90% of the feed should be eaten in 15 minutes or less. Feed Sizes The size of feed particles is critical in the feeding of fish. If particles are too large, the fish will not be able to ingest them until the water disin- tegrates the feed to an acceptable size. When this occurs, nutrients leach out of the pellet, wasting feed and possibly polluting the water. When the 258 FISH HATCHERY MANAGEMENT Table 33. recommended sizes for dry formulated feeds given to trout. GRANULE OR PELLET size" FISH SIZE us WEIGHT NUMBER SCREEN PER PER SIZE THOUSAND POUND 30-40 less than 0.5 2,000+ 20-30 0.5-1.25 2,000-800 16-20 1.2.5-4.0 800-250 10-16 4.0-10.0 250-100 6-10 10.0-33.3 100-30 33.3-100.0 30-10 100.0+ 10 and fewer Starter granule No. 1 granule No. 2 granule No. 3 granule No. 4 granule — " pellets _L" 16 pellets '^Feed sizes — US Fish and Wildlife Service Trout Feed Contract Specifications, Spearfish Fisheries Center, Spearfish, South Dakota 57783. particles are too small, the feed dissolves in water and is lost. It is impor- tant for maximum feed efficiency to provide an acceptable range of feed sizes for fish during their different growth stages. Granules or crumbles are made in a range of sizes for fingerlings of dif- ferent weights (Tables 33-35). Hard pellets are cracked into granules and the different particle sizes are separated by screening. When the fish are being shifted from a small granule to a larger size, the change should be gradual rather than abrupt. The change may be made ei- ther by mixing the two sizes together and feeding them at the same time, or by feeding the two sizes separately, starting with a few feedings of the larger size each day and gradually increasing the frequency until only the larger particle is fed. Table 34. recommended sizes for abernathy dry pelleted feed given to PACIFIC salmon. (SOURCE: L.G. FOWLER, UNPUBLISHED.) GRANULE OR PELLET SIZE FISH SIZE (NUMBER PER POUND) Starter granule -!--inch granule - — inch granule ^-inch granule — inch granule —-inch pellet 32 ^ —-inch pellet —-inch pellet 16 ^ 800 + 800-500 500-200 200-100 100-75 75-.50 .50-20 Less than 20 NUTRITION AND FEEDING 259 Table 35. optimum feed particle sizes for small channel catfish, crum- bles OR pellets should be kept to the maximum size that the fish can ingest. (SOURCE; STICKNEY AND LOVELL 1977.) CRUMBLE OR PELLET SIZE FISH SIZE (INCHES) 00 Crumble (starter) No. 1 crumble No. 3 crumble ^-inch pellet Swim-up fry 0.5-1.5 1.5-2.5 2.5-6 Feeding Methods Automatic feeders with timing devices can be used to reduce labor costs and to provide fish with small quantities of feed at frequent intervals. Self- feeders or demand feeders are especially useful in feeding large channel catfish, particularly during winter months when the fish fed less actively. Automatic feeders have become quite popular for feeding salmonids and coolwater fishes. However, most pond- reared warmwater fishes are fed by hand. Mobile blower- type feeders often are used to feed warmwater fish in large ponds (Figure 77). One study determined that more frequent feeding with automatic feeders did not increase growth of channel catfish over those hand-fed twice per day. Because catfish have relatively large stomachs, they may consume enough food for maximum growth in two feedings. FIGURE 77. pond. Bulk- feeding of formulated pelleted feed to catfish in a large rearing 260 FISH HATCHERY MANAGEMENT Bibliography Anderson, Ronald J. 1974. Feeding artificial diets to smallmouth bass. Progressive Fish- Culturist 36(3): 145-151. Andrews, James W., and Jimmy W. Page. 1975. The effects of frequency of feeding on cul- ture of catfish. Transactions of the American Fisheries Society 1 04 (2) :3 17-321. Beyerle, George B. 1975. Summary of attempts to raise walleye fry and fingerlings on artifi- cial diets, with suggestions on needed research and procedures to be used in future tests. Progressive Fish-Culturist 37(2): 103-105. Bonn, Edward W., William M. Bailey, Jack D. Bayless, Kim E. Erickson, and Robert E. Stevens. 1976. Guidelines for striped bass culture. Striped Bass Committee, South- ern Division, American Fisheries Society, Bethesda, Maryland. 103 p. Brett, J. R. 1971. Growth responses of young sockeye salmon [Oncorhynchus nerka) to different diets and plans of nutrition. Journal of the Fisheries Research Board of Canada 28(10):1635-1643. 1971. Satiation time, appetite, and maximum food intake of sockeye salmon {On- corhynchus nerka). Journal of the Fisheries Research Board of Canada 28(3):409-415. Buterbaugh, Galen L., and Harvey Willoughby. 1967. A feeding guide for brook, brown and rainbow trout. Progressive Fish-Culturist 29(4):210-215. Cheshire, W. F., and K. L. Steele. 1972. Hatchery rearing of walleyes using artificial food. Progressive Fish-Culturist 34(2):96-99. Dawai, Shin-ICHIRO, and Shizunori Ideda. 1973. Studies of digestive enzymes of rainbow trout after hatching and the effect of dietary change on the activities of digestive en- zymes in the juvenile stage. Bulletin of the Japanese Society of Scientific Fisheries 39(7):819-823. Delong, Donald C, John E. Halver, and Edwin T. Mertz. 1958. Nutrition of salmonid fishes. VI. Protein requirements of chinook salmon at two water temperatures. Journal of Nutrition 65(4):589-599. DuPREE, Harry K. 1976. Some practical feeding and management techniques for fish farmers. Pages 77-83 in Proceedings of the 1976 Fish Farming Conference and Annual Conven- tion of the Catfish Farmers of Texas, Texas Agricultural and Mining University, Col- lege Station, Texas. , O. L. Green, and Kermit E. Sneed. 1970. The growth and survival of fingerling channel catfish fed complete and incomplete feeds in ponds and troughs. Progressive Fish-Culturist 32(2):85-92. Elliott, J. M. 1975. Weight of food and time required to satiate brown trout, Salmo trutta. Freshwater Biology 5:51-64. Fowler, L. G. 1973. Tests of three vitamin supplementation levels in the Abernathy diet. Pro- gressive Fish-Culturist 35(4): 197-198. , and J. L. Banks. 1976. Animal and vegetable substitutes for fish meal in the Aber- nathy diet. Progressive Fish-Culturist 38(3):123-126. , and J. L. Banks. 1976. Fish meal and wheat germ meal substitutes in the Abernathy diet, 1974. Progressive Fish-Culturist 38(3): 127-130. , and Roger E. Burrows. 1971. The Abernathy salmon diet. Progressive Fish- Culturist 33(2):67-75. Freeman, R. I., D. C. Haskell, D. L. Longacre, and E. W. Stiles. 1967. Calculations of amounts to feed in trout hatcheries. Progressive Fish-Culturist 29(4): 194-209. Graff, Delano R. 1968. The successful feeding of a dry diet to esocids. Progressive Fish- Culturist 30(3): 152. , and LeRoy Sorenson. 1970. The successful feeding of a dry diet to esocids. Progres- sive Fish-Culturist 32(l):31-35. NUTRITION AND FEEDING 261 Halvf.r, John E., editor. 1972. Fish nutrition. Academic Press, New York and London. 713 p. Hashimoto, Y. 197.5. Nutritional requirements of warmwater fish. Proceedings of the iUh International Congress of Nutrition, Mexico 3:1.58-17.'). H.\STINGS, W. H. 1973. Phase feeding for catfish. Progressive Fish-Culturist 3.')(4):19,')-19f). and Harry K. Dlpree. 1969. Formula feeds for channel catfish. Progressive Fish- Culturist 31(4):187-196. Hilton, J. W., C. Y. CjO, and S. J. Slinger. 1977. Factors affecting the stability of supple- mental ascorbic acid in practical trout diets. Journal of the Fisheries Research Board of Canada 34(5):683-687. Horak, Donald. 197,5. Nutritional fish diseases and symptoms. Colorado Division of Wildlife, Fishery Information Leaflet no. 29. 5 p. HUBLOU, Wallace F. 1963. Oregon pellets. Progressive Fish-Culturist 25(4): 17.5-180. , Joe Wallis, Thomas B. McKee. 1959. Development of the Oregon pellet diets. Ore- gon Fish Commission, Research Briefs, Portland, Oregon 7(l):28-56. Hurley, D. A., and E. L. Brannon. 1969. Effects of feeding before and after yolk absorption on the growth of sockeye salmon. International Pacific Salmon Fisheries Commission, Progress Report 21, New West Minster, British Columbia. 19 p. Inslee, Theophill'S D. 1977. Starting smallmouth bass fry and fingerlings on prepared diets. Project completion report (FH-4312), Fish Cultural Development Center, San Marcos, Texas. 7 p. Kra.MER, Chln and Mayo, Incorporated. 1976. Statewide fish hatchery program, Illinois, CDB Project Number 102-010-006. Seattle, Washington. La.viberton, Dale. 1977. Feeds and feeding. Spearfish In-Service Training School, US Fish and Wildlife Service, Spearfish, South Dakota. (Mimeo.) Lek D. J., and G. B. PutN-iKM. 1973. The response of rainbow trout to varying protein/energy ratios in a test diet. Journal of Nutrition 103(6) :916-922. LEiiRnz, Earl, and Robert C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of Fish and Game, Fish Bulletin 164. 197 p. Locke, David O., and Stanley P. Linscott. 1969. A new dry diet for landlocked Atlantic salmon and lake trout. Progressive Fish-Culturist 3l(l):3-10. LoVELL, Tom. 1979. Diet, management, environment affect fish food consumption. Commer- cial Fish Farmer and Aquaculture News 2(6):33-35. 1979. Fish farming industry becomes a rich source of animal protein. Commercial Fish Farmer and Aquaculture News 3(l):49-50. McCraren, Joseph P., and Robert G. Piper. Undated. The use of length-weight tables with channel catfish. US Fish and Wildlife Service, San Marcos, Texas. 6 p. (Typed report.) Nagel, Tim O. 1974. Rearing of walleye fingerlings in an intensive culture using Oregon moist pellets as an artificial diet. Progressive Fish-Culturist 36(l):59-61. 1976. Intensive culture of fingerling walleyes on formulated feeds. Progressive Fish- Culturist 38(2):90-91. 1976. Rearing largemouth bass yearlings on artificial diets. Wildlife In-Service Note 335, Ohio Department of Natural Resources, Division of Wildlife, Columbus. 6 p. National Research Council, Subcommittee on Fish Nutrition. 1973. Nutrient require- ments of trout, salmon and catfish. National Academy of Sciences, Washington, D.C. 57 p. , Subcommittee on Warmwater Fishes. 1977. Nutrient requirements of warmwater fishes. National Academy of Sciences, Washington, D.C. 78 p. Nelson, John T., Robert G. Bowker, and John D. Robinson. 1974. Rearing pellet-fed largemouth bass in a raceway. Progressive Fish-Culturist 36(2): 108-1 10. Orme, Leo E. 1970. Trout feed formulation and development. Pages 172-192 in European In- land Fisheries Advisory Commission Report of the 1970 Workshop on Fish Feed Tech- 262 FISH HATCHERY MANAGEMENT nology and Nutrition. U.S. Bureau of Sport Fisheries and Wildlife, Resource Publica- tion 102, Washington, D.C. , and C. A. Lemm. 1974. Trout eye examination procedure. Progressive Fish-Culturist 36(3): 165-168. Page, Jimmy W., and James W. Andrews. 1973. Interactions of dietary levels of protein and energy on channel catfish [ictalurus punctatus). Journal of Nutrition 103:1339-1346. Palmer, David D., Harland E. Johnson, Leslie A. Robinson, and Roger E. Burrows. 1951. The effect of retardation of the initial feeding on the growth and survival of sal- mon fingerlings. Progressive Fish-Culturist 13(2):55-62. , Leslie A. Robinson, and Roger E. Burrows. 1951. Feeding frequency: its role in the rearing of blueback salmon fingerlings in troughs. Progressive Fish-Culturist 13(4):205-212. Pearson, W. E. 1968. The nutrition of fish. Hoffmann-LaRoche, Basel, Switzerland. 38 p. Phillips, Arthur M., Jr. 1970. Trout feeds and feeding. Manual of Fish Culture, Part 3.b.5, Bureau of Sport Fisheries and Wildlife, Washington, D.C. 49 p. Satia, Benedict P. 1974. Quantitative protein requirements of rainbow trout. Progressive Fish-Culturist 36(2):80-85. Schmidt, P. J., and E. G. Baker. 1969. Indirect pigmentation of salmon and trout flesh with canthaxanthin. Journal of the Fisheries Research Board of Canada 26:357-360. Smith, R. R. 1971. A method for measuring digestibility and metabolizable energy of fish feeds. Progressive Fish-Culturist 33(3):132-134. Snow, J. R., and J. I. Maxwell. 1970. Oregon moist pellet as a production ration for large- mouth bass. Progressive Fish-Culturist 32(2): 101-102. Spinelli, John, and Conrad Mahnken. 1976. Effect of diets containing dogfish [Squalus acanthias) meal on the mercury content and growth of pen-reared coho salmon [On- corhynchus kisutch). Journal of the Fisheries Research Board of Canada 33(8):1771-1778. Stickney, R. R., and R. T. Lovell. 1977. Nutrition and feeding of channel catfish. Southern Cooperative Series, Bulletin 218, Auburn University, Auburn, Alabama. 67 p. TiEMElER, O. W., C. W. Deyoe, and S. Wearden. 1965. Effects on growth of fingerling chan- nel catfish of diets containing two energy and two protein levels. Transactions of the Kansas Academy of Science 68(l):180— 186. TWONGO, Timothy K., and Hugh R. MacCrimmon. 1976. Significance of the timing of ini- tial feeding in hatchery rainbow trout, Salmo gairdneri. Journal of the Fisheries Re- search Board of Canada 33(9):1914-1921. Windell, John T. 1976. Feeding frequency for rainbow trout. Commercial Fish Farmer and Aquaculture News, 2(4):14-15. , J. D. Hubbard, and D. L. Horak. 1972. Rate of gastric evacuation in rainbow trout fed three pelleted diets. Progressive Fish-Culturist 34(3):156-159. , James F. Kitchell, David O. Norris, James S. Norris, and Jeffrey W. Foltz. 1976. Temperature and rate of gastric evacuation by rainbow trout, Salmo gairdneri. Transactions of the American Fisheries Society 105(6):712-717. Wood, E. M., W. T. Yasutake, A. N. Woodall, and J. E. Halver. 1957. The nutrition of salmonoid (fishes: chemical and histological) studies of wild and domestic fish. Journal of Nutrition 6l(4):465-478. 5 Fish Health Management Control of diseases in hatchery fish can be achieved best by a program of good management. This involves maintaining the fish in a good environ- ment, with good nutrition and a minimum of stress. However, attempts should be made to eradicate the serious diseases from places where they oc- cur. Containment is accomplished by not transferring diseased fish into areas where the disease does not already exist. Eradication, when feasible and beneficial, involves the removal of infected fish populations and chemi- cal decontamination of facilities and equipment. In some cases, simply keeping additional disease agents from contaminated waters can result in effective eradication. Fish tapeworms can be transmitted to people who eat raw fish but, in general, fish diseases are not human health problems. The reasons for disease control are to prevent costly losses in hatchery production, to prevent transmission of diseases among hatcheries when eggs, fry, and broodstock are shipped, and to prevent the spread of disease to wild fish when hatchery products are stocked out. Although fish diseases themselves rarely trouble humans, control measures can create a hazard if fish are con- taminated with drugs or chemicals when they are sold as food. In local disease outbreaks, it is important that treatments begin as soon as possible. If routine disease problems, such as bacterial septicemia, can be recognized by the hatchery manager, treatment can begin sooner than if 263 264 FISH HAICHERY MANAGEMENT a diagnosis is required from a pathology laboratory. Broad- spectrum treat- ments based on a poor diagnosis are ill-advised, but treatment based on keen observation and awareness of signs can mean the difference between losing just a few fish or losing tens of thousands. Disease Characteristics Disease- Ca using Orga n isms Organisms that cause diseases in fish include viruses, bacteria, fungi, proto- zoans, and a wide range of invertebrate animals. Generally, they can be categorized as either pathogens or parasites, although the distinction is not always clear. For our purposes, we consider subcellular and unicellular or- ganisms (viruses, bacteria) to be pathogens. Protozoans and multicellular organisms (invertebrate animals) are parasites, and can reside either inside the host (endoparasites) or outside it (ectoparasites). Low numbers of either pathogens or parasites do not always cause disease signs in fish. Viruses are neither plant nor animal. They have been particularly suc- cessful in infecting fish. Viruses are submicroscopic disease agents that are completely dependent upon living cells for their replication. All known viruses are considered infective agents and often have highly specific re- quirements for a particular host and for certain tissues within that host. Deficiencies or excesses in the major components of the diet (proteins, amino acids, fats, carbohydrates, and fiber) often are the primary cause of secondary bacterial, fungal, and parasitic diseases. Fish with a diet deficient in protein or any of the indispensable amino acids will not be healthy and will be a prime target for infectious agents. The same is true of deficiencies of fatty acids or excesses of digestible carbohydrates. Secondary disease agents may infect a fish in which biochemical functions are impaired. Nu- tritional deficiences are discussed in more detail in Chapter 4. Disease Recognition Disease can be defined briefly as any deviation of the body from its normal or healthy state causing discomfort, sickness, inconvenience, or death. When parasites become numerous on a fish, they may cause changes in behavior or produce other obvious signs. Individual diseases do not always produce a single sign or characteristic that is diagnostic in itself. Nevertheless, by observing the signs exhibited one usually can narrow down the cause of the trouble to a particular type of causative agent. Some of the obvious changes in behavior of fish suffering from a disease, parasite, or other physical affliction are (l) loss of appetite; (2) abnormal FISH HEALTH MANAGEMENT 265 distribution in a pond or raceway, such as swimming at the surface, along the tank sides, or in slack water, or crowding at the head or tail screens; (3) flashing, scraping on the bottom or projecting objects, darting, whirling, or twisting, and loss of equilibrium; and (4) weakness, loss of vitality, and loss of ability to withstand stresses during handling, grading, seining, load- ing, or transportation. In addition to changes in behavior, disease may produce physical signs and lesions, or be caused by parasites that can be seen by the unaided eye. Signs observed may be external, internal, or both. For microscopic exami- nation, it may be necessary to call in a fish pathologist. Gross external signs of disease include discolored areas on the body; eroded areas or sores on the body, head, or fins; swelling on the body or gills; popeye; hemorrhages; and cysts containing parasites or tumors. Gross internal signs of disease are color changes of organs or tissue (pale liver or kidney or congested organs); hemorrhages in organs or tissues; swollen or boil-like lesions; changes in the texture of organs or tissues; accumulated fluid in body cavities; and cysts or tumors. If a serious disease problem is suspected, a pathologist should be con- tacted for assistance in isolating and identifying the causative agent. If a virus is suspected, contact a laboratory for analysis of tissues. Two other classes of disease are important to fish culturists, in addition to those caused by pathogenic organisms. One is nutritional in origin, and the other concerns environmental factors, including bad hatchery practices and poor water quality, that stress the fish. Stress and Its Relationship to Disease Stress plays a major role in the susceptibility of fish to disease. The differ- ence between health and sickness depends on a delicate balance resulting from the interactions of the disease agent, the fish, and the environment (Figure 78). For example, although bacteria such as species of Aeromonas, Pseudomonas, and Flexibacter are present continuously in most hatchery wa- ter supplies, disease seldom occurs unless environmental quality or the de- fense systems of the fish have deteriorated. Fish in intensive culture are affected continuously by environmental fluc- tuations and management practices such as handling, crowding, hauling, and drug treatment. All of these, together with associated fright, can im- pose significant stress on the limited disease defense mechanisms of most fishes. Table 36 presents a list of infectious diseases together with the stress factors known to be predisposing conditions. In addition to sophisti- cated physiological measurements, behavioral changes, production traits (growth, weight gain or loss, food conversion), morbidity, and mortality are factors that can be used to evaluate the severity of stresses. 266 FISH HATCHERY MANAGEMENT A B Figure 78. (A) Frequently, a fish population (l) must interact with a pathogen (2) in an unfavorable environment (3) for an epizootic (1-2-3) to occur. (B) Interaction of more than three factors may be required. In carp hemorrhagic sep- ticemia, a chronic virus infection (l) of the common carp (2), followed by expo- sure to Aeromonas liquefaciens (3) in a stressful environment (4), may be prere- quisites to an epizootic (1-2-3-4). (Source: Snieszko 1973.) Whereas some pathogens of fish are highly virulent and cause disease as soon as they invade a fish, most diseases are stress- related. Prevention of these diseases best can be done through good hatchery management. En- vironmental stresses and associated disease problems are minimized by high water quality standards, optimum rearing densities, and adequate nu- trition. Management stresses such as handling, stocking, drug treatments, haul- ing, or rapid temperature fluctuations of more than 5°F frequently are asso- ciated with the onset of several physiological diseases. Table 37 gives a par- tial listing of these fish cultural practices, their associated disease problems, and stress mitigation procedures if known. Disease Treatment A complete rearing season seldom passes during which fish do not require treatment for one disease or another. Every treatment should be considered a serious undertaking, and caution should be taken to avoid disastrous FISH HEALIU MANAGEMENT 267 Table 36. infectious diseases commonly considered io be stress-mediated in pacific salmon, frol i'. caifish, common carp, and shad. 'schrce: wedemeyer and wood 1974.) DISEASE STRES.S FACTORS PREDISPOSING TO INFECTION Furunculosis Bacterial gill disease Columnaris (Flexibacter columnaris) Corynebacterial kidney disease Aeromonad and Pseudomonad hemorrhagic septicemias Vibriosis (Vibrio anguillarum) Costia, Truhodina, Hexamita Spring viremia of carp Fin and tail rot Infectious hematopoietic necrosis (IHN) Cold water disease Channel catfish virus disease Low o,xygen; crowding; handling in the pres- ence of Aeromonas salmunicida; handling a month prior to an expected epizootic; elevated water temperatures. Crowding; chronic low oxygen (4 ppm); elevated ammonia (l ppm NH3-N); parti- culate matter in water. Crowding or handling during warmwater periods (59°F) if carrier fish are present in the water supply; for salmonids, a tem- perature increase to about rt8°F if the pathogen is present, e\en if fish are not crowded or handled. Low total water hardness (less than about 199 ppm as CaCO;^). Protozoan infections such as Costia, or Tri- chodina, accumulation of organic materials in water leading to increased bacterial load in water; particulate matter in water; han- dling; low oxygen; chronic sublethal expo- sure to heavy metals, pesticides, or poyl- chlorinated biphenyls (PCB'si; for com- mon carp, handling after over- wintering. Handling; dissolved oxygen lower than 6 ppm, especially at water temperatures of ,50-.59T; brackish water of lOl.Tppt. Overcrowding of fry and fingerlings; low oxygen; excessive size variation among fish in ponds. Handling after over-wintering at low tem- peratures. Crowding; improper temperatures; excessive levels of metabolities in the water; nutri- tional imbalances; chronic sublethal expo- sure to PCB's. Temperature decrease from .50°F to 4.5 5.i°F. Temperature decrease (from .50-,')9°F to 4,i-.iOT) if the pathogen is present; high water flow during yolk absorption, e.g., more than five gallons per minute in Heath incubators. Temperature above 68°F; handling; low oxy- gen: co-infection with Flexibacter, Aeromo- nas, or Pseudomonas; crowding. 268 FISH HATCHERY MANAGEMENT Table 37. physiological diseases, environmental factors implicated in their occl'rrknce, and recommended mitigation procedures. (source: WEDEMEYEK AND WOOD 1974.) DISEASE STRESS FACTORS IMPLICATED MITIGATION PROCEDURES Coagulated yolk (white spot) "Hauling loss" (delayed mortality) Blue sac (hydrocoel embryonalis) Rough handling; mala- chite green containing more than 0.()8"(i Zn'; gas supersaturation of I10"u or more; mineral deficiency in incuba- tion water. Hauling; stocking; rough handling Crowding; accumulation of nitrogenous meta- bolic wastes due to inadequate flow pat- terns. Use "Zn-free" malachite green (().()H"m Zn"); aer- ate; add CaCi^ to increase total hardness to 50 ppm (as CaCOy). Add 0.1-0.3". NaCl dur- ing hauling; add CaCl^ to raise total hardness to at least ,^0 ppm (CaCOy). Maintain NH3-N concen- tration lower than 1 ppm during egg incu- bation. Use of malachite green is not recommended. results. All drugs and chemicals used to control infectious organisms can be toxic to fish if concentrations are too high. All treatment calculations should be double-checked before being implemented (Appendix G). In hu- man or veterinary medicine, patients are treated on an individual basis under carefully controlled conditions, whereas fish populations are treated "en masse," often comprising hundreds of thousands of individuals. Treatment Methods There are two classes of treatments for fish disease, prophylactic and thera- peutic. Prophylactic treatments are protective or defensive measures designed to prevent an epizootic from occurring. Such treatments are used primarily against ectoparasites and stress- mediated bacterial diseases. Therapeutic treatments are begun only after disease signs appear. When therapeutic treatments are needed to control external parasites or bacterial gill disease, it may be a good indication of poor hatchery management. In fish diseases, as in human diseases, treatment with various medica- tions and chemotherapeutic agents is for the purpose of keeping the animals alive, i.e., for "buying time," not for killing 100% of the disease FISH HEALTH MANAGEMENT 269 organisms present. Medications hold disease organisms in check by retard- ing their growth or even killing the pathogen but, in the end, it is the fishes' own protective mechanisms that must overcome the disease if the treatment is to be successful. To cure a disease, not just treat it, the body must be helped to do the job itself. To be successful, every fish culturist, farmer, or hobbyist must keep this basic principle in mind every time a treatment is considered. Before treatment is begun, the following questions should be asked; whether or not to treat depends on the answers. 1. What is the prognosis, i.e., is the disease treatable and what is the pos- sibility of a successful treatment? 2. Is it feasible to treat the fish where they are, considering the cost, handling, prognosis, etc.? 3. Is it worthwhile to treat or will the cost of treating exceed the value of the fish? 4. Are the fish in good enough condition to withstand the treatment? 5. Does the loss rate and severity of the disease present warrant treat- ment? Before any treatment is started, four factors must be considered. The cul- turist must know and understand (l) the water source, (2) the fish, (3) the chemical, and (4) the disease. Failure to take all these factors into con- sideration can result in a complete kill of all of the treated fish, or a failure to control the disease with a resultant loss of many fish and wasted funds. (1) Water source. The volume of water of the holding or rearing unit to be treated must be calculated accurately before any treatment is applied. An overestimation of the water volume means too much chemical will be used, which probably will kill all the fish. An underestimation of the volume means not enough chemical will be used, thus the disease-causing organism may not be controlled. Water-quality factors, such as total hardness, pH, and temperature, will increase the activity of some chemicals and decrease that of others. In ponds, the amount and type of aquatic plants present also must be taken into consideration before any chemical is applied. (2) Fish. Fish of different kinds and ages react differently to the same drug or chemical. Certain species are much more sensitive to a particular chemical than others. The age of fish also will affect the way they react to a specific treatment. If a particular chemical or drug has never been used to treat fish at the hatchery, it is always a good idea to test it first on a small number of fish before an entire pond or holding unit is treated. This can be done in tanks or in small containers such as large plastic wastebaskets. (3) Chemical. The toxicity of the chemical should be known for the par- ticular species to be treated. The effect of water chemistry on the toxicity of the chemical also should be known. Some chemicals break down rapidly 270 KISH HATCHERY MANAGEMENT in the presence of sunlight and high temperatures and thus are less likely to be effective during summer months than during the cooler months of the year. Mixing chemicals may enhance or intensify the toxicity of one of them. Also, certain chemicals are toxic to plants and can cause an oxygen depletion if used in ponds at the wrong time. (4) Disease. Although disease may be a self-evident factor, it is disregard- ed widely, much to the regret of many fish culturists. Most of the chemi- cals used to treat fish diseases are expensive and generally are effective only against certain groups of organisms. Use of the wrong chemical or drug usually means that several days to a week may pass before one real- izes the treatment was not effective. During this time, large numbers of fish may be lost unnecessarily. When it is apparent that a treatment is necessary, the following rules must be adherred to: (a) Pretreatment Rules 1. Clean holding unit. 2. Accurately determine the water volume and flow rate. 3. Choose the correct chemical and double-check concentration figures. 4. Prevent leaks in the holding unit if a prolonged dip treatment is involved (see below). 5. Have aeration devices ready for use if needed. 6. Make sure of the route by which chemical solutions are discharged from the holding unit. (B) Treatment Rules 1. Dilute the chemical with water before applying it. 2. Make sure the chemical is well-mixed in the units or ponds. 3. Keep a close watch on units during treatment period. 4. Observe fish closely and frequently during treatment (aeration of water may be required). 5. Turn on fresh water immediately if fish become distressed. (C) Post Treatment Rules 1. Recheck fish to determine success of treatment. 2. Do not stress treated fish for at least 48 hours. Various methods of treatment and drug application have been used in the control of fish diseases. There is no one specific method that is better than others; rather, the method of treatment should be based on the specif- ic situation encountered. DIP TREATMENT During the dip treatments, small numbers of fish are placed in a net and dipped in a strong solution of chemical for a short time, usually 15-45 FISH HEALTH MANAGEMENT 271 seconds, that depends on the type of chemical, its concentration, and the species of fish being treated. Metal containers should not be used to hold the treatment solution because some chemicals can react with the metal and form toxic compounds, particularly if the water is acid. This method of treatment is dangerous because the difference between an effective dose and a killing dose often is very small. However, if done properly, it is very effective for treating small numbers of fish. Other disad- vantages to this method include its high labor costs and stress on the fish due to handling. PROLONGED BATH For prolonged- bath treatments, the inflowing water is cut off and the correct amount of chemical is added directly to the unit being treated (Appendix G). After a specified time, the chemical is flushed out quickly with fresh water. This treatment can be used in any unit that has an adequate supply of fresh water and can be flushed out within 5 to 10 minutes. Several precautions must be observed with this method to prevent seri- ous losses: (l) Because the water flow is turned off, the oxygen concentra- tion of the water may be reduced to the point that the fish are stressed and losses occur. The more fish per unit volume of water, the more likely this is to occur. Aerators of some type must be installed in the unit being treated to insure an adequate oxygen supply or must be available if needed. (2) Regardless of the treatment time that is recommended, the fish always should be observed throughout the treatment and, at the first sign of dis- tress, fresh water must be added quickly. (3) The chemical must be uni- formly distributed throughout the unit to prevent the occurrence of "hot spots" of the chemical. Fish being treated may be killed or severely injured by overdoses if they swim through hot spots. Conversely, fish that avoid these hot spots may not be exposed to a concentration high enough to be effective. The method used for distributing the chemical throughout the unit will depend on the kind of chemical being used, type and size of unit being treated, and equipment and labor available. Common sense must be used as it is impossible to lay down hard and fast guidelines that will cover every situation. INDEFINITE BATH Indefinite baths usually are used to treat ponds or hauling tanks. A low concentration of a chemical is applied and left to dissipate naturally. This generally is one of the safest methods of treatment. One major drawback, however, is that the large quantities of chemicals required can be expen- sive to the point of being prohibitive. Another drawback relates to the 272 FISH HATCHERY MANAGEMENT possible adverse effects on the pond environment. Some treatment chemi- cals are algicidal or herbicidal and may kill enough plants to ultimately cause an oxygen deficit. Other chemicals, such as formalin, may reduce dissolved oxygen levels as they degrade. As in prolonged- bath treatments, it is important that the chemical be evenly distributed throughout the culture unit to prevent the occurrence of hot spots. Special boats are available for applying chemicals to ponds. However, such chemical boats are fairly expensive and are not needed un- less large acreages are involved. For dry chemicals that dissolve rapidly in water, such as copper sulfate or potassium permanganate, burlap or any coarse-weave bags can be used. The required amount of chemical is put into a bag and towed behind the boat so that the chemical dissolves in the wake of the boat. Liquids and wettable powders can be applied evenly with hand or power sprayers or can be siphoned over the edge of a boat into the prop wash. As with the prolonged- bath method, there is no one correct way to apply a chemical evenly to the unit of water to be treated. Rather, the applica- tion will depend on the kind of chemical being used, the equipment avail- able, and the type of unit to be treated. FLUSH TREATMENT Flush treatments are simple, and consist of adding a solution of the treat- ment chemical at the upper end of a holding unit and allowing it to flush through. It has been used widely at trout and salmon hatcheries, but is sel- dom used at warmwater hatcheries. It is applicable only with raceways, tanks, troughs, or incubators for which an adequate flow of water is avail- able, so that the chemical is completely flushed through the unit or system within a predetermined time. Highly toxic chemicals should be avoided be- cause there is no way to assure a uniform concentration within the unit be- ing treated. CONSTANT-FLOW TREATMENT Constant-flow treatments are useful in raceways, tanks, or troughs in situa- tions where it is impractical or impossible to shut off the inflowing water long enough to use prolonged baths (Appendix G). The volume of water flowing into the unit must be determined accurately and a stock solution of the chemical metered into the inflowing water to obtain the desired concentration. Before the metering device or constant- flow siphon that delivers the chemical is started, enough chemical should have been added to the water in the device to give the desired concentra- tion. Upon completion of the desired treatment period, the inflow of chemi- cal is stopped and the unit is flushed by allowing the water flow to continue. FISH HEALTH MANAGEMENT 273 The method by which the chemical is metered into the inflowing water will depend on the equipment available and the type of unit to be treated. Although the constant- flow method is very efficient, it can be expensive because of the large volumes of water that must be treated. FEEDING AND INJECTION Treatment of certain diseases, such as systemic bacterial infections and cer- tain internal parasite infestations, requires that the drug be introduced into the fish's body. This usually is accomplished with feeds or injections. In the treatment of some diseases, the drug or medication must be fed or, in some way, introduced into the stomach of the sick fish. This can be done either by incorporating the medication in the food or by weighing out the correct amount of drug, putting it in a gelatin capsule, and then insert- ing it into the fish's stomach with a balling gun. This type of treatment is based on body weight; standard treatments are given in grams of active drug per 100 pounds of fish per day, in milligrams of active drug per pound of body weight, or in milligrams of active drug per kilogram of body weight. Medicated food may be purchased commercially, or prepared at the hatchery if only small amounts are needed (Appendix H). Once feed- ing of medicated food is begun, it should be continued for the prescribed treatment period. Large and valuable fish, particularly small numbers of them, sometimes can be treated best with injections of medication into the body cavity (in- traperitoneal) or into the muscle tissue (intramuscular). Most drugs work more rapidly when injected intraperitoneally. For both types of injections, but particularly intraperitoneal ones, caution must be exercised to insure that internal organs are not damaged. The most convenient location for intraperitoneal injections is the base of one of the pelvic fins. The pelvic fin is partially lifted, and the needle placed at the fin base and inserted until its tip penetrates the body wall. The needle and syringe should be held on a line parallel to the long axis of the body and at about a 45 degree angle downward to avoid internal organs (see Chapter 3, Figure 59). One can tell when the body wall has been pentrated by the sudden decrease of pressure against the needle. As soon as the tip of the needle is in the body cavity, the required amount of medication should be injected rapidly and the needle withdrawn. For intramuscular injections, the best location usually is the area immediately ahead of the dorsal fin. The syringe and needle should be held on a line parallel with the long axis of the body and at about a 45 degree angle downward. The needle is inserted to a depth of about 7 to ^ inch and the medication slowly is injected directly into the muscle tissue of the back. The injection must be done slowly, otherwise back pressure will force the medication out of the muscle through the channel created by the needle. 274 1 ISH HATCHERY MANAGEMENT General Information on Chemicals Because many drugs and chemicals will be federally registered in the future for use at fish hatcheries and historically have successfully controlled fish diseases, much information is provided in the following section. However, many have not been registered at this time by the United States Food and Drug Administration for use with fishes; reference to unregistered drugs and chemicals in this section and in other chapters of this book should not be construed as approval or endorsement by the United States Fish and Wildlife Service. In all cases where chemicals and drugs are discussed, their registration status is indicated. Chemicals purchased for hatchery use should be of United States Phar- maceutical (USP) grade, if possible, and stored in amber containers to prevent deterioration by sunlight. The chemical formula should be on the label. Treatment compounds must be stored as directed on the label, and lids or caps always should be tight. If chemicals become abnormal in color, texture, etc., they should be discarded. Poisonous chemicals should be han- dled only with proper safety precautions. Antibacterial agents currently used to control bacterial infections in fish include sulfonamides, nitrofurans, and antibiotics. The basic principle of chemotherapy is one of selective toxicity. The drug must destroy or elimi- nate the pathogen by either bactericidal or bacteriostatic action without side reactions to the host. Treatment of some diseases, such as columnaris, ulcer disease, and furun- culosis, requires the feeding of drugs. This is accomplished by mixing the drug with the fish's food. The amount of drug to be fed is relatively small and thorough mixing is necessary to insure proper distribution in the feed. Fish should be hungry before medicated feed is administered; therefore, it may be necessary to eliminate a prior feeding to insure that the treated food is taken readily. With the development of dry diets it now is possible to buy medicated feed containing the drug of choice. Fish of different sizes require use of varying amounts of food and drug, and custom milling may be necessary in order to deliver the proper dosage. When internal medication is begun, it should be maintained until the prescribed treatment period has been completed. It takes approximately 3 days to build up an effective drug level within fish. To maintain the drug level, the fish should receive only medicated food during the treatment period. Generally, once the medication is started, it is continued for 10-12 days or until mortality returns to normal, then extended for at least 3 more days. Drug combinations sometimes are more efficient than single drugs. The combination of sulfamerazine and furazolidone (not registered by the Food FISH HEALTH MANAGEMENT 275 and Drug Administration) often is used to advantage in treating bacterial infections. Chemicals and Their Uses SALT BATHS AND DIPS Fish infected with bacterial gill disease or external parasites often produce excessive amounts of mucus on their gills and body surface. This is a na- tural response to irritation. The mucus buildup, however, often protects the parasites or bacteria and successful treatment may be difficult. A salt (NaCl) treatment, by one of several means, often is helpful as it stimulates mucus flow, rids the fish of the excess mucus, and helps expose the parasites and bacteria to subsequent chemical treatment. Salt baths have some direct effectiveness against a few external proto- zoan parasites, fish lice, and leeches. As a prolonged bath treatment and for use in hauling tanks, salt is used at 1,000-2,000 parts per million (38-76 grams per 10 gallons; 283-566 grams per 10 cubic feet). As a dip treatment for leeches and fish lice, it is used at 30,000 parts per million or 3% (2.5 pounds per 10 gallons, 18.7 pounds per 10 cubic feet). Fish are left in the solution for up to 30 minutes or until they show signs of stress. FORMALIN Formalin (registered by the Food and Drug Administration) is one of the most widely used therapeutic agents in fish culture. It is 37% formaldehyde by weight and should be adjusted to contain 10-15% methanol. Methanol helps to retard formation of paraformaldehyde, which is much more toxic than formalin. Formalin should be stored at temperatures above 40°F be- cause on long standing, and when exposed to temperatures below 40°F, paraformaldehyde is formed. Acceptable formalin is a clear liquid. A white precipitate at the bottom of the container or a cloudy suspension indicates that paraformaldehyde is present and the solution should be discarded. Formalin is considered to be 100% active for the purpose of treating fish. It is effective against most ectoparasites, such as species of Trichodina, Cos- tia, and Ichthyophthirius (ich), and monogenetic trematodes. Although it is of little value in treating external fungal or bacterial infections of hatched fish, high concentrations (1,600-2,000 parts per million for 15 minutes) have controlled fungal infections on eggs of trout and catfish. Caution should be used when eggs are treated at these high concentrations. Forma- lin is used widely on fish as a bath treatment at 125-250 parts per million (4.4-8.8 milliliters per 10 gallons; 32.8-65.5 milliliters per 10 cubic feet) for 1 hour. However, at these concentrations, water temperature will affect the 276 FISH HATCHERY MANAGEMENT toxicity of formalin to fish. Above 70°F, formalin becomes more toxic; the concentration used for channel catfish should not exceed 167 parts per mil- lion for 1 hour (5.9 milliliters per 10 gallons; 43.8 milliliters per 10 cubic feet). At such high temperatures, concentrations higher than 167 parts per million should be used for bluegills or largemouth bass only with caution. In water temperatures above 50°F, salmonids become more sensitive to higher concentrations of formalin, and treatment levels should not exceed 167 parts per million for 1 hour. At higher temperatures and lower concen- trations of formalin, it may be necessary to repeat the treatment on two or more successive days to effectively control ectoparasites without damage to the fish. Aeration should always be provided during bath treatments to prevent low oxygen conditions from developing. At the first sign of stress, fresh water should be added to flush out the treatment. Formalin also can be used effectively as an indefinite treatment of most fish species in ponds, tanks, and aquaria at 15-25 parts per million if cer- tain precautions are used. Do not exceed 10 parts per million as an indef- inite treatment for striped bass fingerlings because the 96- hour LC50 (the concentration that kills 50'/u of the fish in 96 hours) is only 12 parts per million. Formalin removes 1 part per million oxygen for each 5 parts per million formalin within 30-36 hours, and it should be used with extreme caution, particularly during summer months, to minimize the chance of an oxygen depletion in the unit being treated. Formalin also is a very effective algicide so it should not be used in ponds with moderate to heavy phyto- plankton blooms. If it is necessary to use formalin in a pond that has a phytoplankton bloom, drain out one-third to one-half of the water prior to treatment. Within 12 to 16 hours after treating, start adding fresh water to bring the pond level back to normal. Fish treated with excessive concentrations of formalin may suffer delayed mortality. Rainbow trout yearlings, channel catfish fry and fingerlings, and bluegill fingerlings often are vulnerable in this way. Onset of deaths can occur anytime within 1 to 24 hours after treatment but may not occur until 48 to 72 hours later, depending on species of fish, size and condition of fish, and water temperatures. Clinical signs associated with delayed mortal- ities include piping at the water surface, gaping mouths, excess mucus, and pale color. Formalin also is toxic to humans but the strong odor and eye ir- ritation usually warn of its presence. A few people develop allergic responses to formalin. COPPER SULFATE Copper sulfate (registered by the Food and Drug Administration only as an algicide) is one of the oldest and most commonly used chemicals in fish culture and is considered to be 100"o active. It has been applied widely in FISH HEALTH MANAGEMENT 277 aquatic environments as an algicide and also has been an effective control for a variety of ectoparasites, including such protozoans as Trichodina, Cos- tia, Scyphidia (Ambiphrya), and Ich. Its major drawback is that its toxicity to fish varies with water hardness. It is highly toxic in soft water. Copper sulfate never should be used as an algicide or parasite treatment unless the water hardness is known, or unless a test has been run to determine its tox- icity to fish under the circumstances in which it is to be used. Even where it has been used with previous success, it should be used carefully; in at least one situation, dilution of a pond by heavy rainfall reduced water hardness to the point that previously used concentrations of copper sulfate killed many catfish. Copper sulfate generally is used as an indefinite pond treatment. As a rule of thumb, the concentration to use varies with water hardness as fol- lows: at 0-49 parts per million total hardness (TH), do not use unless a bioassay is run first; at 50-99 parts per million TH, use no more than 0.5-0.75 part per million (1.35-2.02 pounds per acre-foot); at 100-149 parts per million TH, use 0.75-1.0 part per million (2.02-2.72 pounds per acre- foot); at 150-200 parts per million TH, use 1.0-2.0 parts per million (2.72-5.4 pounds per acre-foot). Above 200 parts per million TH, copper rapidly precipitates as insoluble copper carbonate and loses its effectiveness as an algicide and parasiticide. In hard-water situations, a bioassay should be run to determine the effective concentration needed. It may be neces- sary to add acetic acid or citric acid to hard water to keep the copper in solution. The commonly used ratio is 1 part CUSO4 to 3 parts citric acid. Although copper sulfate has been touted as an effective control for cer- tain external bacterial infections, such as bacterial gill disease, fin rot and columnaris, and fungal infections, it has proven to be ineffective against these diseases on warmwater fish. Other chemicals are much better for con- trolling these organisms. Copper sulfate should be used with great caution, if at all, in warmwater fish ponds during the summer, particularly if an algal bloom is present. Copper sulfate is a very potent algicide, and it quickly can cause oxygen depletion by killing the bloom. Therefore, it should be used in hot weather only if adequate aeration devices or fresh water are available. POTASSIUM PERMANGANATE (KMnOj Potassium permanganate (registered by the Food and Drug Administration) is 100% active. It is used widely in warmwater fish culture as a control for external protozoan parasites, monogenetic trematodes, and external fungal and bacterial infections. Because it does not deplete oxygen levels, KMn04 is a safe treatment in warm temperatures and in the presence of algal blooms. 278 FISH HATCHERY MANAGEMENT Recommendations for its use vary from 2 parts per million (5.4 pounds per acre- foot) to as much as 8 parts per million (21.6 pounds per acre-foot) as an indefinite pond treatment. At 2 parts per million it is not toxic to catfish or centrarchids, but it can be very toxic at greater concentrations unless there is a significant amount of organic matter in the water. There- fore, before a concentration higher than 2 parts per million is used, it is imperative that a bioassay be run with both fish and water from the unit to be treated. In most situations, it is best to use 2 parts per million even though the treatment may have to be reapplied within 24 hours to be effec- tive. It has been recommended that 3 parts per million be used to treat trout with excessive gill proliferation associated with chronically poor environ- mental conditions. However, as in all cases, it is best to test this concentra- tion on a few of the trout before it is applied to the entire lot. Potassium permanganate imparts a deep wine-red color to water. Upon breaking down, the color changes to dirty brown. If a color change occurs in less than 12 hours after KMn04 has been applied, it may be necessary to repeat the treatment. Potassium permanganate also is used widely to help alleviate oxygen de- ficiencies in warmwater ponds. Although it does not add oxygen to the water, as has been suggested by some, it does help reduce biological oxy- gen demand by oxidizing organic matter in the pond. QUATERNARY AMMONIUM COMPOUNDS Quaternary ammonium compounds are not registered by the Food and Drug Administration. Such chemicals as Roccal, Hyamine 3500, and Hy- amine 1622 are bactericidal but will not kill ectoparasites. They generally are used for controlling external bacterial pathogens and for disinfecting hatchery equipment. Like many chemicals used in external treatments, they become more toxic at high temperatures and in soft water. The quaternary ammonium compounds commonly are used to treat salmonids for bacterial gill disease. A standing bath of 2 parts per million (active in- gredients) of Hyamine 3500 or Roccal for one hour usually is successful. Hymane 1622 has been used by some culturists who find Hyamine 3500 too toxic for salmon fingerlings. Treatments should be conducted for 3 or 4 consecutive days. Quaternary ammonium compounds may be purchased as liquids of vari- ous strengths. A 50% solution is an excellent consistency to use but, when exposed to air, it may evaporate, changing the concentration. Hyamine 1622 may be purchased as a 100% active-ingredient powder that goes into solution easily when added to warm water but tends to form a sticky mass if water is poured over it. A respirator should be worn when this com- pound is used. FISH Hl.Al.lH MANA(;EMENI" 279 Hyamine 3500 is a standardized quaternary ammonium compound con- taining a high percentage of desirable components and very few undesir- able ones. It has proven very satisfactory for the treatment of external bacterial infections of trout and salmon. Hyamine 3500 is a 50% solution and can be used directly, or first diluted to a 10"() solution. In either case, Hyamine 3500 should be used at a final dilution of 2 parts per million (based on active ingredients) for 1 hour. In the case of Roccal, shipments may vary in toxicity to both the fish and the bacteria. Whenever a new supply is received, it should be tested on a few fish before being used in a production unit. Some quaternary ammonium compounds, such as Roccal, have been used to treat external bacterial infections in salmonids for many years with varying degrees of success. Their big drawback has been the variable com- position of different lots; they gave good control sometimes, but killed fish at others. The quaternary ammonium compounds have seen little use in warmwater fish culture, except for the disinfection of equipment, tanks, and troughs. However, these compounds are excellent bactericides and should be effec- tive as tank treatments in controlling external bacterial infections of catfish. TERRAMYCIN^ Terramycin (oxytetracycline) (registered by the Food and Drug Adminis- tration) is a broad-spectrum antibiotic widely used to control both external and systemic bacterial infections of fish. It is available in many formula- tions, both liquid and powder. As a prolonged-bath treatment in tanks, it is used at 15 parts per million active ingredient (0.57 gram active ingredient per 10 gallons; 4.25 grams active ingredient per 10 cubic feet) for 24 hours. The treatment may have to be repeated on 2 to 4 successive days. External bacterial infections, such as columnaris and bacterial gill disease in salmonids, often are treated successfully in troughs and tanks with '^- to 1-hour exposures to the Terramycin Soluble Powder in solution. One successful treatment uses 1.75 grams of formulation (as it comes from the package) per 10 gallons of water. In tanks and troughs, the technique requires lowering the water below the normal volume, adding the lerramy- cin (dissolved in some water), allowing the water to refill to the desired lev- el, and then turning off the flow. Aeration must be provided. Foaming can be a problem. After the proper length of time, the normal water flow is turned back on and allowed to flush the unit. Where small numbers of large or valuable fish are involved, Terramycin can be injected intraperitoneally or intramuscularly at 25 milligrams per pound of body weight. 