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Full text of "Fish hatchery management"



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. 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 


(•J<I«S 


Aif 


ud* 




F*CtO' 


F««l 


Mel'es 


mm 




o 


O 


760 


1 OO 


330 


100 


7SO 


1 01 


S55 


200 


741 


1 03 1 


980 


300 


732 


1 04 1 


1310 


4O0 


723 


1 05 


1640 


500 


714 


1 06 ' 


1970 


600 


705 


1 08 


2300 


700 


696 


1 09 


2630 


80O 


687 


111 


2950 


900 


679 


1 12 1 


3280 


1O0O 


67 1 


113 


3610 


1100 


663 


115 ' 


3940 


1200 


655 


1 16 


4270 


1300 


64 7 


1 1 7 


4600 


1400 


6 39 


1 19 


4930 


1500 


631 


1 20 1 


5250 


1600 


623 


1 22 


5580 


1700 


615 


1 24 1 


5910 


1800 


608 


1 25 


62 40 


1900 


601 


1 26 


6560 


2000 


594 


1 28 


6900 


2100 


587 


1 30 


7220 


2200 


5BO 


1 31 


7550 


2300 


573 


1 33 


7880 


2400 


566 


1 34 


8200 


2500 


560 


,3. 



5 10 15 20 25 30 

Water temperatures "Cent. 



^>o<> 




Oxygen mgm per liter (PPM) 
5 6 7 8 9 10 11 12 13 H 15 16 17 

i J ij j i| i ,i u l || i, i ii;ii|l | i,i|ii| i |i Jr ii|i| i ; iNlM i |i || lMl | ll l ^ |l M |I ^Ni l »^lM ||| l l|l M |l||||;||| ^| |l||^ | ; l^ l M l M |||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 










% 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) 


0.15 




0-0.5 


Ferrous ion 










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 











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 ,^p m 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 

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P- 

Andrews, James W., Lee H. Knight, and Takeshi Mural 1972. Temperature requirements 
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Baummer, John C, Jr., and L. D. Jensen. 1969. Removal of ammonia from aquarium water 
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56 FISH HATCHERY MANAGEMENT 

Bovi), Claude E. 1!)7;). Water quality in warmwater fish ponds. Agricultural Experimental 
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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 
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332 p. 

DeCola, Joseph N. 1970. Water quality requirements for Atlantic salmon. US Department 
of the Interior, Federal Water Quality Administration, Northeast Region, Needham 
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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 
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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. 
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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- 

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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. 

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, and R. G. PiPER. 1973. Effects of water re-use on rainbow trout in hatcheries. Progres- 
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_, 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 

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439-443. 



58 FISH HAIX'HKRY MANAGEMENT 

, and Ronald D. Mayo. 1972. Salmonid hatchery water re-use systems. Technical 

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Warm Water In-service Training School, Marion, Alabama. 244 p. 



HATCHERY REQUIREMENTS 59 

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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 








5 








^ 


\ 
























1 3 


5 1 


1 


5 2 


2 


5 3 


3 


5 4 


4 


5 5 






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. 







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) 





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) 





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 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 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 
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 



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 

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. 



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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. 
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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 

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Glen Hammer, and A. M. Phillips, Jr. 1961. The effect of grading on the total 

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130 FISH HATCHERY MANAGEMENT 

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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 


















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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 




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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. 

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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- 
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Geibel, G. E., and P. J. Murray. 1961. Channel catfish culture in California. Progressive 
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Hagen, William, Jr. 1953. Pacific salmon; hatchery propagation and its role in fishery man- 
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Hamano, Shigerl'. 1961. On the spermatozoa agglutinating agents of the dog salmon and 
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Haskell, D. C. 1952. Egg inventory: enumeration with the egg counter. Progressive Fish- 
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Hendersu.N', Harmon. 1965. Observation on the propagation of flathead catfish in the San 
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Henderson, Nancy E., and John E. Dewar, 1959. Short-term storage of brook trout milt. 
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Henderson, W. H., and S. Winckler. 1968. A winning combination. Texas Parks and 
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HiNER, L.ALRENCE. 1961. Propagation of northern pike. Transactions of the American 
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HORTON, Howard F., and Alxin G. Ott. 1976. Cryopreservation of fish spermatozoa and 
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Jones, Irving W., and Carl H. Copper. 1965. An accurate photoelectric egg counter using a 
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JURGENS, K. C, and W. H. Brown. 1954. Chilling the eggs of the largemouth bass. Progres- 
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Kalman, Sumner M. 1959. Sodium and water exchange in the trout egg. Journal of Cellular 
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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- 
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Lessm.AN, Charles A. 1978. Effects of gonadotropin mixtures and two steroids on inducing 
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Lucas, K. C. 1960. The Robertson Creek spawning channel. The Canadian Fish Culturist 
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McClary, Denny. 1967. Development and use of an egg counter. Proceedings of the 
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McCraREN, J. P. 1!)73. lodophor controls microorganisms on catfish eggs. Fish Health News 
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1964. Studies on reproduction of rainbow trout, Salmo gairdneri, with special reference 

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Nursall, J. R., and A. D. Hasler. 1952. A note on experiments designed to test the viability 
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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 
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Pecor, Charles H. 1978. Intensive culture of tiger muskellunge in Michigan during 1976 
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Phillips, A. M. 1957. Cortland in-service training school manual. US Fish and Wildlife Serv- 
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Phillips, Arthur M., Jr., and Richard F. Dumas. 1959. The chemistry of developing brown 
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Phillips, Raymond A. 1966. Walleye propagation. US Fish and Wildlife Service, Washing- 
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Pisarenkova, A. S. 1958. Storage and transportation of sperm of rainbow trout and pike. 
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Plosila, Daniel S., and Walter T. Keller 1974. Effects of quantity of stored sperm and 
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, 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. 
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Ramaswami, L. S., and B. L Sundararaj. 1958. Action of enzymes on the gonadotrophic ac- 
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Reisenbichler, R. R., and J. D. McIntyre. 1977. Genetic differences in growth and survival 
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Reseach Board of Canada 34(l):123-128. 

RicKER, W. E. 1970. Hereditary and environmental factors affecting certain salmonid popula- 
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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 
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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. 
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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 
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, and R. D. Pollock. 19f)(i. Siltation and egg survival in incubation channels. Transac- 
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Sneed, K. E., and H. P. Clemens. 1956. Survival of fish sperm after freezing and storage at 
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Snow, J. R. 1959. Notes on the propagation of the flathead catfish, Pylodictis olivaris 
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, R. O. Jones, and W. A. Rogers. 1964. Marion in-service training school manual. US 

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Progressive Fish-Culturist 28(l):19-28. 

19()7. Striped bass rearing. North Carolina Cooperative Fishery Unit, North Carolina 

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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 

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ZiRGES, Malcolm H., and Lyle D. Curtis. 1972. Viability of fall chinook salmon eggs 
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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 kcal 


Ash 


10% 


X 





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 





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* 





0.04 


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 





2.3 


Inositol 


182 





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 

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Beyerle, George B. 1975. Summary of attempts to raise walleye fry and fingerlings on artifi- 
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Delong, Donald C, John E. Halver, and Edwin T. Mertz. 1958. Nutrition of salmonid 
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Fowler, L. G. 1973. Tests of three vitamin supplementation levels in the Abernathy diet. Pro- 
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Graff, Delano R. 1968. The successful feeding of a dry diet to esocids. Progressive Fish- 
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Hilton, J. W., C. Y. CjO, and S. J. Slinger. 1977. Factors affecting the stability of supple- 
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Horak, Donald. 197,5. Nutritional fish diseases and symptoms. Colorado Division of 
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Hurley, D. A., and E. L. Brannon. 1969. Effects of feeding before and after yolk absorption 
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Kra.MER, Chln and Mayo, Incorporated. 1976. Statewide fish hatchery program, Illinois, 
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Lek D. J., and G. B. PutN-iKM. 1973. The response of rainbow trout to varying protein/energy 
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LEiiRnz, Earl, and Robert C. Lewis. 1976. Trout and salmon culture (hatchery methods). 
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LoVELL, Tom. 1979. Diet, management, environment affect fish food consumption. Commer- 
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Nagel, Tim O. 1974. Rearing of walleye fingerlings in an intensive culture using Oregon 
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1976. Intensive culture of fingerling walleyes on formulated feeds. Progressive Fish- 
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1976. Rearing largemouth bass yearlings on artificial diets. Wildlife In-Service Note 

