Fish
M a n a g e m e lil
■■'•v.
■••. • ^■.
m:mm
Department of the Interiof
U.S. Fish and Wildlife Service
Fish
Hatchery
Management
Third printing, with corrections, 1986
ISBN 0-913235-03-2
This publication has, been reprinted by the American Fisheries Society in cooperation
with the Fish and Wildlife Service but at no expense to the U.S. Government.
Trade and company names mentioned in this publication are for informational
purposes only. It does not imply U.S. Government endorsement of the product. All
uses of fishery compounds must be registered by appropriate State and/or Federal
agencies. Only those uses described on the label are permitted and only at the rates
listed.
/-r
A
Fish
Hatchery
Management
Robert G. Piper
Ivan B. McElwain
Leo E. Orme
Joseph P. McCraren
Laurie G. Fowler
John R. Leonard
\
Special Advisors
Arden J. Trandahl
Vicky Adriance
United States Department of the Interior
Fish and Wildlife Service
Washington, D. C.
1982
4:" ^
O
O
O
MARINE
BIOLOGICAL
UBORATORY
LIBRARY
VV. H. 0 i
1930
J. T. Bowen
Jack Bess
This publication is dedicated to
J. T. Bowen
Jack Bess
whose initial efforts and dedication
inspired us all to accomplish the task.
Contents
Preface xv
Abbreviations Used in the Text xix
Common and Scientific Names of Fish Species Cited in the Text xxi
1: Hatchery Requirements
Water Quality 3
Temperature 3
Dissolved Gases 4
Oxygen 5
Nitrogen 8
Carbon Dioxide 9
Toxic Gases 10
Dissolved Gas Criteria 70
Suspended and Dissolved Solids JO
Suspended Solids 70
Acidity 7 7
Alkalinity and Hardness 11
Total Dissolved Solids 12
Toxic Materials 12
Heavy Metals 13
Salinity 13
Turbidity 14
vi IISH HAiCllKRV MANAGEMENT
Pesticides 15
Water Supply and Treatment 16
Treatment of Incoming Water 16
Temperature Control 16
Aeration / 7
Sterilization / 7
Treatment of Water for Reuse 19
Ammonia Toxicity 20
Biological Removal of Ammonia 21
Ion Exchange Removal of Ammonia 22
Other Ammonia Removal Techniques 23
Estimation of Ammonia 24
Treatment of Effluent Water and Sludge 25
Hatchery Pollutants 26
Sedimentation Basins 27
Solid Waste Disposal 30
Hatchery Design 32
Buildings 33
Egg Incubation 39
Rearing Facilities 40
Circular Rearing Units 40
Swedish Pond 43
Rectangular Tanks and Raceways 43
Rectangular Circulation Rearing Pond 46
Earthen Ponds 47
Cage Culture 48
Pen Rearing 50
Selection of Rearing Facilities 50
Biological Design Criteria 51
Application of Biological Criteria 54
Bibliography 55
2: Hatchery Operations
Production Methods 60
Length- Weight Relationships 60
Growth Rate 61
Growth at Variable Water Temperatures 62
Carrying Capacity 63
Flow Index 67
Density Index 71
Warmwater Fish Rearing Densities 75
Largemouth Bass 75
CONTENTS
vu
Bluegill 76
Channel Catfish 16
High-Density Catfish Culture 11
Striped Bass 11
Northern Pike and Walleye 11
Inventory Methods 18
Intensive Culture 19
Extensive Culture 81
Fish Grading 83
Fish Handling and Harvesting 84
Rearing Unit Management 88
Sanitation 88
Water Supply Structures 90
Screens 57
Pond Management 91
Preseason Preparation 5/
Wild- Fish Control 93
Fertilization Procedures 94
Organic Fertilizers 91
Inorganic Fertilizers 98
Combining Fertilizers 707
Aquatic Vegetation Control 702
Special Problems in Pond Culture 705
Dissolved Oxygen 705
Acidity 7 70
Turbidity 7 72
Hydrogen Sulfide 7 72
Water Loss 7 13
Problem Organisms 7 7J
Recordkeeping 114
Factors to be Considered 7 74
Production Summary 116
Lot History Production Charts 7 7 7
Definitions 7 75
Instructions 7 75
Totals and Averages 122
Hatchery Production Summary 722
Definitions 722
Instructions 72J
Totals and Averages 124
Warmwater Pond Records 126
Bibliography 725
viii FISH HATCHERY MANAGEMEN 1
3: Broodstock, Spawning, and Egg Handling
Broodstock Management 131
Aquisition of Broodstock 1 32
Care and Feeding of Broodfish 1 32
Forage Fish 140
White Sucker 140
Fathead Minnow 141
Goldfish 142
Golden Shiner 143
Tilapia 144
Improvement of Broodstocks 1 44
Selective Breeding 144
Hybridization and Crossbreeding 148
Spawning 149
Natural Spawning Method 149
Salmonid Fishes 750
Warmwater Fishes 750
Artificial Spawning Method 756"
Factors Affecting Fertilization 76^7
Gamete Storage 168
Anesthetics 76^5
Artificial Control of Spawning Time 7 70
Photoperiod 7 70
Hormone Injection 7 71
Egg Incubation and Handling 173
Egg Development 7 74
Sensitive Stage 7 75
Eyed Stage 7 75
Enumeration and Sorting of Eggs 7 75
Egg Disinfection 1 89
Incubation Period 189
Factors Affecting Egg Development 1 90
Light 190
Temperature 757
Oxygen 752
Transportation of Eggs 1 93
Types of Incubators 1 93
Hatching Trays 1 93
Clark- Williamson Trough 1 94
Catfish Troughs 755
Hatching Baskets 755
Hatching Jars 755
CONTENTS ix
Montana Hatching Box 196
Vertical-Tray Incubators 75 7
Simulated Natural Conditions and Rearing Pond Incubation 1 99
Bibliography 200
4: Nutrition and Feeding
Nutrition 208
Factors Influencing Nutritional Requirements 270
Water Temperature 270
Species, Body Size, and Age 27 7
Physiological Changes 27 7
Other Environmental Factors 272
Digestion and Absorption of Nutrients 2 72
Oxygen and Water Requirements 213
Protein Requirements 214
Protein in Salmonid Feeds 2 75
Protein in Catfish Feeds 2 7 6^
Protein in Coolwater Fish Feeds 27 7
Carbohydrate Requirements 27 7
Carbohydrates in Salmonid Feeds 2 75
Carbohydrates in Catfish Feeds 2 75
Lipid Requirements 220
Lipid Requirements for Salmonids 22 7
Lipid Requirements for Catfish 224
Energy Requirements 224
Energy Requirements for Salmonids 225
Energy Requirements for Catfish 226
Vitamin Requirements 227
Mineral Requirements 229
Nonnutritive Factors 2J7
Fiber 2J7
Pigment-Producing Factors 232
Antioxidants 232
Materials Affecting Fish Quality and Flavor 232
Organic Toxicants in Feeds 233
Sources of Feeds 233
Natural Foods 233
Formulated Feeds 234
Feed Manufacturing 234
Open- and Closed- Formulated Feeds 235
Handling and Storing Procedures 236
Feed Evaluation 238
X riSlI 11 AltllKKV MANACr.MKNT
Feeding 238
Feeding Guides for Salmonids 239
Feeding Guides for Coolwater Fishes 248
Feeding Guides for Warmwater Fishes 249
Catfish 249
Largemouth and Smallmouth Bass 252
Striped Bass 254
Time of Initial Feeding 254
Feeding Frequency 255
Feed Sizes 257
Feeding Methods 259
Bibliography 260
5: Fish Health Management
Disease Characteristics 264
Disease-Causing Organisms 264
Disease Recognition 264
Stress and Its Relationship to Disease 265
Disease Treatment 266
Treatment Methods 268
Dip Treatment 270
Prolonged Bath 271
Indefinite Bath 2 77
Flush Treatment 2 72
Constant-Flow Treatment 272
Feeding and Injection 273
General Information on Chemicals 274
Chemicals and Their Uses 275
Salt Baths and Dips 275
Formalin 275
Copper Sulfate 276
Potassium Permanganate (KMnO,) 277
Quaternary Ammonium Compounds 278
Terramycin" 279
Nitrofurans 280
Sulfonamides 281
Acriflavine 281
Calcium Hydroxide 282
lodophores 282
Di-«-Butyl Tin Oxide 282
Masoten® 282
Equipment Decontamination 283
Facility Decontamination 284
CONTENTS xi
Elimination of Fish 284
Preliminary Operations 284
Decontamination 285
Maintenance of the Hatchery 285
Defense Mechanisms of Fishes 286
Immunization of Fishes 288
Vaccination Methods 288
Fish Disease Policies and Regulations 289
Diseases of Fish 294
Viral Diseases 294
Infectious Pancreatic Necrosis (iPN) 294
Viral Hemorrhagic Septicemia (VHS) 295
Infectious Hematopoietic Necrosis (IHN) 296
Channel Catfish Virus Disease (CCV) 298
Herpesvirus Disease of Salmonids 298
Lymphocystis Disease 299
Bacterial Diseases 300
Bacterial Gill Disease 300
Columnaris Disease 302
Peduncle Disease 303
Fin Rot 304
Furunculosis 304
Enteric Redmouth (ERM) 306
Motile Aeromonas Septicemia (MAS) 307
Vibriosis 310
Kidney Disease 312
Fungus Diseases 314
Protozoan Diseases 315
External Protozoan Diseases 315
Ichtyobodo 315
Ichthyophthirius 316
Chilodonella 319
Epistylis 319
Trie hod ina 320
Ambiphrya 321
Trichophrya 323
Internal Protozoan Diseases 323
Hexamita 323
Henneguya 324
Ceratomyxa 326
Myxosoma 32 7
Pleistophora 328
Trematode Diseases (Monogenetic) 329
Gyrodactylus 330
xii 115.11 iiAiciii.RV manac;i:mi:ni
Dactylogyrus 330
Cleidodiscus 330
Trematode Diseases (Digenetic) 332
Sanguinkola 332
Copepod Parasites 333
Argil lus 334
Lernaea 334
Packing and Shipping Specimens 335
Shipping Live Specimens 340
Shipping Preserved Specimens 341
Fish Disease Leaflets 342
Bibliography 344
6: Transportation of Live Fishes
Transportation Equipment 348
Vehicles 348
Tank. Design 350
Circulation 352
Aeration 353
Water Quality 355
Oxygen 355
Temperature 356
Ammonia 357
Carbon Dioxide 357
Buffers 358
Handling, Loading, and Stocking 358
Stress 358
Anesthetics 359
Carrying Capacity 360
Trout and Salmon 361
Channel Catfish 362
Largemouth Bass, Bluegill, and Other Centrarchids 363
Striped Bass 363
Northern Pike, Muskellunge, and Walleye 364
Stocking Fish 364
Shipping Fish in Small Containers 366
Bibliography 368
Appendices
Appendix A: English-Metric and Temperature Conversion
Tables 375
CONTENTS
Xlll
Append
Append
Append
Append
Append
Append
Append
X B:
X C:
X D:
X E:
X F:
X G:
X H:
Appendix I:
Ammonia Ionization 378
Volumes and Capacities of Circular Tanks 383
Use of Weirs to Measure Flow 384
Hatchery Codes for Designating Fish Lots 387
Nutritional Diseases and Diet Formulations 390
Chemical Treatments: Calculations and Constant Flow
Delivery 401
Drug Coatings for Feed Pellets 405
Length-Weight Tables 406
Glossary
469
Index
503
Preface
The most recent Fish Cultural Manual published by the United States Fish
and Wildlife Service was authored by Lynn H. Hutchens and Robert C.
Nord in 1953. It was a mimeographed publication and was so popular that
copies were jealously sought by fish culturists across the country; it soon
was unavailable.
In 1967, the Service's Division of Fish Hatcheries began to develop a
Manual of Fish Culture, with J. T. Bowen as Editor. Several sections were
published in ensuing years. Efforts to complete the manual waned until
1977 when, due to the efforts of the American Fisheries Society and of the
Associate Director for Fishery Resources, Galen L. Buterbaugh, a task
force was established to develop and complete this publication.
As task- force members, our first business was to identify the audience for
this publication. We decided that we could be most helpful if we pro-
duced a practical guide to efficient hatchery management for practicing
fish culturists. Research and hatchery biologists, bioengineers, and micro-
biologists will not find the in-depth treatment of their fields that they
might expect from a technical publication. For example, we offer a guide
that will help a hatchery manager to avoid serious disease problems or to
recognize them if they occur, but not a detailed description of all fish
diseases, their causative agents, treatment, and control. Similarly, we out-
line the feed requirements and proper feeding methods for the production
of healthy and efficiently grown fish, but do not delve deeply into the
biochemistry or physiology of fish nutrition.
XV
xvi FISH HAICHERV MANAGEMENT
The format of Fisli Hatchery Management is functional: hatchery require-
ments and operations; broodstock management and spawning; nutrition
and feeding; fish health; fish transportation. We have tried to emphasize
the principles of hatchery culture that are applicable to many species of
fish, whether they are from warmwater, coolwater, or coldwater areas of the
continent. Information about individual species is distributed through the
text; with the aid of the Index, a hatchery manager can assemble detailed
profiles of several species of particular interest.
In the broad sense, fish culture as presented in Fish Hatchery Management
encompasses not only the classical "hatchery" with troughs and raceways
(intensive culture), but also pond culture (extensive culture), and cage and
pen culture (which utilizes water areas previously considered inappropriate
for rearing large numbers of fish in a captive environment). The coolwater
species, such as northern pike, walleye, and the popular tiger muskie, tradi-
tionally were treated as warmwater species and were extensively reared in
dirt ponds. These species now are being reared intensively with increasing
success in facilities traditionally associated with salmonid (coldwater)
species.
We have no pretense of authoring an original treatise on fish culture.
Rather, we have assembled existing information that we feel is pertinent to
good fish hatchery management. We have quoted several excellent litera-
ture sources extensively when we found we could not improve on the
author's presentation. We have avoided literature citations in the text, but
a bibliography is appended to each chapter. We have utilized unpublished
material developed by the United States Fish and Wildlife Service; Dale D.
Lamberton's use of length-weight tables and feeding rate calculations, and
his procedures for projecting fish growth and keeping hatchery records
have been especially useful. Thomas L. Wellborn's information on fish
health management greatly strengthened the chapter on that subject.
Many people have helped us prepare this manual. Our special recogni-
tion and appreciation go to Ms. Florence Jerome whose dedication and
diligent efforts in typing several manuscript drafts, and in formating tables
and figures, allowed us to complete the book.
Roger L. Herman and the staff of the National Fisheries Research and
Development Laboratory, Wellsboro, Pennsylvania, supported the project
and assisted in preparation of the manuscript.
We greatly appreciate review comments contributed by federal, state,
university, and private people: James W. Avault; Jack D. Bayless; Claude
E. Boyd; Earnest L. Brannon; Carol M. Brown; Keen Buss; Harold E. Cal-
bert; James T. Davis; Bernard Dennison; Lauren R. Donaldson; Ronald
W. Goede; Delano R. Graff; William K. Hershberger; John G. Hnath;
Shyrl E. Hood; Donald Horak; Janice S. Hughes; William M. Lewis;
David O. Locke; Richard T. Lovell; J. Mayo Martin; Ronald D. Mayo;
PREFACE xvii
David W. McDaniel; Fred P. Meyer; Cliff Millenbach; Edward R. Miller;
Wayne Olson; Keith M. Pratt; William H. Rogers; Raymond C. Simon;
Charlie E. Smith; R. Oneal Smitherman; Robert R. Stickney; Gregory J.
Thomason; Otto W. Tiemeier; Thomas L. Wellborn; Harry Westers. All
these people improved the manual's accuracy and content. Carl R. Sul-
livan, Executive Director of the American Fisheries Society, helped to
stimulate the creation of our task force, and his continued interest in this
project has been a source of strength.
There was much encouragement and effort by many other people who
have gone unmentioned. To all those who took any part in the develop-
ment and publication of the Fish Hatchery Management, we express our grat-
itude.
Lastly, I would like to recognize the guidance, perserverance, tact, and
friendship shown to the task force by Robert Kendall, who provided edi-
torial review through the American Fisheries Society. Without his involve-
ment, the task force would not have accomplished its goal.
Robert G. Piper,
Editor-in-Chief
Abbreviations Used
in the Text
BHA butylhydroxyanisole
BHT butylhydroxytoluene
BOD biochemical oxygen demand
BTU British thermal unit
C condition factor (English units)
°C degrees centigrade or Celsius
cal calories
cc cubic centimeter
CFR Code of Federal Regulations
cm centimeter
cu ft cubic foot
D density index
DO dissolved oxygen
EPA Environmental Protection Agency
et al. and others
F flow index
°F degrees Fahrenheit
ft foot
FWS Fish and Wildlife Service
g gram(s)
gal gallon(s)
gpm gallon(s) per minute
XIX
FISH HArCIIF.RV MANAGF.MKM'
GVW
gross vehicle weight
HCG
human chorionic gonadotrophin
/
water inflow
i.m.
intramuscular
i.p.
intraperitoneal
lU
international units
K
condition factor (metric units); insulation
factor
kcal
kilocalorie
L
length (total)
lb
pound
lbs
pounds
LHP
Lot History Production Chart
m
meter(s)
mg
milligram(s)
min
minute
ml
milliliter
mm
millimeter
MS-222
tricaine methane sulfonate
N
nitrogen
NRC
National Research Council
O.D.
outside diameter
oz
ounce
P
phosphorous
P.C.
Public Code
PCB
polychlorinated biphenols
ppb
part(s) per billion
ppm
part(s) per million
ppt
part(s) per thousand
psi
pound(s) per square inch
SET
standard en\ ironmental temperatures
sp.
species
sq ft
square foot (feet)
T.H.
total hardness
TU
temperature units
Mg
microgram
US
United States
USP
United States Pharmaceutical
V
volume of raceway in cubic feet
w
total weight
W.P.
wettable powder
Wt
weight
Zn
zinc
Common and Scientific
Names of Fishes Cited
in the Text
American eel
American shad
Arctic char
Atlantic salmon
Black bullhead
Blueback salmon
Blue catfish
Bluegill
Brook trout
Brown bullhead
Brown trout
Buffalo
Chain pickerel
Channel catfish
Chinook salmon
Chum salmon
Coho salmon
Common carp
Cutthroat trout
Dog salmon
Fathead minnow
Flathead catfish
Anguilla rostra ta
Alosa sapidissima
Salvelinus alpinus
Salmo salar
Ictalurus melas
see sockeye salmon
Ictalurus furcatus
Lepomis niacrochirus
Salvelinus fontinalis
Ictalurus nebulosus
Salmo trutta
Ictiobus spp.
Esox niger
Ictalurus punctatus
Oncorhynchus tshawytscha
Oncorhynchus keta
Oncorhynchus kisutch
Cyprinus carpio
Salmo clarki
see chum salmon
Pimep hales promelas
Pylodictis olivaris
XX!
XXll
FISH HAICIIKKV M ANAGKMKN I
Grass carp
Golden shiners
Goldfish
Green sunfish
Guppy
Herring
Lake trout
Largemouth bass
Muskellunge
Northern pike
Pink salmon
Pumpkinseed
Rainbow trout
Redbreast sunfish
Redear sunfish
Sauger
Sea lamprey
Sculpin
Smallmouth bass
Sockeye salmon
Steelhead
Striped bass
Tench
Threadfin shad
Tilapia
Walleye
White catfish
Whitefish
White sucker
Yellow perch
Ctenopharyngodon idella
Nolemigonus crysoleucas
Carassius auratus
Lepomis cyanellus
Poecilia reticulata
Clupea harengus
Salvelinus namaycush
Micropterus salmoides
Esox masquinongy
Esox lucius
Oncorhynchus gorbuscha
Lepomis gibbosus
Salmo gairdneri
Lepomis auritus
Lepomis micro lop bus
Stizostedion canadense
Petromyzon marinus
Cottus spp.
Micropterus dolomieui
Oncorhynchus nerka
see rainbow trout
Morone saxatilis
Tinea tinea
Dorosoma petenense
Tilapia spp.
Stizostedion vitreum vitreum
Ictalurus cat us
Coregonus spp.
Catostomus commersoni
Perca flavescens
Fish
Hatchery
Management
1
Hatchery Requirements
The efficient operation of a fish hatchery depends on a number of factorb.
Among these are suitable site selection, soil characteristics, and water qual-
ity. Adequate facility design, water supply structures, water source, and
hatchery effluent treatment must also be considered. This chapter will
identify the more important hatchery requirements and the conditions
necessary for an efficient operation.
Water Quality
Water quality determines to a great extent the success or failure of a fish
cultural operation. Physical and chemical characteristics such as suspended
solids, temperature, dissolved gases, pH, mineral content, and the potential
danger of toxic metals must be considered in the selection of a suitable wa-
ter source.
Temperature
No other single factor affects the development and growth of fish as much
as water temperature. Metabolic rates of fish increase rapidly as tempera-
tures go up. Many biological processes such as spawning and egg hatching
4 FISH HATCHF.RY MANAGKMF.NI'
are geared to annual temperature changes in the natural environment.
Each species has a temperature range that it can tolerate, and within that
range it has optimal temperatures for growth and reproduction. These op-
timal temperatures may change as a fish grows. Successful hatchery opera-
tions depend on a detailed knowledge of such temperature influences.
The temperature requirements for a fish production program should be
well defined, because energy must be purchased for either heating or cool-
ing the hatchery water supply if unsuitable temperatures occur. First con-
sideration should be to select a water supply with optimal temperatures for
the species to be reared or, conversely, to select a species of fish that
thrives in the water temperatures naturally available to the hatchery.
It is important to remember that major temperature differences between
hatchery water and the streams into which the fish ultimately may be
stocked can greatly lower the success of any stocking program to which
hatchery operations may be directed. Within a hatchery, temperatures that
become too high or low for fish impart stresses that can dramatically affect
production and render fish more susceptible to disease. Most chemical sub-
stances dissolve more readily as temperature increases; in contrast, and of
considerable importance to hatchery operations, gases such as oxygen and
carbon dioxide become less soluble as temperatures rise.
Some suggested temperature limits for commonly cultured species are
presented in Chapter 3, Table 17.
Dissolved Gases
Nitrogen and oxygen are the two most abundant gases dissolved in water.
Although the atmosphere contains almost four times more nitrogen than
oxygen in volume, oxygen has twice the solubility of nitrogen in water.
Therefore, fresh water usually contains about twice as much nitrogen as
oxygen when in equilibrium with the atmosphere. Carbon dioxide also is
present in water, but it normally occurs at much lower concentrations than
either nitrogen or oxygen because of its low concentration in the atmos-
phere.
All atmospheric gases dissolve in water, although not in their atmospher-
ic proportions; as mentioned, for example, oxygen is over twice as soluble
as nitrogen. Natural waters contain additional dissolved gases that result
from erosion of rock and decomposition of organic matter. Several gases
have implications for hatchery site selection and management. Oxygen
must be above certain minimum concentrations. Other gases must be kept
below critical lethal concentrations in hatchery or pond water. As for other
aspects of water quality, inappropriate concentrations of dissolved gases in
source waters mean added expense for treatment facilities.
HATCHERY REQUIREMENTS
Corr«cl>Ofl F»c
ors 'O' O
■ ygen
Saiu'
ai.on at V
■ rous Alt
(•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
iJijji|i,iul||i,iii;ii|l|i,i|ii|i|iJrii|i|i;iNlMi|i ||lMl|lll^|lM|I^Nil»^lM|||ll|lM|l||||;|||^||l||^|;l^lMlM|||l^||^l|P|||^
I'l'I'M^'i'l'i'
5 6 7
Oxygen cc per liter
10
11
12
Figure 1. Rawson's nomagram of oxygen saturation values at different tempera-
tures and altitudes. Hold ruler or dark-colored thread to join an observed tem-
perature on the upper scale with the observed dissolved-oxygen value on the
lower scale. The values or units desired are read at points where the thread or
ruler crosses the other scale. The associated table supplies correction values for
oxygen saturation at various altitudes. For example, if 6.4 ppm of oxygen is
observed in a sample having an altitude of approximately 500 m (l,640 feet), the
amount of oxygen that would be present at sea level under the same cir-
cumstances is found by multiplying 6.4 by the factor 1.06, giving the product
6.8; then the percentage saturation is determined by connecting 6.8 on the lower
scale with the observed temperature on top scale and noting point of intersection
on the middle (diagonal) scale.
OXYGEN
Oxygen is the second-most abundant gas in water (nitrogen is the first)
and by far the most important — fish cannot live without it. Concentrations
of oxygen, like those of other gases, typically are expressed either as parts
per million by weight, or as percent of saturation. In the latter case, satura-
tion refers to the amount of a gas dissolved when the water and atmos-
pheric phases are in equilibrium. This equilibrium amount (for any gas)
f) FISH HATCHERY MANAGEMENT
decreases — that is, less oxygen can be dissolved in water — at higher alti-
tudes and, more importantly, at higher temperatures. For this reason, the
relationship between absolute concentrations (parts per million) and rela-
tive concentrations (percent saturation) of gases is not straightforward.
Special conversion formulae are needed; in graphical form these can be
depicted as nomograms. A nomogram for oxygen is shown in Figure 1.
Dissolved oxygen concentrations in hatchery waters are depleted in
several ways, but chiefly by respiration of fish and other organisms and by
chemical reactions with organic matter (feces, waste feed, decaying plant
and animal remains, et cetera). As temperature increases the metabolic rate
of the fish, respiration depletes the oxygen concentration of the water more
rapidly, and stress or even death can follow. Fluctuating water tempera-
tures and the resulting change in available oxygen must be considered in
good hatchery management. In ponds, oxygen can be restored during the
day by photosynthesis and at any time by wind mixing of the air and
water. In hatchery troughs and raceways, oxygen is supplied by continu-
ously flowing fresh water. However, oxygen deficiencies can arise in both
ponds and raceways, especially when water is reused or reconditioned.
Then, chemical or mechanical aeration techniques must be applied by cul-
turists; these are outlined below for raceways, and on pages 108-110 for
ponds. Aeration devices are shown in Figures 2 and 3.
In general, water flowing into hatcheries should be at or near IOO"'!i oxy-
gen saturation. In raceway systems, where large numbers of fish are cul-
tured intensively, oxygen contents of the water should not drop below 80%
saturation. In ponds, where fish densities are lower (extensive culture) than
Figure 2. A simple aeration device made of perforated aluminum can add oxy-
gen to the water and restrict fish from jumping into the raceway above. (FWS
photo.)
HATCHERY REQUIREMENTS 7
Figure 3. Electric powered aerators midway in a series of raceways can provide
up to 2 ppm more oxygen for increased fish production. This type aerator is
operated by a 1 horsepower motor and sprays approximately 1 cubic foot per
second of water. Note the bulk storage bins for fish food in the center back-
ground. (Courtesy California Department of Fish and Game.)
in raceways, lower concentrations can be tolerated for short periods. How-
ever, if either raceway or pond fish are subjected to extended oxygen con-
centrations below 5 parts per million, growth and survival usually will be
reduced (Figure 4).
The lowest safe level for trout is approximately 5 parts per million.
Reduced food consumption by fingerling coho salmon occurs at oxygen
8 FISH HATCHERY MANA(;KMKNT
o
>-
X
o
o
CO
Op SMALL FISH SURVIVE SHORT EXPOSURE
0.3
1.0
2.0
3.0
4.0
5.0
LETHAL IF EXPOSURE PROLONGED
FISH SURVIVE, BUT GROWTH SLOW
FOR PROLONGED EXPOSURE
DESIRABLE RANGE
Figure 4. Effects of dissolved oxygen on warm water pond fish.
Milligrams/liter = parts per million. (Source: Swingle 1969.)
concentrations near 4-5 parts per million, and these fish will die if it drops
below 3 parts per million. Walleye fry do not survive well in water contain-
ing 3 parts per million dissolved oxygen or less. Low levels of dissolved
oxygen below 5 parts per million can cause deformities of striped bass dur-
ing embryonic development.
NITROGEN
Molecular nitrogen (N;) may be fixed by some aquatic bacteria and algae,
but it is biologically inert as far as fish are concerned. Dissolved nitrogen
may be ignored in fish culture so long as it remains at 100% saturation or
below. However, at supersaturation levels as low as 102"^ it can induce gas
bubble disease in fish.
HATCHKR^ REQUIREMENTS 9
Theoretically, gas bubble disease can be caused by any supersaturated
gas, but in practice the problem is almost always due to excess nitrogen.
When water is supersaturated with gas, fish blood tends to become so as
well. Because oxygen is used for respiration, and carbon dioxide enters
into the physiology of blood and cells, excess amounts of these gases in the
water are taken out of solution in the fish body. However, nitrogen, being
inert, stays supersaturated in the blood. Any reduction in pressure on the
gas, or localized increase in body temperature, can bring such nitrogen out
of solution to form bubbles; the process is analogous to "bends" in human
divers. Such bubbles (emboli) can lodge in blood vessels and restrict
respiratory circulation, leading to death by asphyxiation. In some cases,
fish may develop obvious bubbles in the gills, between fin rays, or under
the skin, and the pressure of nitrogen bubbles may cause eyes to bulge
from their sockets.
Gas supersaturation can occur when air is introduced into water under
high pressure which is subsequently lowered, or when water is heated. Wa-
ter that has plunged over waterfalls or dams, water drawn from deep wells,
or water heated from snow melt is potentially supersaturated. Air sucked in
by a water pump can supersaturate a water system.
All fish — coldwater or warmwater, freshwater or marine species — are sus-
ceptible to gas bubble disease. Threshold tolerances to nitrogen supersat-
uration vary among species, but any saturation over 100"" poses a threat to
fish, and any levels over 110"n call for remedial action in a hatchery. Nitro-
gen gas concentrations in excess of 105% cannot be tolerated by trout
fingerlings for more than 5 days, whereas goldfish are unaffected by con-
centrations of nitrogen as high as 120% for as long as 48 hours and 105%
for 5 days. Whenever possible, chronically supersaturated water should be
avoided as a hatchery source.
CARBON DIOXIDE
All waters contain some dissolved carbon dioxide. Generally, waters sup-
porting good fish populations have less than 5.0 parts per million carbon
dioxide. Spring and well water, which frequently are deficient in oxygen,
often have a high carbon dioxide content. Both conditions easily can be
corrected with efficient aerating devices.
Carbon dioxide in excess of 20 parts per million may be harmful to fish.
If the dissolved oxygen content drops to 3-5 parts per million, lower car-
bon dioxide concentrations may be detrimental. It is doubtful that freshwa-
ter fishes can live throughout the year in an average carbon dioxide con-
tent as high as 12 parts per million.
A wide tolerance range of carbon dioxide has been reported for various
species and developmental stages of fish. Chum salmon eggs are relatively
10 MSH HAICHKRY MANAGEMENT
resistant to high levels of carbon dioxide but 50'^ mortality can occur
when carbon dioxide concentrations reach 90 parts per million. However,
concentrations of 40 ppm carbon dioxide have little affect upon juvenile
coho salmon.
TOXIC GASES
Hydrogen sulfide (H^S) and hydrogen cyanide (HCN) in very low concen-
trations can kill fish. Hydrogen sulfide derives mainly from anaerobic
decomposition of sulfur compounds in sediments; a few parts per billion
are lethal. Hydrogen cyanide is a contaminant from several industrial
processes, and is toxic at concentrations of 0.1 part per million or less.
DISSOLVED GAS CRITERIA
As implied above, various fish species have differing tolerances to dissolved
gases. However, the following general guidelines summarize water quality
features that will support good growth and survival of most or all fish
species:
Oxygen 5 parts per million or greater
Nitrogen 100% saturation or less
Carbon dioxide 10 parts per million or less
Hydrogen sulfide 0.1 part per billion or less
Hydrogen cyanide 10 parts per billion or less
In general, oxygen concentrations should be near 100"ii saturation in the
incoming water supply to a hatchery. A continual concentration of 80"ii or
more of saturation provides a desirable oxygen supply.
Suspended and Dissolved Solids
"Solids" in water leave tangible residues when the water is filtered
(suspended solids) or evaporated to dryness (dissolved solids) Suspended
solids make water cloudy or opaque; they include chemical precipitates,
flocculated organic matter, living and dead planktonic organisms, and sedi-
ment stirred up from the bottom on a pond, stream, or raceway. Dissolved
solids may color the water, but leave it clear and transparent; they include
anything in true solution.
SUSPENDED SOLIDS
"Turbidity" is the term associated with the presence of suspended solids.
Analytically, turbidity refers to the penetration of light through water (the
HATCHERY REQUIREMENTS 11
lesser the penetration, the greater the turbidity), but the word is used less
formally to imply concentration (weight of solids per weight of water).
Turbidities in excess of 100,000 parts per million do not affect fish
directly and most natural waters have far lower concentrations than this.
However, abundant suspended particles can make it more difficult for fish
to find food or avoid predation. To the extent they settle out, such solids
can smother fish eggs and the bottom organisms that fish may need for
food. Turbid waters can clog hatchery pumps, filters, and pipelines.
In general, turbidities less than 2,000 parts per million are acceptable for
fish culture.
ACIDITY
Acidity refers to the ability of dissolved chemicals to "donate" hydrogen
ions (H^). The standard measure of acidity is pH, the negative logarithm
of hydrogen-ion activity. The pH scale ranges from 1 to 14; the lower the
number, the greater the acidity. A pH value of 7 is neutral; that is, there
are as many donors of hydrogen ions as acceptors in solution.
Ninety percent of natural waters have pH values in the range 6.7—8.2,
and fish should not be cultured outside the range of 6.5-9.0. Many fish can
live in waters of more extreme pH, even for extended periods, but at the
cost of reduced growth and reproduction. Fish have less tolerance of pH
extremes at higher temperatures. Ammonia toxicity becomes an important
consideration at high pH (Chapter 2).
Even within the relatively narrow range of pH 6.5-9.0, fish species vary
in their optimum pH for growth. Generally, those species that live natural-
ly in cold or cool waters of low primary productivity (low algal photosyn-
thesis) do better at pH 6.5-9. Trout are an example; excessive mortality
can occur at pH above 9.0. The affected fish rapidly spin near the surface
of the water and attempt to leave the water. Whitening of the eyes and
complete blindness, as well as fraying of the fins and gills with the frayed
portions turning white, also occur. Death usually follows in a few hours.
Fish of warmer climates, where intense summer photosynthesis can raise
pH to nearly 10 each day, do better at pH 7.5-9. Striped bass and catfish
are typical of this group.
ALKALINITY AND HARDNESS
Alkalinity and hardness imply similar things about water quality, but they
represent different types of measurements. Alkalinity refers to an ability to
accept hydrogen ions (or to neutralize acid) and is a direct counterpart of
acidity. The anion (negatively charged) bases involved mainly are car-
bonate (CO3 ) and bicarbonate (HCO3 ) ions; alkalinity refers to these
12 FISH HATCHERY MANAGEMENT
alone (or these plus OH ) and is expressed in terms of equivalent concen-
trations of calcium carbonate (CaCO^).
Hardness represents the concentration of calcium (Ca^^) and magnesium
(Mg"^"^) cations, also expressed as the CaCOi-equivalent concentration.
The same carbonate rocks that ultimately are responsible for most of the
alkalinity in water are the main sources of calcium and magnesium as well,
so values of alkalinity and hardness often are quite similar when all are
expressed as CaCO^ equivalents.
Fish grow well over a wide range of alkalinities and hardness, but values
of 120-400 parts per million are optimum. At very low alkalinities, water
loses its ability to buffer against changes in acidity, and pH may fluctuate
quickly and widely to the detriment of fish. Fish also are more sensitive to
some toxic pollutants at low alkalinity.
TOTAL DISSOLVED SOLIDS
"Dissolved solids" and "salinity" sometimes are used interchangeably, but
incorrectly. The total dissolved solids in water are represented by the
weight of residue left when a water sample has been evaporated to dryness,
the sample having already been filtered to remove suspended solids. This
value is not the same as salinity, which is the concentration of only certain
cations and anions in water.
The actual amount of dissolved solids is not particularly important for
most fish within the ranges of 10-1,000 parts per million for freshwater
species, 1-30 parts per thousand for brackish-water species, and 30-40
parts per thousand for marine fish. Several species can live at concentra-
tions well beyond those of their usual habitats; rainbow trout can tolerate
30, and channel catfish at least II, parts per thousand dissolved solids.
However, rapid changes in concentration are stressful to fish. The blood of
fish is either more dilute (marine) or more concentrated (fresh water) than
the medium in which they live, and fish must do continual physiological
work to maintain their body chemistries in the face of these osmotic differ-
ences. Hatchery water supplies should be as consistent in their dissolved
solid contents as possible.
TOXIC MATERIALS
Various substances toxic to fish occur widely in water supplies as a result
of industrial and agricultural pollution. Chief among these are heavy met-
als and pesticides.
HATCHERY RE(^LTREMENTS 13
Heavy Metals
There is a wide range of reported values for the toxicity of heavy metals to
fish. Concentrations that will kill 50"o of various species of fish in 96 hours
range from 90 to 40,900 parts per billion (ppb) for zinc, 46 to 10,000 ppb
for copper, and 470 to 9,000 ppb for cadmium. Generally, trout and salmon
are more susceptible to heavy metals than most other fishes; minute
amounts of zinc leached from galvanized hatchery pipes can cause heavy
losses among trout fry, for example. Heavy metals such as copper, lead, zinc,
cadmium and mercury should be avoided in fish hatchery water supplies, as should
galvanized steel, copper, and brass fittings in water pipe, especially in
hatcheries served by poorly buffered water.
Salinity
All salts in a solution change the physical and chemical nature of water
and exert osmotic pressure. Some have physiological or toxic effects as
well. In both marine and freshwater fishes, adaptations to salinity are
necessary. Marine fishes tend to lose water to the environment by diffusion
out of their bodies. Consequently, they actively drink water and get rid of
the excess salt by way of special salt-excreting cells. Freshwater fishes take
in water and very actively excrete large amounts of water in the form of
urine from the kidneys.
Salinity and dissolved solids are made up mainly of carbonates, bicar-
bonates, chlorides, sulphates, phosphates, and possibly nitrates of calcium,
magnesium, sodium, and potassium, with traces of iron, manganese and
other substances.
Saline seepage lakes and many impounded waters situated in arid
regions with low precipitation and high rates of evaporation have dissolved
solids in the range of 5,000-12,000 parts per million. Fish production in
saline waters is limited to a considerable extent by the threshold of toler-
ance to the naturally occurring salt. Rainbow trout, as an example, gen-
erally tolerate up to 7,000 parts per million total dissolved solids. Survival,
growth and food efficiency were excellent for rainbow trout reared in
brackish water at an average temperature of 56°F. The trout were con-
verted from fresh water to 30 parts per thousand over a 9-day period and
were reared to market size at this salinity.
Mineral deficiencies in the water may cause excessive mortality, particu-
larly among newly hatched fry. Chemical enrichment of water with calcium
chloride has been used to inhibit white spot disease in fry. Brook trout can
absorb calcium, cobalt, and phosphorous ions directly from the water.
14
FISH HAICHKRY MANAGEMENT
ABl.F. 1. SUGGESTED WATER qUAl-ITY CRITERIA lOR OI'IIMIJM HEAl.IH OK SAL-
MONIl) FISHES. CONCENl'RAIIONS ARE IN PARIS I'ER Mil. I. ION (PPM). (SOURCE:
WEDEMEYKR 1!)77.)