280 FISH HATCHERY MANAGEMENT If it is desirable to administer Terramycin orally for the treatment of sys- temic bacterial diseases of catfish, it should be fed at 2.5-3.5 grams active per 100 pounds of fish per day for 7-10 days. If the fish are being fed ap- proximately 3% of their body weight daily, it is necessary to incorporate 83.3-116.7 grams of active Terramycin per 100 pounds of food. Under no circumstances should the treatment time be less than 7 days; 10 days is recommended. For the treatment of furunculosis and other systemic bacterial diseases of salmonids, Terramycin should be fed at the rate of 4 grams active in- gredient per 100 pounds of fish per day for 10 days. Occasionally, it may be necessary to add Terramycin to small amounts of food. This may be done by mixing an appropriate amount of TM-50, TM-50D, or Terramycin Soluble Powder in a gelatin solution (40 grams gelatin to 1 quart of warm water) and spraying it over the daily food ra- tion. The water-soluble powder concentrate of Terramycin is the easiest form with which to work. This form may be purchased in 4-ounce preweighed packages, each of which contains 25.6 grams of antibiotic. As much as two packages of this form may be dissolved in 1 quart of warm gelatin solution. If fry or small fingerlings must be treated, it is possible to combine 1 pound of fresh beef liver (run through a blender), 1 pound of meal- type feed, 2 raw eggs, and 2.5 grams of active Terramycin into a dough-like consistency. Refrigerate and feed as needed. NITROFURANS Nitrofurans are not registered by the Food and Drug Administration. Furazolidone (NF-180, Furox-50) and nitrofurazone (Furacin) are closely related compounds that have been widely used to treat bacterial infections in warm- and cold-blooded animals. They are available in several different formulations, but the most common contain either 11% or 4.59% active ingredient (49.9 grams active ingredient per pound of formulation). Furazolidone effectively treats furunculosis and redmouth disease in sal- monids, particularly if these pathogens have developed a resistance to Ter- ramycin or sulfonamides. It is fed at the rate of 2.5-4.5 grams active ingredient per 100 pounds of fish per day for 10 days. However, a slightly different method has been used by some workers who feed at the rate of 2.5 grams active ingredient per 100 pounds of fish for 3 days, followed by a 20-day course of 1.0 gram active ingredient per 100 pounds of fish. Because furazolidone breaks down rapidly in wet (meat or fish) diets, it should be fed in a dry pelleted feed or mixed fresh for each feeding if a wet diet must be used. FISH HEALTH MANAGEMENT 281 For the treatment of Aeromonas, Pseudomonas, and Flexibacter sp. infec- tions in catfish, the nitrofurans are fed at the rate of 4-5 grams active in- gredient per 100 pounds of fish per day for 7-10 days. If the fish under treatment are being fed at 3% of their body weight daily, it is necessary to incorporate 133-167 grams active ingredient per 100 pounds of food. Fish never should be fed either of the nitrofurans for less than 7 days. Nitrofurans have been used as a prolonged- bath treatment for external bacterial infections and as a prophalaxis during the transport of warmwater fish. The levels recommended vary from 5 to 30 parts per million active in- gredient. However, severe losses of channel catfish sac fry and swim- up fry have occurred during treatment with 15 and 25 parts per million active ni- trofurozone. Five parts per million should be adequate. It is suggested that nitrofurazone not be used to treat channel catfish sac fry or swim- up fry. If it must be used, apply only the lowest concentration, with caution. Furanace (P-7138, nitrofurpirinol) is a relatively new nitrofuran that has been used to control bacterial infections of trout and salmon. It also ap- pears effective against bacterial infections in catfish, although it has been used only on a limited basis for that species. Continued treatment of catfish is discouraged because furanace may cause injury to the skin during prolonged exposures. In trout and salmon culture, furanace is used as a bath at 1 part per million active ingredient (0.038 gram per 10 gallons; 0.283 gram per 10 cubic feet) for 5-10 minutes, or at 0.1 part per million active ingredient (0.0038 gram active per 10 gallons; 0.0283 gram active per 10 cubic feet) for an indefinite period. It is also fed at 100-200 milligrams of active ingredient per 100 pounds of fish for 3-5 days. Thus, if fish are being fed 3"(i of their body weight daily, it is necessary to have 3.3-6.7 grams of active ingredient per 100 pounds of food. SULFONAMIDES Sulfonamides have been used since 1946 to treat bacterial infections of sal- monids, but have been applied rarely to warmwater fish. They are reg- istered by the Food and Drug Administration. Presently, sulfamerazine and sulfamethazine are the sulfonamides most widely used. Generally, they are fed at a therapeutic level of 5-10 grams of drug per 100 pounds of fish per day for 10-21 days. Sulfonamides may be toxic to some fish species when the high dosages (lO grams per 100 pounds of fish per day or more) are fed. However, with the possible exception of bacterial hemorrhagic septicemia caused by Aeromonas hydrophilia or Pseu- domonas fluorescens, high drug levels seldom are required. ACRIFLAVINE Acriflavine is not registered by the Food and Drug Administration. A bac- teriostat, it has been used widely for many years in the treatment of 282 FISH HATCHERY MANAGEMENT external bacterial infections of fish and as a prophylaxis in hauling tanks, but results are not dependable. It is available either as acriflavine neutral or as a hydrochloride salt and is considered lOO'/^i active. Generally, it is used at 3-5 parts per million (0.11-0.19 gram per 10 gallons; 0.85-1.4 grams per 10 cubic feet) in hauling tanks and at 5-10 parts per million (0.19-0.38 gram per 10 gallons; 1.4-2.8 grams per 10 cubic feet) in holding tanks. Cost prohibits the use of acriflavine in large volumes of water, such as ponds. CALCIUM HYDROXIDE Calcium hydroxide (slaked lime or hydrated lime) is registered by the Food and Drug Administration. It is used as a disinfectant in ponds that have been drained. Although calcium oxide (quicklime) probably is better, it is more dangerous to handle and less readily available. Calcium hydrox- ide is used at the rate of 1,000-2,500 pounds per acre (0.02-0.06 pound or 10-26 grams per square foot) spread over the pond bottom. lODOPHORES lodophores are not registered by the Food and Drug Administration. Beta- dine and Wescodyne, non-selective germicides, are iodophores that success- fully disinfect fish eggs. lodophores are much more effective for this than other disinfectants such as acriflavin and merthiolate. Green or eyed eggs usually are disinfected in a net dipped into a large tub or a shallow trough with no inflowing water. After 10 minutes, the eggs should be removed and promptly rinsed in fresh water. For a more extensive description of the use of iodophores, see Chapter 3. DI-7V^BUTYL TIN OXIDE Di-ra-butyl tin oxide (di-n- butyl tin laureate) is not registered by the Food and Drug Administration. It is effective against adult tapeworms in the lu- men of the intestinal tract, and should be equally so against nematodes and spiny-headed worms, when given orally at the rate of 114 milligrams per pound of fish or fed for 5 days at 0.3"/!i of food (0.3 pound per 100 pounds of food). MASOTEN® Masoten (Dylox) is registered by the Food and Drug Administration, and can be obtained in a variety of formulations; most common is the 80% wettable powder (W.P.). It is used as an indefinite pond treatment to con- trol ectoparasites such as monogenetic trematodes, anchor parasites, fish FISH HEALTH MANAGEMENT 283 lice, and leeches. The application rate is 0.25 part per million active (0.84 pound of 80% W.P. per acre- foot). One treatment will suffice for mono- genetic trematodes, leeches, and fish lice. For effective control of anchor parasites, Masoten should be applied four times at 5-7-day intervals. Because Masoten breaks down rapidly at high temperatures and high pH, it may give inconsistent results in summer. If it must be used then, ap- plications should be made early in the morning, and at double strength when water temperatures are above 80°F. Equipment Decontamination The following procedures for the decontamination of hatchery equipment is taken from Trout and Salmon Culture by Leitritz and Lewis (1976). Equipment sometimes must be decontaminated. One of the best and cheapest disinfectants is chlorine. A solution of 200 parts per million will be effective in 30—60 minutes; one of 100 parts per million may require several hours for complete sterilization. Chlorine levels are reduced by organic material such as mud, slime, and plant material; therefore, for full effectiveness, it is necessary to thoroughly clean equipment before it is exposed to the solution. A chlorine solution also loses strength when expo- sed to the air, so it may be necessary to add more chlorine or make up fresh solutions during disinfection. Chlorine is toxic to all fish. If troughs, tanks, or ponds are disinfected, the chlorine must be neutralized before it is allowed to drain or to enter waters containing fish. One gallon of 200 parts per million chlorine solution can be neutralized by 5.6 grams of sodium thiosulfate. Neutralization can be determined with starch-iodide chlorine test paper or with orthotolidine solution. A few drops of orthotolidine are added to a sample of the solution to be tested. If the sample turns a reddish- brown or yellow color, chlorine is still present. Absence of color means that the chlorine has been neutralized. Chlorine may be obtained as sodium hypochlorite in either liquid or powdered (HTH) form. The latter is the more stable of the two, but it is more expensive. The amount of chlorine added to water depends on the percentage of available chlorine in the product used. As an example, HTH powder may contain either 15, 50, or 65% available chlorine. Therefore, the following amounts would be needed to make a 200 parts per million solu- tion: 2 ounces of 15% available chlorine HTH powder to 10.5 gallons of wa- ter; 1 ounce of 50% available chlorine HTH powder to 18 gallons of water; 1 ounce of 65% available chlorine HTH powder to 23.25 gallons of water. 284 FISH HATCHERY MANAGEMENT Facility Decontamination In recent years, as fish production has increased at comparatively high costs, prevention and control of diseases have assumed major importance. Some diseases are controlled quite easily. For those that presently cannot be treated, the only successful control is complete elimination of all infect- ed fish from a hatchery, thorough decontamination of the facility, develop- ment of a new stock of disease- free fish, and maintenance of disease- free conditions throughout all future operations. Hatchery decontamination has been successful in removing corynebacteria and IPN virus in many cases. However, this method is practical only at those hatcheries having a con- trolled water supply originating in wells or springs that can be kept free of fish. ELIMINATION OF FISH During decontamination, all dead fish should be destroyed by deep burial and covered with lime. The burial grounds should be so located that leach- ing cannot recontaminate the hatchery water supply. All stray fish left in pipelines will be destroyed by chlorine, but it is important that their car- casses be retrieved and destroyed. PRELIMINARY OPERATIONS Before chemical decontamination of the hatchery is started, several prelimi- nary operations are necessary. The capacities of all raceways and troughs are measured accurately. The areas of all floor surfaces in the buildings are calculated, and allowance is made for 3 inches of solution on all floors. Then, the quantity of sodium hypochlorite needed to fill these volumes with a 200 parts per million solution is computed. It the chlorine solution will enter fish- bearing waters after leaving the hatchery, it will have to be neutralized. Commercial sodium thiosulfate, used at the rate of 5.6 grams for each gallon of 200 parts per million chlorine solution, will suffice. All loose equipment should be brought from storage rooms, scrubbed thoroughly with warm water and soap, and left near a raceway for later decontamination. Such equipment includes buckets, pans, small troughs, tubs, screens, seines, and extra splash boards. During this operation, any worn-out equipment should be burned or otherwise destroyed. Hatching and rearing troughs should be scrubbed clean. The sidewalls of all race- ways should be scrubbed and the bottom raked. Particular attention should be given to removing any remaining fish food, pond scum, or other organic substances. FISH HEALTH MANAGEMEN I 285 DECONTAMINATION The actual administration of chlorine varies among hatcheries, so only gen- eral procedures will be given here. Decontamination methods should assure that the full strength (200 parts per million) of the chlorine is maintained for at least 1 hour, and that a concentration of not less than 100 parts per million is maintained for several hours. Many hatcheries are so large that total decontamination cannot be completed in one day. Treatment then must be carried out by areas or blocks, and started at the upper end of the hatchery. Before chlorine is added, all ponds, raceways, and troughs are drained. Additional dam boards are set in certain sections to hold the water to the very top of each section. Rearing troughs are plugged, so they will over- flow, and drain outlets from the hatchery blocked. The required quantity of chlorine then is added gradually to the incoming water that feeds the head trough. The solution flows to the various rearing troughs, which are allowed to fill and overflow until there are 3 inches of the chlorine solution on the floor. The incoming water then is turned off or bypassed. The chlorine solution is pumped from the floor and sprayed on the sides and bottoms of all tanks and racks, the walls and ceiling, head trough, and any other dry equipment for 1 hour. The same procedure must be used in all rooms of every building, with special attention being given to the food storage room. Underground pipelines must be filled and flushed several times. If the hatchery must be decontaminated in sections, the work should be so planned and timed so that all buildings, springs, supply lines, and raceways contain maximum chlorine at the same time, so that no contam- inated water can enter parts of the system already treated. While a max- imum concentration of chlorine is being maintained in the raceway system, all loose equipment such as pails, tubs, trays, splashboards, and other ma- terial may be immersed in the raceways. Care must be taken that wooden equipment is kept submerged. Throughout the course of the project, checks should be made on the approximate chlorine strength with the orthotolidine test or chlorine test papers. If any section holds a concentration below 100 parts per million chlorine after 1 hour, the solution should be fortified with additional chlorine. Finally, the solution is left in the hatchery until no chlorine can be detected in the holding unit. This may take several days. MAINTENANCE OF THE HATCHERY After a hatchery has been decontaminated and is pathogen-free, recontami- nation must be prevented. The movement of any live fish into the hatchery should be forbidden absolutely and production should be restarted only with disinfected eggs. The spread of disease can be prevented only by rigid 286 FISH HAICHERV MANAGEMENT cleanliness. All shipped-in equipment should be decontaminated thor- oughly before it is placed in contact with clean hatchery equipment and water. The liberal use of warm water and soap is recommended. All trucks and equipment should be decontaminated before they enter the hatchery. The drivers and helpers should not be allowed to assist in loading fish. A "KEEP IT CLEAN" motto should be adopted and hatchery staff impressed with the idea that one slip-up in cleanliness may nullify all pre- vious efforts. Defense Mechanisms of Fishes As with all living organisms, fish stay healthy only if they prevent exces- sive growth of micro-organisms on their external surfaces and invasion of their tissues by pathogenic agents. Invasion is inhibited by tissues that pro- vide a physical barrier and by natural or acquired internal defense mechan- isms. Physical barriers are important, but give variable degrees of protection. Fish eggs are protected by the structurally tough and chemically resistant chorion. However, during oogenesis the egg may become infected or con- taminated with viruses and bacteria living in the female. Once hatched, the delicate fry again are vulnerable to invasion. Fishes are protected from injury and invasion of disease agents by the external barriers of mucus, scales, and skin. For example, the skin of sal- mon protects against fungi by continuously producing and sloughing off mucus, which allows fungi only temporary residence on the host. Mucus also may contain nonspecific antimicrobial substances, such as lysozyme, specific antibacterial antibodies, and complement-like factors. Gill tissue contains mucus cells that can serve the same purpose as those in the skin. However, irritants may cause accumulation of mucus on the gill tissue and lead to asphyxiation. This is an example of a defense mechanism that can work against the host. Internal defenses of the fish can be divided into natural nonspecific defenses and induced defenses. Induced defenses can be either specific or nonspecific. One of the primary natural defense mechanisms is the inflam- matory response of the vascular (blood) system. Defense agents in capillary blood respond to invasion of pathogenic agents and other irritants. Dila- tion of capillaries increases the supply of humoral and cellular agents at the focus of infection. The inflammatory response proceeds to dilute, local- ize, destroy, remove, or replace the agent that stimulated the response. Fish, like most animals, have an important defense mechanism in the form of fixed and wandering phagocytes in the lymphatic and circulatory sys- tems. Phagocytes are cells capable of ingesting bacteria, foreign particles, and other cells. Fish also have natural, noninduced humoral defenses FISH HEALTH MANAGEMENT 287 against infectious disease that are intrinsic to the species and individual. These defenses account for the innate resistance of various species and races of fish to certain diseases. For example, IHN virus affects sockeye and chinook salmon and rainbow trout fry, but coho salmon appear resis- tant to the disease. Rainbow trout are less susceptible to furunculosis than brook trout. Fish have immunological capabilities. Under favorable circumstances fish are able to produce gamma globulins and form circulating antibodies in response to antigenic stimuli. They also are capable of immunological memory and proliferation of cells involved in the immune response. The immune response of cold-blooded animals, unlike that in warm-blooded ones, depends upon environmental temperature. Lowering of the water temperature below a fish's optimum usually reduces or delays the period of immune response. Other environmental factors that stress fish also can reduce the immune response. Adaptive responses to disease occur in natural populations of fish. Sig- nificant heritabilities for resistance to disease exist, and selection to in- crease disease resistance in controlled environments can be useful. Inten- tionally or unintentionally, specific disease resistance has been increased at many hatcheries by the continued use of survivors of epizootics as broodstock. Increases in resistance to furunculosis in selected populations of brook and brown trout have developed in this way. Potential exists for genetic selection and breeding to increase disease tolerance in all propagat- ed fishes but certain risks must be anticipated in any major breeding pro- gram. Under controlled environmental conditions, resistance to a single disease agent through a breeding program can be expected. However, simultane- ous selection for tolerance of several disease agents can be extremely diffi- cult, except perhaps for closely related forms. In any natural population, individual fish may be found that are resistant to most of the common diseases. Pathogenicity of disease agents varies from year to year and from location to location, probably as a result of environmental changes as well as strain differences of the disease agents. When environmental conditions are favorable for a pathogen, the fish that can tolerate its effect have a selective advantage. However, when conditions favor another pathogen, other individual fish may have the advantage. Natural recombination of the breeding population assures that these variations are reestablished in each new generation of the population. Any propagation program must en- sure that this variability is protected to retain stability of the stocks. Managers always run the risk of decreasing the fitness of their stock in selective breeding programs; changes in gene frequencies resulting from selection for disease resistance may cause undesirable changes in the fre- quencies of other genes that are unrelated to disease resistance. 288 FISH HATCHERY MANAGEMENT Immunization of Fishes In the past few years there has been rapid development in the technology of fish vaccination, primarily for salmonids. In the 1977 Proceedings of the International Symposium on Diseases of Cultured Salmonids, produced by Ta- volek, Inc., T. P. T. Evelyn thoroughly reviewed the status of fish immuni- zation; excerpts of his report are presented in this section. Pressures conspiring to make vaccination an attractive and almost inevit- able adjunct approach to fish health were probably most acutely felt in the United States where it was becoming increasingly clear that reliance on the use of antimicrobial drugs in fish culture might have to be reduced. First, the list of antibacterial drugs that could legally be used is extremely small. ..and the prospects for enlarging the list were dim. Second, the effec- tiveness of the few available antibacterial drugs was rapidly being dimin- ished because of the development of antibiotic resistance among the bacterial fish pathogens. Third, there was the danger that this antibiotic resistance might be transmissible to micro-organisms of public health con- cern, and because of this there was the very real possibility that drugs now approved for use in fish culture would have their approval revoked. Finally, viral infections in fish could not be treated with any of the antibi- otics available. Faced with the foregoing situation, American fish culturists were forced to consider other measures that might help to ensure the health of their charges. One obvious approach was immunization. Advantages of immuni- zation were several. First, immunization did not generate antibiotic resis- tant micro-organisms; second, it could be applied to control viral as well as bacterial diseases; third, it appeared that fish may be vaccinated economi- cally and conveniently while still very small; and fourth, protection con- ferred by vaccination was more durable than that resulting from chemo- therapy, and could be expected to persist for considerable periods follow- ing vaccination. Finally, with killed vaccines, at least, the requirements for licensing the vaccines were less stringent than those required for the regis- tration of antimicrobial drugs. Unfortunately, the biggest single factor working against the widespread use of fish vaccination was the lack of a safe, economical and convenient technique for vaccinating large numbers of fish. Recent advances in sal- monid immunization are very promising. Vaccination Methods Attempts at oral vaccination have been unsuccessful, and alternative pro- cedures have been devised: mass inoculation; infiltration; and spray vacci- nation. FISH HEALTH MANAGEMENT 289 The mass inoculation method works well with fish in the 5-25 gram range, and individual operators are able to vaccinate 500-1,000 fish per hour. Cost of the technique seems reasonable but the number of fish that can be treated is limited by the manpower available for short-term employ- ment and by the size of the inoculating tables. The infiltration method (hyperosmotic immersion) allows vaccination of up to 9,000 fish (1,000 to the pound) quickly and safely in approximately 4 minutes. The method utilizes a specially prepared buffered hyperosmotic solution. Through osmosis, fluid is drawn from the fish body during its im- mersion in the buffered prevaccination solution. The fish are then placed into a commercially prepared vaccine that replenishes the body fluids and simultaneously diffuses the vaccine or bacterin into the fish. Fish are spray vaccinated by removing them briefly from the water and spraying them with a vaccine from a sand-blasting spray gun. Antigenicity of the preparations is markedly enhanced by the addition of bentonite, an absorbent. Spray vaccination against vibriosis protected coho salmon for at least 125 days. Most importantly, the method appears, like the injection method, to be a successful delivery system for all four bacterins tested (two Vibrio species, Aeromonas salmonicida, and a kidney disease bacterium). In 1976, two bacterins were licensed for sale and distribution by the United States Department of Agriculture. These products are enteric red- mouth and Vibrio anguillarum bacterins. Fish Disease Policies and Regulations Current disease-control programs are administered by the Colorado River Wildlife Council, the Great Lakes Fishery Commission, the United States Fish and Wildlife Service, numerous states, and several foreign countries. Most of the state and national programs include important regulations to restrict certain diseases. Very few programs have regulations requiring des- truction of diseased fish and only California has provisions for indemnifica- tion of losses sustained in eradication efforts. The last 20 years have seen a gradual change in disease control emphasis from treatment to prevention. International, federal, and state legislation have been passed to minimize the spread of certain contagious diseases of fish. The use of legal and voluntary restrictions on the transportation of diseased plants and animals, including fish, is not new. In the United States, the Department of Agriculture has an extensive organization for the reporting and eradication of certain plant and animal diseases. Unfor- tunately, this program does not cover fish. Both compulsory and voluntary regulations have been used to fight diseases in other animals. Some disease eradication methods are severe, such as the prompt destruction of entire 290 FISH HATCHERY MANAGEMEN 1 herds of cattle in the United States and Great Britain if hoof-and-mouth disease is discovered in any individual. Pullorum disease of poultry also is dealt with severely, but on a more voluntary basis. Growers have their flocks checked periodically and destroy populations if any individuals have the disease. The success of the regulations is shown by the rare occurrences of these diseases in areas where they are enforced. In 1967, Code of Federal Regulations, Title 50, Chapter 1, Part 13, Im- portation of Wildlife or Eggs Thereof, was amended. To Section 13.7 was added the stipulation that the importation to the United States of sal- monids and their eggs can be done only under appropriate certification that they are free of whirling disease and viral hemorrhagic septicemia un- less they were processed by certain methods or captured commercially in the open sea. In 1976, Canada passed federal Fish Health Protection Regu- lations (PC 1976-2839, 18 November 1976) that reflect concern over the dissemination of infectious fish diseases via international and interprovin- cial movement of cultured salmonids. The Canadian regulations deal with all species and hybrids of fish in the family Salmonidae. Both live and dead shipments of fish are covered and a dozen different fish pathogens or disease conditions are prohibited. Many states have passed restrictive regulations or policies that limit the introduction of infected or contaminated fish. In 1973, the western states of the Colorado River Wildlife Council adopted a Fish Disease Policy that prohibits the importation into the Colorado River drainage system of fish infected with one or more of eight disease pathogens. The policy describes strict inspection and certification procedures that must be passed before live fish or eggs may be transported to hatcheries or waters in the drainage of the Colorado River. To support the policy, each of the seven states and the Fish and Wildlife Service passed rules and regulations that support the intent of the Council. Fish disease control in the Great Lakes Basin is the responsibility of the natural resource agencies responsible for managing the fisheries resources. The Fish Disease Control Committee of the Great Lakes Fishery Commis- sion has developed a program to unify and coordinate the disease-control efforts of the member agencies. The policy sets forth essential requirements for the prevention and control of serious fish diseases, includes a system for inspecting and certifying fish hatcheries, and describes the technical pro- cedures to be used for inspection and diagnosis. Eight fish diseases are covered by the program. A fish disease control program should emphasize all aspects of good health, including infectious diseases, nutrition, physiology, and environ- ment. The program should not be an end in itself, but a means of provid- ing a quality product for fishery resource uses. The first step of any pro- gram must be the establishment of long-range goals. These goals may be FISH HEALTH MANAGEMENT 291 broad in concept or may dictate pathogen eradication. The latter is much more difficult to achieve, as it is possible to have disease control without pathogen eradication. Inspection, quarantine, and subsequent eradication are proven measures in livestock and poultry husbandry. After the goals of disease control have been established, it is necessary to design a policy that is compatible with other fishery resource priorities. The backbone of the policy should be a monitoring program that will determine the range of serious fish pathogens and detect new outbreaks of disease. Control and containment of fish diseases require the periodic ex- amination of hatchery populations as well as fish that are free-ranging in natural waters. Good health of hatchery fish extends beyond their cultural confinement to natural populations which they contact after being stocked. A monitoring program should include: (1) Fish health laboratories capable of following standardized procedures used to analyze fish specimens. These may include tests for disease agents, nutritional deficiencies, histology, tissue residues, etc. (2) A corps of competent, qualified individuals trained in inspection and laboratory procedures. (3) A training program in fish health for all persons involved in fish hus- bandry. (4) Agreements between various government agencies and private groups to establish lines of communication as well as the storage and cataloging of data derived from the monitoring program. (5) Specific guidelines for laboratory procedures to be followed and for qualifications of persons doing the inspections and testing. (6) The development of specific steps for disease reporting and of a cer- tification system. (7) Courses of action to control or eradicate a reportable disease when it occurs. With this in mind, the Fish and Wildlife Service established a policy for fish disease control and developed a plan to implement it. Basically, the plan is designed to classify, suppress, and eradicate certain serious diseases of salmonids present at facilities within the National Fish Hatchery System. As far as nonsalmonids are concerned, sampling for serious diseases is left to the discretion of Service biologists. Within the limits of existing techni- cal capabilities and knowledge, the plan provides for determining specific pathogen ranges within the National Fish Hatchery System, restricting dissemination of fish pathogens, and eradicating certain disease agents from federal fish hatcheries. The policy also provides a stimulus for research and training which should result in significant advances in technical knowledge concerning epizootiology, prevention, control, and diagnosis of various fish 292 FISH HATCHERY MANAGEMENT diseases. The Fish and Wildlife Service Disease Control Program serves as a model for other governmental agencies. During an on-site disease inspection at a hatchery, the fish health in- spector will collect random samples of fish tissue to be sent to a laboratory for analysis. The tests to be conducted will vary according to the type of certification requested and should follow the standardized procedures of the Fish Health Section of the American Fisheries Society (Procedures for the Detection and Identification of Fish Pathogens). The inspector takes tissues from a specified number of fish from each population at the hatchery. In most cases, each fish sampled must be killed. The minimum sample size from each population will follow a statist- ical plan that provides a 95% confidence for detecting a disease agent with an incidence of infection at or greater than 2 or 5% (Table 38). The sample sizes represent the minimum acceptable number. In situa- tions where the presence of a disease agent is suspected strongly, larger samples may be necessary and taken at the discretion of the inspector. The method of collecting subsamples from rearing units to obtain a representa- tive sample also is left to the inspector. For all fish except those being inspected for whirling disease, the sample population is determined on the basis of hatchery variables such as species, age, and water source. Generally, two egg shipments of fall- spawning rain- bow trout from the same hatchery received in September and December are considered as a single population; similarly, all spring-spawning rain- bow trout from the same source would be another population. However, Table 38. the minimum sample sizes for fish-disease inspections, accord- ing TO the number of fish in the population that will allow a disease TO BE detected IF IT OCCURS IN 2". OR 5"n OF THE POPULATION. SIZE OF SAMPLE POPULATION SIZE 2".. INCIDENCE 5% INCIDENCE 50 48 34 100 77 44 250 112 52 500 128 55 1,000 138 57 1,500 142 57 2,000 143 58 4,000 146 58 10,000 147 58 100,000 and larger 148 58 FISH HEALTH MANAGEMENT 293 when fish are held in different water supplies, each group has to be sam- pled as a separate population. All broodstock of the same species held in a single water supply can be considered one population. For a whirling disease inspection, each species of salmonid on the hatchery between 4 and 8 months old in a single water supply is a separate population. Example: A hatchery containing three species of trout between 4 and 8 months old with a single water supply has three sample popula- tions. Wild salmonid broodstocks must be inspected at least once during the period that eggs are being obtained for a National Fish Hatchery. All fish on hand at the time of inspection constitute the population and are sampled accordingly. Samples are collected from each tank or rearing unit. Suspect fish (moribund specimens) are collected along with healthy individuals. Fish should be alive when collected. Necropsy procedures as- sume that the same fish may provide tissues for the various laboratory tests (bacterial, viral, parasitic). A modified procedure may be required for very small fish. Material to be examined for external parasites must be taken before any antiseptic or disinfectant procedures are applied. After the body has been opened aseptically, tissues for bacterial cultures and virus tests are collected. Finally, cartilaginous organs (heads and gill arches) are taken for whirling disease examination. The samples are stored in sealed plastic bags and placed on wet ice for transfer to the laboratory. Protocol in the receiving laboratory must maintain the identity of all samples and preclude the dissemination of possible disease agents to other samples concurrently under examination. In addition, procedures must prevent contamination of the samples once the testing begins. At least 2 weeks are required for the laboratory analyses to be com- pleted. However, additional time may be required if any complications arise that cause some tests to be repeated or extended. Upon completion of the tests, a certifying official will issue a report specifying the samples taken, the laboratory tests conducted, and the findings. The exact type of report can vary according to the governmental agency involved and the cir- cumstances of the inspection. Based on results of the inspection, a certifi- cate of fish health may (or may not) be issued to the agency requesting the inspection. A copy must be given to the hatchery owner or manager. A fish-disease inspection often is trying to a hatchery manager. However, one must remember that the aim of issuing fish disease certificates is to im- prove success in combating diseases on a national scale. The spread of con- tagious diseases has occurred mainly through the uncontrolled transfer of live fish and eggs. In this connection, a clean bill of health helps not only to protect a hatchery owner from serious diseases that might be introduced by new shipments of fish or eggs, but also to assure that hatchery custo- mers receive a quality product. 294 FISH HATCHERY MANAGEMENT Diseases of Fish Viral Diseases INFECTIOUS PANCREATIC NECROSIS (IPN) Infectious pancreatic necrosis is a viral disease of salmonids found throughout the world. The disease is common in North America and has been spread to other countries, probably via contaminated egg and fish shipments. It has been reported in all species of trout and salmon. As a rule, susceptibility decreases with age. High losses occur in young finger- lings but few deaths or signs appear in fish longer than 6 inches. Some evi- dence suggests that well-fed, rapidly growing fish are more vulnerable to the disease than those less well- nourished. In an IPN epizootic, the first sign usually seen is a sudden increase in mortality. The largest and best appearing fingerlings typically are affected first. Spiraling along the long body axis is a common behavior of fish in lots having high death rates. The spiraling may vary from slow and feeble to rapid and frantic. Convulsive behavior may alternate with periods of quiescence during which victims may lie on the bottom and respire weakly. Death usually occurs shortly after the spiraling behavior develops. Signs include overall darkening of the body, protruding eyes, abdominal swelling, and (at times) hemorrhages in ventral areas including the bases of fins. Multiple petechiae occur in the pyloric caecal area, and the liver and spleen are pale in color. The digestive tract almost always is void of food and has a whitish appearance. Clear to milky mucoid material occurs in the stomach and anterior intestine and provides a key sign in the presumptive identification of IPN disease. Spiraling behavior, a mucus plug in the intes- tine, and a lack of active feeding strongly suggest IPN disease. However, a definitive diagnosis requires isolation and identification of the causal agent. This requires isolation of the virus in tissue culture combined with a serum neutralization test with specific immune serum. A positive diagnosis usually can be obtained within 24 to 48 hours in cases where large die-offs occur. Infectious pancreatic necrosis cannot be treated effectively and avoidance presents the only effective control measure. This consists of hatching and pro- pagating IPN virus-free fish stocks in uncontaminated water supplies. Care must be given to exclude sources of contamination such as egg cases, transport vehicles from other hatcheries, and eggs and fish from uncertified sources. Some hatcheries are forced to operate with water from sources containing IPN virus carriers. In these cases, extra eggs should be started to allow for high production losses. When an IPN outbreak occurs, strict sanitation can prevent the spread of the disease to fish in other holding units. If water is reused, susceptible fish elsewhere in the system usually will contract the in- fection. Survivors must be considered to be carriers of the virus. FISH HEALTH MANAGEMENT 295 VIRAL HEMORRHAGIC SEPTICEMIA (VHS) Viral hemorrhagic septicemia, also known as Egtved disease, has not been found in North America but is a serious hatchery problem in several Euro- pean countries. Epizootics have been reported in brown trout but VHS pri- marily is a disease of rainbow trout. It causes major losses among catchable or marketable trout but seldom is a problem among young fingerlings or broodfish. The disease spreads from fish to fish through the water supply. Over the years, the disease has been given numerous names by various German, French, and Danish workers. For simplification, the name Viral Hemorrhagic Septicemia has been recommended and the abbreviation VHS appears frequently in the literature. In North America, VHS is con- sidered an exotic disease that, if introduced, would cause severe problems in American culture of salmonids. Epizootics are characterized by a significant increase in mortality. Affect- ed fish become lethargic, swim listlessly, avoid water current, and seek the edges of the holding unit. Some individuals drop to the bottom and are re- luctant to swim even though they retain their normal upright position. Just prior to death, affected fish behave in a frenzied manner and often swim in tight circles along planes that vary from horizontal to vertical. Hyperactivi- ty may persist for a minute or more, then the fish drop motionless to the bottom. Most die, but others may resume a degree of normal activity for a short time. Affected trout generally do not eat, although a few fish in an infected population will feed. Trout with typical VHS become noticably darker as the disease progresses. Exophthalmia can develop to an extreme stage, and the orbit frequently becomes surrounded by hemorrhagic tissue. Such hemorrhaging is visible externally or may be seen during examination of the roof of the mouth. Characteristically, the gills are very pale and show focal hemor- rhages. On occasion, the base of ventral fins show hemorrhages. The dorsal fin may be eroded and thickened, but this also is a common feature among healthy rainbow trout under crowded conditions so its significance in VHS is not known. There is no food in the gastrointestinal tract and the liver is characteristically pale with hyperemic areas. Hemorrhages may occur throughout the visceral mass, especially around the pyloric caeca. The spleen becomes hyperemic and considerably swollen. One of the more com- mon signs is extensive hemorrhages in swim bladder tissue. Kidneys of af- fected fishes show a variable response. During the peak of acute epizootics, the kidneys usually have normal morphology but they may show hy- peremia. Occasionally, the kidneys become grossly swollen and posterior portions may show corrugation. It is not known whether this is a response to the virus or to other complicating factors. Body musculature also shows a variable response; in some fish it appears to be normal but in others 296 FISH HATCHERY MANAGEMENT petechiae may be present throughout the flesh. As with IPN virus, the causative agent of VHS must be identified by serological methods involv- ing cell cultures and immune serum specific for the virus. Fluorescent anti- body procedures also have been developed and work well. There is evidence that resistance increases with age. Infections usually are more severe in fingerlings and yearling fish, whereas fry and broodfish appear to be less susceptible. Brook trout, brown trout, and Atlantic sal- mon have been infected experimentally and grayling and whitefish were re- ported to be susceptible. Natural transmission occurs through the water, suggesting that virus is probably shed in feces or urine. There also is some evidence that the virus can occur on eggs. Survivors of an epizootic become carriers of the virus. This disease usually occurs during the winter and spring; as water tempera- tures rise, epizootics subside. Sporadic outbreaks may occur in the summer at water temperatures less than 68°F. Preventive measures against VHS in the United States consist largely of preventing the introduction of the virus through importation of infected eggs or fish. No salmonid eggs or fish may enter the United States legally unless they have been thoroughly inspected and found free of VHS. As in the case of other viral infections of fish, chemotherapy of VHS is unsuccessful. The only effective measure at present is avoidance, consisting of propagating clean fish in clean hatcheries and controlling the access of fish, personnel, animals, and equipment that might introduce the virus. INFECTIOUS HEMATOPOIETIC NECROSIS (IHN) Infectious hematopoietic necrosis, a viral disease of trout and salmon, first was recognized in 1967. Recent findings show that the pathogenic agent causing IHN disease is morphologically, serologically, physically, and biochemically indistinguishable from those implicated in viral diseases of sockeye and chinook salmon. Furthermore, clinical signs of the diseases and the histopathological lesions are the same. Thus the descriptive name infectious hematopoietic necrosis (IHN) disease has been given to all. Diseased fish are lethargic but, as in the case of many viral infections, some individuals will display sporadic whirling or other evidence of hy- peractivity. In chronic cases, abdominal swelling, exophthalmia, pale gills, hemorrhages at the base of fins, and dark coloration are typical signs of the disease. Internally, the liver, spleen, and kidneys usually are pale. The stomach may be filled with a milk-like fluid and the intestine with a watery, yellow fluid that sometimes includes blood. Pin-point hemorrhages throughout the visceral fat tissue and mesenteries often can be seen. In oc- casional cases, signs may be absent and fish die of no apparent cause. During the course of an epizootic, a generalized viremia occurs and the virus can be isolated from almost any tissue for diagnostic purposes. After FISH HEALTH MANAGEMENT 297 isolation, positive identification requires neutralization of the virus by a specific antiserum. Fish that survive an infection become carriers; both sexes shed the virus primarily with sex products. Gonadal fluids are used in bioassays to detect carrier populations. Natural transmission occurs from infected fish to noninfected fish through the water, or from the exposure of susceptible fry to sex products of carrier adult broodfish. The virus also can be transmit- ted with eggs or by the feeding of infected fish products. Only rainbow trout and chinook and sockeye salmon have been shown to be susceptible to IHN. Coho salmon apparently are resistant to the virus. Resistance increases with age and deaths are highest among young fry and fingerlings. However, natural outbreaks have occurred in fish rang- ing from yolk-sac fry to 2 years of age. The incubation and course of the disease are influenced strongly by water temperature. At 50°F, mortality may begin 4 to 6 days after exposure. Numbers of dead usually peak within 8 to 14 days, but mortality may continue for several weeks if the water temperature remains near 50°F. Below 50°F, the disease becomes pro- longed and chronic. Above 50°F, the incubation time is shorter and the disease may be acute. Some epizootics have been reported at temperatures above 59°F. Outbreaks of IHN disease have occurred along the Pacific Coast from the Sacramento River in California to Kodiak Island, Alaska. Although the virus may not exist in all populations of sockeye salmon, the virus has been detected in all major salmon production areas. Among chinook sal- mon, the disease is a particularly serious problem in the Sacramento River drainage; it has been found also in fish of the Columbia River. Outbreaks of IHN in rainbow trout have been much more restricted. Isolated hatcheries where carriers and outbreaks were identified are known from South Dakota, Minnesota, Montana, Idaho, Oregon, Washington, Colora- do, and West Virginia. All involved fish or eggs from a known carrier stock. However, there has been no recurrence of the disease at most of these hatcheries after the original outbreak. IHN also occurred in Japan in sockeye salmon from eggs transported from Alaska. An effective method of control is to maintain the water temperature above 59°F while fish are being reared. This principle has been used suc- cessfully to control IHN in chinook salmon along the Sacramento River. However, it is expensive to heat large volumes of water. Furthermore, rear- ing infected fish at elevated temperatures does not eliminate the carrier state. In rainbow trout, IHN virus is believed to be transmitted with eggs as a contaminate. Disinfection of eggs with iodophors usually will destroy the virus. 298 FISH HATCHERY MANAGEMENT CHANNEL CATFISH VIRUS DISEASE (CCV) In recent years, many outbreaks of channel catfish virus disease (CCV) have been reported in the United States, primarily from the major catfish- rearing region of the mid-South and Southeast. However, epizootics are not limited to these states and may occur anywhere channel catfish are cultured inten- sively if water temperatures are optimum for the virus. An outbreak in Cali- fornia led to a complete embargo on the shipment of catfish into that state. A sudden increase in morbidity usually is the first indication of CCV disease. The fish swim abnormally, often rotating about the long axis. This swimming pattern may become convulsive, after which the fish drop to the bottom and become quiescent. Just before death, affected fish tend to hang vertically with their heads at the water surface. This has been a characteris- tic behavioral sign associated with the disease. Any of the following signs may also be observed: hemorrhagic areas on the fins and abdomen and in the eye; distension of the abdomen due to fluid accumulation; pale or hemorrhagic gills; hemorrhagic areas in the musculature, liver, kidneys, and spleen; and a distended stomach filled with yellowish mucoid secre- tion. Definitive diagnosis requires the isolation and identification of the agent with specific immune antiserum. Catfish are the only known susceptible fish. Channel and blue catfish and hybrids between them have been infected experimentally with CCV. Young of the year are extremely vulnerable and losses of more than 90% are common. Age seems to provide some protection. Healthy catfish finger- lings have developed signs and died within 72 to 78 hours after exposure at water temperatures of 77°F and higher. In most cases, the disease can be linked to predisposing stress factors such as handling, low oxygen concen- trations, and coincident bacterial infections. Water temperatures (78°F or above) play an important part in the occurrence of the disease. At present, the only practical controls for channel catfish virus disease are avoidance, isolation, and sanitation. If the disease is diagnosed early, pond disinfection and destruction of infected fish may prevent the spread to other fish in ponds, troughs, or raceways. HERPESVIRUS DISEASE OF SALMONIDS The most recent virus to be isolated from cultured salmonids is the her- pesvirus disease. In the United States, broodstock rainbow trout in a western hatchery have been carriers. This is the only report to date in North America, but a similar, if not identical, agent has been the cause of natural epizootics occurring annually among fry of landlocked sockeye sal- mon in Japan. Recently, the virus was isolated from sick and dead adult landlocked sockeye salmon, also in Japan, but it yet remains to be deter- mined whether or not the virus was the cause of death. Experimentally, the virus has been lethal to rainbow trout fry and fingerlings. FISH HEALTH MANAGEMENT 299 Infected fry become lethargic; some swim erratically and are hyperactive, apparently losing motor control during the terminal stages. Exophthalmia is pronounced and abdominal darkening is common. Hemorrhage may be seen in the eyes of fish with exophthalmia. Abdominal distension is com- mon and gills are abnormally pale. Internally, ascitic fluid is abundant, and anemia and edema may be evi- dent in the visceral mass. The liver, spleen, and digestive tract are flaccid and the vascular organs are mottled with areas of hyperemia. The kidneys are pale, though not necessarily swollen. The digestive tract is void of food. Presently, specific immune antiserum has not been developed for defini- tive identification of the virus. Diagnosis, therefore, must be based on clini- cal signs of the disease, histopathological changes, and presumptive tests of the agent itself. This requires the services of a pathologist at a well- equipped laboratory. Fish- to- fish transmission is assumed, because the virus can be isolated from ovarian fluid, and eggs must be considered contaminated if they come from an infected source. Rainbow trout and landlocked sockeye salmon thus far are the only known susceptible species. Atlantic salmon, brown trout, and brook trout tested experimentally were refractory. Other species of salmon have not been tested. To date, reports of herpesvirus disease have been scattered and efforts should be made to prevent the spread of this potentially damaging disease. Avoidance is the only certain method of control. Chemotheraphy is ineffec- tive. LYMPHOCYSTIS DISEASE Lymphocystis disease, although rarely lethal, is of special interest because of its wide range of occurrence and presence in so many propagated and free-ranging fish species. Marine as well as freshwater fishes are suscepti- ble, but the disease has not been reported among salmonids. Among the propagated freshwater fishes, walleyes and most centrarchids are suscepti- ble. Lymphocystis is a chronic virus-caused disease causing generally granu- lar, wart- like or nodular tissue lesions composed of greatly enlarged host cells and their covering membrane. Cells of infected tissue may attain a size of a millimeter or more and resemble a spattering of sand-like granules or, when larger, a raspberry- like appearance (Figure 79). The causative agent of the disease is a virus maintained in susceptible host fishes. Healthy fish may be exposed when infected cells burst and the virus particles are released. This can occur intermittently through the dura- tion of infection, or it can be massive upon death and decomposition of in- fected fish. Lymphocystis lesions are persistent and commonly remain for several months; some may continue for a year or more. 300 FISH HATCHERY MANAGEMENT Figure 79. Lymphocystic virus disease. Note numerous "lymphocystic tumors" on skin of walleye. (Courtesy Gene Vaughan, National Fish Hatchery, Nashua, New Hampshire.) No method of treatment is known. Fish with the disease should be re- moved from the population to control the spread of the infection. Bacterial Diseases BACTERIAL GILL DISEASE Bacterial gill disease is a typical stress- mediated disease, and probably is the most common disease of cultured trout and salmon; it also is an occa- sional disease of warmwater and coolwater fish reared in ponds. Sudden lack of appetite, orientation in rows against the water current, lethargy, Figure 80. Furunculosis in brook trout. Note large furuncles on body surface of fish infected with Aeromonas salmonicida. (Courtesy National Fish Health Labora- tory, Leetown, West Virginia.) FISH HEALTH MANAGEMENT 301 flared opercula, riding high in water, and distribution of individuals equidistant from each other are typical signs of fish infected with bacterial gill disease. Gills show proliferation of the epithelium that may result in clubbing and fusing of lamellae or even filaments. Microscopic examina- tion of affected gill tissue reveals long, thin bacteria arranged in patches over the epithelium. Necrotic gill tissue may be visibly grayish-white and many of the filaments may be completely eroded. Often, only the gills on one side are affected. A combination of large numbers of bacteria and gill epithelial prolifera- tion differentiates bacterial gill disease from other gill problems. Etiology of the disease has not been proven conclusively because induction of the disease with flexibacteria isolated from diseased fish has not been con- sistently achieved. Other common soil and water bacteria, such as Aeromo- nas sp., also may cause bacterial gill disease. Crowding, mud and silt in the water supply, and dusty starter diets are important stress factors that contribute to outbreaks of the disease. Water temperatures above 56°F are favorable for the bacteria. Yearling and older fish are less susceptible than fry, but outbreaks can be acute in all ages of fish. Water supplies should be kept free of fish, silt, and mud. The accumula- tion of fish metabolic products due to crowding apparently is the most im- portant factor contributing to bacterial gill disease problems, and should be avoided. The most reliable and often- used treatments for bacterial gill disease are Roccal, Hyamine 1622 (98.8% active), and Hyamine 3500 (50% active). These treatments are not registered by the Food and Drug Administration. The effectiveness and toxicity of these compounds depends on water hard- ness and temperature, so caution must be used to prevent losses due to over- treatment and to insure that the treatment is effective. The recom- mended treatment level is 1 to 2 parts per million of active ingredient in water for 1 hour. Prophylactic treatments should be repeated every 7—14 days. If bacterial gill disease is diagnosed, treatment should be repeated daily for 3 to 4 days. Bacterial gill disease seldom is a problem among warmwater fish, partic- ularly those being reared in earthen ponds. It occasionally becomes a prob- lem when young channel catfish, largemouth bass, bluegills, or redear sunfish are held in crowded conditions in tanks or troughs for extended periods. This can be corrected by treating with 1-2 parts per million Roccal for 1 hour daily for 3 or 4 days or with 15-25 parts per million Terramycin for 24 hours. After the problem is under control, the fish popu- lation should be thinned or the water flow increased. Unless the manage- ment practice that precipitated the outbreak is corrected, bacterial gill disease will reappear. 