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National Research Council, Subcommittee on Fish Nutrition. 1973. Nutrient require- 
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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 
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Orme, Leo E. 1970. Trout feed formulation and development. Pages 172-192 in European In- 
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262 FISH HATCHERY MANAGEMENT 

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Page, Jimmy W., and James W. Andrews. 1973. Interactions of dietary levels of protein and 
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, Leslie A. Robinson, and Roger E. Burrows. 1951. Feeding frequency: its role in 

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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 
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Schmidt, P. J., and E. G. Baker. 1969. Indirect pigmentation of salmon and trout flesh with 
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Smith, R. R. 1971. A method for measuring digestibility and metabolizable energy of fish 
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Snow, J. R., and J. I. Maxwell. 1970. Oregon moist pellet as a production ration for large- 
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Spinelli, John, and Conrad Mahnken. 1976. Effect of diets containing dogfish [Squalus 
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Stickney, R. R., and R. T. Lovell. 1977. Nutrition and feeding of channel catfish. Southern 
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nel catfish of diets containing two energy and two protein levels. Transactions of the 
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TWONGO, Timothy K., and Hugh R. MacCrimmon. 1976. Significance of the timing of ini- 
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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 


•'^.^^ 


* 










# 


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% 


* 






# 




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V* 


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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 


().,') 





2.5 








(1) 


0.5 





2.5 


«i 


1.5 


(2) 


1.5 





2.5 


18 


4.5 


(3) 


0.5 





2.5 








(4) 


0.5 





2.5 


(') 


1.5 


(5) 


1.5 





2.5 


IK 


4.5 


(6) 


1.0 


12 





12 


3.0 


(7) 


0.75 


4 





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 



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TRANSPORTATION OF LIVE FISHES 369 

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Henegar, Dale L., and Donald C. Dlerre. 1964. Modified California fish distribution units 
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370 FISH HATCHERY MANAGEMENT 

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Llo^D, R. 1961. I'he toxicity of ammonia to rainbow trout. Water and Waste Treatment 
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TRANSPORTATION OF LIVE FISHES 371 

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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. 





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. 





1 


2 


3 


4 


5 


6 


7 


8 


9 







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>I<V SAI-MON IJ,I,I>S 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, <l.-li.il|.-fl 'Ml' IH.fVf.i 

VVIiciH rnul'lliii!//), ••)tiiii(l;)Mi 

WlM'iil ({f'rin iiK-id 

Vr'ii«t(, (lcliyr)r;it('<l brewer'* 

Hlo(,<l inei.l 'Ml' m:,j 

Wliey, (leliyrl/iilcfl 

Mil llll|/. ' .linHI ■/ MM'I ll<- irM'.ll 

({(ewei'h (<((ilir., d'liydi.i I'd 

Soyliejiii oil 

I'iiili 'III 

Vl(;iliiili I'l'lnl^ li'i ■" 

( IllllillC ' lll'll I'l' 

Mi;i(;rul jiu/Jui' 



it, 


.',1 


10 


10 


H.) 


\:i.4 


a 




r, 


ry 


r> 


5 


F) 


10 


r> 


T) 



10 



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 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 





0.05 


0.5 


B12 


mg 


0.005 


0.01 


0.01 


Choline 


mg 


200 


250 


1,500 


Folic acid 


mg 





2.3 


2.5 


Inositol 


mg 





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 





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 


2<i3.163 


1.7236 


6.292 


580.174 


3.880 


2.4944 


257.737 


1.7599 


6.336 


5fi8.211 


3.9(iO 


2.5114 


252.,530 


1.7962 


6.379 


556.732 


4.040 


2.5282 


247.529 


1.8325 


6.422 


545.708 


4.120 


2.5448 


242.723 


1.8688 


6.464 


535.112 


4.200 


2.5611 


238.100 


1 .9050 


6.505 


524.919 


4.280 


2.5773 


233.649 


1.9413 


6.546 


515.108 


4.360 


2.5933 


229.362 


1.9776 


6.587 


505.656 


4.440 


2.6090 


225.230 


2.0139 


6.627 


496.545 


4.520 


2.624(i 


221.243 


2.0.502 


6.666 


487.757 


4.600 


2.6400 


217.396 


2.0865 


6.706 


479.274 


4.()8() 


2.6552 


213.679 


2.1228 


6,744 


471,082 


4.7fiO 


2.6703 


210.088 


2.1591 


6.782 


463.164 


4.840 


2.6851 


206.616 


2.1953 


6.820 


455.509 


4.920 


2.6998 


203.2.56 


2.2316 


6.858 


448.102 


5.000 


2.7144 


200.000 


2.2680 


6.895 


440.924 


5.400 


2.78.50 


185.185 


2.4494 


7.074 


408.2(i3 


5.800 


2.8521 


172.414 


2.6308 


7.244 


380.107 


6.200 


2.9162 


161.290 


2.8123 


7.407 


355.584 


6.600 


2.9776 


151.515 


2.9937 


7. ,563 


334.034 


7.000 


3.0366 


142.857 


3.1751 


7.713 


314.946 


7.400 


3.0934 


135.135 


3.3566 


7.857 


297.922 


7.800 


3.1481 


128.205 


3.5380 


7.996 


282. (i44 



LENGTH-WEIGHT TABLES 



427 



T.^BLE 1-3. 


C= 2,.i00x 10 ' 


, CONTINUED 








WEIGHT/ 












1,000 


LENGTH 


FISH, 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


8.200 


3.2010 


121.951 


3.7194 


8.131 


268.856 


8.(K)0 


3.2.523 


116.279 


3.9009 


8.261 


256.3.52 


9.000 


3.3019 


111.111 


4.0823 


8.387 


244.958 


9.400 


3.3501 


106.383 


4.2638 


8.509 


234.535 


9.800 


3.3970 


102,041 


4.4452 


8.628 


224.962 


10.200 


3.4426 


98.039 


4.6266 


8.744 


216.140 


10.600 


3.4870 


94.340 


4.8081 


8.857 


207.984 


11.000 


3.5303 


90.909 


4.9895 


8.967 


200.421 


11.400 


3.5726 


87.720 


5.1709 


9.074 


193.388 


11.800 


3.6139 


84.746 


5.3524 


9.179 


186.833 


12.200 


3.6543 


81.967 


5.5338 


9.282 


180.707 


1 2.fi00 


3.6938 


79.365 


5.7152 


9.382 


174.970 


13.000 


3.7325 


76.923 


5.8967 


9.481 


169. .587 


13.400 


3.7704 


74.627 


6.0781 


9.577 


164.524 


13.800 


3.8075 


72.464 


6.2595 


9.671 


159.756 


14.200 


3.8440 


70.423 


6.4410 


9.764 


155.255 


14.600 


3.8797 


68.493 


6.6224 


9.855 


151.002 


15.000 


3.9149 


66.667 


6.8039 


9.944 


146.975 


15.400 


3.9494 


64.935 


6.9853 


10.031 


143.158 


15.800 


3.9833 


63.291 


7.1667 


10.117 


139.533 


16.200 


4.0166 


61.728 


7.3482 


10.202 


136.088 


16.600 


4.0494 


60.241 


7.5296 


10.285 


132.808 


17.000 


4.0817 


58.824 


7.7111 


10.367 


129.684 


17.400 


4.1134 


57.471 


7.8925 


10.448 


126.702 


17.800 


4.1447 


.56.180 


8.0739 


10.528 


123.855 


18.200 


4.1755 


54.945 


8.2554 


10.606 


121.133 


18.600 


4.2059 


53.764 


8.4368 


10.683 


118.528 


19.000 


4.2358 


52.632 


8.6182 


10.7.59 


116.033 


19.400 


4.2653 


51.546 


8.7997 


10.834 


113.640 


19.800 


4.2945 


50.505 


8.98 1 1 


10.908 


111.344 


2(),2()() 