CHEMICAL
UPPER LIMITS FOR CONTINUOUS EXPOSURE
Ammonia (NH3)
Cadmium
Cadmium
Chlorine
Copper
Hydrogen sulfide
Lead
Mercury (organic
or inorganic)
Nitrogen
Nitrite (NO2")
Ozone
Polychlorinated
biphenyls (PCB's)
Total suspended and
settleable solids
Zinc
0.0125 ppm (un-ionized form)
0.0004 ppm (in soft water < 100 ppm alkalinity)
0.003 ppm (in hard water > 100 ppm alkalinity)
0.0;-i ppm
().00() ppm in soft water
0.002 ppm
0.03 ppm
0.002 ppm maximum, O.OOOO.'i ppm average
Maximum total gas pressure 1 10"n of saturation
0.1 ppm in soft water, 0.2 ppm in hard water (0.03
and 0.06 ppm nitrite-nitrogen)
(LOO.""! ppm
0.002 ppm
80 ppm or less
0.03 ppm
To protect salmonid eggs and fry. For non-salmonids, 0.004 ppm is acceptable.
To protect salmonid eggs and fry. For non-salmonids, 0.03 ppm is acceptable.
'^Copper at O.OO.") ppm may supress gill adenosine triphosphatase and compromise smoltifica-
tion in anadromous salmonids.
Walleye fry hatched in artesian well water containing high levels of cal-
cium and magnesium salts with a dissolved solid content of 1,563 parts per
million were twice the size of hatchery fry held in relatively soft spring fed
water. This rapid growth was attributed to the absorption of dissolved
solids.
Channel catfish and blue catfish have been found in water with salinities
up to 11.4 parts per thousand. Determination of salinity tolerance in catfish
is of interest because of possible commercial production of these species in
brackish water.
Turbidity
Clay turbidity in natural waters rarely exceeds 20,000 parts per million.
Waters considered "muddy" usually contain less than 2,000 parts per mil-
lion. Turbidity seldom directly affects fish, but may adversely affect pro-
duction by smothering fish eggs and destroying benthic organisms in
HATCHERY REQUIREMENTS
15
Table 2. suggested chemical values for hatchery water supplies, concen-
tration ARE IN PARTS PER MILLION (PPM). (SOURCE: HOWARD N. LARSEN, UNPUB-
LISHED.)
VARL\BLK
TROUT
\V.\RM V\ A IKR
Dissolved oxygen
5-saturation
5-saturation
Carbon dioxide
0-10
0-15
Total alkalinity (as CaC03)
10-400
50-400
% as phenolphthalein
0-25
0.40
% as methyl orange
75-100
60-100
% as ppm hydroxide
0
0
% as ppm carbonate
0-25
0-40
"(1 as ppm bicarbonate
75-100
75- 100
PH
6.5-8.0
6.5-9.0
Total hardness (as CaC03)
10-400
50-400
Calcium
4-160
10-160
Magnesium
Needed for buffer system
Manganese
0-0.01
0-0.01
Iron (total)
0 0.15
0-0.5
Ferrous ion
0
0
Ferric ion
0.5
0-0.5
Phosphorous
0.01-3.0
0.01-3.0
Nitrate
0-3.0
0-3.0
Zinc
0-0.05
same
Hydrogen sulfide
0
0
ponds. It also restricts light penetration, thereby limiting photosynthesis
and the production of desirable plankton in earthen ponds.
Pesticides
Many pesticides are extremely toxic to fish in the low parts- per- billion
range. Acute toxicity values for many commonly used insecticides range
from 5 to 100 microgram/liter. Much lower concentrations may be toxic
upon extended exposure. Even if adult fish are not killed outright, long-
term damage to fish populations may occur in environments contaminated
with pesticides. The abundance of food organisms may decrease, fry and
eggs may die, and growth rates of fish may decline. Pesticides sprayed onto
fields may drift over considerable areas, and reach ponds and streams. If
watersheds receive heavy applications of pesticides, ponds usually are not
suitable for fish production.
Suggested water quality criteria for salmonid and warmwater fishes are
presented in Tables 1 and 2.
16 FISH HATCHERY MANAGEMENT
Water Supply and Treatment
An adequate supply of high quality water is critical for hatchery opera-
tions. Whether fish are to be cultured intensively, requiring constant water
flow, or extensively, requiring large volumes of pond water, the water supply
must be abundant during all seasons and from year to year. Even
hatcheries designed to reuse water need substantial amounts of "make-up"
flow. Among other criteria, hatchery site selection should be based on a
thorough knowledge of local and regional hydrology, geology, weather, and
climate.
Groundwater generally is the best water source for hatcheries, particu-
larly for intensive culture. Its flow is reliable, its temperature is stable, and
it is relatively free of pollutants and diseases. Springs and artesian wells are
the cheapest means of obtaining groundwater; pumped wells are much less
economical.
Spring-fed streams with a small watershed can give good water supplies.
They carry little silt and are not likely to flood. The springs will ensure a
fairly steady flow, but there still will be some seasonal changes in water
temperature and discharge; storage and control structures may have to be
built. It is important that such streams not have resident fish populations,
so that disease problems can be avoided in the hatchery.
Larger streams, lakes, and reservoirs can be used for fish culture, but
these vary considerably in water quality and temperature through the year,
and may be polluted. They all have resident fish, which could transmit
disease to hatchery stocks.
Even though the water supply may be abundant and of high quality,
most hatcheries require some type of water treatment. This may be as sim-
ple as adjusting temperatures or as involved as treating sewage. Excluding
management of pondwater quality, discussed in Chapter 2, and medication
of diseased fish (Chapter 5), water may have to be treated at three points
as it passes through a hatchery system: as it enters; when it is reused; and
as it leaves.
Treatment of Incoming Water
Water reaching a hatchery may be of the wrong temperature for the fish
being cultured, it may have too little oxygen or too many suspended solids,
and it may carry disease pathogens. These problems often are seasonal in
nature, but sometimes are chronic.
TEMPERATURE CONTROL
The control of water temperature is practical when the amount of water to
be heated or cooled is minimal and the cost can be justified. Temperature
HATCHERY REQUIREMENTS
17
control generally is considered in recycle systems with supplemental make-
up water or with egg incubation systems where small quantities of water
are required. A number of heat exchange systems are available commer-
cially for heating or chilling water.
AERATION
Water from springs and wells may carry noxious gases and be deficient in
oxygen; lake and river sources also may have low dissolved oxygen con-
tents. Toxic gases can be voided and oxygen regained if the water is
mechanically agitated or run over a series of baffles.
STERILIZATION
Any water that has contained wild fish should be sterilized before it
reaches hatchery stocks. Pathogens may be killed by chemical oxidants or
by a combination of sand filtration (Figure 5) and ultraviolet radiation.
BACKWASH TROUGHS
BACKWASH
OUTFLOW
FILTER TANK
COLLECTION MAIN FOR CLEAN WATER
DISCHARGE AND BACKWASH INFLOW
Figure 5. Diagram of a sand filter. The water supply is clarified as it flows
down through the sand and gravel bed, and is then collected in the perforated
lateral pipes and discharged from the filter. The filter is backwashed to clean it
by pumping water up through the gravel and sand; the collected waste material
is washed out the backwash outflow.
18 FISH HATCHERY MANAGEMENT
Figure 6. Micro-screen filters consist of a rotating drum covered with woven
fabric of steel or synthetic material with various size openings. The raw water
enters the center of the drum and passes through the fabric as filtered water. As
the fabric becomes clogged, the drum rotates and a high- pressure water spray
(arrow) removes the filtered material from the screen into a waste trough.
Micro-screen fabric is available with openings as small as 5 microns. (FWS
photo.)
Filtration followed by ultraviolet radiation is a proven method for steri-
lizing hatchery water. For example, 125 gallons per minute of river water
containing large numbers of fish pathogens can be sterilized by passage
through two 30-inch diameter sand filters, then through an 18-lamp ultra-
violet radiation unit. The sand filter removes particles as small as 8-15
microns and the ultraviolet radiation kills organisms smaller than 15
microns. It is important that pathogens be exposed to an adequate amount
of ultraviolet intensity for the required effective contact time. Treated
water must be clear to permit efficient ultraviolet light penetration.
Maintenance of sand filters includes frequent backflushing and ultra-
violet equipment requires periodic cleaning of the quartz glass shields and
lamp replacement. Commercially available microscreen filters can be used
as an alternative to sand filters (Figure 6).
Chlorine gas or hypochlorite can be used as sterilants, but they are toxic
to fish and must be neutralized. Ozone is a more powerful oxidizing agent
HATCHERY REQUIREMENTS 19
than hypochlorite, and has been used experimentally with some success. It
is unstable and has to be produced on site (from oxygen, with electrical or
ultraviolet energy). Ozonated water must be reaerated before fish can live
in it. Although very effective against microorganisms, ozone is extremely
corrosive and can be a human health hazard.
Treatment of Water for Reuse
Often it is feasible to reuse water in a hatchery; some operations run the
same water through a series of raceways or ponds as many as ten times.
Any of several reasons can make it worthwhile to bear the added cost of
reconditioning the water. The quantity of source water may be low; the
cost of pollution control of hatchery effluent may be high. The price of en-
ergy to continuously heat large volumes of fresh source water may limit
production of fish; continuous quality control and sterilization may be
expensive.
A hatchery that uses water only once through the facility is called a
"single- pass" system. Hatcheries that recycle water for additional passes by
pumping and reconditioning it are termed "reuse-reconditioning" systems.
In either system, water that passes through two or more rearing units is
termed "reused." Most practical water-reconditioning systems recycle
90-95% of the water, the supplement of make-up water coming from the
source supply. To be practical, the system must operate for long periods
without problems and carry out several important functions (Figure 7).
As water passes through or within a hatchery, fish remove oxygen, give
off carbon dioxide, urea, and ammonia, and deposit feces. Uneaten food
accumulates and water temperatures may change. This decline in water
quality will lower growth and increase mortality of fish if the water is recy-
cled but not purified. A water-reconditioning system must restore original
temperatures and oxygen concentrations, filter out suspended solids, and
remove accumulated carbon dioxide and ammonia. Urea is not a problem
for fish at the concentrations encountered in hatcheries.
Temperatures are controlled, and suspended solids filtered, in ways out-
lined above for incoming water. Oxygen is added and excess carbon diox-
ide removed by mechanical aeration. The removal of ammonia is more
involved, and represents one of the major costs of recycling systems.
The advantage of manipulating rearing environments in a recycle system
has been demonstrated in the rearing of striped bass fry and fingerlings.
They have been reared to fingerling size with increased success when the
salinity of the recycled water was raised to 47 parts per thousand during
the rearing period. Channel catfish also have been successfully reared in
recycled-water systems.
20
FISH HATCHERY MANAGEMENT
WATER SUPPLY
(INPUT)
FILTER
STERILIZE
HEAT OR COOL
HATCHERY
REARING
PONDS
REMOVE WASTE SOLIDS
REMOVE AMMONIA
REMOVE CARBON DIOXIDE
ADD OXYGEN (AERATION)
TEMPERATURE CONTROL
pH CONTROL
WASTE SOLIDS DISPOSAL
BOD REDUCTION
WASTE WATER
(EFFLUENT)
RECONDITIONED
WA
ER
Figure 7. Schematic diagram of a fish hatchery
water reuse system. (Modified from Larmoyeux
1972.)
AMMONIA TOXICITY
When ammonia gas dissolves in water, some of it reacts with the water to
produce ammonium ions, the remainder is present as un-ionized ammonia
(NH .). Standard analytical methods' do not distinguish the two forms, and
The books by Claude E. Boyd and the American Pubhc Health Association et al., listed in
the references, give comprehensive procedures for analyzing water quality.
HATCHERY REQUIREMENTS 21
both are lumped as "total ammonia." Figure 8 shows the reaction that
occurs when ammonia is excreted into water by fish. The fraction of total
ammonia that is toxic ammonia (NH J varies with salinity oxygen concen-
tration and temperature, but is determined primarily by the pH of the
solution. For example, an increase of one pH unit from 8.0 to 9.0 increases
the amount of un-ionized ammonia approximately 10-fold. These propor-
tions have been calculated for a range of temperatures and pH and are
given in Appendix B. Note that the amount of NH^ increases as tempera-
ture and pH increase. From Appendix B and a measurement of total
ammonia (parts per million: ppm), pH, and temperature, the concentration
of un-ionized ammonia can be determined: Ppm un-ionized
ammonia=(ppm total ammonia x percent un-ionized ammonia) ^ 100.
When un-ionized ammonia levels exceed 0.0125 part per million, a
decline in trout quality may be evidenced by reduction in growth rate and
damage to gill, kidney, and liver tissues. Reduced growth and gill damage
occur in channel catfish exposed to 0.12 part per million or greater un-
ionized ammonia.
Ammonia rapidly limits fish production in a water-recycling system un-
less it is removed efficiently. Biological filtration and ion exchange are the
best current means of removing ammonia from large volumes of hatchery
water.
BIOLOGICAL REMOVAL OF AMMONIA
Biological removal of ammonia is accomplished with cultures of nitrifying
bacteria that convert ammonia to harmless nitrate ions (NOj"). These bac-
teria, chiefly species of Nitrosomonas and Nitrobacter can be grown on almost
any coarse medium, such as rocks or plastic chips. The best culture mate
rial contains calcium carbonate, which contributes to the chemical reac-
tions and buffers pH changes; oyster shells often are used for this purpose.
By the time water reaches the biological filter, it should be already well-
aerated (oxygen is needed for the process) and free of particulate matter
FISH "-NHg + HO " Z^ NH^OH." „ NH^^ OH
\
UNIONIZED pH IONIZED
TOXIC FORM DEPENDENT NONTOXIC FORM
Figure 8. Reaction of ammonia excreted into water by fish.
22 FISH HATCHERY MANAGEMENT
(which could clog the filter). It is important that the water be pathogen-
free, because an antibiotic or other drug that has to be used in the
hatchery can kill the nitrifying bacteria as well.
Settling chambers and clarifiers can extend the life of biofilters and reduce
clogging by removing particulate matter. Filter bed material with large void
spaces also can reduce clogging, and foam fractionation will remove dissolved
organic substances that accumulate. These foaming devices are also called
"protein skimmers," which refers to their ability to remove dissolved organic
substances from the water. The foam is wasted through the top of the device
and carries with it the organic material. In a small system, air stones can be
used to create the foam. The air produces numerous small bubbles that col-
lect the organic material onto their surface. Because foam fractionation does
not readily remove all particulate organic material, it should follow the set-
tling or clarifying unit in a reconditioning system.
Nitrite (NO7 ) is an intermediate product of nitrification, and a poorly
operating biofilter may release dangerous amounts of this toxic ion to the
water. A more rapid growth rate of Nitrosomonas in the biological system
can lead to accumulation of nitrite, which is highly toxic to freshwater
fishes. Nitrite oxidizes blood hemoglobin to methemoglobin, a form which
is incapable of carrying oxygen to the tissues. Methemoglobin is
chocolate-brown in color, and can be easily seen in the fish's gills.
Yearling trout are stressed by 0.15 part per million and killed by 0.55
part per million nitrite. Channel catfish are more resistant to nitrite, but 29
parts per million can kill up to 50'!'() of them in 48 hours. Nitrite toxicity
decreases slightly as the hardness and chloride content of water increases.
ION EXCHANGE REMOVAL OF AMMONIA
Ion exchange for removal of ammonia from hatchery water can be accom-
plished by passing the water through a column of natural zeolite. Zeolites
are a class of silicate minerals that have ion exchange capacities (they are
used in home water softeners). Among these, clinoptilolite has a partic-
ularly good affinity for ammonium ions. It is increasingly being used in
hatcheries, where it effects 90 97"o reductions in ammonia (Figure 9).
Clinoptilolite does not adsorb nitrate or nitrite, nor does it affect water
hardness appreciably. It can be regenerated by passing a salt solution
through the bed. The ammonia is released from the salt solution as a gas
and the solution can be reused. Any ion exchange unit can develop into a
biofilter if nitrifying bacteria become established in it. This may lower
exchange efficiencies and cause production of nitrite, so periodic disinfec-
tion may be necessary.
HATCHERY REQUIREMENTS
23
WASTE WATER
SOLIDS
REMOVAL
CLINOPTILOLITE
BED
T
AERATION
BRINE
I
BRINE
REGENERANT
RECOVERY
AMMONIA
RECONDITIONED
WATER
Figure 9. Schematic diagram of ion exchange removal of
ammonia from hatchery waste water.
OTHER AMMONIA REMOVAL TECHNIQUES
Several procedures for removing ammonia from hatchery water have been
tried. Many of them work, but are impractical in most circumstances.
When the pH of water is raised to 10 or 11 with calcium or sodium hy-
droxide, most of the ammonia goes to the gaseous form (NH^) and will dis-
sipate to the air if the water is sprayed in small droplets. This "ammonia
stripping" does not work well in cold weather, and the water has to be
reacidified to normal pH levels.
Chlorine or sodium hypochlorite added to water can oxidize 95-99% of
the ammonia to nitrogen gas (Figure lO). "Breakpoint chlorination" creates
hydrochloric acid as a byproduct, which must be neutralized with lime or
caustic soda, and residual chlorine must be removed as well. This is an
uneconomical process, although future technological advances may improve
24
FISH HATCHERY MANAGEMENT
CHLORINE
WASTE WATER
SOLIDS
REMOVAL
"
BREAKPOINT
CHLORINATION
1
'
ACTIVATED
CAR
ADSOF
BUIN
iPTlON
WASTE SLUDGE
NITROGEN GAS
CHLORAMINES,
EXCESS CHLORINE
AND DISSOLVED
ORGANICS
AERATION
RECONDITIONED
WATER
Figure 10. Schematic diagram of breakpoint chlorination remov-
al of ammonia from hatchery waste water.
its practicality in hatcheries. An advantage of this system is that all treated
v^ater is sterilized.
Oxidation ponds or lagoons can remove 35-85% of the ammonia in
v^astewater through microbial denitrification in the pond bottom and
through uptake by algae. This method requires considerable land area and
extended retention time of the wastewater in the lagoon. Oxidation
lagoons work best in southern chmates. Cold weather significantly reduces
biological activity.
ESTIMATION OF AMMONIA
Because of the importance of ammonia to fish production total ammonia in
hatchery water should be measured directly on a regular basis. However,
rough estimates of total ammonia can be made from an empirical formula,
if necessary. Although ammonia can be contributed by source water and by
HATCHERY REQUIREMENTS 25
microbial breakdown of waste feed, most of it comes from fish metabolism.
The amount of metabolism, hence the amount of ammonia excreted, is
conditioned by the amount of food fish eat. For each hatchery and feed
type, an ammonia factor can be calculated:
ppm total ammonia x ,^pm water inflow
ammonia factor = — - — , . , ;
lbs food ted per day
Here, ppm is parts per million concentration, gpm is gallons per minute
flow, and lbs is pounds. To establish the ammonia factor, total ammonia
should be measured in raceways, tanks, and ponds several times over one
day. Once the factor is established, the formula can be turned around to
give estimates of total ammonia:
lbs food/day x ammonia factor
ppm total ammonia = ~
gpm flow
Then, by reference to Appendix B with the appropriate temperature and
pH, the concentration of un-ionized ammonia can be estimated.
Example: Three raceways in a series have a water flow of 200 gallons
per minute. Fish in the first raceway receive 10 pounds of food per day, 5
pounds of feed per day go into the second raceway, and 20 pounds of feed
per day go into the third. The ammonia factor for these raceways is 3.0. In
the absence of any water treatment, what is the expected concentration of
total ammonia nitrogen at the bottom of each raceway?
Raceway 1: = 0.15 ppm
^ 200
^ (10+5)X3 ^^„
Raceway 2: = 0.23 ppm
^ 200
^ _ (10 + 5 + 20) X 3
Raceway 3: = 0.53 ppm
^ 200 ^
Treatment of Effluent Water and Sludge
The potential of hatchery effluent for polluting streams is very great. Like
any other source of waste water, hatcheries are subject to federal, state, and
local regulations regarding pollution. The United States Environmental
Protection Agency requires permits of hatcheries that discharge effluent
into navigable streams or their tributaries. Hatchery operators are responsi-
ble for knowing the regulations that apply to their facilities. Some treat-
ment of hatchery effluent is required of almost every hatchery. This is true
even for systems that recycle and treat water internally; their advantage
26 KlSll HATCHERY MANAGEMKNT
lies in the greatly reduced volume of effluent to be treated compared with
single-pass hatcheries.
HATCHERY POLLUTANTS
Generally, three types of pollutants are discharged from hatcheries: (l)
pathogenic bacteria and parasites; (2) chemicals and drugs used for disease
control; (3) metabolic products (ammonia, feces) and waste food. Pollution
by the first two categories is sporatic but nonetheless important. If it
occurs, water must be sterilized of pathogens, disinfected of parasites, and
detoxified of chemicals. Effluent water can be sterilized in ways outlined
for source water (page 17). Drug and chemical detoxification should follow
manufacturers' instructions or the advice of qualified chemists and patholo-
gists. Standby detoxification procedures should be in place before the drug
or chemical is used.
The third category of pollutants — waste products from fish and food — is
a constant feature of hatchery operation, and usually requires permanent
facilities to deal with it. Two components — dissolved and suspended
solids — need consideration.
Dissolved pollutants predominantly are ammonia, nitrate, phosphate, and
organic matter. Ammonia in the molecular form is toxic, as already noted.
Nitrate, phosphate, and organic matter contribute to eutrophication of
receiving waters. For the trout and salmon operations that have been stud-
ied, each pound of dry pelleted food eaten by fish yields 0.032 pound of
total ammonia, 0.087 pound of nitrate, and 0.005 pound of phosphate to
the effluent (dissolved organic matter was not determined separately). The
feed also contributes to Biological Oxygen Demand (BOD), commonly
used as an index of pollution; it is the weight of dissolved oxygen taken up
by organic matter in the water.
More serious are the suspended solids. These can, as they settle out,
completely coat the bottom of receiving streams. Predominantly organic,
they also reduce the oxygen contents of receiving waters either through
their direct oxidation or through respiration of the large microbial popula-
tions that use them as culture media. For the trout and salmon hatcheries
mentioned above, each pound of dry feed results in 0.3 pound of settleable
solids — that part of the total suspended solids that settle out of the water
in one hour. Most of these materials have to be removed from the effluent
before it is finally discharged. Typically, this is accomplished with settling
basins of some type.
It should be noted that except for ammonia, the pollutants listed can be
augmented from other sources such as waste food and organic material in
the incoming water. The fish culturist should not assume that the total pol-
lutant concentrations in the effluent are derived only from food eaten by
the fish.
hatchery requirements 27
Table 3. pollutant levels in the effluent frcjm earthen catfish rearing
ponds during fish seining and draining of the pond. (after boyd li»79.)
I'ONI) USH
POLLLTANl'' ORAIMNG SF.INING
Settleable solids (ppm) O.OH 28. .1
Settleable oxygen demand (ppm) 4.31 28. i)
Chemical oxygen demand (ppm) 30.2 342
Soluble orthophosphate (ppb as P) Hi .'J9
Total phosphorus (ppm as P) 0.11 0.49
Total ammonia (ppm as N) 0.98 2.34
Nitrate (ppm as N) O.Hi 0.14
Concentrations (parts per million or per billion) are on a weight basis except for settleable
solids, which are on a volume basis.
The levels of pollutant in a hatchery effluent can be determined with the
following general equation:
,, pollutant factor X lbs food fed
Average ppm pollutant = -. ^
water flow Igpmj
The following pollutant factors should be used in the equation:
Total ammonia
2.67
Nitrate
7.25
Phosphate
0.417
Settleable solids
25.0
BOD
28.3
Example: A trout hatchery in which fish are fed 450 pounds of food per
day and which has a water flow of 1,500 gallons per minute has a total
ammonia concentration of 0.8 parts per million in the hatchery effluent.
. 2.67 X 450
ppm ammonia = -: = O.o
^^ 1500
Studies in warmwater fish culture have shown that there is no consistent
relationship between the weight of fish harvested in earthen ponds and the
amount of settleable solids discharged in the effluent. In general, an
increase in fish weight results in an increase in settleable solids. Pollutant
levels in the discharge from earthen ponds vary with the volume of water
being discharged and the pond design. Some pollutant levels that have
been reported in the effluent of catfish ponds are presented in Table 3.
SEDIMENTATION BASINS
The principle of sedimentation basins is to spread flowing hatchery effluent
out in area, thus slowing it down, so that suspended solids will settle out of
28 KISH HATCHERY MANAGEMENT
Q
100 FT
^
PERFORATED SCREEN
TT^^.
^^
Q
_i
O
C/3
CO
100
50 FT
PROFILE OF SOLIDS SETTLING
85%
100 FT
Figure 11. A characteristic settling profile for settleable waste solids is
shown for a 30 ft X IGQ ft tank with a 4-ft water depth and a water
velocity (V) of 0.056 ft/second. (Source: Jensen 1972.)
their own weight under conditions of reduced water turbulence (Figure ll).
The design of settling basins should take four interrelated factors into
account: (l) retention time; (2) density of waste solids; (3) water velocity
and flow distribution; (4) water depth.
Retention time is the average period that a unit of water stays in the
basin before it is swept out. Depending on the quantity of wastes carried
by the water, retention time can be anywhere from 15 minutes to 2 hours.
In general, retention time increases as the area and depth of the basin
increase. If flow currents are not managed correctly, however, some of the
water passes rapidly through even a larger structure while other water
lingers in backwater areas; the average retention time may seem adequate,
but much waste will still leave the basin. Therefore, it is important that
flow be directed evenly through the structure, and a system of baffles may
have to be incorporated in the design. If water is too shallow, it constantly
scours the bottom, suspends wastes, and carries solids out to receiving
waters. Conversely, if water is too deep, solids do not have time to settle
from top to bottom before water leaves the basin. A water depth of 1^ feet
is a practical compromise in most circumstances.
HATCHERY REQUIREMENTS
29
Sedimentation basins can take several forms. One is a modified concrete
raceway, called a linear clarifier (Figures 12, 13, and 14). Water entering a
linear clarifier should do so through a screen — preferably through a series
of two or more screens — at the head end of the unit. Such screens, which
should be more than 50% open area, distribute flow and reduce turbulence
much better than dam boards, which cause turbulence near them and a
stronger surface than bottom flow.
Perhaps the most common settling basins are outdoor earthen ponds or
"lagoons." These can be of varying sizes and configurations. Obviously, the
bigger the pond, the more effluent it can accommodate. Because of the
amount of land settling ponds occupy, there usually are practical limita-
tions on lagoon size.
Several commercially produced settling systems incorporate baffles and
settling tubes. These are quite efficient and require less space and retention
time than either linear clarifiers or lagoons. However, they can be quite
expensive.
Figure 12. Effluent treatment system at the Jordan River National Fish
Hatchery consists of two linear clarifiers (top), 30 ft x 100 ft with a water depth
of 4 feet. The system will handle up to 600 gpm divided equally between the two
bays. The bays are cleaned by drawing off the top water and moving the sludge
with a garden tractor to collection channels. The sludge is then removed with a
truck-mounted vacuum liquid manure spreader (bottom). (FWS photos.)
30 FISH HATCHERY MANAGEMENT
Figure 13. Three linear clarifiers located at the Jones Hole National Fish
Hatchery, 114 f t x 41 ft and 6 ft deep. Each unit has a sludge scraper system for
sludge removal. These are long redwood boards attached by chain to move and
deposit sludge into the sumps at the upper ends of the clarifiers. This system is
designed to pump sludge to drying chambers. (FWS photo.)
A warmwater fish rearing pond acts as its own settling basin. Except
when the water level is so low that any water movement scours the bottom,
draining a pond usually does not cause much waste escapement. However,
during seining operations when the bottom is disturbed, levels of suspend-
ed solids in the effluent can increase several hundred times. Special atten-
tion should be given to discharges at such times. If water flow through the
pond cannot be stopped until solids can resettle, the effluent may have to
be filtered or diverted away from receiving streams. Likewise, pollutant
loads from other hatchery operations can increase sharply at times. Periods
of raceway cleaning are examples, and there should be means available to
handle the added waste concentrations. Sometimes, raceways and tanks can
be vacuumed before they are disturbed, although this is labor-intensive
work (Figure 15).
SOLID WASTE DISPOSAL
Over half of the total nutrients produced by hatchery operations are in the
form of settleable solids. They must be removed frequently from lagoons
and clarifiers, because they rapidly decompose and would otherwise pollute
the receiving waters with dissolved nutrients.
The "solid" wastes from settling basins and various filtration units
around a hatchery, being 90% water, can accumulate into large volumes
that must be disposed of. Hatchery sludge has considerable value as a fer-
tilizer. In warm climates and seasons, it can be spread directly on the
HATCHERY REQUIREMENTS 31
ground; winter storage at northern hatcheries may be a problem, however.
If transportation is available, or on-site mechanical separators and vacuum
filters can be justified, the sludge can be reduced to moist cakes and sold
to commercial fertilizer manufacturers; some municipal sewage plants
dispose of sludge this way.
Alternatively, if the hatchery is near an urban area, it may be possible to
dispose of solid waste in the municipal system. Incineration of sludge is the
least desirable means of disposal, as dewatering and drying the material is
costly, and the process merely exchanges air pollution for water pollution.
Figure 14. Sludge is collected from the linear clarifiers into storage lagoons at
the Jones Hole National Fish Hatchery, Utah. The lagoons are periodically
dewatered and the sludge dried for removal.
32 FISH HATCHERY MANAGEMENT
Figure 15. (l) A vacuum liquid manure spreader with a modified hose connec-
tion can be used to remove settleable waste solids from fish rearing units.
(2) Water flow is controlled with a j-turn ball valve (arrow). The valve is shut
off whenever the cleaning wand is not actually drawing up waste. Note the set-
tling area provided at the lower end of the raceway. (3) The collected waste
solids are then spread on agriculture lands or lawn areas away from residences.
(FWS photos.)
Hatchery Design
In judging the suitability of a site for a fish hatchery, the primary purpose
of the hatchery should be considered. If egg production is an important
function, somewhat lower temperatures may be desirable than if the
hatchery is to be used primarily for rearing fish to catchable size. Where
no eggs are handled even higher water temperatures may be desirable to
afford maximum fish growth.
For efficient operation of a hatchery, the site should be below the water
source. This will afford sufficient water head to provide aeration and ade-
quate water pressure without pumping. Site considerations should also in-
clude soil characteristics and land gradient. An impervious soil will hold
water with little seepage. Land that is sloped provides drainage and allows
the construction of raceways in a series for reuse of water by gravity flow.
Possible pesticide contamination of the soil and the presence of adjacent
land use that may cause agricultural or industrial contamination should be
investigated. Flood protection is also essential.
HATCHERY REQUIREMENTS 33
If earthen ponds are being considered, sandy or gravel soils should be
avoided. Soils that compact well should be considered where concrete
structures are proposed.
Hatchery labor is an expensive item in rearing fish and good hatchery
design, including use of mechanized equipment, can eliminate a large per-
centage of the labor.
Many items of equipment are available today that can dramatically
reduce hand labor in the fish hatchery. Consideration should be given for
automatic feeding, loading and unloading fish, transporting fish between
fish rearing units and access to rearing units with vehicles and motorized
equipment. As an example, raceways can be designed so that vehicles have
access to all points in the facility. Raceways built in pairs provide a road-
way on each side so that vehicle- drawn feeding equipment can be utilized.
A suitable hatchery site should include sufficient land area for potential
expansion of the facilities. Hatchery planners often overestimate the pro-
duction capacity of the water supply and underestimate the facility
requirements.
Buildings
The principal buildings of a fish hatchery include an office area for record-
keeping, a hatchery building, garages to protect equipment and vehicles, a
shop building to construct and repair equipment, crew facilities and a lab-
oratory for examining fish and conducting water analyses.
The hatchery building should include facilities for egg incubation and
fry and fingerling rearing and tanks for holding warmwater pond- reared
fish prior to shipment. Storage facilities must also be considered for feed,
which may require refrigeration. Separate facilities should also be provided
for chemical storage. A truck driveway through the center or along one
side of building is convenient for loading and unloading fish. Primary con-
sideration should be given to the design and location of buildings and
storage areas to create a convenient and labor saving operation.
Table 4 provides a summary of suggested standards for fish hatchery site
selection and water requirements along with hatchery design criteria.
34 fish hatchery management
Table 4. suggested standards for fish hatchery development, these
standards will change as new construction materials and more effi-
cient designs become available. hatchery symbol: t = trcjut and salmon
(cold water); c = cool water; w = warm water
HATCHERY
ITEM SYMBOL CRIIERI.\
Land
Area required Y C W Enough for facilities, protection of water su[j-
ply, and future expansion; treatment ol
effluent; future water reuse and recirculation
systems.
Topography V C W Sufficient elevation between water source and
production facilities for aeration and gravity
flow. Land should have gentle slopes or
moderate relief that can be graded to pro-
vide adequate drainage. Avoid areas subject
to flooding.
Water supply
Source T C 1 he water supply should be considered in this
order of preference: spring; well; stream;
river; lake or reservoir. An underground
water source should be investigated.
W Lake or reservoir water preferred over creek or
stream supply.
Qj/aiility T C Water requirements are dictated by the size
future of the unit planned. The supply
should provide A changes per hour through
each unit and no less than 1 change per
hour through the entire system. Where
water reconditioning is planned, require-
ments should be adjusted to the capabilities
of the system. Weirs or water meters should
be installed to measure total inflow. Allow
for future expansion. Prospective sources
should undergo long-term chemical analysis
and biological or live fish tests, with
emphasis on periods of destratification when
reservoir or lake supply is contemplated.
Studies should include examination of
watershed for potential sources of pollution
including turbidity. Consider equipment to
filter and sterilize water.
W Dependent upon acreage involved and require-
ments.
Temperature T 45-f)5°F for fish, 4.')-,'J,')°F for eggs. Plan equip-
ment to cool or heat water to temperature
desired.
C fi()~7()°F desirable for walleye and northern
pike culture.
W 70-8()°F preferred during growing season.
IIAICHKin RKUriRKMF.NTS
35
Table 4. continued.
ITEM
HATCHERY
SYMBOL
CRI 1 KRIA
Water supply [continued)
Availability T
Turbidity T
Supply lines
Siie T
Type
C
c
c
earing facilities
Type
T
C
Size
T
C
Floor slope T C
Intake control T C
W Gravity or artesian flow preferred.
Clear.
W Clear or only slightly turbid.
Adequate to carry Ij times quantity of water
required. Consider future hatchery expan-
sion when sizing supply lines.
W Main supply lines adequate to fill 1-acre pond
in 2 days and all ponds in 14 days or less.
W Cast iron, concrete, or steel, unless size or soil
conditions make other materials desirable.
Teflon, nylon, or other proven, durable inert
substances are acceptable. Under no condi-
tions should copper, brass, or zinc galvan-
ized pipe be used.
RacewaNS and circular pools.
W Earthen ponds.
Rectangular raceways: 8' x 80' x 30" or
6' X 60' X 18"; Burrows recirculation ponds:
17' X 7.5' X 3'; Swedish-type ponds:
3f)' X 36'; circular ponds: varying from 6 to
50 feet diameter, concrete or fiberglass con-
struction.
W Earthen ponds: 0.75 to 1.0 acre preferred; 1 to
4 acres allowable; 0.1 to 0.5 acre for special
purposes. Minimum depth of 3 feet at shal-
low end, (i feet at deep end for rearing
ponds. Deeper ponds (10-12 feet) may be
desirable in northern areas, and for channel
catfish rearing regardless of climate. A 2:1
slope is standard with riprap on sides and
3:1 slope without riprap. Dyke tops should
be 12 feet wide with gravel surface. Core
wall mandatory. Seed banks to grass.
0.6" to 1.0" in 10', except bottom of recircula-
tion ponds, which should be level.
Headbox with concrete overflow wall and
adjustable metal weir plate control for indi-
vidual raceways, or pipe discharging above
the pond water surface; inlet should be full
width of raceway.
W Cast iron pipe with shutoff valve for take-off
to ponds. It may be desirable to have two
supplies: the main suppl> at the outlet to
3() KISH HAICUKKV MANAGEMENT
Table 4. continued.
ITEM
HATCHERY
SYMBOL
CRH ERIA
Rearing facilities {continued)
Outlet control T
Screen slots
Freeboard
Water changes T C
Arrangement T C
Electric lines
Screens
Walks
T
T
C
C
provide fresh water in the catch basin when
pond is harvested; and a supplemental sup-
ply at the opposite end from the outlet
structure. The supplies should enter the
pond above the water surface or not lower
than the top of the drain structure.
Overflow full width of raceway, with standpipe
or valve that is tamperproof.
W Standard plans are available, and may be
modified to include concrete baffle and
valve where pumping is necessary. Struc-
tures located in the bank should have ade-
quate wing-walls to prevent sloughing of
embankments. Outside catch basins should
be used where practicable and serve as many
ponds as feasible. Provide steps and walk-
way around the catch basin. A minimum of
10"'ii slope in pipeline from the pond kettles
to the outside catch basin is required. Out-
side catch basins must have a fresh water
supply available. Kettle chimneys should
have 1" X 3" key way for safety covers.
W Double slots in walls and floor at drain end,
either 2-inch double angle or 2-inch channel
of noncorrosive metal.
6-12 inches in raceways, pools.
W In earthen ponds, 18 inches is sufficient.
Ponds should be oriented to limit sweep of
prevailing winds.
W Minimum of 3 per hour, except one for Bur-
rows recirculation ponds.
W Double in series or in rows. Provide 14 feet or
wider driveways between series. Allow suffi-
cient fall between series for aeration; 18-24
inches is recommended, up to 14 feet is
acceptable.
W To be laid at the time of construction either in
raceway walls or alongside with outlets
spaced to satisfy operational requirements.
Consider automatic feeder installations,
floodlights, raceway covers, etc.
W Perforated noncorrosive metal.
W 14-16-inch concrete walkways, broom finish;
aluminum skid-proof grating. For safety all
open flumes, control structures, etc., should
be covered with nonslip grating.
HAICHERV REC^UIRLMENTS
37
Table 4. con tinued.
ITEM
HATCHERY
SYMBOL
CRITERL\
Rearing facilities [continued)
Type of soil T C
Troughs
Type
Screens
Arrangement
Tanks
Type and size
Egg incubation
Buildings
General layout
T C
T C
T
T
T
W
W
W
W
W
Screens
T
C
w
Water changes
T
C
w
Arrangement
T
c
w
w
Effluent treatment T C W
W
General construction T C W
Avoid rocky terrain or unstable soil conditions
such as swamps and bogs. Obtain subsoil
information during site investigations. Con-
duct test borings prior to selecting pond site.
Avoid rocky soil, gravel, limestone substrata,
or old stream beds. Seek solid ground rea-
sonably impervious to water for earthen
ponds.
Fiberglass, metal, wood; rectangular,
14' X 14" X 8" deep or rectangular
16' X 16" X 16" double, deep-type.
Perforated metal.
Double with individual supply and drains. If
used in series, allow fall between tanks of at
least 12 inches and an aisle between tanks.
Circular 4-8 feet diameter, sloped
bottoms J inch per foot of radius; rectangu-
lar, 3'x3'x30' double arrangement.
Perforated aluminum.
Five per hour.
For convenience, with sufficient aisle space for
handling and removing fish.
Commercial incubators such as Heath or
equivalent recommended. Jar culture or
hatching boxes may be adaptable in some
instances.
Provide settling basin of size and design that
will effectively settle out solids from used
water prior to its release from the hatchery
proper.
Arrange buildings to expedite work, to present
a pleasing appearance, and to be compatible
with topography and approach routes. Con-
sideration of local architecture is desirable.
Provide adequate spacing between buildings
for fire control.
Design for economical heating; steam or hot
water is preferred for large buildings. Avoid
condensation problems in the tank room by
providing adequate insulation, ventilation,
and heating.