302 FISH HATCHERY MANAGEMENT COLUMNARIS DISEASE The causative agent of columnaris disease historically has been named Chondrococcus columnaris, or Cytophaga columnaris, but now is classified as Flexibacter columnaris in Bergey's Manual of Determinative Bacteriology. The agents are long, thin, gram- negative bacteria that move in a creeping or flexing action, and that have a peculiar habit of stacking up to form dis- tinctive columns, hence the name "columnaris." Columnaris most commonly involves external infections but can occur as an internal systemic infection with no visible external signs. Externally, the disease starts as small, grayish lesions anywhere on the body or fins; most commonly the the lesions occur around the dorsal fin or on the belly. The le- sions rapidly increase in size and become irregular in shape. As the lesions get larger, the underlying musculature can be exposed. The margins of the lesions, and occasionally the centers, may have a yellowish color due to large aggregations of the bacteria. Frequently, lesions may be restricted to the head or mouth. In Pacific salmon and warmwater fish, particularly cat- fish, lesions may be confined to the gills. Lesions on the gills are character- ized by yellowish- brown necrotic tissue beginning at the tip of the fila- ments and progressing toward the base. Columnaris disease usually is associated with some kind of stress condi- tion such as high water temperature, low oxygen concentration, crowding, and handling. Under appropriate conditions, columnaris may take an ex- plosive course and cause catastrophic losses in 1 or 2 days after the first ap- pearance of the disease. Therefore, it is incumbent upon the fish culturist to maintain the best possible environmental conditions for the fish and to minimize any stress conditions. Although columnaris disease attacks practically all species of freshwater fish, catfish are particularly susceptible. In warmwater fish, most outbreaks of columnaris occur when the water temperature is above 68°F, but the disease can occur at any time of the year. Columnaris disease is common in salmonids held at water temperatures above 59°F. Progress of the disease usually is faster at the higher temperatures. Flexibacteria are common inhabitants of soil and water. They commonly are found on the surface of fishes, particularly on the gills. The stress of crowding, handling, spawning, or holding fish at above- normal tempera- tures, as well as the stress of external injury, facilitates the transmission and eruption of columnaris disease. Presumptive diagnosis of columnaris is accomplished best by microscopic examination of wet mounts of scrapings from lesions and detection of many long slender bacteria (0.5 x 10 micrometers) that move by flexing or creeping movements and form "haystacks" or "columns." Preventative measures include maintenance of optimum water tempera- tures for salmonids, reduced handling during warm weather, maintenance FISH HEALTH MANAGEMENT 303 of the best possible environmental conditions, and avoidance of overcrowd- ing fish. External infections of columnaris may be treated with: (1) Diquat (not registered by the Food and Drug Administration) at 8.4 to 16.8 parts per million (2-4 parts per million active cation) for 1 hour daily on 3 or 4 consecutive days. (2) Terramycin (registered by the Food and Drug Administration) as a prolonged bath at 15 parts per million active ingredient (0.57 gram per 10 gallons; 4.25 grams per 10 cubic feet) for 24 hours. (3) Furanace for trout and salmon (not registered by the Food and Drug Administration) as a bath at 1 part per million active ingredient (0.038 gram per 10 gallons; 0.283 gram per 10 cubic feet) for 5-10 minutes, or at 0.1 part per million active ingredient (0.0038 gram per 10 gallon; 0.0283 gram per 10 cubic feet) for an indefinite period. (4) Copper sulfate (registered by the Food and Drug Administration) at 0.5 part per million for pond treatments. (5) Potassium permanganate (registered by the Food and Drug Adminis- tration), the most effective pond treatment for external columnaris infec- tions in warmwater fish, at the rate of 2 parts per million (5.4 pounds per acre-foot). If the color changes in less than 12 hours it may be necessary to repeat the treatment. Internal infections of columnaris may be treated with Terramycin or sul- fonamides, both registered by the Food and Drug Administration. (1) For channel catfish and other warmwater fish that will take artificial food, provide medicated feed that will deliver 2.5-3.5 grams Terramycin per 100 pounds of fish per day for 7 to 10 days. For fish being fed 3% of their body weight daily, it is necessary to have 83.3-116.7 grams Terramy- cin per 100 pounds of food. Under no circumstances should the treatment time be less than 7 days. For salmonids, Terramycin given orally in the feed at a rate of 3.5 grams per 100 pounds fish per day for up to 10 days is very effective in early as well as advanced outbreaks. (2) For salmonids, sulfamerazine and sulfamethazine can be given orally in the feed at a rate of 5 to 10 grams per 100 pounds of fish per day, but they are less effective than other drugs. PEDUNCLE DISEASE Peduncle Disease is the same condition known as coldwater or low- temperature disease. Lesions appear on the fish in similar locations, system- ic flexibacteria are present, and the disease occurs at low water tempera- tures in the range of 45° to 50°F. Affected fish become darkened, and le- sions may develop on the caudal peduncle or on the isthmus anterior to 304 FISH HAICHERV MANAGEMENT the pectoral fins. The caudal fin may be completely destroyed. A peduncle disease lesion usually starts on the caudal peduncle behind the adipose fin, where it causes inflammation, swelling, and gradual erosion. The disease progresses posteriorly and the caudal fin may be eroded. Coho and chum salmon are the most susceptible and, in sac fry, the yolk sac may be ruptured. Peduncle disease or coldwater disease is caused by a flexibacterium, Cytophaga psychrophilia. The bacteria are water-borne and can be transmit- ted from carrier fish in the water supply. Crowded conditions stimulate a disease outbreak but are not necessary for the disease to appear. The best treatment for peduncle disease is the oral administration of drugs with food. Sulfasoxazole (Gantrisin) and sulfamethazine (not reg- istered by the Food and Drug Administration), at 9 grams per 100 pounds fish per day, or oxytetracycline (Terramycin), at 2.5 grams per 100 pounds of fish per day, should be given for 10-14 days. Chemotherapy combined with, or followed by, external disinfection with Roccal will give better and longer lasting results. FIN ROT Advanced cases of fin rot can resemble peduncle disease, but in this disease bacteria are found in fin lesions only and no specific type of bacterium is recognized as its cause. Signs may occur incidentally in the course of another bacterial disease, such as furunculosis. In typical fin rot, fins first become opaque at the margins and then lesions move progressively toward the base. Fins become thickened because of proliferation of tissue and, in advanced cases, may become so frayed that the rays protrude. The entire caudal fin may be lost, followed by a gradual erosion of the peduncle. Common water bacteria such as Aeromonas hydrophila and Pseudomonas sp. often are found in lesions of fin rot. Flexibacteria sometimes are mixed with other types of bacteria. The disease is associated with poor sanitary conditions that lead to fin abrasion, secondary bacterial infection, and fi- nally fin rot. The best results from treatments of fin rot infections are obtained with a soluble form of Terramycin added to water at 10 to 50 parts per million for 1 hour. Control also may be achieved with Hyamine or Roccal (not re- gistered by the Food and Drug Administration) in a concentration of 1 to 2 parts per million for 1 hour. FURUNCULOSIS Fish furunculosis, a septicemic disease principally of salmonids, has been known since 1894. It was first reported in the United States in 1902 and, since then, virtually all trout and salmon hatcheries have either been FISH HEALTH MANAGEMENT 305 contaminated with or exposed to the bacterium at one time or another. The causative agent of the disease is Aeromonas salmonicida. Today, furuncu- losis is enzootic in many hatcheries but severe outbreaks are rare due to advances in fish culture, sanitation, and drug therapy. Outbreaks have been reported among marine fishes. The disease is characterized by a generalized bacteremia with focal necrotic lesions in the muscle, often seen as swellings under the skin and not true furuncles (Figure 80). The swollen skin lesions are filled with pink fluid containing blood, and necrotic tissue may have a purple or irridescent blue color. These lesions are especially apparent in chronic infections but similar lesions may occur from other diseases caused by gram- negative bac- teria. Hemorrhaged fin sockets and frayed dorsal fins also are common. The disease frequently occurs as an acute form in which death results from massive bacteremia before gross lesions can develop. Only a few clini- cally sick fish may be seen at any one time in spite of the high death rate. Internally, diseased fish may exhibit small inflamed red lesions called petechiae in the lining of the body cavity and especially on the visceral fat. The pericardium usually is filled with bloody fluid and is inflamed. The spleen, normally dark red in color, often will be a bright cherry- red and swollen. The lower intestine often is highly inflamed and a bloody discharge can be manually pressed from the vent. A diagnosis of furunculosis can be either presumptive or confirmed. Presumptive diagnosis takes into consideration the frequency of outbreaks in a certain area, presence of typical lesions, and the occurrence of short gram-negative rods in the lesions, kidneys, spleen, and blood. Confirmation of a presumptive diagnosis can be made only after Aeromonas salmonicida has been identified as the predominant organism isolated. Furunculosis is endemic in many hatcheries and is so widespread that no natural waters with resident fish populations should be considered free of this disease. The incidence pattern of furunculosis generally follows the seasonal temperature pattern. Almost twice as many cases are reported in July as in any other month. The number of cases drops sharply in August, possibly indicating increased resistance in the remaining fish population or death of most of the susceptible fish. Acute cases of furunculosis have incubation periods of 2-4 days with few apparent signs. Chronic cases usually occur at temperatures below 55°F and may have an incubation period of one to several weeks, depending upon the water temperature. Latent cases may develop during low- temperature periods, and flare up with greater severity, displaying many typical signs, when water temperatures rise. Fish exposed to furunculosis form protective antibodies. Some fish be- come immune carriers of the disease. Suckers and other nongame fish in the water supply may become infected and should be considered likely 306 FISH HATCHERY MANAGEMENT reservoirs of infection. Furunculosis may break out in virtually any fresh- water fish population, including warmwater species, if conditions such as high temperature and low dissolved oxygen favor the pathogen. Among the eastern salmonids, brook trout are the most susceptible to in- fection, brown trout are intermediate, and rainbow trout are least suscepti- ble. Atlantic salmon also are susceptible. Furunculosis has been reported in most of the western salmonids. In addition to salmonids, the disease has been reported in many other fishes, including sea lamprey, yellow perch, common carp, catfish, northern pike, sculpins, goldfish, whitefish, and vari- ous aquarium fishes. Sanitation provides the most important long-range control of furuncu- losis. If a population of trout at a hatchery is free of furunculosis and if the water supply does not contain fish that harbor the pathogen, strict sanita- tion measures should be used to prevent the introduction of the disease via incoming eggs or fish. Eggs received at a hatchery should be disinfected upon arrival. lodophors used as recommended are not toxic to eyed eggs but are highly toxic to fry. Maintenance of favorable environmental conditions for the fish is of prime importance in preventing furunculosis outbreaks. Proper water tem- peratures, adequate dissolved oxygen, efficient waste removal, and avoidance of overcrowding must be observed. In areas where the disease is endemic, strains of trout resistant to furunculosis are recommended. How- ever, regardless of the trout strain involved, acute outbreaks of furunculosis have occurred when conditions favored the disease. Sulfamerazine (lO grams per 100 pounds of fish per day) in the diet has been the standard treatment of furunculosis for years. In recent years, be- cause of sulfa-resistant strains of A. salmonicida, Terramycin (3.6 grams TM-50 or TM-50D per 100 pounds of fish per day for 10 days) has be- come the drug of choice. Furazolidone (not registered by the Food and Drug Administration) has been used successfully under experimental con- ditions against resistant isolates of the bacterium. Furox 50 (also not reg- istered) at 5 grams active ingredient per 100 pounds fish per day has been used successfully under production conditions with Pacific salmon. Drugs are effective only in the treatment of outbreaks. Recurrences of furuncu- losis are likely as long as A. salmonicida is present in the hatchery system and environmental conditions are suitable. ENTERIC REDMOUTH (ERM) Enteric Redmouth disease refers to an infection of trout caused by an enteric bacterium, Yersinia ruckeri. Initially, the disease was called Redmouth; later the name Hagerman redmouth disease (HRM) was used to differentiate between infections caused by Yersinia and those caused by the bacterium FISH HEALTH MANAGEMENT 307 Aeromonas hydrophila. Presently, the Fish Health Section of the American Fisheries Society recommends the name Enteric Redmouth. Enteric red- mouth disease occurs in salmonids throughout Canada and much of the United States. Outbreaks in Pennsylvania trout and in Maine Atlantic sal- mon are among the most recent additions to its geographical range. The gram- negative Yersinia ruckeri produce systemic infections that result in nonspecific signs and pathological changes. The diagnosis of infections can be determined only by isolation and identification of the bacterium. Enteric redmouth disease is characterized by inflammation and erosion of the jaws and palate of salmonids. Trout with ERM typically become sluggish, dark in color, and show inflammation of the mouth, opercula, isthmus, and base of fins. Reddening occurs in body fat, and in the posteri- or part of the intestine. The stomach may become filled with a colorless watery liquid and the intestine with a yellow fluid (Figure 8l). This disease often produces sustained low-level mortality, but can cause large losses. Large-scale epizootics occur if chronically infected fish are stressed during hauling, or exposed to low dissolved oxygen or other poor environmental conditions. The disease has been reported in rainbow trout and steelhead, cutthroat trout, and coho, chinook, and Atlantic salmon. The bacterium was isolated first in 1950, from rainbow trout in the Hagerman Valley, Idaho. Evidence suggests that the spread of the disease is associated with the movement of infected fish to uncontaminated waters. Fish-to-fish contact provides transfer of the bacterium to healthy trout. Because spread of the disease can be linked with fish movements, the best control is avoidance of the pathogen. Fish and eggs should be obtained only from sources known to be free of ERM contamination. This can be accom- plished by strict sanitary procedures and avoidance of carrier fish. Recent breakthroughs in the possible control of ERM by immunization have provided feasible economic procedures for raising trout in waters con- taining the bacterium. Bacterins on the market can be administered effi- ciently to fry for long-term protection. A combination of drugs sometimes is required to check mortality during an outbreak. One such combination is sulfamerazine at 6.6 grams per 100 pounds fish plus NF-180 (not registered by the Food and Drug Adminis- tration) at 4.4 grams per 100 pounds fish, fed daily for 5 days. MOTILE AEROMONAS SEPTICEMIA (MAS) Motile aeromonas septicemia is a ubiquitous disease of many freshwater fish species. It is caused by gram- negative motile bacteria belonging to the genera Aeromonas and Pseudomanas. Two species frequently isolated in out- breaks are A. hydrophila and P. fluorescens. A definitive diagnosis of MAS 308 FISH HATCHKRY MANAGEMENT Figure 81. Enteric red mouth disease in a rainbow trout. Note hemorrhaging in eye and multiple petechial hemorrhages in liver. The spleen is swollen and a yel- lowish mucoid plug has been pushed from the intestine. Judged by the pale gills and watery blood in the body cavity, this fish was anemic. (Courtesy Charlie E. Smith, FWS, Bozeman, Montana.) can be made only if the causative agent is isolated and identified. A tenta- tive diagnosis based only on visible signs can be confused with other simi- lar diseases (Figure 82). When present, the most common signs of MAS are superficial circular or irregular grayish-red ulcerations, with inflammation and erosion in and Figure H2. Bacterial septicemia on a goldfish, caused by an infection with Aero- monas hydrophila. (Courtesy National Fish Health Laboratory, Leewtown, West Virginia. FISH HF.ALTH MANAGEMENT 309 around the mouth as in enteric redmouth disease. Fish may have a distend- ed abdomen filled with a slightly opaque or bloody fluid (dropsy) or pro- truding eyes (exophthalmia) if fluid accumulates behind the eyeball. Other fish, minnows in particular, may have furuncules like those in furunculosis, which may erupt to the surface, producing deep necrotic craters. Fins also may be inflamed (Figure 83). In addition to the presence of fluid in the abdominal cavity, the kidney may be swollen and soft and the liver may become pale or greenish. Petechiae may be present in the peritoneum and musculature. The lower intestine and vent often are swollen and inflamed and may contain bloody contents or discharge. The intestine usually is free of food, but may be filled with a yellow mucus. Motile aeromonas septicemia occasionally takes an acute form in warm- water fish and severe losses can occur even though fish show few, if any, clinical signs of the disease. In general, most outbreaks in warmwater fish occur in the spring and summer but the disease may occur at any time of year. Largemouth bass and channel catfish are susceptible particularly dur- ing spawning and during the summer if stressed by handling, crowding, or low oxygen concentrations. Aquarium fish can develop the disease at any time of the year. Among salmonids, rainbow trout seem to be the most sus- ceptible and outbreaks are associated with handling stress and crowding of Figure 83. Severe bacterial septicemia in a channel catiish infected vvith an unknown enteric bacterium. (Courtesy National Fish Health Laboratory, Lee- town, West Virginia.) 310 FISH HATCHERY MANAGEMENT Figure 84. Grayish-white necrotic lesions in the kidney of a rainbow trout with bacterial kidney disease. (Courtesy National Fish Health Laboratory, Leetown, West Virginia.) fish. Fish and frogs that recover from the disease usually become carriers and may contaminate water supplies if they are not destroyed. The disease has been identified throughout the world and apparently infects any species of freshwater fish under conditions favoring the bacteria. Observation of strict sanitary practices and the elimination of possible carrier fish from the water supply are extremely important to the control of bacterial hemmorhagic septicemia on trout and salmon hatcheries. For warmwater fish, everything possible should be done to avoid stressing the fish during warm weather. As a prophylactic measure, broodfish can be in- jected with 25 milligrams active Terramycin per pound of body weight or fed medicated feed before they are handled in the spring. Outbreaks of MAS in channel catfish and other warmwater fish that will eat artificial food can be treated by feeding them 2.5-3.5 grams active Ter- ramycin per 100 pounds of fish for 7-10 days. Outbreaks in salmonids have been treated successfully by Terramycin fed at 3.6 grams TM-50 per 100 pounds of fish daily for 10 days. Sulfam- erazine fed at 10 grams per 100 pounds of fish per day for 10 days also has been used with reasonable success. A combination of sulfamerazine and NF-180 Inot registered by the Food and Drug Administration) has been very effective in treating outbreaks on trout hatcheries in the western United States. VIBRIOSIS Vibriosis is a common systemic disease of marine, estuarine, and (occasion- ally) freshwater fishes. It is known also under the names of red pest, red FISH HEALTH MANAGEMENT 31 1 boil, red plague, or salt water furunculosis. Vibrio anguillarum is now con- sidered to be the etiologic agent of the disease. Although vibriosis generally is a disease of cultured marine fishes, it also occurs in wild populations. It can occur any time of year, even in water temperatures as low as 39°F. However, it is most prevalent in the temperate zones during the warmer summer months and epizootics can be expected when water temperatures reach 57°F. Signs of the disease usually do not become evident until the fish have been in salt water for two weeks or more under crowded conditions. Di- minished feeding activity is one of the first noticeable signs. Lethargic fish gather around the edges of holding units; others swim in erratic, spinning patterns. Diseased fish have hemorrhages around the bases of their pectoral and anal fins or a bloody discharge from the vent. When a fish is opened for necropsy, diffuse pin-point hemorrhages of the intestinal wall and liver may be evident. The spleen frequently is enlarged and may be two to three times its normal size. Diagnosis of vibriosis caused by V. anguillarum requires isolation of a gram- negative, motile, rod-shaped bacterium on salt medium. The organ- ism may be slightly curved and produces certain biochemical reactions under artificial culture. There is no reliable presumptive diagnosis of vi- briosis because of its similarity to other septicemic diseases caused by gram- negative bacteria. The organism is ubiquitous in marine and brackish waters and infections probably are water-borne and may be spread by contact. Salmonids usually die within 1 week after exposure; fish of all ages are susceptible. Vibriosis is worldwide in its distribution, but it usually is most severe in mariculture operations. Virtually all species of marine and estuarine fishes are susceptible. Among salmonids, pink salmon and chum salmon are the most susceptible but serious epizootics have occurred in coho salmon, rain- bow trout, and Atlantic salmon. Stresses associated with handling, low oxy- gen, and elevated temperature predispose fish to vibriosis. Prevention of vibriosis depends on good sanitation, no crowding, and minimal handling stress. Immunization is an effective means of combatting the disease. Bacterins now are available from commercial sources and ap- pear to provide long-term protection. Hyperosmotic procedures utilizing bacterins appear most suitable for large numbers of small fingerlings. Injec- tions may be preferable for larger fish. In theory, long-term selection and breeding for resistance to the bacterium may be a means of control. Sulfamerazine (registered by the Food and Drug Administration) used at the rate of 17 grams per 100 pounds of fish per day for 10 days has con- trolled vibriosis. Terramycin (also registered) at 5.0 to 7.5 grams per 100 pounds of fish per day for 10 days also has been successful. 312 FISH HAICHERV MANAGEMENT KIDNEY DISEASE Kidney disease is a chronic insidious infection of salmonid fishes. The disease is slow to develop but, once established, it may be difficult to con- trol and virtually impossible to cure. The causative bacterium of kidney disease (Renibacterium salmoninarum) is a small, non-motile, nonacid-fast, gram-positive diplobacillus. The course of kidney disease is similar to that of a chronic bacteremia. Once the pathogen enters the fish via infected food, or from contact with other infected fish in the water supply, the bacteria multiply slowly in the blood stream. Foci of infection develop in the kidney and in other organs such as the liver, spleen, and heart (Figure 84). White cellular debris col- lects in blisters and ulcers that develop in these organs are seen easily. Le- sions developing in the posterior kidney are easiest to spot and may reach a centimeter or more in diameter. Some lesions extend into the muscula- ture and result in externally visible blisters under the skin. If the disease has reached the stage in which gross lesions are apparent, therapeutic treat- ment has little effect (Figure 85). At best, drug therapy will only cure light- ly or newly infected fish. This difficulty in the control of kidney disease is the basis for classifying it as a reportable disease. Although kidney disease first was reported in the United States in 1935, a similar, and probably identical, condition termed "Dee disease" was re- ported in Scotland in 1933. The disease has been found in 16 species of salmonids in North America. A tendency towards seasonal periodicity has been noted, but the incidence varies at different hatcheries. Chinook, coho, sockeye, and Atlantic salmon and brook trout are highly susceptible, but the disease is not known among nonsalmonids. Infected or carrier fish are considered to be sources of infection. Experi- mentally, from 1 to 3 months have elapsed before mortality began. Historically, diagnosis of kidney disease epizootics has been based on the demonstration of small, gram- positive diplobacilli in infected tissues. How- ever, the accuracy of such identifications is uncertain and more reliable serological procedures such as fluorescent antibody techniques should be used. Until the sources and modes of infection in hatcheries are known, strict quarantine and antiseptic disposal of infected fish are recommended. lodo- phor disinfection of salmonid eggs may be of benefit in preventing transmission of the organism with eggs, but it is not completely effective. Under laboratory conditions, erythromycin (not registered by the Food and Drug Administration) given orally at the rate of 4.5 grams per 100 pounds of fish per day for three weeks gave the best control but was not completely effective. Treatments under field conditions have given similar results; cures were effected in some lots, but among others the disease IMl llKAl.lll MANAGEMENT 313 FiGL RE 85. External lesions in trout infected u ith corynebacterial kidney disease. (Courtesy National Fish Health Laboratory, Leetown, West Virginia.) recurred. All published accounts of treatment with sulfonamides report that mortality from the infection recurred after treatment ceased. Sulfametha- zine (registered by the Food and Drug Administration) fed at 2.0 grams per 100 pounds of fish per day has been successfully used for prophylaxis in Pacific salmon. To date, no sulfonamide-resistant strains of the kidney disease bacterium have been reported. Figure 86. Smallmouth bass with severe external fungus infection. (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkansas.) 314 FISH HATCHERY MANAGEMENT Fungus Diseases Fungi are encountered by all freshwater fishes at one time or another dur- ing their lives. Under cultural conditions, certain fungi can be particularly troublesome. Species of the family Saprolegniaceae commonly are implicat- ed in fungal diseases of fish and fish eggs. Species of Saprolegnia, Achlya, Aphanomyces, Leptomitus, Phoma, and Pythium have been reported as patho- gens. Fungae infestating fish or eggs generally are considered to be secon- dary invaders following injury but, once they start growing on a fish, the lesions usually continue to enlarge and may cause death. Fungi often at- tack dead fish eggs and spread to adjacent live eggs, killing them. These fungi grow on many types of decaying organic matter and are widespread in nature. The presence of fungal infections on fish or fish eggs is noted by a white cottony growth. This growth consists of a mass of filaments; these contain the flagellated zoospores that escape to begin infections on other fish or eggs. Unless control measures are taken, the expanding growth ultimately may cover every egg in the incubator. Injuries to fish produced by spawning activity or other trauma, and le- sions caused by other infections, often are attacked by fungus. Holding warmwater fish in cold water during summer can render fish more suscepti- ble to fungal infections (Figure 86). Good sanitation and cleanliness are absolutely essential to effective con- trol of fungi and other parasites under intensive culture conditions. For the control of fungal infections on eggs, there are two methods, one mechanical, the other chemical. The mechanical method is used for controlling fungal infections on both salmonid and catfish eggs, and involves picking dead and infected eggs at frequent intervals during incubation. This, however, is time-consuming and some healthy eggs may be injured in the process. Good chemical control of fungal infections on eggs can be achieved. For- malin at 1,600 and 2,000 parts per million for 15 minutes will control fungus on both salmonid and catfish eggs. Do not expose fry to these con- centrations of formalin. In Europe, gill rot, a disease caused by fungi of the genus Branchiomyces, is considered one of the greatest threats to fish culture. Although European gill rot is primarily a disease of pike, tench, and carp it has been found in rainbow trout, largemouth bass, smallmouth bass, striped bass, northern pike, pumpkinseed, and guppies in the United States. This disease has been found in Alabama, Arkansas, Florida, Georgia, Missouri, Ohio, Rhode Island, and Wisconsin. Clinical signs associated with branchiomycosis include pale, whitish gills with necrotic areas, fish gasping at surface, and high losses. A presumptive diagnosis can be made by microscopic examination of FISH HEALTH MANAGEMENT 315 wet gill tissue (lOO x or 440 x) if nonseptate hyphae and spores of the fungus are seen in the capillaries and tissue of the gill lamellae. Suspect material should be sent for a confirmatory diagnosis. Suspect fish should be held under strict quarantine until the diagnosis is confirmed. There is no control for branchiomycosis except destruction of infected fish and decontamination of facilities. Protozoan Diseases Protozoans probably cause more disease problems in fish culture than any other type of fish pathogen. Fish reared under intensive conditions rarely are without some parasites. It is common to find protozoans of many taxo- nomic classes in or on wild fish. When present in small numbers, they usu- ally produce no obvious damage; in large numbers they can impair the ep- ithelium and actually feed on the cells and mucus of the fish. To discuss each protozoan and parasite of fish in this text would be a lengthy task. Therefore, only those of major importance to fish husbandry are presented. For those who wish additional details, a search of the literature will reveal many comprehensive works. Hoffman's Parasites of North American Freshwa- ter Fishes (1967), is an excellent source with which to begin. External Protozoan Diseases ICHTYOBODO Species of Ichtyobodo (Costia) are very small flagellated ectoparasites easily missed during routine microscopic examinations of gills and body scrap- ings. These protozoans are free- swimming, move by means of long flagella, and are about 5 by 12 micrometers in size — about the size of a red blood cell (Figure 87). Two species, /. pyriformis and /. necatrix, are commonly seen and produce "blue slime" disease of fish. The characteristic blue slime or bluish sheen taken on by fish is caused by increased mucus production in response to irritation. An early sign of an Ichtyobodo infection is a drop in appetite of the fish and a general listlessness. "Flashing" may be evident if the skin is infected, but only rarely if just the gills are involved. Signs of the disease sometimes are mistaken for bacterial gill disease. Heavily infected fish often develop a bluish slime over the entire body (Figure 88); however, fish less than 3 or 4 months old usually will die before this condition develops. 316 FISH HATCHERY MANAGEMENT Figure 87. hhtyobodo (Costia), 400x magnification. (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkan- sas.) Ichtyobodo can be a serious problem on all species and sizes of warmwater fish, particularly channel catfish. This flagellate can cause problems any- time of year, but is most common on warmwater fish from February to April. Pond treatments for Ichtyobodo that give good results, if they can be used in the particular situation, include: formalin at 15-25 parts per million; po- tassium permanganate at 2 parts per million (may have to be repeated depending on organic load in the pond); or copper sulfate at whatever concentration can be used safely. For a prolonged bath treatment for salmonids or warmwater fish, best results are obtained from formalin at 125 to 250 parts per million for up to 1 hour; the concentration depends on water temperature and species and size of fish to be treated. ICHTHYOPHTHIRIUS Ichthyophthirius multifilis, or "Ich," is a large ciliated protozoan exclusively parasitic on fish. It probably is the most serious disease of catfish, but also is a common parasite of other warmwater fishes and can be a serious prob- lem of salmonids. Ich is the only protozoan parasite that can be seen by the naked eye; when fully grown it may be as large as 1.0 millimeter in di- ameter and appear as gray-white pustules much like grains of salt. Positive identification is based on the finding of a large, ciliated protozoan with a horseshoe- shaped macronucleus embedded in gills, skin, or fin tissue. The feeding stages, or trophozoites, of Ich are found in the epithelium of the skin, fins, and gills (Figures 89 and 90). When mature, the adult parasites drop off the host and attach to the bottom or sides of the pond. Once encysted, they reproduce by multiple fission and, within two to FISH HEALTH MANAGEMENT 317 Figure 88. Ichtyobodo (Costia) infection on a rainbow trout (blue slime disease). (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkansas.) several days, depending upon temperature, each adult may produce up to 1,000 ciliated tomites. The tomites burst from the cysts and must find a fish host within about 24 hours or die. Upon contact with the fish, the tomites penetrate the skin and begin to feed and grow into adults. At op- timal temperatures of 70 to 75°F, the life cycle may take as few as 3 to 4 days. The cycle requires 2 weeks at 60°F, more than 5 weeks at 50°F, and months at lower temperatures. Ich is known as "salt and pepper" and "white spot" disease by aquarists because of the gray-white specks that appear on the skin. However, on some species of warmwater fish, mainly the golden shiner, Ich is found al- most exclusively on the gills. On rare occasions, Ich infections on catfish also may be restricted to the gills. In severe outbreaks, losses may precede Figure 89. Severe Ichthyopthirius infection (white spots) in the skin of an Ameri- can eel. (Courtesy National Fish Health Laboratory, Leetown, West Virginia.) 318 FISH HATCHERY MANAGEMENT Figure 90. Ichthyophthirius on a rainbow trout fin, 6x magnification. (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Arkansas.) the appearance of the mature parasites on the fish. Young fish exhibit con- siderable flashing off the bottom and often show erratic spurts of activity, jumping out of the water and thrashing about, due to irritation caused by the parasites. Successful treatment of Ich depends upon the elimination of parasite stages that are free in the water and the prevention of re-infection. Tomites and adult parasites leaving the fish are, therefore, the target of therapeutic efforts. The best control for Ich, as for any disease, is prevention. Hatchery wa- ter supplies always should be kept free of fish. If possible, any warmwater fish brought onto a hatchery should be quarantined for at least one week at 70°F, and coldwater fish for at least 2 weeks at 60°F, to determine if they i are infested with Ich. Ich is difficult to treat because the tissue- inhabiting and encysted forms are resistant to treatment; only the free-swiming forms are vulnerable. Suc- cessful treatment usually is long and expensive. There are several pond treatments for either warmwater fish or salmonids that can be used success- fully if started in time. Copper sulfate can be used at whatever concentra- tion is safe in the existing water chemistry. Treatment is repeated on alter- nate days; usually from two to four applications are necessary, depending on water temperature. This is the least expensive treatment and gives good FISH HEALTH MANAGEMENT 319 results on catfish when it can be used safely. Potassium permanganate sometimes is used at 2 parts per million and repeated on alternate days for two to four applications. Success is not always good. Formalin at 15-25 parts per million can be used on alternate days for two to four applications. The higher concentration gives the best results. This is a very effective treatment but is expensive for treating large volumes of water. Prolonged bath or flush treatments can also be used to treat Ich on fish being held in tanks, raceways, or troughs. Formalin is effective at 167-250 parts per million, depending on water temperature and species and size of fish, for up to 1 hour daily or on alternate days. The number of treatments required depends on the water temperature. CHILODONELLA Species of Chilodonella are small, oval, colorless protozoans, 50-70 microme- ters long, which may be found in vast numbers on the skin, fins, and gills of goldfish, other warmwater species, and salmonids. Under high magnifi- cation, faint bands of cilia can be seen over much of the organism (Figure 91). Their optimal water temperature is 40 to 50°F, making it particularly troublesome on warmwater species during cold weather. Heavily infected fish are listless, do not feed actively, and may flash. Chilodonella is con- trolled easily with any of the following treatments for external protozoan parasites: (1) Formalin at 125-250 parts per million for 1 hour in tanks or racesays. (2) Formalin at 15-25 parts per million as an indefinite treatment in ponds. (3) Copper sulfate at whatever concentration can be used safely in the existing water chemistry as an indefinite treatment in ponds. (4) Potassium permanganate at 2 parts per million as an indefinite treat- ment in ponds. The treatment may have to be repeated if heavy organic loads are present. EPISTYLIS Species of Epistylis grow in clumps at the ends of bifurcate, noncontractile stalks (Figures 92 and 93). Under the microscope they appear much like a cluster of bluebells growing on a stalk that is attached to the fish by a disc. They commonly are found on the skin but also may occur on gills and incu- bating eggs. Flashing actions by the fish during the late morning and late evening hours are among the first signs of infestations. Some species of Epi- stylis evidently cause little tissue damage but other strains cause extensive cutaneous lesions. Epistylis should be removed when it causes severe flash- ing or skin lesions that may serve as openings for fungal or bacterial infec- tions. Epistylis can be extremely difficult to control on warmwater 320 FISH HATCHERY MANAGEMENT Figure 91. Chilodonella, 475 x magnification. (Cour- tesy G. L. Hoffman, Fish Farming Experimental Sta- tion, Stuttgart, Arkansas.) fish, particularly channel catfish. Epistylis on salmonids can be controlled with one treatment of 167 parts per million formalin for 1 hour if the water temperature is 55°F or higher, or with 250 parts per million formalin for 1 hour repeated twice, if the water temperature is 45°F or lower. For warm- water fish the following treatments have been used: (1) Salt (NaCl) at 0.1-1.5% for 3 hours is the best for controlling Epistylis on channel catfish. This is suitable only for raceway, tank, or trough treat- ments, not for ponds. (2) In ponds, use formalin at 15-25 parts per million or potassium per- manganate at 2 parts per million. These treatments usually must be repeated two to three times to achieve an effective control. TRICHODINA Trichodinids are saucer-shap>ed protozoans with ciUa around the margin of the body as they normally are viewed under the microscop>e. These protozoans live on the skin, fins, and gills of fish and, when abundant, cause severe irritation and continual flashing. Salmon yearlings, if left untreated, develop a tattered appear- ance. Secondary bacterial infections may develop in untreated cases. FISH HEALTH MANAGEMENT 321 Trichodina on warmwater fish can be controlled with any of the following treatments: (1) Copper sulfate as an indefinite pond treatment at whatever concen- tration can be used safely in the existing water chemistry. (2) Potassium permanganate at 2 parts per million as an indefinite pond treatment. (3) Formalin at 15-25 parts per million as an indefinite pond treatment. (4) Formalin at 125-250 parts per million, depending on water tempera- ture and species and size of fish, for up to 1 hour. To control Trichodina on salmonids, formalin at 167-250 parts per mil- lion for up to 1 hour usually is successful. If salmonids are sensitive to for- malin, a 2-4 parts per million treatment of Diquat for one hour should be tested. AMBIPHRYA Ambiphrya (Scyphidia) can occur in large numbers on the skin, fins, and gills of freshwater fish. The organism has a barrel-shaped body with a band of cilia around the unattached end and around the middle of the body, and a ribbon-shaped Figure 92. Epistylis, lOOx magnification. (Courtesy G. H. Hoffman, Fish Farm- ing Experimental Station, Stuttgart, Arkansas.) 322 FISH HATCHERY MANAGEMENT Figure 93. Epistylis sp., living colony from rainbow trout, 690x magnification. (Courtesy Charlie E. Smith, FWS, Bozeman, Montana.) Figure 94. Trichophyra sp. on gills of rainbow trout. Note extended food gather- ing tentacles, 300x magnification. (Courtesy Charlie E. Smith, FWS, Bozeman, Montana.) FISH HEALTH MANAGEMENT 323 macronucleus. They can be especially troublesome on young catfish, cen- trarchids, and goldfish. Ambiphrya can cause problems anytime of year but most frequently occurs when water quality deteriorates due to excessive amounts of organic matter or low oxygen levels. This protozoan is not a parasite. It feeds on bacteria and detritus and may develop in high numbers. Heavy infestations on the gills cause the fish to act as if they were suffering from an oxygen deficiency. Large numbers of them can cause a reddening of the skin and fins. Fry and small fish may refuse to feed actively, flash, and become listless. Ambiphrya is controlled easily with formalin at 125-250 parts per million for up to 1 hour, or 15-25 parts per million as a pond treatment. Copper sulfate, at whatever concentration can be used safely, or potassium perman- ganate at 2 parts per million, also give good results. TRICHOPHRYA Species of Trichophrya sometimes are found on the gills of fish and can cause serious problems in catfish and occasionally in other warmwater species. They have rounded to pyramid-shaped bodies (30 x 50 microme- ters) and are distinguished by food-catching tentacles in the adult stage (Figure 94). Live organisms have a characteristic yellowish-orange or yellowish- brown color that makes them very conspicuous when wet mounts of gill tissue are examined under a microscope at lOOx or 440 x. Affected fish gills are pale and clubbed, and may be eroded. Infected fish will be listless, as if they were suffering from an oxygen deficiency. Trichophrya is difficult to control in ponds but satisfactory results can be obtained with copper sulfate at whatever concentration is safe. Pond treat- ments with formalin or potassium permanganate give erratic results. A bath treatment of 125-250 parts per million formalin for up to 1 hour usually is effective, but may have to be repeated the next day. Internal Protozoan Diseases HEXAMITA Hexamita salmonis is the only common flagellated protozoan found in the intestine of trout and salmon. Although the pathogenicity of the organism is questioned by some researchers, most feel it can cause poor growth and elevated mortality in small (2-inch) fish. All species of salmonids are sus- ceptible to infection. Because there are no well-defined signs, a diagnosis of 324 FISH HATCHERY MANAGEMENT Figure 95. Hexamita salmonis. Figure 96. Henneguya sp. hexamitiasis must be made by microscopic examination of gut contents from the anterior portion of the intestine and pyloric caeca. The flagellates (Figure 95) are minute, colorless, pear-shaped organisms that dart rapidly in every direction. Gross signs of infected fish may include swimming in a cork-screw pattern, and a dark emaciated condition commonly called "pin- headed." The protozoan may become abundant in fish that are fed meat diets, and can cause irritation of the gut lining. With the advent of processed diets, incidence of the disease has greatly declined. Therapy is not recommended unless Hexamita salmonis is abundant. For treatment, feed epsom salt (magnesium sulfate) at the rate of S'/o of the diet for 2 or 3 days. HENNEGUYA Seventeen species of Henneguya have been described from a wide variety of North American freshwater fishes. The following remarks are limited to the relationship of these parasites to hatchery-reared species, primarily channel catfish. FISH HEALTH MANAGEMENT 325 All species of Henneguya are histozoic and localize in specific tissues. In- fections may appear as white cysts within the gills, barbels, adipose fins, skin, gall bladder, connective tissue of the head, subcutaneous tissues, or sclera and muscles of the eye. Spores of Henneguya grossly resemble spermatoza; they possess two ante- rior polar capsules and an elongate posterior process (Figure 96) that may or may not separate along the sutural plane. The mode of transmission is believed to be fish-to-fish; no methods of chemical control are known. Henneguya salminicola has been found in cysts in the body or musculature of coho, pink, and chinook salmon. Chum salmon also are subject to infection. In channel catfish, Henneguya infections are categorized with respect to the tissue parasitized and the site of spore formation. An intralamellar branchial form develops cysts within gill lamellae. A cutaneous form causes large lesions or pustules within the subcutaneous layers and underlying musculature of the skin; a granulomatous form causes large tumor- like le- sions. An integumentary form causes white cysts on the external body sur- face. A gall-bladder form develops within that organ and may obstruct the bile duct. An adipose-fin form localizes solely within the tissue of that fin. Spores from catfish infections are similar morphologically and virtually indistinguishable on the basis of shape and dimensions. They closely resemble H. exilis described in channel catfish. The intralamellar form is observed commonly among cultured catfish but does not cause deaths. The role of this form as a debilitating agent is suspected but unproven. Spore development occurs within capillaries of gill lamellae or blood vessels of gill filaments. The resultant opaque, spore- filled cysts may be foynd in large numbers and are readily observed in wet mounts. The inter lame liar form of Henneguya develops spores within basal cells between gill lamellae (Figure 97). This form, in contrast to the intralamel- lar form, has caused large losses among very young channel catfish. Mor- talities of 95% or more among fingerlings less than 2 weeks old have been reported. Loss of respiratory function accompanies acute infections. Fish exhibit signs of anoxia, swimming at the surface of ponds with flared gill opercula. Infected fish are unable to tolerate handling. Most attempts to treat with parasiticides have resulted in additional losses. As with other myxosporidean infections, prevention is the only control measure because no chemical treatment is effective. The disease has been spread from hatchery to hatchery with shipments of infected fingerlings. Confirmation of the interlamellar form in a catfish population may warrant destruction of the infected fish and decontamination of the rearing facilities involved. 326 FISH HATCHERY MANAGEMENT :|- % > • :.£■ j^ Figure 97. The interlamellar form of Henneguya with resultant spore-filled cysts (arrow) between gill lamellae. Gill lamellae may become greatly hypertrophied and lose all of their normal appearance. 