4.3232 


49. ,505 


9.1625 


10.981 


109.140 


20.600 


4.3515 


48.544 


9.3440 


11.053 


107.021 


21.000 


4.3795 


47.619 


9.5254 


11.124 


104.982 


21.400 


4.4071 


46.729 


9.7069 


11.194 


103.020 


21.800 


4.4344 


45.872 


9.8883 


11.263 


101.129 


22.200 


4.4614 


45.045 


10.0697 


11.332 


99.307 


22.600 


4.4880 


44.248 


10.2512 


1 1 .400 


97.550 


23.000 


4.5144 


43.478 


10.4326 


11.466 


95.853 


23.400 


4.5404 


42.735 


10.6140 


11.533 


94.215 


23.800 


4.,5661 


42.017 


10.7955 


11.598 


92.631 


24.200 


4.,5915 


41.322 


10.9769 


11.662 


91.100 


24.600 


4.6167 


40.650 


11.1583 


11.726 


89.619 


25.000 


4.6416 


40.000 


11.3398 


11.790 


88.185 


25.800 


4.6906 


38.760 


11.7027 


11.914 


85.450 


26.600 


4.7386 


37.594 


12.0656 


12.036 


82.880 


27.400 


4.7856 


36.496 


12.4285 


1 2. 1 55 


80.460 



428 FISH HATCHERY MANAGEMENT 



Table 1-3. 


C = 2,.'')00x 10  


', CONTINUED 








WEIGHT/ 












1,(10(1 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


28.200 


4.8317 


35.461 


12.7913 


12.273 


78.178 


29.000 


4.8770 


34.483 


13.1542 


12.388 


76.021 


29.800 


4.9214 


33..557 


13.5171 


12.500 


73.980 


30.(i00 


4.965 1 


32.680 


13.8800 


12.611 


72.046 


31.400 


5.0080 


31.847 


14.2428 


12.720 


70.211 


32.200 


5.0502 


31.056 


14.6057 


12.827 


68.466 


33.000 


5.0916 


30.303 


14.9686 


12.933 


66.807 


33.800 


5.1325 


29.586 


15.3314 


13.036 


65.225 


34.600 


5.1726 


28.902 


15.6943 


13.138 


63.717 


35.400 


5.2122 


28.249 


16.0572 


13.239 


62.277 


36.200 


5.2512 


27.624 


16.4201 


13.338 


60.901 


37.000 


5.2896 


27.027 


16.7829 


13.436 


59.584 


37.800 


5.3274 


26.455 


17.1458 


13.532 


58.323 


38.600 


5.3647 


25.907 


17.5087 


13.626 


57.114 


39.400 


5.4016 


25.381 


17.8716 


13.720 


55.955 


40.200 


5.4379 


24.876 


18.2344 


13.812 


54.841 


41.000 


5.4737 


24.390 


18. ,5973 


13.903 


53.771 


41.800 


5..5091 


23.923 


18.9602 


13.993 


52.742 


42.600 


5.5440 


23.474 


19.3230 


14.082 


51.752 


43.400 


5.5785 


23.041 


19.6859 


14.169 


.50.798 


44.200 


5.6126 


22.624 


20.0488 


14.256 


49.878 


45.000 


5.6462 


22.222 


20.4117 


14.341 


48.991 


45.800 


5.6795 


21.834 


20.7745 


14.426 


48.136 


46.600 


5.7124 


21.459 


21.1374 


14.509 


47.309 


47.400 


5.7449 


21.097 


21.5003 


14.592 


46.511 


48.200 


5.7770 


20.747 


21.8632 


14.674 


45.739 


49.000 


5.8088 


20.408 


22.2260 


14.754 


44.992 


49.800 


5.8402 


20.080 


22.5889 


14.834 


44.269 


50.600 


5.8713 


19.763 


22.9518 


14.913 


43.570 


51.400 


5.9021 


19.455 


23.3147 


14.991 


42.891 


52.200 


5.9326 


19.157 


23.6775 


15.069 


42.234 


53.000 


5.9627 


18.868 


24.0404 


15.145 


41. ,597 


53.800 


5.9926 


18.587 


24.4033 


15.221 


40.978 


54.600 


6.0221 


18.315 


24.7661 


15.296 


40.378 


55.400 


6.0514 


18.051 


25.1290 


15.371 


39.795 


56.200 


6.0804 


17.794 


25.4919 


15.444 


39.228 


57.000 


6.1091 


17.544 


25.8548 


15.517 


38.677 


57.800 


6.1376 


17.301 


26.2176 


15.589 


38.142 


58.600 


6.1657 


17.065 


26.,5805 


15.661 


37.621 


59.400 


6.1937 


16.835 


26.9434 


15.732 


37.115 


60.200 


6.2214 


16.611 


27.3063 


15.802 


36.622 


61.000 


6.2488 


16.393 


27.6691 


15.872 


36.141 


61.800 


6.2760 


16.181 


28.0320 


15.941 


35.673 


62.600 


6.3030 


15.974 


28.3949 


16.010 


35.218 


63.400 


6.3297 


15.773 


28.7578 


16.077 


34.773 


64.200 


6.3562 


15.576 


29.1206 


16.145 


34.340 



LENGTH-WEIGHT TABLES 



429 



Table 1-3. 


C = 2„500 X 10 ' 