38 FISH HATCHERY MANAGEMKNT
Table 4. continued.
ITEM
HATCHERY
SYMBOL
CRITERIA
Hatchery buildings
Arrangement
Tank
Incubation area
Feed storage
General storage
Office
Laboratory
W
W
c
w
w
T C W
T C W
T C W
Hatchery room, incubation area, feed storage,
material storage, crew's room, toilet facilities,
and small office area. Administrative offices
and visitor facilities are not recommended
for inclusion in hatchery building proper.
Allow 2.,')-foot aisles between tanks and 4-fi
feet around ends. Floor: concrete with
broom finish, slope (l" in 10') for drainage.
Walls and ceilings should be cement asbes-
tos or other waterproof material. Water sup-
ply and drain systems should be designed
for flexibility and alteration. Buried lines
should be kept to a minimum. A fish tran-
sport system (pipe) from tank room to out-
side ponds is desirable. Portals in the walls
are convenient for moving fish out of the
hatchery building.
Separate room or designated area in the tank
room should be provided for egg incubation.
Use of stacked commercial incubators is
recommended. Permit flexibility in arrang-
ing incubators, small troughs, or tanks
within the room.
A separate storage area for dry feed is recom-
mended because of undesirable odors. It
should be located convenient to use area.
Consider bulk feed storage and handling
where more than 50 tons of feed is required
annually. Provide storage for one-fourth of
annual dry feed requirements with protec-
tion against moisture and vermin. There
should be proper ventilation and tempera-
ture control. The delivery area should have
turnaround room for large trucks. Include
elevation loading dock or mechanical
unloading equipment. If moist pellets are
used, cold storage (lO°F) for fiO-days supply
should be provided.
Locate convenient to tank room, provide
ample size for intended purpose, and design
for maximum utilization of wall space with
shelves and storage lockers.
Main offices should be located in a separate
administration building.
Equipped and sized in accordance with antici-
pated needs.
HATCHERY REQUIREMENTS
39
Table 4. continued.
ITEM
HATCHERY
SYMBOL
CRITERIA
Hatchery buildings {continued)
Crew room T C
Garage and storage
building
Shop
Oil and paint
storage
Fertilizer and
chemical
storage
W
w
w
w
w
Room should provide locker space for each
employee, and be adequate to serve as a
lunch room. Shower facilities should be pro-
vided.
Size of building or buildings is dependent
upon the number of truck stalls required
and the amount of material to be stored.
Concrete floors should be broom finish with
a 1" in 10' slope to doors.
Minimum of 300 square feet, floor 1" in 10'
slope to door or center drain. Provide heat-
ing and electrical systems to satisfy require-
ments, including 220-volt outlets; overhead
door should be at least 10 feet wide and 9
feet high. Build in cabinets for tool storage
and adequate work bench area.
Provide a separate building, or materials may
be stored in another building if a special
room rated for a '2-hour fire, with outside
access, is provided. The electrical installa-
tion should be explosion- proof. Provide
heat if storage of water base paints is con-
templated.
Explosion-proof electrical fittings and positive
ventiliation must be provided.
Egg Incubation
Incubation equipment is being modified constantly and several different
types are available commercially. There are basically two concepts for the
incubation of fish eggs. One method involves the use of wire baskets or
rectangular trays suspended in existing hatchery troughs to support the
eggs. The hatched fry drop through the wire mesh bottom of the basket or
tray to the bottom of the trough. This method does not require additional
building space because existing facilities are utilized. Other methods of egg
incubation are jar culture or vertical tray incubation. Additional space in
the hatchery building is required for this equipment. Control of water tem-
perature should be part of any hatchery design involving egg incubation
and hatching of fry. Heating or chilhng of water for optimum incubation
40 FISH HAICIIKKY MANAGEMENT
temperature is practical with today's equipment, which requires relatively
less water flow than older methods of egg incubation. Various types of egg
incubation are described in detail in Chapter 3.
Rearing Facilities
Rearing units for intensive fish culture include starting tanks or troughs for
swim- up fry, intermediate rearing tanks for fingerlings, and large outdoor
rearing ponds or raceways.
Rearing units should be constructed so they can be drained separately
and quickly. They should be adequate not only for the normal operating
flow in the hatchery but also for increased volumes of water needed during
draining and cleaning of the facilities.
Much personal opinion and preference is involved in the selection of a
rearing unit. Fish can be raised successfully in almost all types of rearing
units, although some designs have distinct advantages in certain applica-
tions. Adequate water flow with good circulation to provide oxygen and
flush metabolic waste products are of paramount importance in the selec-
tion of any facility. Ease of cleaning also must be considered.
CIRCULAR REARING UNITS
Limited water supplies make semiclosed water recycling systems highly
desirable. The most efficient involve circular units and pressurized water
systems. By common acceptance, circular "tanks" refer to portable or semi-
portable units up to 12 feet in diameter, while "pools" refer to permanently
installed units up to 40 feet in diameter.
There are basic criteria for construction and design of circular tanks and
pools that are essential for their satisfactory operation. Double-walled or in-
sulated tanks reduce external condensation and eliminate dripping water.
Adequate reinforcement must be incorporated in the bottom of the tank to
support the filled units. There is no need for a sloping bottom except to
dry out the tank. Flat-bottomed tanks will self-clean well if proper water
velocities are established. The walls should be smooth for easy cleaning. In
the case of portable tanks, the preferred material is fiber glass, but good
tanks can also be constructed of wood or metal. Large circular pools are
usually constructed of masonry.
Without proper equipment, removal of fish from larger circular tanks is
difficult. Crowding screens facilitate the removal of fish (Figures 16 and
17). Some types of pools have inside collection wells for the accumulation
of waste and removal of fish.
HATCHERY REQUIREMENTS 41
Figure 16. Crowding screen used in smaller circular tanks.
Large circular tanks and pools can be modified with a flat center bottom
screen and an outside stand pipe to control water depth for ease of opera-
tion. An emergency screened overflow is advisable in the event the bottom
effluent screen becomes clogged. Horizontal slots in the drain screens allow
better cleaning action and are not as easily clogged as round holes. They
also provide more open screen area. Cylindrical center screens used in
4-6-foot diameter tanks provide better cleaning action if they are not per-
forated in the upper portion, so that all effluent leaves the tank through
the bottom portion.
Self-cleaning properties of the pool are dependent on the angle at which
inflowing water enters. The angle of inflow must be adjusted according to
the volume of water being introduced and the water pressure (Figure 18).
The carrying capacity (number or weight of fish per volume of con-
tainer) of circular tanks and pools is superior to those of troughs, rectangu-
lar tanks, and raceways if there is sufficient water pressure for reaeration.
42 FISH HATCHERY MANAGEMENT
'?*i;|ii^i^uit/iialiji;.
Figure 17. A fish crowder for large- diameter circular pools, (l) Screens are
inserted into the thret -sided frame, after it is placed in the pool. (2) One end of
the frame is anchored to the pool wall with a retaining rod, and the other end is
carefully guided around the circumference of the pool, herding the fish ahead of
the crowder. (3) The fish can be readily netted from the rectangular enclosure
formed by the three sides of the crowder and weighed. Note the hanging dial
scale and dip net (see inventory methods in Chapter 2). (4) The crowder also
can be used for grading fish when appropriately spaced racks are inserted in the
frame. Small fish will swim through the racks, leaving the larger ones entrapped.
Aluminum materials should be used to construct the crowder to reduce weight.
(FWS photo.)
Air, driven into the water by the force of the inflowing water, provides ad-
ditional oxygen as the water circulates around the tank or pool. Water in-
troduced under pressure at the head end of rectangular troughs or race-
ways does not have the same opportunity to reaerate the water flowing
through those units.
An example of the effect of water pressure on circular tank environments
is presented in Table 5. At low pressures, the amount of dissolved oxygen
limits the carrying capacity; at high pressures the buildup of metabolites
(ammonia) limits production before oxygen does.
There must be a compromise between velocity and the flow pattern best
suited for feed distribution, self-cleaning action of the tank and the energy
requirement of continuously swimming fish. This environment may not be
suitable for such fish as northern pike, which do not swim actively all of
the time. When properly regulated, the flow pattern in a circular tank will
effectively keep feed particles in motion and will eventually sweep uneaten
hatchery requirements 43
Table 5. ammonia and oxygen concentrations in identical circular
tanks with high- and low-pressure water systems. tank diameters are 6
feet, tank volumes are ,'i30 gallons, flows are 10 gallons per minute
(gpm), water changes are 1.13 per hour, fish size is 8.5 inches, and oxygen
content of inflow water 8.5 parts per million (ppm). water pressures are
pounds per square inch (psi).
WATER PRESSURE
HIGH (29 PSI)
LOW (1..5 PSI)
Fish weight (pounds)
100
200
250
300
100
200
250
Pounds/cubic foot
1.4
2.8
3.5
4.3
1.4
2.8
3.5
Pounds/gpm
10
20
25
30
10
20
25
Total ammonia (ppm)
0.21
0.44
0.80
0.89
0.21
0.44
0.74
Dissolved oxygen (ppm)
7.5
6..T
5.2
5.1
5.8
4.3
3.2
food and excrement toward the center for removal through the outlet
screen. Velocity should never be great enough to cause fish to drift with
the current. Velocities for small fry may be so low ttiat the tank does not
self-clean and it will be necessary to brush accumulations of waste to the
center screen.
Oxygen consumption per pound of fish is higher in circular tanks than
in troughs and raceways. This difference may be due to the increased ener-
gy demand created by the higher water velocity in the circular tank.
SWEDISH POND
The Swedish Pond was developed specifically for Atlantic salmon. It is
square with rounded corners and its operation is very similar to that of a
circular tank. Water is supplied through a pipe at the surface of the water.
Waste water leaves the tank through a perforated plate in the center of the
unit and the water level is controlled by a standpipe outside the wall of the
tank. This design provides a large ratio of surface area to water volume;
some fish culturists feel that Atlantic salmon require more surface area as
they do not stack over each other like other salmonids.
RECTANGULAR TANKS AND RACEWAYS
Originally rectangular raceways were elongated earthen ponds. Such ponds
required considerable maintenance because weeds and plants grew along
the banks and the pond walls eroded. Irregular widths and depths resulted
in poor water flow patterns.
Rectangular tanks or troughs generally are used for rearing small fry and
fingerlings in the hatchery building (Figure 19). These can be made of
aluminum, fiber glass, wood, or concrete. Potentially toxic material such as
44
FISH HATCHERY MANAGEMENT
A
Figure 18. Piping and water flow arrangement in (A) 20-ft and (B) 5-ft diame-
ter circular tanks. The velocity and direction of water flow can be changed by
swinging the horizontal pipe toward or away from the tank wall, and twisting
the pipe clockwise to change the angle of inflow. The velocity is lowest when the
water is directed downward into the tank, as shown in (B). The bottom screen
plate and external head-box (arrow) eliminate vertical screens and standpipes in
the center of the tank. Note that only one automatic feeder is required per tank.
(FWS photo.)
HATCHERY REQUIREMENTS 45
galvanized sheet metal should be avoided. Dimensions of raceways vary,
but generally a length:width:depth ratio of 30:3:1 is popular. Properly con-
structed raceways have approximately identical water conditions from side
to side, with a gradual decline in dissolved oxygen from the head end to
the lower end. Levels of ammonia and any other metabolic waste products
gradually increase towards the lower end of the unit. Although this
represents a deterioration of water quality, some hatchery workers feel that
a gradient in water quality might be better for the fish because it attracts
them to the higher quality water at the inflow end of the raceway. In circu-
lar ponds, there is no opportunity for the fish to select higher oxygen and
lower ammonia levels.
FlGlRF. 1!). Rectangular aluminum troughs (background) and concrete tanks.
Small swim-up fry generally are started on feed in the troughs and then
transferred to the tanks when they are 1-1 j -inch fingerlings. (FWS photo.)
46
FISH HATCHERY MANAGEMENT
Figure 20. Rectangular circulation rearing pond ("Burrows pond"). Water is
recirculated around the pond with the aid of turning vanes (arrow). Waste water
flows out through floor drains located in the center wall (not shown). (FWS
photo.)
Raceways should not vary in width, since any deviation can cause eddies
and result in accumulation of waste materials. It is desirable to have ap-
proximately one square foot of screen area at the outflow of the raceway
for each 25 gallons per minute water flow. The percent open area of the
screen material must also be considered.
Raceways have some disadvantages. A substantial supply of water is
required and young fish tend to accumulate at the inflow end of the unit,
not utilizing the space efficiently. The raceway is believed by many
hatchery operators to be the best suited for mass-producing salmon finger-
lings. Its ease of cleaning, feeding, and fish handling make it desirable
where ample water supplies are available.
RECTANGULAR CIRCULATION REARING POND
The rectangular circulation rearing pond is commonly known as the
"Burrow's Pond" (Figure 20).
Its basic design incorporates a center wall partly dividing a rectangular
pond into two sections of equal width. Water is introduced into the pond
under pressure and at relatively high velocities, through two inflow pipes
located at opposite ends of the pond. The flow pattern is controlled with
HATCHERY REQUIREMENTS 47
vertical turning vanes at each pond corner. The water generally flows
parallel to the outside walls of the unit, gradually moves toward the center
wall, and leaves the pond through the perforated plates in the pond bottom
at opposite ends of the center wall.
The rectangular pond operates well at a water depth of either 30 or 36
inches, depth being controlled by a removable standpipe in the waste line.
An advantage of the rectangular circulation pond is that fish are well dis-
tributed through the pond and the water current carries food to the fish.
This reduces concentrations of fish at feeding time. It is relatively self-
cleaning due to the water path created by the turning vanes at inflows of
400 gallons per minute or greater. The water flow and turbulence along the
center wall carry debris and waste material to the outlet.
Pond dimensions and water flows are very specific, and any change in
the design criteria of this rearing unit may drastically alter the hydraulic
performance. This can prove a distinct disadvantage when flexibility of fish
loads and water flows is desired.
EARTHEN PONDS
There is general agreement that concrete raceways are cheaper to maintain
and operate than earthen ponds. Many fish culturists contend, however,
that fish reared in dirt raceways and ponds are healthier and more colorful,
have better appearing fins, and are a better product.
Rectangular earth ponds usually are more convenient and efficient, and
may range in size from | acre to 3 acres or more. Large ponds of irregular
shapes are more difficult to clean, and it is harder to feed and harvest fish
and to control disease in them.
It is doubtful that fish production will become as intensive in large
earthen ponds as in smaller types of rearing units that have more water
changeovers. Earth ponds do have relatively low water requirements and
produce some natural food. Successful culturing of trout and salmon have
been accomplished in this type of facility and use of supplemental aeration
has increased catfish production dramatically in recent years.
Harvest methods must be considered in the design of an earthen pond.
Ponds must be drainable and contain a basin or collection area for harvest-
ing the fish (Figures 21 and 22), although many of the fish can be seined
from the pond before it is drained. The bottom of the pond should slope
gradually toward the outlet from all sides. Pond banks should be built with
as steep a slope as possible to avoid shallow-water areas along the edge of
the ponds. Shallow areas collect waste material and allow dense growths of
vegetation to develop.
Topography for construction of earthen ponds should be gently sloping
and should have only moderate relief that can be economically removed.
48
FISH HATCHERY MANAGEMENT
DRAIN PIPE
< ^
CATCH BASIN
CREEN
7T^^
» =
♦ \\ *
« «»"="//
■(■=://.,
««
Figure 21. Pond outlet with catch basin. (Source: Davis 1953)
The soil type is extremely important; clay soil or subsoil is best. Seepage
tests at the pond sites are highly desirable. Seepage loss is not as important
in intensive salmon or trout culture where abundant quantities of water
flow through the pond, but is important in warmwater fish culture where
circulating water flows are not required.
Pond banks must be stable and well drained, because heavy tractors and
feed trucks must have access to the ponds preferably along gravelled road-
ways. Cement or transite material is best for water supply lines and drain
lines.
CAGE CULTURE
There is growing interest in cage culture of warmwater species such as cat-
fish. This involves rearing fish in small enclosures built of wire or plastic
netting stretched over a frame. The cages are attached in series to floating
platforms and anchored in rivers, lakes, and ponds or in protected areas
along coastal shores (Figure 23). Water currents and wind action carry
HATCHERY REQUIREMENTS 49
^HAMttmmaimm:^
i* J
Figure 22. A pond catch basin should have a supply line (arrow) to
provide fresh water to the fish when they are collected in the basin.
This pond outlet also has a valve to open the pond drain.
away wastes and provide fresh water. Cage culture is readily adapted to
areas that cannot be drained or from which fish cannot be readily har-
vested. However, good water circulation must be assured, as an oxygen
depletion in water around cages can cause catastrophic fish losses. Disease
control is very difficult in cage culture and labor requirements are high.
Feeding and treatment for disease must be done by hand.
Largemouth bass fingerlings have been experimentally grown in cages.
Cylindrical instead of rectangular containers were used to prevent crowd-
ing in corners, which might cause skin damage to active fish such as bass.
Moist trout pellets were fed to the fish; a retaining ring kept the food in-
side the cage until it could be eaten.
Figure 23. Cage culture of catfish. IFWS photo.)
50 FISH HATCHERY MANAGEMENT
PEN REARING
Marine culture of salmon and trout in cages is called "pen rearing." Pen
culture developed in Scandinavia and Japan, and commercial operations
began recently in Washington state. Rainbow trout and Atlantic, chinook,
and coho salmon have been cultured in sea water. Coho salmon have been
the most popular in the United States because they are relatively resistant
to disease and can be fed formulated feeds. After initial rearing in fresh
water, the juvenile fish complete their growth to marketable size in saltwa-
ter pens.
The term "sea ranching" is used when hatchery-reared salmon are
released as smolts and allowed to migrate to the ocean to complete the ma-
rine portion of their life cycle.
Pen rearing relies on tidal currents to supply oxygen and flush out meta-
bolic wastes. The pens and floating structures cost less than a fish hatchery
on land, but must be protected from storms and high winds, and some type
of breakwater may be necessary. Some freshwater facilities must be avail-
able on land, however, to incubate the salmon eggs and initially rear the
fry.
Water temperatures should not fluctuate greatly during pen culture;
50— 57°F are best for salmon. Prolonged higher temperatures lead to disease
problems. Although disease has been a serious problem in saltwater farm-
ing, recent developments in immunization of fish with vaccines show great
promise for overcoming this (Chapter 5).
SELECTION OF REARING FACILITIES
No single pond type will meet all requirements of fish hatcheries under all
rearing conditions. Topography of the land, water source, species of fish
being reared, and availability of funds and material will influence the selec-
tion of the rearing unit. There is a wealth of literature describing the
strong and weak points of various hatchery rearing facilities, much of it
conflicting. Personal preference based on experience tends to play a key
roll in making a selection. As pointed out previously, all of the types of
rearing units described successfully raise fish.
In any hatchery construction there are several important objectives that
must be kept in mind: (l) to provide a compact rearing unit layout that
will allow future development of the hatchery; (2) to provide adequate
intake and outlet water supply facilities to meet the special requirements of
pond cleaning, treatment of fish for disease, and collection and handling of
fish; (3) to allow sufficient slope on pond bottoms for complete drainage
and provide for a practical and efficient means of collecting fish for
removal, sorting, or treating; and (4) to provide adequate water and rearing
space to safely accommodate the anticipated production of the hatchery.
HATCHERY REQUIREMENTS 51
Table 6 summarizes some of the characteristics of the various rearing
units that have been described.
Biological Design Criteria
Every species of fish has basic environmental requirements and each has
optimum conditions under which it thrives and can be efficiently cultured.
Biological criteria are essential in the design of any fish culture facility and
these criteria must be recognized before a successful fish rearing program
can be developed. The following comments are abstracted from
Nightingale (1976).
Information required in designing a facility includes fishery management
needs, fish physiology, chemical requirements, disease, nutrition, behavior,
genetics, and fish handling and transportation.
These criteria must be developed for each species to be cultured. The
fishery management criteria include identification of the species to be
reared, desired sizes for production, and desired production dates. Manage-
ment criteria are usually listed as the number and length (or weight) of fish
that are required on certain dates. Physiological criteria include oxygen
consumption for various fish sizes and optimum temperatures for
broodstock holding, egg incubation, and rearing. Required rearing space,
water flows, and spawning and incubation methods are included in these
criteria. Chemical criteria include water quality characteristics that affect
the species of fish to be reared, such as tolerable gas saturation, pH, and
water hardness. Disease criteria include methods for disease prevention and
treatment. Nutrition criteria involve the types of feeds, feeding rates, and
expected food conversions at different temperatures and fish sizes.
Behavior criteria are needed to identify special problems such as cannibal-
ism and excessive excitability; for example, a decision may be made to use
automatic feeders to avoid a fright response. Genetic criteria involve
selection of specific strains and matching of stocks to the environment.
Transportation and handling criteria involve the acceptable procedures and
limitations for handling and moving the fish.
The application of these criteria to the particular circumstances at each
hatchery can result in a biologically sound culture program. A program can
be developed by combining the management and physiological criteria
with the particular species and water temperatures to be utilized. Rearing
space and water flow requirements can be defined and combined with the
other criteria to establish a suitable hatchery design.
Good program development for fish hatchery design should include, in
addition to biological criteria, adequate site evaluation, production alterna-
tives, and layout and cost estimates.
52
I-ISH HAICHEKY MANAGEMENT
Table 6. summary of rearing unit characteristics for fish hatcheries.
TYPE
UA 1 KR SLl'I'l.V
I()I'(K.KA1'II^
Various sizes available
in a variety of materi-
als. Can be used for
small or large groups
of fish.
Circular tanks and ponds
Pump or high-pressure
gravity; low flow
volume.
Level or sloped.
Fairly restricted to one
size; used e.xtensively
with large groups of
production fish.
Reitangular-circ II latum rearing ponds
Same as above.
Same as above.
Various sizes; used for
small or large groups
of fish. Larger units
made of concrete.
Swedish ponds
Same as above.
Same as above.
Small tanks made with a
variety of materials;
used for small or large
groups of fish. Race-
ways generally made
of concrete for large
groups of production
fish.
Rectangular tanks and raceways
High- or low pressure
gravity; high flow
volume preferred.
Slope preferred for
reaeration ol water
between units.
Generally for large
groups of production
fish.
Ear/hen ponds
High- or low pressure
gravity; high or low
flow volume.
Level preferred. Consid-
erable area of land
required.
Various net materials;
can be built in various
sizes. Generally
smaller units than
raceways or ponds.
Cage culture and pen rearing
Lake or pond with some
current or protected
coastal or stream area.
Protected shoreline.
HATCHERY REQUIREMENTS 53
DISKASE CON IROl, SPFXIAL FEATLRKS
Circular tanks and pond ^
Can be a problem bee ause of recirculating Controlling velocities, self-cleaning.
v\ater and low How rates.
Reclangular-circulation rearing ponds
Same as abo\e. Uniform velocity throughout; relatively
self-cleaning. Expensive construction.
Swedish ponds
Same as abo\ e. Self-cleaning; large surface area to depth
ratio. Moderate velocitv control.
Rectangular tanks and raceways
\'er> good if tank designed properly. Relatively ine.xpensi\e construction,
readil) adaptable to mechanization
(cleaning, feeding, crowding).
Earthen ponds
A problem because of flow patterns and Many attributes of a natural environment,
buildup of wastes hc\m large groups of
production fish.
Cage culture and pen rearing
Difficult Inexpensive facilitv ; water readily a\ail
able.
54
FISH HATCHERY MANAGEMENT
Table 7. typical biological data organized into a concise format to aid
IN developing a rearing program and ultimately designing a hatchery.
(SOURCE: KRAMER, CHIN AND MAYO 1976.)
TEMP-
AVERAGE
TOTAL
FLOW
SPACE
LOCA-
ATURE
NUMBER
LENGTH
WEIGHT
NEEDED
NEEDED
DATE
EVENT
TION
(T)
(millions)
(INCHES)
(POUNDS)
(gpm")
March 1.^
'Egg
take
Incub-
tion
150
Jars
54
45
150
March 29 Hatch
April 1
Begin
feed
8 ST*
54
15
0.2
150
60
1,280
April 1
Release
54
3
0.2
300
May 1
3 RW'
60
1.3
1.0
520
380
4,730
June 1
4 RW'
66
1.1
2.0
3,780
700
7,000
June 15
Release
1.0
2.6
7,000
"Gallons per mi
nute.
Starter tanks.
Raceways.
APPLICATION OF BIOLOGICAL CRITERIA
The following is a brief explanation of the methodology and format used
by Kramer, Chin and Mayo, engineering consultants, in formulating a rear-
ing program based on biological criteria. A typical program is used to
demonstrate step-by-step planning. Table 7 illustrates how collected bio-
logical data can be organized concisely.
(1) Determine temperature. The first step in preparing a rearing program is
to obtain either the ambient or adjusted monthly water temperature ex-
pected for use in the hatchery system. Example: 54°F.
(2) Determine date of event and length of fish. As a baseline for the program
projection, the date of spawning of the stock that will serve as parents for
the hatchery stocks should be determined. Example: March 15. Determine
the date of hatching and initial feeding. Because water temperatures in this
example will be approximately 54°F, calculate Daily Temperature Units
(DTU) as follows: 54T-32°F = 22 DTU per day. (The standard basis for
calculating temperature units is 32°F.) Determine days to hatch, if 300
DTU are required to hatch eggs: 300 DTU ^ 22 DTU = 14 days. Adding
14 days to March 15 makes the expected hatching date March 29. Deter-
mine the day to begin feeding, if 40 DTU are required for hatched fry to
develop to feeding stage: 40 DTU -^ 22 DTU = 2 days. This results in an
anticipated feeding date of April 1. In this example, 12,000,000 fry are to
be released immediately to begin natural feeding in a rearing pond, leaving
HATCHERY REQUIREMENTS 55
3,000,000 fry in the hatchery. Final release in this example calls for
1,000,000, 2:7-inch fingerlings. Determine the date fish will reach this size.
A search of the literature indicates that fry begin feeding at a length of 0.2
inch. By a method described in Chapter 2, the growth is projected; the fish
will average 2.6 inches on June 15. (For convenience, all releases have been
assumed to fall on either the first or fifteenth of a month.)
(3) Determine weight. Fish lengths can be converted to pounds from the
length/weight tables provided in Appendix I.
(4) Determine the number of fish or eggs required to attain desired production.
For example, to determine requirements on June 1 for a release of
1,000,000 on June 15, use one-half the monthly anticipated mortality (7.5%
in our example). Convert this to survival: 100% — 7.5% = 92.5%, or 0.925.
Divide the required number of fish at the end of the period by this survival
to determine the fish needed on June 1: 1,000,000-0.925= 1,081,000. This
can be rounded to 1.1 million for planning purposes.
(5) Determine total weight. Total weight is determined by multiplying
weight per fish (Appendix l) by the number of fish on that date.
(6) Determine flow requirements. Adequate biological criteria must be
developed for the species of fish being programmed before flow rates can
be calculated. For this example a value of 1 gallon per minute per 10
pounds of fish was used. Because there is a total weight of 3,850 pounds,
3,850^10 = 385 gallons per minute are required. Flow requirements for in-
cubation are based upon 1 gallon per minute per jar.
(7) Determine rearing space. All density determinations follow the same
method described for Density Index determinations in Chapter 2. Biologi-
cal criteria must be developed for each species of fish being programmed.
Bibliography
American Public Health Association, American Water Works Association, and Water Pollu-
tion Control Federation, 1971. Standard methods for the examination of water and
wastewater, 13th edition. American Public Health Association, Washington, D.C. 874
P-
Andrews, James W., Lee H. Knight, and Takeshi Mural 1972. Temperature requirements
for high density rearing of channel catfish from fingerling to market size. Progressive
Fish-Culturist 34(4):240-241.
Banks, Joe L., Laurie G. Fowler, and Joseph W. Elliott. 1971. Effects of rearing tem-
perature on growth, body form, and hematology of fall chinook fingerlings. Progressive
Fish-Culturist 33(l):20-26.
Baummer, John C, Jr., and L. D. Jensen. 1969. Removal of ammonia from aquarium water
by chlorination and activated carbon. Presented at the 15th Annual Professional
Aquarium Symposium of the American Society of Ichthyologists and Herpetologists.
Bonn, Edward W., Willl\m M. Bailey, Jack D. Bavless, Kim E. Erickson, and Robert
E. Stevens. 197fi. Guidelines for striped bass culture. Striped Bass Committee, South-
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56 FISH HATCHERY MANAGEMENT
Bovi), Claude E. 1!)7;). Water quality in warmwater fish ponds. Agricultural Experimental
Station, Auburn University, Auburn, Alabama. 3.')i) p.
Brki I", J. R. \932. Temperature tolerance in young Pacific salmon, Genus Oncorhynchus. Jour-
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Water Pollution Research, US Department of Health Education and Welfare, Public
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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.
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HATCHERY REQUIREMENTS 57
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58 FISH HAIX'HKRY MANAGEMENT
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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
0 5
^
\
1 3
5 1
0 1
5 2
0 2
5 3
0 3
5 4
0 4
5 5
0
AVERAGE WEIGHT IN GRAMS
Figure 24. Effect of fish size on maximum loading density of
salmon, expressed as pounds of fish per cubic foot of water.
(From Burrows and Combs 1968.)
451
401
5
o
351
E 30
o
<
o
X
CO
251
20L
15
CO
Q
101
o
Q.
0
HATCHERY OPERATIONS 65
co:
^^:
5g. lOg.
91/lb 45/lb
FISH SIZE
15g.
30/lb
Figure 25. Carrying capacity of oxygen- saturated water
at normal activity level of fingerling chinook salmon as
affected by water temperature and fish size. (Source: Bur-
rows and Combs 1968.)
Catastrophic fish losses because of overloaded rearing facilities are an
ever-present danger in fish hatcheries. Many successful managers have
operated a fish hatchery as an art, making judgements by intuition and ex-
perience. However, there are several quantitative approaches for estimating
carrying capacities in fish hatcheries.
Experience has shown that fish density can be increased as fish increase
in size. Figure 24 demonstrates the increase in density that is possible with
chinook salmon. The carrying capacity of oxygen-saturated water at five
water temperatures and several sizes of chinook salmon fingerlings is
presented in Figure 25. Oxygen is usually the limiting factor at warmer
66 FISH HATCHERY MANAGEMENT
400^
2 4 6
FISH LENGTH IN INCHES
8
Figure 26. The weight of different sized fish that would receive the
same quantity of food (5 pounds) at a Hatchery Constant of 10.
(Source: Piper 1972.)
water temperatures. These two graphs do not depict optimum stocking rates
but rather what we believe to be the maximum loading or density that must
not be exceeded if normal growth rates are to be maintained.
There is a relationship between the amount of feed that can be metabo-
lized in a given rearing situation and the pounds of fish that can be carried
in that rearing unit. There is much support for two major premises
presented by David Haskell in 1955:
1. The carrying capacity is limited by (A) oxygen consumption, and (B)
accumulation of metabolic products.
2. The amount of oxygen consumed and the quantity of metabolic prod-
ucts produced are proportional to the amount of food fed.
Haskell postulated that the accumulation of metabolic products and the
consumption of oxygen are the factors that limit the carrying capacities of
rearing units. If this is true, metabolism is the limiting factor because both
the utilization of oxygen and production of metabolic products are
HATCHERY OPKRATIONS 67
regulated by metabolism. If the carrying capacity of a unit is known for a
particular size and species of fish at any water temperature, then the carry-
ing capacity for another size of the same species held at other water tem-
peratures will be the weight of fish that would consume the same amount
of feed.
FLOW INDEX
The feeding guide developed by Buterbaugh and Willoughby demonstrates
a straight line relationship between the length of fish in inches and percent
body weight to feed (Figure 26). At a Hatchery Constant of 10, 100 pounds
of 2-inch fish will receive the same quantity of food (5 pounds) as 200
pounds of 4-inch fish, or 400 pounds of 8-inch fish. (The Hatchery Con-
stant is explained on page 245.)
Haskell states, "if the carrying capacity of a trough or pond is known for
any particular size of fish at a particular temperature, then the safe carry-
ing capacity for other sizes and temperatures is that quantity of fish which
will require the same weight of feed daily." By Haskell's premise, if 100
pounds of 2-inch fish is the maximum load that can be held in a rearing
tank, then 200 pounds of 4- inch fish, 300 pounds of 6-inch, or 400 pounds
of 8-inch fish also would be maximum loads.
The following formula was derived for a Flow Index, where fish size in
inches was used instead of weight of food fed to calculate the safe carrying
capacity for various sizes of trout.
F=W ^[L XI)
F = Flow Index
W = Known permissible weight of fish
L = Length of fish in inches
/ = Water inflow, gallons per minute
To determine the Flow Index [F], establish the permissible weight of
fish in pounds [W) at a given water inflow (/) for a given size fish [L).
The Flow Index [F) reflects the relationship of pounds of fish per gallons
per minute water flow to fish size.
As an example, 900 pounds of 4- inch trout can be safely held in a race-
way supplied with 150 gallons per minute water. What is the Flow Index?
/■ = 900-(4x 150)
F = 1.5
How do you establish the initial permissible or maximum weight of fish
when calculating the Flow Index? A Flow Index can be estimated by
68 FISH HATCHERY MANAGEMENT
adding fish to a rearing unit with a uniform water flow until the oxygen
content is reduced to the minimum level acceptable for the species at the
outflow of the unit (.5 parts per million recommended minimum oxygen
level for trout). The information required for calculating the Flow Index
can also be determined with an existing weight of fish in a rearing unit by
adjusting the water inflow until the oxygen content is reduced to 5 parts
per million at the outflow of the unit.
The Flow Index can then be used to determine the permissible weight of
any size fish ( W), by the formula: W = F x L x /.
Example: In the previous example, a Flow Index of 1.5 was determined
for a raceway safely holding 900 pounds of 4-inch trout in 150 gallons per
minute water flow, (l) How many pounds of 8-inch trout can be safely
held? (2) How many pounds of 2-inch trout?
(1) W = 1.5X8X 150
W = 1,800 pounds of eight-inch trout
(2) W = 1.5 X2X 150
W = 450 pounds of two-inch trout
Furthermore, when weight of fish is increased or decreased in a raceway,
the water inflow requirement can be calculated by the formula:
1= W ^[F X L).
For example, if 450 additional pounds of 8-inch trout are added to the
above raceway containing 1800 pounds of 8-inch trout, what is the re-
quired water inflow?
/ = (1800 + 450) ^(1.5x8)
/ = 188 gallons per minute water inflow
The Flow Index shown in the example should not be considered a
recommended level for all hatcheries, however, because other environmen-
tal conditions such as water chemistry and oxygen saturation of the water
may influence the holding capacities at various hatcheries.
Table 8, with an optimum Flow Index of 1.5 at 50°F, considers the ef-
fects of water temperature and elevation on the Flow Index. This table is
useful in estimating fish rearing requirements in trout and salmon
hatcheries. For example, a trout hatchery is being proposed at a site 4,000
feet above sea level, with a 55°F water temperature. Production of 4- inch
rainbow trout is planned. How many pounds of 4-inch trout can be safely
reared per gallon per minute water inflow (if the water supply is near 100%
oxygen saturation)?
HATCHERY OPERA IIONS
69
Table 8. flow index related to water temperature and elevation for
trout and salmon, based on an optimum index of f = 1.3 at .'>0°f and '),000
feet elevation. oxygen concentration is assumed to be at or near 100%
saturation. (source: bruce b. cannady, unpublished.)
WATER
TEMPER
ATURE
ELEVATION (FEET)
("F)
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
40
2.70
2.61
2.52
2.43
2.34
2.25
2,16
2.09
2,01
1.94
41
2.61
2.52
2.44
2.35
2.26
2.18
2,09
2.02
1.94
1.87
42
2.52
2.44
2.35
2.27
2.18
2.10
2,02
1.95
1.88
1.81
43
2.43
2.35
2.27
2.19
2.11
2.03
1,!)4
1.88
1.81
1.74
44
2.34
2.26
2.18
2.11
2.03
l.!)5
1,87
1.81
1,74
1.68
45
2.25
2.18
2.10
2.03
1.95
1.88
1,80
1.74
1,68
1.61
46
2.16
2.09
2.02
1.94
1.87
1.80
1,73
1,67
1.61
1.55
47
2.07
2.00
1.93
1.86
1.79
1.73
1,66
1,60
1,54
1.48
48
1.98
1.91
1.85
1.78
1.72
1.65
1,58
1,53
1,47
1.42
49
1.89
1,83
1.76
1.70
1.64
1.58
1.51
1,46
1,41
1.36
50
1.80
1.74
1.68
1.62
l.,56
7.50
1.44
1,39
1,34
1.29
51
1.73
1.67
1.62
1.56
1.50
1.44
1.38
1,34
1,29
1.24
52
1.67
1.61
1.56
1.50
1.44
1.39
1,33
1,29
1,24
1.19
53
1.61
1.55
1.50
1.45
1.39
1.34
1,29
1,24
1,20
1.15
54
1.55
1.50
1.45
1.40
1.34
1.29
1.24
1,20
1,16
1.11
55
1.50
1.45
1.40
1.35
1.30
1.25
1,20
1,16
1,12
1.07
56
1.45
1.40
1.35
1.31
1.26
1.21
1,16
1,12
1,08
1.04
57
1.41
1.36
1.31
1.27
1.22
1.17
1,13
1,09
1.05
1.01
58
1.36
1.32
1.27
1.23
1.18
1,14
1,09
1 ,05
1.02
0.98
59
1.32
1.28
1.24
1.19
1.15
1,10
1,06
1 ,02
0.99
0.95
60
1.29
1.24
1.20
1.16
1.11
1,07
1.03
0,99
0.96
0.92
61
1.25
1.21
1.17
1.13
1.08
1,04
1.00
0,97
0.93
0.90
62
1.22
1.18
1.14
1.09
1.05
1,01
0.97
0,94
0.91
0.87
63
1.18
1.14
1.11
1.07
1,03
0,99
0.95
0,92
0.88
0.85
64
1.15
1.12
1.08
1.04
1.00
0,96
0.92
0,89
0.86
0.83
(1) The Flow Index [F] is 1.30 (Table 8, 4,000 feet elevation, 55°F tem-
perature).
(2) We can now estimate the permissible weight of trout that can be held
per gallon per minute, by the formula W = F >^ L x /, where F=1.30,
L = A inches, and / = 1 gallon per minute. Approximately 5.2 pounds of
trout can be safely reared per gallon per minute water inflow (l.SO x 4 x l).
The effect of water temperature on the Flow Index can readily be seen in
the table. For instance, a hatchery at a 5,000- foot elevation having a water
70 FISH HATCHERY MANAGEMENT
temperature drop from 50° to 46°F would have an increase in Flow Index
from 1.50 to 1.80, because the metabolic rate of the fish normally would
drop and the oxygen concentration would increase with a drop in water
temperature. The reverse would be true with a rise in water temperature.
Although Table 8 is useful for planning and estimating preliminary carrying capa-
city in a trout or salmon hatchery, it should be considered only as a guide and
specific Flow Indexes ultimately should be developed at each individual hatchery.
The table is based on oxygen levels in the inflowing water at or near
100% saturation. If a rise or drop in oxygen occurs, there is a correspond-
ing rise or drop in the Flow Index, proportional to the oxygen available for
growth (that oxygen in excess of the minimum concentration acceptable for
the species of fish being reared).
Example: There is a seasonal drop in oxygen concentration from 11.0 to
8.0 parts per million (ppm) in the water supply of a trout hatchery, and the
minimum acceptable oxygen concentration for trout is 5.0 ppm. The Flow
Index has been established at 1.5 when the water supply contained 11.0
ppm oxygen. What is the Flow Index at the lower oxygen concentration?