175x magnification. (Courtesy Charlie E. Smith, FWS, Bozeman, Montana.) CERA TOMYXA Ceratomyxa shasta is a serious myxosporidian parasite of salmonids in the western United States that causes severe losses of rainbow and cutthroat trout, steelhead, and coho and chinook salmon. Heavy mortalities of adult salmon have occurred just prior to spawning. Severe hatchery epizootics, resulting in 100% mortality, were reported as early as 1947 in California. Many epizootics have been reported, including significant losses among some wild salmonid populations. Infections also have been found in brook and brown trout, and sockeye and Atlantic salmon. The spores of Ceratomyxa shasta are tiny and elongated and can be found in great numbers in the lining of the gut and in cysts in the liver, kidney, spleen, and muscle. The disease is contracted by adult salmon upon enter- ing infected fresh water. Lake conditions are believed to be vital to the development of the infective stage of the parasite. The entire life cycle, which is poorly known, may be completed in 20 to 30 days at 53°F. Some researchers feel that infection will not occur below 50°F. The first signs of infection in domestic rainbow trout include lack of ap- petite, listlessness, and movement to slack water. The fish may darken and shed fecal casts. The abdomen often swells with ascites. Exophthalmia often occurs. The first internal changes appear as small, whitish, opaque FISH HEALTH MANAGEMENT 327 areas in the tissue of the large intestine. As the disease progresses, the en- tire intestine becomes swollen and hemorrhagic. The disease has been transferred by inoculating ascites (containing schizonts, trophozoites, and spores) from infected rainbow trout into the visceral cavity of noninfected rainbow trout. Fish-to-fish transmission by other methods has failed. Infection seemingly does not depend on the ingestion of food organisms or any of the known stages of the parasite. The mode of transmission remains unknown. There is no known treatment for Ceratomyxa shasta, so the parasite should be avoided at all costs. Water supplies known to be contaminated should not be utilized for hatchery purposes without pretreatment. There should be no transfer of eggs, young fish, or adults from infected to noninfected areas. MYXOSOMA Myxosoma cerebralis is the causative agent of whirling disease, a serious con- dition of salmonid fishes. Because of its importance, special emphasis should be given to it. The disease was endemic in central Europe, but now is well-established in France, Italy, Czechoslovakia, Poland, the Soviet Un- ion, Denmark, and the United States. It first appeared in the United States at a brook trout hatchery in Pennsylvania and has spread as far west as California and Nevada. The obvious sign of tail-chasing (whirling) becomes evident about 40 to 60 days after infection and may persist for about 1 year. The whirling symptom is caused by erosion of the cranial cartilage, par- ticularly around the auditory equilibrium organ behind the eye, by the tro- phozoite phase of the parasite. Infected fingerling trout can become so exhausted by the convulsive whirling behavior that they fall to the bottom and remain on their sides (Figure 98). In general, only young trout (fry to small fingerlings) exhibit whirling disease so it has been referred to as a "childhood disease." However, older fish can become infected even though they show no clinical signs. Mortality has varied greatly among epizootics, sometimes minor, sometimes devastating. The complete life cycle of Myxosoma cerebralis has never been established. In the past, it has been thought that the spores are ingested by fish, and that the sporoplasm leaves the spore, penetrates the intestinal mucosa, and migrates to the cartilage where it resides as the trophozoite. However, this hypothesis has never been verified experimentally and other means of in- fection may be possible. Most recent studies suggest that the spores are not infective upon release from the fish, but must be aged in mud for 4-5 months. External signs alone are not adequate for positive diagnosis of Myxosoma cerebralis infections. Verification requires identification of the spore stage, 328 FISH HATCHERY MANAGEMENT Figure 98. Characteristic signs of whirling disease in older fish that have sur- vived the disease are a sunken cranium, misshapen opercles, and scoliosis of the spine due to the destruction of cartilage (arrow). (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkansas.) which may not appear for 4 months after infection. In heavy infections, spores readily can be found in wet mounts or histological sections (Figure 99). They are ovoidal (front view) or lenticular (in profile), and have two pyriform polar capsules containing filaments at the anterior end. Because of the seriousness of whirling disease, control and treatment measures must be rigorous. Ideally, all earthen rearing units and water sup- plies should be converted to concrete, followed by complete decontamination of facilities and equipment with high concentrations of such chemicals as sodium hyprochlorite or calcium oxide. Allow the treated area to stand 4 weeks, clean thoroughly, and ref>eat decontamination. New eggs or fry must be obtained from a known uncontaminated source and raised in spore-free ponds or raceways for the first 8 months. PLEISTOPHORA Several species of Pleistophora infect hatchery fish. As the name of the class Microsporidea indicates, these are exceedingly small protozoans. Pleisto- phora spores are about the size of large bacteria, 3-6 micrometers long and somewhat bean shaped. Severe infections have been reported in the gills of rainbow trout and in the ovaries of golden shiners. In golden shiners, the parasites infest up to about half of the ovary and significantly reduce the fecundity of broodstock populations. The only known control for Pleistophora in rainbow trout is prevention. Rainbow trout or their eggs should not be transferred from infected to uninfected hatcheries. Broodstocks known to be infected should be phased out and the rearing facilities decontamination. FISH HEALTH MANAGEMENT 329 Because there are no known stocks of golden shiners free of Pleistophora ovariae, proper management is the only answer to this problem. The severi- ty of infections increases with age, so only one-year-old broodstock should be used and all older fish destroyed. Trematode Diseases (Monogenetic) Monogenetic trematode parasites of fish can complete their life cycles on fish without involving other species of animals. Although the majority are too small to be seen by the naked eye, some species may reach 5 millime- ters in length. The posterior organ of attachment, the "haptor," is used in identification of different genera and species. There often are marginal hooklets around margin of the haptor and either zero, two, or four large anchor hooks. Species of the family Gyrodactylidae generally are found on the body and fins of fish, rarely on the gills. These parasites move around freely. The members of this family give birth to live young similar in appearance to the adults. They have no eye spots, 16 marginal hooklets, and two large anchors. Species of the family Dactylogyridae are found commonly on the gills of fish. Dactylogyrids lay eggs, and have eye spots, one pair of anchor hooks, Figure 99. Stained Myxosoma cerebralis spores in a histological section of cartilage, 875 x magnification. (Courtesy G. L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkansas.) 330 FISH HATCHERY MANAGEMENT and 16 marginal booklets. Dactylogyrids are common on warmwater fish while Gyrodactylids are common on both trout and warmwater species. GrRODACTTLUS Species of Gyrodactylus can be identified by the developing embryo inside the adult as well as by their lack of eye spots. The haptor has two large an- chor hooks and 16 marginal booklets (Figure lOO). These worms are so common on trout that it is unusual to examine fish and not find them. Di- agnosis is made from wet mounts of fin tissue or skin scrapings under a mi- croscope at 35 X or lOOx magnification (Figure 101 ). The parasites may occur in large numbers and cause skin irritation and lesions. Fish with large numbers of Gyrodactylus may appear listless, have frayed fins, and flash frequently. In ponds, they may gather in shallow water in dense schools. On salmonids, these parasites are removed easily by treating the fish with formalin at 167 to 250 parts per million for up to 1 hour, or at 25 parts per million in ponds with one or more treatments. Potassium perman- ganate at 2 to 3 parts per million for 1 hour should be tested as an alter- nate treatment for formalin-sensitive trout. For warmwater fish, excellent results are obtained with Masoten (re- gistered with the Food and Drug Administration) at 0.25 part per million active ingredient as an indefinite pond treatment. Other good pond treat- ments are copper sulfate at whatever concentration that can be used safely, and formalin at 15-30 parts per million. DACTYLOGYRUS Dactylogyrus is but one genus of several dactylogyrids found on warmwater fish. These worms are particularly serious parasites of cyprinids. Dactylo- gyrus, a small gill parasite, can be identified by the presence of four eye spots, one pair of anchor hooks, and 16 marginal booklets (Figure lOO). No embryos will be found internally, as these worms lay eggs. These parasites feed on blood and can cause serious damage to the gills of warm- water fish when numerous. Clinical signs easily can be mistaken for those caused by an oxygen deficiency or other gill infections. Dactylogyrids easi- ly are controlled with 0.25 part per million active Masoten, copper sulfate at whatever concentration is safe, or 15-25 parts per million formalin as an indefinite pond treatment. Formalin at 125-250 parts per million for up to 1 hour is an effective bath treatment for raceways, tanks, or troughs. CLEIDODISCUS Cleidodiscus sp. is common on the gills of catfish and a variety of other warmwater fish species. Like Dactylogyrus, it has eye spots, but has four FISH HEALTH MANAGEMENT 331 our 1 Figure 100. Gyrodactylus sp. (l) and Dactylogyrus sp. (2). Figure 101. Gyrodactylus on a rainbow trout fin, 35x magnification. (Courtesy G. H. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkansas.) 332 FISH HATCHERY MANAGEMENT Figure 102. Cleidodiscus sp. large anchor hooks (Figure 102) and lays eggs; unlaid eggs frequently may be seen within the adult worm. Cleidodiscus is found only on the gills where, when numerous, it causes respiratory problems by severely damag- ing the tissue. Signs of infection, therefore, are those of gill damage and may be similar to those seen when oxygen is low. The most effective control is Masoten at 0.25 part per million as a pond treatment. Other controls include formalin at 15-25 parts per million, 2 parts per million potassium permanganate, or copper sulfate at whatever rate can be used safely as an indefinite pond treatment. In raceways, tanks, or troughs, use 125-250 parts per million formalin for up to 1 hour. Trematode Diseases (Digenetic) Digenetic trematodes require one or more animal hosts, in addition to fish, to complete their life cycles. These parasites can be divided into two major groups; (l) those that live in fish as adults, producing eggs that leave the fish to continue the life cycle, and (2) those that penetrate the skin of the fish and live in the fish as larvae, usually encysted in the tissue, until the fish is eaten by the final host. SANGUINICOLA Blood flukes (Sanguinicola davisi) live as adults in arterioles of the gill arches of salmonids and other fish species. These tiny worms lay eggs that become trapped in the capillary beds of the gills and other organs, where they develop into miracidia that have a characteristic dark eye spot (Figure 103). When fully developed, the ciliated miracidia burst from the gill to be eaten by an operculate snail, the only intermediate host in the life cycle. Cercaria emerge from the snail and penetrate fish to complete the cycle. The control of blood flukes is difficult. It depends upon either continual treatment of infected water supplies to kill the cercaria, or eradication of FISH HEALTH MANAGEMENT 333 the intermediate host snails. In most cases, however, blood flukes are debil- itating but not the cause of serious losses of fish. It is conceivable that large numbers of miracidia leaving the gill at one time could cause a signif- icant loss of blood and damage to the gills. Eggs and developing miracidia also interfere with the circulation of blood in the gill capillaries and in the capillary beds of the kidney and liver. Copepod Parasites Most copepods in fresh and salt water are an important part of the normal diet of fish. Certain species, however, are parasitic on fish and the sites of their attachment may become ulcerated and provide access for secondary infections by fungi and bacteria. Crowded hatchery rearing units provide ideal conditions for infestations by copepods because of the dense fish pop- ulations and rich environmental conditions. Under most hatchery condi- tions, however, serious losses of fish seldom are caused by parasitic copepods. The stocking of copepod-infested fish has infected wild fish in streams. # 1 • 1^ f ■* # ^ 1 •'^.^^ * # ^%^ % * # # ■ V* .^ Figure 103. Sanguinkola davisi, 2,000x magnification. (Courtesy G. L. Hoff- man, Fish Farming Experimental Station, Stuttgart, Arkansas.) 334 FISH HATCHERY MANAGEMENT ARGULUS Argulus spp. have been given the common name of fish lice because of their ability to creep about over the surface of the fish. On first glance, they look like a scale but, on closer examination, are seen to be saucer shaped and flattened against the side of the fish. They have jointed legs and two large sucking discs for attachment that may give them the appearance of having large eyes (Figure 104). Argulids have an oral sting that pierces the skin of the host fish. They then inject a cytolytic substance, and feed on blood. If these organisms become abundant, even large fish may be killed. Masoten (registered by the Food and Drug Administration) at 0.25 part per million active is used for the treatment of Argulus in ponds. Complete dry- ing of rearing units will kill eggs, larvae, and adults. LERNAEA Lernaea spp. are most commonly found on warmwater fish. However, one species, L. elegans, lacks host specificity and even attacks frogs and salamanders. Heavy infestations have caused massive mortality in carp and goldfish populations. The parasite penetrates beneath scales and causes a lesion at the point of attachment. The damage caused is associated with loss of blood and exposure to secondary infections by fungi, bacteria, and possibly viruses. Lernaea are long (5-22 millimeters) slender copepods which, when at- tached, give the appearance of a soft sticks with two egg sacs attached at the distal ends. Actually, the head end is buried in the flesh. This end has large, horn- like appendages that aid in identification of the parasite (Figure 105). Figure 104. Argulus sp. Figure 105. Lernaea sp. FISH HEALTH MANAGEMENT 335 Masoten at 0.25 part per million active as a pond treatment, repeated four times at weekly intervals, gives good control of anchor worms. How- ever, inconsistent results are obtained when water temperatures exceed 80°F or when the pH is 9 or higher. During summer months, Masoten treatment should be applied early in the morning and it may be necessary to increase the concentration to 0.5 part per million active for best results. Packing and Shipping Specimens Several state agencies have laboratories with biologists trained in the diag- nosis of fish diseases. In addition, several fish- disease laboratories and a number of trained hatchery biologists in the United States Fish and Wildlife Service are available for help in disease diagnosis. In recent years private consulting biologists also have set up practices in disease diagnosis. Correct diagnosis depends upon accurate and detailed information re- garding the fish and the conditions under which they were raised, and especially upon the proper preparation of material that will be shipped to a fish- disease laboratory. The more information that is available, the more likely that the diagnosis will be correct. If, after a preliminary diagnosis in the hatchery, some treatment already has been started, specimens and information nevertheless should be sent to a disease laboratory for verification. Although the symptoms may seem typ- ical, another disease may be present. It is not uncommon to have two disease conditions present at the same time, one masking the other. Although treatments may be effective for one condition, the other disease may still be uncontrolled. Hatchery personnel should furnish the laboratory with correctly collected and handled material, including all available infor- mation, at the earliest possible date. // the required information is not fur- nished with specimens, conclusive diagnosis may not be possible. To facilitate the packing and shipping of proper specimens and informa- tion, a comprehensive checklist, such as the Diagnostic Summary Informa- tion form (Figure 106), should be included. All instructions and questions should be read carefully. All questions should be answered. If an answer cannot be furnished, or a question is not applicable, this should be indicat- ed in each case. When disease breaks out, specimens should be collected and preserved before any treatment is given or started. Only a few fish should be sent for examination, but these should be collected with the ut- most care. Dead fish or fish that appear to be normal are nearly worthless. The most desirable fish are those that show most typically the sings of the disease in question. Moribund, but still living, fish are the best for diagnostic purposes. 336 FISH HATCHERY MANAGEMENT DIAGNOS nC SUMMARY INFORMATION INSTRUCTIONS: Prepare in duplicate, retain one copy at hatchery. Answer all ques- tions. If information is not available or not applicable, please check "Na" box. If samples are to be sent separately, note Item 26. To: From: 1. FISH Species: Age: Date of collection: Size: Density: Date of first feeding: (Number/lb.) (Lbs./cu. ft. of water) (small fingerling only) 2. WATER— CONDITIONS— Na D Hatchery Trough LJ Dirt Pond I I Circular Pool I I Lake 1 I Concrete Raceway I I Stream 1 I Dirt Raceway I I Rate of Change: per hr. Clear I I Turbid I I Muddy I I Colored I I Indicate color Temp °F pH O2 ppm 3. WATER SOURCE — Na I I (If combination, give percent, temp., and pH of each. If individual, give temp, and pH only) Spring I I % Open Stream I I % Reservoir I I % Well n % Lake D % Runoff rainwater D % Temp. pH Temp. pH 4. IF POND WATER— Na D *\Vater Bloom: Abundant I I Surface Algae: Abundant I — I Moderate I I Partial Cover I I None LJ None LJ Type and dates of pond water treatment (if preceded mortality) For Algae For course vegetation Other treatments * (If bloom is heavy — send preserved sample) 5. FISH FOOD— Na D Natural I — I Pond fertilization with organic fertilizer I I Mineral fertilizer Ll None Lj Service Diet LJ Pellets LJ Pellets with Meat LJ Other diet LJ (Give formula below) How long Rate of Brand name diet fed Feeding of pellets Formula: Time in storage: Refrigerated: Yes LJ No D Figure 106. Diagnostic Summary Information form. FISH HEALTH MANAGEMENT 337 6. FISH COLLECTED FOR SHIPMEN L, INOCULATION OF MEDIA, OR BOTH (Live (Ish arc superior to preserved fish) — Na I I Dead I I Moribund I I Appear slightlv abnormal I I Healibv LJ Not selected in any special way I I 7. PRFA'IOrS TREATMENT (If any)— Na D Number of treatments: Hours or Davs- Chemical(s) used: Sulfamerazine I I Terramycin I I Cbloronivcelin I I PMA D Calomel I I Roccal I I Formalin I I Other 8. MORTALrriES— Na D List on a separate page pickofT by days, starting with the first day mortalities seem abnormal, and indicate on which davs treatments were administered, if any. Mortalities should be listed as individual tioughs or tanks, as well as by lot. If experimental treatments are given, a separate list of mortalities in the control trough should be included. 9. OENERAL APPEARANCE— Na D Normal I I Nervous and scarv I I Sluggish I I Floating listlesslev I I Flashing I I Swimming upside I I down or on the side Other: Spiraling or corkscrewing I I Making spasmodic movements I I Sinking to the bottom I I Rubbmg against the bottom I I 10. APPETITE— Na D Normal I I Reduced I I Refuse Food I I 1 1 . ARRANGEMENT IN WATER— Na D Normal Distribution LJ Schooling LJ Near surface I — I Gasping for air I I Crowding water inlet I I Floating towards outlet I — I Distribution at even distance, one fish from another, and facing water current I — I 12. BODY SL'RF.\CE— Na D Normal LJ /Bluish film: in patches I — I or all over I — I /Grayish-white: patches LJ or tufts I I Swollen areas as furuncles I — I Deep open lesions with pus and blood LJ /Shallow red ulcers: small I — I large I — I /Necrotic areas: separate I I confluent I I gray I I It. brown I — I on head LJ all over LJ lips and head especially I — I /Granulations: glass bead-like I I pearl-like I I on fins I I on bodv I I variable in size I I Figure 106. Continued. 338 FISH HATCHERY MANAGEMENT 12. BOl)\ SURFAC.K— Continued: /Pinpoinl pimples I I Cysts I I /Pinpoint spots: white I I or black I I /Paiasiics: verv small, bareh' visible, soil I I oi Ifjnger, hard I I (often with suallowiail appearance) /Fish abnormally dark: entire bod% I I certain body areas I I Indicate where Growth LJ oi Warts I I Iriegiilai I I proliferating I I on surface I I protruding from: vent I I nostrils I I mouth LJ gills LJ color: fish bod\ D red D black D 13. FINS— Na D Normal I I Swollen I I Necrotic I I Frayed I I Bluish-white I I Twisted I I Eioded I I /Spots present: white LJ black LJ /Blood-shot I — I Parasite present I — I 14. CAUD.AL PKDL'NCLE— Na D Slightly Swollen D Bluish-White D Necrotic D Very Swollen I I Fungus-like tufts present I I Inflamed I I 15. CILI.S— Na n Covers open more I I Swollen I I Covered with mucus, I — I than normallv food and dirt particles Patches: white I I brown I I gray I I (IF EXAMINED UNDER MICROSCOPE) Filaments and Lamellae: Swollen LJ fused I I club-shaped I — I ballooned I I Cottonv tufts present I I Small gravish-white objects: on filaments I — I on lamellae I — I between filaments I I between lamellae I I Color of gills: deep red LJ pale red I — I hemorrhagic I I pale pink I — I 16. MUSCULATURE— Na D Sores I I or Fmuncles I I filled with red pus I I Small red spots I I i sores I I or filled with creamy I I or cheesy I I contents cysts I I Hard cysts like sand grains: small I I black I I large I I or \ellow I I Figure 106. Continued. FISH HEALTH MANAGEMENT 339 17. EVES— Na D Normal I I opaque I I W'liiif: lens I I or center I I Tinv spt)t in lens I I Red spots in cornea I — I Popeye I I One eye missing I I Both eyes missing I I If a needle is inserted in the eye socket and the eye is pressed while fish head is under water, gas bubbles I I or opaque fluid I — I escapes. IS. BODY CAMTV— Na D Appears normal LJ Excessive fluid present I — I /Fluid: Colorless D Opaque D Bloodv D /Present in lining: Spots U or Hemorrhages LI /Worms: lape-like LJ or Round LJ /Small Cysts U 19. INTESTINAL TRACT— Na D Normal LJ Emptv LJ Filled with food I — I /Filled with mucus: Colorless CH Yellow LJ Reddish lJ Hind gut bloody LI Blood in vent LI Stomach opened LI Round worms present LI Flat worms present LI 20. LI\'ER— Na D Normal D Red D Yellow D Brown D Pale D Color of coffee w ith cream LJ Marbled LJ Spotty LJ /Cysts: Small I I or Large I I /Gall Bladder Bile: Greenish-yellow D Watery Clear D or Bluish-Bhuk D 21. SPLEEN— Na D Red D Black-red D Pale D Spotty D Shrivelled D Swollen D Lumpy D Grosslv Enlarged □ 22. PYLORIC CAECA— Na D Normal LJ Fused together I I Swollen I — I Worms inside LJ Bloodshot I — I Figure 106. Continued. 340 FISH HATCHERY MANAGF.MKNT 23. KIDNKY— Na D Normai Cj /Pinpoint Spots: Gray Lj or White LI Gray pustules: How many: Where located: Small CH Creamy consistency Lj Hard and gritty U Large I I Cheesy consistency I I 24. TUMORS— Na D Any internal organ: Much enlarged Lj Irregular in shape LI O IHER CONDITIONS OR SYMPTOMS NOTED: (Continue on reverse, if necessary) 26. If samples are submitted separately from this summary, please identify each test tube, jar, or other container with the following: 1. Name and address of sender. 2. Dates when specimens were collected, or media inoculated. (See instruction sheet for packing and shipping specimens.) Figure 106. Continued. Shipping Live Specimens When it is necessary to ship live specimens for diagnostic purposes: (l) as- sure that everything possible is done to insure that the specimens will be received alive; (2) take extra precautions to insure that other parcels will not be damaged by water leakage. Postal authorities have advised that such shipments should bear the notation "Special Handling" and, in larger lettering, "LIVE FISH-THIS SIDE UP." When shipments might exceed 36 to 48 hours duration by other means, it is best to ship by air express. Air-express packages should bear the name of the final carrier, final terminal, and any special delivery instructions, in- cluding a telephone contact. Many shipments can be more economical by regular air mail. An attempt should be made to determine local schedules to reduce shipping time. Whether air-mail or air-express shipments are made, packing should al- low for gas expansion that occurs in high altitude flights. Fully inflated packages have burst enroute, causing the contents to leak and the fish to die. Plastic bags containing about one- fourth water and half or less air or FISH HEALTH MANAGEMENT 341 oxygen usually provide room for expansion. A general precaution is to use a double bag system, one bag filled and sealed within another. It is best to ship a minimum number of specimens. Sick fish and coldwater fish, such as trout, require greater volumes of water than healthy or warmwater fish. Twenty volumes of water for each volume of fish usually will be adequate for healthy fish, but greater volumes should be provided for sick fish. Dur- ing extreme hot or cold weather, insulated containers may be required. Expanded polystyrene picnic hampers provide good insulation but are rela- tively fragile and require protection against damage. They should be packed, therefore, in a protective corrugated cardboard box or other con- tainer. Coldwater fish usually ship better if ice is provided. The ice should be packed in double plastic bags so that it will not leak when it melts. Shipping Preserved Specimens Preservatives typically are corrosive and odorous. Containers should be un- breakable and absorbent material should be provided in the event leakage does occurs. A good procedure is to fix the fish in a proper fixative for a day or two, then place the preserved fish, with a very small volume of fixa- tive, in a plastic bag. The sealed bag should be placed within a second plastic bag, which also should be sealed. This durable package has minimal weight. Select representative specimens. Examine them carefully to supply data in the order given in the Diagnostic Summary Information form. Bouin's solution is a preferred fixative. Its recipe is: picric acid (dangerous), 17.2 grams; distilled water, 1,430 milliliters; formalin, 475 mil- liliters; glacial acetic acid, 95 milliliters. NOTE: picric acid explodes when rapidly heated. Handle accordingly. Weigh picric acid and place crystals in a pyrex container large enough to hold 2 liters (2,000 milliliters) and add distilled water. Heat on a stove. Stir occasionally until all crystals are dis- solved. Do not boil the solution. When crystals have dissolved, remove the solution from the stove and cool it completely. Add the formalin and gla- cial acetic acid to the cooled solution. Stir briefly and pour the mixture into a jar. This solution will keep well, but should be protected from freezing. Volume of the fixative should be at least five to ten times that of the fish or tissue. (Thus, put only one 6- inch fish in a pint of fixative.) Fish and tissues should be left in the fixative for at least 24 hours, and then the fixing solution replaced with 65% ethyl alcohol. However, if alcohol is not available, retain the specimens in Bouin's fluid. To facilitate fixation, fish, regardless of size, should be slit down the ab- domen from the anus to the gills. The air bladder should be pulled out and broken to permit fixation of the kidney. The kidney of 6-inch or larger fish should be split along its entire length. The intestines and other organs 342 KISH llAICHKRY MANAGEMENT should be slit if the fish are larger than fingerlings. It also is desirable to cut the skin along the back of the fish. If the fish are larger than 6 inches, the cranial cap should be opened to facilitate fixation of the brain. The importance of these incisions cannot be overemphasized. If the fish are too large to ship whole, cut pieces from individual tissues (gill, heart, liver, etc.), and especially any lesions observed. These pieces should not be larger than one-half inch square and one-quarter inch thick. Commercial formalin (containing about 40'^ formaldehyde) also can be used for preserving specimens and should be mixed with nine parts of wa- ter to make approximately a 10% formalin solution. Unless the lesions are very clear and obvious, always preserve several healthy specimens of the same size and age as the sick fish, and send them at the same time in a separate container. This important step often determines whether or not the disease can be diagnosed. Fish Disease Leaflets The Fish Disease Leaflet (FDL) series is issued by the United States Fish and Wildlife Service in order to meet the needs of hatchery personnel for specific information on fish diseases. Each Fish Disease Leaflet treats a par- ticular disease or parasite, and gives a brief history of the disease, its etiolo- gy, clinical signs, diagnosis, geographic range, occurrence, and methods of control. As new information becomes available, the Fish Disease Leaflets are revised. They are distributed from the Library, National Fisheries Center (Leetown), Route 3, Box 41, Kearneysville, West Virginia 25430. In the following list, leaflets that have been superseded by more recent ones are omitted. FDL-1. Infectious pancreatic necrosis (IPN) of salmonid fishes. Ken Wolf. 1966. 4 p. FDL-2. Parasites of fresh water fish. II. Protozoa. 3. Ichthyophthirus mul- tifilis. Fred P. Meyer. 1974. 5 p. FDL-5 Parasites of fresh water fish. IV. Miscellaneous. Parasites of cat- fishes. Fred P. Meyer. 1966. 7 p. FDL~6. Viral hemorrhagic septicemia of rainbow trout. Ken Wolf. 1972. 8 p. FDL-9. Approved procedure for determining absence of viral hemor- rhagic septicemia and whirling disease in certain fish and fish products. G. L. Hoffman, S. F. Snieszko, and Ken Wolf. 1970. 7 p. FDL-13. Lymphocystis disease offish. Ken Wolf. 1968. 4 p. FISH HEALTH MANAGEMENT 343 FDL-15. Blue-sac disease of fish. Ken Wolf. 1969. 4 p. FDL-19. Bacterial gill disease of freshwater fishes. S. F. Snieszko. 1970. 4 p. FDL-20. Parasites of freshwater fishes. II. Protozoa. 1. Microsporida of fishes. R. E. Putz. 1969. 4 p. FDL-21. Parasites of freshwater fish. I. Fungi. 1. Fungi (Saprolegnia and relatives) of fish and fish eggs. Glenn L. Hoffman. 1969. 6 p. FDL-22. White-spot disease of fish eggs and fry. Ken Wolf. 1970. 3 p. FDL-24. Ulcer disease in trout. Robert G. Piper. 1970. 3 p. FDL-25. Fin rot, cold water disease, and peduncle disease of salmonid fishes. G. L. Bullock and S. F. Snieszko. 1970. 3 p. FDL-27. Approved procedure for determining absence of infectious pan- creatic necrosis (IPN) virus in certain fish and fish products. Donald F. Amend and Gary Wedemeyer. 1970. 4 p. FDL— 28. Control and treatment of parasitic diseases of fresh water fishes. Glenn L. Hoffman. 1970. 7 p. FDL-31. Approved procedure for determining absence of infectious hematopoietic necrosis (IHN) in salmonid fishes. Donald F. Amend. 1970. 4 p. FDL-32. Visceral granuloma and nephrocalcinosis. Roger L. Herman. 1971. 2 p. FDL-34. Soft-egg disease of fishes. Ken Wolf. 1971. 1 p. FDL-35. Fish virology: procedures and preparation of materials for pla- quing fish viruses in normal atmosphere. Ken Wolf and M. C. Quimby. 1973. 13 p. FDL-36. Nutritional (dietary) gill disease and other less known gill diseases of freshwater fishes. S. F. Snieszko. 1974. 2 p. FDL-37. Rhabdovirus disease of northern pike fry. Ken Wolf. 1974. 4 p. FDL-38. Stress as a predisposing factor in fish diseases. Gary A. Wedemeyer and James W. Wood. 1974. 8 p. FDL-39. Infectious hematopoietic necrosis (IHN) virus disease. Donald F. Amend. 1974. 6 p. FDL-40. Diseases of freshwater fishes caused by bacteria of the genera Aeromonas, Pseudomonas, and Vibrio. S. F. Snieszko and G. L. Bullock. 1976. 10 p. FDL-41. Bacterial kidney disease of salmonid fishes. G. L. Bullock, H. M. Stuckey, and Ken Wolf. 1975. 7 p. FDL-43. Fish furunculosis. S. F. Snieszko and G. L. Bullock. 1975. 10 p. FDL-44. Herpesvirus disease of salmonids. Ken Wolf, Tokuo Sano, and Takahisa Kimura. 1975. 8 p. FDL-45. Columnaris disease of fishes. S. F. Snieszko and G. L. Bullock. 1976. 10 p. 344 FISH HATCHERY MANAGEMENT FDL-46. Parasites of freshwater fishes. IV. Miscellaneous. The anchor parasite (Lernaea elegans) and related species. G. L. Hoffman. 1976. 8 p. FDL-47. Whirling disease of trout. G. L. Hoffman. 1976. 10 p. FDL-48. Copepod parasites of freshwater fish: Ergasilus, Achtheres, and Salmincola. G. L. Hoffman. 1977. 10 p. FDL-49. Argulus, a branchiuran parasite of freshwater fishes. G. L. Hoff- man. 1977. 9 p. FDL-50. Vibriosis in fish. G. L. Bullock. 1977. 11 p. FDL-51. Spring viremia of carp. Winfried Ahne and Ken Wolf. 1977. 11 p. FDL-52. Channel catfish virus disease. John A. Plumb. 1977. 8 p. FDL-53. Diseases and parasites of fishes: an annotated list of books and symposia, with a list of core journals on fish diseases, and a list of Fish Disease Leaflets. Joyce A. Mann. 1978. 77 p. FDL-54. Pasteurellosis of fishes. G. L. Bullock. 1978. 7 p. FDL-55. Mycobacteriosis (tuberculosis) of fishes. S. F. Snieszko. 1978. 9 p. FDL-56. Meningitis in fish caused by an asporogenous anaerobic bac- terium. D. H. Lewis and Lanny R. Udey. 1978. 5 p. FDL-57. Enteric redmouth disease of salmonids. G. L. Bullock and S. F. Snieszko. 1979. 7 p. FDL-58. Ceratomyxa shasta in salmonids. K. A. Johnson, J. E. Sanders, and J. L. Fryer. 1979. 11 p. Bibliography Allison, R. 1957. A preliminary note on the use of di-n-butyl tin oxide to remove tapeworms from fish. Progressive Fish-Culturist 19 (3): 128- 130, 192. Amend, D. F. 1976. Prevention and control of viral diseases of salmonids. Journal of the Fisheries Research Board of Canada 33(4,2): 1059-1066. , and A. J. Ross. 1970. Experimental control of columnaris disease with a new nitro- furan drug, P-1738. Progressive Fish-Culturist 32(l):19-25. , and L. Smith. 1974. Pathophysiology of infectious hematopoietic necrosis virus disease in rainbow trout (Salmo gairdneri): early changes in blood and aspects of the immune response after injection of IHN virus. Journal of the Fisheries Research Board of Canada 31 (8):1371-1378. Amlacher, E. 1970. Textbook of fish diseases. Translation by D. A. Conroy and R. L. Her- man of Taschenbuch der Fischkrankheiten, 1961. T.F.H. Publications, Neptune City, New Jersey. 302 p. Anderson, B. G., and D. L. Mitchum. 1974. Atlas of trout histology. Wyoming Game and Fish Department Bulletin 13. 110 p. FISH HEALTH MANAGEMENT 345 Anderson, D. P. 1974. Fish immunology. T.F.H. Publications, Neptune City, New Jersey. 239 p. Antipa, R., and D. F. Amend. 1977. Immunization of Pacific salmon: comparison of intraper- itoneal injection and hyperosmotic infiltration of Vibrio anguilarum and Aeromonas sal- monicida bacterins. Journal of the Fisheries Research Board of Canada 34(2):203-208. Baler, O. N. 1959. Parasites of freshwater fish and the biological basis for their control. Bul- letin of the State Scientific Research Institute for Lake and River Fish, Leningrad, USSR, volume 49. 226 p. English translation as Office of Technical Service 61-31056, Department of Commerce, Washington, D.C. Bell, G. R. 1977. Aspects of defense mechanisms in salmonids. Pages 56^71 in Proceedings of the international symposium on diseases of cultured salmonids. Tavolek, Redmond, Washington. Buchanan, R. E., and N. E. Gibbons. 1974. Bergey's manual of determinative bacteriology, 8th edition. Williams and Wilkins, Baltimore, Maryland. Bullock, Graham L. 1971. The identification of fish pathogenic bacteria. T.F.H. Publica- tions, Jersey City, New Jersey. 41 p. , and Dl^NE Collis. 1969. Oxy tetracycline sensitivity of selected fish pathogens. US Bureau of Sport Fisheries and Wildlife, Technical Paper 32. , David A. Conroy, and S. F. Snieszko. 1971. Bacterial diseases of fishes. T.F.H. Pub- lications, Jersey City, New Jersey. 151 p. and J. A. McLaughlin. 1970. Advances in knowledge concerning bacteria pathogen- ic to fishes (1954-1968). American Fisheries Society Special Publication 5:231-242. Davis, H. S. 1953. Culture and diseases of game fishes. University of California Press, Berke- ley. 332 p. Dogiel, v. a., G. K. Petrushevski, and YU. K. Polyanski. 1961. Parasitology of fishes. Oliver and Boyd, Edinburgh and London. Dujin, C. van. 1973. Diseases of fishes, 3rd edition. Charles Thomas, Springfield, Illinois. Ehlinger, N. F. 1964. Selective breeding of trout for resistance to furunculosis. New York Fish and Game Journal ll(2):78-90. 1977. Selective breeding of trout for resistance to furunculosis. New York Fish and Game Journal 24(l):25-36. Evelyn, T. P. T. 1977. Immunization of salmonids. Pages 161-176 in Proceedings of the International Symposium on Diseases of Cultured Salmonids. Tavolek, Seattle, Wash- ington. Fijan, N. N., T. L. Wellborn, and J. P. Naftel. 1970. An acute viral disease of channel cat- fish. US Fish and Wildlife Service Technical Paper 43. Fryer, J. L., J. S. Rohovec, G. L. Tebbit, J. S. McMichael, and K. S. Pilcher. 1976. Vaccination for control of infectious diseases in Pacific salmon. Fish Pathology 10(2):155-164. Fujihara, M. P., and R. E. Nakatani. 1971. Antibody production and immune responses of rainbow trout and coho salmon to Chondrococcus columnaris. Journal of the Fisheries Research Board of Canada 28(9):1253-1258. Garrison, R. L., and R. W. Gould. 1976. AFS 67. Vibrio immunization studies. Federal Aid Progress Reports, Fisheries (PL 89-304), US Fish and Wildlife Service, Washington, D.C. Griffin, P. J. 1954. The nature of bacteria pathogenic to fish. Transactions of the American Fisheries Society 83:241-253. , S. F. Snieszko, and S. B. Friddle. 1952. A more comprehensive description of Bac- terium salmonicida. Transactions of the American Fisheries Society 82:129-138. Grizzle, J. M., and W. A. Rogers. 1976. Anatomy and histology of the channel catfish. Agricultural Experimental Station, Auburn University, Auburn, Alabama. 94 p. 346 FISH HATCHERY MANAGEMENT Heartwell, C. M., III. 1975. Immune response and antibody characterization of the channel catfish (Ictalurus punctatus) to a naturally pathogenic bacterium and virus. US Fish and Wildlife Service Technical Paper 85. Herman, Roger Lee. 1968. Fish furunculosis 1952-1966. Transactions of the American Fisheries Society 97(3) :22 1-230. 1970. Prevention and control of fish diseases in hatcheries. American Fisheries Society Special Publication 5:3-15. Hester, E. F. 1973. Fish Health: A nationwide survey of problems and needs. Progressive Fish-Culturist 35(l):ll-18. Hoffman, Glenn L. 1967. Parasites of North American freshwater fishes. University of Cali- fornia Press, Berkeley. 486 p. 1970. Control and treatment of parasitic diseases of freshwater fishes. US Bureau of Sport Fisheries and Wildlife, Fish Disease Leaflet 28. 7 p. 1976. Fish diseases and parasites in relation to the environment. Fish Pathology 10(2):123-128. , and F. P. Meyer. 1974. Parasites of freshwater fishes: a review of their control and treatment. T.F.H. Publications, Neptune City, New Jersey. 224 p. Johnson, Harlan E., C. D. Adams, and R. J. McElrath. 1955. A new method of treating salmon eggs and fry with malachite green. Progressive Fish-Culturist 17(2):76-78. Leitritz, E. and R. C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of Fish and Game, Fish Bulletin 164. Lewis, W. M., and M. Bender. 1960. Heavy mortality of golden shiners during harvest due to a bacterium of the genus Aeromonas. Progressive Fish-Culturist 22(l):ll-14. , and 1960. Free-living ability of a warmwater fish pathogen of the genus Aero- monas and factors contributing to its infection of the golden shiner. Progressive Fish- Culturist 23(3):124-126. LOVELL, R. T. 1975. Nutritional deficiencies in intensively cultured catfish. Pages 721-731 in W. E. Ribelin and G. Migaki, editors. The pathology of fishes. University of Wisconsin Press, Madison. Major, R. D., J. P. McCraren, and C. E. Smith. 1975. Histopathological changes in chan- nel catfish (Ictalurus punctatus) experimentally and naturally infected with channel cat- fish virus disease. Journal of the Fisheries Research Board of Canada 32(4):563-567. McCraren, J. P., M. L. Landolt, G. L. Hoffman, and F. P. Meyer. 1975. Variation in response of channel catfish to Henneguya sp. infections (Protozoa: Myxosporidea). Jour- nal of Wildlife Diseases 11:2-7. , F. T. Wright, and R. M. Jones. 1974. Bibliography of the diseases and parasites of the channel catfish (Ictalurus punctatus Rafinesque). Wildlife Disease Number 65. (Mi- crofiche.) Meyer, F. P. 1964. Field treatment of Aeromonas liquefaciens infections in golden shiners. Pro- gressive Fish-Culturist 26(l):33-35. 1966. A new control for the anchor parasite, Lernaea cyprinacea. Progressive Fish- Culturist 28(l):33-39. 1966. A review of the parasites and diseases of fishes in warmwater ponds in North America. Pages 290-318 in Proceedings of the Food and Agricultural Organization of the United Nations World Symposium on Warmwater Pond Fish Culture, Rome, Vol. 5. 1969. Dylox as a control for ectoparasites of fish. Proceedings of the Annual Confer- ence Southeastern Association of Game and Fish Commissioners 22:392-396. , and J. D. Collar. 1964. Description and treatment of a Pseudomonas infection in white catfish. Applied Microbiology 12(3):201-203. FISH HEALTH MANAGEMENT 347 Plumb, J. A. 1972. Channel catfish virus disease in southern United States. Proceeding of the Annual Conference Southeastern Association of Game and Fish Commissioners 25:489-493. 1972. Effects of temperature on mortality of fingerling channel catfish (Ictalurus punc- tatus) experimentally infected with channel catfish virus. Journal of the Fisheries Re- search Board of Canada 30(4):568-570. , Editor. 1979. Principal diseases of farm-raised catfish. Southern Cooperative Series Number 225. PUTZ, R. R., G. L. Hoffman, and C. E. Dunbar. 1965. Two new species of Plistophora (Mi- crosporidea) from North American fish with a synopsis of Microsporidea of freshwater and euryhaline fishes. Journal of Protozoology 12(2):228-236. Reichenbach-Klinke, Heinz-Hermann, and E. Elkan. 1965. The principal diseases of lower vertebrates. Academic Press, New York. 600 p. Rock, L. F., and H. M. Nelson. 1965. Channel catfish and gizzard shad mortality caused by Aeromonas liquefaciens. Progressive Fish-Culturist 27(3):138-141. Sanders, J. E., and J. L. Fryer. 1980. Renibacterium salmoninarum gen. nov., sp. nov., the causative agent of bacterial kidney disease in salmonid fishes. International Journal of Systematic Bacteriology 30:496-502. Smith, L. S., and G. R. Bell. 1975. A practical guide to the anatomy and physiology of Pacific salmon. Canada Department of Fisheries and Oceans Miscellaneous Special Publication 27. Snieszko, S. F. 1973. Recent advances in scientific knowledge and developments pertaining to diseases of fishes. Advances in Veterinary Science and Comparative Medicine 17:291-314. , editor. 1970. A symposium on diseases of fishes and shellfishes. American Fisheries So- ciety Special Publication 5. 525 p. Summerfelt, R. C. 1964. A new microsporidian parasite from the golden shiner, Notemigonus crysoleucas. Transactions of the American Fisheries Society 93(l):6-10. Vegina, R., and R. Desrochers. 1971. Incidence oi Aeromonas hydrophila in the perch, Perca flavescens Mitchell. Canadian Journal of Microbiology 17:1101-1114. Wedemever, G. a. 1970. The role of stress in the disease resistance of fishes. Amercian Fisheries Society Special Publication 5:30-34. , F. P. Meyer, and L. Smith. 1976. Environmental stress and fish diseases. T.F.H. Pub- lications, Nepturn City, New Jersey. 192 p. , and J. W. Wood. 1974. Stress as a predisposing factor in fish diseases. US Fish and Wildlife Service, Fish Disease Leaflet 38. 8 p. Wellborn, Thomas L. 1967. Trichodina (Ciliata: Urceolariidae) of freshwater fishes of the southeastern United States. Journal of Protozoology 14(3):399-412. 1979. Control and therapy. Pages 61-85 in Principal diseases of farm-raised catfish. Southern Cooperative Series Number 225. , and WiLMER A. Rogers. 1966. A key to the common parasitic protozoans of North American fishes. Zoology- Entomology Department Series, Fisheries No. 4, Agricultural Experimental Station, Auburn University, Auburn, Alabama. 17 p. (mimeo.) Wood, J. W. 1974. Diseases of Pacific salmon: their prevention and treatment, 2nd edition. Washington Department of Fisheries, Seattle. 6 Transportation of Live Fishes One extremely important aspect of fish culture and fisheries management is the transportation of live fishes from the hatchery to waters in which they are to be planted. The objective of this function is to transport as many fish as possible with minimal loss and in an economical manner. This often involves hauling large numbers of fish in a small amount of water, and, depending upon the time involved, can result in extensive deteriora- tion of water quality. Sometimes fish arrive at the planting site in poor physiological condition due to hauling stresses, and may die at the time of planting or shortly thereafter. Transportation Equipment Vehicles Fish are transported in a variety of ways, ranging from plastic containers shipped via the postal service to complex diesel truck-trailer units. Air- planes and seagoing vessels are used to a limited degree (Figure 107). The extensive stocking of Lake Powell by airplane with rainbow trout and largemouth bass involved a large, coordinated effort involving several hatcheries and numerous personnel. 348 TRANSPORTATION OF LIVE FISHES 349 Figure 107. Airplane stocking of trout in a remote lake. (Courtesy Bill Cross, Maine Department of Inland Fisheries and Wildlife.) Figure 108. Fish distribution tank mounted on a gooseneck trailer. This unit can be pulled by a pickup truck. 350 FISH HATCHERY MANAGEMENT Trucks are the principal means of transporting fish. Most hatcheries currently use vehicles near 18,000 pounds gross vehicle weight (GVW). However, units from 6,000 to over 45,000 pounds GVW often are used for moving fish. Automatic transmissions are becoming common in all trucks. Automatic shifting reduces engine lugging or overspeeding, and allows the driver to concentrate on defensive driving rather than on shifting gears. Diesel engines also are gaining in popularity. Minimal service and long life are attractive features but the high initial cost is a major disadvantage. Cab-over trucks are popular in many areas especially where a short turning radius is important. Conventional-cab trucks generally are quieter, have better directional stability, and a less choppy ride because of their longer wheelbase. A relatively new and promising innovation in warmwater fish transporta- tion is the combined use of gooseneck trailers and pickup trucks. These units are low in cost yet very versatile (Figure 108). Tank Design Most new fish-distribution tanks are constructed of fiber glass or alumi- num, but plywood, redwood, stainless steel, glass, galvanized iron, and sheet metal all have been utilized in the past. Aluminum is lightweight, corrosion-resistant, and easily mass-produced. Alloys in the range 3003H14 to 6061T6 will not cause water-quality prob- lems. Fiber glass is molded easily into strong, lightweight tanks and can be repaired readily. Its smooth surface is simple to clean and sanitize. Alumi- num and fiber glass appear equally well- suited for fish- transport tanks. Most tanks constructed in recent years are insulated, usually with styro- foam, fiberglass, urethane, or corkboard. Styrofoam and urethane are pre- ferred materials because of their superior insulating qualities and the minimal effect that moisture has on them. A well-insulated tank miminizes the need for elaborate temperature-control systems and small amounts of ice can be used to control the limited heat rises. Circulation is needed to maintain well-aerated water in all parts of the tank. Transportation success is related to tank shape, water circulation pat- tern, aerator type, and other design criteria. The K factor is the basis for comparing insulation materials. It is the amount of heat, expressed in BTU's, transmitted in 1 hour through 1 square foot of material 1 inch thick for each degree Fahrenheit of tempera- ture difference between two surfaces of a material. The lower the K factor, the better the insulating quality. The following is a list of insulating ma- terials and their respective K factors: TRANSPORTATION OF LIVE FISHES 351 Expanded vermiculite 1.60 Oak 1.18 Pine 0.74 Cork 0.29 Styrofoam 0.28 Fiber glass 0.25 Urethane 0.18 The K values indicate that pine must be 4 times as thick as urethane to give the same insulating quality. Generally, combinations of various materi- als are used in fabricating distribution tanks. The distribution tank in Figure 109 is constructed with marine plywood, insulated with styrofoam and covered inside and out with fiber glass. Units vary in size and may contain several compartments. Warmwater distribution tanks generally are compartmented. Compart- ments facilitate fish stocking at several different sites on a single trip, per- mit separation of species, and act as baffles to prevent water surges. The number of compartments used in tanks ranges from two to eight, four be- ing most common. Tanks in current use have 300-700-gallon capacities, averaging about 450 gallons. However, 1,200-gallon tanks occasionally are used to transport catchable size catfish, trout, and bass. Although most tanks presently in use are rectangular, the trend in recent years has been towards elliptical tanks, such as those used to transport milk. This shape has several advantages. Figure 109. Fiberglass distribution tank with four compartments, each with an electric aerator (arrow). Additional oxygen is provided through carbon rods or micropore tubing on the bottom of the tank. (McNenny National Fish Hatchery, FWS.) 352 FISH HATCHERY MANAGEMENT (1) "V"-shaped, elliptical, or partially round tanks promote better mix- ing and circulation of water as the size of the tank increases. (2) Polyurethane insulation, which has the best insulating qualities, lends itself ideally to a round or oval tank. It can be injected easily within the walls of the tank. (3) These tanks can be constructed with few structural members and without sharp corners that might injure fish. (4) Rapid ejection of fish is facilitated by an elliptical tank. (5) Lowering the water level in these tanks reduces surface area and sim- plifies the removal of fish with dip nets. The rounded bottom also contri- butes in this respect. (6) As this shape of tank is widely used by bulk liquid transport com- panies, they are mass-produced and readily available. (7) This shape conforms to a truck chassis and holds the center of grav- ity towards the area of greatest strength. (8) Construction weight is less than that of rectangular tanks of the same capacity. Circulation Circulation systems are of various sizes and designs; all have plumbing ad- ded for the pickup and discharge of water. Suction lines to the pumps lie on the bottom of the tank and are covered by perforated screens. Water is carried to the pumps and then forced through overhead spray heads mounted above the waterline. In most systems, oxygen is introduced in one of the suction lines just ahead of the pump. This usually is controlled by a medical gas-flow meter; because of the danger involved in handling and transporting bottled oxygen, care must be taken to follow all prescribed safety procedures. Self- priming pumps powered by gasoline engines are used to circulate water in many distribution units. Pumps may be close-coupled or flexibly coupled. Although the former type is more compact, it tends to transfer heat to the water. Depending upon ambient air temperature, close-coupled pumps may increase the temperature of 400 gallons of water by about 7°F an hour, whereas flexible coupling will reduce heat transfer to approxi- mately 3°F per hour. Pipes used in conjunction with pumps usually are black or galvanized steel. Although steel is durable, threads may rust, and replacement or modification following installation may prove difficult. Aluminum pipe also has been used in systems of this type, but its advantages and disadvantages are reportedly similar to those of steel except aluminum pipe does not rust. Because of the ease of installation, plastic pipe should be considered for TRANSPORTATION OF LIVE FISHES 353 use. It is noncorrosive, lightweight, and easy to assemble, modify, and remove. Friction reduces water flow through a circulation system if there is an excess of pipe fittings. Further, the diameter of piping should not be re- duced within the system except at the spray devices. Generators and electric pumps or aerators sometimes are used, especially on larger trucks or trailers with multiple tanks. This eliminates the need for many small engines with all their fuel and maintenance problems. Heat and noise problems are minimized by placing the generator on the rear of the unit. A method of circulating water with 12- volt mechanical aerators uses car- bon rods and micropore tubing for dispensing oxygen (Figure llO). Aera- tors alone may not be sufficient to provide the oxygen needed to transport large loads of fish, but a supplemental oxygenation system can increase the carrying capacity of the transportation tank. Some advantages of aerator systems over gasoline- driven water pump systems are: (1) Temperature increases from aerators are less than 1°F per hour, com- pared with 2.5°F with pumps. (2) Aerators and the oxygen injection system can operate independently. There are advantages to carrying small sizes of certain species of fish on oxygen alone. Oxygen also can be used as a temporary backup system if aerators fail. (3) Usually, aerators have fewer maintenance problems. (4) Costs of recirculating equipment and aerators strongly favor aerators. (5) Use of aerators eliminates the space required between the tank and truck cab for pumps and plumbing, so the overall truck length can be reduced to assure safer weight distribution. The empty weight of a truck with a 1,250-gallon tank equipped with aerators is 14,000 pounds — 2,000 pounds less than a similar unit operating with pumps and refrigeration. The most efficient tanks have the highest water circulation rates, but cir- culation rates must be balanced with water capacity. Pumping or aerating systems should be able to circulate at least 40"o of the tank water per minute when 8-9-inch salmonids are hauled, though lesser rates are ap- propriate for smaller fish. Aeration The purpose of aeration during transport is to provide oxygen and to reduce the concentration of carbon dioxide. The exchange of gases between water and the atmosphere is a recognized and important problem in transporting fish. Transport water must contain adequate oxygen, pH 354 FISH HATCHERY MANAGEMENT Figure 110. Aerator-oxygen system designed and tested by FWS personnel at Alchesay National Fish Hatchery, New Mexico, (l) Aerators mounted on top of an aluminum tank. Note the electrical line for the 12-volt system. (2) Aerator with a dual manifold extending through the false bottom of a tank. Water is pulled through manifold (M) and discharged through aerator (A). (3) Aerator in operation. Water is aerated and circulated and carbon dioxide is removed. (4) The false bottom of the tank has been removed to show micropore tubing (arrow) which disperses oxygen into the water. Note bubbling of oxygen through the water. (Photos courtesy Alchesay National Fish Hatchery, FWS.) levels must remain within a tolerable range, and toxic levels of dissolved ammonia and carbon dioxide must be suppressed. A partial solution to this complex problem is aeration by sprays, baffles, screens, venturi units, compressed gas liberation, agitators, or air blowers. Bottled gaseous or liquid oxygen is liberated within tanks in a variety of ways, including per- forated rubber tubing, carborundum stones, carbon rods, and micropore tubing, or is injected directly into the recirculation system. Recent aeration innovations include a miniature water wheel that aerates water during transport and the Fresh- flo^ aerator. The latter is commer- cially available in ten sizes. The system depends upon centrifugal force created by a high speed motor-driven impellor that pulls water into a sys- tem of vanes, producing the turbulence needed to mix water with air, while concurrently removing carbon dioxide. This aerator has been highly satisfactory for transportation of warmwater fish and salmonids. TRANSPORTATION OF LIVE FISHES 355 The formation of scum and foam on the surface of transport water may result from drug usage or excessive mucus produced by large numbers of fish hauled over long distances. Excessive foaming interferes with observa- tion of fish during transit and inhibits aeration. To alleviate this problem, a 10"o solution of Dow Coming's Antifoam AF emulsion should be used at the rate of 25 milliliters per 100 gallons of water. For maximum effective- ness, the compound should be mixed in before drugs are added or fish loaded. Antifoam is nontoxic to fish. Water Quality Oxygen The most important single factor in transporting fish is providing an ade- quate level of dissolved oxygen. However, an abundance of oxygen within a tank does not necessarily indicate that the fish are in good condition. The ability of fish to use oxygen depends on their tolerance to stress, water temperature, pH, and concentrations of carbon dioxide and metabolic products such as ammonia. The importance of supplying sufficient quantities of oxygen to fish in distribution tanks cannot be overemphasized. Failure to do so results in severe stress due to hypoxia and a subsequent buildup of blood lactic acid, and may contribute to a delayed fish mortality. Ample oxygen suppresses harmful effects of ammonia and carbon dioxide. Dissolved-oxygen content of transport water preferably should be greater than 7 parts per million, but less than saturation. Generally, as long as the oxygen concentration is at least 6 parts per million, salmonids have ample oxygen; however, should carbon dioxide levels increase, more oxygen is required by the fish. Oxy- gen consumption by fish increases dramatically during handling and load- ing into the transportation tank. For this reason, additional oxygen (as much as twice the flow normally required) should be provided during load- ing and the first hour of hauling. The oxygen flow can be reduced to nor- mal levels (to provide 6 parts per million in the water) after this acclima- tion period, when the fish have become settled and oxygen consumption has stabilized (see Stress, page 358). The addition of certain chemicals such as hydrogen peroxide has been effective in increasing the oxygen concentration in water. However, a more practical and economical method is to introduce oxygen directly from pres- surized cylinders into the circulating water. Control of water temperature, starving fish before they are transported, and the addition of chemicals and anesthetics to the water have reduced hauling stress. 