, CONTINUED 








WEIGHT/ 












1,000 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


USH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


65.000 


6.3825 


15.385 


29.4835 


16.212 


33.917 


65.800 


6.4086 


15.198 


29.8464 


16.278 


33.505 


66.600 


6.4344 


15.015 


30.2092 


16.343 


33.102 


67.400 


6.4601 


14.837 


30.5721 


16.409 


32.709 


68.200 


6.48.56 


14.663 


30.9350 


16.473 


32.326 


69.000 


6.5108 


14.493 


31.2979 


16.537 


31.951 


69.800 


6.5359 


14.327 


31.6607 


16.601 


31. ,585 


70.600 


6.5608 


14.164 


32.0236 


16.664 


31.227 


71.400 


6.5855 


14.006 


32.3865 


16.727 


30.877 


72.200 


6.6100 


13.8,50 


32.7494 


16.789 


30.,535 


73.000 


6.6343 


13.699 


33.1122 


16.851 


30.200 


73.800 


6.6584 


13.5,50 


33.4751 


16.912 


29.873 


74.600 


6.6824 


13.405 


33.8380 


16.973 


29.553 


75.400 


6.7062 


13.263 


34.2009 


17.034 


29.239 


76.200 


6.7298 


13.123 


34. ,5637 


17.094 


28.932 


77.000 


6.7533 


12.987 


34.9266 


17.153 


28.631 


77.800 


6.7766 


12.853 


35.2895 


17.213 


28.337 


78.600 


6.7998 


12.723 


35.6523 


17.271 


28.049 


79.400 


6.8228 


12. ,594 


36.0152 


17.330 


27.766 


80.200 


6.8456 


12.469 


36.3781 


17.388 


27.489 


81.000 


6.8683 


12.346 


36.7410 


17.445 


27.217 


81.800 


6.8908 


12.225 


37.1038 


17., 503 


26.951 


82.600 


6.9132 


12.107 


37.4667 


17.. 560 


26.690 


83.400 


6.9355 


11.990 


37.8296 


17.616 


26.434 


84.200 


6.9576 


11.876 


38.1925 


17.672 


26.183 


85.000 


6.9795 


11.765 


38.5553 


17.728 


25.937 


85.800 


7.0014 


11.655 


38.!)182 


17.783 


25.695 


86.600 


7.0231 


11.547 


39.2811 


17.839 


25.457 


87.400 


7.0446 


11.442 


39.6440 


17.893 


25.224 


88.200 


7.0660 


11.338 


40.0068 


17.948 


24.996 


89.000 


7.0873 


11.236 


40.3697 


18.002 


24.771 


89.800 


7.1085 


11.136 


40.7326 


18.056 


24.550 


90.600 


7.1296 


11.038 


41.0955 


18.109 


24.334 


91.400 


7.1,505 


10.941 


41.4583 


18.162 


24.121 


92.200 


7.1713 


10.846 


41,8212 


18.215 


23.911 


93.000 


7.1920 


10.753 


42.1841 


18.268 


23.706 


93.800 


7.2125 


10.(i61 


42.5470 


18.320 


23..503 


94.600 


7.2330 


10.571 


42.9098 


18.372 


23.305 


95.400 


7.2.533 


10.482 


43.2727 


18.423 


23.109 


96.200 


7.2735 


10.395 


43.63,56 


18.475 


22.917 


97.000 


7.2936 


10.309 


43,9984 


18..526 


22.728 


97.800 


7.3136 


10.225 


44.3613 


18.577 


22.542 


98.600 


7.3335 


10.142 


44.7242 


18.627 


22.359 


99.400 


7.3533 


10.060 


45.0871 


18.677 


22.179 


102.000 


7.4169 


9.804 


46.2664 


18.839 


21.614 


110.000 


7.6059 


9.091 


49.8951 


19.319 


20.042 



430 FISH HATCHERY MANAGEMKNT 



-7 



Table 1-3. c = :2,.woxio '.continued 



WEIGHT/ 












1,00(1 


LKNtiTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


IIH.OOO 


7.78(iO 


8.475 


53.5238 


19.776 


18.()83 


I'ifi.OOO 


7.9581 


7.937 


57.1526 


20.214 


17.497 


i;-i4.()()() 


8,1231 


7.463 


60.7813 


20.633 


16.452 


142.000 


8.2816 


7.042 


64.4100 


2 1 .035 


15.525 


1,''>0.000 


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<i4 


2212.400 


0.2050 


2.912 


4877.500 


0.456 


1.1498 


2192.993 


0.2068 


2.920 


4834.715 


0.460 


1.1531 


2173.923 


0.2087 


2.929 


4792.672 


0.464 


1.1565 


2155.183 


0.2105 


2.937 


4751.355 


0.468 


1.1598 


2136.763 


0.2123 


2.946 


4710.746 


0.472 


1.1631 


2181.655 


0.2141 


2.954 


4670.828 


0.476 


1.1663 


2100.851 


0.21,59 


2.963 


4631.574 


0.480 


1.1696 


2083.344 


0.2177 


2.971 


4592.980 



432 FISH HATCHKRY MANAGEMENT 

Table 1-4. c = 3,000 x 10^'', con iinued 



WEIGHT/ 












1,000 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


0.484 


1.1728 


206(i.l26 


0.2195 


2.979 


4555.023 


0.488 


1.1761 


2049.191 


0.2214 


2.987 


4517.688 


0,492 


1 . 1 793 


2032.531 


0.2232 


2.995 


4480.957 


0,49(i 


1 . 1 825 


2016.140 


0.2250 


3.003 


4444.820 


0.500 


1.18,56 


2000.000 


0.2268 


3.012 


4409.238 


0.508 


1.1919 


1968. .504 


0.2304 


3.027 


4339.801 


0.5 Hi 


1.1981 


1937.985 


0.2341 


3.043 


4272.520 


0,524 


1.2043 


1908.398 


0.2377 


3.059 


4207.289 


0,532 


1.2104 


1879.701 


0.2413 


3.074 


4144.023 


0,540 


1.2164 


1851.854 


0.2449 


3.090 


4082.633 


0„548 


1.2224 


1824.819 


0.2486 


3.105 


4023.033 


0,.556 


1.2283 


1798.563 


0.2522 


3.120 


3965.149 


0,564 


1.2342 


1773.052 


0.2558 


3.135 


3908. 90() 


0.572 


1.2400 


1748.254 


0.2595 


3.1,50 


3854.237 


0,580 


1.2458 


1724.141 


0.2631 


3.164 


3801.075 


0,588 


1.2515 


1700.683 


0.2667 


3.179 


3749.361 


0.,596 


1 .257 1 


1677.8,56 


0.2703 


3.193 


3699.034 


0,604 


1.2627 


1655.633 


0.2740 


3.207 


36,50.041 


0,612 


1.2683 


1633.991 


0.2776 


3.221 


3602,328 


0,620 


1.2738 


1612.907 


0.2812 


3.235 


35,5,5.847 


0,628 


1.2792 


1,592.361 


0.2849 


3.249 


3510.5.50 


0.636 


1.2846 


1572.331 


0.2885 


3.263 


3466.393 


0,644 


1.2900 


1.552.799 


0.2921 


3.277 


3423.333 


0,652 


1.29,53 


1533.747 


0.29.57 


3.290 


3381.329 


0,660 


1.3006 


151,5.156 


0.2994 


3.303 


3340.344 


0.668 


1.3058 


1497.011 


0.3030 


3.317 


3300.340 


0,67(i 


1.3110 


1479.295 


0.3066 


3.330 


3261.283 


0,684 


1.3162 


1 46 1 .993 


0.3103 


3.343 


3223.139 


0,692 


1.3213 


1445.092 


0.3139 


3.3,56 


3185.878 


0,700 


1.3264 


1428.577 


0.3175 


3.369 


3149.469 


0,708 


1.3314 


1412.435 


0.3211 


3.382 


3113.882 


0.716 


1.3364 


1396.653 


0.3248 


3.394 


3079.090 


0,724 


1.3413 


1381.221 


0.3284 


3.407 


3045.067 


0,732 


1.3463 


1366.126 


0.3320 


3.420 


3011.788 


0.740 


1.3,511 


1351.357 


0.3357 


3.432 


2979.228 


0.748 


1.3.560 


1336.904 


0.3393 


3.444 


2947.36,5 


0.756 


1.3608 


1322.757 


0.3429 


3.456 


2916.177 


().7(i4 


1.3656 


1308.906 


0.3465 


3.469 


2885.641 


0.772 


1.3703 


1295.343 


0.3502 


3.481 


2855.738 


0.780 


1.3751 


1282.057 


0.3,538 


3.493 


2826.449 


0.788 


1.3798 


1269.042 


0.3574 


3. .505 


2797.754 


0.796 


1.3844 


1256.287 


0.3611 


3.516 


2769.(i3(J 


0.804 


1.3890 


1243.787 


0.3647 


3.528 


2742.078 


0.812 


1.3936 


1231.533 


0.3683 


3.540 


2715.063 


0.820 


1.3982 


1219.518 


0.3719 


3.551 


2688.574 


0.828 


1.4027 


1207.736 


0.37.56 


3..563 


2662.598 



LENGTH-WEIGHT TABLES 



433 



Table 1-4. 