(1) With 11 ppm oxygen in the water supply, there is 6 ppm available
oxygen, since the minimum acceptable level for trout is 5 ppm (ll ppm — 5
ppm).
(2) With 8 ppm oxygen in the water supply, there is 3 ppm available ox-
ygen (8 ppm — 5 ppm).
(3) The reduction in Flow Index is the available oxygen at 8 ppm divid-
ed by the available oxygen at 11 ppm or a 0.5 reduction (3 ^ 6).
(4) The Flow Index will be 0.75 at the lower oxygen concentration
(1.5x0.5).
Table 9 presents dissolved oxygen concentrations in water at various tem-
peratures and elevations above sea level. The percent saturation can be cal-
culated, once the dissolved oxygen in parts per million is determined for
the water supply.
Many hatcheries reuse water through a series of raceways or ponds and
the dissolved oxygen concentration may decrease as the water flows
through the series. As a result, if aeration does not restore the used oxygen
to the original concentration, the carrying capacity will decrease through a
series of raceways somewhat proportional to the oxygen decrease. The car-
rying capacity or Flow Index of succeeding raceways in the series can be
calculated by determining the percent decrease in oxygen saturation in the
water flow, but only down to the minimum acceptable oxygen concentration for the
fish species.
Calculations of rearing unit loadings should be based on the final
weights and sizes anticipated when the fish are to be harvested or loadings
hatchery operations 71
Table 9. dissolved oxygen in parts per million for fresh water in equili-
brium WITH air. (SOURCE: LEITRITZ AND LEWIS 1976.)
TEMPER-
ELEVATION
IN FEET
ATURE
("F)
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
40
13.0
12.5
12.1
11.6
11.2
10.8
10.4
10.0
9.6
9.3
9.0
45
12.1
11.7
11.2
10.8
10.5
10.1
9.7
9.3
9.0
8.7
8.4
46
11. ;»
11..')
11.1
10.7
10.3
9.9
9.6
9.2
8.9
8.()
8.3
47
n.8
11.3
10.9
10.5
10.2
9.8
9.4
9.1
8.8
8.5
8.2
48
11. (i
11.2
10.8
10.4
10.0
9.7
9.3
9.0
8.7
8.3
8.0
49
11.5
11.1
10.6
10.3
i).9
9.5
9.2
8.9
8.6
8.2
7.9
50
11.3
10.9
1U.5
10.1
9.8
9.4
9.1
8.7
8.4
8.1
7.8
51
11.2
10.8
10.4
10.0
9.7
9.3
9.0
8.6
8.3
8.0
7.7
52
11.0
10.6
10.2
9.9
9.5
9.2
8.9
8.5
8.2
7.9
7.6
53
10.9
10.5
10.1
9.8
9.4
9.1
8.7
8.4
8.1
7.8
7..")
54
lO.K
10.4
10.0
9.6
9.3
9.0
8.6
8.3
8.0
7.7
7.4
55
10.()
10.3
9.9
9.5
9.2
8.9
8.5
8.2
7.9
7.6
7.3
60
10.0
9.6
9.3
8.9
8.6
8.3
8.0
7.7
7.4
7.1
6.8
65
9.4
9.1
8.8
8.4
8.1
7.8
7.5
7.2
7.0
6.7
6.4
70
9.0
8.7
8.4
8.0
7.8
7.4
7.2
6.9
6.7
6.4
6.1
75
8.6
8.3
8.0
7.7
7.4
7.1
6.8
6.5
6.3
6.1
5.8
reduced. In this way, maximum rearing unit and water flow requirements
will be delineated and frequent adjusting of water flows or fish transfers
can be avoided.
Generally, these methods are limited to intensive culture of fish in situa-
tions where oxygen availability is regulated by the inflowing water. In ex-
tensive culture systems involving large ponds, oxygen availability depends
to a greater extent on oxygen replacement through the surface area of the
water. Water inflow in such situations is not as significant as pond surface
area and water volume in determining carrying capacity.
Estimates of oxygen consumption under intensive cultural conditions
have been determined for channel catfish. Oxygen consumption rates de-
cline as the available oxygen decreases, and there is a straight- line (semi-
log) relationship between fish size and oxygen consumption; smaller fish
require more oxygen per unit size than larger fish (Figure 27).
The data in Figure 27 can be used to estimate the carrying capacity for
channel catfish if the available oxygen in a rearing unit is determined. Ox-
ygen consumption will change proportionately as the water temperature in-
creases or decreases.
DENSITY INDEX
Carrying capacity has been discussed in relation to water inflow or, more
specifically, oxygen availability. What affect does density, as pounds of fish
72
FISH HATCHERY MANAGEMENT
>-
<
Q
X
to
C/5
OQ
O
O
4.5
4.0
3.5
3.0
2.5
2.0
1.5
o
CO
0.51
_L
_L
4 5 6
LENGTH IN INCHES
10
Figure 27. Oxygen consumption of well-fed and fasted channel
catfish at 79°F water temperature. Environmental oxygen levels were
6-7 ppm. (Modified from Andrews and Matsuda 1975.)
per cubic foot of rearing space, have on carrying capacity? Economic con-
siderations dictate that the loading density be maintained as high as is
practical. However, a reduction in density of fish has been reported by
some fish culturists to result in better quality fish, even though there was
no apparent environmental stress in their original crowded situation.
Most carrying capacity tables are based on the maximum fish load possi-
ble without excessive dissolved oxygen depletion, and ignore the pathogen
load of the water supply. It is known that in steelhead rearing ponds,
parasites apparently cannot be controlled by formalin treatments if the
loading exceeds seven to eight pounds of fish per gallon of water per
minute at 60-70°F. Carrying capacities that include disease considerations
and are conducive to optimum health of spring chinook and coho salmon
are shown for standard 20 x 80- foot raceways in Table 10.
This information supports the principle that as fish size increases, fish
loading can be increased proportionally. An example of this principle is shown
HATCHERY OPERATIONS
73
in Figure 28. There is no effect on the rate of length increase or food
conversion of rainbow trout as fish density increases from less than I to 5.6
pounds per cubic foot.
A rule of thumb that can be used to avoid undue crowding is to hold
trout at densities in pounds per cubic foot no greater than 0.5 their length
in inches (i.e., 2-inch fish at one pound per cubic foot, 4-inch fish at two
pounds per cubic foot, etc.). A density index can be established that is the
proportion of the fish length used in determining the pounds of fish to be
held per cubic foot of rearing space. Fish held at densities equal to one- half
00
cc
CO
CD
CO
o
CJ)
co'
LlJ
53
C3
^/
/
/
/
/■
^y
V
.^v
^
5^
/
X'
y
.-'\
r
^ y \ CONVERSION
j_
_L
8 12 16 20
BIWEEKLY GROWTH PERIODS
24
Figure 28. Relationship of cumulative length increase, food
conversion, and pounds per cubic foot (ft ) of rainbow trout
reared in aluminum troughs for 10 months. (Source: Piper
1972.)
74 fish hatchery management
Table 10. recommended hatchery pond loadings (pounds of fish per gal-
lon PER MINUTE INFLOW), BASED ON DISEASE CONSIDERATIONS, FOR CHINOOK
AND COHO SALMON HELD IN 80 x 2()-FOOT PONDS. THE VALUES REPRESENT FINAL
POND OR RACEWAY LOADINGS AT TIME OF RELEASE OR HARVEST FOR FISH SIZES OF
1000 FISH PER POUND AND LARGER. LOADINGS SHOULD NOT EXCEED THE TABLE
VALUE BEFORE TIME OF RELEASE. INFORMATION IS NOT AVAILABLE FOR OTHER
TEMPERATURES, SIZES, OR SPECIES OF FISH. (SOURCE: WEDEMEYER AND WOOD 1974.)
WATER
FISH SIZE
(NUMBER PER POUND)
TEMPERA-
TURES (°F)
1,000
500
100
50
33
25
15
Coho salmon
38
3.5
5.0
8.0
11.0
15.0
20.0
25.0
48
2.7
4.0
6.0
10.0
14.0
16.0
18.0
58
2.2
3.0
4.5
7.0
10.0
12.0
15.0
63
2.0
3.5
5.0
7.0
9.0
10.0
68
1.5
2.0
3.0
3.0
4.0
Fall and spring chinook salmon
38
3.0
4.0
6.0
8.0
11.0
12.0
13.0
48
2.5
3.0
5.0
6.5
9.0
10.0
11.0
58
2.0
2.2
3.5
4.5
6.0
7.5
9.0
63
1.2
3.0
3.5
4.0
5.0
5.5
their length have a density index equal to 0.5. A useful formula to avoid
overcrowding raceways is:
W = D X FXZ.
Where W = Permissible weight of fish
D = Density index (0.5 suggested for trout)
V = Volume of raceway in cubic feet
L = Fish length in inches
Raceway or pond volume requirements can be calculated with the for-
mula:
V=W^{D XL).
Volumes of circular tanks can be determined from Table C- 1 in Appendix
C.
This concept of space requirement assumes that the Density Index
remains constant as the fish increase in length. In reality, larger fish may
be able to tolerate higher densities in proportion to their length. This
method has proved to be a practical hatchery management tool, nonethe-
less, and can be used with any species of fish for which a Density Index
has been determined.
HATCHERY OPERATIONS 75
Warmwater Fish Rearing Densities
Channel catfish have been reared at densities of up to eight pounds per cu-
bic foot of water. Stocking density and water turnover both had substantial
effects on growth and food conversion. Reduced growth due to the increase
in stocking density was largely compensated by increased water exchange,
and growth rate data indicated that production of over 20 pounds per cu-
bic foot of water was possible in a 365-day period. High-density culture of
catfish in tanks or raceways can be economical if suitable environmental
conditions and temperatures are maintained.
Fish weight gain, food utilization, and survival may decrease as fish den-
sity increases, but faster water exchanges (inflow) will benefit high stocking
densities. The best stocking densities and water exchange rates will take
into consideration the various growth parameters as they affect the
economics of culturing channel catfish. Stocking densities between five and
10 fish per cubic foot have been suggested as feasible and production can
be increased to higher densities by increasing the oxygen content with
aeration, if low oxygen concentration is the limiting factor.
Acceptable stocking densities for warmwater fish are related to the type
of culture employed (intensive or extensive) and the species cultured. The
appropriate density is influenced by such factors as desired growth rate,
carrying capacity of the rearing facility, and environmental conditions.
Most warmwater fish, other than catfish, normally are cultured extensively.
The following paragraphs cover representative species of the major groups
of commonly cultured warmwater and coolwater fishes. Stocking rates for
related species can be estimated from these examples.
LARGEMOUTH BASS
Production methods used for largemouth bass are designed to supply 2-
inch fingerlings.
Fry are stocked in prepared rearing ponds at rates varying from 50,000
to 75,000 per acre. If a fingerling size larger than 2 inches is desired, the
number of fry should be reduced. Normal production of small bass ranges
from 30 to 150 pounds per acre depending on the size fish reared, the pro-
ductivity of the rearing pond, and the extent to which natural food has
been consumed and depleted.
The length of time required for the transferred fry to grow to a harvest-
able size depends mainly upon the prevailing water temperature and the
available food supply. Normally, it is 20-30 days in southeastern United
States at a temperature range of 65-75°F. A survival rate of 75 to 90% is
acceptable. A higher survival suggests that the number of fry stocked was
estimated inaccurately. Less than 75% survival indicates a need for
7fi FISH HATCHERY MANAGEMENT
improved enumeration technique, better food production, or control of
disease, predators, or competitors.
Production of 3- to 6-inch bass fingerlings requires careful attention to
size uniformity of the fry stocked. The number of fry stocked is reduced by
75 to 90"(i below that used for 2-inch bass production. Growth past a size
of 2 inches must be achieved mainly on a diet of immature insects, mainly
midges. If a size larger than 4 inches is needed, it will be necessary to pro-
vide a forage fish for the bass. There are no standard procedures for this,
but one method is to stock 17-inch bass at a rate of 1,000 per acre into a
pond in which fathead minnows had been stocked at a rate of 2,000 per
acre 3 or 4 weeks previously. The latter pond should have been fertilized
earlier with organic fertilizer and superphosphate so that ample zooplank-
ton will have developed to support the minnows. The minnows are allowed
to grow and reproduce to provide feed for the bass when they are stocked.
If weekly seine checks show that the bass are depleting the supply of
forage fish, additional minnows must be added to the pond. Variable
growth among bass fingerlings is common but if some fingerlings become
too much larger than others, cannibalism can cause heavy losses. If this
occurs, the pond must be drained and the fingerlings graded.
BLUEGILL
Numerically, bluegills and redear sunfish are the most important of the cul-
tured warmwater fishes. Generally, spawning and rearing occurs in the
same pond, although some fish culturists transfer fry to rearing ponds for
one reason or another.
In previously prepared ponds, broodstock bluegills 1 to 3 years old are
stocked at a rate of 30 to 40 pairs per acre. Spawning- rearing ponds for
bluegills can be stocked in the winter, spring, or early summer. About 60
days are required to produce harvestable-size fingerlings under average
conditions.
CHANNEL CATFISH
Channel catfish reared in ponds are stocked at a rate of 100,000 to 200,000
fry per acre. At these rates, survival should be 80%, and 3- to 4- inch finger-
lings can be produced in 80 to 120 days if there is adequate supplemental
feeding. Stocking at a higher rate reduces the growth rate of fingerlings. A
stocking rate of 40,000 to 50,000 per acre yields 4- to 6- inch fingerlings in
80-120 days if growth is optimum.
Although channel catfish can be reared on natural food, production is
low compared to that obtained with supplemental feeding. A well- fertilized
pond should produce 300-400 pounds of fingerling fish per acre, with no
HATCHERY OPERATIONS 77
supplemental feeding. Up to 2,000 pounds or more of fingerling fish per
acre can be reared with supplemental feeding.
If fish larger than 4 inches are desired, stocking rates must be reduced.
Experimental evidence suggests that 1,500, 3- to 6-inch fingerlings per acre
will produce 1- pound fish in 180 days.
HIGH-DENSITY CATFISH CULTURE
Specialized catfish culture systems have received much publicity in recent
years, and several high-density methods are currently under investigation.
These include the use of cages; earthen, metal, or concrete raceways; vari-
ous tank systems; and recirculation systems. High-density fish culture
demands not only highly skilled and knowledgeable management but also
requires provision of adequate amounts of oxygen, removal of wastes, and a
complete high-quality diet. The methods used for calculating carrying
capacity in salmonid hatcheries can readily be used for intensive culture of
catfish.
STRIPED BASS
At present, most striped bass rearing stations receive fry from outside
sources. Eggs are collected and usually hatched at facilities located near
natural spawning sites on the Atlantic coast. Fry are transferred to the
hatchery at 1 to 5 days of age. There they are either held in special tanks
or stocked in ponds for rearing, depending on the age of the fry and
whether or not they have sufficiently developed mouth parts to allow
feeding.
Earthen ponds are fertilized before stocking to produce an abundance of
zooplankton. In these prepared ponds, striped bass fry are stocked at a rate
of 75,000 to 125,000 per acre. A stocking density of 100,000 fry per acre,
under normal growing conditions, yields 2-inch fingerlings in 30 to 45
days. Survival is very erratic with this species, and may vary from 0 to
100% among ponds at the same hatchery. As with most pond-cultured fish,
the growth rate of striped bass increases as the stocking density decreases.
If a 3- inch fingerling is needed, the stocking density should be reduced to
60,000 to 70,000 fry per acre.
Culture of striped bass larger than 3 inches usually requires feeding for-
mulated feeds. Striped bass larger than 2 inches readily adapt to formulat-
ed feeds, and once this has taken place most of the procedures of trout cul-
ture can be applied.
NORTHERN PIKE AND WALLEYE
These coolwater species represent a transition between coldwater and
warmwater cultural methods. A combination of extensive and intensive
78 FISH HATCHERY MANAGEMENT
culture is applied. Fry are usually stocked in earthen ponds that have been
prepared to provide an abundance of zooplankton. Fry are stocked at den-
sities of 50,000 to 70,000 per acre to produce 2- inch fingerlings in 30 to 40
days. Because of the aggressive feeding behavior of these species, especially
northern pike, care must be taken not to let the zooplankton decline or
cannibalism will occur and survival will be low. At a size of 2 to 3 inches
these fish change from a diet of zooplankton and insect larvae to one
predominantly of fish. At this stage, the fingerlings usually are harvested
and distributed. If fish larger than 2 to 3 inches are desired, the fingerlings
can be restocked into ponds supplied with a forage fish. Stocking rates do
not normally exceed 20,000 per acre, and generally average about 10,000
to 15,000. As long as forage fish are present in the pond, northern pike and
walleyes can be reared to any size desired. As the fish become larger, they
consume more and larger forage fish. Northern pike and walleyes are
stocked at lower densities if they are to be raised to larger sizes. Stocking
densities of 10,000 to 20,000 fingerlings per acre are used to rear 4- to 6-
inch fingerlings; 5,000 to 10,000 per acre for 6- to 8-inch fish; and usually
less than 4,000 per acre for fish 8 inches or larger.
This method of calculating carrying capacities of ponds or raceways ig-
nores the effects of accumulative metabolic wastes. Where water is reused
through a series of raceways, the Flow Index would remain fairly constant,
but metabolic products would accumulate.
Inventory Methods
The efficient operation of a fish hatchery depends on an accurately main-
tained inventory for proper management. Whether weight data are applied
directly to the management of fish in the rearing units or used in an ad-
ministrative capacity, they are the criteria upon which most hatchery prac-
tices are based.
Hatchery procedures that are based upon fish weight include feed calcu-
lations, determination of number per pound and fish length, loadings of
distribution trucks for stocking, calculations of carrying capacities in rear-
ing units, and drug applications for disease control.
Administrative functions based upon weight of fish include preparation
of annual reports, budgeting, estimating production capability of rearing fa-
cilities, recording monthly production records, feed contracting, and plan-
ning for distribution (stocking).
Some managers inventory every two or three months to keep their pro-
duction records accurate; others use past record data to project growth for
several months and obtain a reasonable degree of accuracy. An inventory is
essential after production fish have been thinned and graded, and one
HATCHERY OPERATIONS 79
should be made whenever necessary to assure that records provide accurate
data. In any inventory, it is imperative that fish weights be as accurate as
possible.
INTENSIVE CULTURE
Fish can be weighed either by the wet or dry method. The wet method in-
volves weighing the fish in a container of water that has been preweighed
on the scale. Care must be exercised that water is not added to the
preweighed container, nor should water be splashed from it during weigh-
ing of the fish. This method is generally used with small fish. Dry weigh-
ing is a popular method of inventorying larger fish. The dip net is hung
from a hook at the bottom of a suspended dial scale. The scale should be
equipped with an adjusting screw on the bottom, so the weight of the net
can be compensated for. Dry weighing eliminates some fish handling and,
with a little practice, its accuracy is equal to that of wet weighing.
The most common ways to determine inventory weights are the sample-
count, total-weight, and pilot-tank methods.
In the sample-counting method, the total number of fish is obtained ini-
tially by counting and weighing the entire lot. In subsequent inventories, a
sample of fish is counted and weighed and either the number per pound or
weight per thousand is calculated (Figure 29). To calculate the number per
pound, divide the number of fish in the sample by the sample weight. To
calculate the weight per thousand, divide the sample weight by the number
of fish (expressed in thousands). The total weight of fish in the lot then is
estimated either by dividing the original total number of fish (adjusted for
recorded mortality) by the number per pound or by multiplying it (now
expressed in thousands) by the weight per thousand. This method can be
inaccurate, but often it is the only practical means of estimating the weight
of a group of fish. To assure the best possible accuracy the following steps
should be followed:
(1) The fish should be crowded and sampled while in motion.
(2) Once a sample of fish is taken in the dip net, the entire sample
should be weighed. This is particularly true if the fish vary in size. The
practice of weighing an entire net full of fish will obtain more representa-
tive data than that of weighing preset amounts (such as 5 or 15 pounds).
Light net loads should be taken to prevent injury to the fish or smothering
them.
(3) When a fish is removed from water it retains a surface film of water.
For small fish, the weight of the water film makes up a larger part of the
observed weight than it does for larger fish. The netful of fish should be
carefully drained and the net bottom wiped several times before the fish
are weighed.
80
FISH HATCHERY MANAGEMENT
Figure 29. Muskellunge fry being sample-counted for inventory. (Courtesy
Wisconsin Department of Natural Resources.)
(4) Several samples (at least five) should be taken. If the calculated
number of fish per pound (or weight per 1,000) varies considerably among
samples, more samples should be taken until there is some consistency in
the calculation. Then the sample values can be averaged and applied to the
total lot; all samples should be included in the average. Alternatively, the
counts and weights can be summed over all the samples, and an overall
number per pound computed. Larger samples are required for large fish.
Even with care, the sample-count method can be as high as 15-20% inac-
curate. Some fishery workers feel it is necessary to weigh as much as 17%
of a population to gain an accuracy of 5-10%. Hewitt (l948) developed a
quarter-sampler that improved the accuracy of the sample count method
(Figure 30).
In the total-weight method, as the name implies, all of the fish in a lot
are weighed, thus sampling error is avoided. Initial sample counting must
be conducted during the first weighing to determine the number of fish in
the lot, but this is done when the fish are small and more uniform in size.
This method involves more work in handling the fish, but is the most accu-
rate method of inventorying fish.
HATCHERY OPERATIONS
81
The pilot- unit method utilizes a tank or raceway of fish maintained to
correspond to other tanks or raceways of the same type. The pilot unit is
supplied with the same water source and flow, and the fish are fed the
same type and amount of food per unit of body weight. All the fish reared
in the pilot unit are weighed and the gain in weight is used to estimate the
fish weight in the other rearing units. This method is more accurate than
sample counting for fish up to six inches long.
EXTENSIVE CULTURE
Fish grown in ponds are relatively inaccessible and difficult to inventory
accurately before they finally are harvested. Pond fish still are sampled fre-
quently, as they are in raceway culture, but the value of such sampling is
Figure 30. A quarter- sampler can be used to accurately estimate the number of
fish per pound or weight per thousand fish, (l) A framed net with four remov-
able pockets in the bottom is designed to fit snugly in a large tub of water. (2)
Several netfuls of fish are put in the tub and when the frame is removed the fish
are divided into four uniform samples. (3) Only one-quarter of the" fish are actu-
ally used in the sampling. The fish are counted and then weighed. (4) A modi-
fied frame design has one of the net pockets closed (arrow) and the other three
open. As the frame is lifted out of the tub the fish in the closed pocket are
retained for counting. It is felt that a sample taken in this manner, from several
netfuls of fish, reduces bias in sampling. (FWS photos.)
82 FISH HATCHERY MANAGEMENT
Figure 31. Pond fish being sampled with a lift net. The fish are
attracted to the area with bait.
as much to determine the condition and health of the fish, to adjust feed
applications, and to estimate harvest dates, as it is to estimate growth and
survival. Usually, it is impractical to concentrate all fish in a pond to-
gether, so sampling is done on a small fraction of the population. Numeri-
cal calculations based on such small samples may be biased and unreliable
except as general guidelines.
One way to sample pond fish is to attract them with bait and then cap-
ture them, as with a prelaid lift net (Figure 3l). The problem with this
technique is that fish form dominance hierarchies, and the baited area
quickly becomes dominated by the larger and more vigorous individuals.
This will bias the sample.
Most pond samples are taken with seine nets. Such samples can be ex-
trapolated to the whole pond if the seine sweeps a known area, if few fish
escape the net, and if the population is distributed uniformly throughout
the pond. The area swept by the net can be calculated with little difficulty;
HATCHERY OPERATIONS 83
however, fish over 3 inches long can outrun the pulled seine, and are likely
to escape, leaving a nonrepresentative sample. This problem can be partial-
ly overcome by setting the net across, or pulling it into, a corner of the
pond instead of pulling it to a straight shore. The uniformity of fish distri-
bution is the most difficult aspect to determine. Many species form aggre-
gations for one reason or another. A seine might net such a cluster or the
relatively empty space between them. It helps to sample several areas of
the pond and to average the results, although this is time-consuming, and
seines rarely reach the pond center in any case.
Fish can be concentrated for sampling if the pond is drawn down. This
wastes time — it can take two or three days to empty a pond of several
acres — and a lot of water. It also can waste a lot of natural food production
in the pond. Unless fish have to be concentrated for some other purpose,
such as for the application of disease-control chemicals, ponds should not
be drawn down for sampling purposes.
In summary, pond fish should be sampled regularly, but the resulting in-
formation should be used for production calculations only with caution.
Fish Grading
Fish grading — sorting by fish length — makes possible the stocking of uni-
formly sized fish if this is necessary for fishery management programs. Also,
it reduces cannibalism in certain species of fish; some, such as striped bass
and northern pike, must be graded as often as every three weeks to prevent
cannibalism. Grading also permits more accurate sample counting and in-
ventory estimates by eliminating some of the variation in fish size. An ad-
ditional reason for grading salmon and steelhead is to separate smaller fish
for special treatment so that more of the fish can be raised to smolt size by
a specified time for management purposes (Figure 32).
In trout culture, good feeding procedure that provides access to food by
less aggressive fish can minimize the need for grading. However, grading of
fish to increase hatchery production by allowing the smaller fish to increase
their growth rate is questionable. Only a few studies have demonstrated
that dominance hierarches suppress growth of some fish; in most cases,
segregation of small fish has not induced faster growth or better food utili-
zation. In any fish population there are fish that are small because of their
genetic background and they will remain smaller regardless "of opportuni-
ties given them to grow faster.
In warmwater culture — and extensive culture generally — fish usually
cannot be graded until they are harvested. Pond-grown fish can vary great-
ly in size, and they should be graded into inch-groups before they are dis-
tributed. Products of warmwater culture often are sold in small lots to
84 FISH HATCHERY MANAGEMENT
several buyers, who find them more attractive if the fish are of uniform size
within each lot.
A number of commercial graders are available. Mixed sizes of fish may
require grading through more than one size of grader. Floating grading
boxes with panels of metal bars on the sides and bottom are commonly
used in fish hatcheries. Spacing between the bars determines the size of
fish that are retained; fish small enough to pass between the bars escape.
The quantity of fish in the grader at any one time should not exceed five
pounds per cubic foot of grader capacity. Small fish can be driven from the
grader by splashing the water inside the grader with a rocking motion.
Recommended grader sizes for such warmwater fish as minnows and
channel catfish are as follows:
Minnows Channel catfish
Spacing Length Spacing Length
between offish between offish
bars held bars held
(inches) (inches) (inches) (inches)
±1
u
27
3
M
I
(i4
(>4
4
11
(i4
4
11
64
2
40
(i4
5
ii
(i4
21
4
Al
1)4
6
Al
M
21
2
11
fi4
7
ill
(i4
21
4
(i4
8
A lT;-inch grader will retain j-1-pound channel catfish. Catfish pass
most readily through the bottom of a grader and minnows through the
sides.
Fish Handling and Harvesting
Handling of fish should be kept to a minimum to avoid injury and stress
that can lead to disease or death. Losses from handling can be substantial,
but they do not always occur immediately and can go unnoticed after the
fish have been stocked in natural waters.
An adequate supply of oxygen must be provided in the raceway or pond
during harvest, and during transit in containers. Silt and waste material
such as feed and feces in the water should be avoided or kept to a
minimum. Overloading nets or containers will abrade the skin of the fish.
Extremes in water temperature should be avoided in the hauling containers
and between rearing units. Sudden changes in water temperature of 6°F or
HATCHERY OPERATIONS
85
Figure 32. A mechanical crowder used in concrete rearing ponds with an adjust-
able Wilco grader mounted on the crowder frame. (Courtesy California Department
of Fish and Game.)
greater have adverse effects on most fishes. The use of l-3'/^i saline solution
for handling and moving fish has been recommended by some fishery
workers to reduce handling stress. Containers should be full of water. If the
water cannot slosh, fish will not be thrown against the sides of the
container.
A dip net and tub can be used to avoid physical damage when small
poundages of fish are moved. Large- meshed nets should be avoided, partic-
ularly when scaled fish are involved. Nets used for catfish commonly are
treated with asphaltum or similar substances to prevent damage due to
spine entanglement.
Many warmwater fish hatcheries comprise a number of earthen ponds
that normally are harvested through a combination of draining and seining
(Figure 33). When large poundages of fish are present, a substantial portion
is removed by seining before the pond is lowered. The remainder are then
easily harvested from collection basins (Figure 34). Small fihgerlings are
harvested by lowering the pond water level as rapidly as possible without
stranding the fish or catching them on the outlet screen.
If the contents of a pond cannot be removed in one day, the pond
should be partially refilled for overnight holding. Holding a partially har-
vested pond at a low level for long periods of time should be avoided
86
FISH HATCHERY MANAGEMENT
Figure 33. Marketable size catfish being graded and harvested from a large
earthen pond (Fish Farming Experimental Station, Stuttgart, Arkansas).
because this increases loss to predators and the possibility of disease.
Crowding and the lack of food also will reduce the ability of small fish to
withstand handling stress. A fresh supply of water should be provided
while the fish are confined to the collection basin.
Although harvesting the fish crop by draining the pond has the major
advantage of removing the entire crop in a relatively short time, trapping is
another popular harvesting technique. The advantages associated with trap-
ping include better overall condition of the fish, because they are collected
in silt-free water; reduced injury, because the fish are handled in small
numbers; avoidance of pond draining; successful harvesting in vegetated
ponds; avoidance of nuisance organisms such as tadpoles and crayfish; and
reduced labor, as one person can operate a trap successfully. The major
disadvantage to trapping is it does not supply a reliably large specified
number of fish on a given date.
The most widely used trap on warmwater fish hatcheries is the V-trap
(Figure 35). Successful trapping requires knowledge of the habits of the
fish and proper positioning of the device. The trap usually is used in com-
bination with pond draining; it is positioned in front of the outlet screens
and held away from them, against the water current, by legs or some other
means. The trap is constructed so it floats with about 10% above the water
HATCHERY OPERATIONS
87
surface and 90% below. As the pond is drained the trap simply falls with
the water level. Fish are attracted to the outlet screen for a number of rea-
sons, the two main ones being the water current and the abundance of food
organisms that are funneled there. Some species of fish are attracted to
fresh cool water, and a small stream of this should be introduced near the
trapping area if possible. The fish attracted to the area have to swim
against the outgoing current to keep from being pulled against the outlet
screen. They rest behind a glass plate that shields them from the current;
following this glass they come into the trap, from which they can periodi-
cally be harvested with a small net.
The trap is used in another manner for harvesting small fish. The
advanced fry and early fingerlings of many species, such as largemouth
bass, smallmouth bass, and walleye run the shoreline of ponds in schools of
varying numbers. To collect them, the trap is fixed far enough out in the
pond that the fry swim between it and the shore. A wire screen lead run-
ning from the mouth of the trap to the shore, and extending from the
water surface to the pond bottom, intercepts the fish. As they attempt to
get around the lead, the fish follow it toward deep water and into the trap.
Four such traps set around a pond have caught up to 80% of the available
largemouth bass fry.
Figure 34. Removing fish from a collection basin in an earthen pond.
88
FISH HATCHERY MANAGEMENT
Figure 35. Diagram of a V-trap. Fish follow the wire screen into the V and
enter the cage, where it is difficult for them to find a way back out through the
narrow opening in the V.
Physical characteristics of earthen ponds play an important part in the
efficient harvest of fish. Removal of all stumps, roots, and logs is necessary
for harvesting with seines. The pond bottom should be relatively smooth to
provide adequate and complete drainage. Low areas that will not drain to-
wards the collection basin should be avoided.
Rearing Unit Management
Sanitation
Sanitation is an important phase of any animal husbandry. A number of
undesirable situations can arise when waste feed and fecal material collect
in rearing units. If fish feed falls into waste material on the pond or race-
way bottoms, fish will generally ignore it and it will be wasted. Excessive
feces and waste food harbor disease organisms and can accumulate in the
mucus of the gills, especially during disease outbreaks. Disease treatment is
also difficult in filthy rearing units because treatment chemicals may react
with the organic matter, reducing the potency of the chemical. The waste
material may become stirred up as the chemical is mixed in the water; this
can be hazardous to the gills of the fish. Tanks, troughs, and raceways
must be cleaned frequently, whatever species — cold-, cool-, or warm-
water — is grown in them.
In large earthen ponds, accumulated waste may reduce the oxygen con-
tent of the water. This can become a severe problem during periods of re-
duced water flow in the warm summer months.
HATCHERY OPERATIONS 89
Most fish diseases are water-borne and are readily transferred from one
rearing unit to another by equipment such as brushes, seines, and dip nets.
All equipment used in handling and moving fish can be easily sanitized by
dipping and rinsing it in a disinfectant such as Roccal, Hyamine, or so-
dium hypochlorite. Solutions of these chemicals can be placed in containers
at various locations around the hatchery. Separate equipment should be
provided for handling small fish in the hatchery building and should not
be used with larger fish in the outside rearing units. Detailed procedures
for decontaminating hatchery facilities and equipment are presented in
Chapter 5.
Dead and dying fish are a potential source of disease organisms and
should be removed daily. Empty rearing units should be cleaned and
treated with a strong solution of disinfectant and then flushed before being
restocked. Direct sunshine and drying also can help sanitize rearing units.
If possible, ponds and raceways should be allowed to air-dry in the sun for
several weeks before they are restocked. To prevent long-term buildup of
organic matter, ponds typically are dried and left fallow for two to five
months after each harvest. Many times, the pond bottoms are disked,
allowing the organic matter to be oxidized more quickly. After the pond
soil has been sun-baked, remaining organic material will not be released
easily when the pond is reflooded.
Disinfection of warmwater fish ponds is a process by which one or more
undesirable forms of plant and animal life are eliminated from the environ-
ment. It may be desirable for several reasons: disease control; elimination
of animal competitors; destruction of aquatic weeds, among others. Disin-
fection may be either partial or complete, according to the degree to which
all life is eliminated. It is impractical, if not impossible, to achieve com-
plete disinfection of eathern ponds.
Disinfection of ponds with lime is a common practice, especially in Eu-
rope. This is particularly useful for killing fish parasites and their inter-
mediate hosts (mainly snails), although it will also destroy insects, other in-
vertebrates, and shallow rooted water plants for a few weeks. Calcium ox-
ide or calcium hydroxide are recommended; the latter is easier to obtain
and less caustic. Lime may be applied either to a full or dewatered pond
(so long as the bottom is wet); in either case, the lime penetrates the pond
soil less than an inch. It is most important that the lime be applied evenly
across the pond, and mechanized application is better for this than manual
distribution. Except for the smallest ponds, equipment for applying lime
must be floated. This means that at least some water must be in the ponds,
even though lime is most effective when spread over dewatered soils.
Lime makes water alkaline. If the pH is raised above 10, much aquatic
life will be killed; above 11, nearly all of it. Application rates of 1,000 to
2,500 pounds of lime per acre will achieve such high pH values. Appropri-
ate rates within this range depend on the water chemistry of particular
90 FISH HATCHERY MANAGEMENT
ponds, especially on how well the water is naturally buffered with bicar-
bonates. Agricultural extension agents and the Soil Conservation Service
can provide detailed advice about water chemistry and lime applications.
Normally, a limed pond will be safe for stocking within 10 days after
treatment, or when the pH has declined to 9.5. However, a normal food
supply will not be present until three to four weeks later.
Chlorine has been used by fish culturists as a disinfecting agent. Ten
parts per million chlorine applied for 24 hours is sufficient to kill all harm-
ful bacteria and other organisms. Several forms of chlorine can be obtained.
Calcium hypochlorite is the most convenient to apply. It contains 70%
chlorine and is readily available. It can be applied to either flooded or
dewatered ponds.
A 600 parts per million solution of Hyamine 1622, Roccal, or Hyamine
3500 may be used for disinfecting ponds. Twice this strength may be used
to disinfect equipment and tools. The strength of the disinfecting solution
is based on the active ingredient as purchased.
Water Supply Structures
The water supply for a fish hatchery should be relatively silt-free and de-
void of vegetation that may clog intake structures. For this reason, an
earthen ditch is not recommended for conveying water because of algal
growth and the possibility of aquatic vegetation becoming established. At
hatcheries with a silt problem, a filter or settling basin may be necessary.
The water intake structure on a stream should include a barred grill to ex-
clude logs and large debris and a revolving screen to remove smaller debris
and stop fish from entering the hatchery.
There are a vast number of methods used to adjust and regulate water
flows through fish rearing units. Some of these include damboards, head-
boxes with adjustable overflows, headgates, headboards with holes bored
through them, molasses valves, faucet- type valves, and flow regulators.
Each type has advantages.
Generally, damboards and headboxes will not clog, and they provide a
safe means of regulating water flows. They are particularly useful with
gravity water supplies, but they are not easily adjusted to specific water
flows. Valves and flow regulators are readily adjustable to specific water
flows and are preferred with pressurized water supplies, but are prone to
clogging if any solid material such as algae or leaves is present in the
water.
Water flows can be measured with a pail or tub of known volume and a
stop watch when valves or gates are used to regulate the water flow. Dam
boards can be modified to serve as a rectangular weir for measuring flows
(Appendix D).
HATCHERY OPERATIONS 91
Screens
Various materials have been used to construct pond or raceway screens.
Door screening and galvanized hardware cloth can be used, but clog easily.
Wire screening fatigues and breaks after much brushing and must be re-
placed periodically. Perforated sheet aluminum screens are used commonly
in many fish hatcheries today. They can be mounted on wood or metal an-
gle frames. Redwood frames are easier than metal ones to fit to irregular
concrete slots in raceway walls.
Perforated aluminum sheets generally can be obtained from any sheet
metal company. Some suggested sheet thicknesses are 16 gauge for large
screens (ponds, raceways: 30x96 inches) and 18-20 gauge for small
screens (troughs: 7 x 13 inches). Round holes and oblong slots are available
in a number of sizes (Figure 36). Horizontal oblong slots are preferred by
some fish culturists who feel they are easier to clean and do not clog as
readily as round holes. They can be used with the following fish sizes:
Slot size Fish size
_\_
111
j_
s
\_
4
J_
2
Perforated aluminum center screens can also be used in circular rearing
tanks, but only the bottom 2-3 inches of the cylinder should be perforated.
These provide some self-cleaning action for the tank and prevent short-
circuiting of water flows by drawing waste water off the bottom of the
tank.
Pond Management
PRESEASON PREPARATION
Proper management of earthen ponds begins before water is introduced
into them. During the winter it is advisable to dry and disk ponds to pro-
mote aerobic breakdown of the nutrient-rich sediments. Although some nu-
trients are desirable for fingerling culture, because they promote algal
growth on which zooplankton graze, an overabundance tends to produce
more undesirable blue-green and filamentous algae. Relatively new ponds
with little buildup of organic material, or those with sandy, permeable bot-
toms that allow nutrients to escape to the groundwater, are less likely than
older or more impermeable ponds to require drying and disking. They may
xi
fry up to 1,000/lb
XT
1,000-200/lb
xi
200-30/lb
x|
30/lb and larger
92
FISH HATCHERY MANAGEMENT
Figure 36. Perforated aluminum screens showing (l) round holes, (2) staggered
slots, and (3) nonstaggered slots. (Courtesy California Department of Fish and
Game.)
actually leak if the bottom is disturbed, and it may be necessary to com-
pact their bottom with a sheepsfoot roller, rather than to disk them.
If a pond is to remain dry for several months it should be seeded around
the edges with rye grass (8-10 pounds per acre). This cover prevents ero-
sion of pond dikes and it can be flooded in the spring to serve as a source
of organic fertilizer. The grass should be cut and partially dried before the
pond is reflooded, or its rapid decay in water may deplete dissolved
oxygen.