356 FISH HATCHERY MANACJKMENT Temperature Insulation and ice have been used to control the temperature of transport water. Ice sometimes is difficult to find during a delivery trip and can cause damage to fish and tanks if used in large pieces. The main advantage of ice is its simplicity; it involves no mechanical refrigeration equipment that can break down. Refrigeration units are being used increasingly to mechanically control water temperature. Such units are expensive and require careful mainte- nance. Large units easily justify the cost of refrigeration but small systems require additional development before they become economical (Figure 111). Because temperature is such an important factor, it should be continu- ously monitored and controlled. Electric thermometers are readily available and inexpensive, and provide monitoring of temperature from the truck cab. Temperature strongly influences oxygen consumption by fish; the lower the temperature, the lower the oxygen consumption. For each 1°F rise in temperature, the fish load should be reduced by about 5.6%; conversely, for each 1°F decrease in temperature, the load can be increased about 5.6%. Thus, if a distribution tank will safely hold 1,000 pounds of 9-inch trout in 52°F water, an increase in temperature to 57°F decreases the permissible load by 27.8%i (5° x 5.56%), or to 722 pounds. If the water temperature is decreased from 52°F to 47°F, the load can be increased by 27.8')(i to 1,278 pounds. Figure 111. Aluminum elliptical tank with refrigeration unit mounted at the front. Aeration is by gas-driven pumps and pure oxygen. Note air scoops (arrow) for CO2 removal on front and rear of tanks. (Ennis National Fish Hatchery, FWS.) TRANSPORTATION OF LIVE FISHES 357 Ammonia When fish are transported in distribution tanks, their excretory products accumulate in the water. Ammonia is the main metaboHc product of fish and is excreted through the gills. Total ammonia concentrations can reach 10 parts per million (ppm) or higher in fish distribution tanks depending on the fish load and duration of the haul. Exposure to 11 to 12 parts per million total ammonia (0.13 to 0.14 ppm un-ionized ammonia) for 6 hours and longer adversely affects trout and can reduce stamina. Temperature and time of last feeding are important factors regulating ammonia excretion. For example, trout held in water at 34°F excrete 66% less ammonia than those held in 51°F water, and fish starved for 63 hours before shipment produce half as much ammonia as recently fed fish. Small fish should be starved for at least two days prior to shipping. Fish larger than 4 inches should be starved at least 48 hours; those 8 inches and larger should be starved 72 hours. If they are not, large losses may occur. Water temperature during shipping should be as low as can be tolerated by the fish being handled. Low temperatures not only reduce ammonia production, but oxygen consumption as well. The effects of metabolic waste products and related substances on warm- water fish during transportation have received little attention, but most fish culturists agree that excretory products, mucus, and regurgitated food de- grade water quality and stress the fish. Cannibalistic species, such as large- mouth bass, walleye, and northern pike, obviously should not be starved. Although proper grading for size of fish will reduce cannibalism, it does not eliminate it. Carbon Dioxide Elevated carbon dioxide concentrations are detrimental to fish and can be a limiting factor in fish transportation. A product of fish and bacterial respiration, CO2 acidifies transport water. Although this reduces the per- centage of un-ionized ammonia in the water, it also reduces the oxygen- carrying capacity of fish blood. Fish may succumb if CO^ levels are high, even though oxygen levels are seemingly adequate. Trout appear to tolerate carbon dioxide at levels less than 15.0 parts per million in the presence of reasonable oxygen and temperature, but become distressed when carbon dioxide levels approach 25.0 parts per million. Fish transported in distribution tanks are exposed to gradually increas- ing concentrations of carbon dioxide. Unless aeration is adequate, CO^ lev- els may exceed 20-30 parts per million. In general, for each milliliter of oxygen a fish consumes, it produces approximately 0.9 milliliters of CO2. If the CO2 level increases rapidly, as with heavy fish loads, fish become 358 FISH HAICHERY MANAGEMENT distressed. However, elevated concentrations of CO2 can be tolerated if the rate of buildup is slow. Adequate ventilation, such as air scoops provide (Figure 111), is a neces- sity for distribution units. Tight covers or lids on the units can result in a buildup of CO2 which will stress the fish. Aeration of the water will reduce concentrations of dissolved CO2, if there is adequate ventilation. As men- tioned previously, antifoam agents reduce foaming, which inhibits aeration and contributes to the buildup of CO2. Buffers Rapid changes in pH stress fish, but buffers can be used to stabilize the water pH during fish transport. The organic buffer trishydroxymethyl- aminomethane is quite effective in fresh and salt water. It is highly soluble, stable, and easily applied. This buffer has been used on 29 species of fish with no deleterious effects. Levels of 5-10 grams per gallon are recom- mended for routine transport of fish. The least promising buffers for fish tanks have been inorganic compounds such as phosphates. Handling, Loading, and Stocking Stress Stress associated with loading, hauling, and stocking can be severe and result in immediate or delayed mortality. When fish are handled vigor- ously while being loaded into distribution units, they become hyperactive. They increase their oxygen consumption and metabolic excretion. The first hour of confinement in the unit is critical. Oxygen consumption remains elevated for 30-60, minutes then gradually declines as fish become acclimated. If insufficient oxygen is present during this adjustment period, fish may develop an oxygen debt. The problem may be alleviated if oxygen is introduced into the distribution tank 10 to 15 minutes before fish are loaded, especially if the water has a low dissolved oxygen content. When fish are in the unit, the water should be cooled. After the first hour of the trip, the oxygen flow may be gradually decreased, depending on the condi- tion of the fish. The total hardness should be raised in waters used to hold fish during handling and shipping. The addition of 0.1-0.3% salt and enough calcium chloride to raise the total hardness to 50 parts per million is recommended for soft waters. Calcium chloride need not be added to harder waters, which already contain sufficient calcium. Striped bass are commonly transported and handled in a 1.0% salt solu- tion. Fingerlings should be held in tanks for 24 hours after harvest to allow TRANSPORTATION OF LIVE FISHES 359 them to recover from stress before they are loaded. The fish appear to tolerate handling and transportation much better in saline solutions. The numbers of bacteria in a warmwater fish transport system should be kept at a minimum level. Acriflavin at 1.0-2.0 parts per million (ppm), Furacin at 5.0 ppm, and Combiotic at 15.0 ppm are effective bacteriostats during transport. Although varying degrees of success have been attained with the above compounds, sulfamerazine and terramycin are the only bac- tericides currently registered for use on food fish. Anesthetics Experimentation with anesthetics and their effects on fish was most active during the 1950's. The main benefit of anesthetics is to reduce the meta- bolic activity of fish, which results in lower oxygen consumption, less car- bon dioxide production, and reduced excretion of nitrogenous wastes. Such drugs made it possible to transport trout at two to three times the normal weight per volume of water. Their tranquilizing effects also reduce injury to large or excitable fish when they are handled. Considerable care must be taken to assure that proper dosages of anesthetics are used. Deep sedation (Table 39) is best for transported fish. Deeper anesthesia produces partial to total loss of equilibrium, and fish may settle to the bottom, become overcrowded, and suffocate. If pumps are used to recycle water, anesthetized fish may be pulled against the intake screen, preventing proper water circulation. Methane tricainesulfonate (MS-222) in a concentration of 0.1 gram MS-222 per gallon of water, appears to be useful in transporting fish. Reduced mortality of threadfin shad has been attained when the fish were hauled in a T'o salt solution containing 1.0 gram MS-222 per gallon of water. Concentrations of 0.5 and 1.0 gram MS-222 per gallon of water are not suitable for routine use in the transportation of salmon because anesthetized salmon have both a high oxygen consumption and a long recovery time. Golden shiners have been transported successfully in 8.5 parts per mil- lion sodium Seconal and smallmouth bass in 8.5 parts per million sodium amytol. A pressurized air system was used in conjunction with the drugs. However, caution is advised because drugs tend to lose their strength at temperatures above 50°F. Fathead minnows have been transported safely in 2.3 parts per million sodium Seconal at 50°F. California Department of Fish and Game personnel have reduced oxygen consumption by transported fish with 8.5 parts per million sodium amytol. Oklahoma state personnel suc- cessfully use a mixture of 2.0 parts per million guinaldine and 0.25% salt for transporting a variety of fish. 360 FISH HATCHERY MANAGEMENT Table 39. classification of ihk behavioral changes ihai occur in fishes DURING anesthesia. LEVELS OF ANESIHESIA CONSIDERED VALUABLE TO FISHERIES WORK ARE ITALICIZED. (SOURCE: McFARLAND 19fi0). DEFINABLE LEVELS OF ANESTHESIA STATE PLANE WORD EQUIVALENTS BEHAVIORAL RESPONSES OF FISH II // /// IV Normal 1 Light sedation 2 Deep sedation 1 Partial loss of equilibrium Total loss of equilibrium Loss of reflex reactivity Medullary collapse Reactive to external stimuli, equilibrium and muscle tone normal. Slight loss of reaction to external stimuli (visual and tactile). No reaction to external stimuli except strong pressure; slight decreased oper- cular rate. Partial loss of muscle tone; reaction only only to very strong tactile and vibra- tional stimuli; rheotaxis present, but swimming capabilities seriously dis- rupted; increased opercular rate. Total loss of muscle tone; reaction only to deep pressure stimuli; opercular rate decreased below normal. Total loss of reactivity; respiratory rate very slow; heart rate slow. Respiratory movements cease, followed several minutes later by cardiac arrest. Carrying Capacity The weight of fish that can be safely transported in a distribution unit depends on the efficiency of the aeration system, duration of the haul, wa- ter temperature, fish size, and fish species. If environmental conditions are constant, the carrying capacity of a dis- tribution unit depends upon fish size. Fewer pounds of small fish can be transported per gallon of water than of large fish. It has been suggested that the maximum permissible weight of trout in a given distribution tank is directly proportional to their length. Thus, if a tank can safely hold 100 pounds of 2-inch trout, it could hold 200 pounds of 4-inch trout, and 300 pounds of 6-inch trout. Reported loading rates for fishes vary widely among hatcheries, and maximum carrying capacities of different types of transportation units have not been determined. Fish loadings have been calculated and reported inconsistently. In the interests of uniform reporting by fish culturists, it is suggested that loading densities be calculated by the water-displacement method. This is based on TRANSPORTATION OF LIVE FISHES 361 Table 40. proximate amount of water displaced by a known weight of fish. ALL figures rounded TO NEAREST WHOLE NUMBER. (SOURCE: McCRAREN AND JONES 1978). WEIGHT WATER WEIGHT WATER WEIGHT WAIKR OF FISH DISPLACED OF FISH DISPLACED OF FISH DISPLACED (LB! (GAL! iLB) (GAL5 fLB) (GAL) 100 12 1,500 180 2,800 336 200 24 1,600 192 2,900 348 300 36 1,700 204 3,000 360 400 48 1,800 216 3,100 372 500 60 1,900 228 3,200 384 600 72 2,000 240 3,300 396 700 84 2,100 252 3,400 408 800 96 2,200 264 3,500 420 900 108 2,300 276 3,600 432 1,000 120 2,400 288 3,700 444 1,100 132 2,500 300 3,800 4.56 1,200 144 2,600 312 3,900 468 1,300 156 2,700 324 4,000 480 1,400 168 the actual volume of the distribution tank being used, the weight of fish being transported, and the volume of water displaced by the fish. Table 40 provides the water displacements for various weights of fish. As an example, what would be the loading density of 800 pounds of fish trans- ported in a ,500-gallon tank? T ,. , . pounds of fish Loadmg density = *^ ( , ,1 \ tank capacity — water displaced by fish (pounds per gallon) r ; r / Loading density Loading density (gallons) 800 (galic 500-96 1.98 pounds per gallon TROUT AND SALMON Normal carrying capacity for 1.5-inch and 2.5-inch chinook salmon is 0.5-1.0, and 1.0-2.0 pounds per gallon, respectively. The carrying capacity for 4-5-inch coho salmon is 2.0-3.0 pounds per gallon of water. Under ideal conditions, the maximum load of 8-11-inch rainbow trout is 2.5-3.5 pounds per gallon of water for 8 to 10 hours. Similar loading rates are appropriate for brook, brown, and lake trout of the same size. 362 FISH HATCHERY MANAGEMENT CHANNEL CATFISH Channel catfish have been safely transported at loadings presented in Table 41. Experience will dictate whether or not the suggested loadings are suitable for varying situations. If the trip exceeds 16 hours, it is recom- mended that a complete water change be made during hauling. Catfish also may be transported as sac fry and in the swim- up stage. Most transfers of these stages should be of relatively short duration. Oxy- gen systems alone are satisfactory when fry are hauled, and have some ad- vantages over the use of pumps because suction and spraying turbulence is eliminated. If pumps and spray systems are used, the pump should be operated at a rate low enough to minimize roiling of water in the compart- ments. Sac fry, 5,000 per 1.5 gallons of water, have been shipped success- fully in 1-cubic-foot plastic bags for up to 36 hours. Water temperature should be maintained at the same level fry experienced in the hatchery. Although it may be advantageous to gradually cool the water for shipping some warmwater species, it is not recommended for channel catfish fry. Fingerlings of 1-6 inches ship well for 36 hours. As with salmonids, the number and weight of fish transported varies in proportion to the size of the fish and duration of the shipment. The following guidelines may be of value for hauling channel catfish: (1) Four pounds of 16-inch catfish can be transported per gallon of water at 65T. (2) Loading rates can be increased by 25"o for each 10°F decrease in wa- ter temperature, and reduced proportionately for an increase in tempera- ture. (3) As fish length increases, the pounds of fish per gallon of water can be increased proportionally. For example, a tank holding 1 pound of 4-inch Table 41. pounds of catfish that can be transported per gallon of fi5°F WATER. (SOURCE: MILLARD AND McCRAREN, UNPUBLISHED) NO. OF FISH TRANSIT PERIOD IN HOURS PER POUND 8 12 16 1.0 6.30 5.55 4.80 2.0 5.90 4.80 3.45 4.0 5.00 4.1 2.95 50 3.45 2.50 2.05 125 2.95 2.20 1.80 2.50 2.20 1.75 1.50 .500 1.75 1.65 1.25 1,000 1.25 1.00 0.70 10,000 0.20 0.20 0.20 transportation of live fishes 363 Table 42. pounds of centrarchids that can be distributed per gallon of WATER AT temperatures RANGING BETWEEN fi5° AND H.IT. (AFTER WILSON 19.50.)'' NO. OF FISH SIZE .'VPPRO.XIM.ME NO. POUNDS OF FISH PER LB. (INCHES) OF FISH PER G .M.. PER GAL. 25.0 4.0 25.0 1.00 100.0 3.0 67.0 0.66 400.0 2.0 200.0 0.50 1,000.0 1.0 333.0 0.33 '^Although time is not given by Wilson, the literature indicates minimal problems up to 16 hours at these rates. catfish will safely hold 2 pounds of 8- inch, or 4 pounds of 16-inch fish per gallon of water. (4) If the transportation time exceeds 12 hours, the loading rate should be decreased by 25"n. (5) If the transportation time exceeds 16 hours, loading rates should be decreased by 50% or a complete water change should be arranged. (6) During the winter, hauling temperatures of 45-50°F are preferred, whereas 60-70°F are preferable during summer months. LARGEMOUTH BASS, BLUEGILL, AND OTHER CENTRARCHIDS In keeping with current stocking requirements, centrarchids are transport- ed primarily as small fingerlings at light densities (Table 42). Largemouth bass fingerlings of 6-10 inches can be transported at 2.0 pounds per gallon of water for up to 10 hours without loss. This loading rate was used when several southwestern hatcheries transported larger largemouth bass fingerlings and most trips were considered highly success- ful. Aeration was provided by aerators and bottled oxygen introduced at 0.14—0.21 cubic foot per minute. STRIPED BASS The Fish and Wildlife Service in the southeastern United States hauled striped bass averaging 1,000 per pound at a rate of 0.15 pounds per gallon of water for up to 10 hours with few problems. Fingerlings averaging five per pound were transported at rates of 1.5 pounds per gallon for 10 hours and 0.75 pounds per gallon for 15 hours. Recirculation systems and agita- tors both have been used successfully. The recommended water tempera- ture for hauling striped bass is 55°-65°F. Successful short hauls have been made at higher temperatures. Striped bass averaging 500 per pound have been successfully transported at loadings approaching 0.5 pound per gallon for periods of 19 to 24 hours. 364 fish harchkry management Table 43. pounds of northern pike and walleye ihai can be carried per gallon of water at temperatures between .w" to 6r>°f. (source: raymond a. phillips, personal communicaiion.) no. of fish size pounds of transit period per lb. (inches) fish per gal. ' (hours) (iO.O 3.0 l.M) 8.0 .■")0().() 2.0 O.fif) H.O 1,000.0 1.0 0. ,''),'■) H.O Striped bass fry 1 or 2 days old have been shipped successfully in plastic bags. Very little mortality has been experienced in transporting fry for 48 hours at numbers up to 40,000 per gallon of water. Striped bass less than 2 months old exhibit considerable tolerance when abruptly transferred into waters with temperatures of 44°F to 76°F and salinities of 4 to 12 parts per thousand. This species normally is transported and handled in a 1.0% reconstituted sea-salt solution to reduce stress. Striped bass do not require tempering when transferred either from fresh water to 1% saline or from saline to fresh water. NORTHERN PIKE, MUSKELLUNGE, AND WALLEYE Table 43 suggests loading rates that have proved successful for northern pike and walleye. Muskellunge fry often are transported in small screen boxes placed in the tank of a distribution truck. Fry also have been transported successfully in plastic bags inflated with oxygen. Fingerlings are transported in tanks, either of 250 or 500 gallons capacity; oxygen is bubbled into the tanks but no water circulation is attempted. About 0.5 pound of 10-14-inch finger- lings can be carried per gallon of water, and 1-2 parts per million acrifla- vine is added to the tank to reduce bacterial growth. Stocking Fish It has been an established practice to acclimate fish from the temperature of the transportation unit to that of the environment into which they are stocked, a process called tempering. In the past, temperature was the main reason given for tempering fish. There is some doubt, however, that tem- perature is the only factor involved. Evidence in many cases has failed to demonstrate a temperature shock even though there was a difference of as much as 30°F; changes in water chemistry and dissolved gas levels may be more important than temperature changes. The fish may be subjected to Figure 112. Plastic bag shipment of fish. The container should be at least 4-mil plastic and preferably thicker for catfish and large sunfish. (l) The proper weight of fish is combined with the required amount of water. (2) Fish then are poured into the plastic shipping bag. Any chemicals such as anesthetics or buffers should be added to the water before the fish are introduced. (3) The bag is then filled with oxygen. All the air is first forced out of the bag, which is then refilled with oxygen through a small hole at the top of the bag, or the bag can be bunched tightly around the oxygen hose. Approximately 75"i> of the volume of the bag should be oxygen. The bag then is heat-sealed or the top is twisted tightly and secured with a heavy-duty rubber band. (4) Because cool water can support more fish than warm water, the water temperature in the shipping con- tainer should be kept as cool as the fish will tolerate. If ice is needed it may be placed directly with the fish or in separate bags (arrow) next to the fish con- tainer. In this way the fish and water are cooled simultaneously. (5) Polyurethane foam - inch thick is excellent insulation for shipping, but it is heavier and less efficient than foam. (6) The package then is sealed and prop- erly labelled for shipment. (Photos courtesy Don Toney, Willow Beach National Fish Hatchery, FWS.) 365 366 fish hatchi.ky management Table 44. kecommendkd loadings and ireaimenls im:r siiiimmng lmi iok rainbow or brook iroui l.iod i'lr i'ound). the ccjntalner almosl'ukrl is blair, elsii and wildliee service, unit bi.isiied.) NlMlil.K .SI'WIKS oi- HSU C(JN lAIM.K 1 \ M 1 \ 1 1 1 1 \ (1) Largemouth bass ()-l()() 1 -gallon t libilainer None (2) Largemoulh bass I()5-l.-.() 1 -gallon cubitainer None (3) Largemouth bass 1. '),'")- ,')()() 12 X 2(i-inch, 4- mil plastK bag Ncme (4) Bluegill 0- 100 1 -gallon cubilainer None (5) Bluegill lo.v :-!()() 1 -gallon cubilainer None (6) Bluegill 3(),')-8()() 12 X 2H-in(;h, 4- mil plastii bag None (7) Rainbow or brook trout ()-:-i(i() 12 - 2K-inch, 4- mil plastic bag Newspajjcr (8) Rainbow or brook O-HOO 12 « 24-incli, 4-mil Rigid poly- trout plastic- bag u re thane foam carbon dioxide and oxygen tensions in the shipping water that are not present in the natural environment. Osmotic shock can be a very serious problem, particularly if fish reared in hatcheries with buffered water from limestone formations are stocked into dilute acidic waters. Addition of receiving water to the fish distribution tank before fish are unloaded requires effort, but the benefits will more than justify the effort in many situations. As fish are gradually changed from hauling water to re- ceiving water, they have an opportunity to make some adjustments to their future environment. Flowing water also aids in removing fish from the tank with minimum stress. Shipping Fish In Small Containers Polyethylene bottles have been used to transport small trout, especially by horseback to back-country areas. After the bottle is filled with water, fish, ice, and oxygen, it is placed in an insulated container for shipment. Plastic bags frequently are used to ship small numbers of tropical fish, warmwater fish, and trout (Figure 112). Upon arrival at the destination the plastic bags should be allowed to float unopened in a shaded area of the re- ceiving water supply for about 30 minutes to acclimate the fish. There are varying and sometimes conflicting opinions regarding fish loads, water volume, the use of buffers, and container sizes to be used in shipping fish. Some suggested shipping loads are presented in Table 44. The following excerpts from private communications collected at the TRANSPORTATION OF LIVE FISHES 367 LARGEMOUTH BASS (1,500 FISH PER POUND), BLUEGILLS (2,100 PER POUND), AND PURE OXYGEN. SHIPPING TIME SHOULD NOT EXCEED 21 HOURS. (SOURCE: ALAN B. PAR 1 .S PER GRAMS MILLILITERS GALLONS POUNDS MILLION TRIS HLFFER lERTIARV OF U ATER OF ICE AC'RIFLAVIN KM [)H AMVL ALCOHOL SPECIES ().,') 0 2.5 0 0 (1) 0.5 0 2.5 «i 1.5 (2) 1.5 0 2.5 18 4.5 (3) 0.5 0 2.5 0 0 (4) 0.5 0 2.5 (') 1.5 (5) 1.5 0 2.5 IK 4.5 (6) 1.0 12 0 12 3.0 (7) 0.75 4 0 12 2.0 (8) Warmwater Fish Cultural Development Center, San Marcos, Texas, may also be of interest to fish culturists faced with determining a suitable proto- col for container shipment of fish. All comments relate to containers with one atmosphere of pure oxygen: . . . Good survival was achieved shipping 100 bluegill sunfish (l,200 fish per pound) in ^ gallon of water. If shipment is 30 hours or less, we believe it safe to ship 200 fish in -; gallon of water in a one-gallon cubitainer. . . . We had excellent survival on mail distribution. We used ^ gallon water per one-gallon cubitainer, an oxygen overlay, and largemouth bass going 900 per pound. Duration of shipment was 24 hours. . . . Amyl alcohol slightly increased survival time for all species tested when used at rates of 2.0-3.0 ml per gallon of water. This chemical appears to tranquilize the fish, thereby reducing metabolism. . . . When shipping in plastic bags we seldom use ice with largemouth bass, and never with northern pike and walleye. . . . We load each bag or box with 50,000 northern pike fry, 70,000 walleye fry, or up to 600 small largemouth bass fingerlings. We have experienced mortalities in shipments when using V-bottom plastic bags. All species will hold for 24 hours but we prefer to get the fish out of the bag in 4-10 hours. . . . Catfish sac fry were shipped by air from Dallas to Honolulu, Hawaii, for several years with good success. We used 1 -cubic-foot plastic cubi- tainers with 12 pounds of water to 6 ounces of fry. Shipments arriving within 24 hours usually had losses of 5"m or less. 368 FISH HATCHERY MANAGEMENT Bibliography Anonymous. 1883. I ransportation of live fish. English translation by H. Jacobson, taken from the International P'ishery Exposition, Berlin 1880. Bulletin of the US Fish Com- mission 2:9.')- 102. li)3i). Distribution highlights in Pennsylvania. Progressive Fish-Culturist (4S) :34-3.'). 19F>{). A note regarding air shipment of largemouth bass fingerlings from Oklahoma to Colorado. Progressive Fish-Culturist 12(l):28. 1955. Test of planting walleye fry by plane. Progressive Fish-Culturist 17(3):128. 1971. Live hauler. Catfish Farmer 3 (5): 19-21. 1973. "300,000 fingerlings per load." Fish Farming Industries, 4(2):31. BabCOCK, W. H., and G. Post. 1967. An evaluation of water conditioning systems for fish dis- tribution tanks. Colorado Department of Fish, Game and Parks Special Report 16:1-9. BaSU, S. P. 1959. Active respiration of fish in relation to ambient concentrations of oxygen and carbon dioxide. Journal of the Fisheries Research Board of Canada lfi(2) :175-212. Beamish, F. H. W. 19(i4. Influence of starvation on standard and routine oxygen consump- tion. Transactions of the American Fisheries Society 93(l): 103-107. Bell, G. R. 19fi4. A guide to the properties, characteristics and uses of some general anesthet- ics for fish. Fisheries Research Board of Canada Bulletin 148. BeZDEK, Francis H. 1957. Sodium Seconal as a sedative for fish. Progressive Fish-Culturist 19 (3): 130. BiTZER, Ralph, and Alfred Burnham. 1954. A fish distribution unit. Progressive Fish- Culturist 16(l):35. Black, E. C, and I. Barrett. 1957. Increase in levels of lactic acid in the blood of cutthroat and steelhead trout following handling and live transportation. Canadian Fish Cultu- rist 20:13-24. Bonn, Edward W., William M. Bailey, Jack D. Bayless, Kim E. Erickson, and Robert E. Stevens. 1976. Guidelines for striped bass culture. Striped Bass Committee, South- ern Division, American Fisheries Society, Bethesda, Maryland. 103 p. BrOCKWAY, D. R. 1950. Metabolic products and their effects. Progressive Fish-Culturist 12 (3): 127- 129. Burrows, R. E. 1937. More about fish planting. Progressive Fish-Culturist (34):21-22. Burton, D., and A. Spehar. 1971. A re-evaluation of the anerobic end products of freshwater fish exposed to environmental hypoxia. Comparative Biochemistry and Physiology 40A;945-954. Caillouet, Charles W., Jr. 19()7. Hyperactivity, blood lactic acid and mortality in channel catfish. Pages 898-915 in Iowa State University Agricultural and Home Economical Experiment Station, Research Bulletin 551, Ames. Collins, James L., and Andrew M. Hulsey. 1967. Reduction of threadfin shad hauling mor- tality by the use of MS-222 and common salt. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 18:522-524. COPELAND, T. H. 1947. Fish distribution units. Progressive Fish-Culturist 9(4) :193-202. Culler, C. F. 1935. "Comments from our readers." Progressive Fish-Culturist (7):7-8. Davis, James T. 1971. Handling and transporting egg, fry, and fish. Proceeding of the Conference on Production and Marketing of Catfish in the Tennessee Valley, Tennes- see Valley Administrations:40-42. DoBiE, John, O. Lloyd Meehean, S. F. Snieszko, and George N. Washburn. 1956. Rais- ing bait fishes. US Fish and Wildlife Service Circular 35:124. Downing, K. M., and J. C. Merkens. 1955. The influence of dissolved-oxygen concentration on the toxicity of unionized ammonia to rainbow trout. Annals of Applied Biology 43:243. TRANSPORTATION OF LIVE FISHES 369 Eddy, F. B., and R. I. G. Morgan. 1969. Some effect of carbon dioxide on the blood of rainbow trout, Salmo gairdneri Richardson. Journal of Fish Biology l(4):361-372. Falconer, D. D. 19fi4. Practical trout transport techniques. Progressive Fish-Culturist 26(2):51-.')8. Feast, C. N., and C. E. Hagie. 1948. Colorado's glass fish tank. Progressive Fish-Culturist 10(l):29-30. Fromm, p. O., and J. R. Gillette. 1968. Effect of ambient ammonia on blood ammonia and nitrogen excretion of rainbow trout, Salmo gairdneri. Comparative Biochemistry and Physiology 26:887-896. Fry, F. E. J. 19.^7. The aquatic respiration of fish. Pages 163 in M. E. Brown, editor. Phy- siology of fishes, volume 1. Academic Press, New York. , and K. NORRIS. 1962. The transportation of live fish. Pages .')9.')-6()9 in George Borgstrom, editor. Fish as food, volume 2, nutrition, sanitation and utilization. Academic Press, New York. FuQLA, Charles L., and Hi bf.rt C. Topel. 1939. Transportation of channel catfish eggs and fry. Progressive Fish-Culturist (46): 19-21. Garlick, Lewis R. 1950. The helicopter in fish-planting operations in Olympic National Park. Progressive Fish-Culturist 12(2);72-76. Greene, A. F. C. 19.56. Oxygen equipment for fish transportation. Progressive Fish-Culturist 18(l):47-48. Haskell, D. C. 1941. An investigation on the use of oxygen in transporting trout. Transac- tions of the American Fisheries Society 70:149-160. , and R. O. D.aV'IES. 1958. Carbon dioxide as a limiting factor in transportation. New York Fish and Game Journal 5(2):17,5-183. Heffernan, Bern.^RD E. 1973. Intensive catfish culture "cuts its teeth" in Kansas. Fish Farm- ing Industries 4(5):8-ll. Henegar, Dale L., and Donald C. Dlerre. 1964. Modified California fish distribution units for North Dakota. Progressive Fish-Culturist 26(4):188-19(). Holder, C. F. 1908. A method of transporting live fishes. Bulletin of the US Bureau of Fisheries 28(2): 1005- 1007. HORTON, H. F. 1956. An evaluation of some physical and mechanical factors important in reducing delayed mortality of hatchery reared rainbow trout. Progressive Fish-Culturist 18(1):3-14. Itazawa, Y. 1970. Characteristics of respiration of fish considered from the arterio- venous difference of oxygen content. Bulletin of the Japanese Society of Scientific Fisheries 36(6):571-577. Johnson, F. C. 1972. Fish transportation improvement — phase II. Final report prepared for State of Washington, Department of Fisheries, Olympia. 63 p. Johnson, Leon D. 1972. Musky survival. Wisconsin Conservation Bulletin, May-June:8-9. Johnson, S. K. 1979. Transport of live fish. Report FDDL-F14, Texas Agricultural Experi- mental Service, Department of Wildlife and Fisheries Science, College Station, Texas. 13 p. Keil, W. M. 1935. Better stocking methods. Progressive Fish-Culturist (9):l-6. Kingsbury, O. R. 1949. The diffusion of oxygen in fish tanks. Progressive Fish-Culturist ll(l):24. Klontz, G. W. 1964. Anesthesia of fishes. Pages 14-16 in Proceedings of the symposium on experimental animal anesthesiology. Brooks Air Force Base. Leach, G. C. 1939. Artificial propogation of brook trout and rainbow trout with notes on three other species. US Department of Interior, Fisheries Document 955, Washington, D.C. 74 p. Lefever, Lorin. 1939. A new water aerator. Progressive Fish-Culturist (45):54-56. 370 FISH HATCHERY MANAGEMENT LrriRirz, Earl, and Robert C. Lewis. 1976. Trout and salmon culture (hatchery methods). California Department of F'ish and Game, Fish Bulletin lfi4. 197 p. Lewis, Wu.I.IAM M., and Michael Bender. 19()(). Heavy mortality of golden shiners during harvest due to a bacterium of the genus Airoiiiunas. Progressive Fish-Culturist 22(1):I1 N. Llo^D, R. 1961. I'he toxicity of ammonia to rainbow trout. Water and Waste Treatment Journal 8:278-279. Maloy, Charles R. \[)(VA. Hauling channel catfish fingerlings. Progressive Fish-Culturist 25(4):21 1-212. Marathe, V. B., N. V. Hlilgol, and S. G. Path.. 197."). Hydrogen peroxide as a source of oxygen supply in the transport of fish fry. Progressive Fish-Culturist 37(2):117. Maxwell, John M., and Robert W. Thoesen. 196,'). Lake Powell stocking story. Progressive Fish-Culturist 27 (3): 11.')- 120. Mazlranich, John J. 1971. Basic fish husbandry distribution. US Bureau of Sport Fisheries and Wildlife, Washington, D.C. 53 p. (Mimeo.) McCraren, J. P., and R. W. JONES. 1978. Suggested approach to computing and reporting loading densities for fish transport units. Progressive Fish-Culturist 40(4):169. , and Jack L. Millard. 1978. Transportation of warmwater fishes. Pages 43-88 (/; Manual of fish culture, Section G, LIS Fish and Wildlife Service, Washington, D.C. McFarland, W. N. 19(i0. The use of anesthetics for the handling and the transport of fishes. California Fish and Game 46f4):4t)7-431. Meehan, W. R., and L. Revei. 1962. The effect of tricane methane sulfonate (MS-222) and/or chilled water on oxygen consumption of sockeye salmon fry. Progressive Fish- Culturist 24(4):18,S-187. Meyer, Fred P., Kermit E. Sneed, and Pall T. Eschmeyer, editors. 1973. Second report to the fish farmers. L^S Bureau of Sport Fisheries and Wildlife, Resource Publication 113, US Fish and Wildlife Service, Washington, D.C. 123 p. MooRE, T. J. 1887. Report on a successful attempt to introduce living soles to America. Bul- letin of the US Fish Commission 7(l);l-7. Moss, D. D., and D. C. Scolt. 1961. Dissolved oxygen requirements for three species of fish. Transactions of the American Fisheries Society 90(4):377-393. Miller, R. B. 19.')1. Survival of hatchery-reared cutthroat trout in an Alberta stream. Trans- actions of the American Fisheries Society 81:35-42. NORRIS, K. S., F. Brocato, and F. Calandrino. 1960. A survey of fish transportation methods and equipment. California Fish and Game 46(l):5-33. Olson, K. R., and P. O. Fromm. 1971. Excretion of urea by two teleosts exposed to different concentrations of ambient ammonia. Comparative Biochemistry and Physiology 40A(4):999-1007. Olson, Ralph H. 1940. Air conditioning fish distribution tanks. Progressive Fish-Culturist (.52): 16-17. OSBORN, P. E. 19.51. Some experiments on the use of thiouracil as an aid in holding and transporting fish. Progressive Fish-Culturist 13(2):75-78. Otwell, W. S., and J. V. Merriner. 197,5. Survival and growth of juvenile striped bass, Morone saxalilis, in a factorial experiment with temperature, salinity and age. Transac- tions of the American Fisheries Society 104(3) :560-566. Phillips, A. M., and D. R. Brockway. 1954. Effect of starvation, water temperature and sodium amytal on the metabolic rate of brook trout. Progressive Fish-Culturist 16(2):6,5-68. Phillips, Arihur M., Jr. 196(). Outline of courses given at In-Service Training School, Cort- land, New York, part B, methods for trout culture. US Fish and Wildlife Service, Cort- land, New York. 100 p. TRANSPORTATION OF LIVE FISHES 371 Powell, Naihan A. 1!)70. Striped bass in air shipment. Progressive Fish-Culturist 32(l):18 pp. Reese, Al. 1953. Use of hypnotic drugs in transporting trout. California Department of Fish and Game, Sacramento. 10 p. (Mimeo.) SCHLLTZ, F. H. 195fi. Transfer of anesthetized pike and yellow walleye. Canadian Fish Cultu- rist 18:1 -.'i. Se.ALE, a. 1910. The successful transference of black bass into the Philippine Island with notes on the transportation of live fish long distances. Philippine Journal of Science, Section B 5(3): 153- 159. ShEBLEY, W. H. 1!)27. History of fish planted in California. California Fish and Game 13(3):163-i74. S.MITH, Ch.ARLIE E. 1978. Transportation of saimonid fishes. Pages 9 41 in Manual of fish cul- ture. Section G, US Fish and Wildlife Service, Washington, D.C. Smuh, H. W. 1929. The excretion of ammonia and urea by the gills of fish. Journal of Bio- logical Chemistry 81:727-742. Snow, J. R., R. O. Jones, and W. A. Rogers. 19fi4. Training manual for warmwater fish cul- ture. US Bureau of Sport Fisheries and Wildlife, National Fish Hatchery, Marion, Ala- bama. 4ti0 p. Srini\ ASAN, R., P. I. Chacko, and A. P. Valsan. 1955. A preliminary note on the utility of sodium phosphate in the transport of fingerlings of Indian carps. Indian Journal of Fisheries 2(l):77-83. Stone, Livingston. 1874. Report on shad hatching operations. US Commission of Fish and Fisheries, Commissioner's Report, Appendix C:413-41fi. Sykes, Ja.mes E. 1950. A method of transporting fingerling shad. Progressive Fish-Cuiturist 12 (3): 153- 159. 1951. The transfer of adult shad. Progressive Fish-Culturist 13(l):45-46. TrL'SSELL, R. p. 1972. The percent of un-ionized ammonia in aqueous ammonia solutions at different pH levels and temperatures. Journal of the Fisheries Research Board of Cana- da 29(10):1505-1.507. Waite, Di.XON. Undated. Use of electric and hydraulic systems on fish transportation units in Pennsylvania. Pennsylvania Fish Commission, Benner Springs Research Station. 3 p. (Mimeo.) Webb, Roberi T. 1958. Distribution of bluegill treated with tricaine methanesulfonate (MS-222). Progressive Fish-Culturist 20(2):69-72. Wedemeyer, G. 1972. Some physiological consequences of handling stress in the juvenile coho salmon [Oncorhynchus kisutch) and steelhead trout [Salmo gairdneri). Journal of the Fisheries Research Board of Canada 2!)( 12) : 1 780- 1783. , and J. Wood. 1974. Stress as a predisposing factor in fish diseases. US Fish and Wildlife Service, Fish Disease Leaflet Number 38. 8 p. Weibe, a. H., a. M. McGavock, A. C. Fuller, and H. C. Marcis. 1934. The ability of freshwater fish to extract oxygen at different hydrogen ion concentrations. Phys- iological Zoology 7(3):435-448. Wilson, Albert J. 1950. Distribution units for warmwater fish. Progressive Fish-Culturist 12(4):211-213. Appendices Appendix xV English- Metric and Temperature Conversion Tables Table A-1. english-metric conversions. ENGLISH METRIC 1 inch 0.39 inch 1 foot (12 inches) 1 yard (3 feet) 1.09 yards 1 square inch 0.15 square inch 1 square foot (144 square inches) 1 square yard (9 square feet) 1.20 square yards 1 acre (4,840 square yards) 2.47 acres 1 acre-foot (43,560 cubic feet) 1 English ton (2,000 pou 1.10 English tons nds) 1 cubic foot/second 0.035 cubic foot/second 1 cubic foot/minute 0.035 cubic foot/minute 1 gallon/minute 0.264 gallons/minute Length Area Volume Weight Flow rate 2.54 centimeters 1 centimeter (lO millimeters) 30.5 centimeters 0.91 meters 1 meter (lOO centimeters) 6.45 square centimeters 1 square centimeter 929 square centimeters 0.84 square meters 1 square meter (10,000 square centimeters) 0.40 hectares 1 hectare (10,000 square meters) 1,233.6 cubic meters 0.91 metric ton 1 metric ton ( 1,000 kilograms) 28.32 liters/second 1 liter/second 28.32 liters/minute 1 liter/minute 3.785 liters/minute 1 liter/minute 375 376 fish hatchery management Table A-2. temperatures-fahrenheit to centigrade, temperature in degrees fahrenheit is expressed in the left column and in the top row; the corresponding temperature in degrees centigrade is in the body of TABLE. TEMP.T. 0 1 2 3 4 F) 6 7 8 •J 30 1.1 0.6 0.0 0.6 1.1 1.7 2.2 2.8 3.3 3.9 40 4.4 5.0 5.6 6.1 6.7 7.7 7.8 8.3 8.9 9.4 50 10.0 10.6 11.1 11.7 12.2 12.8 1 3.3 13.9 14.4 15.0 60 1,1. fi 16.1 16.7 17.2 17.8 18.3 18.9 19.4 20.0 2().fi 70 21.1 21.7 22.2 22.8 23.3 23.9 24.4 25.0 25.6 26.1 80 26.7 27.2 27.8 28.3 28.9 29.4 30.0 30.6 31.1 31.7 90 32.2 32.8 33.3 33.9 34.4 35.0 35.6 36.1 36.7 37.2 Table A-4. volumetric and weight equivalents of water in metric and (source: charles l. sowards unpublished.) example: to find the weight in column; then read horizontally to find 3.78.s in the "kilogram" column, gram of water at 4°c and on an atmospheric pressure of 760 mm mercury. CUBIC CUBIC YARD FOOT CUBIC INCH GALLON QU.^RT PINT (1) 1.309 35.361 61,095 264.5 1 ,058 2,116 (2) 0.001 0.035 61.09 0.264 1 .058 2.116 (3) — — 0.061 — 0.001 0.002 (4) 1 27 46,656 201.98 807.9 1,616 (5) 0.037 1 1,728 7.48 29.92 59.85 (6) 0.005 0.134 231 1 4 8 (7) 0.001 0.033 57.75 0.25 1 2 (8) 0.001 0.017 28.88 0.125 0.5 1 (9) — 0.016 27.71 0.12 0.48 0.96 (10) — 0.001 1.805 0.008 0.031 0.062 (11) — 0.001 1.732 0.007 0.03 0.06 (12) — — 1 0.004 0.017 0.035 (13) — — 0.061 — 0.001 0.002 CONVERSION lABLES 377 Table A-3. temperatures-centigrade to Fahrenheit, temperature in DEGREES centigrade IS EXPRESSED IN THE LEFT COLUMN AND IN THF. TOP ROW; THE CORRESPONDING TEMPERATURE IN DEGREES FAHRENHEIT IS IN THE BODY OF TABLE. TEMP° C. 0 1 2 3 4 5 6 7 8 9 0 32.0 33.H 35.6 37.4 39.2 41.0 42.8 44.(i 46.4 48.2 10 50.0 51.8 53.6 55.4 57.2 59.0 60.8 62.6 64.4 66.2 20 68.0 69.8 71.6 73.4 75.2 77.0 78.8 80.6 82.4 84.2 30 8fi.O 87.8 89.6 !»1.4 93.2 95.0 For intermediate temperatures or those exceeding the range of the tables, the following for- mulas may be used: F - 32 F = 1.8XC + 32, C = ^ ^ ENGLISH SYSTEMS. ALL FIGURES ON A HORIZONTAL LINE ARE EQUIVALENT VALUES. KILOGRAMS OF ONE GALLON OF WATER, FIND THE NUMBER ONE IN THE "GALLON" METRIC COMPUTATIONS WERE BASED ON 1 LITER BEING THE VOLUME OF 1 KILO- FLL II) CLBIC LITER OR MILLILITER OUNCE METER KILOGR.'^M OR GRAM OUNCE (WT) POUND 33,854 1 1,000 1,000,000 35,273 2,205 1 33.85 0.001 1 1,000 35.27 2.204 (2) 0.034 — 0.001 1 0.035 0.002 (3) 25,853 0.764 764.5 764,559 26,937 1,683.6 (4) 957.5 0.028 28.317 28,322 997.7 62.428 (5) 128 0.004 3.785 3,785 133.4 8.335 (6) 32 0.001 0.946 946.2 33.34 2.084 (7) 16 — 0.473 473.1 16.67 1.042 (8) 15.36 — 0.454 453.6 16 1 (9) 1 0.03 29.57 1.042 0.065 (10) 0.96 0.028 28.35 1 0.062 (11) 0.554 0.016 16.37 0.577 0.036 (12) 0.034 — 0.001 1 0.035 0.002 (13) B Appendix Ammonia Ionization Table B-1. percent un-ionized ammonia (NH3) in aqueous ammonia EMERSON l!t74. AQUEOUS AMMONIA EQUILIBRIUM CALCULATIONS, TECHNICAL TEMPERATURE,°C PH 0.0 1.0 2.0 3.0 4.0 5.0 6.0 0.00827 0.00899 0.00977 0.0106 0.0115 0.0125 6.1 0.0104 0.0113 0.0123 0.0134 0.0145 0.0157 6.2 0.0131 0.0143 0.0155 0.0168 0.0183 0.0198 6.3 0.0165 0.0179 0.0195 0.0212 0.0230 0.0249 6.4 0.0208 0.0226 0.0245 0.0267 0.0189 0.0314 6.5 0.0261 0.0284 0.0309 0.0336 0.0364 0.0395 6.6 0.0329 0.0358 0.0389 0.0422 0.0459 0.0497 6.7 0.0414 0.0451 0.0490 0.0532 0.0577 0.0626 6.8 0.0521 0.0567 0.0616 0.0669 0.0727 0.0788 6.9 0.0656 0.0714 0.0776 0.0843 0.0915 0.0992 7.0 0.0826 0.0898 0.0977 0.106 0.115 0.125 7.1 0.104 0.113 0.123 0.133 0.145 0.157 7.2 0.131 0.142 0.155 0.168 0.182 0.198 7.3 0.165 0.179 0.195 0.211 0.229 0.249 7.4 0.207 0.225 0.245 0.266 0.289 0.313 7.5 0.261 0.284 0.308 0.335 0.363 0.394 7.6 0.328 0.357 0.388 0.421 0.457 0.495 7.7 0.413 0.449 0.488 0.529 0.574 0.623 7.8 0.519 0.564 0.613 0.665 0.722 0.783 7.9 0.652 0.709 0.770 0.836 0.907 0.983 8.0 0.820 0.891 0.968 1.05 1.14 1.23 8.1 1.03 1.12 1.22 1.32 1.43 1.55 8.2 1.29 1.41 1.53 1.65 1.79 1.94 8.3 1.62 1.76 1.91 2.07 2.25 2.43 8.4 2.03 2.21 2.40 2.60 2.81 3.04 8.5 2.55 2.77 3.00 3.25 3.52 3.80 8.6 3.19 3.46 3.75 4.06 4.39 4.74 8.7 3.98 4.31 4.67 5.05 5.46 5.90 8.8 4.96 5.37 5.81 6.28 6.78 7.31 8.9 6.16 6.67 7.20 7.78 8.39 9.03 9.0 7.64 8.25 8.90 9.60 10.3 11.1 378 AMMONIA IONIZATION 379 SOLUTIONS. (SOURCE: THURSTON, ROBERT V., ROSEMARIE RUSSO, AND KENNETH REPORT 74-1, MONTANA .STATE UNIVERSITY, BOZEMAN, MONTANA. TEMPERATURE,°C PH 6.0 7.0 8.0 9.0 10.0 11.0 6.0 0.0136 0.0147 0.0159 0.0172 0.0186 0.0201 6.1 0.0171 0.0185 0.0200 0.0217 0.0235 0.0254 6.2 0.0215 0.0233 0.0252 0.0273 0.0295 0.0319 6.3 0.0270 0.0293 0.0317 0.0344 0.0372 0.0402 6.4 0.0340 0.0369 0.0400 0.0432 0.0468 0.0506 6.5 0.0429 0.0464 0.0503 0.0544 0.0589 0.0637 6.6 0.0539 0.0585 0.0633 0.0685 0.0741 0.0801 6.7 0.0679 0.0736 0.0797 0.0862 0.0933 0.101 6.8 0.0855 0.0926 0.100 0.109 0.117 0.127 6.9 0.108 0.117 0.126 0.137 0.148 0.160 7.0 0.135 0.147 0.159 0.172 0.186 0.201 7.1 0.170 0.185 0.200 0.216 0.234 0.253 7.2 0.214 0.232 0.252 0.272 0.294 0.318 7.3 0.270 0.292 0.316 0.342 0.370 0.400 7.4 0.339 0.368 0.398 0.431 0.466 0.504 7.5 0.427 0.462 0.,501 0.542 0.586 0.633 7.6 0.537 0.582 0.629 0.681 0.736 0.796 7.7 0.675 0.731 0.791 0.856 0.925 1.00 7.8 0.848 0.919 0.994 1.07 1.16 1.26 7.9 1.07 1.15 1.25 1.35 1.46 1.58 8.0 1.34 1.45 1.57 1.69 1.83 1.97 8.1 1.68 1.82 1.96 2.12 2.29 2.47 8.2 2.10 2.28 2.46 2.66 2.87 3.09 8.3 2.63 2.85 3.08 3.32 3.58 3.86 8.4 3.29 3.56 3.84 4.15 4.47 4.82 8.5 4.11 4.44 4.79 5.16 5.56 5.99 8.6 5.12 5.53 5.96 6.42 6.91 7.42 8.7 6.36 6.86 7.39 7.95 8.54 9.17 8.8 7.88 8.48 9.12 9.80 10.5 11.3 8.9 9.72 10.5 11.2 12.0 12.9 13.8 9.0 11.9 12.8 13.7 14.7 15.7 16.8 380 kish hatchery management Table B-1. continued. TEMPERATURE,°C pH 12.0 13.0 14,0 i:..() 16.0 17.0 (i.O 0.0218 0.0235 0.0254 0.0274 0.0295 0.0318 6.1 0.0274 0.0296 0.0319 0.0345 0.0372 0.0401 6.2 0.0345 0.0373 0.0402 0.0434 0.0468 0.0504 6.3 0.0434 0.0469 0.0506 0.0546 0.0589 0.0635 6.4 0.0547 0.0590 0.0637 0.0687 0.0741 0.0799 6.5 0.0688 0.0743 0.0802 0.0865 0.0933 0.101 6.6 0.0866 0.0935 0.101 0.109 0.117 0.127 6.7 0.109 0.118 0.127 0.137 0.148 0. 1 .59 6.8 0.137 0.148 0.160 0.172 0.186 0.200 6.9 0.173 0.186 0.201 0.217 0.234 0.252 7.0 0.217 0.235 0.253 0.273 0.294 0.317 7.1 0.273 0.295 0.319 0.344 0.370 0.399 7.2 0.344 0.371 0.401 0.432 0.466 0.502 7.3 0.433 0.467 0.504 0.543 0.586 0.631 7.4 0.544 0.587 0.633 0.683 0.736 0.793 7.5 0.684 0.738 0.796 0.859 0.925 0.996 7.6 0.859 0.927 1.00 1.08 1.16 1.25 7.7 1.08 1.16 1.26 1.35 1.46 1.57 7.8 1.36 1.46 1.58 1.70 1.83 1.97 7.9 1.70 1.83 1.98 2.13 2.29 2.47 8.0 2.13 2.30 2.48 2.67 2.87 3.08 8.1 2.67 2.87 3.10 3.33 3.58 3.85 8.2 3.34 3.59 3.87 4.16 4.47 4.80 8.3 4.16 4.48 4.82 5.18 5.56 5.97 8.4 5.19 5.58 5.99 6.44 6.91 7.40 8.5 6.44 6.92 7.43 7.97 8.54 9.14 8.6 7.98 8.56 9.18 9.83 10.5 11.2 8.7 9.84 10.5 11.3 12.1 12.9 13.8 8.8 12.1 12.9 13.8 14.7 15.7 16.7 8.9 14.7 15.7 16.8 17.9 19.0 20.2 9.0 17.9 19.0 20.2 21.5 22.8 24.1 AMMONIA IONIZATION 381 TEMPERATURE,°C PH 18.0 19.0 20.0 21.0 22.0 23.0 6.0 0.0343 0.0369 0.0397 0.0427 0.0459 0.0493 6.1 0.0431 0.0465 0.0500 0.0.538 0.0578 0.0621 6.2 0.0543 0.0585 0.0629 0.0677 0.0727 0.0782 6.3 0.0684 0.0736 0.0792 0.0852 0.0916 0.0984 6.4 0.0860 0.0926 0.0997 0.107 0.115 0.124 6.5 0.108 0.117 0.125 0.135 0.145 0.156 6.6 0.136 0.147 0.158 0.170 0.183 0.196 6.7 0.172 0.185 0.199 0.214 0.230 0.247 6.8 0.216 0.232 0.250 0.269 0.289 0.310 6.9 0.272 0.292 0.315 0.338 0.364 0.390 7.0 0.342 0.368 0.396 0.425 0.457 0.491 7.1 0.430 0.463 0.498 0.535 0.575 0.617 7.2 0.540 0.582 0.626 0.673 0.723 0.776 7.3 0.679 0.731 0.786 0.845 0.908 0.975 7.4 0.854 0.919 0.988 1.06 1.14 1.22 7.5 1.07 1.15 1.24 1.33 1.43 1.54 7.6 1.35 1.45 1.56 1.67 1.80 1.93 7.7 1.69 1.82 1.95 2.10 2.25 2.41 7.8 2.12 2.28 2.44 2.63 2.82 3.02 7.9 2.65 2.85 3.06 3.28 3.52 3.77 8.0 3.31 3.56 3.82 4.10 4.39 4.70 8.1 4.14 4.44 4.76 5.10 5.47 5.85 8.2 5.15 5.53 5.92 6.34 6.79 7.25 8.3 6.40 6.86 7.34 7.86 8.39 8.96 8.4 7.93 8.49 9.07 9.69 10.3 11.0 8.5 9.78 10.5 11.2 11.9 12.7 13.5 8.6 12.0 12.8 13.7 14.5 15.5 16.4 8.7 14.7 15.6 16.6 17.6 18.7 19.8 8.8 17.8 18.9 20.0 21.2 22.5 23.7 8.9 21.4 22.7 24.0 25.3 26.7 28.2 9.0 25.5 27.0 28.4 29.9 31.5 33.0 382 FISH HATCHERY MANAGEMENT Table B-1. continued. TEMPERATURE, °C PH 24.0 25.0 26.0 27.0 28.0 29.0 30.0 6.0 0.0530 0.0569 0.0610 0.0654 0.0701 0.0752 0.0805 6.1 0.0667 0.0716 0.0768 0.0824 0.0883 0.0946 0.101 6.2 0.0839 0.0901 0.0967 0.104 0.111 0.119 0.128 6.3 0.106 0.113 0.122 0.130 0.140 0.1,50 0.160 6.4 0.133 0.143 0.153 0.164 0.176 0.189 0.202 6.5 0.167 0.180 0.193 0.207 0.221 0.237 0.254 6.6 0.211 0.226 0.242 0.260 0.279 0.299 0.320 6.7 0.265 0.284 0.305 0.327 0.351 0.376 0.402 6.8 0.333 0.358 0.384 0.411 0.441 0.472 0.506 6.9 0.419 0.450 0.483 0.517 0.554 0.594 0.636 7.0 0.527 0.566 0.607 0.651 0.697 0.747 0.799 7.1 0.663 0.711 0.763 0.818 0.876 0.938 1.00 7.2 0.833 0.894 0.958 1.03 1.10 1.18 1.26 7.3 1.05 1.12 1.20 1.29 1.38 1.48 1.58 7.4 1.31 1.41 1.51 1.62 1.73 1.85 1.98 7.5 1.65 1.77 1.89 2.03 2.17 2.32 2.48 7.6 2.07 2.22 2.37 2.54 2.72 2.91 3.11 7.7 2.59 2.77 2.97 3.18 3.40 3.63 3.88 7.8 3.24 3.47 3.71 3.97 4.24 4.53 4.84 7.9 4.04 4.33 4.63 4.94 5.28 5.64 6.01 8.0 5.03 5.38 5.75 6.15 6.56 7.00 7.46 8.1 6.26 6.69 7.14 7.62 8.12 8.65 9.21 8.2 7.75 8.27 8.82 9.40 10.0 10.7 11.3 8.3 9.56 10.2 10.9 11.6 12.3 13.0 13.8 8.4 11.7 12.5 13.3 14.1 15.0 15.9 16.8 8.5 14.4 15.3 16.2 17.2 18.2 19.2 20.3 8.6 17.4 18.5 19.6 20.7 21.8 23.0 24.3 8.7 21.0 22.2 23.4 24.7 26.0 27.4 28.8 8.8 25.1 26.4 27.8 29.2 30.7 32.2 33.7 8.9 29.6 31.1 32.7 34.2 35.8 37.4 39.0 9.0 34.6 36.3 37.9 39.6 41.2 42.9 44.6 Appendix c Volumes and Capacities of Circular Tanks Table C-1. WATER VOLUMES (CUBIC FEET) AND CAPACITIES (US GALLONS) OF CIR- CULAR TANKS FILLED TO A 1-FOOT DEPTH. a,b,c TANK VOLUME TANK VOLUME DIAMETER (CUBIC CAPACITY DIAMETER (CUBIC CAPACITY (FEET) FEET) (GALLONS) (FEET) FEET) (GALLONS) 1.00 0.785 5.87 11.0 95.0 711 1.50 1.77 13.2 11.5 104 777 2.00 3.14 23.5 12.0 113 845 2.,W 4.91 36.7 12.5 123 918 3.00 7.07 52.9 13.0 133 993 3.50 9.62 72.0 13.5 143 1,070 4.00 12.6 94.0 14.0 154 1,1,50 4.50 15.9 119 14.5 165 1,240 5.00 19.6 147 15.0 177 1,320 5.50 23.8 178 15.5 189 1,410 6.00 28.3 212 16.0 201 1,.500 6.50 33.2 248 16.5 214 1,600 7.00 38.5 288 17.0 227 1,700 7.. 50 44.2 330 17.5 241 1,800 8.00 .50.1 376 18.0 254 1,900 8.50 56.8 424 18.5 269 2,010 9.00 63.6 476 19.0 284 2,120 9.50 70.9 530 19.5 299 2,230 10.0 78.5 588 20.0 314 2,3.50 10.5 86.6 641 For water depths less or greater than 1 foot, multiply the tabulated volumes and capacities by the actual depth in feet. For tanks larger than 20 feet in diameter, multiply the volume and capacity of a tank one-half its diameter by four. A 30-foot diameter tank, for example, has a volume of four times the volume of a 15-foot tank. For intermediate tank sizes, volume = 3.14 x ( -j diameter) x water depth; capacity = volume X 7.48. 383 Appendix D Use of Weirs to Measure Flow The discharge of water through a hatchery channel can be measured easily if a Cippoletti or a rectangular weir (Figure D-l) is built into the channel. The only measurement needed is that of the water head behind the weir; the head is the height the water surface above the crest of the weir itself. Reference of this head to a calibration chart (Table D-l) gives the corresponding discharge in gallons per minute. Water-flow determinations will be inaccurate if the head is measured at the wrong point or if the weir has not been constructed carefully. The fol- lowing considerations must be met if weir operation is to be successful. (1) The head must be measured at a point sufficiently far behind the weir. Near the weir, the water level drops as water begins its fall over the weir crest. The head never should be measured closer to the weir than 2 2 times the depth of water flowing over the crest. For example, if 2 inches of water are flowing over the weir crest, the head should be meas- ured 5 inches or more behind the weir. A practical measuring technique is to drive a stake into the channel bottom so that its top is exactly level with the weir crest. Then, the head can be measured with a thin ruler as the depth of water over the stake. A ruler also can be mounted permanently on the side of a vertical channel wall behind the weir, if such a wall has been constructed. (2) The weir crest must be exactly level and the weir faces exactly verti- cal, or the standard head-to-discharge calibrations will not apply. 