C = 3,000 X 10 


% CONTINUED 








WEIGHT/ 












1.000 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


0.836 


1.4072 


1196.178 


0.3792 


3.574 


2637.119 


0.844 


1.4117 


1184.840 


0.3828 


3.586 


2612.123 


0.852 


1.4161 


1173.715 


0.3865 


3.597 


2587.596 


0.860 


1.4206 


1162.797 


0.3901 


3.608 


2563.525 


0.868 


1.4249 


1152.080 


0.3937 


3.619 


2539.898 


0.876 


1.4293 


1141.5.59 


0.3973 


3.630 


2516.703 


0.884 


1.4336 


1131.228 


0.4010 


3.641 


2493.928 


0.892 


1.4380 


1121.083 


0.4046 


3.6.52 


2471. .561 


0.900 


1.4422 


1111.117 


0.4082 


3.663 


2449.592 


0.908 


1.4465 


1101.328 


0.4119 


3.674 


2428.009 


0.916 


1.4507 


1091.709 


0.4155 


3.685 


2406.804 


0.924 


1.4550 


1082.257 


0.4191 


3.696 


2385.966 


0.932 


1.4591 


1072.968 


0.4227 


3.706 


2365.486 


0.940 


1.4633 


1063.836 


0.4264 


3.717 


2345.354 


0.948 


1.4674 


1054.859 


0.4300 


3.727 


2325.,563 


0.956 


1.4716 


1046.031 


0.4336 


3.738 


2306.102 


0.964 


1.4757 


1037.351 


0.4373 


3.748 


2286.964 


0.972 


1.4797 


1028.813 


0.4409 


3.758 


2268.142 


0.980 


1.4838 


1020.415 


0.4445 


3.769 


2249.626 


0.988 


1.4878 


1012.152 


0.4481 


3.779 


2231.411 


0.996 


1.4918 


1004.022 


0.4518 


3.789 


2213.488 


1.040 


1.5135 


961.539 


0.4717 


3.844 


2119.829 


1.120 


1.5513 


892.859 


0.5080 


3.940 


1968.416 


1.200 


1.5874 


833.337 


0.5443 


4.032 


1837.191 


1.280 


1.6219 


781.2.54 


0.5806 


4.120 


1722.368 


1.360 


1.6550 


735.299 


0.6169 


4.204 


1621.0.54 


1.440 


1.6869 


694.449 


0.6532 


4.285 


1530.998 


1.520 


1.7175 


657.900 


0.6895 


4.363 


1450.420 


1.600 


1.7472 


625.006 


0.7257 


4.438 


1377.900 


1.680 


1.7758 


595.244 


0.7620 


4.511 


1312.287 


1.760 


1.8036 


.568.188 


0.7983 


4.581 


12.52.638 


1.840 


1.8305 


543.484 


0.8346 


4.649 


1198.177 


1.920 


1.8566 


520.839 


0.8709 


4.716 


1148.2.53 


2.000 


1.8821 


500.006 


0.9072 


4.780 


1102.323 


2.080 


1.9068 


480.775 


0.9435 


4.843 


10.59.927 


2.160 


1.9310 


462.969 


0.9797 


4.095 


1020.671 


2.240 


1.9545 


446.435 


1.0160 


4.964 


984.219 


2.320 


1.9775 


43 1 .04 1 


1.0523 


5.023 


9.50.281 


2.400 


2.0000 


416.673 


1.0886 


5.080 


918.605 


2.480 


2.0220 


403.232 


1.1249 


5.136 


888.973 


2.560 


2.0435 


390.631 


1.1612 


5.190 


861.193 


2.640 


2.0645 


378.794 


1.1975 


5.244 


835.096 


2.720 


2.0852 


367.653 


1.2338 


5.296 


810..535 


2.800 


2.1054 


357.148 


1.2700 


5.348 


787.377 


2.880 


2.1253 


347.228 


1.3063 


5.398 


765..505 


2.960 


2.1448 


337.843 


1.3426 


5.448 


744.816 



434 



FISH HATCHERY MANAGEMENT 



Table 1-4. 


C = 3,000 X 10 ' 


', CONTINUED 








WEIGHT/ 












1,0(10 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


3.040 


2.1640 


328.953 


1.3789 


5.496 


725.216 


3.120 


2.1828 


320.518 


1.4152 


5.544 


706.621 


3.200 


2.2013 


312.,505 


1.4515 


5., 591 


688.955 


3.280 


2.2195 


304.883 


1.4878 


5.637 


672.152 


3.360 


2.2374 


297.624 


1.5240 


5.683 


656.148 


3.440 


2.2550 


290.703 


1.5603 


5.728 


640.889 


3.520 


2.2723 


284.096 


1.5966 


5.772 


626.323 


3.600 


2.2894 


277.783 


1.6329 


5.815 


612.405 


3.680 


2.3062 


271.744 


1.6692 


5.858 


599.092 


3.760 


2.3228 


265.962 


1.7055 


5.900 


586.346 


3.840 


2.3392 


260.421 


1.7418 


5.942 


574.130 


3.920 


2.3553 


255.107 


1.7780 


5.983 


562.413 


4.000 


2.3712 


250.005 


1.8143 


6.023 


551.165 


4.080 


2.3870 


245.103 


1 .8506 


6.063 


540.358 


4.160 


2.4025 


240.389 


1.886!) 


6.102 


529.967 


4.240 


2.4178 


235.854 


1.9232 


6.141 


519.967 


4.320 


2.4329 


231.486 


1 .9595 


6.179 


510.338 


4.400 


2.4478 


227.277 


1.9958 


6.217 


501.060 


4.480 


2.4625 


223.219 


2.0321 


6.255 


492.112 


4.560 


2.4771 


219.302 


2.0683 


6.292 


483.479 


4.640 


2.4915 


215.521 


2.1046 


6.328 


475.143 


4.720 


2.5057 


211.869 


2.1409 


6.365 


467.090 


4.800 


2.5198 


208.337 


2.1772 


6.400 


459.305 


4.880 


2.5337 


204.922 


2.2135 


6.436 


451.775 


4.960 


2.5475 


201.617 


2.2498 


6.471 


444.489 


5.200 


2.5880 


192.308 


2.3587 


6.573 


423.965 


5.600 


2.6527 


178.572 


2.5401 


6.738 


393.682 


6.000 


2.7144 


166.667 


2.7215 


6.895 


367.437 


6.400 


2.7734 


156.2.50 


2.9030 


7,045 


344.472 


6.800 


2.8301 


147.059 


3.0844 


7,188 


324,209 


7.200 


2.8845 


138.889 


3.2659 


7.327 


306.198 


7.600 


2.9370 


131.579 


3.4473 


7.460 


290.082 


8.000 


2.9876 


125.000 


3.6287 


7.589 


275.578 


8.400 


3.0366 


119.048 


3.8102 


7.713 


262.455 


8.800 


3.0840 


113.637 


3.99 Hi 


7.833 


250.526 


9.200 


3.1301 


108.696 


4.1730 


7.950 


239.633 


9.600 


3.1748 


104.167 


4.3545 


8.064 


229.649 


10.000 


3.2183 


100.000 


4.5359 


8.174 


220.463 


10.400 


3.2606 


96.154 


4.7173 


8.282 


211.983 


10.800 


3.3019 


92.593 


4.8988 


8,387 


204.132 


11.200 


3.3422 


89.286 


5.0802 


8.489 


196.842 


11.600 


3.3815 


86.207 


5.2616 


8.589 


190.054 


12.000 


3.4199 


83.334 


5.4431 


8.687 


183.719 


12.400 


3.4575 


80.645 


5.6245 


8.782 


177.793 


12.800 


3.4943 


78.125 


5,8060 


8.876 


172.237 


13.200 


3.5303 


75.758 


5.9874 


8.967 


167.017 



LENGTH-WEIGHT TABLES 



435 



Table 1-4. 


C= 3,000 X 10 ' 