Application of 1,000 pounds per acre of agricultural lime during the fal-
lowing period, followed by disking, may improve the buffering capacity of
HATCHERY OPERATIONS 93
a soft-water pond. Fertilizers are often spread on the pond bottom prior to
filling, and nuisance vegetation may also be sprayed at this time.
WILD-FISH CONTROL
Wild fish must be kept from ponds when they are filled, as they compete
with cultured species for feed, complicate sorting during harvest, may in-
troduce diseases, or confound hybridization studies. Proper construction of
the water system and filtration of inlet water can prevent the entrance of
wild fish.
A sock filter is made by sewing two pieces of 3- foot- wide material into a
12-foot-long cylinder, one end of which is tied closed and the other end
clamped to the inlet pipe (Figure 37). It can handle water flows up to
1,000 gallons per minute. This filter should be used only on near-surface
discharges, to prevent excessive strain on the screening.
A box filter consists of screen fastened to the bottom of a wooden box
eight feet long, three feet wide, and two feet deep (Figure 38), and is suit-
able for water flows up to 1,000 gallons per minute. The screen bottom is
supported by a wooden grid with 1 x 2 foot openings, which prevents ex-
cessive stress and stretching. The filter may be mounted in a fixed position
or equipped with floats. If the inlet water line is not too high above the
pond water level, a floating filter is preferred. This allows the screen to
remain submerged, whatever the water level, which reduces damage caused
by falling water.
If the water supply contains too much mud or debris and cannot be ef-
fectively filtered, ponds can be filled and then treated with chemicals to
kill wild fish. Rotenone is relatively inexpensive and is registered and la-
beled for this purpose. It should be applied to give a concentration of 0.5
to 2.0 parts per million throughout the pond. Rotenone does not always
control some fishes, such as bullheads and mosquitofish, and it requires up
to two weeks to lose its toxicity in warm water and even longer in cold wa-
ter. However, 2 to 2.5 parts per million potassium permanganate (KMn04)
can be added to detoxify rotenone.
Antimycin A is a selective poison that eliminates scaled fishes in the
presence of catfish. It does not kill bullheads, however, which are undesir-
able in channel catfish ponds. The chemical varies in activity in relation to
water chemistry and temperature; the instructions on the label must be
closely followed. Expert advice should be sought in special cases.
Chlorine in the form HTH, used at concentrations of 5 parts per million
for as little as one hour, will kill most wild species of fish that might enter
the pond. Chlorine deteriorates rapidly and usually loses its toxicity after
one day at this concentration. Chlorine can be neutralized if need be with
sodium thiosulfate. Chlorine is a nonspecific poison, and will kill most of
the organisms in the pond, not only fish.
94
FISH HATCHERY MANAGEMENT
FERTILIZATION PROCEDURES
Fertilization promotes fish production by increasing the quantity and qual-
ity of food organisms. Bacteria are important in the release or recycling of
nutrients from fertilizers. Once in solution, nutrients stimulate growth and
reproduction of algae which, in turn, support populations of zooplankton.
PIPE CLAMPS
SUPPLY LINE
SOCK FILTER,
WATER SURFACE
LEVEE
SARAN SOCK ATTACHED TO THE WATER LINE
Figure 37. Sock- type filters with saran screen for pond
inflows. (Diagram from Arkansas Game and Fish Commis-
sion; photo courtesy of Fish Farming Experimental Station,
Stuttgart, Arkansas.)
HATCHERY OPERATIONS 95
SUPPLY LINE
BOX FILTER
1
H
—fEiiiii
LEVEE
SCREEN BOX FILTER
^s:3i I
Figure 38. Box- type filters mounted in fixed positions.
(Diagram from Arkansas Game and Fish Commission;
photo courtesy of Fish Farming Experimental Station,
Stuttgart, Arkansas.)
Depending on the fish species, either algae or zooplankton (or both) supply
food to fry and fingerlings.
A number of factors effect the use of fertilizers, and responses are not
predictable under all conditions. Physical influences include area and
depth of the pond, amount of shoreline, rate of water exchange, turbidity,
9() FISH HATCHERY MANAGEMENT
and water temperature. Biological influences include type of plant and an-
imal life present and the food habits of the fish crop. Chemical elements al-
ready present in the water supply, composition of the bottom mud, pH,
calcium, magnesium, and chemical interactions have significant effects on
fertilizer response.
Not all ponds should be fertilized; fertilization may be impractical if a
pond is too large or too small. Turbid or muddy ponds with light penetra-
tion less than six inches should not be fertilized, nor those having a high
water exchange rate. Ponds having low water temperatures may not give a
good return for the amount of fertilizer applied. If the species of fish being
reared is not appreciably benefited by the type of food produced, fertiliza-
tion should not be considered. In cold regions where winterkill is common
in shallow productive ponds, fertilization may be undesirable.
Ponds should be thoroughly inspected before they are fertilized. Includ-
ed in the inspection may be a secchi disc reading to determine the water
turbidity; close examination for the presence of filamentous algae, rooted
aquatic vegetation, and undesirable planktonic forms; oxygen determina-
tions on any pond where low oxygen concentrations are suspected, and ob-
servation of nesting locations in spawning ponds.
Fertilizer to be applied should be weighed or measured on platform or
hanging scales, or with precalibrated buckets. It is necessary to calibrate a
bucket for each type of fertilizer used, because fertilizers vary considerably
in density. Small amounts of fertilizer may be dispensed with a metal
scoop, large amounts with a shovel or a mechanical spreader.
Distribution of the fertilizer in the pond will vary with wind direction,
size of the pond, whether organic or inorganic materials are used, and the
particular reason for fertilizing. On a windy day (which should be avoided
when possible), fertilizers should be distributed along the windward side of
the pond. In general, organic fertilizers (especially heavy forms such as
manure) should be given a more uniform distribution than the more solu-
ble inorganic ones. However, when insufficient phosphorus is thought to be
responsible for plankton die-off, an inorganic phosphate fertilizer should be
evenly distributed over most of the pond. Ordinarily, inorganic fertilizer
need not be spread over any greater distance than about half the length of
the pond on one side. If a pond is being filled or if the water level is being
raised, it may be advantageous to apply fertilizer near the inlet pipe.
Avoid wading through the pond while spreading fertilizers, if possible.
Wading stirs up the bottom mud and some of the fertilizer nutrients, par-
ticularly phosphates, may be adsorbed on the mud and temporarily re-
moved from circulation. A wader may destroy fish nests, eggs, and fry. Fer-
tilizer should not be spread in areas where nesting activity is underway or
into schools of fry. Larger fingerlings can swim quickly away from areas of
fertilizer concentration.
hatchery operations 97
Table 11. composition of several organic fertilizer materials, (source:
snow et al. 1964.)
CARBO
FERTILIZER
NITROGEN
PHOSPHORUS
POTASSIUM
PROTEIN
HYDRATES
Alfalfa hay
2.37
0.24
2.05
14.8
33.5
Grass hay
1.12
0.21
1.20
Peanut vine hay
l.(i2
0.13
1.25
lO.I
38.5
Cottonseed meal 36%
5.54
0.83
1.22
34.6
24.5
Cottonseed meal 43"o
7.02
1.12
1.45
43.9
15.8
Fish meal
10.22
2.67
0.40
63.9
2.1
Peanut meal
6.96
0.54
1.15
43.5
31.3
Meat scrap
8.21
5.15
51.0
3.5
Soybean oil meal
7.07
0.59
1 .90
44.2
29.0
Horse manure
0.49
0.26
0.48
Cow manure
0.43
0.59
0.44
Chicken manure
1.31
0.40
0.54
Sheep manure
0.77
0.39
0.59
Cladophera sp.
2.90
0.32
Potamogeton sp.
1.30
0.13
2.08
Najas flexilis
1.90
0.30
2.19
Chara sp.
0.70
0.27
0.58
Wood yeast (Torula)
6.9" 8.6
0.82 1.96
43 ,54
37.4 43.9
Green Italian ryegrass
0..50
0.09
0.40
3.1
11.5
Green rye
0.42
0.10
2.6
12.9
Green oats
0.42
0.09
0..50
2.6
13.5
Green vetch
0.67
0.07
0.41
4.2
8.1
Green, white clover
0.82
0.09
0.38
5.1
6.6
"Calculated by dividing protein content by 6.25.
ORGANIC FERTILIZERS
Organic materials such as composted plant residues, manure, stable
drainage, slaughterhouse waste, and municipal sewage are very good
sources of nitrogen. They also contain a large percentage of organic carbon
as well as other minerals in small amounts. Typical analyses are shown in
Table 11. Values may vary slightly depending on the conditions under
which the crops were grown or the products were processed.
Organic fertilizers are recommended for only fingerling fish production
to accelerate the production of zooplankton in rearing ponds, particularly
in new or sterile ponds. Their use is limited by cost and labor requirements
for application. The advantages of organic fertilizers are their (l) shorter
cycle for plankton production than inorganic fertilizers, (2) decomposition
to liberate CO^, which is used by plants for growth, (S) aid in clearing
silt-laden waters, and (4) use as a supplemental feed.
Their disadvantages are that they (l) are more expensive than inorganic fer-
tilizers, (2) may deplete the oxygen supply, (3) may stimulate filamentous
algae growth, and (4) require more labor to apply than inorganic fertilizers.
98 FISH HATCHERY MANAGEMENT
INORGANIC FERTILIZERS
Inorganic fertilizers are relatively inexpensive sources of nitrogen, phos-
phorus, and potassium, which stimulate algal growth, and calcium, which
helps to control water hardness and pH.
In nitrogen- free water, 0.3 to 1.3 parts per million of nitrogen must be ad-
ded to stimulate phytoplankton growth, and to sustain this growth about
one part per million must be applied at weekly intervals. In a normal
hatchery pond this comes to about eight pounds of nitrogen per surface
acre. Because nitrogen can enter the pond system from the atmosphere,
watershed, and decomposing organic matter, it is not always necessary to
add more.
For the operation of warmwater hatchery ponds, it is recommended that
nitrogen be included in the fertilizer applications during the late spring
and summer months for all ponds except those which have been weed- free
for at least three years. If development of phytoplankton is delayed longer
than four weeks, nitrogen should be added.
Forms of nitrogen available for pond fertilization are listed on Table 12.
Phosphorus is an active chemical and cannot exist alone except under
very specialized conditions. It is generally considered to be the most essen-
tial single element in pond fertilization and the first nutrient to become a
limiting factor for plant growth. Plankton require from 0.018 to 0.09 part
per million as a minimum for growth. Several workers have recommended
applications of about 1.0 part per million phosphorus pentoxide (P^OrJ
periodically during the production season.
Table 12. nitrogen fertilizers for pond enrichment.
pH OF
CHEMICAL
PERCENT
AQUEOUS
SOURCE MAIERIAL
FORMULA
NITROGEN
SOLUTION
Ammonium metaphosphate
(NHJ3PO,
XT'
Ammonium nitrate
NH4NO3
33.5
4.0
Ammonium phosphate
(NH^j.PO^
11*
4.0
Ammonium sulfate
(NHjj.SO,
20
5.0
Anhydrous ammonia
NH3HP
82
Aqua-ammonia
NH3H2O
40-50
Calcium cyanamide
CaCN,,
22
Diammonium phosphate
(NH,)^HP03
21'
8.0
Urea
H^HCONH^
46
7.2
Sodium nitrate
NaNO^
16
7.0
"Also contains 73",i P^r,.
'Also contains 48", 1 P^O-,.
'Also contains 48-52"(i P^Or,.
HATCHERY OPERATIONS
99
Table 13. sources of p^o, in commercial phosphate fertilizers
SOURCE MATERIAL
CHEMICAL FORMULA
' P;0-,
AVAILABILTIY
Ammonium
metaphosphate
Basic slag
Bone meal
Calcium
metaphosphate
Defluorinated
rock
Diammonium
phosphate
Enriched
superphosphate
Monoammonium
phosphate
Potassium
metaphosphate
Rock phosphate
Triple
(NHjaPO.,
(CaO-P^ySiO.^
Ca(P03)2
CalPOj^
(NHjaHPO^
Ca(H,P04),
NH^H^PO,
Ordinary Ca(H^P04)^
superphosphate
Phosphoric acid H3PO4
KPO.
(Ca3(P04),)3-CaF,
(Ca(H,P04),)3
15
60-65
73 Variable solubility; has
17"" nitrogen
9 Poor in calcium-rich
waters
Not readily available
Equal to superphosphate
in acid and neutral soil
41.3 Used primarily in live-
stock feeds; insoluble
in water
53 Completely water solu-
ble has 21" nitrogen
32 About the same as ordi-
nary superphosphate
48 CompleteH water-
soluble in form of
ammophosphate; has
1 1" I nitrogen
18-20 Not completely water-
soluble
72.5 Water-soluble and acid
in reaction
55-58 Equal to or superior to
ordinary superphos-
phate; has 35-38','u
32 Least soluble of calcium
salts; availability var-
ies from 0 to 15"»
44-51 A major portion is
water-soluble
Phosphorus will not exist for long in pondwater solution. Although both
plants and animals remove appreciable amounts of the added phosphate,
the majority of applied phosphorus eventually collects in the bottom mud.
Here, phosphorus may be bound in insoluble compounds that are per-
manently unavailable to plants. Some 90-95% of the phosphorus applied to
field crops in fertilizers becomes bound to the soil, and the same may hold
true in ponds.
100 FISH HATCHERY MANAGEMENT
A number of phosphate fertilizers are available for use in ponds. Ordi-
nary superphosphate is available commercially more than any other form
and is satisfactory for pond use. More concentrated forms may save labor
in application, however. Sources of P^O-, in commercial phosphate fertiliz-
ers are listed in Table 13. When nitrogen also is desired, ammoniated phos-
phates are recommended as they are completely water-soluble and gen-
erally should give a more rapid response. An application rate of 8 pounds
P2O-, per surface acre is normal in pond fertilization. This amount supplies
about 1 part per million in a pond averaging about 3 feet deep. In the
United States, the usual practice is to supply the needed phosphorus
periodically throughout the growing season. In Europe, however, the sea-
sonal phosphorus requirements are supplied in one or two massive applica-
tions either before or shortly after pond is filled, or at the beginning and
middle of the fish production cycle. A 50-100"'i) increase over normal
applications is justified in ponds with unusually hard waters, large
amounts of iron and aluminum, or high rates of water exchange.
Potassium generally is referred to as potash, a term synonomous with po-
tassium oxide (K2O). The most common sources are muriate of potash
(KCl) and potassium nitrate (KNO3). Potassium sulfate (K2SO4) also is a
source of potassium.
Potassium is less important than nitrogen or phosphorus for plankton
growth, but it functions in plants as a catalyst.
Increased phytoplankton growth occurs with increases in potassium from
0 to 2 parts per million; above 2 parts per million there is no additional
phytoplankton growth. Many waters have an ample supply of potassium for
plant growth, but where soils or the water supply are deficient or where
heavy fertilization with nitrogen and phosphorus is employed, addition of
potassium is desirable. It can be applied at the beginning of the production
cycle, or periodically during the cycle. It is quite soluble and unless ad-
sorbed by bottom deposits or taken up by plants, it can be lost by seepage
or leaching.
Calcium is essential for both plant and animal growth. It seldom is defi-
cient to the point that it exerts a direct effect on growth. Many of its ef-
fects are indirect, however, and these secondary influences contribute sig-
nificantly to the productivity of a body of water. Waters with hardness of
more than 50 parts per million CaC03 are most productive, and those of
less than 10 parts per million rarely produce large crops. Calcium ac-
celerates decomposition of organic matter, establishes a strong pH buffer
system, precipitates iron, and serves as a disinfectant or sterilant. In some
cases, fish production can be increased 25-100% by adding lime at the rate
of 2 to 3 tons per acre.
Calcium is available in three principal forms. It is 71"o of calcium oxide
(CaO) or quicklime, 54% of calcium hydroxide (Ca(OH)2) or hydrated
lime, and up to 40"ii of calcium carbonate (CaCO^) or ground limestone.
HATCHERY OPERATIONS 101
The form of calcium to apply depends upon the primary purpose for
which it is used. Unless bottom mud is below pH 7, lime is not recom-
mended except for sterilization purposes. For general liming, calcium hy-
droxide or ground limestone are the forms most suitable. Each has certain
advantages and disadvantages which make it desirable in specific situa-
tions.
Waters softer than 10 parts per million total hardness generally require
applications of lime, whereas waters harder than 20 parts per million sel-
dom respond to liming. The need for lime may be indicated when inor-
ganic fertilization fails to produce a substantial plankton bloom. However,
analysis of the water or, preferably, of the bottom mud should be made for
total hardness and alkalinity before lime is applied. A state agricultural
experiment station or extension service can assist with these (and other)
analyses.
Liming can be done with the pond either dry or filled with water. Suit-
able mechanical equipment is needed to assure uniform dispersion. A
boat- mounted spreader can be used for ponds filled with water. If the pond
contains water, additional amounts of lime may be added to satisfy the
needs of the water as well as of the bottom mud. It may take 3 to 6 months
before the pond responds. In some situations, limed ponds revert to an acid
condition within two years after the initial application.
COMBINING FERTILIZERS
In making a decision on whether to use organic or inorganic fertilizers, the
advantages and disadvantages should be carefully considered. Comparative
tests have been attempted but conclusive answers as to which material is
best often will depend upon the individual situation or production cycle in-
volved.
Combining organic and inorganic fertilizers is a common practice. Many
workers have found that a combination of an organic meal and superphos-
phate, in a ratio of 3:1, gave higher fish production than the organic
material alone. In hatchery rearing ponds where draining is frequent and
time for development of a suitable food supply often is limited, combining
organic and inorganic fertilizers appears to be advantageous. While the
cost of such a procedure is greater than with inorganic fertilization, the
high value of the fish crop involved normally justifies the added cost,
particu- larly in the case of bass and catfish rearing.
The ratio of 4-4-1, N2-P20-,-K20, is needed to produce favorable
plankton growth for fish production ponds. The fertilizer grade most com-
monly used is 20-20-5, which gives the 4-4-1 ratio with relatively little
filler.
The type of fertilizer program chosen will be determined by such factors
as species of fish reared, time of year, cost, availability of product, and past
102 FISH HATCHERY MANAGEMENT
experience. If the species to be reared is a predator species such as large-
mouth bass, striped bass, or walleye, a typical program might be as follows.
In spring, while the pond is still dry, disk the pond bottom. Apply lime
if needed to bring pH into a favorable range. The fertilizer can be spread
on the dry pond bottom and the pond then filled, or the pond filled and
then the fertilizer spread; the following example assumes it is on the pond
bottom.
Spread: 500 pounds per acre chopped alfalfa hay; 200 pounds per acre
meat scraps; 200 pounds per acre ground dehydrated alfalfa hay; 50
pounds per acre superphosphate; 10 pounds per acre potash; 1,000 pounds
per acre chicken manure. Fill the pond and wait 3 to 5 days before stock-
ing fish.
This fertilizer program for sandy loam soils and slightly acid waters will
produce an abundance of zooplankton needed for rearing the predator
species. Usually this amount is added only one time and will sustain the
pond for 30-40 days. If the fish crop is not of harvest size by that time, a
second application of all or part of the components may be needed.
If the species to be reared is a forage species such as bluegill, redear sun-
fish, goldfish, or tilapia, the following program might be used: 100 pounds
per acre ammonium nitrate; 200 pounds per acre superphosphate; 50
pounds per acre potash; 100 pounds per acre chopped alfalfa hay; 300
pounds per acre chicken manure. This fertilizer program will produce more
phytoplankton than the one outlined for predators. As with the one above,
this program will have to be repeated about every 30-45 days.
The type of fertilizer program that works best at any particular station
will have to be developed at that station. The program that works best at
one station will not necessarily work well at another. The examples given
above are strictly guidelines.
AQUATIC VEGETATION CONTROL
Aquatic plants must have sunlight, food, and carbon dioxide in order to
thrive. Elimination of any one of these requirements inhibits growth and
eventually brings about the death of the plant. The majority of the com-
mon water weeds start growth on the bottom. Providing adequate depth to
ponds and thus excluding sunlight essential to plant growth may prevent
weeds from becoming established. Water plants are most easily controlled
in the early stages of development. Control methods applied when stems
and leaves are tender are more effective than those applied after the plant
has matured. In most cases, seeds or other reproductive bodies are absent
in early development and control at this time minimizes the possibility of
reestablishment.
The first step in controlling aquatic vegetation is to identify the plant.
After the problem weed has been identified, a method of control can be
HATCHERY OPERATIONS 103
selected. Control methods may be mechanical, biological, or chemical,
depending upon the situation.
Mechanical control consists of removal of weeds by cutting, uprooting, or
similar means. While specialized machines have been developed for mow-
ing weeds, they are expensive and not very practical except in special cir-
cumstances. In small ponds, hand tools can be employed for plant removal.
Even in larger bodies of water, mechanical removal of weeds may be feasi-
ble provided that work is begun when the weeds first appear.
Biological weed control is based on natural processes. Exclusion of light
from the pond bottom by adequate water depth and turbidity resulting
from phytoplankton is one method. Production of filamentous algae that
smother submerged rooted types of weeds is another.
The most inexpensive form of weed control for many ponds is control or
prevention through the use of fertilizers. When an 8-8-2 grade fertilizer is
applied at a rate of 100 pounds per acre, every 2 to 4 weeks during the
warm months of the year, microscopic plants are produced that shade the
bottom and prevent the establishment of weeds. Although 8 to 14 applica-
tions are needed each season, fish production is increased along with the
weed control achieved. Generally, most aquatic weeds may be controlled
by fertilization in properly constructed ponds. However, such a program of
fertilization will be effective in controlling rooted weeds only if the secchi
disk reading already is 18 inches or less.
Winter fertilization is a specialized form of biological control effective on
submerged rooted vegetation if the ponds cannot be drained. An 8-8-2
grade fertilizer or equivalent is applied at a rate of 100 pounds per acre
every 2 weeks until a dense growth of filamentous algae covers the sub-
merged weed beds. Once the algae appears, an application of fertilizer is
made at 3- to 4-week intervals until masses of algae and rooted weeds be-
gin to break loose and float. All fertilization is then stopped until the
plants have broken free and decomposed. This will start in the late spring
and generally takes from four to six weeks. Phytoplankton normally re-
place the filamentous algae and rooted weeds and should be mantained by
inorganic fertilization with 100 pounds of 8-8-2 per acre applied every 3
to 4 weeks.
Lowering the water level of the pond in the late fall has been helpful in
achieving temporary control of watershield. This practice also aids in the
chemical control of alligator weed, water primrose, southern water grass,
needlerush, knotgrass, and other resistant weeds that grow partially sub-
merged and have an extensive root system.
Plant-eating fish that convert vegetation to protein have been considered
in biological control. Among these are grass carp, Israeli carp (a race of
common carp), and tilapia. Experiments have indicated that the numbers
of Israeli carp and tilapia required to control plants effectively are so large
104 FISH HATCHERY MANAGEMENT
that these fish would compete for space and interfere with the production
of other, more desirable species.
Extensive development of herbicides in recent years makes chemical con-
trol of weeds quite promising in many instances. When properly applied,
herbicides are effective, fast, relatively inexpensive, and require less labor
than some of the other control methods. Chemical control, however, is not a
simple matter. Often the difference in toxicity to weeds and to fish in the
pond is not great. Some chemicals are poisonous to humans or to livestock
and they may have an adverse effect on essential food organisms. Decay of
large amounts of dead plants can exhaust the oxygen supply in the water,
causing death of fish and other aquatic animals. It is essential that discretion
regarding treatment be followed if satisfactory results are to be obtained.
An important aspect of vegetation control is the rate of dilution of ap-
plied herbicides and the effect of substances present that may neutralize
the toxicity of the chemical used. The rate of water exchange by seepage
or outflow and the chemical characteristics of the water and pond bottom
also affect the success of chemical control measures. Often the herbicide
must reach a high percentage of the plant surface before a kill is obtained;
the chemical must be applied carefully if good results are to be achieved.
The herbicide is applied directly on emergent or floating weeds and to
the water where submerged weeds are growing. The first type of treatment
is called a local treatment, the second is termed a solution treatment ap-
plied either to a plot or to the entire pond.
Conventional sprayers are used to apply the local treatments and in
some instances may be suitable for solution treatments. Chemicals for solu-
tion treatment are sometimes diluted with water and poured into the wake
of an outboard motor, sprinkled over the surface of the pond, or run by
gravity into the water containing the weed beds. Crystalline salts may be
placed in a fine woven cotton bag and towed by boat, allowing the herbi-
cide to dissolve and mix with the pond water. Some herbicides are
prepared in granular form for scattering or broadcasting over the areas to
be treated. Generally, the more rapidly the chemical loses its toxicity the
more uniformly it must be distributed over the area involved for effective
results. Also, if the chemical is at all toxic to fish, it must be uniformly dis-
tributed. Emergent or floating vegetation receiving local treatments applied
with spray equipment should be uniformly covered with a drenching spray
applied as a fine mist.
A number of precautions should always be taken when herbicides are
used. Follow all instructions on the label and store chemicals only in the
original labeled container. Avoid inhalation of herbicides and prevent their
repeated or prolonged contact with the skin. Wash thoroughly after han-
dling herbicides, and always remove contaminated clothing as soon as pos-
sible. Prevent livestock from drinking the water during the post- treatment
period specified on the label. Do not release treated water to locations that
HATCHERY OPERATIONS 105
may be damaged by activity of the chemical. Avoid overdoses and spil-
lages. Avoid use near sensitive crops and reduce drift hazards as much as
possible; do not apply herbicides on windy days. Clean all application
equipment in areas where the rinsing solutions will not contaminate other
areas or streams.
Fish culturists must also be aware of the current registration status of
herbicides. Continuing changes in the regulation of pesticide and drug use
in the United States has created confusion concerning what chemicals may
be used in fisheries work. Table 14 lists those chemicals that presently pos-
sess registered status for use in the presence of food fish only, a food fish
being defined as one normally consumed by humans.
Special Problems in Pond Culture
DISSOLVED OXYGEN
Because adequate amounts of dissolved oxygen are critical for good fish
growth and survival, this gas is of major concern to fish culturists (Figure
39). On rare occasions, high levels of oxygen supersaturation — caused by
intensive algal photosynthesis — may induce emphysema in fish. Virtually
all oxygen- related problems, however, are caused by gas concentrations
that are too low.
Tolerances of fish to low dissolved oxygen concentrations vary among
species. In general, fish do well at concentrations above 4 parts per million.
They can survive extended periods (days) at 3 parts per million, but do not
grow well. Most fish can tolerate 1-2 parts per million for a few hours, but
will die if concentrations are prolonged at this level or drop even lower.
In ponds that have no flowing freshwater supply, oxygen comes from
only two sources: diffusion from the air; and photosynthesis. Oxygen dif-
fuses across the water surface into or out of the pond, depending on
whether the water is subsaturated or supersaturated with the gas. Once
oxygen enters the surface film of water, it diffuses only slowly through the
rest of the water mass. Only if surface water is mechanically mixed with
the rest of the pond — by wind, pumps, or outboard motors — will diffused
oxygen help to aerate the whole pond.
During warmer months of the year when fish grow well, photosynthesis
is the most important source of pond oxygen. Some photosynthetic oxygen
comes from rooted aquatic plants, but most of it typically comes from phy-
toplankton. Photosynthesis requires light; more occurs on bright days than
on cloudy ones. The water depth at which photosynthesis can occur
depends on water clarity. Excessive clay turbidity or dense blooms of phy-
toplankton can restrict oxygen production to the upper foot or less of wa-
ter. Generally, photosynthesis will produce adequate amounts of oxygen for
106 FISH HATCFIKRY MANAGEMENT
TaBI.K 14. HERBICIDES REGISTERED HY IHE UNH KD S I'A 1 ES FOOD AND DRUG
AL. 1976; SNOW ET AL. U)64.)
COMPOUND
FORMll.Al ion"
VEGETATION
AFTECrED
ToxicTTV ro
ANIMALS
Copper
sulfate
Crystals, 100"n
Algae and submerged
rooted plants
Moderate to high
Diquat
Liquid, 35"'ii
Emergent, terrestrial,
Low
(bromide)
submerged
Endothal
Liquid, 35"ii
Submerged, rooted
Low
Simazine
Powder, 80"(i
Algae, submerged,
terrestrial
Low
2,4- D'
Granular, 10"n
Floating, emergent,
Low
salt, 80"n
terrestrial
ester, 37-42%
amine, 28-42"(i
granular, 20""
Low or moderate
"Percentages are percent actual ingredient.
Consult product labels for limitations on use.
'Only for use by federal, state, and local public agencies.
fish to a depth of two to three times the secchi disk visibility. Penetration
of oxygen below this depth depends on mechanical mixing.
Two processes use up dissolved oxygen: chemical oxidation and respira-
tion. Both occur throughout the water column and in the top layer of pond
sediments. The first involves chiefly inorganic compounds and elements,
and rarely is of major significance in ponds. Respiration is the main cause
of oxygen depletion. All aquatic organisms respire — not only fish, but
plants, phytoplankton (even during photosynthesis), zooplankton, bottom
animals (such as crayfish), and perhaps most importantly, the bacteria that
live off nitrogenous and organic material.
Over the whole year, but especially during the growing season, the oxy-
gen concentration in a pond is determined primarily by the balance of pho-
tosynthesis and respiration. For pond fish culture to succeed, photosyn-
thesis must stay ahead of respiration. Pond management techniques involve
manipulation of both components.
Of all the physical variables that affect dissolved oxygen concentrations,
temperature is by far the most important. It has direct influences on the
oxygen balance: photosynthesis, respiration, and chemical oxidation all
proceed faster at higher temperatures. It has a direct influence on a pond's
A I en IK Y OI'KRAIIONS
107
AUMIMSIRAI 1U.\ lOR LSI. Willi lool) MSll. ll.BKl AK'l, I!i7i. SOIRC'K MKVF.R i: I
AI'PLICAIION
RATES
MODL t)K
ACTION
COM MEN is"
0.1 -.").(> ppm
2-3 pounds/acre
()..')-2.() ppm
1-3 ppm
0.3-2.0 ppm
(10-40 pounds/
(acre)
3-l,T pounds/acre
Nonsystemic
Nonsystemic
Probably
nonsystemic
Systemic
Systemic
Limit is one part per million for
copper complexes, but
CuS04-5H20 and basic copper
carbonate are exempted from
the limit
Interim limit in potable water is
0.01 part per million
Interim limit in potable water is
0.2 part per million
Upper limits are 12 parts per mil-
lion in raw fish and 0.01 part
per million in potable water.
Upper limit in raw- fish and shellf-
ish is 1 part per million.
oxygen capacity: less oxygen dissolves in water at higher temperatures. It
has an indirect effect on oxygen circulation: as temperature rises, water be-
comes more difficult to mix. If temperatures rise high enough, and the wa-
ter is deep enough, the pond may stratify into an upper, warmer, wind-
mixed layer and a lower, cooler, poorly circulated layer. In such cases, lit-
tle water moves across the thermocline separating the two layers. The
upper layer receives, and keeps, most of the new oxygen (chiefly from pho-
tosynthesis by phytoplankton); the lower layer receives little new oxygen,
and loses it — sometimes completely — to respiration (chiefly by bacteria).
Several pond management techniques attempt to overcome the effects such
temperature- induced stratification has on the oxygen supply.
It is easy to see why pond-oxygen problems are more acute in summer
than in autumn, winter, and spring. When the water is cool, it can dissolve
more oxygen, and it is more easily mixed by wind action to the pond bot-
tom. Photosynthesis is less, but so is respiration, and photosynthetic oxy-
gen is kept in the pond.
In contrast, vr-ater circulation is constrained in summer. In the upper
layers, especially in stratified ponds, photosynthesis may be so intense that
the water becomes supersaturated with oxygen so that much of the gas is
108 FISH HATCHERY MANAGEMENT
Figure 39. An essential instrument in any fish rearing opera-
tion is an oxygen meter. Catastrophic fish losses can be
avoided if oxygen concentrations are checked periodically and
the optimum carrying capacity of the hatchery can be deter-
mined. Several brands of meters are available commercially.
(FWS photo.)
lost to the air. The water has a lower capacity for oxygen, and little of it
may reach the pond bottom. Planktonic animals have short life spans; as
more are produced during warm weather, more also die and sink to the
bottom, where bacteria decompose them — utilizing oxygen in the process.
Respiration levels are high, meaning that more metabolism is occurring
and more wastes produced. These also are stimulants to bacterial produc-
tion. So is any uneaten food that may be provided by the culturist. Both
oxygen production and consumption are very rapid, and the balance is
HATCHERY OPERATIONS 109
vulnerable to many outside influences: a cloudy day that slows photosyn-
thesis; a hot still day that causes stratification; a miscalculated food ration
that is too large for fish to consume before it decomposes.
Typically the summer oxygen content in a pond follows a 24- hour cycle:
highest in the late afternoon after a day of photosynthesis; lowest at dawn
after a night of respiration. It is the nighttime oxygen depletion that is
most critical to pond culturists.
Pond managers can take several precautions to prevent, or reduce the
severity of, dissolved oxygen problems.
(1) Most ponds are fertilized to stimulate plankton production for natur-
al fish food. Suitable plankton densities allow secchi disk readings of 12-24
inches. Fertilization should be stopped if readings drop to 10 inches or less.
Special care should be taken if the pond is receiving supplemental fish
food, as this can stimulate sudden plankton blooms and subsequent die-
offs.
(2) Because the frequency of dissolved oxygen problems increases with
the supplemental feeding rate, fish should not be given more than 30
pounds of food per acre per day.
(3) If algicides are used to control plankton densities, they should be ap-
plied before, rather than during, a bloom. Otherwise, the accelerated die-
off of the bloom will worsen the rate of oxygen depletion.
(4) During critical periods of the summer, the oxygen concentration
should be monitored. This is most easily accomplished at dusk and two or
three hours later. These two values can be plotted against time on a graph,
and the straight line extended to predict the dissolved oxygen at dawn.
This will allow emergency aeration to be prepared in advance.
Dissolved oxygen problems may arise in spite of precautions. Corrective
measures for specific problems are suggested below.
(1) If there has been an excessive kill of pond weeds or plankton that
are decaying, add 20'/o superphosphate by midmorning at a rate of 50-100
pounds per acre. Stir the pond with an outboard motor or otherwise mix or
circulate water to rapidly distribute phosphate and add atmospheric oxy-
gen; 1 to 2 hours of stirring a 1-acre pond should suffice. Dilute the
oxygen- deficient water with fresh water of about the same temperature.
Distribute, as evenly as possible, 100-200 pounds of hydrated lime,
Ca(OH)2, per acre in the late afternoon if CO2 levels are 10 parts per mil-
lion or higher. Then stir for another one to two hours.
(2) Low dissolved oxygen may be caused by excessive rooted vegetation
and a lack of phytoplankton photosynthesis. If the pond is unstratified, add
P2O5 and stir or circulate as in (l) above. Add fresh water if available. If
the pond is stratified, which is the usual case in warm months, aerate the
surface waters by agitation, draw off the cool oxygen- deficient bottom wa-
ter, or add colder fresh water.
1 10 FISH HATCHERY MANAGEMENT
(3) If the problem is caused by too much supplemental feed, drastically
reduce or eliminate feeding until the anaerobic condition is corrected.
Drain off foul bottom water. Refill the pond with fresh water and add P^Or,
to induce phytoplankton growth.
(4) Summer stratification of ponds often is inevitable. During its early
stage of development, when cool anaerobic water is less than 20-25% of the
total pond volume and upper waters have a moderate growth of green
plants, top and bottom water can be thoroughly mixed. Aerate the pond
with special equipment or an air compressor, or vigorously stir it with an
outboard- powered boat or with a pump. If the layer of anaerobic water is
more than ^ the total pond volume, drain off the anaerobic water, refill
with fresh water, and fertilize to re-establish the phytoplankton bloom.
(5) Low dissolved oxygen may result from excessive application of
organic fertilizers, which overstimulates plankton production. Treat this
problem as in example (l), above. Two to six parts per million potassium
permanganate (KMnO,) may be added to oxidize decaying organic matter,
freeing the available oxygen for the pond fish.
Quite often, oxygen depletion is caused by two or more of the above fac-
tors acting simultaneously. In such cases, a combination of treatments may
be needed. If a substantial amount of foul bottom water exists, the pond
should never be mixed, because the oxygen deficit in the lower water layer
may exceed the amount of oxygen available in the surface layer. Drain off
the anaerobic water and replace it with fresh water from a stream, well, or
adjacent pond. An effective technique is to pump water from just below
the surface of the pond and spray it back onto the water surface with force.
Small spray- type surface aerators are in common use. These aerators are
most effective in small ponds or when several are operated in a large pond.
More powerful aerators such as the Crisafulli pump and sprayer and the
paddlewheel aerator supply considerably more oxygen to ponds than the
spray- type surface aerators. However, Crisafulli pumps and paddlewheel
aerators are expensive and must be operated from the power take-off of a
farm tractor. The relative efficiency of several types of emergency aeration
appears in Table 15.
ACIDITY
Fish do not grow well in waters that are too acid or too alkaline, and the
pH of pond waters should be maintained within the range of 6.5 to 9. The
pH of water is due to the activity of positively charged hydrogen ions
(H ), and pH is controlled through manipulation of hydrogen ion concen-
trations: if the pH is too low (acid water), H^ concentrations must be de-
creased.
The treatments for low pH (liming) were discussed on pages 108-109.
The principle involved is to add negatively charged ions, such as carbonate
hatchery operations 1 1 1
Table 15. amounts of oxygen added to pond waters by different tech-
niques OF emergency aeration. (SOURCE: BOYD 1979.)
OXYGEN RELATIVE
ADDED EFFICIENCY
TYPE OF EMERGENCY AREATION (LB/ACRE) ("..)
Paddlewheel aerator 48.9 100
Crisafulli pump with sprayer 31.2 64
Crisafulli pump to discharge oxy- 19.0 39
genated water from adjacent
pond
Otterbine aerator (3.7 kilowatts) 15.2 31
CrisfuUi pump to circulate pond 11.8 24
water
Otterbine aerator (2.2 kilowatts) 11.3 23
Rainmaster pump to circulate 10.7 22
pond water
Rainmaster pump to discharge 6.0 12
oxygenated water from adjacent
pond
Air-o-later aerator (0.25 kilowatt) 3.9 8
(CO3") or hydroxyl (OH ), that react with H^ and reduce the latter's con-
centration.
Excessively high pH values can occur in ponds during summer, when
phytoplankton are abundant and photosynthesis is intense. As carbon diox-
ide is added to ponds, either by diffusion from the atmosphere or from
respiration, it reacts with water to form a weak carbonic acid. The basic
reaction involved is:
CO^ + H^O ^ H^C03 ^ H+ + HCOr ^ 2H+ + C03=.
As more CO2 is added, the reaction moves farther to the right, generating
first bicarbonate and then carbonate ions; H"*^ is released at each step,
increasing the acidity and lowering the pH. Photosynthesizing plants
reverse the reaction. They take CO2 from the water, and the HC03~ and
CO3" ions bind hydrogen; acidity is reduced and pH rises — often to levels
above ten.
Two types of treatment for high pH can be applied. One involves addi-
tion of chemicals that form weak acids by reacting with water to release
H^; they function much like CO^ in this regard. Examples are sulfur, fer-
rous sulfate, and aluminum sulfate, materials also used to acidify soils. The
action of sulfur is enhanced if it is added together with organic matter,
such as manure.