384 WEIRS 385 HOLES FOR lOd GALVANIZED NAILS AT 4" 4"0.C Figure D-1. (Top) Diagram of a Cippoletti weir plate. It should be cut from No. 8 or No. 10 galvanized iron plate. The trapezoidal notch must be cut to the exact dimensions as shown. Flov^ rates with this weir will be twice the values shown in Table D-1. (Bottom) A rectangular weir installed to measure water flow at the discharge of a fish hatchery. A sight gauge (insert) with a float in an aluminum cylinder is used to measure water depth over the crest of the weir. It must be positioned at a distance at least 2.5 times the depth of the water flowing over the weir. 386 fish hatchery management Table D-1. relation between head and discharge for cippoletti and rec- tangular WEIRS, discharge VALUES ASSUME A 1-FOOT-LONG WEIR CREST; FOR SHORTER OR LONGER CRESTS, MULTIPLY THESE VALUES BY THE ACTUAL LENGTH IN FEET. DISCHARGE DISCHARGE DISCHARGE HEAD (GALLONS HEAD (GALLONS HEAD (GALLONS (INCHES) PER MINUTE) (INCHES) PER MINUTE) (INCHES) PER MINUTE) 0.250 5.00 4.25 317 8.25 860 0.500 14.0 4.50 346 8.50 900 0.7,50 23.0 4.75 375 8,75 939 1 .00 36.0 5.00 405 9.00 978 1.25 50.0 5.25 436 9.25 1,020 1.50 (ifi.O 5.50 468 9.50 1 ,060 1.75 84.0 5.75 500 9,75 1,100 2.00 102 fi.OO 533 10.0 1,150 2.25 122 6.25 567 10.3 1,190 2.,50 143 6.50 601 10.5 1,230 2.75 165 6.75 636 10.8 1,280 3.00 188 7.00 672 11.0 1,320 3.25 212 7.25 708 11.3 1,370 3.50 237 7.50 745 11.5 1,410 3.75 263 7.75 783 11.8 1,460 4.00 290 H.OO 820 12.0 1,510 (3) The weir crest, formed with a metal plate, must be leak- proof, sharp or square-edged, and no thicker than ^-inch. The distance of the weir crest above the bottom of the channel should be at least 2- times the water head on the weir to minimize approach water velocities. (4) Air must have access to the underside of falling water as it flows over the weir crest. Otherwise, air pressure may force water against the down- stream face of the weir, increasing the rate of discharge above the flow rates indicated in Table D-1. (5) The channel above the weir must be straight, level, and clean to ensure smooth water flow. Sediment and debris should not be allowed to collect on or behind the weir. Appendix E Hatchery Codes for Designating Fish Lots Table E-1. codes for United States national fish hatcheries. CODE HATCHERY CODE HATCHERY Ab Abernathy, Washington Cf Crawford, Nebraska Ac Alchesay, Arizona Ct Creston, Montana Al Allegheny, Pennsylvania DH Dale Hollow, Tennessee BD Bs Baldhill Dam. North Dakota Berkshire, Massashusetts Dt Ds Dexter, New Mexico Dworshak, Idaho Bl Bd Bm Berlin, New Hampshire Bowden, West Virginia Bozeman, Montana EC Ed En Eagle Creek, Oregon Edenton, North Carolina Ennis, Montana Et Entiat, Washington CH Carbon Hill, Alabama Ew Erwin, Tennessee Cs Carson, Washington Cd Cedar Bluff, Kansas Ff Frankfort, Kentucky CF Chattahoochee Forest, Georgia Cr Cheraw, South Carolina GD Garrison Dam, North Dakota Ch Cohutta, Georgia GP Gavins Point, South Dakota Cm Coleman, California Gn Genoa, Wisconsin Cn Corning, Arkansas GL Green Lake, Maine CB Craig Brook, Maine GF Greers Ferry, Arkansas 387 388 USH HATCHERY MANAGEMENT Table E-1. continued. CODE HATCHERY CODE HATCHERY Hg Hagerman, Idaho HL Harrison Lake, Virginia Hb Hebron, Ohio HF Hiawatha Forest, Michigan Hk Hotchkiss, Colorado ID Inks Dam, Texas IR Iron River, Wisconsin Js Jackson, Wyoming JH Jones Hole, Utah JR Jordan River, Michigan Kk Kooskia, Idaho Lh Lahontan, Nevada LM Lake Mills, Wisconsin Lm Lamar, Pennsylvania Lv Leadville, Colorado Le Leavenworth, Washington Lt Leetown, West Virginia LW Little White Salmon, Washington Mk Makah, Washington MS Mammoth Springs, Arkansas MN McNenny, South Dakota ML McKinney Lake, North Carolina Mr Meridian, Mississippi Ms Mescalero, New Mexico MC Miles City, Montana MI Millen, Georgia Ns Nashua, New Hampshire Ni Natchitoches, Louisiana NL New London, Minnesota No Neosho, Missouri Nf Norfork, Arkansas NA North Attleboro, Massachusetts Or Orangeburg, South Carolina PB Paint Bank, Virginia PC Pendills Creek, Michigan PF Pisgah Forest, North Carolina Pf Pittsford, Vermont Qc Quilcene, Washington Qa Quinauit, Wahington SM San Marcos, Texas Sr Saratoga, Wyoming Sn Senecaville, Ohio Sf Spearfish, South Dakota SC Spring Creek, Washington TC Tehama Colusa, California Ts Tishomingo, Oklahoma Tp Tupelo, Mississippi Uv Uvalde, Texas VC Valley City, North Dakota Wh Walhaila, South Carolina Wm Warm Springs, Georgia WS Warm Springs, Oregon Wl Welaka, Florida WR White River, Vermont Ws White Sulphur Springs, West Virginia Wd Wiilard, Washington WC Williams Creek, Arizona WB Willow Beach, Arizona Wt Winthrop, Washington Wk Wolf Creek, Kentucky Wv Wytheville, Virginia Yk Yakima, Washington HAICHKRY CODES 389 Table E-2. two-letter state abbreviations. AL Alabama AK Alaska AZ Arizona AR Arkansas CA California CO Colorado CT Connecticut DE Delaware DC District of Columbia FL Florida GA Georgia GU Guam HI Hawaii ID Idaho IL Illinois IN Indiana lA Iowa KS Kansas KY Kentucky LA Louisiana ME Maine MD Maryland MA Massachusetts MI Michigan MN Minnesota MS Mississippi MO Missouri MT Montana NB Nebraska NV Nevada NH New Hampshire NJ New Jersey NM New Mexico NY New York NC North Carolina ND North Dakota OH Ohio OK Oklahoma OR Oregon FA Pennsylvania PR Puerto Rico RI Rhode Island SC South Carolina SD South Dakota TN Tennessee TX Texas UT Utah VT Vermont VA Virginia VI Virgin Islands WA Washington wv West Virginia WI Wisconsin WY Wyoming Appendix F Nutritional Diseases and Diet Formulations Table F-1. nutritional diseases in eish. ihe following is presented as a diagnostic guide. all signs observed in eish are lumped together and some disorders may not apply to a particular fish species. (source: HORAK I97r).) NUTRIENI' Protein Crude pi u It in Amino acids Fat SIGNS OF DEFICIENCY OR EXCESS Signs of deficiency; poor growth; reduced activity; fish remain near the water surface; increased vulnerability to parasites. Signs of excess: moderate to shght growth retardation. Signs of deficiency: deficiency of any essential amino acid can cause reduced or no growth; lens cataract may result from a deficiency of any essential amino acid except arginine; lordosis or scoliosis may result from less than ().2".i tryptophan in the diet; blacktail syn- drome, loss of equilibrium will result from less than 0.8"ii lysine in the diet. Signs of excess: inhibited growth results from excess leucine; dietary inefficiency may result from extreme ratios of phenylalanine to tyrosine, high levels of either phenylalanine or tyrosine, and valine greater than 3"ii. Signs of deficiency: poor growth, as essential amino acids must be used for energy; necrosis of the caudal fin; fatty pale liver; fin ero- sion; dermal depigmentation; edema; increased mitochondrial swel- ling; mortality; stress- induced violent swimming motion with little forward movement, followed by motionless floating for 1,') minutes before recovery; slightly reduced hemoglobin; anemia; liver and kidney degeneration; soreback; high mortality may occur from corn or soy oil in diets at near-freezing temperatures. Signs of excess: plugged intestine; liver and kidney degeneration; death may result from hard fat (beef); pale, swollen, yellow-brown. 390 nutritional diseases and diets 391 Table F-I. continued. NUTRIENT SIGNS OF DEFICIENCY OR EXCESS Fat [continued) fatty infiltrated liver; pigmented insoluble fat (ceroid) in liver; water edema; amenia; fattv infiltrated kidney and spleen; reduced weight gain with no increase in carcass fat. Carbohydrate Signs of deficency: reduced survival of stocked fish; decreased liver glycogen from carbohydrate-free diet; slow growth, as amino acids are used for energy. Signs of excess: glycogen-infiltrated, pale, swollen liver; fatty- infiltrated kidneys; degenerated pancreatic islets; poor growth; edema; elevated blood glucose; death from overfeeding or from digestible carbohydrate greater than 20" of diet. Vitamins Vitamin A Signs of deficency: serous fluid in abdominal cavity; edema; ex- ophthalmus; hemorrhage of anterior chamber of the eye, base of fins, and kidne%s; light-colored body; poor appetite; poor growth; eye cataracts; anemia; drying and hardening of mucous-secreting tissue; clubbed gills; high mortalit) ; bent gill operculum. (Vitamin A is destroyed by rancid fats.) Signs of excess: enlargement of liver and spleen; retarded growth; skin lesions; epithelial keratinization; abnormal bone formation and fusion of vertebrae; necrosis of caudal fin; elevated levels of body fat and cholesterol; lowered hematocrit. Vitamin D Signs of deficency: elevated feed conversion; slightly increased number of blood cells; impaired absorption of calcium and phos- phorous from intestine. Signs of excess: impaired growth; decalcification, especially of ribs; lethargy; dark coloration; ele\ated blood serum calcium caused by doses of D3. Vitamin E Signs of deficency: serous fluid in abdominal cavity; ceroid in liver, spleen, and kidney; fragility of red blood cells; poor growth; poor food conversion; cell degeneration; sterility; excessive mortality; clubbed gills; soreback; general feed rancidity, as vitamin E is a strong antioxidant. Vitamin E is involved with selenium and vita- min C for normal reproduction, and may be involved with embryo membrane permeability and hatchability of fish eggs. It is des- troyed by rancid fats. Fortification of E can prevent anemia caused by rancidity of the feed. Signs of excess: no growth; toxic liver reaction; death; accumulation of vitamin E in ovary. Vitamin h Signs of deficency: anemia; pale liver, spleen, and gills; hemorrhagic gills, eyes, base of fins, and vascular tissues; death. Signs of excess: none. Thiamine (B^) Signs of deficiency: poor appetite; muscle atrophy; vascular degenera- tion; con\ulsions; rolling whirling motion; extreme ner\ousness and no recovery from excitement; instability and loss of equilibrium weakness; edema; poor appetite; poor growth; retracted head sometimes a purple sheen to the body; melanosis in older fish excessive mortality; anemia; corneal opacities; paralysis of dorsal and pectoral fins. 392 FISH HATCHERY MANAGEMENT Table F-1. continued NUTRIENT SIGNS OF DEFICIENCY OR EXCESS Vitamins (continued) Riboflavin (B2) Pyridoxine (Bf) Pantothenic acid Biotin Choline Vitamin B12 Niacin Ascorbic acid (vitamin C) Signs of excess: none. Signs of deficiency: corneal vascularization; cloudy lens and cataract; hemorrhagic eyes, nose, or operculum; photophobia; incoordina- tion; abnormal pigmentation of iris; striated constructions of abdominal wall; dark coloration; poor appetite; anemia; complete cessation of growth; dermatitis; high mortality. Signs of excess: none. Signs of deficiency: nervous disorders; epileptiform convulsions; hyperirritability; alexia; loss of appetite; edema of peritoneal cavity with colorless serous fluid; rapid onset of rigor mortis; rapid jerky breathing; flexing of opercles; iridescent blue-green coloration on back; heavy mortality; retarded growth; indifference to light. (A high tryptophan diet increases requirement for pyridoxine.) Signs of excess: none. Signs of deficiency: clubbed gills; necrosis; scarring and cellular atro- phy of gills; gill exudate; general "mumpy" appearance; eroded opercles; pinhead; prostration; loss of appetite; lethargy; poor growth; high mortality; eroded fins; disruption of blood cell forma- tion. Signs of excess: none. Signs of deficiency: loss of appetite; lesions in colon; dark coloration (blue slime film that sloughs off in patches); muscle atrophy; spas- tic convulsions; anemia; skin lesions; reduced stamina; contracted caudal fin; poor growth; elevated feed conversion; small liver size; abnormally pale liver. Signs of excess: depression of growth; excessive levels can be coun- teracted by adding folic acid or niacin. Signs of deficiency: poor food conversion; hemorrhagic kidney and intestine; exophthalmia; extended abdomen; light-colored body; poor growth; fatty infiltrated livers; increased gastric emptying time; anemia. Signs of excess: none. Signs of deficiency: Poor appetite; erratic and low hemoglobin; frag- mentation of erythrocytes with many immature forms; protein metabolism disruption; poor growth; poor food conversion. Signs of excess: none. Signs of deficiency: loss of appetite; poor food conversion; lesions in colon; jerky or difficult motion; weakness; reduced coordination; mortality from handling stress; edema of stomach and colon; mus- cle spasms while resting; tetany; sensitivity to sunlight and sun- burn; poor growth; swollen but not clubbed gills; flared opercles; anemia; lethargy; skin hemorrhage; high mortality. Signs of excess: none. Signs of deficiency: scoliosis; lordosis; abnormal opercles; impaired formation of collagen; impaired wound healing; abnormal cartilage; twisted, spiraled, deformed cartilage of gill filaments; clubbed gills; hyperplasia of jaw and muscle; deformed vertebrae; eye lesions; NUTRITIONAL DISEASES AND DIETS 393 Table F-1. continued. NLTRItM SIGNS UF DEFICIENCV OR EXCESS Vitamins [continued] hemorrhagic skin, hver, kidney, intestine, and muscle; retarded growth; loss of appetite; increased mortality; eventual anemia. Signs of excess: none. Folic acid Signs of deficiency: lethargy; fragility of fins, especially caudal; dark (vitamin H) coloration; reduced resistance to disease; poor growth; no appetite; infraction of spleen; serous fluid in abdominal cavity; sluggish swimming; loss of caudal fin; exophthalmia. Signs of excess: none. Inositol Signs of deficiency: distended stomach; increased gastric emptying time; skin lesions; fragile fins; loss of caudal fin; poor growth; poor appetite; edema; dark color; anemia; high mortality; white-colored liver. Signs of excess: none. Minerals Signs of deficiency: hyperemia on floor of mouth; protrusions at bran- chial junction; thryoid tumor; exophthalmia; renal calculi (kidney stones). Signs of excess: scoliosis; lordosis; blacktail; eroded caudal fin; mus- cular atrophy; paralysis if there is dissolved lead in the water at 4-8 parts per billion (no toxic effects with lead up to 8, ()()() parts per million in dry feed); growth retardation; pigmentation changes when copper is greater than 1 mg/g in dry diet (lOO to 200 times the daily requirement). Toxins and chemicals Signs of deficiency: none. Signs of excess: Hepatocellular carcinoma after 1220 months with tannic acid at 7. ,1^480 mg/100 g in dry feed; loss of appetite; grossly visible sundan-ophilic substance in liver; decreased availa- bility of lysine when greater than 0.04".. free gossypol (yellow pig- ment from glands of cottonseed meal) is in feed; trypsin inhibition resulting from low heat-treated soybean meal; liver cell carcinomas; pale yellow or creamy-colored livers; gill epithelium disruption resulting from aflatoxin-contaminated oilseed meals (especially cot- tonseed) with as little as 0.1-0..T parts per billion aflatoxin Bl, or 7.,T mg carbarson/lOO g dry feed; feed with greater than 13".. mois- ture encourages mold growth which produces the toxin; gill disease resulting from DDT at 7. ,5 mg/100 g dry diet; cataract caused by 30 mg/100 mg dry diet of thioacetamide for 12 months; broken- back syndrome; retarded growth produced by toxaphene in water at greater than 70 parts per thousand; retarded ammonia detoxica- tion enzymes affected by dieldrin greater than 0.36 parts per mil- lion in feed; inhibited mobilization of liver glycogen and Cortisol production in fish under stress and endrin greater than 0.2 in feed; stimulated thyroid when greater than 0.8 parts per million DDT or 2.0 parts per million DDE is in feed, or 2,4-D in the water; lowered egg hatching; abnormal fry anemia; mortality; reduced growth; dark, lethargic fish when greater than 0.2-0..'i parts per million Aro- clor 12,54 is in feed; yellow-colored flesh when ()"« corn gluten meal is in feed. 394 FISH HAI'CHERY MANAGEMENT Table F-2. dry trout feeds developed by the US fish and wh.dijfe serv- ice. VALUES are percent OF FEED BY WEIGHT. MP = MINIMUM PROTEIN. INGREDIENT STARTER DlEr SD 7 FINGERLING DIETS PR fi PR y PRODUCTION DIET PR 11 Fish meal (MP 60",,) Soybean meal, dehulled seeds Flour (MP .SO",,) Meal (MP 47.5",,) Corn gluten meal (MP 60";,) Wheat middlings, standard Yeast, dehydrated brewer's or torula Blood meal (MP 80",,) Whey, dehydrated Fish solubles, condensed (MP 50" „) Fermentation solubles, dehydrated Alfalfa meal, dehydrated Soybean oil Fish oil Vitamin premix no. 30 Choline chloride, 50% Mineral mixture 4.5 34 35 \5 10 20 6 9.35 li).3 13.3 5 5 5 5 5 10 10 5 8 8 3 3 10 4 5 0.4 0.4 0.4 0.2 0.2 0.2 O.O.T 0.1 0.1 26 25 17.3 5 10 8 3 5 0.4 0.2 0.1 "See Table F «. Mineral mixture (grams per pound) MnS04, 94; KIO^, 0.38; inert carrier, 251.37. ZnS04, 84; FeS04- 7H2O, 22.5; CUSO4, 1.75; nu tritional. diseases and dieis 395 Table F-3. dry trout feeds developed by Colorado division of wildlife, values are precent of feed by weight. mp = minimum protein. STARTER DIETS FINCERLING DIETS REGULAR PRODUCTION INGREDIENTS SD 3 SD 3A PR 4 PR 4A DIP. I Fish meal (MP 60"..) 37 42 31 35 27 Soybean meal, dehulled seeds Flour (MP 50%) 5 Meal (MP 47.5"..) Corn gluten meal (MP 60".,) Wheat middlings, standard 13.8 1.3 19.8 l.xH 23.8 Wheat germ meal 5 Yeast, dehydrated brewer's 4.5 7 3.5 5.5 10 Blood meal (MP 80'..) 7 2 3 2.5 Whey, dehydrated 10 10 5 5 (i 13.8 1.3 19.8 l.x8 4.5 7 3.5 5.5 7 2 3 10 10 10 U) ,T 5 8 8 3 3 8 8 Fi 8 8 4 4 0.5 0.5 0.5 0.5 0.2 0.2 0.2 0.2 1 1 2 2 ''See Table F-8. Maximum zinc content 0.005"ii. 10 Fish solubles, condensed 5 10 Fermentation solubles, dehydrated 5 5 8 8 6.5 Alfalfa meal, dehydrated Poultry feathers, hydrolyzed Fish oil 8 8 4 4 3.5 Vitamin premix no. 30" 0.5 0.5 0.5 0.5 0.5 Cholme chloride 0.2 0.2 0.2 0.2 0.2 Salt, trace mineralized 112 2 1 'Md (ISM MAM MlJ'.y MANAOKMKNf iMU.t. F i. I>IS l)i.VU.()\'l.l) IJY I UK L .S HSil AM) WILDIJht ShKV I' I VAM;h,S AUI, I'UKChNIOF KU-U BY WhIOHt Ml' MIMM" m CHO If IN .VIAKIJK IJIKI ( r-'.( I' I I'-', fiu I |Nf,«l,liM.M'> l'j*li fiM'i.l 'MP <.()' .; CoH-Miv.-rl (n-';.l, 5 F) 10 r> T) 10 0 1 0.4 0.2 0.2 0.1 .•i4 10 4 0.4 0.2 0.1 u ir,'' III ■.^iliii'iii I'-i- •(Is ;it a See l.il'l' I '' lii'iMl") iriir.l I" .I'I'I' il I', llii ■;il.iiiiiii |)i'iiir. level i)( H I'l.iiir, pel |)i)iiii'l nl |iii im • 'Miiii'i.iI iiiixIiik- 'i',i,iiir, |i' I |.miiir|/ /)i,S(>»,(, HI; l'L-,'5U,(' 711^0, 22..'); CU.SU4, 1,7.'>; MiiSO,,, Ml, KIOj, 0,:iH, lll'll '.iiii'i, 2,".l,:'.7, NT I Kl I l( )\ \l 1)1 MASKS WlilMI l\ 1")7 TAHI.I, V-Fy. MOIST SALMON M.KDS Dl.Vl.l.OI'l.l) in OKIa;ON SIAIK UNIVLKSin AND oKi:(;oN nirvKiMiM oi iisii and wiimiii \ \m is aki nun ni (H iim> ii\ wtiGHi. OKH.dN (ilU(.i)N SIAKIIK MAUIIK MASM IM-,l,l,in INGREnilNI (»M I (ir i Meal mix Mi'itini; meal IH rish inci.l'' 2!» Wheat genu me.il 10 4 Whey, dehydrated 10 rt Cottonseed inciil, di Imllrd 17 Shrini|) <>i c tab meal 4 Com distiller's dried solubles 3 Vitamin premix*^ l..'> l.Ti Wet mix I una viseera 10 I'urbot, salmon visteia, liemng^ 10 Wet fish'' 30 Hcirmnnir 10 (i.O Choline chloride (liquid, 70".. iiuhIik () ()..') O.Fi Miiimniiii /•)' [iiniciii, rn.ixiiiHini .'i"'i NaC'l. Herring meal (minimum 70". i prnlrui, mnsminm .'i"n NaCi) must be used as !()()"" ol the fish meal in earh batch of ' -, ^^ -, and ^^ mk Ii jiellels, and at no less than fit)"" of the fish miid m each batch of large pellets. Make (minimum (>K"" protein), anchovy (domestic or J'eruvi;iii, miiniinim Grj"/!! protein), or menhaelen (mitiirinmi Mt |prn(cjiil m;iy be used as the remaining poilion of the fish meal (or larger pellets, provided (he liilal lisli meal is increased to M)"" of the diet (31"" if menhaden us used). "^Prepress solvent-extracted; minimum 4K.,'J"" protein, maximum 0 O.'i.V'n free gossypid. Maximum IV'/n NaCI; muiiriinrii /V' ptoicin (not (onnted as (isli meid in piolein i all ulti tions Sec Table I' H, Oregon salmon premix. ^No heads or gills; with livers, pasteurized. ^Turbot, pasteurized salmon viscera (no heads or gills), or pasteuri/.ed heriing. Limited to tuna viscera, herring, "l)r)tlom fish" (whole or fillet scrap), salmon viscera, dog- fish, and hake, with the following provisions: (l) two or more must be used in combination, with no one exceeding l.VJ^i of the total diet; (2) ■- - and ;;7-inch pellets shall contain at least 7.,'>"'ii tuna viscera, but no fillet scrap. '.Stabilized with 0.,r;. BMA lUIT (l:l); less than IIO".. free fatty acids, and m-t alkaline reprocessed. 398 FISH HATCHERY MANAGEMENT Table F-6. dry catfish feeds, values are precent of feed by weighi. mp = MINIMUM protein. feeds'' INGREDIENTS 1 2 3 4 Fish meal (MP 60"n) 10 10 12 Soybean meal, dehulled seeds (MP 44%) 26 52 35 (MP 49"o) 20 Corn gluten meal (MP 60"..) 20 Wheat middlings, standard IS) Blood meal (MP H()"„) 3 5 Alfalfa meal, dehydrated 3.4 Meat and bone meal 15 Corn, yellow, dent 21.4 28.65 Distillers dried grains with sol ubles 5 Dried distillers solubles 7.5 8 Rice bran 25 Rice mill dust 10 Wheat, grain, ground 24.9 5 Cottonseed meal, dehulled (MP 48.5':n) 10 Feather meal 5 Animal tallow 1.5 2 2.5 Dicalcium phosphate 4.5 1 3 Trace mineralized salt 0.5 0.5 0.25 1 Vitamin premix 0.5 0.5 0.5 0.5 Choline chloride, 5()"(i 0.1 0.1 0.1 0.1 Feed 1 was developed by the departments of Biology and Grain Science, Kansas State University. Feed 2 was developed by the Department of Fisheries and Allied Aquacultures, Auburn University. Feed 3 was developed by the Skidaway Institute of Oceanography and Coastal Plain Station, Savannah, Georgia. Feed 4 was developed by the US Fish and Wildlife Service's Fish Farming Experimental Station, Stuttgart, Arkansas. See Table F-8, catfish premix. NUTRITIONAL DISEASES AND DIETS 399 Table F-7. coolwater dry fish feed (w-7) developed for fry and finger- lings BY the us fish and wildlife service, vall'es are percent of feed by weight. MP = minimum protein. INGREDIENTS W-7 Fish meal (MP (i5"„) Soybean flour, dehulled seeds (MP 48.,'j"(i) VV'heat middlings, standard Fish solubles, condensed (MP 50%) Blood meal (MP 80",i) Yeast, dehydrated brewer's Whey, dehydrated Fish oil Vitamin premi.x no. 30 Choline chloride, 50"o .50 10 5.1 10 5 5 5 9 0.6 0.3 See Table F 8. Vitamin premix (no. 30) is used at 1.5> the level used in trout feeds. Table F-8. specifications for vitamin premixes for catfish, trout, and salmon feeds, values are amounts per pound of premix". CATFISH TROUT OREGON SALMON vitamin UNITS PREMIX PREMIX NO. M) PREMIX Vitamin A lU 500,000 750,000 Vitamin B lU 90,000 50,000 Vitamin E lU 4,(S00 40,000 15,200 Vitamin K^ mg 900 1,2.50 545 Ascorbic acid g 9 75 27 Biotin mg 10 40 18 Bl2 mg 2 2.5 1.8 Folic acid mg 4(i0 1,000 385 Inositol g 9 8 Niacin^ g 9 25 5.7 Pantothenate g 10 12 3.2 Pyridoxine mg 1,800 3,500 .535 Riboflavin g 1.8 6 1.6 Thiamine-' mg 1,800 4,000 778 "Diluent used to bring the total amount to one pound must be a cereal product. Levels in this vitamin premix are calculated to supply the recommended amounts in a complete feed. Palmitate or acetate. Stabilized. Alpha tocopherol acetate. Menadione sodium bisulfite complex. ■^Niacinamide. fi , . D-calcium. 'HCl. Mononitrate. 400 FISH HATCHERY MANAGEMENT Table ¥-9. recommended amounts of vitamins in fish feeds, values are amounts per pound of feed, and include total amounts from ingredients AND VITAMIN PREMIXES". (SOURCE: NATIONAL ACADEMY OF SCI- ENCES.) VVARMWATER FISH FEEDS SUPPLEMENTAL COMPLETE SALMONID VITAMIN UNITS DIET DIET FEEDS Vitamin A lU 1,000 2,500 1 ,000 Vitamin D3 lU 100 450 R* Vitamin E lU 5 23 15 Vitamin K mg 2.3 4.5 40 Ascorbic acid mg 23 45 50 Biotin mg 0 0.05 0.5 B12 mg 0.005 0.01 0.01 Choline mg 200 250 1,500 Folic acid mg 0 2.3 2.5 Inositol mg 0 45 200 Niacin mg 13 45 75 Pantothenic acid mg 5 50 20 Pyridoxine mg 5 9 5 Riboflavin mg 3 9 10 Thiamine mg 0 9 5 These amounts do not allow for processing or storage losses but give the total vitamins contributed from all sources. Other amounts may be more appropriate under various condi- tions b R = required, amount not determined. Requirement is affected directly by the amount and type of unsaturated fat fed. G Appendix Chemical Treatments: Calculations and Constant Flow Delivery Hatchery systems often receive prolonged- bath or constant-flow chemical treatments that adjust water quality or control diseases. In prolonged-bath treatments (without water flow), chemicals are spread over the surface of the water body, and mixed throughout its volume, by hand or machine. Many hatchery tanks and most ponds, particularly large ones, are treated statically. In constant-flow treatments, chemicals are metered at one point into continously renewed water supplies; the turbulence of the moving water accomplishes the mixing. Constant-flow treatments typically are used in intensive culture when even a temporary halt in the supply of fresh water might cause fish mortality because of oxygen depletion or waste accumulation. Chemical applications normally are couched in terms of final concentra- tions; a pond treatment of 2 parts per million rotenone means the whole pond should contain this concentration after application. Concentrations, in turn, typically are weight ratios: weight of chemical in solution (or suspension) per weight of solvent (usually water). The ratio may be expressed in terms either of unit solvent weight or of unit solute weight. Ten pounds chemical per ton of water, and one pound chemical per 200 pounds water (l:200), both represent the same concentration. Even when a concentration is expressed in terms of volume or capacity (pounds/acre- foot; milligrams/liter), it is the equivalent weight of that volume of water that is implied. 401 402 FISH HAICHKRY MANAGEMENT Calculations for Prolonged-Bath Treatments The basic formula for computing the amount of chemical needed is: capacity final (volume) of concentration correction water to x desired x factor . , . , \ weight of be treated Ippmj , . , — = chemical strength of chemical (decimal) needed The units of measure and the correction factor (Table G-l) that correlates volume with weight vary with the size of the unit to be treated. The chem- ical strength is the fraction of a chemical preparation that is active in- gredient when purchased; ppm is parts per million. For example, in smaller hatchery units, gallon capacities usually are used. Chemicals typically are measured in grams because small amounts are usually needed, and metric balances are more accurate than English ones in this range. The correction factor is 0.0038 (grams/gallon). Examples: (1) How much Dylox (50"(i active ingredient) is needed for a 0.25 ppm treatment of a 390-gallon tank? 390x0.25x0.0038 ^ ^, = 0.74 erams Uyiox 0.50 ^ ^ (2) How much copper sulfate (lOO'/o active ingredient) is needed for a 1:6,000 treatment of that 390-gallon tank? 390x167x0.0038 ^,^ ^ ^^ =- 247 grams CuSO. 1.00 ^ * Table G-1. correction factors used to convert volume or capacity to WEIGHT IN calculations OF CHEMICAL CONCENTRATION. Units Correction Factor grams (or milliliters)/gaIlon 0.00378 grams (or milliliters)/cubic foot 0.02828 grams (or milliliters)/cubic yard 0.76366 ounces (fluid)/cubic foot 0.00096 ounces (nuid)/cubic yard 0.0258.'i ounces (weight)/cubic foot 0.00100 ounces (weight)/cubic yard 0.02694 pounds/cubic foot 0.00006 pounds/cubic yard 0.00168 pounds/acre-foot 2.7181 CHEMICAL TREATMENTS 403 For ponds, volumes usually are known in acre-feet (surface area in acres X average depth in feet). Relatively large amounts of chemicals are needed for treatment, and these usually can be weighed in pounds. The correction factor is 2.7 (pounds/acre- foot per part per million). Example: How much of chemical A (60"() active ingredient) is needed for a 2-ppm treatment of a 2.0-acre pond that averages 2.5 feet deep? Volume = 2.0 acres x 2.5 feet = 5.0 acre-feet; 5.0X2.0X2.7 ^, , r . ■ , A = 45 pounds oi chemical A 0.60 Calculations for Constant-Flow Treatments The weight of chemical needed for constant-flow treatments is computed just as for prolonged-bath treatments. However, in this case the volume (capacity) of water to be treated is equal to the flow rate times the treat- ment time (for example, 10 gallons per minute x 30 minutes). Correc- tion factors are the same. The formula is: flow treatment final correction rate x time x concentration x factor weight of = chemical chemical strength (decimal fraction) needed Example: A trough receiving a water flow of six gallons per minute is to receive a 1-hour (60-minute) constant-flow treatment of chemical B (lOO% active strength) at a concentration of 5 ppm. How many grams of chemical B must be dispensed to maintain the treatment concentration? 6.0x60x5.0x0.0038 ^ „, r ■ • , t> = 6.84 grams oi chemical B. 1.00 ^ Constant-Flow Delivery of Chemicals Of the variety of constant-flow devices that have been adapted to hatchery use, commercial chicken waterers are the most reliable (Figure G-1). All such devices deliver only liquids. Dry chemicals first must be put into solution before they can be dispensed. If the amount of dry chemi- cal needed already has been computed by the formula given in the previ- ous section, it only is necessary to determine the amount of liquid that will be dispensed from the chicken waterer over the period of treatment. This is done by simple proportion. For example, if the constant-flow de- vice delivers 20 milliliters per minute and the treatment is to be 60 minutes long, 1,200 milliliters will be delivered in all. This is the water 404 FISH HATCHERY MANAGEMENT ISr^^^iiir?' Figure G-1. A constant- flow device for dispensing liquid chemicals, (l) The de- vice must be positioned over the water inflow to the fish-rearing unit, to insure uniform mixing of the chemicals in the water. (2) The device can be made from a conventional chicken waterer. Note siphon in place (arrow). volume into which the predetermined weight of chemical should be dis- solved before treatment begins. If a 300-gallon tank were receiving a 10-gallon-per-minute water flow, it would take at least 30 minutes (300 ^ 10) for water in the tank to be replaced. It would take this long for any chemical to reach a desired concentration in the tank. Thus, much of the treatment would be wast- ed. To avoid such waste, it is best to pretreat the tank. The water flow is shut off briefly, and chemical is quickly added to establish the final concentration required (according to the formula for static treatment above). Then the water flow is resumed and chemical metering is begun with the constant-flow device. After all the chemical has been dispensed, some time will be required for the last of it to be flushed from the treated tank. Partial draining of the tank will flush much of the chemical from the unit. Fish should be watched for signs of stress after, as well as during, the treatment period. If effluent from the tank has to be treated for public- health reasons, such treatment should be continued until all the chemical has disappeared from the system. H Appendix Drug Coatings for Feed Pellets Either gelatin or soy oil may be used as drug carriers for coating feed pel- lets. A representative sample of pellets should be checked for adequate coatings before the operation is terminated. Gelatin: 125 grams gelatin in 3.0 quarts water per 100 pounds of pellets. (1) Slowly dissolve the gelatin into hot tap water. (2) Stir the drug into the gelatin solution until all lumps are gone. (3) Slowly add the drug-gelatin mixture to pellets as they are stirred by hand or in a small cement mixer. To avoid pellet breakage, stir gently and only long enough to assure an even drug coating. Soy oil: 2-3 pounds per 100 pounds of pellets. (1) Mix drug evenly in warm (100-120° F) oil. (2) Pour or spray mixture over pellets. 405 I Appendix Length- Weight Tables Guide to Selecting a Condition Factor (C) Table to Match a Species of Fish Species Muskellunge (l,600), tiger muskellunge (l,600) Northern pike (l,81l) Lake trout (2,723) Chinook salmon (2,959), walleye (3,000), chan- nel catfish (2,877) Westslope cutthroat trout (3,559), coho salmon (3,737), steelhead (3,405) Rainbow, brook, and brown trout (4,055 ac- cepted rainbow trout C factor) Largemouth bass (4,606) The body form of some fishes remains nearly constant until the fish be- come sexually mature. Therefore, the table can be used for fish longer than 10 inches, or shorter than 1 inch, if the decimal point is moved as fol- lows in the tables: Columns Fish shorter than 7 inch Fish longer than 10 inches 1 and 4 Move three spaces to left Move three spaces to right 2 and 5 Move one space to left Move one space to right 3 and 6 Move three spaces to right Move three spaces to left 406 Condition factor (Cx 10^^' Table 1,500 I-l 2,000 1-2 2,500 1-3 3,000 1-4 3,500 1-5 4,000 1-6 4,500 1-7 5,000 1-8 LENG TH-WKIGH I lABLES 407 Table I-l. LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C = I,.')00x lo ' WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.150 1.0000 6666.664 0.0680 2.540 14697.465 0.154 1.0088 6493.508 0.0699 2.562 14315.719 0.158 1.0175 6329.117 0.0717 2.584 13953.301 0.162 1.0260 6172.844 0.0735 2.606 13608.777 0.1 fi6 1.0344 6024.102 0.0753 2.627 13280.859 0.170 1.0426 5882.359 0.0771 2.648 12968.371 0.174 1.0507 5747.137 0.0789 2.669 12670.250 0.178 1.0587 5617.988 0.0807 2.689 12385.531 0.182 1.0666 5494.516 0.0826 2.709 12113.324 0.186 1.0743 5376.355 0.0844 2.729 11852.824 0.190 1.0820 5263.172 0.0862 2.748 11603.293 0.194 1.0895 5154.652 0.0880 2.767 11364.051 0.198 1.0970 5050.520 0.0898 2.786 11134.477 0.202 1.1043 4950.512 0.0916 2.805 10913.996 0.206 1.1115 4854.383 0.0934 2.823 10702.074 0.210 1.1187 4761.922 0.0953 2.841 10498.227 0.214 1.1257 4672.914 0.0971 2.859 10302.000 0.218 1.1327 4587.172 0.0989 2.877 10112.977 0.222 1.1396 4504.523 0.1007 2.895 9930.762 0.226 1.1464 4424.797 0.1025 2.912 9754.996 0.230 1.1531 4347.844 0.1043 2.929 9585.348 0.234 1.1598 4273.523 0.1061 2.946 9421.496 0.238 1.1663 4201.699 0.1080 2.963 9263.1.52 0.242 1.1728 4132.250 0.1098 2.979 9110.043 0.246 1.1793 4065.061 0.1116 2.995 8961.914 0.250 1.1856 4000.021 0.1134 3.011 8818.523 0.254 1.1919 3937.029 0. 1 1 52 3.027 8679.652 0.258 1.1981 3875.990 0.1170 3.043 8545.082 0.262 1.2043 3816.815 0.1188 3.059 8414.625 0.266 1.2104 3759.420 0.1207 3.074 8288.090 0.270 1.2164 3703.725 0.1225 3.090 8165.305 0.274 1.2224 ' 3649.656 0.1243 3.105 8046.105 0.278 1.2283 3597.144 0.1261 3.120 7930.332 0.282 1.2342 3546.121 0.1279 3.135 7817.848 0.286 1.2400 3496.525 0.1297 3.1.50 7708. ,508 0.290 1.2458 3448.297 0.1315 3.164 7602.184 0.294 1.2515 3401.382 0.1334 3.179 7498.754 0.298 1.2571 3355.726 0.1352 3.193 7398.098 0.302 1.2627 3311.280 0.1370 3.207 7300.113 0.306 1.2683 3267.995 0.1388 3.221 7204.688 0.310 1.2738 3225.828 0.1406 3.235 7111.723 0.314 1.2792 3184.735 0.1424 3.249 7021.129 0.318 1.2846 3144.676 0.1442 3.263 6932.813 0.322 1.2900 3105.612 0.1461 3.277 6846.691 0.326 1.2953 3067.506 0.1479 3.290 6762.684 0.330 1.3006 3030.324 0.1497 3.303 6680.711 408 FISH HA rCHEKY MANAGEMENT Tabu: I-l. C = l.-WOx 10" ■ ', CONIINIJEI) Wl K.ll 1 l,()(H) LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.334 1.3058 2994.033 0.1515 3.317 6600.703 0.338 1.3110 2958.601 0.1,533 3.330 6522.590 0.342 1.3162 2i)23.9i)8 0.1551 3.343 6446.301 0.34fi 1.3213 2890. li)5 0. 1 5(i9 3.35fi 6371.777 0.350 1.3263 2857. 1()4 0.1588 3.369 <>298.957 0.354 1.3344 2824.880 0.1606 3.382 6227.785 0.358 1.3364 2793.317 0.1624 3.394 6158.199 0.3(i2 1.3413 2762.452 0.1642 3.407 60!)().15() 0.3(i(i 1.3463 2732.261 0.1660 3.419 (i023.598 0.370 1.3511 2702.723 0.1678 3.432 .5958.477 0.374 1 .35()0 2673.817 0.1696 3.444 5894.7,50 0.378 1.3608 2645.523 0.1715 3.456 5832.371 0.382 1.36,56 2617.822 0.1733 3.469 5771.301 0.386 1.3703 2590.694 0.1751 3.481 57 1 1 .492 0.390 1.3751 2,564.123 0.1769 3.493 5652.914 0.394 1.3797 2,538.091 0.1787 3.505 5595.523 0.398 1.3844 2512.583 0.1805 3.516 5539.289 0.402 1.3890 2487.582 0.1823 3.528 5484.172 0.406 1.3936 2463.074 0.1842 3.540 5430.141 0.410 1.3982 2439.044 0.1860 3.551 5377.164 0.414 1.4027 2415.479 0.1878 3.563 5325.211 0.418 1.4072 2392.364 0.1896 3.574 5274.254 0.422 1.4117 236!).<)88 0.1914 3.586 5224.258 0.426 1.4161 2347.438 0.1932 3.597 5175.207 0.430 1.4206 2325.601 0.1950 3.608 5127.063 0.434 1.4249 2304.167 0.19()9 3.619 5079.809 0.438 1.4293 2283.124 0.1987 3.630 ,5033.418 0.442 1.4336 2262.463 0.2005 3.641 4987.867 0.446 1.4380 2242.172 0.2023 3.652 4943.133 0.450 1.4422 2222.241 0.2041 3.663 4899.195 0.454 1.4465 2202.662 0.2059 3.674 4856.031 0.458 1.4507 2183.425 0.2077 3.685 4813.621 0.462 1 .45.50 2164.521 0.2096 3.696 4771.945 0.466 1.4591 2145.941 0.2114 3.706 4730.984 0.470 1.4633 2127.678 0.2132 3.717 4690.719 0.474 1.4674 2109.723 0.2150 3.727 4651.137 0.478 1.4716 2092.069 0.2168 3.738 4612.215 0.482 1.4757 2074.707 0.2186 3.748 4573.938 0.486 1.4797 2057.631 0.2204 3.758 4536.293 0.490 1.4838 2040.834 0.2223 3.769 4499.262 0.494 1.4878 2024.310 0.2241 3.779 4462.832 0.498 1.4918 2008.()5() 0.2259 3.789 4426.984 0.504 1.4978 1984.127 0.2286 3.804 4374.246 0.512 1.5057 1953.125 0.2322 3.824 4305. 8i)8 0.520 1.5135 1923.078 0.2359 3.844 4239. (i52 0.528 1.5212 1893.941 0.2395 3.864 4175.418 LENG IH-WEIGHI TABLES 409 Table I-l. C = l,.')()Ox 10 , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0..')36 1.5288 1865.673 0.2431 3.883 4113.098 0.544 1.5364 1838.237 0.2468 3.902 40.52.614 0.552 1.5439 1811.596 0.2.504 3.921 3993.881 0.560 1.5513 1785.717 0.2540 3.940 3936.826 0.568 1.5587 1760.566 0.2576 3.959 3881.379 0.576 1.5659 1736.114 0.2613 3.978 3827.471 0.584 1.5732 1712.332 0.2649 3.996 3775.041 0.592 1.5803 1689.192 0.2685 4.014 3724.027 0.600 1.5874 1666.670 0.2722 4.032 3674.374 0.608 1.5944 1644.740 0.2758 4.0,50 3626.028 0.616 1.6014 1623.380 0.2794 4.068 3578.937 0.624 1.6083 1602.568 0.2830 4.085 3533.053 0.632 l.(il51 1582.283 0.2867 4.102 3488.332 0.640 1.6219 1562.504 0.2903 4.120 3444.728 0.648 1.6286 1543.214 0.2939 4.137 3402.201 0.656 1.6353 1524.395 0.2976 4.154 3360.711 0.664 1.6419 1,106.029 0.3012 4.171 3320.221 0.672 1.6485 1488.100 0.3048 4.187 3280.695 0.680 1 .65.50 1470.593 0.3084 4.204 3242.099 0.688 1.6615 1453.493 0.3121 4.220 3204.400 0.696 1.6679 1436.787 0.3157 4.236 3167.569 0.704 1.6743 1420.460 0.3193 4.253 3131.574 0.712 1.6806 1404.,")00 0.3230 4.269 3096.388 0.720 1.6869 1388.894 0.3266 4.285 3061.984 0.728 1.6931 1373.632 0.3302 4.300 3028.336 0.736 1.6993 1358.701 0.3338 4.316 2995.420 0.744 1.7054 1344.092 0.3375 4.332 2963.211 0.752 1.7115 1329.793 0.3411 4.347 2931.688 0.760 1.7175 1315.795 0.3447 4.363 2900.828 0.768 1.7235 1302.08!) 0.3484 4.378 2870.612 0.776 1.7295 1288.666 0.3520 4.393 2841.018 0.784 1.7354 1275.516 0.3556 4.408 2812.028 0.792 1.7413 1262.632 0.3592 4.423 2783.624 0.800 1.7472 1250.006 0.3629 4.438 2755.788 0.808 1.7530 1237.630 0.3(i(i5 4.4,53 2728.503 0.816 1.7587 1225.496 0.3701 4.467 2701.753 0.824 1.7(i45 1213.598 0.3738 4.482 2675.523 0.832 1.7701 1201.929 0.3774 4.496 2649.797 0.840 1.7758 1190.482 0.3810 4.511 2624..561 0.848 1.7814 1179.251 0.3846 4.525 2599.801 0.856 1.7870 1168.230 0.3883 4.539 2.575.504 0.864 1.7926 1157.414 0.3919 4.5,53 2551.657 0.872 1.7981 1146.795 0.3955 4..567 2528.248 0.880 1.8036 1136.370 0.3992 4.581 2.505.264 0.888 1 .8090 1126.132 0.4028 4.-595 2482.694 0.896 1.8144 1116.078 0.4064 4.609 2460.527 410 FISH HATCHERY MANAGEMENT Table I-l. C = \,5()0x 10 ■ ', CONTINUED WEIGHT/ 1,000 LENGIH FISH/ Wl-.IGHr I.KNGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.904 1.8198 110(i.201 0.4100 4.622 2438.753 0.912 1.8252 1096.498 0.4137 4.636 2417.360 0.920 1.8305 1086.963 0.4173 4.649 2396.340 0.928 1.83,58 1077.593 0.4209 4.663 2375.682 0.936 1.8410 1068.382 0.4246 4.676 2355.377 0.944 1.8463 1059.328 0.4282 4.689 2335.417 0.952 1.8515 1050.427 0.4318 4.703 2315.791 0.960 1 .8566 1041.673 0.43.54 4.716 2296.493 0.968 1.8618 1033.064 0.4391 4.729 2277.514 0.976 1.8669 1024.596 0.4427 4.742 2258.846 0.984 1.8720 1016.266 0.4463 4.7,55 2240.481 0.992 1.8770 1008.071 0.4500 4.768 2222.413 1 .000 1.8821 1000.000 0.4536 4.780 2204.620 1.080 1.9310 925.927 0.4899 4.905 2041.318 1.160 1.9775 862.072 0.5262 5.023 1900.541 1.240 2.0220 806.455 0.5625 5.136 1777.928 1.320 2.0646 757.580 0.5987 5.244 1670.177 1.400 2.1054 714.291 0.6350 5.348 1574.740 1,480 2.1448 675.681 0.6713 5.448 1489.620 1 .560 2.1828 641.031 0.7076 5.544 1413.230 1.640 2.2195 609.762 0.7439 5.637 1344.293 1.720 2.25.50 581.401 0.7802 5.728 1281.769 1.800 2.2894 555. ,562 0.8165 5.815 1224.802 1.880 2.3228 531.921 0.8527 5.900 1172.684 1.960 2.3553 510.210 0.8890 5.983 1124.820 2.040 2.3870 490.202 0.9253 6.063 1080.709 2.120 2.4178 471.704 0.9616 6.141 1039.928 2.200 2.4478 454.552 0.9!)7!) 6.217 1002,113 2.280 2.4771 438.603 1.0342 6.292 966.952 2.360 2.5058 423.735 1 .0705 6.365 934.174 2.440 2.5338 409.842 1.1067 6.436 903,546 2.520 2.,5611 396.831 1.1430 6.505 874.862 2.600 2.5880 384.621 1.1793 6.573 847.944 2.680 2.6142 373.140 1.2156 6.640 822.632 2.760 2.6400 362.324 1.2519 6.706 798.788 2.840 2.6653 352.118 1.2882 6.770 776.287 2.920 2.6901 342.471 1.3245 6.833 755.019 3.000 2.7144 333.339 1.3608 6.895 734.885 3.080 2.7383 324.681 1,3970 6.955 715.798 3.160 2.7618 316.461 1.4333 7.015 697, ()76 3.240 2.7849 308.647 1.4696 7.074 680,450 3.320 2.8077 301.210 1..5059 7.131 664.053 3.400 2.8300 294.123 1.5422 7,188 648.429 3.480 2.8521 287.361 1.5785 7.244 633.522 3.560 2.8738 280.904 1.6148 7.299 619.286 3.640 2.8951 274.730 1.6510 7.354 605.676 LENGlH-VVtlGHT TABLF.S 411 T.\BLE I-l. C= l,.TOOx 10 ' ', CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GR.AMSJ iCM) KH.OGR.AM 3.720 2.9162 268.822 1.6873 7.407 592.6,50 3.800 2.9369 263.163 1.7236 7.460 580.174 3.880 2.9574 257.374 1.7599 7.512 ,568.211 3.960 2.9776 252.530 1.7962 7.563 5.56.732 4.040 2.9975 247.529 1.8325 7.614 545.708 4.120 3.0172 242.723 1.8688 7.664 ,535.112 4.200 3.0366 238.100 1.9050 7.713 524.919 4.280 3.0557 233.649 1.9413 7.762 515.108 4.360 3.0746 229.362 1.9776 7.810 505.656 4.440 3.0933 225.230 2.0139 7.857 496.545 4.520 3.1118 221.243 2.0,502 7.904 487.757 4.600 3.1301 217.396 2.0865 7.9,50 479.274 4.680 3.1481 213.679 2.1228 7.99(i 471.082 4.760 3.1659 210.088 2.1,591 8.041 463.164 4.840 3.1836 2()6.fil6 2.1953 8.()8f) 455.509 4.920 3.2010 203.256 2.2316 8.131 448.102 5.000 3.2183 200.000 2.2680 8.174 440.924 5.400 3.3019 185.185 2.4494 8.387 4()8.263 5.800 3.3815 172.414 2.6308 8.589 380.107 6.200 3.4575 161.2!)() 2.8123 8.782 355.584 6.600 3.5303 151.515 2.9937 8.967 334.034 7.000 3.6003 142.857 3.1751 9.145 314.946 7.400 3.6676 135.135 3.3,566 9.316 297.922 7.800 3.7325 128.205 3.5380 9.481 282.644 8.200 3.7952 121.951 3.7194 9.640 268.856 8.600 3.8560 116.279 3.9009 9.794 256.352 9.000 3.9149 111.111 4.0823 9.944 244.958 9.400 3.9720 106.383 4.2638 10.089 234.535 9.800 4.0276 102.041 4.4452 10.230 224.962 10.200 4.0816 98.039 4.626() 10.367 2Ui.l40 10.600 4.1343 94.340 4.8081 10.. 501 207.984 11.000 4.1857 90.909 4.9895 10.632 200.421 11.400 4.2358 87.720 5.1709 10.759 193.388 11.800 4.2848 84.746 5.3524 10.883 186.833 12.200 4.3327 81.967 5.5338 1 1 .005 180.707 12.600 4.3795 79.365 5.71.52 11.124 174.;)70 13.000 4.4254 76.923 5.8967 11.240 169.587 13.400 4.4703 74.627 6.0781 1 1 .355 164.524 13.800 4.5143 72.464 6.2595 1 1 .466 159.756 14.200 4.5576 70.423 6.4410 11.576 155.255 14.600 4.5999 68.493 6.6224 11.684 151.002 15.000 4.6416 66.667 6.8039 11.790 146.975 15.400 4.6825 64.935 6.9853 1 1 .893 143.1,58 15.800 4.7227 63.291 7.1667 11.996 139.533 16.200 4.7622 61.728 7.3482 12.096 136.088 1().600 4.8011 60.241 7.5296 12.195 132.808 412 KLSH HATCHERY MANAGEMENT -7 Table 1-1. c= i.^oox lo , continued WEIGHT/ 1, ()()() l.KNCriH FISH/ WKIGH'I LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 17.{)()() 4.8393 58,824 7.7111 12.292 1 29.684 17.400 4.8770 57.471 7.8925 12.388 12(i.7()2 17.800 4.9141 .56.180 8.0739 12.482 123.855 18.200 4.9506 54,945 8.2554 12.575 121.133 18. ()()() 4.9866 53,764 8.4368 12.666 118.528 19.()()() 5.0221 52,632 8.(il82 12.756 116.033 19.400 5.057 1 51.546 8.7997 12.845 113.640 19.800 5.0916 50,505 8.9811 1 2.933 111.344 20.200 5.1257 49,505 9.1625 13.019 109.140 20.600 5.1593 48,544 9.3440 13.105 107.021 21.000 5.1925 47,619 i).5254 13.189 104.982 21.400 5.2252 46,729 9.7069 13.272 103.020 21.800 5.2576 45,872 9.8883 13.354 101.129 22.200 5.2896 45.045 10.0697 13.436 99.307 22.600 5.3211 44.248 10.2512 13.516 97.550 23.000 5.3524 43.478 1().432() 13.595 95.853 23.400 5.3832 42.735 10.6140 13.673 94.215 23.800 5.4137 42,017 10.7955 13.751 92.631 24.200 5.4439 41,322 10.9769 13.827 91.100 24.(i00 5.4737 40,650 11.1 583 13.903 89.619 25.000 5. ,5032 40,000 11.3398 13.978 88.185 25.800 5.5613 38,760 11.7027 14.126 85.4,50 26.600 5.6182 37,594 12.0650 14.270 82.880 27.400 5.6740 36,496 12.4285 14.412 80.460 28.200 5.7287 35.461 12.7913 14.551 78.178 29.000 5.7823 34.483 13.1542 14.687 76,021 29.800 5.8350 33.557 13.5171 14.821 73,980 30.600 5.8868 32.680 13.8800 14.9,52 72,046 31.400 5.9376 31,847 14.2428 15.082 70,211 32.200 5.5)876 3 1 ,056 14.6057 15.209 68,466 33.000 6.0368 30.303 14.9686 15.333 66,807 33.800 6.0852 29.586 15.3314 15.4.56 65,225 34.600 6.1328 28.902 15.6943 15.577 63,717 35.400 6.1797 28.249 16.0572 15.697 62.277 36.200 6.2259 27.624 16.4201 15.814 60.901 37.000 6.2715 27.027 16.782!) 15.930 59,584 37.800 6.3164 26.455 17.1458 16.044 58,323 38.(i00 6.3606 25.907 17.5087 16.156 57,114 39.400 6.4042 25.381 17.8716 16.267 55.955 40.200 (i.4473 24.876 18.2344 16.376 54.841 4 1 .()t)0 6.4898 24.390 18.5973 16.484 53.771 41.800 6.5317 23.923 18.9602 16.591 52.742 42.600 6.5731 23.474 19.3230 16.696 51.752 43.400 6.6140 23.041 19.6859 16.800 .50.798 44.200 6.6544 22.624 20.0488 16.902 49.878 45.000 6.()943 22.222 20.4117 17.004 48.991 LENGTH-WEIGHT TABLES 413 Table I-l. C = 1,500 X 10 , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 45.800 6.7338 21.834 20.7745 17.104 48.136 46.600 6.7727 21.459 21.1374 17.203 47.309 47.400 6.8113 21.097 2 1 .5003 17.301 46.511 48.200 6.8494 20.747 21.8632 17.397 45.739 49.000 6.8871 20.408 22.2260 17.4!)3 44.992 49.800 6.9244 20.080 22.5889 17.588 44.269 50.600 6.9612 19.763 22.9518 17.682 43.570 51.400 6.9977 19.455 23.3147 17.774 42.891 52.200 7.0338 19.157 23.6775 17.866 42.234 53.000 7.0696 18.868 24.0404 17.957 41.597 53.800 7.10,50 18.587 24.4033 18.047 40.978 54.600 7.1400 18.315 24.7661 18.136 40.378 55.400 7.1747 18.051 25.1290 18.224 39.795 56.200 7.2091 17.794 25.4919 18.311 39.228 57.000 7.2432 17.544 25.8548 18.398 38.677 57.800 7.2769 17.301 26.2176 18.483 38.142 58.600 7.3103 17.065 26..5805 18.568 37.621 59.400 7.3434 16.835 26.9434 18.652 37.115 60.200 7.3762 16.611 27.3063 18.736 36.622 61.000 7.4088 16.393 27.6691 18.818 36.141 61.800 7.4410 16.181 28.0320 18.900 35.673 62.600 7.4730 15.974 28.3949 18.981 35.218 63.400 7.5047 15.773 28.7578 19.062 34.773 64.200 7.5361 15.576 2i).120fi 19.142 34.340 65.000 7..5673 15.385 29.4835 19.221 33.917 65.800 7.5982 15.198 29.8464 19.299 33..505 66.600 7.6289 15.015 30.2092 19.377 33.102 67.400 7.6,593 14.837 30.5721 19.455 32.709 68.200 7.6895 14.663 30.9350 19.,531 32.326 69.000 7.7194 14.493 31.2979 19.607 31.951 69.800 7.7492 14.327 31.6607 19.683 31. .585 70.600 7.7787 14.164 32.0236 19.758 31.227 71.400 7.8079 14.006 32.3865 19.832 30.877 72.200 7.8370 13.8,50 32.7494 19.906 30.535 73.000 7.8658 13.699 33.1122 19.979 30.200 73.800 7.8944 13.5,50 33.4751 20.052 29.873 74.600 7.9229 13.405 33.8380 20. 1 24 29.553 75.400 7.9511 13.263 34.2009 20.196 29.239 76.200 7.9791 13.123 34.,5637 20.267 28.932 77.000 8.0069 12.i)87 34.9266 20.338 28.631 77.800 8.0346 12.853 35.2895 20.408 28.337 78.600 8.0620 12.723 35.6523 20.478 28.049 79.400 8.0893 12.594 36.0152 20.547 27.766 80.200 8.1164 12.469 36.3781 20.616 27.489 81.000 8.1432 12.346 36.7410 20.684 27.217 81.800 8.1700 12.225 37.1038 20.752 26.951 414 FISH HAICHKRY MANAGF.MKNT TABI. 1,1-1. C=l/)OOxlO SCONTINUED WEIGHT/ 1,(100 LENGTH KISH/ WEIGH!' LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 82.fi()0 8.19()5 12.107 37.4667 20,819 26.690 83.400 8.2229 1 1 .9i)0 37.829() 2().88() 26.434 84.200 8.2491 11.876 38.1925 20,953 26.183 85.000 8.2751 11.765 38.5553 21,019 25.937 85.800 8.3010 ll.(i55 38.!I182 21.085 25.695 8(i.(i00 8.32(i7 11.547 3<».2K1 1 21,150 25.457 87.400 8.3523 11.442 39.6440 21,215 25.224 88.200 8.3777 11.338 40.0068 21,279 24,996 89.000 8.4030 11.236 40.3697 21,344 24,771 8!). 800 8.4281 11.13(i 40.7326 21,407 24.550 !)().()()() 8.4530 11.038 4 1 .0955 21,471 24.334 91. 400 8.4778 10.941 41.4583 21,534 24.121 92.200 8.5025 10.846 41.8212 21,. 596 23.!) 11 93.000 8.5270 10.753 42.1841 2 1 ,(i59 23.706 93.800 8.5514 10.6(.l 42.5470 21,721 2 3., 503 i»4.(iO() 8.5756 10.571 42,9098 21,782 23.305 95.400 8.5997 10.482 43.2727 21,843 23.109 9().2()() 8.6237 10.395 43.6356 21,904 22.917 97.000 8.6476 10.309 43.!)984 21,965 22.728 97.800 8.6713 10.225 44.3613 22,025 22.542 i)8.fi00 8.6948 10.142 44.7242 22,085 22.359 99.400 8.7183 10.060 45.0871 22,144 22.179 102.000 8.7936 9.804 46.2664 22,336 21.614 110.000 9.0178 9.091 49.8951 22.905 20.042 118.000 9.2313 8.475 53.5238 23.447 18.683 12(i.()0() !).4354 7.937 57.1526 23.f»66 17.497 134.()()0 !).6310 7.463 60.7813 24.4(i3 16.452 142.000 !).8190 7.042 64.4100 24.940 15.525 150.000 10.0000 6.667 68.0388 25.400 14.697 LENGTH-WEIGHT TABLES 415 Table 1-2. LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C= 2,000 x 10-7 WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS' (CM) KILOGRAM 0.200 1 .0000 5000.000 0.0907 2.540 11023.102 0.204 1 .0066 4901.961 0.0925 2.,5.57 10806.965 0.208 1.0132 4807. ()9.5 0.0943 2.573 10599.141 0.212 1.0196 4716.984 0.0962 2..590 10399.160 0.216 1.0260 4629.633 0.0980 2.606 10206..586 0.220 1.0323 4.545.461 0.0998 2.622 10021.012 0.224 1.038,5 4464.293 0.1016 2.638 9842.066 0.228 1.0446 4385.973 0.1034 2.653 9669.402 0.232 1.0.507 4310.3.52 0.1052 2.669 9.502.691 0.236 1.0567 4237.297 0.1070 2.684 9341.629 0.240 1.0627 416().676 0.1089 2.699 9185.938 0.244 1.0685 4098.371 0.1107 2.714 903.5.348 0.248 1.0743 4032.269 0.1125 2.729 8889.617 0.2.'i2 1.0801 3968.266 0.1143 2.743 8748.516 0.2,56 1.0858 3906.262 0.1161 2.758 8611.820 0.260 1.0914 3846.166 0.1179 2.772 8479.332 0.264 1.0970 3787.892 0.1197 2.786 83.50.8.59 0.268 1.1025 3731.356 0.1216 2.800 8226.219 0.272 1.1079 3676.484 0.1234 2.814 8105.246 0.276 1.1133 3623.202 0.1252 2.828 7987.781 0.280 1.1187 3571.442 0.1270 2.841 7873.672 0.284 1.1240 3.521.141 0.1288 2.855 7762.777 0.288 1.1292 3472.237 0.1306 2.868 7654.961 0.292 1.1344 3424.672 0.1324 2.881 75.50.098 0.296 1.1396 3378.393 0.1343 2.895 7448.070 0.300 1.1447 3333.348 0.1361 2.908 7348.766 0.304 1.1498 3289.48!) 0.1379 2.920 7252.070 0.308 1.1548 3246.769 0.1397 2.933 7157.891 0.312 1.1.598 3205.144 0.1415 2.946 7066.121 0.316 1.1647 3164.573 0.1433 2.958 6976.680 0.320 1.1696 3125.016 0.14.51 2.971 6889.469 0.324 1.1745 3086.436 0.1470 2.983 6804.414 0.328 1.1793 3048.796 0.1488 2.995 6721.434 0.332 1.1840 3012.064 0.1506 3.007 6640.453 0.336 1.1888 2976.207 0.1524 3.020 6.561.402 0.340 1.1935 2941.193 0.1542 3.031 6484.211 0.344 1.1981 2906.993 0. 1 560 3.043 6408.813 0.348 1.2028 2873.579 0.1578 3.055 6335.148 0.3.52 1.2074 2840.925 0.1,597 3.067 6263.160 0.35(i 1.2119 2809.005 0.1615 3.078 6192.785 0.360 1.2164 2777.794 0.1633 3.090 6123.977 0.364 1.2209 2747.269 0.1651 3.101 6056.684 0.3()8 1.2254 2717.408 0.1669 3.112 5990.848 0.372 1.2298 2688.188 0.1687 3.124 5926.434 0.376 1.2342 2659.591 0.1705 3.13.5 5863.387 0.380 1.2386 2631. .59.5 0.1724 3.146 5801.664 416 FISH HATCHERY MANAGEMENT Table 1-2. c= 2,000x10 ', continued WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.384 1.2429 2604.183 0.1742 3.157 5741.230 0.388 1.2472 2577.336 0.1760 3. 1 68 5682.043 0.392 1.2515 2551.037 0.1778 3.179 5624.066 0.396 1.2557 2525.26!) 0.1796 3.189 5567.258 0.400 1.2599 2500.0 Hi 0.1814 3.200 5511.586 0.404 1.2641 2475.264 0.1832 3.211 5457.016 0.408 1.2683 2450.997 0.1851 3.221 5403.516 0.412 1.2724 2427.201 0.1869 3.232 5351.055 0.416 1.2765 2403.863 0.1887 3.242 5299.602 0.420 1.2806 2380.969 0.1905 3.253 5249.129 0.424 1.2846 2358.507 ().1!)23 3.263 5199.609 0.428 1.2887 2336.465 0.1941 3.273 5151,016 0.432 1.2927 2314.831 0.1960 3.283 5103.320 0.436 1.2966 2293.594 0.1978 3.293 5056,500 0.440 1.3006 2272.743 0.1996 3.303 5010.535 0.444 1.3045 2252.268 0.2014 3.313 4965.395 0.448 1.3084 2232.159 0.2032 3.323 4921.059 0.452 1.3123 2212.406 0.2050 3.333 4877.512 0.456 1.3162 2192.999 0.20(i8 3.343 4834.727 0.460 1.3200 2173.929 0.2087 3.353 4792.688 0.464 1.3238 2155.188 0.2105 3.362 4751.371 0.468 1.3276 2136.768 0.2123 3.372 4710.758 0.472 1.3314 2118.660 0.2141 3.382 4670.840 0.476 1.3351 2100.856 0.21.59 3.391 4631.586 0.480 1.3389 2083.349 0.2177 3.401 4592.992 0.484 1.3426 2066.132 0.2195 3.410 4555.031 0.488 1.3463 2049.196 0.2214 3.419 4517.695 0.492 1.3499 2032.536 0.2232 3.429 4480.969 0.496 1.3536 2016.145 0.2250 3.438 4444.832 0.500 1.3572 2000.000 0.2268 3.447 4409.238 0.508 1.3644 1968.504 0.2304 3.466 4339.801 0.516 1.3715 1937.985 0.2341 3.484 4272.520 0.524 1.3786 1908.398 0.2377 3.502 4207.289 0.532 1.3856 1879.701 0.2413 3.519 4144.023 0.540 1.3925 1851.854 0.2449 3.537 4082.633 0.548 1.3993 1824.819 0.2486 3.554 4023.033 0.556 1.4061 1798.563 0.2522 3.571 3965.149 0.564 1.4128 1773.052 0.2558 3.589 3908.906 0.572 1.4195 1748.254 0.2595 3.605 3854.237 0..580 1.4260 1724.141 0.2631 3.622 3801.075 0.588 1.4326 1700.683 0.2(i67 3.639 3749.361 0.596 1.4390 1677.856 0.2703 3.655 3699.034 0.604 1.4454 1655.633 0.2740 3.671 3650.041 0.612 1.4518 1633.991 0.2776 3.688 3602.328 0.620 1.4581 1612.907 0.2812 3.704 3555.847 0.628 1.4643 1592.361 0.2849 3.719 3510.550 LENGIH-WKIGHT TABLES 417 Table 1-2. C = 2,0(){) X 10 \ CONTINUED WEIGHT/ 1. ()()() LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.(i3(i 1.4705 1572.331 0.2885 3.735 3466.393 0.644 1.4767 1552.799 0.2921 3.751 3423.333 0.652 1.4828 1.533.747 0.2!)57 3.766 3381.329 0.660 1.4888 1515.1.56 0.2994 3.782 3340.344 0.668 1.4948 1497.011 0.3030 3.797 3300.340 0.676 1 .5007 1479.295 0.3066 3.812 3261.283 0.684 1 .5066 1461.993 0.3103 3.827 3223.139 0.692 1.5125 1445.092 0.3139 3.842 3185.878 0.700 1.5183 1428.577 0.3175 3.856 3149.469 0.708 1.5241 1412.435 0.3211 3.871 3113.882 0.716 1..5298 1396.653 0.3248 3.886 3079.090 0.724 1 ..5354 1381.221 0.3284 3.900 3045.067 0.732 1.5411 1366.126 0.3320 3.914 3011.788 0.740 1.5467 1351.357 0.3357 3.929 2979.228 0.748 1.5522 1336.904 0.3393 3.943 2947.365 0.7.56 1.5577 1322.757 0.3429 3.957 2916.177 0.764 l.,5632 1308.906 0.3465 3.971 2885.641 0.772 1..5687 1295.343 0.3502 3.984 2855.738 0.780 1.5741 1282.057 0.3538 3.998 2826.449 0.788 1.5794 1269.042 0.3574 4.012 2797.7.54 0.796 1.5847 1256.287 0.3611 4.025 2769.636 0.804 1,5!)00 1243.787 0.3647 4.039 2742.078 0.812 1..5953 1231.533 0.3683 4.0.52 2715.063 0.820 1.6005 121!). 5 18 0.3719 4.065 2688.574 0.828 1.6057 1207.736 0.37.56 4.078 2662..598 0.836 1.6109 1196.178 0.3792 4.092 2637.119 0.844 1.6160 1184.840 0.3828 4.105 2612.123 0.852 1.6211 1173.715 0.3865 4.118 2587.596 0.860 1.6261 1162.797 0.3901 4.130 2563.525 0.868 1.6312 1152.080 0.3937 4.143 2539.898 0.876 1.6362 1141.559 0.3973 4.1.56 2516.703 0.884 1.6411 1131.228 0.4010 4.168 2493.928 0.892 1.6461 1121.083 0.4046 4.181 2471. .561 0.900 1.6510 1111.117 0.4082 4.193 2449.592 0.908 1.6558 1101.328 0.4119 4.206 2428.009 0.916 l.fi()()7 1091.709 0.4155 4.218 2406.804 0.924 1.6655 1082.257 0.4191 4.230 2385.966 0.932 1.6703 1072.968 0.4227 4.243 2365.486 0.940 1.6751 1063.836 0.4264 4.255 2345.354 0.948 1 .6798 1054.85S) 0.4300 4.267 2325.563 0.956 1 .6845 1046.031 0.4336 4.279 2306.102 0.964 1.6892 1037.351 0.4373 4.291 2286.964 0.972 1 .6939 1028.813 0.4409 4.302 2268.142 0.980 1.6985 1020.415 0.4445 4.314 2249.626 0.988 1.7031 1012.1.52 0.4481 4.326 2231.411 0.996 1.7077 1004.022 0.4518 4.338 2213.488 418 FISH HATCHERY MANAGEMENT Table 1-2. C= 2,000 X 10 \ CONTINUED WEIGHT/ 1,000 LKNGTH KISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 1.040 1.7325 961.539 0.4717 4.400 2119.829 1.120 1.7758 892.859 0..5080 4.511 1968.416 1.200 1.8171 833.337 0.5443 4.615 1837.191 1.2H0 1 .85()6 781.254 0.5806 4.716 1722.368 1.360 1.8945 735.299 0.6169 4.812 1621.054 1.440 1.9310 694.449 0.6532 4.905 1530.998 1..520 1.9661 657.900 0.6895 4.994 14,50.420 1 .600 2.0000 625.006 0.7257 5.080 1377.900 l.