, CONTINUED 








WEIGHT/ 












1,000 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


13.600 


3.5656 


73.530 


6.1688 


9.057 


162.105 


14.000 


3.fi003 


71.429 


6.3503 


9.145 


157.473 


14.400 


3.6342 


(i9.445 


6.5317 


9.231 


1.53.099 


14.800 


3.6676 


67.568 


6.7131 


9.316 


148.961 


15.200 


3.7003 


65.790 


6.8946 


9.399 


145.041 


15.600 


3.7325 


64.103 


7.0760 


9.481 


141.322 


16.000 


3.7641 


62.500 


7.2574 


9.561 


137.789 


16.400 


3.7953 


60.976 


7.4389 


9.640 


134.428 


16.800 


3.8259 


59..524 


7.6203 


9.718 


131.227 


17.200 


3.8560 


58.140 


7.8018 


9.794 


128.176 


17.600 


3.8856 


56.818 


7.9832 


9.870 


125.263 


18.000 


3.9149 


r)5.riri6 


8.1646 


9.944 


122.479 


18.400 


3.9437 


54.348 


8.3461 


10.017 


119.816 


18.800 


3.9720 


53.192 


8.5275 


10.089 


117.267 


19.200 


4.0000 


52.083 


8.7090 


10.160 


114.824 


19.600 


4.0276 


51.020 


8.8904 


10.230 


112.481 


20.000 


4.0548 


50.000 


9.0718 


10.299 


110.231 


20.400 


4.0817 


49.020 


9.2533 


10.367 


108.070 


20.800 


4.1082 


48.077 


9.4347 


10.435 


105.991 


21.200 


4.1343 


47.170 


9.6161 


10.501 


103.992 


21.600 


4.1602 


46.296 


9.7976 


10.567 


102.06fi 


22.000 


4.1857 


45.455 


9.9790 


10.632 


100.210 


22.400 


4.2109 


44.643 


10.1604 


10.696 


98.421 


22.800 


4.2358 


43.860 


10.3419 


10.759 


96.694 


23.200 


4.2604 


43.103 


10.5233 


10.822 


95.027 


23.600 


4.2848 


42.373 


10.7048 


10.883 


93.416 


24.000 


4.3089 


41.667 


10.8862 


10.945 


91.8,59 


24.400 


4.3327 


40.984 


11.0676 


1 1 .005 


90.353 


24.800 


4.3562 


40.323 


11.2491 


1 1 .065 


88.896 


25.400 


4.3911 


39.370 


11.5213 


11.153 


86.796 


26.200 


4.4367 


38.168 


11.8841 


11.269 


84.146 


27.000 


4.4814 


37.037 


12.2470 


11.383 


81.6.52 


27.800 


4.5252 


35.971 


12.6099 


11.494 


79.303 


28.600 


4..5682 


34.965 


12.9728 


11.603 


77.084 


29.400 


4.6104 


34.014 


13.3356 


11.711 


74.987 


30.200 


4.6519 


33.112 


13.6985 


11.816 


73.000 


31.000 


4.6926 


32.258 


14.0614 


11.919 


71.117 


31.800 


4.7326 


31.446 


14.4243 


12.021 


69.327 


32.600 


4.7720 


30.675 


14.7871 


12.121 


67.626 


33.400 


4.8107 


29.940 


15.1500 


12.219 


66.006 


34.200 


4.8488 


29.240 


15.5129 


12.316 


64.462 


35.000 


4.8863 


28.571 


15.8758 


12.411 


62.989 


35.800 


4.9233 


27.933 


16.2386 


12..505 


61.581 


36.600 


4.9597 


27.322 


16.6015 


12..598 


60.235 


37.400 


4.9956 


26.738 


16.9644 


12.689 


58.947 


38.200 


5.0309 


26.178 


17.3272 


12.779 


57.712 



436 



FI.SH HATCHERY MANAGEMENT 



Table 1-4. 


C = 3,000 X 10 


\ CONTINUED 








WEIGHT/ 












1.(100 


I.KNGTH 


FISH/ 


WEIGHT 


LENGTH 


KI.SH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


39.()()() 


5.0658 


25.641 


17.6901 


12.867 


56.529 


39.800 


5.1002 


25.126 


18.0530 


12.955 


55.392 


40.fi00 


5.1341 


24.630 


18.41,59 


13.041 


,54.301 


41.400 


5.1676 


24. 1 55 


18.7787 


13.126 


53.252 


42.200 


5.2007 


23.697 


19.1416 


13.210 


52.242 


43.000 


5.2334 


23.2.56 


19.,5045 


13.293 


51.270 


43.800 


5.2656 


22.831 


19.8674 


13.375 


50.334 


44.600 


5.2975 


22.421 


20.2302 


13.4.56 


49.431 


45.400 


5.3290 


22.026 


20.5931 


13.536 


48. .560 


46.200 


5.3601 


21.645 


20.9560 


13.615 


47.719 


47.000 


5.3909 


21.277 


21.3188 


13.693 


46.907 


47.800 


5.4213 


20.920 


21.6817 


13.770 


46.122 


48.600 


5.4514 


20.576 


22.0446 


13.846 


45.362 


49.400 


5.4811 


20.243 


22.4075 


13.922 


44.628 


50.200 


5.5105 


19.920 


22.7703 


13.997 


43.917 


51.000 


5.5397 


19.608 


23.1332 


14.071 


43.228 


51.800 


5.-5685 


19.305 


23.4961 


14.144 


42.560 


52.600 


5.,5970 


19.011 


23.8590 


14.216 


41.913 


53.400 


5.6252 


18.727 


24.2218 


14.288 


41.285 


54.200 


5.6532 


18.450 


24.5847 


14.359 


40.676 


55.000 


5.6809 


18.182 


24.9476 


14.429 


40.084 


55.800 


5.7083 


17.921 


25.3105 


14.499 


39.509 


56.600 


5.73,54 


17.668 


25.6733 


14. ,568 


38.951 


57.400 


5.7623 


17.422 


26.0362 


14.636 


38.408 


58.200 


5.7890 


17.182 


26.3991 


14.704 


37.880 


59.000 


5.8154 


16.949 


26.7619 


14.771 


37.366 


59.800 


5.8415 


16.722 


27.1248 


14.837 


36.867 


60.600 


5.8675 


16.502 


27.4877 


14.903 


36.380 


61.400 


5.8932 


16.287 


27.8,506 


14.969 


35.906 


62.200 


5.9187 


16.077 


28.2134 


15.033 


35.444 


63.000 


5.9439 


15.873 


28.5763 


15.098 


34.994 


63.800 


5.9690 


15.674 


28.9392 


15.161 


34.555 


64.600 


5.9938 


15.480 


29.3021 


15.224 


34.127 


65.400 


6.0185 


15.291 


29.6649 


15.287 


33.710 


66.200 


6.0429 


15.106 


30.0278 


15.349 


33.302 


67.000 


6.0671 


14.925 


30.3907 


15.411 


32.905 


67.800 


6.0912 


14.749 


30.7536 


15.472 


32.516 


68.600 


6.1151 


14.577 


31.1164 


15.532 


32.137 


69.400 


6.1387 


14.409 


31.4793 


15.592 


31.767 


70.200 


6.1622 


14.245 


31.8422 


15.652 


31.405 


71.000 


6.18,56 


14.084 


32.20,50 


15.711 


3 1 .05 1 


71.800 


6.2087 


13.928 


32.5679 


15.770 


30.705 


72.600 


6.2317 


13.774 


32.9308 


15.828 


30.367 


73.400 


6.2,545 


13.624 


33.2937 


15.886 


30.036 


74.200 


6.2771 


13.477 


33.6566 


15.944 


29.712 


75.000 


6.2996 


13.333 


34.0194 


16.001 


29.395 



LENGTH-WEIGHT TABLES 



437 



Table 1-4. 


C = 3,000 X 10 ' 