A second treatment for high pH is the addition of positively charged
ions that bind preferentially with COa^; they keep the carbonate from
1 12 FISH HATCHERY MANAGEMENT
recombining with hydrogen and prevent the above reaction from moving to
the left, even though plants may be removing CO^ from the water. The
most important ion used for this purpose is calcium (Ca ), which usually
is added in the form of gypsum (calcium sulfate, CaSOj.
The two types of treatments may be combined. For example, sulfur,
manure, and gypsum together may be effective in reducing pond alkalinity.
TURBIDITY
Excessive turbidity in ponds obstructs light penetration; it can reduce pho-
tosynthesis and make it more difficult for fish to find food. Much turbidity
is caused by colloids — clay particles that remain suspended in water
because of their small size and negative electric charges. If the charges on
colloidal particles can be neutralized, they will stick together —
flocculate — and precipitate to the bottom. Any positively charged material
can help flocculate such colloids. Organic matter works, although it can
deplete a pond's oxygen supply as it decomposes, and is not recommended
during summer months. Weak acids or metallic ions such as calcium also
can neutralize colloidal charges, and many culturists add (depending on
pH) limestone, calcium hydroxide, or gypsum to ponds for this purpose.
HYDROGEN SULFIDE
Hydrogen sulfide, H^S, is a soluble, highly poisonous gas having the
characteristic odor of rotten eggs. It is an anaerobic degradation product of
both organic sulfur compounds and inorganic sulfates. Decomposition of
algae, aquatic weeds, waste fish feed, and other naturally deposited organic
material is the major source of H^S in fish ponds.
The toxicity of H^S depends on temperature, pH, and dissolved oxygen.
At pH values of five or below, most of the H^S is in its undissociated toxic
form. As pH rises the H7S dissociates into S and H^ ions, which are
nontoxic. At pH 9 most of the H^S has dissociated to a nontoxic form. Its
toxicity increases at higher temperatures, but oxygen will convert it to
nontoxic sulfate.
H^S is toxic to fish at levels above 2.0 parts per billion and toxic to eggs
at 12 parts per billion. It is a known cause of low fish survival in organi-
cally rich ponds. If the water is well oxygenated, H^|S will not escape from
the sediments unless the latter are disturbed, as they are during seining
operations. Hydrogen sulfide mainly is a problem during warm months,
when organic decomposition is rapid and bottom waters are low in dis-
solved oxygen.
Hydrogen sulfide problems can be corrected in several ways: (l) remove
excess organic matter from the pond; (2) raise the pH of the water (see
above); (3) oxygenate the water; (4) add an oxidizing agent such as potas-
sium permanganate.
HATCHERY OPERATIONS 113
WATER LOSS
Water loss by seepage is a problem at many hatcheries. A permanent solu-
tion is to add a layer of good quality clay about a foot thick, wetted, rolled,
and compacted into an impervious lining, (in small ponds, the same effect
can be achieved with polyethylene sheets protected with three to four
inches of soil.) Bentonite can be used effectively to correct extreme water
loss when applied as follows:
(1) Disk the bottom soil to a depth of six inches, lapping cuts by 50%.
(2) Harrow the soil with a spike- tooth harrow, overlapping by 50%.
(3) Divide treated area into 10-foot by 10-foot squares.
(4) Uniformly spread 50 pounds of bentonite over each square (20,000
pounds per acre).
(5) Disk soil to a depth of three inches.
(6) Compact soil thoroughly with a sheepsfoot roller.
This procedure has reduced seepage over 90% in some cases.
Evaporation is a problem in farm and hatchery ponds of the southwest.
Work in Australia indicates that a substantial reduction in evaporation
(25%) can be reduced by a film of cetyl alcohol (hexadecanol), applied at a
rate of about eight pounds per acre per year. The treatment is only effec-
tive in ponds of two acres or less.
PROBLEM ORGANISMS
Most plants, animals, and bacteria in a pond community are important in
fish culture because of their roles as fish food and in photosynthesis,
decomposition, and chemical cycling. However, some organisms are un-
desirable, and sometimes have to be controlled.
Some crustaceans — members of the Eubranchiopoda group such as the
clam shrimp {Cyzicus sp.), the tadpole shrimp {Apus sp.) and the fairy
shrimp [Streptocephalus sp.)— compete with the fish fry for food, cause ex-
cessive turbidity that interfers with phytosynthesis, clog outlet screens, and
interfere with fish sorting at harvest. They usually offer no value as fish
food, because of their hard external shell and because of their fast growth
to sizes too large to eat.
These shrimp need alternating periods of flooding and desiccation to
perpetuate their life cycles, and they can be controlled naturally if ponds
are not dried out between fish harvests. However, they usually are con-
trolled with chemicals. Formalin, malathion, rotenone, methyl parathion,
and others have been used with varying degrees of success; many of these
are very toxic to fish. The best chemicals today are dylox and masoten,
which contain the active ingredient trichlorfon and which have been re-
gistered for use as a pesticide with nonfood fish. Treatments of 0.25 part
per million dylox will kill all crustaceans in 24 hours, without harming
114 FISH HATCHERY MANAGEMENT
fish. Most of the desirable crustacean species will repopulate the pond in
two or three days.
Most members of the aquatic insect groups Coleoptera (beetles) and
Hemiptera (bugs) prey on other insects and small fish. In some cases,
members of the order Odonata (dragonflies) cause similar problems. Most
of these insects breath air, and can be controlled by applying a mixture of
one quart motor oil and two to four gallons diesel fuel per surface acre
over the pond. As insects surface, their breathing apertures become clogged
with oil and they may get caught in the surface film. The treatment is
harmless to fish but supplemental feeding should be discontinued until the
film has dissipated. Nonsurfacing insects can be killed by 0.25 part per mil-
lion masoten.
Large numbers of crayfish in rearing ponds may consume feed intended
for the fish, inhibit feeding activity, cause increased turbidity, and interfere
with seining, harvesting, and sorting of fish. Baytex is an effective control;
0.1-0.25 part per million Baytex will kill most crayfish species in 48 hours
or less without harming the fish.
Vertebrates that prey on fish may cause serious problems for the pond-
fish culturist. Birds, otters, alligators, and turtles, to name a few, are impli-
cated annually. Some can be shot, although killing of furbearing mammals
generally requires a special license or permit issued by the states. Fences
can keep out some potential predators, but nonlethal bird control (several
forms of scaring them away) do not produce long-lasting results.
Adult and immature frogs have long plagued the warmwater culturist.
The adults are predaceous and may transmit fish diseases; the immature
frogs consume feed intended for fish and must be removed by hand from
fish lots awaiting transport. Adults usually are controlled with firearms,
whereas attempts to control the young are limited to physical removal of
egg masses from ponds or by treating individual masses with copper sulfate
or pon's green. Although some laboratory success has been achieved with
formalin, there still is no good chemical control available for frog tadpoles.
Recordkeeping
Factors to be Considered
Recordkeeping, in any business or organization, is an integral part of the
system. It is the means by which we measure and balance the input and
output, evaluate efficiency, and plan future operations.
Listed below are factors that should be considered in efficient record-
keeping. These factors are particularly applicable to trout and salmon
hatcheries, but many of them pertain to warmwater hatcheries as well.
HATCHERY OPERATIONS 1 15
Water
(1) Volume in cubic feet for each rearing unit and for the entire
hatchery.
(2) Gallons per minute and cubic feet per hour flow into each unit and
for the entire hatchery.
(3) Rate of change for each unit and for the total hatchery.
(4) Temperature.
(5) Water quality.
Mortality
(1) Fish or eggs actually collected and counted (daily pick-off).
(2) Unaccountable losses (predation, cannibalism) determined by com-
parison of periodic inventories.
Food and Diet
(1) Composition.
(2) Cost per pound of feed and cost per pound of fish gained.
(3) Amount of food fed as percentage of fish body weight.
(4) Pounds of food fed per pound of fish produced (conversion).
Fish
(1) Weight and number of fish and eggs on hand at the beginning and
end of accounting period.
(2) Fish and eggs shipped or received.
(3) Gain in weight in pounds and percentage.
(4) Date eggs were taken, number per ounce, and source.
(5) Date of first feeding of fry.
(6) Number per pound of all lots of fish.
(7) Data on broodstock.
Disease
(1) Occurrence, kind, and possible contributing factors.
(2) Type of control and results.
Costs (other than fish food):
(1) Maintenance and operation.
(2) Interest and depreciation on investment.
(3) Analysis of all cost and production records.
IKJ FISH HATCHERY MANAGEMENT
Production Summary
Some additional records that should be considered for extensive (pond)
culture follow.
Water
(1) Area in acres of each pond.
(2) Volume in acre-feet.
(3) Average depth.
(4) Inflow required to maintain pond level.
(5) Temperatures.
(6) Source and quality.
(7) Weed control (dates, kind, amount, cost, results).
(8) Fertilization (dates, kind, amount, cost, results).
(9) Algae and zooplankton blooms (dates and secci visibility in inches;
kinds of plankton).
Fish
(1) Broodstock
(a) Species, numbers.
(b) Stocked for spawning (species, numbers, dates).
(c) Replacements (species, numbers, weights).
(d) Feeding and care (kind, cost, and amounts of food, including
data on forage fish production).
(e) Diseases and parasites (treatments, dates, results).
(f) Fry produced per acre and per female.
(2) Fingerlings
(a) Species (numbers stocked, size, weight, date)
(b) Number removed, date, total weight, weight per thousand,
number per pound.
(c) Supplemental feeding (kind, amount, cost).
(d) Disease and predation (including insect control, etc.).
(3) Production per acre by species (numbers and pounds).
(4) Days in production.
(5) Weight gain per acre per day.
(6) Cost per pound of fish produced at hatchery.
(7) Cost per pound including distribution costs.
A variety of management forms are in use at state, federal, and commercial
hatcheries today. The following examples have been used in the National
Fish Hatchery system of the Fish and Wildlife Service. These forms, or
variations of them, can be helpful to the fish culturist who is designing a
recordkeeping system.
HATCHERY OPERATIONS 117
Lot History Production Charts
Production lots of fish originating from National Fish Hatcheries are iden-
tified by a one- digit numeral that designates the year the lot starts on feed
and a two-letter abbreviation that identifies the National Fish Hatchery
where the lot originated. When production lots are received from sources
outside the National Fish Hatchery system the following designations ap-
ply: (l) the capital letter "U" designates lots originating from a state
hatchery followed by the two-letter abreviation of the state; (2) the capital
letter "Y" and the appropriate state abbreviation designates lots originating
from commercial sources; (3) the letter "F" followed by the name of the
country identifies lots originating outside the United States. For example:
Lot 7-En designates the 1977 year class originating at the
Ennis National Fish Hatchery.
Lot 7-UCA designates the 1977 year class originating at a
California state fish hatchery.
Lot 7-YWA designates the 1977 year class originating from a
commercial hatchery in the state of Washington.
Lot 7-F-Canada designates the 1977 year class originating in
Canada.
Lots from fall spawning broodstock that begin to feed after November
30th are designated as having started on January 1st of the following year.
The practice of maintaining sublots is discouraged but widely separated
shipments of eggs result in different sizes of fish and complicated record
keeping. When sublots are necessary, they are identified by letters (a, b, c,
etc.) following the hatchery abbreviation. Lot 7-En-a and 7-En-b designate
two sublots received in the same year from the Ennis National Fish
Hatchery.
Identification of fish species should be made on all management records.
The abbreviations for National Fish Hatcheries and the states are present-
ed in Appendix E.
Lot History Production charts should be prepared at the end of each
month for all production lots of fish reared in the hatchery. This chart pro-
vides valuable accumulated data on individual lots and is useful in evaluat-
ing the efficiency and the capability of a hatchery. Information recorded on
the chart will be used in completing a quarterly distribution summary and
a monthly cumulative summary. These forms were developed for salmon
and trout hatcheries. Parts of them are readily adaptable to intensive cul-
ture of coolwater and warmwater fishes. Presently, information needed to
estimate the size of fry at initial feeding (which allows projections of
growth and feed requirements from this earliest stage) is lacking for species
other than salmonids. For the time being, cool- and warmwater fish cultu-
rists should ignore that part of the production chart, and pick up growth
118 IISII HATCHERY MANAGEMENT
and feed projections from the time fry become large enough to be handled
and measured without damage.
The following definitions and instructions relate to the Lot History Pro-
duction form used in National Fish Hatcheries (Figure 40).
DEFINITIONS
Date of initial feeding: This is the day the majority of fry accept feed or, in
the case of fish transferred in, the day the lot is put on feed.
Number at initial feeding: If lots are inventoried at initial feeding, this
number will be used. If lots are not inventoried, the number of eggs re-
ceived or put down for hatching, minus the number of egg or fish deaths
recorded prior to initial feeding, will determine the number on hand at ini-
tial feeding.
Weight at initial feeding: The weight on hand at initial feeding should be
recorded by inventory when possible. Otherwise, multiply the number at
initial feeding, in thousands, by the weight per thousand: (thousands on
hand) x (weight/1,000 fish) = weight on hand.
Length at initial feeding: The length of fish at initial feeding, in inches,
can be found from the appropriate length-weight table in Appendix I cor-
responding to the size (weight per 1,000 fish).
Size at initial feeding: For this chart, sizes of fish will be recorded as
weight in pounds per 1,000 fish (Wt/M). When sample counts are not
available, the size at initial feeding can be determined from Table 16.
INSTRUCTIONS
Column 1: Record the number of fish on hand the last day of the month.
This is the number of fish in Column 1 of the previous month's chart,
minus the current month's mortality (Column 4), minus the number of fish
shipped out during the current month (Column 5), plus the additions for
the current month (Column 7). This figure may be adjusted when the lot is
inventoried. Report in 1,000's to three significant figures, i.e., 269, 200,
87.8, etc.
Column 2: Record the inventory weight of the lot on the last day of the
current month. When inventory figures are not available, the number on
hand the last day of the current month (Column l), multiplied by the sam-
ple count size (Column 3), equals the weight on hand at the end of the
current month.
Column 3: Record the size of the fish on hand the last day of the current
month as determined by sample counts.
Weight offish in sample , ^_,. x.r . , /, ^^^ r. i
— — ^ ^ — X 1,000 = Weight/ 1,000 fish
Number of fish in sample
Column 4: Record the total deaths of feeding fish in the lot for the
current month.
HATCHERY OPERATIONS
119
STATION
LOT HISTORY PRODUCTION
LOT NUMBER
SPECIES
INITIAL FEEDING
DATE
NUMBER OF FISH
WEIGHT OF FISH
LENGTH
WEIGHT PER 1000 FISH
M
0
FISH ON HAND
END OF MONTH
WEIGHT
PER 1000
MORTAL
ITY
FISH SHIPPED
FISH ADDED
WEIGHT GAIN
(POUNDS!
FOOD FED
(POUNDS)
FEED
COST
CONVERSION
UNIT FEED
COST TO DATE
N
T
H
NUMBER
1000s
WEIGHT
POUND
NUMBER
NUMBER
WEIGHT
NUMBER
WEIGHT
MONTH
TO DATE
MONTH
TO DATE
TO DATE
MONTH
TO
DATE
PER
POUND
PER
1000
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
TOTAL
DAY
OF
YEAR
(JUL-
IAN)
M
0
N
T
H
DIET
IDENTIFICATION
LENGTH ON
LAST DAY
OF MONTH
CURRENT
MONTHS
LENGTH INCREASE
NO DAYS
SINCE INITIAL
FEEDING
AVERAGE DAILY
LENGTH INCREASE
(INCHES)
LENGTH
INCREASE
30 DAY
MONTH
TEMPERATURE
UNITS
TEMPERATURE
UNITS
PER INCH GAIN
INCHES
INCHES
FOR MO
TO DATE
FOR MO
TO DATE
FOR MO
TO DATE
18
19
20
21
22
23
24
25
26
27
28
TOTAL
PERCENT SURVIVAL UNTIL TRANSFERRED. RELEASED OR DISTRIBUTED SAC FRY .
REMARKS
FEEDING FRY .
FISH.
Figure 40. Production form for recording lot history data. Temperature units
are monthly temperature units, which equal TF above 32°F for the average
monthly water temperature.
120
I ISH HATCHERY MANAGEMENT
Table 16. the size of salmonid fry at initial feeding, based on the size of
THE eyed egg listed AND THE CORRESPONDING WEIGHT PER 1,000 FRY.
INITIAL FEEDING
EYED EGG
INITIAL FEEDING
EYED EGG
WEIGHT PER
WEIGHT PER
(NUMBER
1,000 FRY
LENGTH
(NUMBER
1,000 FRY
LENGTH
PER OUNCE)
(POUNDS)
(INCHES)
PER OUNCE)
(POUNDS)
(INCHES)
200
0.53
1.10
460
0.23
0.83
210
0..50
1.08
470
0.22
0.82
220
0.48
1.06
480
0.22
0.81
230
0.46
1.05
490
0.21
0.81
240
0.44
1.03
500
0.21
0.80
2.50
0.42
1.02
510
0.21
0.75
260
0.40
1.00
520
0.20
0.79
270
0.39
0.99
530
0.20
0.79
280
0.38
0.98
540
0.19
0.78
290
0.36
0.96
5.50
0.19
0.78
300
0.35
0.96
560
0.19
0.75
310
0.34
0.95
570
0.18
0.77
320
0.33
0.94
580
0.18
0.77
330
0.32
0.93
590
0.18
0.76
340
0.31
0.92
600
0.18
0.76
350
0.30
0.91
610
0.17
0.75
360
0.29
0.90
620
0.17
0.74
370
0.28
0.89
630
0.17
0.74
380
0.28
0.88
640
0.16
0.74
390
0.27
0.88
6.50
0.16
0.74
400
0.26
0.87
660
0.16
0.73
410
0.26
0.86
670
0.16
0.73
420
0.25
0.85
680
0.15
0.73
430
0.24
0.84
690
0.15
0.72
440
0.24
0.84
700
0.15
0.72
450
0.23
0.83
Column 5: Record the total number of fish shipped from the lot for the
current month.
Column 6: Record the total weight of the fish shipped during the current
month.
Column 7: Record the total number of fish added to the lot in the
current month.
Column 8: Record the total weight of the fish added to the lot in the
current month.
Column 9: Record the gain in weight for the current month. This is equal
to Column 2 (this month) — Column 2 (last month) + Column 6 — Column
8.
Column 10: Record total weight gain to date. This is equal to Column 10
(last month) + Column 9 (this month).
HATCHERY OPERATIONS 121
Column 11: Record the total food fed for the current month from daily
records.
Column 12: Record the total food fed to date. This is equal to Column
12 (last month) + Column 11 (this month).
Column 13: Record the cumulative cost of fish food fed to date. This is
equal to Column 13 (last month) + cost for this month. Report to the
nearest dollar.
Column 14: Record feed conversions for this month. This is equal to
Column 1 1 -^ Column 9. Record conversion to two decimal places.
Column 15: Record the conversion to date. This is Column 12 -i- Column
10.
Column 16: Record to the nearest cent, the unit feed cost per pound of
fish reared. This is Column 13 ^ Column 10.
Column 1 7: Record, to the nearest cent, the unit feed cost to date per
1,000 fish. This is (Column 3 — the weight per 1,000 fish reported at initial
feeding) x Column 16.
Column 18: Identify the type of diet fed for the current month including
the cost per pound.
Column 19: Record, to two decimal places, the length of the fish on hand
the last day of the current month. This comes from the length-weight table
appropriate for Column 3.
Column 20: Record the increase in fish length for this month. For new
lots, this is Column 19 — the length at initial feeding. For pre-existing lots,
this is Column 19 (this month) — Column 19 (last month).
Column 21: Record the number of days since the date of initial feeding.
Column 22: Record, to two decimal places, the average daily increase in
fish length. For new lots, this is Column 20 ^ the number of days the lot
was on feed. For pre-existing lots, this is Column 20 ^ the number of days
in the month.
Column 23: Record, to two decimal places, the average daily length in-
crease to date. This is Column 19 — length at initial feeding -^ Column 21.
Column 24: Record, to two decimal places, the length increase during a
30-day unit period. This is Column 22 x 30.
Column 25: Record the monthly mean water temperature in degrees
Fahrenheit. Monthly Temperature Units (MTU) available per month are
the mean water temperature minus 32°F. If a lot of fish was started part
way through the month, the MTU reported for this column must reflect
the actual days the lot was on feed. For example, if fish were on feed from
June 16th through June 30th, the MTU available to the lot must reflect 15
days. A detailed explanation of Monthly Temperature Units is given on
page 62.
Column 26: Record, to one decimal place, the temperature units available
to date. This is Column 26 (last month) + Column 25 (this month).
122 FISH HATCHERY MANAGEMENT
Column 27: Record the Monthly Temperature Units per inch of gain for
the current month. For new lots, this is Column 25 ^ Column 20. For pre-
existing lots, this is Column 25 ^ Column 24.
Column 28: Record the Monthly Temperature Units required per inch of
gain to date. This is Column 26^ (Column 19 — length at initial feeding).
TOTALS AND AVERAGES
Totals in Columns 4, 5, 6, 7, and 8 are the sums of entries in their respec-
tive columns.
The last entry for Columns 10, 12, 13, 15, and 16 is used as the total for
the respective column.
For Column 17, the aggregate feed cost per 1,000 fish is Column
13 H- Column 5.
Totals or averages for Columns 18 through 28 have been omitted for this
form.
Hatchery Production Summary
The Hatchery Production Summary is prepared at the end of each month
(Figure 4l). Entries on this form are taken from the Lot History Produc-
tion (LHP) chart. Hatchery Production Summaries provide cumulative
monthly information for all production lots reared at the hatchery on an
annual basis. Once a lot has been entered on this form, the lot should be
carried for the entire year. When a lot is closed out during the year, entries
in Columns 2, 3, 4, 13, and 14 will be omitted for the month the lot was
closed out and for the remaining months in that fiscal year.
DEFINITIONS
Density index is the relationship of the weight of fish per cubic foot of water
to the length of the fish.
Flow index is the relationship of the weight of fish per gallon per minute
flow to the length of fish.
Weight of fish is the total weight on hand from Column 3.
Length of fish is the average length of fish on hand from Column 4.
Cu ft water is the total cubic feet of water in which each lot is held the
last day of the month.
GPM flow is the total hatchery flow used for production lots the last day
of the month. Water being reused though a series of raceways is not con-
sidered; however, reconditioned water (e.g., through a biological filter) is
included in the total flow.
HATCHERY OPERATIONS
123
STATION
HATCHERY PRODUCTION SUMMARY
PERIOD COVERED
OCT 1, 19 through
DENSITY INDEX
FLOW INDEX
TOTAL FLOW
SPECIES
FISH ON HAND
END OF MONTH
FISH
SHIPPED
THIS FY
GAIN
THIS FY
FISH FEED
EXPENDED
CONVER
SION
UNIT FEED
COST
TU
PER
INCH
TU
TO
DATE
LENGTH
INCREASE
AND
LOT
PER
LB
PER
1000
30 DAY MONTH
NUMBER
WEIGHT
LENGTH
NUMBER
WEIGHT
POUNDS
COST
INCHES
1
2
3
4
5
6
7
8
9
lO
11
12
13
14
TOTAL
AVERAGE
Figure 41. The hatchery production summary is used to record the monthly
total and average production data. T.U. denotes temperature units; F.Y. is fiscal
year.
INSTRUCTIONS
Compute the following indexes.
Density Index
weight of fish
Flow Index =
(average length of fish) (cu. ft. water)
weight of fish
(average length of fish) (GPM flow)
Column 7: List the species of fish and the lot number.
Column 2: Record the number of fish on hand at the end of the month
for the individual lots from Column 1 of the LHP Chart.
Column 3: Record the weight of fish on hand at the end of the month for
the individual lots from Column 2 of the LHP chart.
Column 4: Record the size of the fish on hand at the end of the month
for the individual lots from Column 19 of the LHP chart.
Column 5: Record the total number of fish shipped from the individual
lots during the year, from Column 5 of the LHP chart.
Column 6: Record the gain in weight to date for the individual lot during
the year, from Column 10 of the LHP chart.
124 FISH HAICHERY MANAGEMENT
Column 7: Record the total food fed to date for the individual lot for the
fiscal year only, from Column 12 of the LHP chart.
Column 8: Record the total cost of food fed to date for the individual lot
during the year, from Column 13 of the LHP chart.
Column 9: Record the feed conversion to date. This is Column 7 (this
form) -^ Column 6 (this form).
Column 10: Record the unit feed cost per pound of fish to date. This is
Column 8 (this form) -^Column 6 (this form).
Column VI: Record the unit feed cost per 1,000 fish for the individual lot
during the year, from Column 17 of the LHP chart. If a lot is carried over
for two years, subtract the size (weight/ 1,000) recorded at the end of the
year in Column 3 of the LHP chart from the size (weight/1,000) recorded
the last day of the current month and multiply the difference by the unit
feed cost per pound recorded in Column 10 of the Hatchery Production
Summary form.
Column 12: Record the current month entry from Column 28 of the LHP
chart.
Column 13: Record the current month entry from Column 26 of the LHP
chart.
Column 14: Record the current month entry from Column 24 of the LHP
chart.
TOTALS AND AVERAGES
Column 2: Record the total number of fish on hand at the end of the
current month.
Column 3: Record the total weight of fish on hand at the end of the
current month.
Column 4: Record the weighted average length of fish on hand at the end
of the current month. Multiply each entry in Column 2 by the correspond-
ing entry in Column 4. Add the respective products and divide this sum by
the total number on hand from Column 2.
Column 5: Record the total number of fish shipped this fiscal year.
Column 6: Record the total gain in weight for the hatchery for this fiscal
year.
Column 7: Record the total pounds of fish food fed for this fiscal year.
Column 8: Record the total cost of fish food fed for this fiscal year.
Column 9: Record the food conversion to date. This is Column
7 ^ Column 6.
Column 10: Record the cost per pound gain to date. This is Column
8 -^ Column 6.
Column 11: Record the average unit feed cost per 1,000 fish reared to
date. This is Column 8 -^ (Column 2 + Column 5).
HATCHERY OPERATIONS
125
POND NO
AREA.
POND
.ACRE FT
RECORD
STATION .
. YEAR .
Date
Pond
Species
Stocked
STOCKED
SHIPPED
Date
Applied
N
P
Organic
Resu
fs
Cost
Filled
Date
Number
Weight
Date
Number
Weight
Total
Total
Fertilizer
COST PER POUND
FISH PRODUCED
Hprhiride
TRANSFERRED TO OTHER UNITS FOR FURTHER
REARING & NOT CHARGED TO FISH SHIPPED
Date
Number
Size
Weight
To Pond No
AMOUNT & KINDS OF MATERIALS USED FOR
WEED & PEST CONTROL
DATE
Applied
Trade Name
Strength
Amount
Method
Results
Cost
Total
Total
POND RECORD
SPECIES
PRODUCTION
PER ACRE
TOTAL
FOR POND
NUMBER
PER
POUND
FOR BROOD POND RECORD
NUMBER
WEIGHT
NUMBER
WEIGHT
Niimhor "f fry harvo^tod
Niimhpr nf fry harup<;tpri ppr fpm^lp
REMARKS
TOTAL
DISEASE CONTROL DATA
DATE
TYPE
TREATMENT
COST
EST. MORTALITY
•
TOTAL
Figure 42. Pond record form used to record fish production, chemical treat-
ments, and disease control data.
126 FISH HATCHERY MANAGEMENT
Column 12: The sum of the entries in this column divided by the number
of entries gives the average Temperature Units (TU's) required per one
inch of growth to date.
Column 13: The sum of the entries in this column divided by the number
of entries gives the average Temperature Units (TU's) to date.
Column 14: The sum of the entries in this column divided by the number
of entries is the average length increase to date.
Warmwater Pond Records
Important recordkeeping information for warmwater fish pond manage-
ment is shown in Figure 42. Accurate historical data concerning fertiliza-
tion and pond weed control can be useful in evaluating the year's
production.
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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
'«:•;!:■:'■
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MM
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>://.'.;j(t
: i'/.-'-jfeSI
l^fc" •"'•'•••'
l^Bt-'t^!':;*;'
M:ii^::::i:il:i
Figure 44. Sexual dimorphism develops in mature broodfish. The male blue-
gill becomes much darker than the female and changes body shape (upper
panel). Male salmon also show changes in color and the jaw becomes hooked,
forming a kype (lower panel).
140 FISH HATCHERY MANAGEMENT
Forage Fish
Forage species cultured as feed for predatory broodfish vary depending on
the species of broodfish being maintained. Several factors must be con-
sidered when a forage organism is selected. The forage must not be too
large for the predator to consume nor too small to provide adequate nour-
ishment, and should be able to reproduce in adequate numbers at the time
v^hen it is needed. Forage species should have the right shape and
behavior to attract the predator, be easily captured by the broodfish, and
require little pond space to rear. If the forage can be obtained commercial-
ly at a reasonable cost, production space and time will be saved at the
hatchery.
Species of forage fish propagated as food include suckers, fathead min-
nows, goldfish, golden shiners and Tilapia. Shad, herring, bluegills, and
trout are used to a lesser degree as forage fish. Suckers, fathead minnows,
and goldfish usually are used with coolwater broodfish. These species are
early spawners, making them available as forage when needed by the
broodfish. Northern pike, walleye, and muskellunge prefer a long slender
fish with good body weight, such as the sucker.
Culture of forage fish varies with the species; some notes about the most
frequently utilized species follow.
WHITE SUCKER
White suckers occur east of the Great Plains from northern Canada to the
southern Appalachian and Ozark mountains. They prefer clearwater lakes
and streams. In early spring, they run upstream to spawn in swift water
and gravel bottoms, although they also will spawn to some extent in lakes
if there are no outlets and inlets. White suckers have diversified feeding
habits, but prefer planktonic crustaceans and insect larvae.
Broodfish usually are taken from streams during the natural spawning
run. These fish are hand-stripped and the eggs are hatched in jars. After
hatching, the fry are stocked in ponds prepared for the production of zoo-
plankton. Stocking rates vary with the size of the desired forage:
40,000-60,000 per acre for 1-2-inch fish; 20,000-40,000 for 2-4-inch fish;
5,000-20,000 for 4-6- inch fish.
Ponds of moderate fertility usually produce the most suckers. Sterile
ponds do not produce enough food for white suckers and excessively fertile
ponds often produce too much aquatic vegetation. Ponds with large popu-
lations of chironomid fly larvae (bloodworms) in the bottom muds will
produce good sucker crops year after year. Loam and sandy- loam soils pro-
duce the best chironomid populations; peat and peat-loam ponds are ade-
quate for this purpose, but silt and clay- loam ponds are poor. Ponds with
BROODSTOCK, SPAWNING, AND EGG HANDLING 141
heavy, mosslike growths of filamentous algae over the bottom do not pro-
duce good crops of suckers.
After the suckers attain a length of 1-2 inches, an organic fertilizer such
as manure can be added to increase the production of natural food. Suck-
ers will adapt to formulated feeds as a supplemental diet.
FATHEAD MINNOW
The fathead minnow occurs throughout southern Canada and in the
United States from Lake Champlain west to the Dakotas and south to
Kentucky and the Rio Grande River. It feeds mainly on zooplankton and
insects. The spawning season extends from May until the latter part of
August. The eggs are deposited on the underside of objects in a pond, and
hatch in 4.5 to 6 days. Mature fathead minnows range in length from 1^
to 4 inches, the male being consistently larger than the female. The life
span of hatchery-reared fathead minnows is 12 to 15 months, depending on
the size of the fish at maturity. During the early spawning season a large
majority of the males usually die within 30 days after the onset of spawn-
ing activities, and a large percentage of the gravid females will die within
60 days. One- to two-inch immature fatheads, even though only a year old,
die shortly after they become gravid at an age of about 15 months. Thus,
the older fish in a pond should be used as forage after they have spawned.
Ponds for fathead minnows should have flowing, cool water from a
spring or well. The ponds should not be larger than one acre or smaller
than 0.25 acre. The water depth should average about 3 feet and range
from 2 feet at the shallow end to 6 feet at the drain. The pond should be
equipped with a controllable water inlet and drain. Ponds to be used for
reproduction should be lined along two banks with rocks ranging in size
from 6 to 12 inches in diameter, or with tile, extending from six inches
above the planned water level to two feet below it. This material provides
spawning surfaces for the minnows.
The brood ponds should be stocked in early April with about 60% adult
minnows and 40"n immature fish. Both adults and juveniles are used as
breeders because of the species' short life span. In this way, one can be
sure of a continuous, uninterrupted supply of newly hatched fry. The
brood ponds should be stocked at the rate of 15,000 to 25,000 fish per acre.
Fathead minnows normally start spawning activities during the latter
part of April or at a time when the pondwater temperature reaches 65°F.
They spawn intermittently throughout the summer, provided the water
temperature does not rise above 85°F. When this temperature is reached,
spawning ceases, and is not resumed until the pond is cooled by a weather
change or by an increased flow of spring water. Within a few days of
spawning activity, small fry will be seen swimming near the surface, a few
142 FISH HATCHERY MANAGEMENT
feet out from shore. As soon as fry become numerous, they can be captured
with a small fry seine and transferred to rearing ponds at the rate of
300,000 to 600,000 fry per acre. From this stocking rate, a harvest of about
150,000 fathead minnows can be expected.
During the first few weeks of life following transfer to the rearing pond,
fry grow very rapidly. Within 4 to 8 weeks, many of these fish will mature
and begin to spawn. When this occurs, the pond may become overstocked
and the fish become stunted. The excess fry should be transferred to
another pond or destroyed.
A productive pond should have a good plankton density; a Secchi disk
reading of about 12 inches should be maintained. Fathead minnows readily
accept a formulated diet, usually in the form of meal. The amount recom-
mended is 2% of body weight per day, not to exceed 25 pounds per day
per acre. In 6 to 10 weeks this procedure will produce 2-inch forage organ-
isms.
GOLDFISH
Goldfish are good forage fish. This is a hardy species that prospers during
hot weather. Goldfish feed largely on plankton, but will take insects and
very small fish. They reproduce in large numbers and grow rapidly.
Goldfish normally start spawning when the water reaches 60°F and con-
tinue to spawn throughout the summer if the temperature remains above
60°F and the fish are not overcrowded. The favorite spawning time is right
after sunrise on sunny days. The females lay their eggs on grass, roots,
leaves, or similar objects. A female goldfish may lay 2,000 to 4,000 eggs at
one time and may spawn several times during the season. The eggs are
adhesive and stick to any object they touch. The live eggs are clear and
turn brown as they develop; dead eggs are cloudy and opaque. The eggs
hatch in 6 to 7 days at a water temperature of 60°F.
Goldfish averaging 0.25 to 0.75 pound reproduce well and should be
used for broodstock. Broodstock overwintered in crowded ponds will not
spawn in the ponds. Maximum egg production is obtained by keeping the
broodfish in the overwintering pond until after the last spring frost. Then
the fish are stocked in the production ponds at the rate of 100-200 adults
per acre without danger of frost damaging the eggs or fry. Goldfish will ac-
cept formulated feeds and feeding rates should be set to produce 2-3-inch
fish in the shortest time.
Broodstock ponds should be fertilized to insure that phytoplankton pro-
duction is sustained all summer. Secchi disk readings should be 18 inches
or less.
Ponds should contain suitable natural vegetation or artificial spawning
material. The water level is commonly dropped in early spring to en-
courage the growth of grass along the shoreline. When the ponds are filled,
BROODSTOCK, SPAWNING, AND EGG HANDLING 143
this grass provides spawning sites. Aquatic plants are also utilized as
spawning sites. If natural vegetation is absent or scarce, hay, straw, or mats
of Spanish moss may be anchored in shallow areas for spawning purposes.
If the eggs are allowed to hatch in the ponds where they are laid, the
adults will stop spawning when the pond becomes crowded with young
fish. If the eggs are removed and transferred to clean ponds to hatch, the
uncrowded adults will continue to spawn all summer. In general, ponds
containing both young and adults should produce up to 100,000 fingerlings
per acre. In intensive situations, where a heavily stocked brood pond pro-
vides fry for eight or ten rearing ponds, production will reach 200,000 to
300,000 goldfish per acre.
GOLDEN SHINER
Golden shiners are widely distributed from eastern Canada to Florida, and
westward to the Dakotas and Texas. They prefer lakes and slack-water
areas of rivers. Young golden shiners eat algae and cladocerans. Adults will
consume a variety of organisms, from algae and zooplankton to mollusks
and small fish. Eggs are adhesive and are scattered over filamentous algae
and rooted aquatic plants.
Golden shiner breeders should be at least 1 year old, and 3-8 inches
long. About 50% of the broodstock should be shorter than 5 inches in
length; otherwise the stock might be predominantly females, as the males
are consistently smaller than females. The stocking rate in large ponds,
where the fry will remain with the adults, should range from 2,000 to 3,000
fish per acre. In ponds where egg or fry removal is planned, the stocking
rate should be 4,000-8,000 adults per acre.
Golden shiners start spawning activity when the water temperature rises
above 65°F, but if the temperature exceeds 80°F, spawning ceases. During
this period, at least four or five distinct spawning cycles occur, separated
by periods of about 4 or 5 days. Spawning usually starts early in the morn-
ing and terminates before noon. The females deposit their eggs on any type
of submerged plants or debris. At temperatures of 75-80°F, fertilized eggs
hatch within four days.
Shortly thereafter, fry congregate in schools near the surface along the
shoreline, where they can be collected with a fine- mesh net and transferred
to growing ponds. Because adults often cannibalize the young if the two
age groups are left together, the fry should be transferred to other ponds at
the rate of 200,000-300,000 fry per acre. Successful production will yield
75,000-150,000 2-3- inch fish per acre. In ponds where the fry remain with
the adults, 60,000 shiners per acre is considered good production.
Golden shiners, like most other forage species, can be fed a supplemental
formulated diet to increase growth rate.
144 FISH HATCHERY MANAGEMENT
When golden shiners are seined from a pond, the seine should be of cot-
ton or very soft material because the scales are very loose on this species.
Harvesting at water temperatures below 75°F will reduce stress.
TILAPIA
Fish of the genus Tilapia are native to Africa, the Near East, and the
Indo-Pacific, but are presently widely distributed through the world. Tila-
pia are cichlids, and most species are mouth brooders; females incubate
eggs and newly hatched fry in their mouth for 10-14 days. When the fry
are free- swimming they begin feeding on algae and plankton.
Tilapia tolerate temperatures in excess of 100°F, but do not survive
below 50-55°F. Consequently, their culture as forage fish is restricted to
the southern United States. Even there, broodfish usually need to be
overwintered in water warmer than 55°F. Most tilapia are very durable and
tolerant, able to survive low oxygen and high ammonia concentrations.
Tilapia are excellent forage species in areas where culture is possible:
easy to propagate; prolific; rapid growing; disease-resistant; and hardy for
transferring in hot weather. Rearing ponds should be prepared and fertil-
ized to produce an abundance of phytoplankton. If 200-250 adults are
stocked in a pond after the water temperature is 75°F or above, they will
produce 100,000 juveniles of 1-3 inches in 2-3 months. The adults will
spawn and rear a new brood every 10-14 days throughout the summer.
Tilapia accept dry food, and supplemental feeding will increase the growth
rate.
Improvement of Broodstocks
Fish stocks may be improved by several methods, some of which are: selec-
tive breeding, the choosing of individuals of a single strain and species; hy-
bridization, the crossing of different species; and crossbreeding, the mating
of unrelated strains of the same species to avoid inbreeding.
SELECTIVE BREEDING
Selective breeding is artificial selection, as opposed to natural selection. It
involves selected mating of fish with a resulting reduction in genetic varia-
bility in the population.