(i80 2.0328 595.244 0.7620 5.163 1312.287 1.760 2.0646 568.188 0.7983 5.244 1252.638 1.840 2.0954 543.484 0.834() 5.322 1198.177 1.920 2.1253 520.839 0.870!) 5.398 1148.253 2.000 2.1544 500.006 0.9072 5.472 1102.323 2.080 2.1828 480.775 0.9435 5.544 10.59.927 2.160 2.2104 462.969 0.9797 5.614 1020.671 2.240 2.2374 446.435 1.0160 5.683 984.219 2.320 2.2637 431.041 1.0523 5.750 950.28 1 2.400 2.2894 416.673 1.0886 5.815 918.605 2.480 2.3146 403.232 1 . 1 249 5.879 888.973 2.,560 2.3392 390.631 1.1612 5.942 861.193 2.640 2.3633 378.794 1.1975 6.003 835.096 2.720 2.3870 367.653 1.2338 6.063 810.535 2.800 2.4101 357.148 1.2700 6.122 787.377 2.880 2.4329 347.228 1.3063 6.179 765.505 2.960 2.4552 337.843 1.3426 6.236 744.816 3.040 2.4771 328.953 1.3789 6.292 725.216 3.120 2.4986 320.518 1.4152 6.347 706.621 3.200 2.5198 312.505 1.4515 6.400 688.955 3.280 2.5407 304.883 1.4878 6.453 672.152 3.360 2.5611 297.624 1.5240 6.505 656.148 3.440 2..5813 290.703 1.5603 6.557 640.889 3.520 2.6012 284.096 1.5966 6.607 626.323 3.600 2.6207 277.783 1.6329 6.657 612.405 3.680 2.6400 271.744 1.6692 6.706 599.092 3.760 2.6590 265.962 1.7055 6.754 586.346 3.840 2.6777 260.421 1.7418 6.801 574.130 3.920 2.6962 255.107 1.7780 6.848 ,562.413 4.000 2.7144 2,50.005 1.8143 6.895 551.165 4.080 2.7324 245.103 1 .8506 6.940 540.358 4.160 2.7,501 240.389 1.8869 6.985 529.967 4.240 2.7676 235.854 1.9232 7.030 519.967 4.320 2.7849 231.486 1 .9595 7.074 510.338 4.400 2.8020 227.277 1.9958 7.117 ,501.060 4.480 2.8189 223.219 2.0321 7.160 492.112 4.560 2.8356 219.302 2.0683 7.202 483.479 4.640 2.8521 215.521 2.1046 7.244 475.143 LENGTH-WEIGHT TABLES 419 Table 1-2. C = 2,000 X 10 , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 4.720 2.8684 211.869 2.1409 7.286 467.090 4.800 2.8845 208.337 2.1772 7.327 459.305 4.880 2.9004 204.922 2.2135 7.367 451.775 4.!)fi() 2.9162 201.617 2.2498 7.407 444.489 5.200 2.9625 192.308 2.3587 7..525 423.965 5.600 3.0366 178.572 2.5401 7.713 393.682 6.000 3.1072 166.667 2.7215 7.892 367.437 6.400 3.1748 156.250 2.9030 8.064 344.472 6.800 3.2396 147.0.59 3.0844 8.229 324.209 7.200 3.3019 138.889 3.26,59 8.387 306.198 7.600 3.3620 131.579 3.4473 8.,539 290.082 8.000 3.4199 125.000 3.6287 8.687 275.578 8.400 3.4760 119.048 3.8102 8.829 262.455 8.800 3.5303 113.637 3.9916 8.967 2,50.526 9.200 3.5830 108.696 4.1730 9.101 239.633 9.600 3.6342 104.167 4.3545 9.231 229.649 10.000 3.6840 100.000 4.5359 9.357 220.463 10.400 3.7325 96.154 4.7173 9.481 211.983 10.800 3.7798 92.593 4.8988 9.601 204.132 11.200 3.8259 89.286 5.0802 9.718 196.842 11.600 3.8709 86.207 5.2616 9.832 190.054 12.000 3.9149 83.334 5.4431 9.944 183.719 12.400 3.9579 80.645 5.6245 10.053 177.793 12.800 4.0000 78.125 5.8060 10.160 172.237 13.200 4.0412 75.758 5.1*874 10.265 167.017 13.600 4.0816 73.530 6.1688 10.367 162.105 14.000 4.1213 71.429 6.3.503 10.468 157.473 14.400 4.1602 69.445 6.5317 10.,567 153.099 14.800 4.1983 67.568 6.7131 10.664 148.961 15.200 4.2358 65.790 6.8946 10.7,59 145.041 15.600 4.2727 64.103 7.0760 10.853 141.322 16.000 4.3089 62.500 7.2574 10.945 137.789 16.400 4.3445 60.976 7.4389 11.035 134.428 16.800 4.3795 59.524 7.6203 11.124 131.227 17.200 4.4140 58.140 7.8018 11.212 128.176 17.600 4.4480 56.818 7.9832 11.298 125.263 18.000 4.4814 55.556 8.1646 11.383 122.479 18.400 4.5144 54.348 8.3461 11.466 119.816 18.800 4.5468 53.192 8.5275 1 1 .549 117.267 19.200 4.5789 52.083 8.7090 11,630 114.824 19.600 4.6104 51.020 8.8904 11.710 112.481 20.000 4.6416 50.000 9.0718 11.790 110.231 20.400 4.6723 49.020 9.2.533 11.868 108.070 20.800 4.7027 48.077 !).4347 1 1 .945 105.991 21.200 4.7326 47.170 !).6161 12.021 103.992 21.600 4.7622 46.296 9.7976 12.096 102.066 420 FISH HAICHKRY MANAGEMENT Table 1-2. c = 2,000 x lo"'', continued WEIGHT/ 1 ,()()() LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 22.000 4.7914 4.5.455 9.i)7<)() 12.170 100.210 22.400 4.8203 44.(i43 10.1()()4 12.244 98.421 22.800 4.8488 43.860 10.3419 12.316 96.694 23.200 4.8770 43.103 10..5233 12.388 95.027 23.600 4.9049 42.373 10.7048 12.458 93.416 24.000 4.9324 4 1 .667 10.88fi2 12.528 91.859 24.400 4.9597 40.984 11.0()7() 12..598 90.353 24.800 4.9866 40.323 n.2491 12.666 88.896 2.5.400 5.0265 39.370 ll.,5213 12.767 86.796 26.200 5.0788 38.168 11.8841 12.900 84.146 27. ()()() 5.1299 37.037 12.2470 13.030 81.(i52 27.800 5.1801 35.971 12.6099 13.157 79.303 28.600 5.2293 34.965 12.9728 13.282 77.084 29.400 .5.2776 34.014 13.33.56 13.405 74.i)87 30.200 5.3251 33.112 13.6985 13.526 73.000 3L0()() 5.3717 32.258 14.0614 13.644 71.117 3L8()() 5.4175 31.446 14.4243 13.760 69.327 32.600 .5.4626 30.675 14.7871 13.875 67.626 33.400 5.5069 29.940 15.1.500 13.987 66.006 34.200 5.5.505 29.240 1.5.5129 14.098 64.462 35.000 5.5934 28.571 15.8758 14.207 62.989 35.800 5.6357 27.933 16.2386 14.315 61. .581 36.600 5.6774 27.322 16.6015 14.421 60.235 37.400 5.7185 26.738 16.9644 14.525 58.947 38.200 5.7590 26.178 17.3272 14.628 57.712 39.000 5.7989 25.64 1 17.6901 14.729 56.529 39.800 5.8383 25.126 18.0530 14.829 55.392 40.600 5.8771 24.630 18.41,59 14.928 .54.301 4L40() 5.9155 24.155 18.7787 15.025 53.252 42.200 5.9533 23.697 19.1416 15.121 52.242 43.000 .5.9907 23.256 19.5045 15.21() 51.270 43.800 6.0277 22.831 19.8674 15.310 50.334 44.()00 6.0641 22.421 20.2302 15.403 49.431 45.400 6.1002 22.026 20.5931 15.494 48.560 46.200 6.1358 21.645 20.9560 15.585 47.719 47.000 ().171() 21.277 21.3188 15.674 46.907 47.800 (i.2()58 20.920 21.6817 15.763 46.122 48.600 6.2403 20.576 22.0446 15.8,50 45.362 49.400 6.2743 20.243 22.4075 15.937 44.628 50.200 6.3080 li).920 22.7703 16.022 43.917 ,5L()00 6.3413 19.608 23.1332 16.107 43.228 5L8()() 6.3743 19.305 23.49()1 l(i.l91 42.5(i0 52.(.00 (i.407() 19.011 23.8590 16.274 41.913 ,53.400 6.4393 18.727 24.2218 16.35() 41.285 54.200 6.4713 18.4.50 24.5847 16.437 40.676 5.5.000 6..5030 18.182 24.9476 16.517 40.084 LENGTH-WEIGHl TABLES 421 Table 1-2. C = 2,000 X 10 , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CMJ KILOGRAM F,5.H0{) 6..5343 17.921 25.3105 16..597 39..509 ,5fi.fiOO 6.,56.54 17.668 25.6733 16.676 38.951 ,57.400 6.,5962 17.422 26.0362 16.754 38.408 ,58.200 6.6267 17.182 26.3991 16.832 37.880 ,')9.0()0 6.6.569 Ui.949 26.7619 16.909 37.366 ,59.800 6.6869 16.722 27.1248 16.985 36.867 fiO.fiOO 6.7166 16.,502 27.4877 17.060 36.380 fi 1.400 6.7460 16.287 27.8506 17.135 35.906 ()2.20() 6.77,52 1().()77 28.2134 17.209 35.444 fi3.000 6.8041 15.873 28.57()3 17.282 34.994 63.800 6.8328 15.674 28.9392 17.3.55 34.,5.55 64.600 6.8612 1.5.480 29.3021 17.427 34.127 6.5.400 6.8894 15.291 29.6649 17.499 33.710 66.200 6.9174 15.106 30.0278 17.570 33.302 67.000 6.9451 14.925 30.3907 17.641 32.905 67.800 6.9727 14.749 30.7536 17.711 32.516 68.600 7.0000 14.577 31.1164 17.780 32.137 69.400 7.0271 14.409 31.4793 17.84il 31.767 70.200 7.0540 14.245 31.8422 17.917 31.405 71.000 7.0807 14.084 32.20,50 17.98.5 31.051 71.800 7.1072 13.928 32.5679 18.0.52 30.705 72.fi0() 7.1335 13.774 32.9308 18.119 30.367 73.400 7.1.596 13.624 33.2937 18.18.5 30.036 74.200 7.18.55 13.477 33.6566 18.251 29.712 7.5. ()()() 7.2112 13.333 34.0194 18.317 29.395 7.5.800 7.2368 13.193 34.3823 18.381 29.085 76.600 7.2622 13.055 34.74.52 18.446 28.781 77.400 7.2874 12.920 3.5.1080 18.510 28.483 78.200 7.3124 12.788 35.4709 18.573 28.192 79.000 7.3372 12.658 35.8338 18.637 27.907 79.800 7.3619 12.531 36.1967 18.699 27.627 80.600 7.3864 12.407 36.5595 18.7(i2 27.353 81.400 7.4108 12.285 36.9224 18.823 27.084 82.200 7.43,50 12.165 37.2853 18.885 26.820 83.000 7.4590 12.048 37.6481 18.946 26..562 83.800 7.4829 11.933 38.0110 19.007 26.308 84.600 7.5067 11.820 38.3739 19.067 26.059 8.5.400 7..5302 11.710 38.73(i8 19.127 25.815 86.200 7..5,537 11.601 39.09!)7 19.186 25.576 87. ()()() 7.5770 11.494 39.4625 19.246 25.340 87.800 7.6001 1 1 .390 39.8254 19.304 25.110 88.600 7.6231 11.287 40.1883 1 9.363 24.883 89.400 7.6460 11.186 40.55 1 1 19.421 24.660 90.200 7.6688 11.086 40.9140 19.479 24.441 91.000 7.6914 10.989 41.27(i9 19.536 24.227 91.800 7.7138 10.893 41.()398 19..593 24.015 422 FISH HATCHERY MANAGEMENT Table 1-2. c = 2,000 x lo"'', continued WEIGHT/ 1,000 LENGTH FISH/ WEIGH! LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 92.600 7.7362 10.799 42.0026 19.(i5() 23.808 93.400 7.7584 10.707 42.3655 19.706 23.604 94.200 7.7805 10.(il6 42.7284 19.762 23.404 95.000 7.8025 10.52() 43.0912 19.818 23.206 95.800 7.8243 10.438 43.4541 19.874 23.013 96.600 7.8460 10.352 43.8170 19.929 22.822 97.400 7.8676 10.267 44.1799 19.984 22.635 98.200 7.8891 10.183 44.5427 20.038 22.4.50 99.000 7.9105 10.101 44.9056 20.093 22.269 99.800 7.9317 10.020 45.2685 20.147 22.090 106.000 8.0927 9.434 48.0807 20.555 20.798 114.000 8.2913 8.772 51.7095 21.060 19.339 122.000 8.4809 8.197 55.3382 21.542 18.071 130.000 8.6624 7.692 58.96(i9 22.002 16.959 138.000 8.8365 7.246 62.5957 22.445 15.976 1 46.000 9.0041 6.849 66.2244 22.870 15.100 154.000 9.1657 6,494 69.8531 23.281 14.316 162.000 9.3217 6.173 73.4819 23.677 13.609 170.000 9.4727 5.882 77.1106 24.061 12.968 178.000 9.6190 5.618 80.7394 24.432 12.386 186.000 9.7610 5.376 84.3681 24.793 11.853 194.000 9.8990 5.155 87.9968 25.143 11.364 LENGTH-WEIGHT TABLES 423 Table 1-3. LENCrH-WF.IGH 1 RKI.AIIONSHIPS FOR FISH WriH C = 2,.iO()x 10- ' WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH fish; FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.250 1 .0000 4000.002 0.1134 2..540 8818.480 0.254 1.0053 3937.010 0.1152 2.553 8679.609 0.25S 1.0106 3875.972 0.1170 2.567 8545.043 0.2(i2 1.0157 3816.798 0.1188 2.580 8414.586 0.2()(i 1.0209 3759.403 0.1207 2.,593 8288.055 0.270 1.0260 3703.709 0.1225 2.606 8165.270 0.274 1.0310 3649.641 0.1243 2.619 8046.070 0.278 1.0360 3597.128 0.1261 2.631 7930.301 0.282 1.0410 3546.106 0.1279 2.644 7817.813 ().28(; 1.04,59 3496.510 0.1297 2.656 7708.477 0.290 1.0.507 3448.283 0.1315 2.669 7602.1,52 0.294 1 .0555 3401.368 0.1334 2.681 7498.723 0.298 1.0603 3355.713 0.1352 2.693 7398.070 0.302 1 .0650 3311.267 0.1370 2.705 7300.082 0.306 1.0697 3267.983 0.1388 2.717 7204.6,56 0.310 1.0743 3225.816 0.1406 2.729 7111.695 0.314 1.0789 3184.723 0.1424 2.740 7021.102 0.318 1.0835 3144.664 0.1442 2.752 6932.785 0.322 1.0880 3105.600 0.1461 2.764 6846.664 0.32fi 1.0925 3067. 4!)5 0.1479 2.775 6762.660 0.330 1.0970 3030.313 0.1497 2.786 6680.688 0.334 1.1014 2994.023 0.1515 2.797 6600.680 0.338 1.10,58 2958.591 0.1533 2.809 6522.566 0.342 1.1101 2923.988 0.1551 2.820 6446.281 0.346 1.1144 2890.185 0.1569 2.831 6371.7,58 0.350 1.1187 2857.154 0.1588 2.841 6298.938 0.354 1.1229 2824.870 0.1606 2.852 6227.762 0.358 1.1271 2793.308 0.1624 2.863 6158.180 0.362 1.1313 2762.443 0.1642 2.874 6090.133 0.366 1.1355 2732.252 0.1660 2.884 6023.,574 0.370 1.1396 2702.715 0.1678 2.895 5958.457 0.374 1.1437 2673.809 0.1696 2.905 5894.730 0.378 1.1478 2645.515 0.1715 2.915 5832.3.52 0.382 1.1518 2617.813 0.1733 2.926 5771.281 0.386 1 . 1 558 2590. 68() 0.1751 2.936 5711.477 0.390 1.1598 2564.115 0. 1 769 2.946 5652.898 0.394 1.1637 2538.084 0.1787 2.956 5595.,508 0.398 1.1677 2512.575 0.1805 2.966 5,539.273 0.402 1.1716 2487.575 0.1823 2.976 5484.1.56 0.406 1.1754 2463.067 0.1842 2.986 ,5430.125 0.410 1.1793 2439.037 0.1860 2.i)!)5 5377.148 0.414 1.1831 2415.472 0.1878 3.005 5325.195 0.418 1.1869 2392.357 0.1896 3.015 .5274.238 0.422 1 . 1 907 2369.681 0.1914 3.024 ,5224.246 0.426 1.1944 2347.431 0.1932 3.034 5175.191 424 FISH HATCHERY MANAGEMENT Table 1-3. c = 2,500 x lo '.continued WEIGHT/ 1 .()()() LENGIH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.430 1.1981 2325.,594 0.1950 3.043 5127.051 0.434 1.2018 2304.161 0.1969 3.053 .5079.797 0.138 1.2055 2283.118 0.1987 3.062 5033.406 0.442 1.2092 2262.457 0.2005 3.071 4987.855 0.44() 1.2128 2242.166 0.2023 3.081 4943.121 0.450 1.2164 2222.235 0.2041 3.090 4899.184 0.454 1.2200 2202.656 0.2059 3.099 48.56.020 0.458 1.2236 2183.419 0.2077 3.108 4813.609 0.4f)2 1.2272 2164.515 0.2096 3.117 4771.934 0.4fi6 1.2307 2145.936 0.21 14 3.126 4730.973 0.470 1.2342 2127.673 0.2132 3.135 4690.707 0.474 1.2377 2109.718 0.21.50 3.144 4651.125 0.478 1.2412 2092.063 0.2168 3.153 4612.203 0.482 1.2446 2074.702 0.2186 3.161 4573.926 {).48fi 1.2480 2057.626 0.2204 3.170 4536.281 0.490 1.2515 2040.830 0.2223 3.179 4499.250 0.494 1.2549 2024.305 0.2241 3.187 4462.820 0.498 1.2582 2008.045 0.2259 3.196 4426.977 0..504 1.2633 1984.127 0.2286 3.209 4374.246 0.512 1.2699 19.53.125 0.2322 3.226 4305.898 0,520 1.2765 1923.078 0.2359 3.242 4239.652 0.528 1.2830 1893.941 0,2395 3.2,59 4175.418 0.53(i 1.2895 1865.673 0.2431 3.275 4113.098 0.544 1.2958 1838.237 0.24(i8 3.291 4052.614 0.552 1.3022 1811.596 0.2504 3.307 3993.881 0.560 1.3084 1785.717 0.2540 3.323 3936.826 0.568 1.3146 1760.566 0.2576 3.339 3881.379 0.576 1.3208 1736.114 0.2613 3.355 3827.471 0.584 1.3269 1712.332 0.2<)49 3.370 3775.041 0.592 1.3329 1689.192 0.2685 3.386 3724.027 0.600 1.3389 1666.670 0.2722 3.401 3674.374 0.608 1.3448 1644.740 0.2758 3.416 3626.028 0.(il6 1.3,507 1623.380 0.2794 3.431 3578.937 0.624 1.3,565 1602.568 0.2830 3.445 3533.053 0.632 1.3623 1582.283 0.2867 3.460 3488.332 0.640 1.3680 1.562., 504 0.2903 3.475 3444.728 0.648 1.3737 1543.214 0.2939 3.489 3402.201 0.656 1.3793 1524.395 ().297<; 3. ,503 3360.711 0.664 1.3849 1506.029 0.3012 3.518 3320.221 0.672 1.3904 1488.100 0.3048 3.532 3280.695 0.680 1 .39.59 1470.593 0.3084 3.546 3242.099 0.(i88 1.4014 1453.493 0.3121 3.5.59 3204.400 0.fi!>6 1.4068 1436.787 0.3157 3.573 3167.569 0.704 1.4121 1420.460 0.3193 3.587 3131.574 0.712 1.4175 1404.500 0.3230 3.600 3096.388 0.720 1.4228 1388.894 0.3266 3.614 3061.984 LENGTH-WEIGHT TABLES 425 Table 1-3. C = 2, .500 X 10 ' , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHI LENGTH FISH, FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.728 1.4280 1373.632 0.3302 3.627 3028.336 0.736 1.4332 1358.701 0.3338 3.640 2995.420 0.744 1.4384 1344.092 0.3375 3.6,54 2963.211 0.752 1.4435 1329.793 0.3411 3.667 2931.688 0.760 1.4486 1315.795 0.3447 3.680 2900.828 0.768 1.4537 1302.089 0.3484 3.692 2870.612 0.776 1.4587 1288.666 0.3520 3.705 2841.018 0.784 1.4637 1275.516 0.3556 3.718 2812.028 0.792 1.4687 1262.632 0.3592 3.730 2783.624 0.800 1.4736 1250.006 0.3629 3.743 2755.788 0.808 1.4785 1237.630 0.3665 3.755 2728.503 0.816 1.4834 1225.496 0.3701 3.768 2701.7,53 0.824 1.4882 1213.598 0.3738 3.780 2675.523 0.832 1.4930 1201.929 0.3774 3.792 2649.797 0.840 1.4978 1190.482 0.3810 3.804 2624.561 0.848 1.5025 1179.251 0.3846 3.816 2,599.801 0.856 l.,5072 1168.230 0.3883 3.828 2575..104 0.864 1.5119 1157.414 0.3919 3.840 2.551.657 0.872 1.5166 1146.795 0.3955 3.852 2528.248 0.880 1.5212 1136.370 0.3992 3.864 2,505.264 0.888 1.5258 1126.132 0.4028 3.875 2482.694 0.896 1.5303 1116.078 0.40f)4 3.887 2460.527 0.904 1.5349 1106.201 0.4100 3.899 2438.7,53 0.912 1.5394 1096.498 0.4137 3.910 2417.360 0.920 1.5439 1086.963 0.4173 3.921 2396.340 0.928 1.5483 1077.593 0.4209 3.933 2375.682 0.936 1.5528 1068.382 0.4246 3.944 23,55.377 0.944 1.5572 1059.328 0.4282 3.955 2335.417 0.952 1.5616 1050.427 0.4318 3.966 2315.791 0.960 1.5659 1041.673 0.4354 3.977 2296.493 0.968 1.5703 1033.064 0.4391 3.989 2277.514 0.976 1.5746 1024. .596 0.4427 3.999 2258.846 0.984 1.5789 1016.266 0.4463 4.010 2240.481 0.992 1.5832 1008.071 0.4,500 4.021 2222.413 1.000 1.5874 1000.000 0.4536 4.032 2204.620 1.080 1.6286 925.927 0.4899 4.137 2041.318 1.160 1.6679 862.072 0.5262 4.236 1900.,541 1.240 1.7054 806.455 0..5625 4.332 1777.928 1.320 1.7413 757.580 0.5987 4.423 1670.177 1.400 1.7758 714.291 0.6350 4.511 1574.740 1.480 1.8090 675.681 0.6713 4..595 1489.620 1.560 1.8410 641.031 0.7076 4.676 1413.230 1.640 1.8720 609.762 0.7439 4.755 1344.293 1.720 1.9019 581.401 0.7802 4.831 1281.769 1.800 1.9310 555.562 0.81()5 4.905 1224.802 1.880 1.9592 531.921 0.8527 4.976 1172.684 426 FISH HAICHKRY MANAGKMKN T Table 1-3. c; = 2,. '■)()() > 10 ■ ', CONIINl LI) WEIGHT/ 1, ()()() LKNGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 1 .960 1 .9866 510.210 0.8890 5.046 1 121.820 2.040 2.0132 490.202 0.9253 5.114 1080. 709 2.120 2.03!)2 471.704 0.9(il6 5.180 1039.928 2.200 2.0646 454.552 0.9979 5.244 1002.113 2.280 2.0893 438. (;03 1.0342 5.307 966.952 2.360 2.1134 423.735 1 .0705 5.368 934.174 2.440 2.1370 409.842 1.1067 5.428 !)03.546 2.520 2.1602 396.831 1.1430 5.487 874.862 2.600 2.1828 384.621 1 . 1 793 5.544 847.944 2.680 2.2049 373.140 1.2156 5.601 822.f)32 2.760 2.2267 362.324 1.2519 5.656 798.788 2.840 2.2480 352.118 1.2882 5.710 776.287 2.920 2.2689 342.471 1.3245 5.763 755.019 3.000 2.2894 333.339 1.3608 5.815 734.885 3.080 2.3096 324.681 1.3970 5.866 715.798 3.160 2.3294 316.461 1.4333 5.917 ()!)7,676 3.240 2.3489 308.647 1.4(i9(i 5.966 680.450 3.320 2.3681 301.210 1.5059 6.015 6(i4.053 3.400 2.3870 2!)4.123 1.5422 6.0(i3 ()48.429 3.480 2.4055 287.361 1.5785 <>.11() 633,522 3.560 2.4238 280.904 1.6148 6.157 (i 19.286 3.640 2.4418 274.730 1.6510 6.202 605.676 3.720 2.4596 268.822 1.6873 6.247 592.650 3.800 2.4771 20.000 8.4343 6.667 68.0388 21.423 14.697 158.000 8.5817 6.329 71.6675 21.797 13.953 Ififi.OOO 8.7241 6.024 75.2962 22.1,'".9 13.281 174.000 8.8621 5.747 78.9250 22.510 12.670 182.000 8.9959 5.495 82.5537 22.850 12.113 190.000 9.1258 5.263 86.1825 23.180 11.603 198.000 9.2521 5.051 89.8112 23.500 11.134 206.000 9.3751 4.854 93.4399 23.813 10.702 214.000 9.4949 4.673 97.0687 24.117 10.302 222.000 9.6118 4.505 100.6974 24.414 9.931 230.000 9.7259 4.348 104.3261 24.704 9.585 238.000 9.8374 4.202 107.9549 24.987 9.263 24().000 9.9464 4.065 111.5836 25.264 8.962 LENGTH-WEIGHT TABLES 431 Table 1-4. LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C= 3,000 x 10-7 WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS! (CM) KILOGRAM 0.300 1.0000 3333.335 0.1361 2.540 7348.734 0.304 1.0044 3289.476 0. 1 379 2.551 7252.043 0.308 1.0088 3246.756 0.1397 2.562 7157.8.59 0.312 1.0132 3205.131 0.1415 2.573 7066.094 0.316 1.0175 3164..561 0.1433 2.,584 6976.652 0.320 1.0217 3125.004 0.1451 2.. 595 6889.445 0.324 1.0260 3086.424 0.1470 2.606 6804.391 0.328 1.0302 3048.785 0.1488 2.617 6721.410 0.332 1.0344 3012.053 0. 1 506 2.627 6640.430 0.336 1.0385 2976.196 0.1524 2.638 6561.379 0.340 1.0426 2941.182 0.1542 2.648 6484.188 0.344 1.0467 2906.983 0.1560 2.6.59 6408.789 0.348 1.0507 2873.570 0.1578 2.669 6335.125 0.352 1.0547 2840.916 0.1597 2.679 6263.137 0.356 1.0587 2808.996 0.1615 2.689 6192.766 0.360 1.0627 2777.785 0.1633 2.699 6123.957 0.364 1.0666 2747.260 0.1651 2.709 6056.664 0.368 1.0705 2717.399 0.1669 2.719 .5990.828 0.372 1.0743 2688.180 0.1687 2.729 5926.414 0.376 1.0782 2659.583 0.1706 2.739 5863.367 0.380 1.0820 2631.587 0.1724 2.748 5801.648 0.384 1.0858 2604.175 0.1742 2.7,58 5741.215 0.388 1.0895 2577.328 0.1760 2.767 .%82.027 0.392 1.0933 2551.029 0.1778 2.777 5624.047 0.396 1.0970 2525.261 0.1796 2.786 5567.238 0.400 1.1006 2500.009 0.1814 2.796 5511.566 0.404 1.1043 2475.257 0.1833 2.805 5457.000 0.408 1.1079 2450.990 0.1851 2.814 5403.500 0.412 1.1115 2427.194 0.1869 2.823 5351.039 0.416 1.1151 2403.856 0.1887 2.832 5299.586 0.420 1.1187 2380.962 0.1905 2.841 5249.113 0.424 1.1222 2358.500 0.1923 2.850 5199.594 0.428 1.1257 2336.458 0.1941 2.8,59 5151.000 0.432 1.1292 2314.825 0.1960 2.868 5103.309 0.436 1.1327 2293.588 0.1978 2.877 5056.488 0.440 1.1362 2272.737 0.1996 2.886 .5010.520 0.444 1.1396 2252.262 0.2014 2.895 4965.379 0.448 1.1430 2232.153 0.2032 2.903 4921.047 0.452 l.U lo ', continued WEIGHT/ 1, ()()() LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM •t.()40 2.2600 247.529 1.8325 5.740 545.708 4.120 2.2748 242.723 1.8688 5.778 535.112 4.200 2.2894 238.100 1.9050 5.815 524.919 4.280 2.3039 233.649 1.9413 5.852 515.108 4.360 2.3181 229.362 1.9776 5.888 505.656 4.440 2.3322 225.230 2.0139 5.924 496.545 4.520 2.3461 221.243 2.0502 5.959 487.757 4.600 2.3599 217.396 2.0865 5.994 479.274 4.680 2.3735 213.679 2.1228 6.029 471.082 4.760 2.3869 210.088 2.1591 6.063 463.164 4.840 2.4002 206.616 2.1953 6.097 455.509 4.920 2.4134 203.256 2.2316 6.130 448.102 5.000 2.4264 200.000 2.2680 6.163 440.924 5.400 2.4895 185.185 2.4494 6.323 408.263 5.800 2.5495 172.414 2.6308 6.476 380.107 6.200 2.6068 161.290 2.8123 6.621 355.584 6.600 2.6617 151.515 2.9937 6.761 334.034 7.000 2.7144 142.857 3.1751 6.895 314.946 7.400 2.7652 135.135 3.3566 7.024 297.922 7.800 2.8141 128.205 3.5380 7.148 282.644 8.200 2.8614 121.951 3.7194 7.268 268.856 8.600 2.9072 116.279 3.9009 7.384 256.352 9.000 2.9516 111.111 4.0823 7.497 244.958 9.400 2.9947 106.383 4.2638 7.607 234.535 9.800 3.0366 102.041 4.4452 7.713 224.962 10.200 3.0773 98.039 4.6266 7.816 216.140 10.600 3.1171 94.340 4.8081 7.917 207.984 11. ()()() 3.1558 90.909 4.9895 8.016 200.421 11.400 3.1936 87.720 5.1709 8.112 193.388 11.800 3.2305 84.746 5.3524 8.205 186.833 12.200 3.2666 81.967 5.5338 8.297 180.707 12.600 3.3019 79.365 5.7152 8.387 174.970 13.000 3.3365 76.923 5.8967 8.475 169.587 13.400 3.3704 74.627 6.0781 8.561 164.524 13.800 3.4036 72.464 6.2595 8.645 159.756 14.200 3.4362 70.423 6.4410 8.728 155.255 14.600 3.4681 68.493 6.6224 8.809 151.002 15.000 3.4995 66.667 6.8039 8.889 146.975 15.400 3.5303 64.935 6.9853 8.967 143.158 15.800 3.5606 63.291 7.1667 9.044 139.533 16.200 3.5905 61.728 7.3482 9.120 136.088 l(i.600 3.6198 60.241 7.5296 9.194 132.808 17.000 3.6486 58.824 7.7111 9.267 129.684 17.400 3.6770 57.471 7.8925 9.340 126.702 17.800 3.7050 56.180 8.0739 9.411 123.855 18.200 3.7325 54.945 8.2554 9.481 121.133 LENGTH-WEIGHT TABLES 443 Table 1-5. C= S.-SOOx 10 ' , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH ILBI (INCHES) POUND (GRAMS) (CM) KILOGRAM 18.600 3.7597 53.764 8.4368 9.550 118.528 19.000 3.7864 52.632 8.6182 9.617 116.033 19.400 3.8128 51. .546 8.7997 9.685 113.640 19.800 3.8388 50.505 8.9811 9.751 111.344 20.200 3.8645 49.505 9.1625 9.816 109.140 20.r.oo 3.8898 48.544 9.3440 9.880 107.021 21.000 3.9149 47.619 9.5254 9.944 104.982 21.400 3.9396 46.729 9.7069 10.006 103.020 21.800 3.9640 45.872 9.8883 10.068 101.129 22.200 3.9881 45.045 10.0697 10.130 99.307 22.600 4.0119 44.248 10.2512 10.190 97.550 23.000 4.0354 43.478 10.4326 10.2,50 95.853 23.400 4.0587 42.735 10.6140 10.309 94.215 23.800 4.0816 42.017 10.7955 10.367 92.631 24.200 4.1044 41.322 10.9769 10.425 91.100 24.600 4.1269 40.650 11.1583 10.482 89.619 2.5.000 4.1491 40.000 11.3398 10.539 88.185 25.800 4.1929 38.760 11.7027 10.6,50 85.450 26.600 4.2358 37.594 12.0656 10.7,59 82.880 27.400 4.2779 36.496 12.4285 10.866 80.460 28.200 4.3191 35.461 12.7913 10.971 78.178 29.000 4.3596 34.483 13.1542 11.073 76.021 29.800 4.3993 33.557 13.5171 11.174 73.980 30.600 4.4383 32.680 13.8800 11.273 72.046 31.400 4.4767 31.847 14.2428 11.371 70.211 32.200 4.5144 31.056 14.6057 11.466 68.466 33.000 4.5514 30.303 14.9686 11. ,561 66.807 33.800 4.5879 29.586 15.3314 11.653 65.225 34.600 4.6238 28.902 15.6943 11.745 63.717 35.400 4.6592 28.249 16.0572 11.834 62.277 36.200 4.6940 27.624 16.4201 11.923 60.901 37.000 4.7284 27.027 16.7829 12.010 59.584 37.800 4.7622 26.455 17.1458 12.096 58.323 38.600 4.7956 25.907 17.5087 12.181 57.114 39.400 4.8285 25.381 17.8716 12.264 55.955 40.200 4.8609 24.876 18.2344 12.347 .54.841 4 1 .000 4.8930 24.390 18.5973 12.428 53.771 41.800 4.9246 23.923 18.9602 12..508 52.742 42.600 4.9558 23.474 19.3230 12.588 51.752 43.400 4.9866 23.041 19.68.59 12.666 50.798 44.200 5.0171 22.624 20.0488 12.743 49,878 45.000 5.0472 22.222 20.4117 12.820 48.991 45.800 5.0769 21.834 20.7745 12.895 48.136 46.600 5.1063 2 1 .459 21.1374 12.970 47.309 47.400 5.1353 21.097 21., 5003 13.044 46.511 48.200 5.1641 20.747 21.8632 13.117 45.739 444 FISH HATCHERY MANAGEMENT Table 1-5. c = ^jmo x lo" '', continued WEIGHT/ 1,1)01) LENGTH FISH/ WEIGHT EENGIH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 49.000 5.1925 20.408 22.22(;0 13.189 44.992 49.800 5.2206 20.080 22.588!) 13.2()0 44.2(i9 50.f)00 5.2484 19.763 22.9518 13.331 43.570 51.400 5.2759 19.455 23.3147 13.401 42.891 52.200 5.3032 19.157 23.6775 13.470 42.234 53.000 5.3301 18.868 24.0404 13.538 41. ,597 53.800 5.3568 18.587 24.4033 13.606 40.978 54.600 5.3832 18.315 24.76()1 13.673 40.378 55.400 5.4094 18.051 25.1290 13.740 39.795 56.200 5.4353 17.794 25.4919 13.806 39.228 57.000 5.4610 17.544 25.8548 13.871 38.677 57.800 5.4864 17.301 26.2176 13.935 38.142 58.600 5.5116 17.065 26.5805 13.999 37.621 59.400 5.5366 16.835 26.9434 14.063 37.115 60.200 5.5613 16.611 27.3063 14.126 36.622 61.000 5.5858 16.393 27.(i691 14,188 36.141 61.800 5.6101 16.181 28.0320 14,2,50 35.673 62.600 5.6342 15.974 28.3949 14.311 35.218 63.400 5.6581 15.773 28.7578 14.372 34.773 64.200 5.6818 15.576 29.1206 14.432 34.340 65.000 5.7053 15.385 29.4835 14.492 33.917 65.800 5.7287 15.198 29.8464 14.551 33.505 66.600 5.7518 15.015 30.2092 14.610 33.102 67.400 5.7747 14.837 30.5721 14.668 32.709 68.200 5.7975 14.663 30.9350 14.726 32.326 69.000 5.8201 14.493 31.2979 14.783 31.951 69.800 5.8425 14.327 31.6()07 14.840 31.585 70.600 5.8647 14.164 32.0236 14.896 31.227 71.400 5.8868 14.006 32.3865 14.952 30.877 72.200 5.9087 13.850 32.7494 15.008 30.535 73.000 5.9304 13.699 33.1122 15.063 30.200 73.800 5.9520 13.5,50 33.4751 15.118 29.873 74.600 5.9734 13.405 33.8380 15.173 29.553 75.400 5.9947 13.263 34.2009 15.227 29.239 76.200 6.0158 13.123 34.-5637 15.280 28.932 77.000 6.0368 12.987 34.9266 15.334 28.(i31 77.800 6.0576 12.853 35.2895 15.386 28.337 78.600 6.0783 12.723 35.6523 15.439 28.049 79.400 6.0989 12.594 36.0152 15.491 27.766 80.200 6.1193 12.469 36.3781 15.543 27.489 81.000 6.1396 12.346 36.7410 15.595 27.217 81.800 6.1597 12.225 37.1038 15.646 26.951 82.600 6.1797 12.107 37.4667 15.697 26.690 83.400 6.1996 1 1 .990 37.8296 15.747 26.434 84.200 6.2194 11.876 38.1925 15.797 26.183 85.000 6.2390 11.765 38.5553 15.847 25.937 LENGTH-WEIGHT TABLES 445 Table 1-5. C = S.-SOO V 10 ' , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 85.800 6.2585 11.6.55 38.9182 15.897 25.695 8f).fi00 6.2779 11.547 39.2811 15.946 25.457 87.400 6.2972 11.442 39.6440 15.995 25.224 88.200 6.3164 11.338 40.0068 16.044 24.996 89.000 6.3354 1 1 .236 40.3697 16.092 24.771 89.800 6.3543 11.136 40.7326 16.140 24.5.50 90.600 6.3731 11.038 41.09,55 16.188 24.334 91.400 6.3918 10.941 41.4583 16.235 24.121 92.200 6.4104 10.846 41.8212 16.283 23.911 93.000 6.4289 10.7.53 42.1841 16.329 23.706 93.800 6.4473 10.661 42.5470 16.376 23. .503 94.600 6.4656 10.571 42.9098 16.423 23.305 95.400 6.4838 10.482 43.2727 16.469 23.109 96.200 6.,5018 10.395 43.6356 16.515 22.917 97.000 6.5198 10.309 43.9984 16.,560 22.728 97.800 6.5377 10.225 44.3613 16.606 22.542 98.600 6.5555 10.142 44.7242 16.651 22.3,59 99.400 6.5731 10.060 45.0871 16.697 22.179 102.000 6.6299 9.804 46.2664 16.840 21.614 110.000 6.7989 9.091 49.8951 17.269 20.042 118.000 6.9599 8.475 53.5238 17.678 18.683 126.000 7.1138 7.937 57.1526 18.069 17.497 134.000 7.2613 7.463 60.7813 18.444 16.452 142.000 7.4030 7.042 64.4100 18.804 15.525 1.50.000 7.5395 6.667 68.0388 19.150 14.697 158.000 7.6712 6.329 71.6675 19.485 13.953 166.000 7.7985 6.024 75.2962 19.808 13.281 174.000 7.9219 5.747 78.92,50 20.122 12.670 182.000 8.0415 5.495 82.5537 20.425 12.113 190.000 8.1576 5.263 86.1825 20.720 11.603 198.000 8.2705 5.051 89.8112 21.007 11.134 206.000 8.3804 4.8.54 93.4399 21.286 10.702 214.000 8.4875 4.673 97.0687 21.558 10.302 222.000 8.5920 4. .505 100.6974 21.824 9.931 230.000 8.6940 4.348 104.3261 22.083 9.,585 238.000 8.7937 4.202 107.9549 22.336 9.263 246.000 8.8911 4.065 111.5836 22.,583 8.962 254.000 8.9865 3.937 115.2123 22.826 8.680 262.000 9.0798 3.817 118.8411 23.063 8.415 270.000 9.1713 3.704 122.4698 23.295 8.165 278.000 9.2610 3.597 126.0986 23.523 7.930 286.000 9.3490 3.497 129.7273 23.746 7.708 294.000 9.4354 3.401 133.3.560 23.966 7.499 302.000 9.5202 3.311 136.9848 24.181 7.300 310.000 9.6035 3.226 140.6135 24.393 7.112 318.000 9.6854 3.145 144.2422 24.601 6.933 44(5 FISH HATCHERY MANAGEMENT Table 1-5. c=3,.';ooxio % continued WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 326.000 9.7fi(iO 3.067 147.8710 24.80(i (),763 3;«.ooo 9,84,'')2 2.994 151.4997 25.007 6.601 342.000 9.9232 2.924 155.1284 25.205 6.44() 350.000 10.0000 2.857 158.7572 25.400 6.299 LENGTH-WKICH I [ABLE.S 447 Table 1-6. LENGTH-WEIGH I RELAIIONSHH'S EUR EISH \VH H C = 4,()()() ■ 10-^ WEIGHT/ 1,000 LENGTH FISH WEIGHI LE.\GTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.400 l.OOUO 2500.001 0.1814 2.540 5511.551 0.404 1.0033 2475.249 0.1833 2.548 5456.980 0.408 1.0066 2450.982 0. 1 85 1 2.557 5403.484 0.412 1.0099 2427.187 0.1869 2..565 5351.023 0.416 1.0132 2403.849 0.1887 2.573 5299.570 0.420 1.0164 2380.955 0.1905 2.582 5249.098 0.424 1.0196 2358.494 0.1923 2.590 5199.582 0.428 1.0228 2336.452 0.1941 2. ,598 5150.988 0.432 1.0260 2314.818 0.1960 2.606 5103.293 0.436 1.0291 2293.582 0.1978 2.614 5056.473 0.440 1.0323 2272.731 0.1996 2.622 .5010..508 0.444 1 .0354 2252.256 0.2014 2.630 4965.367 0.448 1.0385 2232.147 0.2032 2.638 4921.035 0.452 1.0416 2212.394 0.2050 2.646 4877.484 0.456 1.0446 2192.987 0.2068 2.653 4834.703 0.460 1.0477 2173.918 0.2087 2.661 4792.660 0.464 1.0507 2155.177 0.2105 2.669 4751.344 0.468 1.0537 2136.757 0.2123 2.676 4710.734 0.472 1.0567 2118.649 0.2141 2.684 4670.816 0.476 1 .0597 2100.846 0.21.59 2.692 4631.566 0.480 1.0627 2083.339 0.2177 2.699 4592.969 0.484 1 .0656 2066.121 0.2195 2.707 4555.012 0.488 1 .0685 2049.186 0.2214 2.714 4517.676 0.492 1.0714 2032.526 0.2232 2.721 4480.945 0.496 1.0743 2016.135 0.22,50 2.729 4444.809 0.500 1.0772 2000.000 0.2268 2.736 4409.238 0.508 1.0829 1968.504 0.2304 2.751 4339.801 0.516 1.0886 1937.985 0.2341 2.765 4272.520 0.524 1.0942 1908.398 0.2377 2.779 4207.289 0.532 1.0997 1879.701 0.2413 2.793 4144.023 0.540 1.1052 1851.854 0.2449 2.807 4082.633 0.548 1.1106 1824.819 0.2486 2.821 4023.033 0.556 1.1160 1798.563 0.2522 2.835 3965.149 0.564 1.1213 1773.052 0.2558 2.848 3908.906 0.572 1.1266 1748.254 0.2595 2.862 3854.237 0.580 1.1319 1724.141 0.2631 2.875 3801.075 0.588 1.1370 1700.683 0.2667 2.888 3749.361 0.596 1.1422 1677.856 0.2703 2.901 3699.034 0.604 1.1473 1655.633 0.2740 2.914 36.50.041 0.612 1.1523 1633.991 0.2776 2.927 3602.328 0.620 1.1573 1612.907 0.2812 2.940 3555.847 0.628 1.1622 1592.361 0.284i) 2.952 3510.5.50 0.636 1.1672 1572.331 0.2885 2.965 3466.393 0.644 1.1720 1552.799 0.2921 2.977 3423.333 0.652 1.176!) 1533.747 0.2957 2.989 3381.329 0.660 1.1817 1515.156 0.29!)4 3.001 3340.344 448 FISH HATCHERY MANAGEMENT Table 1-6. C= 4,000 X 10 ' , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.668 1.1864 1497.011 0.3030 3.014 3300.340 0.676 1.1911 1479.295 0.3066 3.025 3261.283 0.684 1.19.58 1461.993 0.3103 3.037 3223.139 0.692 1.2005 1445.092 0.3139 3.049 3185.878 0.700 1.2051 1428.577 0.3175 3.061 3149.469 0.708 1 .2096 1412.435 0.3211 3.072 3113.882 0.716 1.2142 1396.653 0.3248 3.084 3079.090 0.724 1.2187 1381.221 0.3284 3.095 3045.067 0.732 1.2232 1366.126 0.3320 3.107 3011.788 0.740 1.2276 1351.357 0.3357 3.118 2979.228 0.748 1.2320 1336.904 0.3393 3.129 2947.365 0.756 1.2364 1322.757 0.3429 3.140 2916.177 0.764 1.2407 1308.906 0.3465 3.151 2885.641 0.772 1.24.50 1295.343 0.3502 3.162 2855.738 0.780 1.2493 1282.057 0.3538 3.173 2826.449 0.788 1.2.536 1269.042 0.3574 3.184 2797.754 0.796 1.2578 1256.287 0.3611 3.195 2769.636 0.804 1.2620 1243.787 0.3647 3.206 2742.078 0.812 1.2662 1231.533 0.3683 3.216 2715.063 0.820 1.2703 1219.518 0.3719 3.227 2688.574 0.828 1.2744 1207.736 0.3756 3.237 2662.-598 0.836 1.2785 1196.178 0.3792 3.247 2637.119 0.844 1.2826 1184.840 0.3828 3.258 2612.123 0.852 1.2866 1173.715 0.3865 3.268 2587.596 0.860 1.2907 1162.797 0.3901 3.278 2563.525 0.868 1.2947 1152.080 0.3937 3.288 2539.898 0.876 1.2986 1141.559 0.3973 3.298 2516.703 0.884 1.3026 1131.228 0.4010 3.308 2493.928 0.892 1.3065 1121.083 0.4046 3.318 2471.561 0.900 1.3104 1111.117 0.4082 3.328 2449.592 0.908 1.3142 1101.328 0.4119 3.338 2428.009 0.916 1.3181 1091.709 0.4155 3.348 2406.804 0.924 1.3219 1082.257 0.4191 3.358 2385.966 0.932 1.3257 1072.968 0.4227 3.367 2365.486 0.940 1.3295 1063.836 0.4264 3.377 2345.354 0.948 1.3333 1054.8.59 0.4300 3.386 2325.563 0.956 1.3370 1046.031 0.4336 3.396 2306.102 0.964 1.3407 1037.351 0.4373 3.405 2286.964 0.972 1.3444 1028.813 0.4409 3.415 2268.142 0.980 1.3481 1020.415 0.4445 3.424 2249.626 0.988 1.3518 1012.152 0.4481 3.433 2231.411 0.996 1.3554 1004.022 0.4518 3.443 2213.488 1.040 1.3751 961.539 0.4717 3.493 2119.829 1.120 1.4095 892.8.59 0.5080 3.580 1968.416 1.200 1.4422 833.337 0.5443 3.663 1837.191 1.280 1.4736 781.254 0.5806 3.743 1722.368 LENG IH-WEIGHT TABLES 449 Table 1-6. C = 4,000 X 10 ' ', CONTINUED WEIGHT/ 1, ()()() LENGTH FISH/ WEIGHT LENGTH FISH, FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM l.SfiO 1.5037 735.299 0.6169 3.819 1621.054 1.440 1.5326 694.449 0.6532 3.893 1530.998 1.520 1.5605 657.900 0.6895 3.964 1450.420 1.600 1.5874 625,006 0.7257 4.032 1377.900 1.680 1.6134 595.244 0.7620 4.098 1312.287 1.760 1.6386 568.188 0.7983 4.162 1252.638 1.840 1.6631 543.484 0.8346 4.224 1198.177 1.920 1.6869 520.839 0.8709 4.285 1148.253 2.000 1.7100 500.006 0.9072 4.343 1102.323 2.080 1.7325 480.775 0.9435 4.400 1059.927 2.160 1.7544 462.969 0.9797 4.456 1020.671 2.240 1.7758 446.435 1.0160 4.511 984.219 2.320 1.7967 431.041 1.0523 4.564 950.281 2.400 1.8171 416.673 1.0886 4.615 918.605 2.480 1.8371 403.232 1.1249 4.666 888.973 2.560 1.8566 390.631 1.1612 4.716 861.193 2.640 1.8758 378.794 1.1975 4.764 835.096 2.720 1.8945 367.653 1.2338 4.812 810.535 2.800 1.9129 357.148 1.2700 4.859 787.377 2.880 1.9310 347.228 1.3063 4.905 765.505 2.960 1.9487 337.843 1.3426 4.950 744.816 3.040 1.9661 328.953 1.3789 4.994 725.216 3.120 1.9832 320.518 1.4152 5.037 706.621 3.200 2.0000 312.505 1.4515 5.080 688.955 3.280 2.0165 304.883 1.4878 5.122 672.152 3.360 2.0328 297.624 1.5240 5.163 656.148 3.440 2.0488 290.703 1.5603 5.204 640.889 3.520 2.0645 284.096 1.5966 5.244 626.323 3.600 2.0801 277.783 1.6329 5.283 612.405 3.680 2.0954 271.744 1.6692 5.322 599.092 3.760 2.1104 265.962 1.7055 5.361 586.346 3.840 2.1253 260.421 1.7418 5.398 574.130 3.920 2.1400 255.107 1.7780 5.436 562.413 4.000 2.1544 250.005 1.8143 5.472 551.165 4.080 2.1687 245.103 1.8506 5.508 540.358 4.160 2.1828 240.389 1.8869 5.544 .529.967 4.240 2.1967 235.854 1.9232 5.580 519.967 4.320 2.2104 231.486 1.9595 5.614 510.338 4.400 2.2240 227.277 1.9958 5.649 .501.060 4.480 2.2374 223.219 2.0321 5.683 492.112 4.560 2.2506 219.302 2.0683 5.717 483.479 4.640 2.2637 215.521 2.1046 5.750 475.143 4.720 2.2766 211.869 2.1409 5.783 467.090 4.800 2.2894 208.337 2.1772 5.815 4,59.305 4.880 2.3021 204.922 2.2135 5.847 451.775 4.960 2.3146 201.617 2.2498 5.879 444.489 450 FISH H.-XTCHERY MANACJEMKNT Table 1-6. C = 4,000 X 10 ' , CONTINUED WKIGH17 1,0(10 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 5.200 2.3513 192.308 2.3587 5.972 423.i)65 5.600 2.4101 178.572 2.5401 6.122 393.(i82 (i.OOO 2.46()2 166.667 2.7215 6.264 367.437 6.400 2.5198 156.2,50 2.9030 6.400 344.472 6.800 2.5713 147.059 3.0844 6.531 324.209 7.200 2.6207 138.889 3.2()59 6.657 306.1!)8 7.600 2.(i684 131.579 3.4473 6.778 290.082 8. ()()() 2.7144 125.000 3.6287 6.895 275.578 8.400 2.7589 119.048 3.8102 7.008 262.455 8.800 2.8020 113.637 3.9916 7.117 250.526 9.200 2.8439 108.69(i 4.1730 7.223 239.633 9.()00 2.8845 104.1(i7 4.3545 7.327 22!).(i49 10. 000 2.!)240 lOO.OOO 4.53,59 7.427 220.463 10.400 2.9625 96. 1 54 4.7173 7.525 211.983 10.800 3.0000 92. ,593 4.8988 7.620 204.132 11.200 3.0366 89.286 5.0802 7.713 196.842 ll.()00 3.0723 86.207 5.2616 7.804 190.054 12.000 3.1072 83.334 5.4431 7.892 183.719 12.400 3.1414 80.645 5.()245 7.979 177.793 12.800 3.1748 78.125 5.80()0 8.064 172.237 13.200 3.2075 75.758 5.9874 8.147 l(i7.017 13.()00 3.2396 73.530 6.1688 8.229 162.105 14.000 3.2711 71.429 f).35()3 8.308 157.473 14.400 3.3019 69.445 6.5317 8.387 153.099 14.800 3.3322 67. ,568 6.7131 8.464 148.961 15.200 3.3620 65.790 6.8946 8.539 145.041 15.(iO() 3.3912 64.103 7.0760 8.614 141.322 16.000 3.4199 62.500 7.2574 8.687 137.789 16.400 3.4482 60.976 7.4389 8.758 134.428 16.800 3.4760 ,59.524 7.6203 8.829 131.227 17.200 3.,5034 58.140 7.8018 8.899 128.176 17. ()()() 3.5303 56.818 7.9832 8.967 125.263 18.000 3.5569 55.556 8.1646 9.035 122.479 18.400 3.5830 54.348 8.3461 9.101 119.816 18.800 3.6088 53.192 8.5275 9.166 117.2(i7 1!».200 3.6342 52.083 8.70i)0 9.231 114.824 19.1)00 3.()593 51.020 8.8904 9.295 112.481 20.000 3.6840 50.000 9.0718 9.357 110.231 20.400 3,7084 49.020 9.2533 9.419 108.070 20.800 3.7325 48.077 9.4347 9.481 105.i)91 21.200 3.7563 47.170 9.6161 9.541 103.992 21.600 3.7798 3.8029 46.296 45.455 9. 797(1 9.601 102.066 .22.000 (^9.9790> . OTHUD 22.400 3.8259 44.643 10.1604 9.718 98.4'21 22.800 3.8485 43.860 10.3419 9.775 9(i.<)94 23.200 3.8709 43.103 10.5233 9.832 95.027 LENGTH-WEIGH r TABLES 451 T.ABLK 1-6. C = 4,000 > 10 ' ', CONTINUED WEIGHT/ 1 ,000 LENGTH FISH/ WEIGHT LENGTH FISH FISH ILB) (INCHES) POUND (GRAMS! I cm; KILOGR.-KM 23.600 3.8930 42.373 10.7048 9.888 93.416 24.000 3.9149 41.667 10.8862 9.i)44 91.859 24.400 3.9365 40,984 11.0676 9.999 90.353 24.800 3.9579 40,323 11.2491 10.053 88.896 25.400 3.9896 39,370 11.5213 10.133 86.796 26.200 4.0310 38,168 11.8841 10.239 84.146 27.000 4,0716 37.037 12.2470 10.342 81.652 27.800 4,1115 35,971 12.6099 10.443 79.303 28.600 4,1505 34,965 12.9728 10.542 77.084 29.400 4.1889 34.014 13.3356 10.640 74.987 30,200 4.2265 33.112 13.6985 10.735 73.000 31.000 4.2635 32.258 14.0614 10.829 71.117 31.800 4.2999 31,446 14.4243 10.922 69.327 32.600 4.3356 30.675 14.7871 11.013 67.626 33.400 4,3708 29.940 15.1500 11.102 66.006 34.200 4,4054 29.240 15.5129 11.190 64.462 35.000 4.4395 28.571 15.8758 11.276 62.989 35.800 4.4731 27.933 16.2386 11.362 61.581 36.600 4.5062 27.322 16.6015 11.446 60.235 37.400 4.5388 26.738 16.9644 11.528 58.947 38.200 4.5709 26.178 17.3272 11.610 57.712 39.000 4.6026 25.641 17.6901 11.691 56.529 39.800 4.6338 25.126 18.0530 11.770 55.392 40.600 4.6()47 24.630 18.4159 11.848 54.301 41,400 4.6951 24.155 18.7787 11.926 53.252 42.200 4.7252 23.697 19.1416 12.002 52.242 43.000 4.7548 23.256 19.5045 12.077 51.270 43.800 4.7842 22.831 19.8674 12.152 50.334 44.600 4.8131 22,421 20.2302 12.225 49.431 45,400 4.8417 22.026 20.5931 12.298 48.560 46,200 4.8700 21.645 20.9560 12.370 47.719 47,000 4.8979 21.277 21.3188 12.441 46.907 47.800 4.9256 20.920 21.6817 12.511 46.122 48.600 4.9529 20.576 22.0446 12.580 45.362 49.400 4.9799 20.243 22.4075 12.649 44.628 50.200 5.0067 19,920 22.7703 12.717 43.917 51.000 5.0331 19,fi()8 23.1332 12.784 43.228 51.800 5.0593 19,305 23.4961 12.851 4 2., 560 52.600 5.0852 19.011 23.8590 12.916 41.913 53.400 5.1109 18.727 24.2218 12.982 41.285 54.200 5,1363 18.450 24.5847 13.046 40.676 55.000 5,1614 18.182 24.9476 13.110 40.084 55.800 5,1863 17.921 25.3105 13.173 39.509 56.600 5.2110 17.668 25.6733 13.236 38.951 57.400 5.2354 17.422 26.0362 13.298 38.408 58.200 5.2596 17.182 26.3991 13.359 37.880 452 FISH HATCHERY MANAGEMENT Table 1-6. C = 4,000 X 10 % CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 59.000 5.2836 16.949 26.7619 13.420 37.366 59.800 5.3074 16.722 27.1248 13.481 36.867 60.(iO0 5.3309 16.502 27.4877 13.541 36.380 61.400 5.3543 16.287 27.8506 13.600 35.906 62.200 5.3775 16.077 28.2134 13.659 35.444 63.000 5.4004 15.873 28.5763 13.717 34.994 63.800 5.4232 15.674 28.9392 13.775 34.555 64.600 5.4457 15.480 29.3021 13.832 34.127 65.400 5.4681 15.291 29.6649 13.889 33.710 66.200 5.4903 15.106 30.0278 13.945 33.302 67.000 5.5124 14.925 30.3907 14.001 32.905 67.800 5.5324 14.749 30.7536 14.057 32.516 68.600 5.5559 14.577 31.1164 14.112 32.137 69.400 5.5774 14.409 31.4793 14.167 31.767 70.200 5.5988 14.245 31.8422 14.221 31.405 71.000 5.6200 14.084 32.2050 14.275 31.051 71.800 5.6410 13.928 32.5679 14.328 30.705 72.600 5.6619 13.774 32.9308 14.381 30.367 73.400 5.6826 13.624 33.2937 14.434 30.036 74.200 5.7031 13.477 33.6566 14.486 29.712 75.000 5.7236 13.333 34.0194 14.538 29.395 75.800 5.7438 13.193 34.3823 14.589 29.085 76.600 5.7640 13.055 34.7452 14.641 28.781 77.400 5.7840 12.920 35.1080 14.691 28.483 78.200 5.8038 12.788 35.4709 14.742 28.192 79.000 5.8236 12.658 35.8338 14.792 27.907 79.800 5.8432 12.531 36.1967 14.842 27.627 80.600 5.8626 12.407 36.5595 14.891 27.353 81.400 5.8820 12.285 36.9224 14.940 27.084 82.200 5.9012 12.165 37.2853 14.989 26.820 83.000 5.9202 12.048 37.6481 15.037 26.562 83.800 5.9392 11.933 38.0110 15.086 26.308 84.600 5.9580 11.820 38.3739 15.133 26.059 85.400 5.9768 11.710 38.7368 15.181 25.815 86.200 5.9954 11.601 39.0997 15.228 25.576 87.000 6.0139 11.494 39.4625 15.275 25.340 87.800 6.0322 11.390 39.8254 15.322 25.110 88.600 6.0505 11.287 40.1883 15.368 24.883 89.400 6.0687 11.186 40.5511 15.414 24.660 90.200 6.0867 11.086 40.9140 15.460 24.441 91.000 6.1046 10.989 41.2769 15.506 24.227 91.800 6.1225 10.893 41.6398 15.551 24.015 92.600 6.1402 10.799 42.0026 15.596 23.808 93.400 6.1578 10.707 42.3655 15.641 23.fi04 94.200 6.1754 10.616 42.7284 15.685 23.404 95.000 6.1928 10.526 43.0912 15.730 23.206 LENGTH-WEIGHT TABLES 453 Table 1-6. C = 4,(){)() ^ 10 ^, CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GR.AMSI (CM) KILOGRAM 95.800 6.2101 10.438 43.4.541 15.774 23.013 96.600 6.2274 10.352 43.8170 15.818 22.822 97.400 6.2445 10.267 44.1799 15,861 22.635 98.200 6.2616 10.183 44.5427 15.904 22.450 99.000 6.2785 10.101 44.9056 15.947 22.269 99.800 6.2954 10.020 45.2685 15.990 22.090 106.000 6.4232 9.434 48.0807 16.315 20.798 114.000 6.5808 8.772 51.7095 16.715 19.339 122.000 6.7313 8.197 55.3382 17.098 18.071 130.000 6.8753 7.692 58.9669 17.463 16.9.59 138.000 7.0136 7.246 62..5957 17.814 15.976 146.000 7.1466 6.849 66.2244 18.152 15.100 154.000 7.2748 6.494 69.8531 18.478 14.316 162.000 7.3986 6.173 73.4819 18.793 13.609 170.000 . 7.5185 5.882 77.1106 19.097 12.968 178.000 7.6346 5.618 80.7394 19.392 12.386 186.000 7.7473 5.376 84.3681 19.678 11.853 194.000 7.8568 5.155 87.9968 19.9.56 11.364 202.000 7.9634 4.950 91.6256 20.227 10.914 210.000 8.0671 4.762 95.2543 20.491 10.498 218.000 8.1683 4.587 98.8830 20.747 10.113 226.000 8.2670 4.425 102.5118 20.998 9.7.55 234.000 8.3634 4.274 106.1405 21.243 9.421 242.000 8.4577 4.132 109.7692 21.483 9.110 250.000 8.5499 4.000 113.3980 21.717 8.818 258.000 8.6401 3.876 117.0267 21.946 8.545 266.000 8.7285 3.759 120.6.555 22.170 8.288 274.000 8.8152 3.650 124.2842 22.390 8.046 282.000 8.9001 3.546 127.9129 22.606 7.818 290.000 8.9835 3.448 131.5417 22.818 7.602 298.000 9.0654 3.356 135.1704 23.026 7.398 306.000 9.1458 3.268 138.7991 23.230 7.205 314.000 9.2248 3.185 142.4279 23.431 7.021 322.000 9.3025 3.106 146.0566 23.628 6.847 330.000 9.3789 3.030 149.6853 23.822 6.681 338.000 9.4541 2.959 153.3141 24.013 6.523 346.000 9.5281 2.890 156.9428 24.201 6.372 354.000 9.6009 2.825 160.5715 24.386 6.228 362.000 9.6727 2.762 164.2003 24.569 6.090 370.000 9.7435 2.703 167.8290 24.748 5.958 378.000 9.8132 2.646 171.4577 24.926 5.832 386.000 9.8819 2.-59 1 175.0865 25.100 5.7 1 1 394.000 9.9497 2.538 178.7152 25.272 5.595 454 FISH HATCHKRY MANAGEMENT Table 1-7. LENGTH-WKIGHI r RELATIONSHIPS FOR FISH WITH C= 4,500 x ur' WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.450 1.0000 2222.224 0.2041 2.540 4899.1.56 0.454 1.0030 2202.645 0.2059 2.548 4855.992 0.458 1 .0059 2183.408 0.2077 2.555 4813.582 0.462 1.0088 2164.504 0.2096 2.562 4771.906 0.466 1.0117 2145.925 0.2114 2.570 4730.945 0.470 1.0146 2127.662 0.2132 2.577 4690.684 0.474 1.0175 2109.707 0.2150 2..584 4651.102 0.478 1 .0203 2092.053 0.2168 2.592 4612.180 0.482 1.0232 2074.692 0.2186 2.,599 4573.906 0.486 1.0260 2057.616 0.2204 2.606 4.536.262 0.490 1.0288 2040.820 0.2223 2.613 4499.230 0.494 1.0316 2024.295 0.2241 2.620 4462.801 0.498 1.0344 2008.036 0.22.59 2.627 4426.9,53 0.504 1.0385 1984,127 0.2286 2.638 4374.246 0.512 1.0440 1953.125 0.2322 2.652 4305.898 0.520 1.0494 1923.078 0.23.59 2.665 4239.6.52 0.528 1.0547 1893.941 0.2395 2.679 4175.418 0.536 1.0600 1865.673 0.2431 2.692 4113.098 0.544 1.0653 1838.237 0.2468 2.706 4052.614 0.552 1.0705 1811.. 596 0.2.504 2.719 3993.881 0.560 1.0756 1785.717 0.2540 2.732 3936.826 0.568 1.0807 1760.566 0.2576 2.745 3881.379 0.576 1 .0858 1736.114 0.2613 2.758 3827.471 0.584 1.0908 1712.332 0.2649 2.771 3775.041 0.592 1 .0957 1689.192 0.2685 2.783 3724.027 0.600 1.1006 1666.670 0.2722 2.796 3674.374 0.608 1.1055 1644.740 0.2758 2.808 3626.028 0.616 1.1103 1623.380 0.2794 2.820 3578.937 0.624 1.1151 1602.568 0.2830 2.832 3533.053 0.632 1.1199 1582.283 0.2867 2.844 3488.332 0.640 1.1246 1562. ,504 0.2903 2.856 3444.728 0.648 1.1292 1.543.214 0.2939 2.868 3402.201 0.656 1.1339 1524.395 0.2976 2.880 3360.711 0.664 1.1385 1506.029 0.3012 2.892 3320.221 0.672 1.1430 1488.100 0.3048 2.903 3280.695 0.680 1.1475 1470.593 0.3084 2.915 3242.099 0.688 1.1520 1453.493 0.3121 2.926 3204.400 0.696 1.1565 1436.787 0.3157 2.937 3167..569 0.704 1.1609 1420.460 0.3193 2.949 3131.574 0.712 1.1653 1404.,500 0.3230 2.960 3096.388 0.720 1.1696 1388.894 0.3266 2.971 3061.984 0.728 1.1739 1373.632 0.3302 2.982 3028.336 0.736 1.1782 1358.701 0.3338 2.993 2995.420 0.744 1.1825 1344.092 0.3375 3.003 2963.211 0.752 1.1867 1329.793 0.3411 3.014 2931.688 0.760 1.1909 1315.795 0.3447 3.025 2900.828 LENGTH-WEIGHT TABLES 455 Table 1-7. C = 4,.-)00 X 10 ■ , CONTINUED WEIGHT, 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 0.768 1.1950 1302.089 0.3484 3.035 2870.612 0.776 1.1992 1288.666 0.3520 3.046 2841.018 0.784 1.2033 1275.516 0.3556 3.056 2812.028 0.792 1.2074 1262.632 0.3592 3.067 2783.624 0.800 1.2114 1 250.006 0.3629 3.077 2755.788 0.808 1.2154 1237.630 0.3665 3.087 2728..503 0.816 1.2194 1225.496 0.3701 3.097 2701.7.53 0.824 1.2234 1213.598 0.3738 3.107 2675.523 0.832 1.2274 1201.929 0.3774 3.117 2649.797 0.840 1.2313 1190.482 0.3810 3.127 2624..561 0.848 1.2352 1179.251 0.3846 3.137 2,599.801 0.856 1.2390 1168.230 0.3883 3.147 2575. .504 0.864 1.2429 1157.414 0.3919 3.157 2551.657 0.872 1.2467 1146.795 0.3955 3.167 2528.248 0.880 1.2505 1136.370 0.3992 3.176 2505.264 0.888 1.2.543 1126.132 0.4028 3.186 2482.694 0.896 1.2.580 1116.078 0.4064 3.195 2460.527 0.904 1.2618 1106.201 0.4100 3.205 2438.753 0.912 1.2655 1096.498 0.4137 3.214 2417.360 0.920 1.2692 1086.963 0.4173 3.224 2396.340 0.928 1.2729 1077. ,593 0.4209 3.233 2375.682 0.936 1.2765 1068.382 0.4246 3.242 23,55.377 0.944 1.2801 1059.328 0.4282 3.252 2335.417 0.952 1.2837 1050.427 0.4318 3.261 2315.791 0.960 1.2873 1041.673 0.4354 3.270 2296.493 0.968 1.2909 1033.064 0.4391 3.279 2277.514 0.976 1.2944 1024.596 0.4427 3.288 2258.846 0.984 1.2980 1016.266 0.4463 3.297 2240.481 0.992 1.3015 1008.071 0.4500 3.306 2222.413 1.000 1.3050 1000.000 0.4536 3.315 2204.620 1.080 1.3389 925.927 0.4899 3.401 2041.318 1.160 1.3711 862.072 0.5262 3.483 1900.541 1.240 1.4020 806.455 0..5625 3.561 1777.928 1.320 1.4315 757.580 0.5987 3.636 1670.177 1.400 1.4598 714.291 0.6350 3.708 1574.740 1.480 1.4871 675.681 0.6713 3.777 1489.620 1.560 1.5135 641.031 0.7076 3.844 1413.230 1.640 1.5389 609.762 0.7439 3.909 1344.293 1.720 1.5635 581.401 0.7802 3.971 1281.769 1.800 1.5874 555.562 0.8165 4.032 1224.802 1.880 1.6106 531.921 0.8527 4.091 1172.684 1.960 1.6331 510.210 0.8890 4.148 1124.820 2.040 1.65.50 490.202 0.9253 4.204 1080.709 2.120 1.6764 471.704 0.9616 4.258 1039.928 2.200 1.6972 454.552 0.9979 4.311 1002.113 2.280 1.7175 438.603 1.0342 4.363 966.952 456 FISH HATCHF.RY MANAGEMENT Table 1-7. C= 4,.TO()x 10 \ CONTINUED WEIGHT/ 1 ,()()() LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 2.360 1.7374 423.735 1.0705 4.413 934.174 2.440 1.7568 409.842 1.1067 4.462 903.546 2.520 1.7758 396.831 1.1430 4.511 874.862 2.600 1.7944 384.621 1.1793 4.558 847.944 2.680 1.8126 373.140 1.2156 4.604 822.632 2.760 1 .8305 362.324 1.2519 4.649 798.788 2.840 1.8480 352.118 1.2882 4.694 776.287 2.920 1.8652 342.471 1.3245 4.738 755.019 3.000 1.8821 333.339 1.3608 4.780 734.885 3.080 1.8986 324.681 1.3970 4.823 715.798 3.160 1.9149 316.461 1.4333 4.864 697.676 3.240 1.9310 308.647 1.4696 4.095 680.450 3.320 1.9467 301.210 1.5059 4.945 664.053 3.400 1.9622 294.123 1.5422 4.984 648.429 3.480 1.9775 287.361 1.5785 5.023 633.522 3.560 1.9926 280.904 1.6148 5.061 619.286 3.640 2.0074 274.730 1.6510 5.099 605.676 3.720 2.0220 268.822 1.6873 5.136 592.6,50 3.800 2.0364 263.163 1.7236 5.172 580.174 3.880 2.0506 257.737 1.7599 5.208 ,568.211 3.960 2.0645 252.530 1.7962 5.244 -556.732 4.040 2.0784 247.529 1.8325 5.279 545.708 4.120 2.0920 242.723 1.8688 5.314 535.112 4.200 2.1054 238.100 1.90,50 5.348 524.919 4.280 2.1187 233.649 1.9413 5.382 515.108 4.360 2.1318 229.362 1.9776 5.415 ,505.656 4.440 2.1448 225.230 2.0139 5.448 496.545 4.520 2.1576 221.243 2.0,502 5.480 487.757 4.600 2.1703 217.396 2.0865 5.512 479.274 4.680 2.1828 213.679 2.1228 5.544 471.082 4.760 2.1951 210.088 2.1591 5.576 463.164 4.840 2.2074 206.616 2.1953 5.607 455. ,509 4.920 2.2195 203.256 2.2316 5.637 448.102 5.000 2.2314 200.000 2.2680 5.668 440.924 5.400 2.2894 185.185 2.4494 5.815 408.263 5.800 2.3446 172.414 2.6308 5.955 380.107 6.200 2.3973 161.290 2.8123 6.089 3.55.584 6.600 2.4478 151.515 2.9937 6.217 334.034 7.000 2.4963 142.857 3.1751 6.341 314.946 7.400 2.5430 135.135 3.3566 6.4,59 297.922 7.800 2.5880 128.205 3.5380 6.573 282.644 8.200 2.6315 121.951 3.7194 6.684 268.856 8.()00 2.6736 116.279 3.9009 6.791 256.352 9.000 2.7144 111.111 4.0823 6.895 244.958 9.400 2.7540 106.383 4.2638 6.995 234.535 9.800 2.7926 102.041 4.4452 7.093 224.962 LENGTH-WEIGHT TABLES 457 Table 1-7. C= 4,.i00> 10 ■ , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB' (INCHES) POUND 'GRAMSl (CM) KILOGRAM 10.200 2.8301 98.039 4.6266 7.188 216.140 10.600 2.8666 94.340 4.8081 7.281 207.984 1 1 .000 2.9022 90.909 4.9895 7.372 200.421 11.400 2.9370 87.720 5.1709 7.460 193.388 11.800 2.9709 84.746 5.3524 7.546 186.833 12.200 3.0041 81.967 ,5.5338 7.630 180.707 12.600 3.0366 79.365 5.7152 7.713 174.970 13.000 3.0684 76.923 5.8967 7.794 169.587 13.400 3.0995 74.627 6.0781 7.873 164.524 13.800 3.1301 72.464 6.2595 7.950 1.59.756 14.200 3.1600 70.423 6.4410 8.026 155.255 14.600 3.1894 68.493 6.6224 8.101 151.002 15.000 3.2183 66.667 6.8039 8.174 146.975 15.400 3.2467 64.935 6.9853 8.246 143.158 15.800 3.2745 63.291 7.1667 8.317 139.533 16.200 3.3019 61.728 7.3482 8.387 136.088 16.600 3.3289 60.241 7.5296 8.455 132.808 17.000 3.3554 58.824 7.7111 8.523 129.684 17.400 3.3815 57.471 7.8925 8.589 126.702 17.800 3.4072 56.180 8.0739 8.654 123.855 18.200 3.4326 54.945 8.2554 8.719 121.133 18.600 3.4575 53.764 8.4368 8.782 118.528 19.000 3.4821 52.632 8.6182 8.845 116.033 19.400 3.5064 51.546 8.7997 8.906 113.640 19.800 3.5303 50.505 8.9811 8.967 111.344 20.200 3.5540 49.505 9.1625 9.027 109.140 20.600 3.5773 48.544 9.3440 9.086 107.021 21.000 3.6003 47.619 9.5254 9.145 104.982 21.400 3.6230 46.729 9.7069 9.202 103.020 21.800 3.6454 45.872 9.8883 9.259 101.129 22.200 3.6676 45.045 10.0697 9.316 99.307 22.600 3.6895 44.248 10.2512 9.371 97..5.50 23.000 3.7111 43.478 10.4326 9.426 95.853 23.400 3.7325 42.735 10.6140 9.481 94.215 23.800 3.7537 41.017 10.79.55 9..534 92.631 24.200 3.7746 41.322 10.9769 9..587 91.100 24.600 3.7953 40.650 11.1583 9.640 89.619 25.000 3.8157 40.000 11.3398 9.692 88.185 25.800 3.8560 38.760 11.7027 9.794 85.4.50 26.600 3.8954 37.594 12.0656 9.894 82.880 27.400 3.9341 36.496 12.4285 9.993 80.460 28.200 3.9720 35.461 12.7913 10.089 78.178 29.000 4.0092 34.483 13.1.542 10.183 76.021 29.800 4.0458 33.557 13.5171 10.276 73.980 30.600 4.0817 32.680 13.8800 10.367 72.046 31.400 4.1169 31.847 14.2428 10.457 70.211 458 FISH HATCHERY MANAGEMENT Table 1-7. C = 4,500 X 1 0 , CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 32.200 4.1516 3 1 .056 14.6057 10.545 68.466 33.000 4.1857 30.303 14.9686 10.632 66.807 33.800 4.2192 29.586 15.3314 10.717 65.225 34.600 4.2523 28.902 15.6943 10.801 63.717 35.400 4.2848 28.249 16.0572 10.883 62.277 36.200 4.3168 27.624 16.4201 10.965 60.901 37.000 4.3484 27.027 16.7829 11.045 ,59.,584 37.800 4.3795 26.455 17.1458 11.124 58.323 38.600 4.4102 25.907 17. .5087 1 1 .202 57.114 39.400 4.4405 25.381 17.8716 11.279 55.9.55 40.200 4.4703 24.876 18.2344 11.3,55 54.841 41.000 4.4998 24.390 18..5973 11.429 .53.771 41.800 4.5289 23.923 18.9602 11. .503 52.742 42.600 4.5576 23.474 19.3230 11.576 51.752 43.400 4.5859 23.041 19.6859 11.648 ,50.798 44.200 4.6139 22.624 20.0488 11.719 49.878 45.000 4.6416 22.222 20.4117 11.790 48.991 45.800 4.6689 21.834 20.7745 11.8.59 48.136 46.600 4.6960 21.4,59 21.1374 11.928 47.309 47.400 4.7227 21.097 21. ,5003 11.996 46.511 48.200 4.7491 20.747 21.8632 12.063 45.739 49.000 4.77,52 20.408 22.2260 12.129 44.992 49.800 4.8011 20.080 22.5889 12.195 44.269 50.600 4.8267 19.763 22.9518 12.260 43.570 51.400 4.8520 19.455 23.3147 12.324 42.891 52.200 4.8770 19.157 23.6775 12.388 42.234 53.000 4.9018 18.868 24.0404 12.451 41.. 597 53.800 4.9263 18.587 24.4033 12.513 40.978 54.600 4.9506 18.315 24.7661 12.575 40.378 55.400 4.9747 18.051 25.1290 12.636 39.795 56.200 4.9985 17.794 25.4919 12.696 39.228 57.000 5.0221 17. ,544 25.8548 12.756 38.677 57.800 5.04,55 17.301 26.2176 12.816 38.142 58.600 5.0687 17.065 26.5805 12.874 37.621 59.400 5.0916 16.835 26.9434 12.933 37.115 60.200 5.1144 16.611 27.3063 12.991 36.622 61.000 5.1370 16.393 27.6691 13.048 36.141 61.800 5.1593 16.181 28.0320 13.105 35.673 62.600 5.1815 15.974 28.3949 13.161 35.218 63.400 5.2035 15.773 28.7578 13.217 34.773 64.200 5.2253 15.576 29.1206 13.272 34.340 65.000 5.2469 15.385 29.4835 13.327 33.917 65.800 5.2683 15.198 29.8464 13.381 33. .505 66.600 5.2896 15.015 30.2092 13.436 33.102 67.400 5.3107 14.837 30.5721 13.489 32.709 68.200 5.3316 14.663 30.9350 13.542 32.326 LENGTH-WEIGHT TABLES 459 Table 1-7. c = 4,500 x 10 CONTINUED WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 69.000 69.800 70.600 71.400 72.200 73.000 73.800 74.600 75.400 76.200 77.000 77.800 78.600 79.400 80.200 8L000 8L800 82.600 83.400 84.200 8.5.000 8,1.800 86.600 87.400 88.200 89.000 89.800 90.600 9L400 92.200 93.000 93.800 94.600 9.5.400 96.200 97.000 97.800 98.600 99.400 102.000 110.000 118.000 126.000 134.000 142.000 1.50.000 .5.3524 .5.3730 5.3934 5.4137 5.4339 5.4539 5.4737 5.4934 5.5130 5.5324 5.5517 5.5709 5.5899 5.6088 5.6276 5.6462 5.6647 5.6832 5.7014 5.7196 5.7377 5,75.56 5.7734 5.7912 5.8088 5.8263 5.8437 5.8610 5.8782 5.8953 5.9123 5.9292 5.9460 5.9627 5.9793 5.99.59 6.0123 6.0287 6.0449 6.0972 6.2526 6.4006 6.5421 6.6778 6.8081 6.9337 14.493 14.327 14.164 14.006 13.850 13.699 13.5,50 13.405 13.263 13.123 12.987 12.853 12.723 12..594 12.469 12.346 12.225 12.107 11.990 11.876 11.765 11.655 11.547 11.442 11.338 11.236 11.136 11.038 10.941 10.846 10.753 10.661 10.571 10.482 10.395 10.309 10.225 10.142 10.060 9.804 9.091 8.475 7.937 7.463 7.042 6.667 31.2979 31.6607 32.0236 32.3865 32.7494 33.1122 33.4751 33.8380 34.2009 34.5637 34.9266 35.2895 35.6523 35.0152 36.3781 36.7410 37.1038 37.4667 37.8296 38.1925 38.5553 38.9182 39.2811 39.6440 40.0068 40.3697 40.7326 41.0955 41.4583 41.8212 42.1841 42.5470 42.9098 43.2727 43.6356 43.9984 44.3613 44.7242 45.0871 46.2664 49.8951 53.5238 57.1526 60.7813 64.4100 68.0388 13.595 13.647 13.699 13.751 13.802 13.853 13.903 13.953 14.003 14.052 14.101 14.1.50 14.198 14.246 14.294 14.341 14.388 14.435 14.482 14.528 14.574 14.619 14,665 14.710 14.754 14,799 14.843 14.887 14.931 14.974 15.017 15.0()0 15.103 15.145 15.188 15.230 15.271 15.313 15.354 15.487 15.882 16.258 16.617 16.961 17.293 17.611 31.951 31.585 31.227 30.877 30.535 30.200 29.873 29.553 29.239 28,932 28.631 28,337 28,049 27,766 27,489 27,217 26,951 26,690 26.434 26.183 25.937 25.695 25.457 25.224 24.996 24.771 24.5,50 24.334 24.121 23.911 23.706 23..503 23.305 23.109 22.917 22.728 22.542 22.359 22.179 21.614 20.042 18.683 17.497 16.452 15.525 14.697 460 KISH HATCHERY MANAGEMENT Table 1-7. c- 4,500 x 10 CONTINUED WEIGHT/ 1, ()()() LENGTH FISH/ WEIGHT LENGIH FISH/ FISH (LB) (INCHES) POUND (GRAMS) (CM) KILOGRAM 158. ()()() 7.0547 6.329 71.6675 17.919 13.953 1()().