' , CONTINUED 








WEIGHT/ 












1,000 


LENGTH 


FISH/ 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


75.800 


6.3219 


13.193 


34.3823 


16.0.58 


29.085 


76.600 


6.3441 


13.055 


34.74.'')2 


16.114 


28.781 


77.400 


6.3661 


12.920 


35.1080 


16.170 


28.483 


78.200 


6.3880 


12.788 


35.4709 


16.225 


28.192 


79.000 


6.4097 


12.658 


35.8338 


16.281 


27.907 


79.800 


6.4312 


12..531 


36.1967 


16.335 


27.627 


80.600 


6.4526 


12.407 


36.5595 


16.390 


27.353 


81.400 


6.4739 


12.285 


36.9224 


16.444 


27.084 


82.200 


6.4951 


12.165 


37.2853 


16.497 


26.820 


83.000 


6.5161 


12.048 


37.6481 


16.551 


26.562 


83.800 


6.5369 


11.933 


38.0110 


16.604 


26.308 


84.600 


6.5577 


11.820 


38.3739 


16.6.56 


26.059 


85.400 


6.5783 


11.710 


38.7368 


16.709 


25.815 


86.200 


6.5988 


11.601 


39.0997 


16.761 


25.576 


87.000 


6.6191 


11.494 


39.4625 


16.813 


25.340 


87.800 


6.6393 


11.390 


39.8254 


16.864 


25.110 


88.600 


6.6594 


11.287 


40.1883 


16.915 


24.883 


89.400 


6.6794 


11.186 


40.5511 


16.966 


24.660 


90.200 


6.6993 


1 1 .086 


40.9140 


17.016 


24.441 


91.000 


6.7190 


10.989 


41.2769 


17.066 


24.227 


91.800 


6.7387 


10.893 


41.6398 


17.116 


24.015 


92.600 


6.7582 


10.799 


42.0026 


17.166 


23.808 


93.400 


6.7776 


10.707 


42.3655 


17.215 


23.604 


94.200 


6.7969 


10.616 


42.7284 


17.264 


23.404 


95.000 


6.8161 


10.526 


43.0912 


17.313 


23.206 


95.800 


6.8351 


10.438 


43.4541 


17.361 


23.013 


96.600 


6.8541 


10.352 


43.8170 


17.409 


22.822 


97.400 


6.8730 


10.267 


44.1799 


17.457 


22.635 


98.200 


6.8918 


10.183 


44.5427 


17. .505 


22.4,50 


99.000 


6.9104 


10.101 


44.9056 


17..5.52 


22.269 


99.800 


6.9290 


10.020 


45.2685 


17.600 


22.090 


106.000 


7.0696 


9.434 


48.0807 


17.957 


20.798 


114.000 


7.2432 


8.772 


51.7095 


18.398 


19.339 


122.000 


7.4088 


8.197 


55.3382 


18.818 


18.071 


130.000 


7. ,5673 


7.692 


58.9669 


19.221 


16.9.59 


138.000 


7.7194 


7.246 


62..5957 


19.607 


15.976 


146.000 


7.8658 


6.849 


66.2244 


19.979 


15.100 


154.000 


8.0069 


6.494 


69.8531 


20.338 


14.316 


162.000 


8.1432 


6.173 


73.4819 


20.684 


13.609 


170.000 


8.2751 


5.882 


77.1106 


21.019 


12.968 


178.000 


8.4030 


5.618 


80.7394 


21.344 


12.386 


186.000 


8.5270 


5.376 


84.3681 


21.6.59 


11.8,53 


194.000 


8.6475 


5.155 


87.9968 


21.965 


11.364 


202.000 


8.7648 


4.950 


91.6256 


22.263 


10.914 


210.000 


8.8790 


4.762 


95.2543 


22.553 


10.498 


218.000 


8.9904 


4.587 


98.8830 


22.836 


10.113 



438 FISH HATCHERY MANAGEMENT 



Tabik I- 1. 


C = 3,000 X 10 ' 


', CONTINUED 








WIJC.ll 1, 












1,(1110 


l.F-.NUTH 


FISH,' 


vvFi(;Hr 


LENGTH 


KI.SH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


22(). ()()() 


!).()!)!)0 


4.425 


102.51 18 


23.1 12 


<).755 


234.000 


9.2052 


4.274 


10(i.l4()5 


23.381 


9.421 


242.000 


9.3089 


4.132 


l()9.7fi!)2 


23.645 


9.110 


2,'')().0()() 


9.4104 


4.000 


113.3980 


23.902 


8.818 


2.')8.()()() 


9.5097 


3.87f) 


117.02fi7 


24.155 


8.545 


2(ifi.OOO 


9.(i()7() 


3.759 


12().(i555 


24.402 


8.288 


274.000 


9.7023 


3.f)50 


124.2842 


24.644 


8.046 


282.000 


9.7959 


3.546 


127.9129 


24.881 


7.818 


2iH).()()() 


9.887fi 


3.448 


131.5417 


25.115 


7.602 


298.000 


9.9777 


3.35rt 


135.1704 


25.343 


7.398 



LENGTH-WEIGHT TABLES 439 

Table 1-5. length-weight relationships for fish with c = 3,500 x io~^ 



WEIGHT/ 












1,0(10 


length 


FISH/ 


weight 


LFNGI II 


fish 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS! 


CM 


kilogram 


0.350 


1.0000 


2857.145 


0.1588 


2.540 


6298.914 


0.354 


1.0038 


2824.861 


0.1606 


2.5.50 


6227.742 


0.358 


1.0076 


2793.298 


0.1624 


2.559 


6158.160 


0.362 


1.0113 


2762.434 


0.1642 


2.569 


6090. 1 1 3 


0.3(i(i 


1.0 !.')() 


2732.243 


0.1660 


2.578 


6023.555 


0.370 


1.0187 


27()2.7()(i 


().lfi78 


2.587 


5958.438 


0.374 


1.0224 


2673.800 


().169fi 


2.597 


,5894.7 1 1 


0.378 


1.02()() 


2645. ,507 


0.1715 


2.606 


5832.336 


0.382 


1.0296 


2617.805 


0.1733 


2.615 


5771.266 


0.38() 


1.0332 


2590.(i78 


0.1751 


2.624 


5711.457 


0.390 


1.0367 


2564.107 


0.1769 


2.633 


5652.879 


0.394 


1 .0403 


2538.076 


0.1787 


2.642 


5595.492 


0.398 


1.0438 


2512.5()8 


0.1805 


2.651 


5539.254 


0.402 


1.0473 


2487. 5(i8 


0.1823 


2.r)60 


5484.141 


0.4()() 