Criteria that often influence broodfish selection for selective breeding
include size, color, shape, growth, feed conversion, time of spawning, age at
maturity, reproductive capacity, and past survival rates. These may vary
with conditions at different hatcheries. No matter what type of selection
BROODSTOCK, SPAWNING, AND EGG HANDLING 145
program is chosen, an elaborate recordkeeping system is necessary in order
to evaluate progress of the program.
Inbreeding occurs whenever mates selected from a population of
hatchery broodfish are more closely related than they would be if they had
been chosen at random from the population. The extent to which a partic-
ular fish has been inbred is determined by the proportion of genes that its
parents had in common. Inbreeding leads to an increased incidence of
phenotypes (visible characteristics) that are recessive and that seldom occur
in wild stocks. An albino fish is an example of a fish with a recessive
phenotype. Such fish typically are less fit to survive in nature. Animals
with recessive phenotypes occur less frequently in populations where mat-
ing is random.
Problems that can arise after only one generation of brother-sister mat-
ing include reduced growth rate, lower survival, poor feed conversion, and
increased numbers of deformed fry. Broodstock managers must be aware of
the problems that can result from inbreeding and employ techniques that
will minimize potential breeding problems. To avoid inbreeding, managers
should select their broodstocks from large, randomly mated populations.
Significant differences have been found in rainbow trout between females
of different ages in egg volume, egg size, and egg numbers per female.
Three-year-old females provide a higher percentage of eyed eggs and
larger, more rapidly growing fingerlings than two-year-old females. Growth
of the fingerlings is influenced by the age of the female broodfish and is
directly related to the size of the egg. The egg size is dependent on the age
and size of the female broodfish. Generally, the egg size increases in fe-
males until the fifth or sixth year of life and then subsequently decreases.
If inbreeding is avoided, selective breeding is an effective way to im-
prove a strain of fish. A selective breeding program for rainbow trout at
the Manchester, Iowa National Fish Hatchery resulted in fish 22% heavier
than fish hatched from unselected individuals. Selective breeding in trout
has increased growth rate, altered the age of maturation, and changed the
spawning date.
A system has been developed for maintaining trout broodstocks for long
periods with lower levels of inbreeding than might be experienced in ran-
dom mating. It requires the maintenance of three or more distinct breeding
lines in a rotational line-crossing system. The lines can be formed by: (a)
an existing broodstock arbitrarily subdivided into three groups; (b) eggs
taken on three different spawning dates and the fry reared separately to
adulthood; or (c) three different strains or strain hybrids. Rotational line-
crossing does nothing to reduce the level of inbreeding in the base
broodstock, but serves only to reduce the rate at which further inbreeding
occurs. Consequently, it is essential that a relatively high level of genetic
diversity be present in the starting broodstock. The use of three different
146
FISH HATCHERY MANAGEMENT
0
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s
s
s
N
S
z
o
}
.*-
1—
<
cc
1
UJ
2
LU
CJ
V
s
s
N
S
V
s
'
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2
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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
^
,r^:'
\
Figure 47. Spawning receptacles for channel catfish are placed in the pond
before it is filled with water.
requires close inspection of nests with an underwater viewer. The method
allows the fish culturist to collect eggs, if so desired, for subsequent hatch-
ing under controlled conditions. It has the added advantage of allowing the
culturist to respawn broodfish during the height of the season.
Culture of bluegills and other sunfishes is relatively simple. The
spawning-rearing pond method almost always is used for culturing these
species, although a few hatcheries transfer fry to rearing ponds. Best
spawning success with bluegills is obtained by using mature broodfish
weighing 0.3 to 0.6 pound. However, good production has been obtained
with 1-year-old fish averaging 0.10—0.15 pound at spawning time. When
broodstock of this latter size is used, an increased number of fish per acre
is needed to adequately stock the pond. Use of yearling broodstock gen-
erally results in less uniform spawning, which tends to cause greater size
variation in the fingerlings produced. Bluegills spawn when water tempera-
tures approach 80°F and several spawns can be anticipated during the sum-
mer.
Catfish generally are spawned by either the open- pond or pen method.
In the open-pond method, spawning containers such as milk cans, nail
kegs, or earthenware crocks, are placed in the pond with the open end to-
ward the center of the pond (Figure 47). It is not necessary to provide a
spawning receptacle for each pair of fish, because not all fish will spawn at
the same time. Most culturists provide two or three receptacles for each
four pairs of fish. Fish will spawn in containers placed in water as shallow
as 6 inches and as deep as 5 feet. The receptacles are checked most easily
if they are in water no deeper than arm's length.
Frequency of examination of spawning containers depends on the
BROODSTOCK, SPAWNING, AND EGG HANDLING
155
number of broodfish in the pond and the rate at which spawning is prog-
ressing. In checking a container, the culturist gently raises it to the surface.
If this is done quietly and carefully, the male usually is not disturbed. Cau-
tion should be used, because an attacking male can bite severely. If the wa-
ter is not clear, the container can be slowly tilted and partly emptied.
Catfish eggs may be handled in different ways. The eggs may be re-
moved, or left in the spawning pond to hatch and the fry reared in the
ponds. Removal of the eggs has several advantages. It minimizes the
spread of diseases and parasites from adults to young, and provides for egg
disinfection. The eggs are protected from predation and the fry can be
stocked in the rearing ponds at known rates.
The pen method of spawning catfish utilizes pens about 10 feet long and
5 feet wide located in a row in the spawning ponds (Figure 48). They are
constructed of wood, wire fencing, or concrete blocks. They should be en-
closed on all four sides but the bank of the pond may be used as one side.
The sides should be embedded in the pond bottom and extend at least 12
inches above the water surface to prevent fish from escaping. Water should
be 2-3 feet deep.
Location of the spawning container in the pen is not critical, but gen-
erally it faces away from the pond bank. Broodfish are sexed and paired in
the pens. Usually the best results occur when the male is equal in size to,
or slightly larger than, the female. This discourages the female from eating
the eggs that are being guarded by the male. After spawning, eggs and
parent fish may be removed and another pair placed in the pen. Some-
times, the female is removed as soon as an egg mass is found, and the male
is then allowed to hatch the eggs. Usually, containers are checked daily
and the eggs removed to a hatching trough. A male may be used to spawn
several females.
Figure 48. Channel catfish spawning pens. Note spawning receptacle (arrow).
(FWS photo.)
156 FISH HATCHERY MANAGEMENT
The pen method has several advantages. It provides close control over
the time of spawning, allows the pairing of selected individuals, facilitates
removal of spawned fish from the pond, protects the spawning pair from
intruding fish, and allows the injection of hormones into the broodfish.
The aquarium method of spawning catfish is a modification of the pen
method. A pair of broodfish is placed in a 30- to .50-gallon aquarium with
running water. The broodfish are induced to spawn by the injection of hor-
mones. Tar-paper mats are placed on the bottom of the aquarium. As the
eggs are deposited and fertilized, they form a large gelatinous mass, and
adhere to the mat. The eggs readily can be removed with the mat. It is an
intensive type of culture; many pairs of fish can be spawned successfully in
a single aquarium during the breeding season. Each spawn is removed im-
mediately to a hatching trough for incubation.
In methods involving the use of hormones, only females ready to spawn
should be used. Males need not be injected with hormones, but should be
about the same size or larger than the females with which they are paired.
If the male attacks the female, he should be removed until after the female
has been given one to three additional hormone injections. He then may be
placed with the female again. Males may be left to attend the eggs in the
aquarium or, preferably, the eggs are removed to a hatching trough.
Striped bass have been spawned in circular tanks. This method generally
requires a water flow of 3 to 10 gallons per minute per tank. Six-foot diam-
eter tanks are most desirable. Broodfish are injected with hormones and at
least two males are put in a tank containing one female. After spawning,
the broodfish are removed. Striped bass eggs are free-floating, and if the
males have participated in spawning, the water will appear milky. The eggs
can be left circulating in the tank until they hatch or removed with a
siphon to aquaria for hatching. Some egg loss can be expected due to
mechanical damage if they are transferred from tank to aquaria. When fer-
tilized eggs are allowed to hatch in the tank, the fry will become concen-
trated around the edge of the tank after 4 or 5 days and they can then be
dipped out and transferred to rearing facilities.
Artificial Spawning Method
The artificial method of spawning consists of manually stripping the sex
products from the fish, mixing them in a container, and placing the fertil-
ized eggs in an incubator. The following description of egg stripping and
fertilization is widely applicable to many species of fish, including coolwa-
ter and warmwater species (Figure 49).
Any spawn- taking operation should be designed to reduce handling of
the fish. Anesthetics should be used when possible to reduce stress. In
hand- stripping the eggs from a female, the fish is grasped near the head
with the right hand, and the left hand grasps the body just above the tail.
BROODSTOCK, SPAWNING, AND EGG HANDLING
157
Figure 49. Equipment used for spawning wild coolwater fishes (trap net shown
in background). The males and females are held separately in holding tanks con-
taining an anesthetic (A, B). A bench with a spawning pan (C) is provided for
the spawn taker. (FWS photo.)
The fish is then held with the belly downward over a pan, and the eggs are
forced out gently by a massaging movement beginning forward of the vent
and working back toward it. Care should be taken to avoid putting pres-
sure too far forward on the body as there is danger of damaging the heart
or other organs (Figure 50). After the eggs have been extruded, a small
amount of milt (sperm) is added from a male fish. Milt is expressed from a
ripe male in much the same manner as the eggs are taken from a female
(Figure 5l). If either eggs or milt do not flow freely, the fish is not suffi-
ciently ripe and should not be used. The fish should be examined frequent-
ly, as often as twice a week, to determine ripeness. Fish rarely spawn of
their own accord under hatchery conditions, and, if they are not examined
for ripeness frequently, overripe eggs will result. Muskellunge, however,
will often spawn on their own accord.
The two generally accepted procedures for handling eggs during fertili-
zation are often referred to as the wet and dry methods. In the dry method
of fertilization, water is not introduced before the eggs are expressed into
the pan, and all equipment is kept as dry as possible. Sperm and eggs are
thoroughly mixed and usually left undisturbed for 5 to 15 minutes before
158 FISH HATCHERY MANAGEMENT
Figure 50. Eggs being spawned from a northern pike female. (FWS photo.
Figure 51. Sperm being expressed from a northern pike male. (FWS photo.
BROOUSTOCK, SPAWNING, AND EGG HANDLING 159
water is added to wash the eggs for incubation. In the wet method, a pan is
partially filled with water before the eggs are expressed from the female
fish. The milt from a male is then added. Because the sperm will live less
than 2 minutes in water after being activated, considerable speed is neces-
sary by the spawn takers. The dry method generally is accepted as the best
procedure.
Eggs are washed or rinsed thoroughly after they have been fertilized and
before they are placed in the incubator. In some species, the eggs are allowed
to water- harden before being placed in an incubator. Water- hardening is the
process by which water is absorbed by the eggs and fills the perivitelline
space between the shell and yoke, causing the egg to become turgid. Precau-
tions should be taken to protect eggs from exposure to direct rays of bright
light, because both sunlight and artificial light are detrimental.
Some species, such as walleye and northern pike, have eggs that are ex-
tremely adhesive. Often during the water- hardening process of adhesive
eggs, an inert substance is added to prevent the eggs from sticking togeth-
er. Starch, black muck, clay, bentonite clay, and tannin have been used as
separating agents. Starch, because it is finely ground, does not have to be
specially prepared, but muck and regular clay must be dried and sifted
through a fine screen to remove all coarse particles and then sterilized be-
fore they can be used. Starch or clay first must be mixed with water to the
consistency of thick cream. One or two tablespoons of this mixture is ad-
ded to each pan of eggs after fertilization is completed. When the separat-
ing agent has been mixed thoroughly with the eggs, the pan is allowed to
stand for a minute. Water is then added, the separating agent is washed
from the eggs, and the eggs placed in a tub of water to harden. Constant
stirring during water hardening helps prevent clumping. The water should
be changed at least once an hour until the eggs are placed in the hatchery.
Striped bass also may be hand-stripped as an alternative to tank spawn-
ing. Both males and females of this species usually are injected with hor-
mones, as described in a later section of this chapter. An egg sample
should be taken and examined between 20 and 28 hours after a hormone
injection. Egg examination and staging requires microscopic examination.
The catheter used for extraction of the egg sample is made of glass tub-
ing, 3 millimeter O.D., with fire- polished ends. The catheter is inserted ap-
proximately 2 inches into the vent and removed with a finger covering the
end of the tube to create a vacuum that holds any eggs in place in the
tube. Extreme care is needed while the catheter is inserted into the ovary.
The catheter should be instantly removed if the fish suddenly thrashes;
such thrashing usually is immediately preceded by a flexing of the gill cov-
ers. Careful manipulation will permit the catheter to be inserted into the
vent with a minimum of force, preventing damage to the sphincter muscles.
If these muscles are torn, eggs at the posterior end of the ovary will water-
harden. The plug thus formed will prevent the flow of eggs.
160 FISH HATCHERY MANAGEMENT
The egg sample is placed on a clean glass slide with a small amount of
water. Magnification of 20 x provides a sufficiently wide field for examina-
tion of several eggs with enough magnification for detailed viewing of indi-
vidual eggs.
Egg samples should be taken between 20 and 28 hours after hormone in-
jection. Approximately 16 hours are required for the effects of the hormone
to be detected in egg development. Early in the spawning season, it is
advisable to wait 28 hours before sampling because it usually requires
about 40 hours for ovulation, and eggs taken more than 15 hours before
ovulation cannot be accurately staged. Near the peak of the natural spawn-
ing season, ovulation may occur within 20 hours following injection and it
is prudent to sample earlier.
It is impractical to predict ovulation in striped bass that are more than
15 hours from spawning as the eggs are very opaque and no difference can
be detected between 30- hour and 17- hour eggs. If opaque eggs are found,
the ovary should be resampled 12 hours later.
At about 15 hours before ovulation, the ova assume a grainy appearance
and minute oil globules appear as light areas in individual ova. This is the
first visible indication of ripening.
At 14 hours, the globules in some of the ova have become somewhat en-
larged while very small globules are evident in others. No distinct progress
can be detected in a few eggs. This mixed development may be confusing,
but in order to avoid over-ripeness, a prediction of spawning time should
be based primarily on the most advanced eggs. Uneven maturation persists
to some degree until approximately the 10- hour stage, after which develop-
ment progresses more uniformly.
At 13 hours, the majority of ova will have enlarged globules and cleared
areas occupy over one- half of the surface of most eggs.
At 12 hours, the first evidence of polarization of what eventually will be-
come the oil globule is apparent. The small globules begin fusion to form a
single globule.
At 10 hours, polarization of the oil globule is complete. The entire egg is
more translucent than in earlier stages.
At 9 hours, eggs begin to show more transparency in the yolk, although
the majority of the yolk remains translucent.
It is difficult to describe differences between eggs that are 6, 7, or 8
hours from spawning. There is a continued clearing of the nucleus, and
with experience, the worker will be able to pinpoint the exact stage. How-
ever, to avoid over- ripeness, it is best to classify eggs in any of these stages
as the 6-hour stage and attempt to hand-strip the eggs.
From 5 hours until ovulation, the ova continue to clear; at 1 hour, no
opaque areas can be detected. For more detailed information describing
this process consult the publication by Bayless 1972 (Figures 52-55).
BROODSTOCK, SPAWNING, AND EGG HANDLING 161
•*_'^^''
k
i
*
Immature Eggs
15 hrs. before Ovulation
14 hrs. before Ovulation
13 hrs. before Ovulation
12 hrs. before Ovulation
11 hrs. before Ovulation
Figure 52. Development of striped bass eggs from immaturity to 1 1 hours
before ovulation. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine
Resources Department.)
162
FISH HATCHERY MANAGEMENT
10 hrs. before Ovulation
Polarization Complete
9 hrs. before Ovulation
Nucleus Clearing
i
C
Ji^
8 hrs. before Ovulation
^W.
7 hrs. before Ovulation
o
6 hrs. before Ovulation
5 hrs. before Ovulation
Figure 53. Development of striped bass eggs from 10 to 5 hours before ovula-
tion. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources
Department.)
BROODSTOCK, SPAWNING, AND EGG HANDLING 163
4 hrs. before Ovulation
3 hrs. before Ovulation
V
2 hrs. before Ovulation
I V ..
1 hr. before Ovulation
^
Ripe Eggs at Ovulation
\
Ripe Eggs at Ovulation (SOX)
Figure 54. Development of striped bass eggs from 4 hours before ovulation to
ripeness. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine
Resources Department.)
164 FISH HATCHERY MANAGEMENT
Overripe Eggs 1 hr. (50X)
Note Breakdown at Inner
Surface of Chorion
/
V
Overripe Eggs 2 hrs. (50X)
Note Deterioration Confined
to One-Half of Egg
Overripe Eggs 1^2 hrs. (50X)
Breakdown at Inner
Surface of Chorion Persists
Overripe Egg 16 hrs. (20X)
(Dark Areas Appear White
Under Microscope)
Figure 55. Development of striped bass eggs that become overripe before ovula-
tion. (Courtesy Jack D. Bayless, South Carolina Wildlife and Marine Resources
Department.)
As ovulation occurs, eggs of striped bass become detached from the
ovarian tissue. They are deprived of parental oxygen supply, and anoxia
can result in a short period of time if the eggs remain in the body. (This
also is true for grass carp.) If eggs flov^ from the vent when pressure is ap-
plied to the abdomen, at least partial ovulation has occurred. The max-
imum period between ovulation and overripeness is approximately 60
minutes. The optimum period for egg removal is between 15 and 30
minutes following the first indication of ovulation. Eggs obtained 30
minutes after initial ovulation are less likely to hatch.
Prior to manual stripping, female striped bass should be anesthetized
with quinaldine sprayed onto the gills at a concentration of 1.0 part per
BROODSTOCK, SPAWNING, AND EGG HANDLING 165
thousand. The vent must be covered to prevent egg loss. Fish will become
sufficiently relaxed for removal of eggs within 1 to 2 minutes. Workers
should wear gloves to prevent injury from opercular and fin spines. Strip-
ping follows the procedure previously described in this chapter.
Because the broodfish of anadromous species of Pacific salmon die after
spawning, no advantage is obtained by stripping the female. Females are
killed and bled. Bleeding can be accomplished by either making an inci-
sion in the caudal peduncle or by cutting just below the isthmus and
between the opercula to sever the large artery leading from the heart to the
gills. The females are allowed to bleed for several minutes before being
spawned. A mechanical device is in common use that effectively kills and
bleeds the fish by making a deep cut through the body behind the head.
Bleeding reduces the chance of blood mixing with the eggs and reducing
fertilization. The point of the spawning knife is placed in the vent to
prevent the loss of eggs and the fish is lifted by the gill cavity and held
vertically over a bucket, such that the vent is 7-I inch above the lip of the
bucket. The fish can be held securely in this position by bracing the back
of the fish between the spawner's knees. An incision is made from the vent
to a point just below the ventral fin, around the ventral fin, back to the
center line, and upward to a point just beneath the gill cavity. If the fish is
ripe, most of the eggs will flow freely into the bucket (Figure 56). The
remaining ripe eggs can be dislodged by gently shaking the viscera. If the
fish is not ripe, gentle shaking will not dislodge the eggs and such females
should be discarded. Eggs that can only be dislodged by greater force will
be underdeveloped and infertile.
The spawning knife needs a sharp blade, but should have a blunt tip to
avoid damage to the eggs during the incision. Linoleum knives have been
used for this purpose, but personal preference usually determines the
choice of the knife.
Male salmon also are killed prior to spawning. Milt is hand stripped
directly onto the eggs in the bucket. The eggs and milt are gently mixed
by hand.
In the case of Atlantic salmon or steelhead, which may return to spawn
more than once, females should not be killed to obtain eggs. A female fish
can be spawned mechanically by placing her into a double walled, rubber
sack with the tail and vent of the fish protruding. The sack can be adjust-
ed to fit each fish. Water entering between the walls of the sack causes a
pressure against the entire fish, and will express the eggs if they are ripe.
Female fish handled in this way seem to recover more rapidly than from
other methods of stripping. Milt is collected from the males and stored in
test tubes. A male fish is held upside down and the milt is gently pressed
out and drawn into a glass tube with suction.
Reduction of damage to broodstock and increased efficiency are factors
of prime importance in any spawning operation. The use of air pressure
166
FISH HATCHERY MANAGEMENT
systems, as introduced by Australian workers and used on some trout
species in this country, have made spawning fast, easy, and efficient (Fig-
ure 57). Two to four pounds of air pressure injected into the body cavity
by means of a hollow needle will expel the eggs. The needle is inserted in
the area between the pectoral and ventral fins midway between the mid-
ventral line and the lateral line. The possibility of damage to the kidney by
needle puncture is reduced if the posterior section of this area is used. The
needle should be sterilized in alcohol for each operation to reduce the pos-
sibility of infection. It is imperative that a female be ripe if the eggs are to
flow freely. When a fish is held in the normal spawning position, a few
eggs should flow from the fish without pressure on the abdomen.
It is important that the fish be relaxed before the air pressure method is
attempted. An anesthetic should be used. The fish should be rinsed and
wiped fairly dry to prevent anesthetic dripping into the egg- spawning pan.
Air should be removed from the body cavity before the fish is returned
to the water. This is best done by installing a two-way valve and a suction
line to the needle. A supplemental line may be used to draw off the air by
mouth, or the air may be forced out by hand when a check is made for
remaining eggs, although these methods are generally not as effective.
Figure 56. Spawning Pacific salmon. Left, female is opened with a spawning
knife (cutting edge indicated by arrow). Right, milt is hand-stripped from a male
directly onto the eggs.
BROODSTOCK, SPAWNING, AND EGG HANDLING 167
Figure 57. Spawning of salmonids with air pressure.
Urine-free sperm can be collected through a pipette inserted about 0.5
inch into the sperm duct. If the male trout is gently stripped by hand, suc-
tion on the pipette will draw clean sperm out of the fish. Sperm and eggs
are then mixed together.
Factors Affecting Fertilization
Several factors may have an adverse affect on fertilization during the
spawning process at a hatchery. The contamination of either eggs or sperm
can result in low levels of fertility. In the case of most salmonids, pro-
longed exposure of either sperm or eggs to water will reduce fertility.
Sperm mixed with water are highly active for up to 15 seconds; after that,
motility declines and usually no activity is recorded after 2 minutes. Eggs
rapidly begin absorption of water shortly after contact with it and may be-
come nonviable if they have not been fertilized.
168 FISH HATCHERY MANAGEMENT
The activation of sperm, however, does require exposure to either water
or female ovarian fluid. The sperm are active for a longer period when di-
luted with an isotonic salt solution or ovarian fluid than they are in water.
Sperm activated in ovarian fluid without the addition of water will fertilize
the egg readily and have the additional benefit of prolonged viability. This
is of particular importance when large volumes of eggs must be fertilized
with small quantities of sperm.
Contaminants associated with the spawning operation also may have a
significant effect on egg fertility. Although skin mucus itself has not been
shown to reduce fertility, there is a good possibility that it can carry a con-
taminant such as the anesthetic used. Therefore, mucus should be kept out
of the spawning pan. Occasionally, blood will be ejected into the spawning
pan from an injured female; fish blood clots quickly and may plug the mi-
cropyle of the eggs, through which the sperm must enter. Occasionally,
broken eggs will result from the handling of females either prior to or dur-
ing spawning. Protein from broken eggs will coagulate and particles of
coagulated protein may plug the micropyle, thus reducing fertilization. If
large numbers of ruptured eggs occur, fertility sometimes may be increased
by placing the eggs in a 0.6% salt solution. This will cause the protein to
go back into solution.
Fertilization can be estimated by microscopically examining a sample of
eggs during the first day or two after fertilization. The early cell divisions
form large cells (blastomeres) that readily can be distinguished from the
germinal disk of unfertilized eggs at 10 x magnification. To improve the
examination of embryos, a sample of eggs can be soaked in a 10% acetic
acid solution for several minutes. Unfertilized germinal disks and the em-
bryos of fertilized eggs will turn an opaque white and become visible
through the translucent chorion. A common procedure is to examine the
eggs when the four- cell stage is reached. The rate of embryonic develop-
ment will vary with temperature and the species of fish. This method may
not be suitable on eggs of some warmwater species.
Gamete Storage
Sperm of rainbow trout and northern pike have been stored and transport-
ed successfully. The sperm, with penicillin added, is placed in dry, sterile
bottles and then sealed. The temperature is maintained at approximately
32°F in a thermos containing finely crushed ice. Undiluted brook trout
sperm has been stored with some success for as long as 5 days. The sperm
should be taken under sterile conditions, kept free from all contaminants,
chilled immediately to 35°F, and refrigerated until needed. This procedure
also has been used to store rainbow trout sperm for a 7-day period. Some
workers, however, prefer to store brook trout milt for not more than 24
BROODSTOCK, SPAWNING, AND EGG HANDLING 169
hours at 34°F and to warm the stored milt to the ambient water tempera-
ture before fertilization.
Cryopreservation (freezing) of sperm from several warm- and coldwater
species has been successful for varying length of times and rates of fertility.
These procedures generally require liquid nitrogen and extending agents,
and are reviewed by Horton and Ott (1976).
At 46° to 48°F, sockeye salmon eggs with no water added maintained
their fertility for 12 hours after being stripped, and a few were still fertile
after 175 hours. Sockeye milt maintained its fertility for 11 hours and fertil-
ized a few eggs after 101 hours. Pink salmon eggs have maintained their
fertility for 8 hours, and some were still fertile at 129 hours. Milt of pink
salmon maintained its fertility for 33 hours after being stripped from the
male, and fertilized 65"i of the eggs after 57 hours; none were fertilized
after 81 hours. Some fish culturists have obtained 90"(i fertilization with
pink salmon eggs and sperm stored for periods up to 20 hours at 43°F.
Storage of chum salmon eggs for 108 hours at temperatures of 36° to 42°F
maintained an 80"() fertility when fertilized with fresh sperm. Chum salmon
sperm stored under similar conditions for 36 hours maintained a 90% fertil-
ity when applied to fresh eggs.
Experiments with fall chinook salmon eggs and sperm have shown that
the eggs are more sensitive to storage time and temperature than sperm.
After 48 hours storage at 33°F, egg mortality was approximately 47%. Mor-
tality was 100"o after 48 hours storage at 56°F. Forty-eight-hour storage of
sperm at 56°F resulted in about a 12"n mortality. The stored eggs were fer-
tilized with freshly collected sperm and the stored sperm was used to fertil-
ize freshly spawned eggs.
Anesthetics
Anesthetics relax fish and allow increased speed and handling ease during
the spawning operation. In general, the concentration of the anesthetic
used must be determined on a trial and error basis with the particular
species of fish being spawned, because such factors as temperature and
chemical composition of the water are involved. Fish may react differently
to the same anesthetic when exposed to it in a different water supply. Be-
fore any anesthetic is used, it is advisable to test it with several fish.
At least 15 anesthetic agents have been used by fish culturists. Of the
anesthetics reported, quinaldine (2-methylquinoline), tricaine methane sul-
fonate (MS-222), and benzocaine are the most popular fish anesthetics
currently in use. Only MS-222 has been properly registered for such use.
There are various stages of anesthesia in fish (See Chapter 6, Table 39).
When placed in the anesthetic solution, the fish often swim about for
several seconds, attempting to remain in an upright position. As they lose
170 FISH HATCHERY MANAGEMENT
equilibrium they become inactive. Opercular movement decreases. When
the fish can no longer make swimming movements, the respiration becomes
quite rapid, and opercular movements are difficult to detect. At this point,
the fish may be removed from the water and spawned. If gasping and mus-
cular spasms develop while a fish is being spawned, it should be returned
to fresh water immediately. If the fish has been overexposed to the drug,
respiratory movements will cease. Rainbow trout placed in a 264 parts per
million solution of MS-222 require 30 to 45 seconds to become relaxed.
Concentrations of 0.23 gram of benzocaine per gallon of water or 0.45
gram of MS-222 per gallon of water are commonly used to anesthetized
fingerling Pacific salmon.
Use of MS-222 as an anesthetic for spawning operations is widespread.
However, concentrations as low as 18.9 parts per million have reduced
sperm motility. Therefore, the anesthetizing solution should not come in
contact with the reproductive products. Adult Pacific salmon have been
anesthesized with a mixture of 40 parts per million MS-222 and 10 parts
per million quinaldine. Carbon dioxide at concentrations of 200-400 parts
per million, is used in some instances for calming adult Pacific salmon. It
can be dispersed into the tank from a pressurized cylinder through a car-
borundum stone.
Both ether and urethane have been used in the past, but both should be
discontinued due to the high flammability of ether and the possible carci-
nogenic properties of urethane.
Artificial Control of Spawning Time
Management requirements and availability of hatchery facilities often make
it desirable to spawn fish at times different from the natural spawning date.
Several methods have been used with success.
PHOTOPERIOD
Controlled light periods have been used with several species of fish to
manipulate spawning time. The Fish and Wildlife Service's Salmon Cultur-
al Laboratory, Entiat, Washington, conducted a 3-year study to determine
the effect of light control on sockeye salmon spawning. The study showed
that salmon exposed to shortened periods of light spawn appreciably ear-
lier. Egg mortalities can be significantly higher, however. Light, not tem-
perature, is apparently the prime factor in accelerating or retarding sexual
maturation in this species; although temperatures varied from year to year,
salmon receiving no light control spawned at essentially the same time
each year.
BROODSTOCK, SPAWNING, AND EGG HANDLING 171
Artificial light has been used successfully to induce early spawning in
brook, brown, and rainbow trout. The rearing facilities are enclosed and
lightproof, and all light is provided by overhead flood lamps. Broodstock
should have had at least one previous spawning season before being used
in a light-controlled spawning program. Eggs produced generally are small-
er and fewer eggs are produced per female. The following light schedule is
used to induce early spawning in trout. An additional hour of light is pro-
vided each week until the fish are exposed to nine hours of artificial light
in excess of the normal light period. The light is maintained at this
schedule for a period of four weeks and then decreased one hour per week
until the fish are receiving four hours less light than is normal for that
period. By this schedule, the spawning period can be advanced several
months. Use of broodfish a second consecutive year under light-controlled
conditions does not always prove satisfactory, and a controlled-light
schedule must be started at least six months prior to the anticipated
spawning date.
Most attempts at modifying the spawning date of fish have been to
accelerate rather than retard the maturation process. However, spawning
activity of eastern brook trout and sockeye salmon have been delayed by
extending artificial light periods longer than normal ones. Temperature
and light control are factors in manipulating spawning time of channel cat-
fish. Reducing the light cycle to 8 hours per day and lowering the water
temperature by I4°F will delay spawning for approximately 60-150 days.
The spawning period of largemouth bass has been greatly extended by
the manipulation of water temperature. For example, moving fish from 67°
to 61°F water will result in a delayed spawning time.
HORMONE INJECTION
Spawning of warmwater and coolwater species can be induced by hormone
injection. This method has not proven to be as successful with coldwater
species. Fish must be fairly close to spawning to have any effect, as the
hormones generally bring about the early release of mature sex products
rather than the promotion of their development. Both pituitary material ex-
tracted from fish and human chorionic gonadotropin have been used suc-
cessfully.
Use of hormones may produce disappointing results if broodfish are not
of high quality. Under such conditions, a partial spawn, or no spawn at all,
may result. It also appears that some strains of fish do not respond to hor-
mone treatment in a predictable way, even when they are in good spawn-
ing condition.
Injection of salmon pituitary extract into adult salmon hastens the de-
velopment of spawning coloration and other secondary sex characteristics,
172
FISH HATCHERY MANAGEMENT
ripens males as early as three days after injection, and advances slightly the
spawning period for females, but may lower the fertility of the eggs. Injec-
tion of mammalian gonadotropin into adult salmon fails to hasten the
development of spawning characteristics, and there is no change in the
time of maturation.
Acetone-dried fish pituitaries from common carp, buffalo, flathead cat-
fish, and channel catfish have been tested and all will induce spawning
when injected into channel catfish (Figure 58). Carp pituitary material also
induces ovulation in walleye. The pituitary material is finely ground,
suspended in clean water or saline solution, and injected intraperitoneally
at a rate of two milligrams of pituitary per pound of broodfish (Figure 59).
One treatment is given each day until the fish spawns or shows resistance
to the hormone. Generally the treatment should be successful by the third
or fourth day.
Goldfish have been injected with human chorionic gonadotropin (HCG)
in doses ranging from 10 to 1,600 International Units (lU) but only those
females receiving 100 lU or more have ovulated. One hundred lU of HCG
is comparable to 0.5 milligram of acetone-dried fish pituitary. In some in-
stances goldfish will respond to two injections of HCG as low as 25 lU,
when given 6 days apart. White crappies injected with 1,000, 1,500, and
Figure 58. Collection of pituitary gland (arrow) from a common carp head. The
top of the head has been removed to expose the brain. (Fish Farming Experi-
mental Station, Stuttgart, Arkansas.)
BROODSTOCK, SPAWNING, AND EGG HANDLING 173
Figure 59. Injection of hormone intraperitoneally into female channel catfish.
(Fish Farming Experimental Station, Stuttgart, Arkansas.)
2,000 lU spawned three days after they were injected. Female crappies in-
jected with 1,000 lU spawned 2 days later at a water temperature of 62°F.
Channel catfish, striped bass, common carp, white crappies, and large-
mouth bass, injected with 1,000 to 2,000 lU of HCG, also have been in-
duced to spawn.
Hormone injection of striped bass has proven to be effective for spawn-
ing this species in rearing tanks. Females given single intramuscular injec-
tions at the posterior base of the dorsal fin with 125 to 150 lU of HCG per
pound of broodfish show the best results. Multiple injections invariably
result in premature expulsion of the eggs. Injection of males is recommend-
ed for obtaining maximum milt production. Fifty to 75 lU per pound of
broodfish should be injected approximately 24 hours prior to the anticipat-
ed spawning of the female.
Channel catfish also can be successfully induced to spawn by intraperi-
toneal injections of HCG. One 800- lU injection of HCG per pound of
broodfish normally is sufficient. Two 70-IU injections of HCG per pound
of broodfish, spaced 72 hours apart, will induce ovulation in walleyes.
Egg Incubation and Handling
Eggs of commonly cultured species of fish are remarkably uniform in their
physiology and development. A basic understanding of the morphology
and physiological processes of a developing fish embryo can be of value to
174 FISH HATCHERY MANAGEMENT
the fish culturist in providing an optimum environment for egg develop-
ment.
Egg Development
During oogenesis, when an egg is being formed in the ovary, the egg's fu-
ture energy sources are protein and fat in the yolk material. At this early
stage, the egg is soft and low in water content, and may be quite adhesive.
The ovum, or germ cell, is enclosed in a soft shell secreted by the ovari-
an tissue. This shell, or chorion, encloses a fluid-filled area called the
perivitelline space. An opening (the micropyle) provides an entryway for
the sperm. Inside the perivitelline space is a vitelline membrane; the yolk
is retained within this membrane (Figure 60). Trout eggs are adhesive
when first spawned because of water passing through the porous shell. This
process is called water- hardening, and when it is complete, the egg no
longer is sticky. The egg becomes turgid with water, and the shell is
separated from the yolk membrane by the perivitelline space filled with
fluid. This allows the yolk and germinal disc to rotate freely inside the egg,
with the disc always being in an upright position.
The micropyle is open to permit entry of the sperm when the egg is first
spawned. As the egg water- hardens, the micropyle closes and there is no
MICROPYLE
VITELLINE
MEMBRANE
YOLK
GERMINAL DISC
SHELL
PERIVITELLINE
SPACE
OIL DROPLET
Figure 60. Diagrammatic section of a fertilized trout egg. (Source: Davis 1953.)
BROODSTOCK, SPAWNING, AND EGG HANDLING 175
further chance for fertiUzation. In salmonids, water- hardening generally
takes from 30 to 90 minutes, depending on water temperature.
The sperm consists of a head, midpiece, and tail, and is inactive when it
first leaves the fish; on contact with water or ovarian fluid, it becomes very
active. Several changes take place when the sperm penetrates the egg. Nu-
clear material of the egg and sperm unite to form the zygote. This zygote,
within a few hours, divides repeatedly and differentiates to form the em-
bryo.
Schematic drawings of trout and salmon egg development (Figure 6l)
can be applied in general to other species as well.
SENSITIVE STAGE
Trout and salmon eggs become progressively more fragile during a period
extending roughly from 48 hours after water- hardening until they are eyed.
An extremely critical period for salmonid eggs exists until the blastopore
stage is completed. The eggs must not be moved until this critical period
has passed. The eggs remain tender until the eyes are sufficiently pigment-
ed to be visible.
EYED STAGE
As the term implies, this is the stage between the time the eyes become
visible and hatching occurs. During the eyed stage, eggs usually are
shocked, cleaned, measured and counted, and shipped.
At hatching, the weight of the sac fry increases rapidly. Water content of
the fry increases until approximately 10 weeks after hatching, when it is
approximately 80"(i of the body weight. Water content remains fairly uni-
form in a fish from this point on.
As the embryo develops, there is a gradual decrease in the protein con-
tent of the egg. The fat content remains fairly uniform, but there is a gra-
dual decrease in relative weight of these materials as water content
increases. There is no significant difference in the chemistry of large and
small eggs. However, several studies have shown that larger eggs generally
produce larger fry and this size advantage continues throughout the growth
and development of the fish.
Enumeration and Sorting of Eggs
A number of systems for counting eggs are in general use. Enumeration
methods should be accurate, practical, and should not stress the eggs.
176 FISH HATCHERY MANAGEMENT
.GERMINAL DISC
A. ONE DAY AFTER FERTILIZATION, 55.9°F AVERAGE TEMPERATURE
(23.9 T.U.).
BLASTODISC
B. TWO DAYS AFTER FERTILIZATION, 53.9°F AVERAGE TEMPERATURE
(43.9 T.U.).
EDGE OF BLASTODISC
EMBRYO
C. FIVE DAYS AFTER FERTILIZATION, 51 .7°F AVERAGE TEMPERATURE
(98.4 T.U.).
Figure 61. Schematic development of trout and salmon eggs. One temperature
unit (TU) equals 1°F above 32°F for a 24-hour period. See Glossary: Daily Tem-
perature Unit. (Source: Leitritz and Lewis 1976.)
When small numbers of eggs are involved, counting can be done by
hand or by the use of a counting board that will hold a known number of
eggs. A paddle- type egg counter is constructed of plexiglass by drilling and
countersinking a desired number of holes spaced in rows. The diameter of
the hole will depend on the size of eggs being counted. The paddle is
BROODSTOCK, SPAWNING, AND EGG HANDLING 177
THICKENED EDGE OF BLASTODERM
EMBRYO
D. SIX DAYS AFTER FERTILIZATION, 51.5°F AVERAGE TEMPERATURE
(117.0 T.U.).
EDGE OF BLASTODERM
EMBRYO
E. SEVEN DAYS AFTER FERTILIZATION, 51.2°F AVERAGE TEMPERATURE
(134.4 T.U.).
LIP OF BLASTOPORE
F. EIGHT DAYS AFTER FERTILIZATION, 51.7°F AVERAGE TEMPERATURE
(157.5 T.U.).
Figure 61. Continued.
178 FISH HATCHERY MANAGEMENT
SOMITE
G. NINE DAYS AFTER FERTILIZATION, 51.4°F AVERAGE TEMPERATURE
(174.5 T.U.).
FUTURE OPTIC LOBE
HIND BRAIN
H. TEN DAYS AFTER FERTILIZATION, 51,5°F AVERAGE TEMPERATURE
(195,4 T.U.).