(){)() 7.1719 6.024 75.2962 18.217 13.281 174.000 7.2853 5.747 78.9250 18. ,505 12.()70 1K2.00() 7.3953 5.495 82.5537 18.784 12.113 190.000 7. ,5021 5.263 86.1825 19.055 1 1 .603 198.000 7.6059 5.051 89.8112 19.319 11.134 206.000 7.7070 4.854 93.4399 19.576 10.702 214.000 7.8055 4.673 97.0687 19.826 10.302 222.000 7.9016 4.505 100.6974 20.070 9.931 230.000 7.9954 4.348 104.3261 20.308 9.585 238.000 8.0870 4.202 107.9549 20.541 9.263 24(i.()00 8.1766 4.065 111.0006 20.769 8,962 254.000 8.2643 3.937 115.2123 20.991 8.680 262.000 8.3502 3.817 118.8411 21.209 8.415 270.000 8.4343 3.704 122.4698 21.423 8.165 278.000 8.5168 3.597 126.0986 21.633 7.930 286.000 8.5977 3.497 129.7273 21.838 7.708 294.000 8.6772 3.401 133.3560 22,040 7.499 302.000 8.7552 3.311 136,9848 22.238 7.300 310.000 8.8318 3.226 140.6135 22.433 7.112 318.000 8,9071 3.145 144.2422 22.624 6.933 326.000 8.9812 3.067 147.8710 22.812 6.763 334.000 9.0541 2.994 151.4997 22.997 6.601 342.000 9.1258 2.924 155.1284 23.180 6.446 350.000 9.1964 2.857 158.7572 23.3.59 6.299 358.000 9.2660 2.793 162.3859 23.536 6.1,58 366.000 9.3345 2.732 166.0146 23.710 6.024 374.000 9.4020 2.674 169.6434 23.881 5.895 382.000 9.4685 2.618 173.2721 24.0,50 5.771 390.000 9.5342 2.564 1 76.9008 24.217 5.653 398.000 9.5989 2.513 180.5296 24.381 5.539 406,000 9.6628 2.463 184.1583 24.544 5.430 414.000 9.7259 2.415 187.7871 24.704 5.325 422.000 9,7881 2.370 191.4158 24.862 5.224 430.000 9.8496 2.326 195.0445 25.018 5.127 438.000 9.9103 2.283 198.6733 25.172 5.033 446.000 9.9703 2.242 202.3020 25.324 4.943 LENG TH-WEIGHT TABLES 461 Table 1-8. LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C= .5,000 x ur' WEIGHT/ 1,000 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (lb; iINCHES) POUND (GRAMS) (CM) KILOGRAM 0.500 1 .0000 2000.001 0.2268 2.540 4409.242 0.50fi 1.0040 1976.285 0.2295 2.5.50 4356.953 0.514 1 .0092 1945.526 0.2331 2.563 4289.145 0.522 1.0145 1915.710 0.2368 2.577 4223.410 0.530 1.0196 1886.794 0.2404 2.590 4159.660 0.538 1.0247 1858.738 0.2440 2.603 4097.809 0.546 1.0298 1831.504 0.2477 2.616 4037.770 0.554 1.0348 1805.056 0.2513 2.628 3979.463 0.562 1.0397 1779.362 0.2549 2.641 3922.817 0.570 1.0446 1754.389 0.2585 2.653 3867.760 0.578 1.0495 1730.107 0.2622 2.666 3814.228 0.586 1.0543 1706.488 0.2658 2.678 3762.157 0.594 1.0591 1683.505 0.2694 2.690 3711.489 0.602 1.0638 1661.133 0.2731 2.702 3662.167 0.610 1.0685 1639.348 0.2767 2.714 3614.139 0.618 1.0732 1618.127 0.2803 2.726 3567.355 0.626 1.0778 1597.448 0.2839 2.738 3521.766 0.634 1.0824 1577.291 0.2876 2.749 3477.328 0.642 1.0869 1557.637 0.2912 2.761 3433.997 0.650 1.0914 1538.466 0.2943 2.772 3391.733 0.658 1.0959 1519.761 0.2985 2.783 33.50.496 0.666 1.1003 1501.506 0.3021 2.795 3310.250 0.674 1.1047 1483.684 0.3057 2.806 3270.960 0.682 1.1090 1466.281 0.3093 2.817 3232.592 0.690 1.1133 1449.280 0.3130 2.828 3195.113 0.698 1.1176 1432.670 0.3166 2.839 31.58.493 0.706 1.1219 1416.436 0.3202 2.850 3122.703 0.714 1.1261 1400.565 0.3239 2.860 3087.715 0.722 1.1303 1385.047 0.3275 2.871 3053.502 0.730 1.1344 1369.868 0.3311 2.881 3020.039 0.738 1.1386 1355.019 0.3347 2.892 2987.302 0.746 1.1427 1340.488 0.3384 2.902 2955.267 0.754 1.1467 1326.266 0.3420 2.913 2923.912 0.762 1.1508 1312.342 0.3456 2.923 2893.215 0.770 1.1548 1298.707 0.3493 2.933 2863.156 0.778 1.1588 1285.353 0.3529 2.943 2833.715 0.786 1.1627 1272.271 0.3565 2.953 2804.873 0.794 1.1667 1259.452 0.3602 2.963 2776.613 0.802 1.1706 1246.889 0.3638 2.973 2748.916 0.810 1.1745 1234.574 0.3674 2.983 2721.766 0.818 1.1783 1222.500 0.3710 2.993 2695.148 0.826 1.1821 1210.660 0.3747 3.003 2669.045 0.834 1.1859 1199.047 0.3783 3.012 2643.443 0.842 1.1897 1187.655 0.3819 3.022 2618.327 0.850 1.1935 1176.477 0.3856 3.031 2593.684 0.858 1.1972 1165.507 0.3892 3.041 2569.501 462 FISH HATCHERY MANAGEMENT Table 1-8. C = .5,000 X 10 ', CONTINUED WKKJHIV 1,00(1 LENGTH FISH/ WEIGHT LENGTH FISH/ FISH (LB) (INCHES) PCJUND (GRAMS) (CM) KILOGRAM (),8(i(i 1,2009 11.54.740 0.3928 3.050 2545.764 0,S74 1.2046 1144.171 0.3964 3.060 2522.462 0.882 1.2083 1133.793 0.4001 3.069 2499.583 0.890 1.211!) 1123.602 0.4037 3.078 2477.115 0.898 1.21.5,'-) 1113.,592 0,4073 3.087 2455.047 0.906 1.2191 1103.7,59 0,4110 3.097 2433.369 0.914 1.2227 1094,098 0,4146 3.106 2412,071 0.922 1,2263 1084.60,5 0.4182 3.115 2391,142 0.930 1.2298 107,5,27,5 0,4218 3.124 2370,573 0.938 1.2333 1066.104 0,425,5 3.133 23.50,355 0.946 1.2368 10,57,089 0,4291 3.142 2330,479 0.9.54 1.2403 1048,224 0,4327 3.150 2310.936 0.9(i2 1.2438 1()39„507 0,4364 3.159 2291.719 0.970 1.2472 1030,934 0,4400 3.168 2272.818 0.978 1.2.506 1022, .501 0,4436 3.177 2254.227 0.986 1.2.540 1014.205 0,4472 3.185 2235.937 0.994 1.2.574 10()().()42 0.4509 3.194 2217.941 1.020 1.2683 980.393 0.4627 3.221 2161.393 1,100 1.3006 909.093 0.4990 3.303 2004.204 1.180 1.3314 847.461 0.53,52 3.382 1868.329 1,2()0 1.3608 793.6,5,5 0.5715 3.456 1749.707 1,340 1.3890 746.273 0.6078 3.528 1645.249 1,420 1.4161 704.230 0.6441 3.597 1552. .561 1,.500 1.4422 666.672 0.6804 3.663 1469.7.59 1,.S80 1.4674 632.917 0.7167 3.727 1395.342 1,660 1.4918 602.416 0.7530 3.789 1328.097 1,740 1.. 5 1.54 .574.719 0.7892 3.849 1267.036 1,820 l.,5383 .549.4.57 0.8255 3.907 1211.343 1,900 1., 560,5 ,526.322 0.86)18 3.964 1160.340 1.980 l.,5821 .50.5.0.57 0.8981 4.018 1113.4.58 2.060 1.6031 48.5.443 0.9344 4.072 1070.217 2.140 1.6236 467.296 0.9707 4.124 1030.210 2.220 1 .6436 4.50.4,57 1.0070 4.175 993.085 2.300 1.6631 434.789 1.0432 4.224 958.544 2.380 1,6822 420.174 1.0795 4.273 926.324 2.460 1,7008 406..510 1.1158 4.320 896.200 2..')40 1,7190 393.707 1.1521 4.366 867.973 2,620 l,73Dimethylamino-phenazathionium chloride; a quinoneimine dye effective against external protozoans and superficial bacterial infections. Microbe Microorganism, such as a virus, bacterium, fungus, or proto- zoan. Micropyle Opening in egg that allows entrance of the sperm. Migration Movement of fish populations. Milt Sperm-bearing fluid. Mitosis The process by which the nucleus is divided into two daughter nuclei with equivalent chromosome complements. MJB Coffee can; essential measuring device used by some fish culturists in lieu of a graduated cylinder. Monthly Temperature Unit (MTU) Equal to one degree Fahrenheit above freezing (32° F) based on the average monthly water tempera- ture (30 days). Morbid Caused by disease; unhealthy; diseased. Morbidity The condition of being diseased. Morbidity Rate The proportion of individuals with a specific disease during a given time in a population. Moribund Obviously progressing towards death, nearly dead. Morphology The science of the form and structure of animals and plants. Mortality The ratio of dead to living individuals in a population. Mortality Rate The number of deaths per unit of population during a specified period. Synonyms: death rate; crude mortality rate; fatality rate. Motile Aeromonas Septicemia (MAS) An acute to chronic infectious disease caused by any motile bacteria belonging to the genus Aeromo- nas, primarily Aeromonas hydrophila or Aeromonas punctate (= Aeromonas liquifaciens) . Synonyms: bacterial hemorrhagic septicemia; pike pest. Mottled Blotched; color spots running together. Mouth Fungus See Columnaris Disease. GLOSSARY 489 Mucking (Egg) The addition of an inert substance such as clay or starch to adhesive eggs to prevent them from sticking together during spawn taking. Most commonly used with esocid and walleye eggs. Mucus A viscid or slimy substance secreted by the mucous glands offish. Mutation A sudden heritable variation in a gene or in a chromosome structure. Mycology The study of fungi. Mycosis Any disease caused by an infectious fungus. Myomere An embryonic muscular segment that later becomes a section of the side muscle of a fish. Myotome Muscle segment. Myxobacteriosis A disease caused by any member of the Myxobacteria group of bacteria. See Peduncle Disease, Cold Water Disease, Fin Rot Disease, Columnaris Disease. Nares The openings of the nasal cavity. Necropsy A medical examination of the body after death to ascertain the cause of death. Synonym for humans: autopsy. Necrosis Dying of cells or tissues within the living body. Nematoda A diverse phylum of roundworms, many of which are plant or animal parasites. Nephrocalcinosis A condition of renal insufficiency due to the precipi- tation of calcium phosphate (CaP04) in the tubules of the kidney. Observed frequently in fish. Niacin One of the water-soluble B-complex vitamins, essential for maintenance of the health of skin and other epithelial tissues in fishes. Nicotinic Acid See Niacin. Nitrification A method through which ammonia is biologically oxi- dized to nitrite and then nitrate. Nitrite The NO7 ion. Nitrogen An odorless, gaseous element that makes up 78% of the earth's atmosphere and is a constituent of all living tissue. It is almost inert in its gaseous form. Nitrogenous Wastes Simple nitrogen compounds produced by the metabolism of proteins, such as urea and uric acid. Nonpathogenic Refers to an organism that may infect but causes no disease. Nostril See Nares. Nutrient A chemical used for growth and maintenance of an organism. Nutrition The sum of the processes in which an animal (or plant) takes in and utilizes food. Nutritional Gill Disease Gill hyperplasia caused by deficiency of pan- tothenic acid in the diet. 490 FISH HATCHERY MANAGEMENT Ocean Ranching Type of aquaculture involving the release of juvenile aquatic animals into marine waters to grow on natural foods to har- vestable size. Open-Formula Feed A diet in which all the ingredients and their pro- portions are public (nonproprietary). Operculum A bony flap-like protective gill covering. Optic Referring to the eye. Osmoregulation The process by which organisms maintain stable osmotic pressures in their blood, tissues, and cells in the face of differ- ing chemical properties among tissues and cells, and between the organism and the external environments. Osmosis The diffusion of liquid that takes place through a semiperme- able membrane between solutions starting at different osmotic pres- sures, and that tends to equalize those pressures. Water always will move toward the more concentrated solution, regardless of the sub- stances dissolved, until the concentration of dissolved particles is equalized, regardless of electric charge. Osmotic Pressure The pressure needed to prevent water from flowing into a more concentrated solution from a less concentrated one across a semipermeable membrane. Outfall Wastewater at its point of effluence or its entry into a river or other body of water. Ovarian Fluid Fluid surrounding eggs inside the female's body. Ovaries The female reproductive organs. Overt Disease A disease, not necessarily infectious, that is apparent or obvious by gross inspection; a disease exhibiting clinical signs. Oviduct The tube that carries eggs from the ovary to the exterior. Oviparous Producing eggs that are fertilized, develop, and hatch out- side the female body. Ovoviviparous Producing eggs, usually with much yolk, that are fertil- ized internally. Little or no nourishment is furnished by the mother during development; hatching may occur before or after expulsion. Ovulate Process of producing mature eggs capable of being fertilized. Ovum (plural: Ova) Egg cell or single egg. Oxidation Combination with oxygen; removal of electrons to increase positive charge. Oxytetracycline (Terramycin) One of the tetracycline antibiotics pro- duced by Streptomyces rimosus and effective against a wide variety of bacteria pathogenic to fishes. Pancreas The organ that functions as both an endocrine gland secreting insulin and an exocrine gland secreting digestive enzymes. GLOSSARY 491 Pantothenic Acid One of the essential B-complex vitamins. Para-aminobenzoic Acid (PABA) A vitamin- like substance thought to be essential in the diet for maintenance of health of certain fishes. No requirement determined for fish. Parasite An organism that lives in or on another organism (the host) and that depends on the host for its food, has a higher reproductive potential than the host, and may harm the host when present in large numbers. Parasite, Obligate An organism that cannot lead an independent, non- parasitic existence. Parasiticide Antiparasite chemical (added to water) or drug (fed or injected). Parasitology The study of parasites. Parr A life stage of salmonid fishes that extends from the time feeding begins until the fish become sufficiently pigmented to obliterate the parr marks, usually ending during the first year. Parr Mark One of the vertical color bars found on young salmonids and certain other fishes. Part Per Billion (ppb) A concentration at which one unit is contained in a total of a billion units. Equivalent to one microgram per kilogram (l /ug/kg), or nanoliter per liter (l nl/liter). Part Per Million (ppm) A concentration at which one unit is contained in a total of a million units. Equivalent to one milligram per kilogram (l ml/kg) or one microliter per liter (l yul/liter). Part Per Thousand (ppt or /oo) A concentration at which one unit is contained in a total of a thousand units. Equivalent to one gram per kilogram (l g/kg) or one milliliter per liter (l ml/liter). Normally, this term is used to specify the salinity of estuarine or sea waters. Pathogen, Opportunistic An organism capable of causing disease only when the host's resistance is lowered. Compare with Secondary Invader. Pathology The study of diseases and the structural and functional changes produced by them. Pectoral Fins The anterior and ventrally located fins whose principle function is locomotor maneuvering. Peduncle Disease A chronic, necrotic disease of the fins, primarily the caudal fin, caused by invasion of a myxobacterium (commonly Cyto- phaga psychrophilia) into fin and caudal peduncle tissue of an unhealthy fish. Synonyms: fin rot disease; cold water disease. Pelvic Fins Paired fins corresponding to the posterior limbs of the higher vertebrates (sometimes called ventral fins), located below or behind the pectoral fins. Peritoneum The membrane lining the abdominal cavity. Perivitelline Fluid Fluid lying between the yolk and outer shell (chorion) of an egg. 492 FISH HATCHERY MANAGEMENT Perivitelline Space Area between yolk and chorion of an egg where embryo expansion occurs. Permanganate, Potassium KMnO,; strong oxidizing agent used as a disinfectant and to control external parasites. Petechia A minute rounded spot of hemorrhage on a surface, usually less than one millimeter in diameter. pH An expression of the acid- base relationship designated as the loga- rithm of the reciprocal of the hydrogen-ion activity; the value of 7.0 expresses neutral solutions; values decreasing below 7.0 represent increasing acidity; those increasing above 7.0 represent increasingly basic solutions. Pharynx The cavity between the mouth and esophagus. Phenotype Appearance of an individual as contrasted with its genetic makeup or genotype. Also used to designate a group of individuals with similar appearance but not necessarily identical genotypes. Photoperiod The number of daylight hours best suited to the growth and maturation of an organism. Photosynthesis The formation of carbohydrates from carbon dioxide and water that takes place in the chlorophyll-containing tissues of plants exposed to light; oxygen is produced as a by-product. Phytoplankton Minute plants suspended in water with little or no capa- bility for controlling their position in the water mass; frequently referred to as algae. Pig Trough See Von Bayer Trough. Pigmentation Disposition of coloring matter in an organ or tissue. Pituitary Small endocrine organ located near the brain. Planting of Fish The act of releasing fish from a hatchery into a specific lake or river. Synonyms: distribution; stocking. Plasma The fluid fraction of the blood, as distinguished from corpuscles. Plasma contains dissolved salts and proteins. Compare with Serum. Poikilothermic Having a body temperature that fluctuates with that of the environment. Pollutant A term referring to a wide range of toxic chemicals and organic materials introduced into waterways from industrial plants and sewage wastes. Pollution The addition of any substance not normally found in or occurring in a material or ecosystem. Population A coexisting and interbreeding group of individuals of the same species in a particular locality. Population Density The number of individuals of one population in a given area or volume. Portal of Entry The pathway by which pathogens or parasites enter the host. GLOSSARY 493 Portal of Exit The pathway by which pathogens or parasites leave or are shed by the host. Posttreatment Treatment of hatchery wastewater before it is discharged into the receiving water (pollution abatement). Pox A disease sign in which eruptive lesions are observed primarily on the skin and mucous membranes. Pox Disease A common disease of freshwater fishes, primarily minnows, characterized by small, flat epithelial growths and caused by a virus as yet unidentified. Synonyms: carp pox; papilloma. Pretreatment Treatment of water before it enters the hatchery. Prevention, Disease Steps taken to stop a disease outbreak before it occurs; may include environmental manipulation, immunization, administration of drugs, etc. Progeny Offspring. Progeny Test A test of the value of an individual based on the perform- ance of its offspring produced in some definite system of mating. Prophylactic Activity or agent that prevents the occurrence of disease. Protein Any of the numerous naturally occurring complex combinations of amino acids that contain the elements carbon, hydrogen, nitrogen, oxygen and occasionally sulfur, phosphorus or other elements. Protozoa The phylum of mostly microscopic animals made up of a sin- gle cell or a group of more or less identical cells and living chiefly in water; includes many parasitic forms. Pseudobranch The remnant of the first gill arch that often does not have a respiratory function and is thought to be involved in hormone activation or secretion. Pseudomonas Septicemia A hemorrhagic, septicemic disease of fishes caused by infection of a member of the genus Pseudomonas. This is a stress- mediated disease that usually occurs as a generalized septicemia. See Bacterial Hemorrhagic Septicemia. Pyloric Cecum See Cecum. Pyridoxine (Vitamin B,,) One of the B-complex vitamins involved in fat metabolism, but playing a more important role in protein metabo- lism. As a result, carnivorous fish have stringent requirements for this vitamin. Quaternary Ammonium Compounds Several of the cationic surface- active agents and germicides, each with a quaternary ammonium structure. They are bactericidal but will not kill external parasites of fish. Generally, they are used for controlling external bacterial patho- gens and disinfecting hatching equipment. Radii of Scale Lines on the proximal part of a scale, radiating from near center to the edge. 494 FISH HATCHERY MANAGEMENT Random Mating Matings without consideration of definable charac- teristics of the broodfish; nonselective mating. Ration A fixed allowance of food for a day or other unit of time. Ray A supporting rod for a fin. There are two kinds: hard (spines) and soft rays. Rearing Unit Any facility in which fish are held during the rearing process, such as rectangular raceways, circular ponds, circulation race- ways, and earth ponds. Recessive Character possessed by one parent that is masked in the progeny by the corresponding alternative or dominant character derived from the other parent. Reciprocal Mating (Crosses) Paired crosses in which both males and females of one parental line are mated with the other parental line. Reconditioning Treatment Treatment of water to allow its reuse for fish rearing. Rectum Most distal part of the intestine; repository for the feces. Red Pest See Motile Aeromonas Disease. Red Sore Disease See Vibriosis. Redd Area of stream or lake bottom excavated by a female salmonid during spawning. Redmouth Disease An original name for bacterial hemorrhagic septicemia caused by an infection of Aeromonas hydrophila specifically. Synonyms: motile aeromonas disease; bacterial hemorrhagic septicemia. Residue, Tissue Quantity of a drug or other chemical remaining in body tissues after treatment or exposure is stopped. Resistance The natural ability of an organism to withstand the effects of various physical, chemical, and biological agents that potentially are harmful to the organism. Resistant, Drug Said of a microorganism, usually a bacterium, that can- not be controlled (inhibited) or killed by a drug. Reuse, Recycle The use of water more than one time for fish propaga- tion. There may or may not be water treatment between uses and dif- ferent rearing units may be involved. Riboflavin An essential vitamin of the B-complex group (B2). Roccal See Quaternary Ammonium Compounds. Roe The eggs of fishes. Roundworm See Nematoda. Sac Fry A fish with an external yolk sac. Safe Concentration The maximum concentration of a material that produces no adverse sublethal or chronic effect. Salinity Concentration of sodium, potassium, magnesium, calcium, GLOSSARY 495 bicarbonate, carbonate, sulfate, and halides (chloride, fluoride, bromide) in water. See Dissolved Solids. Sample A part, piece, item, or observation taken or shown as representa- tive of a total population. Sample Count A method of estimating fish population weight from individual weights of a small portion of the population. Sanitizer A chemical that reduces microbial contamination on equip- ment. Saprolegniasis An infection by fungi of the genus Saprolegnia, usually on the external surfaces of a fish body or on dead or dying fish eggs. Saturation In solutions, the maximum amount of a substance that can be dissolved in a liquid without it being precipitated or released into the air. Scale Formula A conventional formula used in identifying fishes. "Scales 7 + 65 + 12," for example, indicates 7 scales above the lateral line, 6.5 along the lateral line, and 12 below it. Scales Above the Lateral Line Usually, the number of scales counted along an oblique row beginning with the first scale above the lateral line and running anteriorly to the base of the dorsal fin. Scales Below the Lateral Line The number of scales counted along a row beginning at the origin of the anal fin and running obliquely dor- sally either forward or backward, to the lateral line. For certain species this count is made from the base of the pelvic fin. Sea Water Water containing from 3.0 to 3.5"o total salts. Secchi Disk A circular metal plate with the upper surface divided into four quadrants, two painted white and two painted black. It is lowered into the water on a graduated line, and the depth at which it disap- pears is noted as the limit of visibility. Second Dorsal Fin The posterior of two dorsal fins, usually the soft- rayed dorsal fin of spiny-rayed fishes. Secondary Invader An opportunist pathogen that obtains entrance to a host following breakdown of the first line of defense. Sediment Settleable solids that form bottom deposits. Sedimentation Pond (Settling Basin) A wastewater treatment facility in which settleable solids are removed from the hatchery effluent. Selective Breeding Selection of mates in a breeding program to pro- duce offspring possessing certain defined characteristics. Sensitive, Drug Said of a microorganism, usually a bacterium, that can be controlled (inhibited) or killed by use of a drug. See Resistant, Drug. Septicemia A clinical sign characterized by a severe bacteremic infec- tion, generally involving the significant invasion of the blood stream by microorganisms. 496 FISH HATCHERY MANAGEMENT Serum The fluid portion of blood that remains after the blood is allowed to clot and the cells are removed. Settleable Solids That fraction of the suspended solids that will settle out of suspension under quiescent conditions. Shocking (Eggs) Act of mechanically agitating eggs, which ruptures the perivitelline membranes and turns infertile eggs white. Short Bath A type of bath most useful in facilities having a controllable rapid exchange of water. The water flow is stopped, and a relatively high concentration of chemical is thoroughly mixed in and retained for about 1 hour. Side Effect An effect of a chemical or treatment other than that intended. Sign Any manifestation of disease, such as an aberration in structure, physiology, or behavior, as interpreted by an observer. Note the term "symptom" is only appropriate for human medicine because it includes the patient's feelings (sensations) about the disease. Silt Soil particles carried or deposited by moving water. Single-pass System A system in which water is passed through fish rearing units without being recycled and then discharged from the hatchery. Sludge The mixture of solids and water that is drawn off a settling chamber. Smolt Juvenile salmonid at the time of physiological adaptation to life in the marine environment. Snout The portion of the head in front of the eyes. The snout is meas- ured from its most anterior tip to the anterior margin of the eye socket. Soft-egg Disease Pathological softening of fish eggs during incubation, the etiological agent(s) being unknown but possibly a bacterium. Soft Fins Fins with soft rays only, designated as soft dorsal, etc. Soft Rays Fin rays that are cross-striated or articulated, like a bamboo fishing pole. Solubility The degree to which a substance can be dissolved in a liquid; usually expressed as milligrams per liter or percent. Spawning (Hatchery context) Act of obtaining eggs from female fish and sperm from male fish. Species The largest group of similar individuals that actually or poten- tially can successfully interbreed with one another but not with other such groups; a systematic unit including geographic races and varieties, and included in a genus. Specific Drug A drug that has therapeutic effect on one disease but not on others. Spent Spawned out. GLOSSARY 497 Spermatozoon A male reproductive cell, consisting usually of head, middle piece, and locomotory flagellum. Spinal Cord The cylindrical structure within the spinal canal, a part of the central nervous system. Spines Unsegmented rays, commonly hard and pointed. Spiny Rays Stiff or noncross-striated fin rays. Spleen The site of red blood cell, thrombocyte, lymphocyte, and granu- locyte production. Sporadic Disease A disease that occurs only occasionally and usually as a single case. Stabilization Pond A simple waste-water treatment facility in which organic matter is oxidized and stabilized (converted to inert residue). Standard Length The distance from the most anterior portion of the body to the junction of the caudal peduncle and anal fin. Standard Metabolic Rate The metabolic rate of poikilothermic animals under conditions of minimum activity, measured per unit time and body weight at a particular temperature. Close to basal metabolic rate, but animals rarely are at complete rest. See Basal Metabolism. Sterilant An agent that kills all microorganisms. Sterilize To destroy all microorganisms and their spores in or about an object. Stock Group of fish that share a common environment and gene pool. Stomach The expansion of the alimentary tract between the esophagous and the pyloric valve. Strains Group of fish with presumed common ancestry. Stress A state manifested by a syndrome or bodily change caused by some force, condition, or circumstance (i.e., by a stressor) in or on an organism or on one of its physiological or anatomical systems. Any condition that forces an organism to expend more energy to maintain stability. Stressor Any stimulus, or succession of stimuli, that tends to disrupt the normal stability of an animal. Subacute Not lethal; between acute and chronic. Sulfadimethoxine Sulfonamide drug effective against certain bacterial pathogens of fishes. Sulfaguanidine Sulfonamide drug used in combination with sulfamera- zine to control certain bacterial pathogens of fishes. Sulfamerazine Sulfonamide drug effective against certain bacterial pathogens of fish. Sulfamethazine (Sulmet) Sulfonamide drug effective against certain bacterial pathogens of fishes. Sulfate Any salt of sulfuric acid; any salt containing the radical SOf. Sulfisoxasole (Gantrisin) Sulfonamide drug effective against certain bacterial pathogens of fishes. 498 FISH HATCHERY MANAGEMENT Sulfomerthiolate (Thimerfonate Sodium) Used as an external disinfec- tant of living fish eggs. Sulfonamides Antimicrobial compounds having the general formula H^NSO^ and acting via competition with /)-aminobenzoic acid in folic acid metabolism (for example, sulfamerazine, sulfamethazine). Superior As applied to the mouth, opening in an upward direction. Supersaturation Greater- than- normal solubility of a chemical as a result of unusual temperatures or pressures. Supplemental Diet A diet used to augment available natural foods. Generally used in extensive fish culture. Susceptible Having little resistance to disease or to injurious agents. Suspended Solids Particles retained in suspension in the water column. Swim Bladder See Air Bladder. Swim-up Term used to describe fry when they begin active swimming in search of food. Syndrome A group of signs that together characterize a disease. Temperature Shock Physiological stress induced by sudden or rapid changes in temperature, defined by some as any change greater than 3 degrees per hour. Tender Stage Period of early development, from a few hours after fertil- ization to the time pigmentation of the eyes becomes evident, during which the embryo is highly sensitive to shock. Also called green-egg stage, sensitive stage. Terramycin See Oxytetracycline. Testes The male reproductive organs. Therapeutic Serving to heal or cure. Thiamine An essential B-complex vitamin that maintains normal car- bohydrate metabolism and is essential for certain other metabolic processes. Thiosulfate, Sodium (Sodium Hyposulfite, Hypo, Antichlor) Na2S203; used to remove chlorine from solution or as a titrant for determination of dissolved oxygen by the Winkler method. Titration A method of determining the strength (concentration) of a solution by adding known amounts of a reacting chemical until a color change is detected. Tocopherol Vitamin E; an essential vitamin that acts as a biological antioxidant. Topical Local application of concentrated treatment directly onto a lesion. Total Dissolved Solids (TDS) See Dissolved Solids. Total Length The distance from the most anterior point to the most posterior tip of the fish tail. GLOSSARY 499 Total Solids All of the solids in the water, including dissolved, suspended, and settleable components. Toxicity A relative measure of the ability of a chemical to be toxic. Usually refers to the ability of a substance to kill or cause an adverse effect. High toxicity means that small amounts are capable of causing death or ill health. Toxicology The study of the interactions between organisms and a toxi- cant. Toxin A particular class of poisons, usually albuminous proteins of high molecular weight produced by animals or plants, to which the body may respond by the production of antitoxins. Transmission The transfer of a disease agent from one individual to another. Transmission, Horizontal Any transfer of a disease agent between indi- viduals except for the special case of parent-to-progeny transfer via reproductive processes. Transmission, Vertical The parent- to- progeny transfer of disease agents via eggs or sperm. Trauma An injury caused by a mechanical or physical agent. Trematoda The flukes. Subclass Monogenea: ectoparasitic in general, one host; subclass Digenea: endoparasitic in general, two hosts or more. Tumor An abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the tissues and persists in the same exces- sive manner after the disappearance of the stimuli that evoked the change. Turbidity Presence of suspended or colloidal matter or planktonic organisms that reduces light penetration of water. Turbulence Agitation of liquids by currents, jetting actions, winds, or stirring forces. Ubiquitous Existing everywhere at the same time. UDN See Ulcerative Dermal Necrosis. Ulcer A break in the skin or mucous membrane with loss of surface tis- sue; disintegration and necrosis of epithelial tissue. Ulcer Disease An infectious disease of eastern brook trout caused by the bacterium Hemophilus piscium. Ulcerative Dermal Necrosis (UDN) A disease of unknown etiology occurring in older fishes, usually during spawning, and primarily involving salmonids. United States Pharmacopeia (USP) An authoritative treatise on drugs, products used in medicine, formulas for mixtures, and chemical tests used for identity and purity of the above. 500 FISH HATCHERY MANAGEMENT Urea One of the compounds in which nitrogen is excreted from fish in the urine. Most nitrogen is eliminated as ammonia through the gills. Uremia The condition caused by faulty renal function and resulting in excessive nitrogenous compounds in the blood. Urinary Bladder The bladder attached caudally to the kidneys; the kidneys drain into it. Urogenital Pore External outlet for the urinary and genital ducts. Vaccine A preparation of nonvirulent disease organisms (dead or alive) that retains the capacity to stimulate production of antibodies against it. See Antigen. Vector A living organism that carries an infectious agent from an infected individual to another, directly or indirectly. Vein A tubular vessel that carries blood to the heart. Vent The external posterior opening of the alimentary canal; the anus. Ventral Fins Pelvic fins. VHS See Viral Hemorrhagic Septicemia. Viable Alive. Vibriosis An infectious disease caused by the bacterium Vibrio anguil- larium. Synonyms: pike pest; eel pest; red sore. Viral Hemorrhagic Septicemia (VHS) A severe disease of trout caused by a virus of the Rhabdovirus group. Synonyms: egtved disease; infectious kidney swelling and liver degeneration (INUL); trout pest. Viremia The presence of virus in the blood stream. Virulence The relative capacity of a pathogen to produce disease. Vitamin An organic compound occurring in minute amounts in foods and essential for numerous metabolic reactions. Vitamin D A radiated form of ergosterol that has not been proved essential for fish. Vitamin K An essential, fat-soluble vitamin necessary for formation of prothrombin; deficiency causes reduced blood clotting. Vitamin Premix A mixture of crystaline vitamins or concentrates used to fortify a formulated feed. Viviparous Bringing forth living young; the mother contributes food toward the development of the embryos. Vomer Bone of the anterior part of the roof of the mouth, commonly tri- angular and often with teeth. Von Bayer Trough A 12-inch V-shaped trough used to count eggs. Warmwater Species Generally, fish that spawn at temperatures above 60°F. The chief cultured warmwater species are basses, sunfish, cat- fish, and minnows. See Coldwater Species; Coolwater Species. GLOSSARY 501 Water Hardening Process by which an egg absorbs water that accumu- lates in the perivitelline space. Water Quality As it relates to fish nutrition, involves dissolved mineral needs of fishes inhabiting that water (ionic strength). Water Treatment Primary: removal of a substantial amount of suspended matter, but little or no removal of colloidal and dissolved matter. Secondary: biological treatment methods (for example, by contact stabilization, extended aeration). Tertiary (advanced): removal of chemicals and dissolved solids. Weir A structure for measuring water flow. Western Gill Disease See Nutritional Gill Disease. Whirling Disease A disease of trout caused by the sporozoan protozoan Myxosoma cere bra lis. White Grub An infestation by the metacercarcial stage of Neodiplos- tomum multicellulata in the liver of many freshwater fishes. White Spot Disease A noninfectious malady of incubating eggs or on the yolk sac of alevins. The cause of the disease is thought to be mechanical damage. Also see Ich. Yellow Grub An infestation by the metacercarial stage of Clinostomum marginatum. Yolk The food part of an egg. Zooplankton Minute animals in water, chiefly rotifers and crustaceans, that depend upon water movement to carry them about, having only weak capabilities for movement. They are important prey for young fish. Zoospores Motile spores of fungi. Zygote Cell formed by the union of two gametes, and the individual developing from this cell. Index The Table of Contents for this book also is intended as a functional index. Acidity (pH) natural waters 11, 15 rearing ponds 110-112 Antimycin A, fish control 93 Ammonia estimation, hatchery water 24-25 ionization tables 378-382 pond effluent 27 production per pound feed 26 removal: chlorine oxidation 23; ion exchange 22; biological nitrification 21-22 toxicity 20-21 upper limit for fish 14 Bass, largemouth broodstock: acquisition 132; maturation 136 carrying capacity, ponds 75-76 diseases: bacterial gill disease 301; European gill rot 314—315; motile aeromonas septicemia (MAS) 309 eggs: disinfection 189; temperature units 191 503 504 FISH HATCHERY MANAGEMENT Bass, largemouth [continued] feeding: guides 253-254; habits 136-137 rearing-pond management 102, 137, 151 spawning 136-137, 151, 152, 192; hormone-induced 173 temperature requirements 136-137, 171 transportation: small containers 366; tank carrying capacity 363 treatment, formalin 276 use of forage fish 136 Bass, smallmouth anesthetics 359 broodstock acquisition 132 disease, European gill rot 314 eggs, temperature units 191 feeding guides 253-254 spawning 136, 152-154 temperature requirements 136-137 Bass, striped broodstock acquisition 132 carrying capacity, ponds 77 disease, European gill rot 314 eggs: development 160-164; incubation 196; sampling 159-160; temperature units 191 feeding guide 254 grading 83 oxygen requirements 8 rearing-pond management 102 spawning 134-135, 156, 159, 164—165; hormone-induced 173 temperature requirements 134-135 transportation: carrying capacity 363; stress 358—359 treatment, formalin 276 tolerance, pH 1 1 Biological design criteria 51-55 Biological Oxygen Demand (BOD), production per pound feed 27 Bluegill broodstock acquisition 138 carrying capacity, ponds 76 culture 154 diet 138 disease, bacterial gill disease 301 eggs, temperature units 191 rearing-pond management 102, 138 INDEX 505 Bluegill {continued) spawning 136; natural 151 temperature requirements 136 transportation: small containers 366; tanks 363 treatment, formalin 276 used as forage fish 140 Box filter 93 Branding 148 Cage culture 48-49 Calcium fertilizer 100-101 hatchery water 15 Carbon dioxide hatchery water 15 plant growth 97 pond acidity 110-112 tolerated, fish 9-10 Carp, common diseases: European gill rot 314; furunculosis 306; hemorrhagic septicemia 266; Lernaea 334; spring viremia 267 source, pituitary hormone 172 spawning 136; hormone-induced 173 stress, disease 267 temperature requirements 136 Carrying capacity 63-78 Catfish, blue broodstock selection 148 disease, channel catfish virus disease 298 tolerance, salinity 14 Catfish, channel broodstock selection 148 capture 132 carrying capacity: pond 138 (broodstock), 76-77 (fingerlings); raceways 77 diet 138 diseases: Ambiphrya [Scyphidia) 323; bacterial gill disease 301; channel catfish virus disease 267, 298; Cleidodiscus 330; Epistylis 319-320; fungus disease (eggs) 314; furunculosis 306; Henneguya 325; Ich 316; Ichtyobodo [Costia) 316; motile aeromonas septicemia (MAS) 309; Trichophrya 323 F)0(] FISH HATCHERY MANAGEMENT Catfish, channel [continued] eggs: handling L')4-155; hatching jars 196; incubation trough 195; temperature units 191 feeds and feeding: conversion '2'26, Til \ energy availability 22^- Til \ fish flavor 224; floating and sinking 23,5; formu- lated 217, 400; frequency 257; guide 249-252; initial 256; sizes 259 grading 84 growth, temperature- related 211 light control 171 nutrition: carbohydrates 218-220; diseases 390-393; lipids 224; proteins 217; vitamins 227-228 selective breeding 147 sex determination 138 spawning 134-135; hormone-induced 173; pens and recepta- cles 155 stress 267 temperature: control 171; requirements 134—135; Standard Environmental Temperature (SET) 211 tolerance: ammonia 21; nitrite 22; pH 11; salinity 14; tem- perature 134-137; total dissolved solids 12 toxicity: ammonia 21; nitrite 22; toxaphene, feeds 233 transportation 362-363; small containers 367 treatments: copper sulfate 277; formalin 276; nitrofurans 281; potassium permanganate 278; salt 275; Terramycin 280 Catfish, flathead spawning 134-135 temperature requirements 134—135 Catfish, white, broodstock selection 148 Char, Arctic, spawning channels 150 Chemical Oxygen Demand (COD), pond effluent 27 Chemicals {see Drugs and chemicals) Chlorine ammonia removal, hatchery water 23 decontamination: equipment 283; hatchery 284 fish control 93 neutralization 283 pond disinfection 90 toxicity 14, 283 Circular rearing units 40-43 Clinoptilolite, ion-exchange ammonia removal 22 Condition factor, calculation 61 INDEX 507 Crayfish, problem in ponds 114 Density Index 71-74 Diseases bacterial: columnaris 302-303; enteric redmouth (ERM) 306-308; fin rot 304; furunculosis 304-306; bacterial kid- ney disease 312-313; motile aeromonas septicemia (MAS) 307-310; peduncle disease 303-304; vibriosis 310-311 certification 293 control 263- 265 environmental: blue sac 268; coagulated yolk (white-spot) 268; gas bubble disease 9 fungal 314-315 immunization 286-288 inspections 292-293 leaflets 342-344 nutritional 390-393 parasitic: Ambiphrya [Scyphidia) 321, 323; Argulus 334; Cerato- myxa 326-327; Chilodonella 319; Cleidodiscus 330, 332; Dac- tylogyrus 330; Epistylis 319-322; Gyrodactylus 330-331; Hen- neguya 324-326; Hexamita 323-324; Ichtyobodo [Costia] 315-316; Ichthyophthirius 316-319; Lernaea 334; Pleistophora 328-329; Sanguinicola 332-333; Trichodina 320-321; Tricho- phrya 322-323 recognition 264—265 regulations 289-292 resistance 286-287 treatment 266-270; constant-flow 272, 403; drug coating, pel- lets 405; feeding, injection 273; flush 272; prolonged bath 271, 402-403 vaccination 288-289 viral: channel catfish virus disease (CCV) 267, 298; her- pesvirus disease of salmonids 298-299; infectious hemato- poietic necrosis (IHN) 267, 296-297; infectious pancreatic necrosis (IPN) 294; lymphocystis disease 299-300; viral hemorrhagic septicemia (VHS) 295-296 Dissolved gas criteria 10 Drugs and chemicals dosages and characteristics: acriflavin 281-282; calcium hydroxide 282; copper sulfate 276-277; de-«-butyl tin oxide 282; formalin 275-276; iodophores 282; Masoten 282-283; nitrofurans 280-281; potassium permanganate 277-278; quaternary ammonium compounds 278-279; salt 275; sulfonamides 281; Terramycin 279-280 508 FISH HATCHKRV MANAGEMENT Drugs and chemicals [continued) registration 274-27.5 storage 274 Earthen ponds 47-48 Eel, American, infected with Ich 317 Eggs (2see also individual species) disinfection 189, 275, 282, 285, 314 transportation (shipping) 193 English- metric conversions 375-377 Feeds and feeding [see also individual species) application practices 238-239 calculations 242-255 conversion 239, 242 Daphnia, food source 248 frequency 255-257 guides: coolwater fishes 248-249; salmonids 239-248; warm- water fishes 249-254 fish meal 215 formulated: antioxidants 232; closed 236; deficiencies 264, 390-400; specifications 390-400; dust, particles 234, 236, 238; energy levels 225-227; fat-soluble vitamins 227; fiber content 231, 232, 236; floating 235, 251; mineral levels 229-231; moisture 234, 235, 238; open 235-236; pigmenta- tion 232, 235; protein levels 215-217, 236; sinking 234; trace minerals 231; vitamin levels 227-229, 232; water- soluble vitamins 227 habits, broodfish 132-134 handling 236-238 hatchery constant 245 manufacturing: lipid rancidity 221, 222, 238; lipid toxicity 222; organic toxicants 233, 390-400; pesticide contamina- tion 221; spray coating 235, 405; temperature 234, 235 natural foods 233 packaging 236 performance 238 storage 235-238 Fertilizers combinations 101-102 composition 97 pond application 96 INDEX 509 Flow Index 67-71 Forage fish goldfish 142-143 herring 140 minnow, fathead 141-142 shad 140 shiner, golden 143-144 sucker, white 140-141 tilapia 140, 144 Goldfish diseases: Ambiphrya [Scyphidia] 323; Chilodonella 319; furuncu- losis 306; Lernaea 334; motile aeromonas septicemia (MAS) 308 rearing- pond management 102 spawning 136; hormone-induced 172 temperature requirements 136 tolerance, nitrogen gas 9 used as forage fish 140, 142-143 Growth projections 62—63 Hatchery design standards 34-39 Heavy-metal toxicity: cadmium, copper, lead, mercury, zinc 13, 14 Hyamine, pond disinfection 90 Hybrid vigor 148 Hybridization (cross breeding) 144, 148-149 Hydrogen cyanide 10 Hydrogen sulfide hatchery water 15 rearing ponds 1 12 toxicity 10, 14 Interspecific hybrids 148—149 Inventory methods 78—83 Iron, hatchery water 15 Lamprey, sea, furunculosis 306 Length- weight relationships 60-61; tables 406-467 Lime, pond disinfection 89-90 510 IISH IIAICHKRY MANACJKMEN'r Magnesium, hatchery water 15 Manganese, hatchery water 15 Metric- English conversions 375-376 Minerals, water enrichment 13 Muskellunge broodstock acquisition 132 eggs, temperature units 191, 192 feeds and feeding: formulated 248-249, 399, 400; guides 248-249; initial 256 forage fish for 140 hybridization 148 nutrition: diseases 390-393; protein requirements 217 spawning 134-135, 157 transportation, carrying capacity 364 Muskie, tiger {see also Pike, northern; muskellunge), hatchery constant 249 Nets, seines broodfish capture 132 inventory 82-83 Nitrate hatchery water 15 fertilizer 98 pond effluent 27 production per pound feed 26 Nitrite, toxicity 14, 22 Osmoregulation 213 Oxygen hatchery water 6-8, 15 ponds 108-110 saturation nomogram 5 Ozone sterilant 18-19 toxicity 14 Pen rearing 50 pH [see acidity) Phosphorus, phosphate hatchery water 15 fertilizer 98-100 pond effluent 27 production per pound feed 26 Pickerel, chain, protein requirements 217 INDEX 511 Pike, northern broodstock acquisition 132 carrying capacity, ponds 11-1% diseases: European gill rot 314; furunculosis 306 eggs 159; temperature units 191 feeds and feeding: formulated 248, 399, 400; frequency 256; guide 248-249 forage fish for 140 grading 83 hybridization 148 nutrition: diseases 390-393; protein requirements 217 spawning 134—135, 156-159 sperm storage 168 transportation: small containers 367; tank carrying capacity 364 temperature requirements 134-135 Polychlorinated biphenyls (PCB's), toxicity 14 Potassium, fertilizer 100 Rearing facilities characteristics 52-53 selection 50 Record keeping factors considered 114-115 hatchery codes 387-388 lot history production charts 117-122 ponds 126 production summaries 122-126 rectangular rearing units circulation ponds 46-47 tanks, raceways 43-46 Roccal, pond disinfection 90 Rotational line-crossing 145-147 Rotenone, fish control 93 Salinity 13-14 Salmon anesthetics 170, 359-360 broodstock acquisition 132 diseases: bacterial gill disease 300; bacterial kidney disease 312-313; Ceratomyxa shasta 326; Chilodonella 319; colum- naris disease 302; enteric redmouth (ERM) 307; fungus 314; furunculosis 304-306; Gyrodactylis 330, Henneguya 325; 512 KISH HATCHERY MANAGEM KNI' Salmon [continued] herpesvirus disease 29H-299; Hexamita salominis 323; Ith 316; Ichtyobodo [Costia] 316; infectious hematopoietic necrosis (IHN) 296-297; infectious pancreatic necrosis (IPN) 294; Myxosoma cerebralis 327; peduncle disease 303-304; Trichodina 320; vibriosis 311; viral hemorrhagic septicemia (VHS) 296 eggs: disinfection 189, 282; incubation 193-200; storage 193; temperature units 191 feeds and feeding: energy availability 226; formulated 209, 235, 396-397, 400; frequency 255-257; guides 239-248; sizes 258; spawning activity 133; storage 236-238 handling, loading 85, 358-359 nutrition: carbohydrates 218-219; diseases 390-393; lipids 222-223; proteins 215 (fry), 216 (yearlings); vitamins 227-228 spawning 165-167 sperm storage 193 stress, disease 265-268 temperature: requirements 134-135; Standard Environmental Temperature (SET) 211 transportation: methods [see Chapter 6); tank carrying capa- city 361 treatments: acriflavin 281; copper sulfate 276-277; formalin 275-276; nitrofurans 280-281; quaternary ammonium com- pounds 278-279; salt 275; sulfonamides 281; Terramycin 279-280 Salmon, Atlantic [see also Salmon) broodstock acquisition 132 diseases: bacterial kidney disease 312; Ceratomyxa shasta 326; enteric redmouth (ERM) 307; herpesvirus disease 299; vibriosis 311; viral hemorrhagic septicemia (VHS) 296 egg development 191 spawning 134-135, 165 temperature requirements 134-135 Salmon, chinook [see also Salmon) diseases: bacterial kidney disease 312; Ceratomyxa shasta 326; enteric redmouth (ERM) 307; Henneguya 325; infectious hematopoietic necrosis (IHN) 296 egg development 191 feeding frequency 257 gamete storage 169 nutrition, protein requirements 216 spawning 134-135; channels 150 temperature requirements 134-135 INDEX 513 Salmon, chum {see also Salmon), carbon dioxide tolerance 9 Salmon, coho {see also Salmon) carbon dioxide tolerance 10 eggs, temperature units 191 feeding guide 242 nutrition, folic acid deficiency 223 oxygen requirements 7-8 spawning 134-135; channels 150 temperature requirements 134—135 Salmon, sockeye {see also Salmon) diseases: bacterial kidney disease 312; Ceratomyxa shasta 326; herpesvirus disease 298; infectious hematopoietic necrosis (IHN) 296 eggs: sensitivity, artificial light 171; temperature units 191 spavining 134-135, 150; photoperiod control 170 sperm storage 169 temperature requirements 134—135 Saltwater fish flesh flavor 233 protein utilization 214 vitamin requirements 229 Sanger, broodstock acquisition 132 Screens, perforated aluminum 91 Sea (ocean) ranching 50 Sedimentation basins 27-30 Selective breeding 144, 145 Settleable solids pond effluent 27 production per pound feed 27 Shad, American spawning 136 temperature requirements 136 Shiner, golden anesthetics, transportation 359 disease, Pleistophora ovariae 328 spawning 136 temperature requirements 136 used as forage 140, 143-144 Shrimp, tadpole, pond nuisance 113-114 Sock filter 93 Solid waste disposal 30-31 Spawning {see also individual species) air-spawning 165-166 aquarium 156 hand stripping 156—159 514 FISH HATCHERY MANAGEMENT Spawning {continued) natural 149-155 open pond 154 pen 154 species summaries 134-137 Specimen, disease diagnosis collection, shipping 335-342 preservation 341-342 Standard disease diagnostic procedures 292 Standard Environmental Temperatures (SET) 211 State abbreviations 389 Steelhead {see also Trout) broodstock acquisition 132 diseases: Ceratomyxa shasta 326; enteric redmouth (ERM) 307 eggs, incubation 199 spawning 165 survival, growth, hatchery-wild crosses 147 Stress diseases 265-268 factors 265; 267-268 handling 85, 358 Sunfish, redear disease, bacterial gill disease 301 eggs, temperature units 191 formulated feed 138 rearing-pond management 102 Suspended solids 10-11 Swedish pond 43 Temperature requirements 134-137 Total alkalinity, hatchery water 15 Total hardness, hatchery water 15 Transportation airplane 348-349 stress 358-359 tanks: aeration 353-355; anesthetics 359-360; carrying capac- ity 360-364; circulation systems 352-353; design 350-352; insulation (A"- factor) 350-351; water quality 355-358 trucks 348-350 Trout anesthetics 170, 359-360 broodstock acquisition 132 INDEX 515 Trout [continued] diseases: bacterial gill disease 300; bacterial kidney disease 312-313; Ceratomyxa shasta 326; Chilodonella 319; colum- naris disease 302; copepod parasites 333-334; enteric red- mouth (ERM) 306-308; Epistylis 319-322; fin rot 304; fungus 314; furunculosis 300, 304-306; Gyrodactylus 330-331; herpesvirus disease 298-299; Hexamila salmonis 323-324; Ich 316-319; Ichtyobodo [Costia] 315-317; infec- tious hematopoietic necrosis (IHN) 296-297; infectious pancreatic necrosis (IPN) 294; motile aeromonas septicemia (mas) 307-310; Myxosoma cerebralis 327; peduncle disease 303-304; Pleistophora 328-329; Sanguinicola davisi 332; Tri- chodina 320-322; vibriosis 310-311; viral hemorrhagic septi- cemia (VHS) 295-296 eggs: coloration 232; development 174-175; disinfection 189, 282; sensitivity, artificial light 190; enumeration 175-185; incubation 193-198; sorting 185-187; storage 193; tempera- ture units 190 feeds and feeding: egg coloration 232; energy availability 225-226; fish flavor 232-233; formulated 234-236, 394-395, 400; frequency 255-257; guides 239-248; initial 255; rates 210; sizes 258; skin coloration 232; spawning activity 133; storage 233-238 handling, loading 358-359 nutrition: carbohydrates 218-219; diseases 222-223 (liver degeneration), 231 (goiter), 390-393; lipids 221-223; phos- phorus absorption 231; proteins 214, 216, 236; vitamins 227-229, 232 oxygen requirements 7 spawning methods 156-159 sperm storage 193 stress, disease 265-268 temperature: requirements 134-135; Standard Environmental Temperatures (SET) 211 tolerance: ammonia 21; nitrite 22; nitrogen gas 9; salinity 13, total dissolved solids 12 toxicity: ammonia 21; nitrite 22 transportation: methods [see Chapter 6); tank carrying capa- city 361 treatments: copper sulfate 276-277; formalin 275-276; nitro- furans 280-281; potassium permanganate 278; quaternary ammonium compounds 278; salt 275; sulfonamides 281; Terramycin 279-280 516 IISH HAUHKRY MANAGEMENT Trout [continued) used, forage fish 140 Trout, brook [see also Trout) hybridization 148 initial feeding 256 mineral absorption 13 shipping, small containers 366 spawning 134-135 temperature requirements 134-135 Trout, brown [see also Trout) initial feeding 256 spawning 134-135 temperature requirements 134-135 Trout, cutthroat {see Trout) Trout, lake [see also Trout) hybridization 148 spawning 134-135 temperature requirements 134-135 Trout, rainbow [see also Trout) anesthetic 170 feeds and feeding: guide 240; initial 256 nutritional diseases 230 selective breeding 145 spawning methods 134-135 temperature requirements 134-135 transportation, small containers 366 Turbidity, ponds 112 V-trap 86- 87 Vertebrates, ponds 114 Volume-weight chemical calculations 402 Walleye broodstock acquisition 132 carrying capacity, ponds 77-78 disease, lymphocystis 299-300 dissolved solids absorption 14 eggs 159, 192; temperature units 191 feeds and feeding: formulated 248, 399, 400; guide 248-249; initial 256 forage fish for 140 INDEX 517 Walleye [continued] nutrition: diseases 390-393; protein 217 oxygen requirements 8 rearing-pond management 102 spawning 132, 134-135 temperature requirements 134—135 transportation: small containers 367; tank carrying capacity 364 Water loss, ponds 1 13 quality criteria 14, 15 reconditioning 19 supply structures 90 Weed control, aquatic biological 103-104 chemical 104-105 mechanical 103 Weight- volume chemical calculations 402 Weir operation, use 384—386 6 U.S. GOVERNMENT PRINTING OFFICE: 1982-329-l.iO RV 1