1 .0507 


2463.0()0 


0.1842 


2.669 


5430.109 


0.410 


1 .0542 


2439.030 


0.1860 


2.678 


5377.133 


0.414 


1.0576 


2415.465 


0.1878 


2.686 


5325.180 


0.418 


1.0610 


2392.351 


0.1896 


2.695 


5274.223 


0.422 


1.0643 


2369.675 


0.1914 


2.703 


5224.230 


0.42(i 


1.0677 


2347.424 


0.1932 


2.712 


5175.176 


0.430 


1.0710 


2325.588 


0.1950 


2.720 


5127.035 


0.434 


1.0743 


2304.154 


0.1969 


2.729 


5079.781 


0.438 


1.0776 


2283.112 


0.1987 


2.737 


.5033.391 


0.422 


1.0809 


2262.4.50 


0.2005 


2.745 


4987.840 


0.44(1 


1.0841 


2242.160 


0.2023 


2.754 


4943.109 


0.450 


1.0874 


2222.229 


0.2041 


2.762 


4899.168 


0.454 


1.0906 


2202.651 


0.2059 


2.770 


4856.004 


0.458 


1.0938 


2183.414 


0.2077 


2.778 


4813.594 


0.462 


1.0970 


21(i4.510 


0.2096 


2.786 


4771.918 


0.466 


1.1001 


2145.930 


0.2114 


2.794 


4730.9()1 


0.470 


1.1033 


2127.667 


0.2132 


2.802 


4690.695 


0.474 


1.1064 


2109.713 


0.2150 


2.810 


4(i5 1.113 


0.478 


1.1095 


2092.058 


0.2168 


2.818 


4612.191 


0.482 


1.1126 


2074.697 


0.2186 


2.826 


4573.918 


0.486 


1.11 56 


2()57.(i21 


0.2204 


2.834 


4536.270 


().4!)0 


1.1187 


2040.825 


0.2223 


2.841 


4499.242 


0.4<)4 


1.1217 


2024.300 


0.2241 


2.849 


4462.809 


().4!)8 


1.1247 


2008.041 


0.2259 


2.857 


4426.965 


0.504 


1.1292 


1984.127 


0.2286 


2.8()8 


4374.246 


0.5 1 2 


1.1352 


1953.125 


0.2322 


2.883 


4305.898 


0.520 


1.1411 


1923.078 


0.2359 


2.8!)8 


4239.652 


0.528 


1.1469 


1893.941 


().23!)5 


2.913 


4175.418 


0.53(i 


1.1527 


18(i5.(i73 


0.2431 


2.928 


4113.098 


0.544 


1 . 1 584 


1838.237 


0.2468 


2.942 


4052.r)14 


0.552 


1.1640 


1811.596 


0.2504 


2.957 


3993.881 


0.560 


1.1696 


1785.717 


0.2540 


2.971 


3936.826 



440 FISH HATCHERY MANAGEMENT 

Table 1-5. c = 3,.')()o x lo"'^, continued 



WEIGHT/ 












1,000 


LENGTH 


FISH/ 


v\i.i(,n 1 


i,KNc;rn 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


0.568 


1.1751 


17()().5()6 


0.2576 


2.985 


3881.379 


0.576 


1.1806 


1736.114 


0.2613 


2.999 


3827.471 


0.584 


1.1861 


1712.332 


0.2649 


3.013 


3775.041 


0.5i)2 


1.1915 


1689.192 


0.2685 


3.026 


3724.027 


0.600 


1.1968 


166(i.670 


0.2722 


3.040 


3674.374 


0.608 


1.2021 


1644.740 


0.2758 


3.053 


3626.028 


0.616 


1.2074 


1623.380 


0.2794 


3.067 


3578.937 


0.624 


1.2126 


1602.568 


0.2830 


3.080 


3533.053 


0.632 


1.2177 


1582.283 


0.2867 


3.093 


3488.332 


0.640 


1.2228 


1562.504 


0.2903 


3.106 


3444.728 


0.648 


1.2279 


1.543.214 


0.2939 


3.119 


3402.201 


0.656 


1.2329 


1524.395 


0.2976 


3.132 


3360.711 


0.664 


1.2379 


1506.029 


0.3012 


3.144 


3320.221 


0.672 


1.2429 


1488.100 


0.3048 


3.157 


3280.695 


0.680 


1.2478 


1470.593 


0.3084 


3.169 


3242.099 


0.688 


1.2,527 


1453.493 


0.3121 


3.182 


3204.400 


0.696 


1 .2575 


1436.787 


0.3157 


3.194 


3 167., 569 


0.704 


1.2623 


1420.460 


0.3193 


3.206 


3131.574 


0.712 


1.2671 


1404.500 


0.3230 


3.218 


3096.388 


0.720 


1.2718 


1388.894 


0.3266 


3.230 


3061.984 


0.728 


1.2765 


1373.632 


0.3302 


3.242 


3028.336 


0.736 


1.2812 


1358.701 


0.3338 


3.2.54 


2995.420 


0.744 


1.2858 


1344.092 


0.3375 


3.266 


2963.211 


0.752 


1.2904 


1329.793 


0.3411 


3.278 


2931.688 


0.760 


1.2949 


1315.795 


0.3447 


3.289 


2900.828 


0.768 


1.2995 


1302.089 


0.3484 


3.301 


2870.612 


0.776 


1.3040 


1288.666 


0.3520 


3.312 


2841.018 


0.784 


1.3084 


1275.516 


0.3556 


3.323 


2812.028 


0.792 


1.3129 


1262.632 


0.3592 


3.335 


2783.624 


0.800 


1.3173 


12.50.006 


0.3629 


3.346 


27,55.788 


0.808 


1.3216 


1237.630 


0.3665 


3.357 


2728. ,503 


0.816 


1.3260 


1225.496 


0.3701 


3.368 


2701.753 


0.824 


1.3303 


1213.,598 


0.3738 


3.379 


2675.523 


0.832 


1.3346 


1201.929 


0.3774 


3.390 


2649.75)7 


0.840 


1.3389 


1190.482 


0.3810 


3.401 


2624.561 


0.848 


1.3431 


1179.251 


0.3846 


3.411 


2599.801 


0.856 


1.3473 


1168.230 


0.3883 


3.422 


2575.,504 


0,864 


1.3515 


1157.414 


0.3919 


3.433 


2551.657 


0.872 


1.3557 


1146.795 


0.3955 


3.443 


2528.248 


0.880 


1.3,598 


1136.370 


0.3992 


3.454 


2505.264 


0.888 


1.3639 


1126.132 


0.4028 


3.464 


2482.694 


0.896 


1.3680 


1116.078 


0.4064 


3.475 


2460.527 


0.904 


1.3720 


1106.201 


0.4100 


3.485 


2438.753 


0.912 


1.3761 


1096.498 


0.4137 


3.495 


2417.360 


0.920 


1.3801 


1086.963 


0.4173 


3.505 


2396.340 


0.928 


1.3841 


1077.593 


0.4209 


3.516 


2375.682 



LENGTH-WEIGHT TABLES 



441 



Table 1-5. 


C = 3,.500 X 10 ' 


, CONTINUED 








WEIGHT/ 












1 ,()()() 


LENGTH 


FISH, 


WEIGHT 


LENGTH 


FISH/ 


FISH (LB) 


(INCHES) 


POUND 


(GRAMS) 


(CM) 


KILOGRAM 


0.936 


1.3880 


1068.382 


0.4246 


3.,526 


23.5.5.377 


0.944 


1.3920 


1059.328 


0.4282 


3.,536 


233,5.417 


0.9.')2 


1.39.^)9 


10.50.427 


0.4318 


3.546 


2315.791 


0.960 


1.3998 


1041.673 


0.4354 


3.555 


2296.493 


0.968 


1.4037 


1033.064 


0.4391 


3.565 


2277.514 


0.976 


1.407.1 


1024.596 


0.4427 


3.,57,5 


2258.846 


0.984 


1.4114 


1016.266 


0.4463 


3.,58,5 


2240.481 


0.992 


1.41,")2 


1008.071 


0.4500 


3.,595 


2222.413 


1 .000 


1.4190 


1000.000 


0.4536 


3.604 


2204.620 


1.080 


1.4."),')9 


925.927 


0.4899 


3.698 


2041.318 


1.160 


1.4909 


862.072 


0..5262 


3.787 


1900.541 


1.240 


1.. 524.5 


806.4,55 


0.5625 


3.872 


1777.928 


1.320 


1.5566 


757.580 


0.,5987 


3.954 


1670.177 


1.400 


1.5874 


714.291 


0.63.50 


4.032 


1574.740 


1.480 


1.6171 


675.681 


0.6713 


4.107 


1489.620 


1..560 


1.64.57 


641.031 


0.7076 


4.180 


1413.230 


1.640 


1.6734 


609.762 


0.7439 


4.2.50 


1344.293 


1.720 


1.7001 


581.401 


0.7802 


4.318 


1281.769 


1.800 


1.7261 


555.562 


0.8165 


4.384 


1224.802 


1.880 


1.7513 


531.921 


0.8.527 


4.448 


1172.684 


1.960 


1.7758 


510.210 


0.8890 


4.511 


1124.820 


2.040 


1.7996 


4!)0.202 


0.92.53 


4.571 


1080.709 


2.120 


1.8229 


471.704 


0.9616 


4.630 


1039.928 


2.200 


1.84.5.5 


4,54..5.52 


0.9979 


4.688 


1002.113 


2.280 


1.8676 


438.603 


1.0342 


4.744 


966.952 


2.360 


1.8892 


423.735 


1.0705 


4.799 


934.174 


2.440 


1.9103 


409.842 


1.1067 


4.852 


903.546 


2..520 


1.9310 


396.831 


1.1430 


4.905 


874.862 


2.600 


1.9512 


384.621 


1.1793 


4.9.56 


847.944 


2.680 


1.9710 


373.140 


1.2156 


5.006 


822.632 


2.760 


1.9904 


362.324 


1.2519 


5.056 


798.788 


2.840 


2.0095 


352.118 


1.2882 


5.104 


776.287 


2.920 


2.0282 


342.471 


1.3245 


.5.1.52 


7,55.019 


3.()()0 


2.0465 


333.339 


1.3608 


5.198 


734.88.5 


3.080 


2.064.5 


324.681 


1.3970 


5.244 


715.798 


3.160 


2.0823 


316.461 


1.4333 


5.289 


697.676 


3.240 


2.0997 


308.647 


1.4696 


5.333 


680.4.50 


3.320 


2.1168 


301.210 


1., 50,59 


5.377 


664.053 


3.400 


2.1337 


2!)4.I23 


1.5422 


5.420 


648.429 


3.480 


2.1.503 


287.361 


1.5785 


.5.462 


633.522 


3.,')60 


2.16(i7 


280.904 


1.6148 


.5.503 


619.286 


3.640 


2.1828 


274.730 


1.6510 


5. .544 


60.5.676 


3.720 


2.1986 


268.822 


1.6873 


5.585 


.592.6,50 


3.800 


2.2143 


263.163 


1.7236 


5.624 


580.174 


3.880 


2.2297 


257.737 


1.7599 


,5.664 


568.211 


3.960 


2.2449 


2.52..530 


1.7962 


.5.702 


,5.56.732 



442 FISH HATCHERY MANAGEMENT 



Table 1-5. c = 3,.^)00> 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