OLFACTORY CAPSULE
FUTURE OPTIC LOBE
HIND BRAIN
I. ELEVEN DAYS AFTER FERTILIZATION, 51, 7T AVERAGE TEMPERATURE
(216,6 T,U,).
Figure 61. Continued.
BROODSTOCK, SPAWNING, AND EGG HANDLING 179
OPTIC LOBE
OTIC CAPSULE
FUTURE PECTORAL FIN
J, THIRTEEN DAYS AFTER FERTILIZATION, 51. 7T AVERAGE TEMPERATURE
(225.8 T.U.)
.MYOMERE
NOTOCHORD
-VENT
K. FOURTEEN DAYS AFTER FERTILIZATION, 51.5°F AVERAGE TEMPERATURE
(273.2 T.U.).
FUTURE CAUDAL FIN
ANAL FIN FOLD
ORSAL FIN FOLD
MYOMERE
FUTURE ANAL FIN
L. SIXTEEN DAYS AFTER FERTILIZATION, 51. 7T AVERAGE TEMPERATURE
(315.9 T.U.).
Figure 61. Continued.
180
FISH HATCHERY MANAGEMENT
HIRD VENTRICLE
QPTIC LOBE
ENS OF EYE
DOE OF MANDIBLE
IND BRAIN
OTIC CAPSULE
,GILL BAR
FUTURE PECTORAL FIN
HEAD-VENTRA
M. SIXTEEN DAYS AFTER
FERTILIZATION, 51. 7T
AVERAGE TEMPERATURE
(315.9 T.U.).
N. EIGHTEEN DAYS AFTER
FERTILIZATION, 51.8°F
AVERAGE TEMPERATURE
(357.4 T.U.).
ORSAL FIN
CEREBRAL HEMISPHERE,
OPTIC LOBE
HIND BRAIN
FUTURE
FOURTH VENTRICLE
FUTURE CEREBELLUM,
ORSAL FIN FOLD
NAL FIN
NAL FIN FOLD
VENTRAL FIN
0. TWENTY-SIX DAYS AFTER
FERTILIZATION, 51. 2T
AVERAGE TEMPERATURE
(500.4 T.U.).
Figure 61. Continued.
dipped into the egg mass and eggs fill the holes as the paddle is lifted
through them.
Three commonly used procedures for counting trout and salmon eggs are
the Von Bayer, weight, and water-displacement methods.
The Von Bayer method employs a 12- inch, V-shaped trough (Figure 62).
BROODSTOCK, SPAWNING, AND EGG HANDLING
181
NUMBER OF EGGS
12 INCH TROUGH
NUMBER OF EGGS
PER OUNCE
Figure 62. Diagrammatic plan view of a Von Bayer V-trough for estimating
numbers and volumes of eggs.
182 FISH HATCHERY MANAGEMENT
A sample of eggs is placed in a single row in the trough until they fill its
length. The number of eggs per 12 inches is referred to Table 18, which
converts this to number of eggs per liquid ounce or quart. All eggs then
are placed in a water-filled, 32-ounce (quart) graduated cylinder, the sub-
merged eggs being leveled to the 32-ounce mark. The total number of eggs
is the number per quart (or ounce) x the number of quarts (or ounces).
The weight method is based on the average weight of eggs in a lot.
Several 100-egg samples are drained and weighed to the nearest 0.1 gram.
The average egg weight then is calculated. The entire lot of eggs is drained
in preweighed baskets and weighed on a balance sensitive to 1 gram. Divi-
sion of the total weight of the eggs by the average weight of one egg deter-
mines the number of eggs in a lot. There are two sources of error in the
weight method; variation in the amount of water retained on the eggs in
the total lot and variation in sample weights due to water retention. Differ-
ences in surface tension prevent consistent removal of water from the eggs.
Blotting pads of folded cloth or paper toweling should be used to remove
the excess water from the eggs.
In the displacement method, water displaced by the eggs is used to meas-
ure the egg volume. This provides an easily read water level rather than an
uneven egg level when volume is determined. Small quantities of eggs can
be measured in a standard 32-ounce graduated cylinder. For larger quanti-
ties, a container with a sight gauge for reading water levels is most con-
venient. A standard 25-milliliter burette calibrated in tenths of milliliters
makes an excellent sight gauge. A table, converting gauge readings to fluid
ounces, is prepared by adding known volumes of water to the container
and recording the gauge readings. The eggs are drained at least 30
seconds in a frame net, and the underside of the net is wiped gently with a
sponge or cloth to remove excess water. The total volume of eggs then is
measured by changes in gauge readings (converted to volume) when eggs
are added to the container. The amount of water initially placed in the
container should be sufficient to provide a clearly defined water level
above the eggs. The volume of water displaced by a known number of eggs
is then determined by sample-counting; the more numerous and represen-
tative the samples, the more accurate the total egg count will be. One or
more random samples should be prepared for each volume measurement
and a minimum of five samples for the total lot of eggs. For sampling,
count out 50 eggs into a burette containing exactly 25 milliliters of water.
Determine the exact number of milliliters of water displaced. The number
of eggs per fluid ounce can then be determined from Table 19.
The accuracy of these three methods has been compared, and only the
Von Bayer technique showed a significant difference from actual egg
counts, with the displacement method being the most accurate. However,
the weight technique is so much faster and efficient that it is considered
broodstock, spawning, and egg handling 183
Table 18. modified von baver table for the estimation of the numbers of
fish eggs in a liquid quart.
NO. OF EGGS
DIAMETER OF EGGS
NO. OF EGGS PER
NO. OF EGGS PER
PER 12 TROUGH
(INCHES)
LIQUID QUART
LIQUID OUNCE
35
0.343
1,677
52
36
0.333
1,833
57
37
0.324
1,990
62
38
0.316
2,145
67
39
0.308
2,316
72
40
0.300
2,606
78
41
0.292
2,690
84
42
0.286
2,893
90
43
0.279
3,116
97
44
0.273
3,326
104
45
0.267
3,556
111
46
0.261
3,806
119
47
0.255
4,081
128
48
0.250
4,331
135
49
0.245
4,603
144
50
0.240
4,895
153
51
0.235
5,214
163
52
0.231
5,490
172
53
0.226
5,862
185
54
0.222
6,185
193
55
0.218
6,531
204
56
0.214
6,905
216
57
0.211
7,204
225
58
0.207
7,630
238
59
0.203
8,089
253
60
0.200
8,459
264
61
0.197
8,851
277
62
0.194
9,268
290
63
0.191
9,712
304
64
0.188
10,184
318
65
0.185
10,638
334
66
0.182
11,225
351
67
0.179
11,799
359
68
0.177
12,203
381
69
0.174
12,348
401
70
0.171
13,533
423
71
0.169
14,020
438
72
0.167
14,529
454
73
0.164
15,341
479
74
0.162
15,916
497
75
0.160
16,621
516
76
0.158
17,157
536
77
0.156
17,825
557
78
0.154
18,528
579
79
0.152
19,270
602
184
FISH HATCHERY MANAGEMENT
Table 19. mh.lii, iters of water displaced by m eggs converted to number
OF eggs per fluid ounce.
MILLI-
NUMBER
MILLI-
NUMBER
MILI.I-
NUMBER
LITERS
PER
LITERS
PER
LHERS
PER
DISPLACED
OUNCE
DISPLACED
OUNCE
DISPLACED
OUNCE
3.0
492.88
7.1
208.25
11.2
132.00
3.1
477.00
7.2
205.35
11.3
130.89
3.2
462.10
7.3
202.55
11.4
129.70
3.3
448.10
7.4
199.80
11.5
128.60
3.4
434.90
7.5
197.15
11.6
127.45
3.5
422.45
7.6
194.55
11.7
126.40
3.6
410.75
7.7
192.05
11.8
125.30
3.7
399.65
7.8
189.55
11.9
124.25
3.8
389.10
7.9
187.15
12.0
123.20
3.9
379.15
8.0
184.83
12.1
122.20
4.0
369.65
8.1
182.55
12.2
121.20
4.1
360.65
8.2
180.30
12.3
120.20
4.2
352.05
8.3
178.15
12.4
119.25
4.3
343.85
8.4
176.05
12.5
118.30
4.4
336.05
8.5
173.95
12.6
117.35
4.5
328.60
8.6
171.95
12.7
116.45
4.6
321.45
8.7
169.95
12.8
115.50
4.7
314.60
8.8
168.05
12.9
114.60
4.8
308.05
8.9
166.15
13.0
113.75
4.9
301.75
9.0
164.30
13.1
112.85
5.0
295.75
9.1
162. .50
13.2
112.00
5.1
289.95
9.2
160.70
13.3
111.20
5.2
284.35
9.3
159.00
13.4
110.35
5.3
279.00
9.4
157.30
13.5
109.55
5.4
273.80
9.5
155.65
13.6
108.70
5.5
268.85
9.6
154.05
13.7
107.95
5.6
264.05
9.7
152.45
13.8
107.15
5.7
259.40
9.8
150.90
13.9
106.40
5.8
254.95
9.9
149.35
14.0
105.60
5.9
250.60
10.0
147.85
14.1
104.85
6.0
246.45
10.1
146.40
14.2
104.15
6.1
242.40
10.2
144.95
14.3
103.40
6.2
238..50
10.3
143.55
14.4
102.70
6.3
234.70
10.4
142.15
14.5
102.00
6.4
231.05
10.5
140.80
14.6
101.30
6.5
227. ,50
10.6
139.. 50
14.7
100.60
6.6
224.05
10.7
138.20
14.8
99.90
6.7
220.70
10.8
136.90
14.9
99.25
6.8
217.45
10.9
135.65
15.0
98.60
6.9
214.30
11.0
134.40
7.0
211.25
11.1
133.20
BROODSTOCK, SPAWNING, AND EGG HANDLING 185
the best of the methods evaluated. The displacement method takes twice
the time required by either of the other methods. The weight method is
recommended when large lots of eggs must be enumerated, while the dis-
placement method is more desirable with small lots of eggs.
Another method of egg inventory, which differs from other volumetric
methods basically in egg measuring technique, sometimes is used by fish
culturists. Eggs are measured in a container, such as a cup or strainer filled
to the top, and an equal number of containerfuls of eggs are put in each
egg incubator tray or jar. Sample counting consists of counting all the eggs
held in one measuring container. To get accurate egg inventories, the same
measuring unit must be used for the sample counts as for measuring the
eggs into the incubator. Measurement by filling the container to the top
eliminates errors in judgment. This method gives a good estimate of the
total number of eggs, but does not estimate the number of eggs per fluid
ounce.
Several methods have been used for the estimating number of striped
bass eggs. Estimates can be made by weighing the eggs from each female
and calculating the number of eggs on the basis of 25,000 per ounce. The
eggs can also be estimated volumetrically on the basis of Von Bayer's table.
Largemouth bass and catfish eggs are measured by weight or volumetric
displacement.
Various mechanical egg counting devices have been developed that use
photoelectric counters (Figure 63). The eggs are counted as they pass a
light source. Velocities producing count rates of up to 1,400 eggs per
minute have proven to be accurate. Air bubbles, dirt, and other matter will
interfere with accurate counting and must be avoided.
Salmonid eggs should be physically shocked before egg picking (removal
of dead eggs) commences, after the eggs have developed to the eyed stage.
Undeveloped or infertile eggs remain tender and they will rupture when
shocked. Water enters the egg and coagulates the yolk, turning the egg
white; these eggs then are readily picked out. Shocking may be done by
striking the trays sharply, siphoning the eggs from one container to
another, or by pouring the eggs from the incubator trays into a tub of
water from a height of 2 or 3 feet. Care should be taken to make sure that
the eggs are not shocked too severely or normally developing eggs also may
be damaged. (Figure 64).
Numerous methods for removing dead eggs have been in use in fish cul-
ture for many years. Before the introduction of satisfactory chemical fungi-
cides, it was necessary to frequently remove (pick) all dead eggs to avoid
the spread of fungus. In some instances where exposure to chemical treat-
ments is undesirable, it still is necessary to pick the dead eggs.
One of the earliest and most common methods of egg picking was with a
large pair of tweezers made either of metal or wood. If only small numbers
of eggs are picked, forceps or tweezers work very well. Another device in
186 FISH HATCHERY MANAGEMENT
Figure 63. A mechanical egg counter used with salmon eggs. (FWS
photo.)
Figure 64. Salmon eggs being shocked. (FWS photo.)
BROODSTOCK, SPAWNING, AND EGG HANDLING 187
use is a rubber bulb fitted to a short length of glass tubing. The diameter
of the tubing is large enough to allow single eggs to pass through it and
dead eggs are removed by sucking them up into the tube. A more ela-
borate egg picker can be constructed of glass and rubber tubing and dead
eggs are siphoned off into an attached glass jar (Figure 65).
A flotation method of separating dead from live eggs still is used in
many hatcheries, and particularly in salmon hatcheries. Eggs are placed in
a container of salt or sugar solution of the proper specific gravity, so that
live eggs will sink and dead eggs will float because of their lower density.
A sugar solution is more efficient than salt because the flotation period is
longer. The container is filled with water, and common table salt or sugar
is added until the dead eggs float and live eggs slowly sink to the bottom.
The optimum concentration of the solution may vary with the size and
developmental stages of the eggs. Floating dead eggs are then skimmed off
with a net. Best results are obtained if the eggs are well eyed because the
more developed the embryo, the more readily the eggs will settle.
Several electronic egg sorters are commercially available that separate
the opaque or dead eggs from the live ones. Manufacturers of these
machines claim a sorting rate of 100,000 eggs per hour. Another commer-
cial sorter works on the principle that live eggs have a greater resiliency
and will bounce (whereas dead eggs will not) and drop into a collecting
tray. This sorter has no electrical or moving parts.
Enumeration and transfer of fry are important facets of warmwater fish
culture, because the eggs cannot be counted in many instances. The fry of
many species, such as largemouth bass, smallmouth bass, and catfish, are
spawned naturally in ponds, and then transferred to a rearing pond. To as-
sure the proper stocking density, fry must be counted or their numbers es-
timated accurately. Many methods are used, and vary in complexity and
style.
The simplest, but least accurate, is the comparison method. A sample of
fry are counted into a pan or other similar container. The remaining fry are
then distributed into identical containers until they appear to have the
same density of fry as the sample container. The sample count is then used
to estimate the total number of fry in all the containers. Other methods in-
volve the determination of weight or volume of counted samples and then
estimating the number of fry from the total weight or volume of the group.
The most accurate methods require greater handling of the fry but, when
they are small, handling should be kept to a minimum to reduce mortality.
In catfish culture, a combination of methods is used. The number of
eggs can be estimated by weight or from records on the parent fish. The
gelatinous matrix in which catfish eggs are spawned makes the volumetric
method of egg counting impractical. There are approximately 3,000 to
5,000 catfish eggs per pound of matrix, and the number of eggs can be
estimated from the weight of the mass of eggs. After the eggs hatch, fry are
188
FISH HATCHERY MANAGEMENT
SELF-SEALING MASON FRUIT JAR
1/4" COPPER TUBE
-♦-DOUBLE-ENDED RUBBER BULB
GLASS TUBE-
1/4" COPPER TUBE
SMALL NOTCH
Figure 65. Construction of a siphon egg picker. (Source:
Davis 1953.)
BROODSTOCK, SPAWNING, AND EGG HANDLING 189
enumerated volumetrically if they are to be moved immediately to rearing
ponds. If they are held in rearing tanks or troughs until they accept formu-
lated feed, their numbers are estimated from weighed and counted samples.
Egg Disinfection
Eggs received from other hatcheries should be disinfected to prevent the
spread of disease. Disinfection should be carried out in separate facilities in
order to prevent contamination of the hatchery by eggs, water, trays, and
packing material from the shipping crate.
The iodophor Betadine, can be used to disinfect most fish eggs. Eggs are
treated at 100 parts per million active ingredient (iodine) for 10 minutes. A
100 parts per million iodine concentration is obtained by adding 2.6 fluid
ounces of 0.5X Betadine per gallon of water. Betadine also is available in a
1% iodine solution. In soft water below 35 parts per million alkalinity, pH
reduction can occur, causing high egg mortality. Sodium bicarbonate may
be added as a buffer at 3.7 grams per gallon if soft water is encountered.
Should a precipitate be formed from the sodium bicarbonate it will not
harm the eggs. The eggs should be well rinsed after treatment. An active
iodine solution is dark brown in color. A change to a lighter color indicates
an inactive solution and a new solution should be used. Do not treat eggs
within 5 days of hatching as premature hatching may result, with increased
mortality. Tests should be conducted on a few eggs before Betadine is considered
safe for general use as an egg disinfectant.
Largemouth bass eggs can be treated with acriflavine at 500 to 700 parts
per million or Betadine at 100 to 150 parts per million for 15 minutes.
Roccal and formalin are not effective disinfectants at concentrations that
are not injurious to fish eggs.
Incubation Period
Several methods have been devised for determining the incubation period
of eggs. One method utilizes temperature units. One Daily Temperature
Unit (DTU) equals 1° Fahrenheit above freezing (32°F) for a 24-hour
period. For example, if the water temperature for the first day of incuba-
tion is 56°F, it would contribute 24 DTU (56°-32°). Temperature units
required for a given species of fish are not fixed. They will vary with dif-
ferent water temperatures and are affected by fluctuating temperatures.
However, DTU can be used as a guide to estimate the hatching date of a
190
FISH HATCHERY MANAGEMENT
Table 20. number of days and daily lEMi'ERAruRE units required for
TROUT EGGS TO HATCH". (SOURCE: LEITRITZ AND LEWIS l<)7(i.)
WATER TEMPERATURE, T
SPECIES
35
40
45
50
55
60
Rainbow trout
Number of days to hatch
Daily temperature units
Brown trout
Number of days to hatch
Daily temperature units
Brook trout
Number of days to hatch
Daily temperature units
Lake trout
Number of days to hatch
Daily temperature units
—
80
48
31
24
19
—
640
624
558
552
532
156
100
64
41
468
800
832
738
—
—
144
103
68
44
35
_
432
824
884
799
805
—
162
108
72
49
486
864
936
882
Spaces without figures indicate incomplete data rather than a proven inability of eggs to
hatch at those temperatures.
group of eggs at a specific temperature. The required temperature units to
hatch several species of fish are presented in Tables 20 through 23.
Factors Affecting Egg Development
Three major factors that affect the development of the embryos are light,
temperature, and oxygen.
LIGHT
Direct light may have an adverse effect on developing fish eggs. The most
detrimental rays are those in the visible violet-blue range produced by cool
white fluorescent tubes. Pink fluorescent tubes, which emit light in the yel-
low to red range, are best suited for hatchery use. The best practice is to
keep eggs covered and away from direct light.
In general, embryos of fishes subjected to bright artificial light before
the formation of eye pigments will suffer high mortality at all stages of
growth. Affected eggs exhibit retarded development and accelerated hatch
and, if they do hatch, the fingerlings often have reduced growth and severe
liver damage. Eggs exposed to artificial light after formation of eye pig-
ments are less susceptible to light rays but still exhibit increased mortality
and reduced growth, or both.
BROODSTOCK, SPAWNING, AND EGG HANDLING
191
Table 21. daily temperature unit REquiRED for egg development of
Pacific salmon.
DAILY TEMPERATURE UNITS
SPECIES
TO EYE
TO HATCH
TO EMERGE
Chinook salmon
Coho salmon
Chum salmon
Pink salmon
Sockeye salmon
450
450
750
750
900
750
750
1,100
900
1,200
1,600
1,750
1,450
1,450
1,800
TEMPERA ri' RE
Chinook salmon eggs have been incubated at temperatures as high as 6\°F
without significant loss. When incubated at 4()°F and below, they have a
much higher mortality than those incubated at temperatures of 57 to (iO°F.
However, if chinook salmon eggs are allowed to develop to the 128-cell
stage in 42°F water, they can tolerate 35°F water for the remainder of the
incubation period. Lower temperatures have been experienced by sockeye
and chinook in natural spawning environments with fluctuating tempera-
tures without adverse affects. The lower threshold temperature for normal
development of sockeye salmon is between 40 and 42°F, with an upper
threshold temperature between 55 and 57°F. Water temperature appears to
be a primary factor in causing yolk-sac constriction in landlocked Atlantic
salmon fry. It apparently is triggered by both constant temperature or an
excessively warm temperature. Fry raised in cold water with fluctuating
temperature do not develop the constriction unless they are moved into a
warmer constant temperature.
Table 22. required daily temperature units for initial development of
VARIOUS COOL- and WARMWATER SPECIES.
incubation stage
HATCH TO
ACTIVE SWIMMING
EGG TAKE
.ACTIVE
TO START OF
SPECIES
to HATCH
SWIMMING
FEEDING
TOTAL
Channel catfish
350
50
100
500
Largemouth bass
140
90
80
310
Smallmouth bass
130
100
80
310
Hybrid sunfish
75
90
100
265
Bluegill
75
100
100
275
Redear sunfish
100
100
100
300
Northern pike
180
50
100
330
Muskellunge
235
260
100
595
Walleye
300
20
20
340
Striped bass
100
90
130
320
192 fish hatchery management
Table 23. time-temperature relationship and daily temperature units
req^uired for hatching muskellunge eggs,
DAILY TEMPERATURE UNITS
TEMPERAI'URE °F DAYS TO HATCH TO HATCH (F)
45 21 273
47 20 300
49 19 323
51 18 342
53 16 336
55 14 322
57 12 300
59 10 270
61 9 261
63 8 248
65 7 231
67 6 210
Eggs and fry of walleye tolerate rapid temperature fluctuations. Approx-
imately 390 daily temperature units are required for eggs to hatch in fluc-
tuating water temperatures, while only 230 daily temperature units general-
ly are required at more constant temperatures (see Table 22).
Low water temperatures during spawning and incubation of largemouth
bass eggs can cause high egg losses. Chilling of the eggs does not appear to
be the direct cause of egg loss. Rather, it causes the male fish, which nor-
mally guards and fans the eggs, to desert the nest. As a result, the eggs are
left without aeration and die from suffocation. This is a common cause of
egg losses in areas that are marginal for largemouth bass production.
Data gathered at the Weldon Striped Bass Hatchery, Weldon, North
Carolina, indicate that the optimum spawning temperature range for
striped bass is between 62 and 67°F. The minimum recorded temperature
at which spawning will occur is 55°F and the maximum temperature is
yiT.
OXYGEN
Sac fry from eggs incubated at low oxygen concentrations are smaller and
weaker than those from eggs incubated at higher concentrations. The best
conditions for the optimal development of embryos and fry are at or near
100% oxygen saturation. As the development of an egg progresses, oxygen
availability becomes increasingly important. Circulation of water is vital for
transporting oxygen to the surface of the chorion and for removing meta-
bolites from the vicinity of the developing egg. Eggs provided with insuffi-
cient oxygen will develop abnormalities and their hatching may be either
delayed or premature, depending on the species.
BROODSTOCK, SPAWNING, AND EGG HANDLING 193
Transportation of Eggs
Eggs can be shipped at four developmental stages: as immature eggs in the
living female; as mature unfertilized eggs; as recently fertilized and water-
hardened eggs; and as eyed eggs.
Live females may be shipped, but this method requires more extensive
transportation facilities than is required to ship eggs. Transportation of live
fish is covered in Chapter 6.
The shipping of mature unfertilized eggs requires some precautions.
Sperm should be shipped separately in sealed plastic bags with an air space
in the sperm container of at least 10 parts air to 1 part sperm. No air re-
quirements are necessary for eggs. Both eggs and sperm should be kept re-
frigerated. With these techniques, the fertility of Pacific salmon sperm and
eggs is not affected by storage for 4 hours at temperatures of 47-52°F be-
fore they are mixed. Eggs that are fertilized and then shipped under the
same conditions can suffer high losses. When newly spawned and fertilized
eggs are shipped the eggs must not be shaken in transit. Therefore, no air
space should be allowed in the container.
Eggs should not be shipped during the tender stage. They may be
shipped over long distances after the eyed stage is reached, if they are kept
cool and shipped in properly insulated boxes (Figure 66).
Types of Incubators
Many systems have been developed for incubating fish eggs. Basically, all
of them provide a fresh water supply with oxygen, dissipate metabolic
products, and protect the developing embryo from external influences
which may be detrimental.
HATCHING TRAYS
Hatching trays are perhaps the simplest type of incubation unit used.
They have been used successfully for many species of fish. The screened
hatching tray is sized to fit inside a rearing trough. The screening has rec-
tangular openings that will retain round eggs but permit newly hatched fry
to fall through. The wire mesh may be obtained in a variety of sizes and is
called triple warp mesh cloth. The triple warp cloth should have nine meshes
per inch for eggs that are 400 to 700 per ounce; seven meshes per inch for
eggs 240 to 390 per ounce; six meshes per inch for eggs 120 to 380 per
ounce; and five meshes per inch cloth for eggs that are 60 to 90 per ounce.
Eggs are placed on the tray no more than two layers deep, and the tray is
inclined and wedged at an angle of approximately 30 degrees, slanting to-
ward the incoming water in the trough. When all the eggs have hatched
194 FISH HATCHERY MANAGEMENT
Figure 66. Commercially available shipping boxes can be used to transport fish
eggs. The boxes should be constructed to keep the eggs moist and cool without
actually carrying them in water, (l) A wet cloth is placed in the shipping tray
and the eggs are carefully poured into the tray. (2) The tray should not be filled
to the point where the next succeeding tray will compress the eggs and put pres-
sure on them. The cloth is then carefully folded over the eggs and the next tray
put in place. (3) The top tray is filled with coarsely crushed ice or ice cubes to
provide cooling during shipping. The melting ice also will provide water to keep
the eggs moist. Ice should never be used directly from the freezer and should be
allowed to warm until it starts to melt before it is placed with the eggs. (4) The
insulated lid is put in place, and the box is sealed and properly labeled for
shipping. (FWS photos.)
and the fry have fallen through the mesh cloth, the trays are removed with
the dead eggs that remain on them. These units are relatively cheap and
easy to maintain, and egg picking is relatively simple. The disadvantages
are that rearing troughs must be available, there must be some means of
excluding light from the troughs while the eggs are being incubated, and
there is always a danger of improper water flow through the trays.
CLARK-WILLIAMSON TROUGH
The Clark- Williamson trough is a tray-hatching system for incubating
large numbers of eggs. The eggs are held on screen trays and are stacked
vertically rather than being placed horizontally in the trough. Dam boards
BROODSTOCK, SPAWNING, AND EGG HANDLING 195
are placed in slots in the trough to force the waterflow up through each
stack.
Many eggs can be handled in this type of unit, but it is difficult to ob-
serve egg development during incubation, and all trays in a stack must be
removed in order to examine the eggs on any individual tray. Possible air
locks within the stack can cause poor water circulation through the eggs.
CATFISH TROUGHS
Channel catfish eggs, which are deposited in a cohesive mass, require spe-
cial devices when they are moved to a hatching trough for artificial incuba-
tion. The large egg masses usually are broken up into smaller pieces to
enhance aeration and then placed in suspended baskets similar to the trays
described in the previous section.
When catfish eggs are hatched in troughs, they must be agitated by pad-
dles supported over the trough and driven by an electric motor or a water
wheel (Figure 67). The agitation must be sufficient to gently move the
whole egg mass. Paddles are constructed of galvanized tin or aluminum
and attached to a rotating shaft. The paddles are commonly 4 inches wide
and long enough to dip well below the bottom of the baskets as they turn.
The pitch of the paddles is adjusted as required to insure movement of
spawns in the baskets. The preferred speed is about 30 revolutions per
minute.
HATCHING BASKETS
Hatching baskets are quite similar to hatching trays, except that they are
approximately 6 to 12 inches deep and suspended in the trough to permit
a horizontal water flow. In many cases, deflector plates are installed ahead
of each basket in such a way as to force the flowing water up through the
baskets for better circulation. In the case of Pacific salmon, as many as
,50,000 eggs may be placed in a single basket.
HATCHING JARS
Hatching jars usually are placed in rows on racks with a manifold water
supply trough providing inlets to each jar and a waste trough to catch
overflow water (Figure 68). A simple unit can be fabricated from 2-inch
supply pipe with taps and an ordinary roof gutter as the waste trough. An
open tee usually is installed between the supply line and the pipe to the
bottom of the jar to aid in the elimination of gas bubbles during incuba-
tion of salmonid eggs, which must not be distrubed. The open tee may also
be used to introduce chemicals for treating eggs. The diameter of the tee
196 FISH HATCHERY MANAGEMENT
Figure 67. Channel catfish trough for egg incubation. Paddles (arrow) gently
circulate the water in the trough. (FWS photo.)
should be larger than the pipe entering the jar to prevent venturi action
from sucking air bubbles into the jar.
Hatching jars are designed to provide an upward flow of water intro-
duced at the bottom of the jar. When rolling of the eggs is desired, as in
the case of some coolwater species, the bottom of the jar is concave, with
the water introduced at the center. When used for incubating trout or sal-
mon eggs, the jar is modified with a screen-supported gravel bottom, and
the water is introduced underneath the gravel. This provides a uniform,
upward water flow, and the eggs are stationary. These systems also have
been used for striped bass and channel catfish egg incubation.
Some fry will swim out of the jar and into the waste trough if a cover
screen is not provided. Coolwater species are allowed to swim from the jars
and are collected in holding tanks.
MONTAN./>k HATCHING BOX
The Montana Hatching Box operates essentially like a hatching jar. The
box is constructed of waterproof plywood or fiberglass and is approxi-
mately 1 foot square by 2 feet high. A vertical water flow is provided by a
BROODSTOCK, SPAWNING, AND EGG HANDLING
197
manifold of pipes beneath a perforated aluminum plate in the bottom of
the box. A screened lip on the upper edge of the box provides an overflow
and retains the eggs or fry. The box commonly is used in bulk handling of
eggs to the eyed stage for shipping, but it can also be used to rear fry to
the feeding stage (Figure 69).
A problem with the hatching box is the tendency for gas bubbles to
build up below the perforated plate, shutting off the water flow to portions
of the box. As with other systems, it is good practice to aerate any water
supply used for this type of incubation.
VERTICAL-TRAY INCUBATORS
The vertical- tray incubator is widely used for developing salmonid eggs
(Figure 70). The eggs are allowed to hatch in the trays and fry remain
there until ready to feed. Water is introduced at one end of the top tray
and flows under the egg basket and up through the screen bottom, circulat-
ing through the eggs. Water, upwelling through the bottom screen helps
prevent smothering of hatched fry. The water then spills over into the tray
below, and is aerated as it falls.
Figure 68. Jar incubation of muskellunge eggs. (Courtesy Wisconsin Depart-
ment of Natural Resources.)
198 FISH HATCHERY MANAGEMENT
Figure 69. Trout eggs being poured into a Montana hatching box.
These incubators can be set up as either 8- or 16-tray units. Draining
and cleaning of each tray is possible without removing it from the incuba-
tor. Individual trays can be pulled out for examination without disturbing
other trays in the stack. Screen sizes can be varied to accommodate the
species of eggs being incubated. Accumulations of air bubbles can cause
problems in water circulation, and care should be taken to de-aerate super-
saturated water prior to use in this unit. Vertical incubators have several
advantages over troughs. They require small amounts of water to operate,
and use relatively little floor space. Fungus can be controlled easily with
chemicals due to the excellent flow pattern through the eggs. The small
quantities of water required for these incubators make it feasible to heat or
cool the water as required.
BROODSTOCK, SPAWNING, AND EGG HANDLING
199
SIMULATED NATURAL CONDITIONS AND REARING POND INCUBATION
Salmon and steelhead eggs have been incubated successfully between layers
of gravel, simulating natural spawning conditions. An incubation box that
has proved successful is made of 7-inch marine plywood, 8 feet long, 2 feet
wide, and 15 inches deep. Water, which is first filtered through crushed
rock, is supplied to the box by four 1-inch diameter aluminum conduit
pipes placed full length in the bottom of the box. Use of such a device for
anadromous fish permits the incubation of eggs in the stream system in
which the fish are to be released.
A similar type of system involves incubation channels. Incubation chan-
nels differ from previously discussed spawning channels in that eyed eggs
are placed in prepared trenches. Fish reared under these conditions are
generally hardier than those reared in the hatchery.
Plastic substrates can be added to incubation units (such as vertical
incubators) to simulate the environment provided by gravel. Plastic sub-
strate fabricated from artificial grass also has been used successfully in sal-
monid incubation systems to provide a more natural environment for newly
hatched fry and has resulted in larger and more hardy fish.
The state of Washington has developed a method for incubating salmon
eggs utilizing specially designed trays placed in raceways. These units are
Figure 70. Salmon eggs being measured into a vertical- tray incubator. A screen
lid is placed on top of the tray to prevent loss of eggs and hatched fry.
200 FISH HATCHERY MANAGEMENT
similar to hatchery trays but are much larger. The raceways are filled with
water, eggs are placed in the trays, and the hatched fry are allowed to exit
into rearing ponds at their own volition.
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4
Nutrition and Feeding
Nutrition
Nutrition encompasses the ingestion, digestion, and absorption of food.
The rearing of large numbers of animals in relatively restricted areas,
whether they be terrestrial or aquatic, requires a detailed knowledge of
their nutritional requirements in order that they can be provided a feed
adequate for their growth and health. There has not been the emphasis on
rearing cultured fish as a major human food source that there has been for
other livestock. Also, the quantity of fish feed required by hatcheries and
commercial fish farms has not been sufficient to justify feed companies or
others to spend more than a minimal amount of money for fish nutrition
research. As a result, an understanding of fish nutrition has advanced very
slowly.
Biologists first approached the problem of feeding cultured fish by inves-
tigating natural foods. Several species still must be supplied with natural
foods because they will not eat prepared feeds. However, as large numbers
of fish were propagated and more and more fish culture stations estab-
lished, it became uneconomical or impractical to use natural feeds. Because
of the limited supply and uncertain nature of artificially cultured natural
food organisms, fish culturists turned to more readily available and reliable
food supplies. Glandular parts of slaughtered animals were among the first
ingredients used to supplement or replace natural feeds.
208
NUTRITION AND FEEDING 209
Hatchery operators also started feeding vegetable feedstuffs separately or
combined with meat products to provide greater quantities of finished feed.
One of the major problems was how to bind the mixtures so they would
hold together when placed in the water. In the early days of fish culture, a
large portion of artificial feed was leached into the water and lost. This
resulted in poor growth, increased mortality, water pollution, and increased
labor in cleaning ponds and raceways. The use of dry meals in the diet to
reduce feed costs compounded the problem of binding feeds to prevent
loss. The use of certain meat products such as spleen and liver mixed with
salt resulted in rubber-like mixtures, called meat-meal feeds, that were
suitable for trough and pond feeding. These were mixed in a cement or
bread mixer and extruded through a meat grinder. This type of feed pro-
duced more efficient food utilization, better growth, and a reduction in the
loss of feeds.
However, considerable labor was involved in the preparation of the
meat-meal feeds. In addition, the use of fresh meat in the diet required ei-
ther frequent shipments or cold storage. The ideal hatchery feed was one
that would combine the advantages of the meat-meal feed, but would elim-
inate the labor involved in preparation and reduce the expense of cold
storage facilities.
In 1959, the Oregon State Game and Fish Commission began to use a
pelleted meat-meal fish feed called Oregon moist pellet (OMP), now com-
mercially manufactured. .These pellets were developed because salmon
would not take dry feed. Use of this feed in production was preceded by
six years of research. The formula is composed of wet fish products and
dry ingredients; it has a moist, soft consistency and must be stored frozen
until shortly before feeding.
Many hatcheries use the Oregon moist pellet as a standard production
feed because it provides satisfactory feed conversion, and good growth and
survival, at a competitive price. The disadvantage of the Oregon moist pel-
let is that it must be transported, stored, and handled while frozen. When
thawed, it deteriorates within 12 hours.
By the mid 1950's, development and refinement of vitamin fortifications
had made possible the "complete" dry pelleted feeds as we know them to-
day.
Fish feeds manufactured in the form of dry pellets solved many of the
problems of hatchery operations in terms of feed preparation, storage, and
feeding. There are several additional advantages to pellet feeding. Pellets
require no preparation at the hatchery before they are fed. They can be
stored for 90-100 days in a cool, dry place without refrigeration. When a
fish swallows a pellet, it receives the ingredients in proportions that were
formulated in the diet. There is evidence that fish fed dry pellets are more
similar in size than those fed meat-meal. The physical characteristics of the
210 FISFi HATCHERY MANAGEMENT
pellets provide for more complete consumption of the feed. Feeding rates of
0.v5 to 10% of fish weight per day reduce the chance for feed wastage. Less
feed wastage results in far less pollution of the water during feeding and a
comparable reduction in cleaning of ponds and raceways. Pelleted feeds are
adaptable for use in automatic feeders.
Many combinations of feedstuffs were tested as pelleted feeds; some
failed because the pellets were too hard or too soft; others did not provide
the nutrient requirements of the fish.
Along with the testing and development of dry feeds, fish nutrition
researchers, relying largely on information concerning nutrition of other an-
imals such as chicken and mink, began utilizing and combining more and
more feedstuffs.
Commercial fish feeds were pelleted and marketed in advance of open-
formula feeds. A few commercial feeds failed to produce good, economical
growth and to maintain the health of the fish but, by and large, most were
very satisfactory.
Several items must be considered in developing an adequate feeding pro-
gram for fish. These include the nutrient requirements for different fish
sizes, species, environmental conditions, stress factors, types of feed, and
production objectives. General feeding methods are important and will be
discussed extensively in the last part of this section.
It would be difficult to determine which factor has the greatest effect on
a hatchery feeding program. In all probability, no one factor is more im-
portant than another, and it is a combination of many that results in an ef-
ficient feeding program. Application of the available knowledge of fish nu-
trition and feeding will result in healthy, fast- growing fish and low produc-
tion costs. A fish culturist must be able to recognize the factors affecting
feed utilization and adapt a feeding program accordingly.
Factors Influencing Nutritional Requirements
The physiological functions of a fish (maintenance, growth, activity, repro-
duction, etc.) govern its metabolism and, in turn, determine its nutritional
requirements. Metabolism is the chemical processes in living cells by which
energy is provided for vital processes and activities.
WATER TEMPERATURE
Apart from the feed, water temperature is probably the single most impor-
tant factor affecting fish growth. Because fish are cold-blooded animals,
their body temperatures fluctuate with environmental water temperatures.
Negligible growth occurs in trout when the temperature decreases to 38°F.
The lower limit for catfish is about 50°F. As the temperature rises, growth
NUTRITION AND FEEDING 211
rate, measured as gain in wet body weight or gain in length, increases to a
maximum and then decreases as temperatures approach the upper lethal
limit. The best temperature for rapid, efficient growth is that at which ap-
petite is high and maintenance requirements (or the energy cost of living)
are low.
For every 18°F increase in water temperature, there is a doubling of the
metabolic rate and, as a result, an increase in oxygen demand. At the same
time that oxygen demand is increasing at higher temperatures, the oxygen
carrying capacity of the water decreases. The metabolic rate of the fish in-
creases until the critical oxygen level is approached. Just below this point,
the metabolic rate decreases.
Temperature is a very important factor in establishing the nutrient re-
quirements of fish. To deal with this problem, the National Research
Council (NRC) reports Standard Environmental Temperatures (SET) for
various species of fish. Suggested Standard Environmental Temperatures
are 50°F for salmon, 59°F for trout, and 85°F for channel catfish. At these
temperatures the metabolic rate for these fish is 100"o. Caloric needs
increase with rising water temperatures, resulting in an increase in the
fishes' appetite. The fish culturist must, therefore, adjust the feeding rate or
caloric content of the feed to provide proper energy levels for the various
water temperatures. Failure to make the adjustment will result in less than
optimal growth and feed wastage.
SPECIES, BODY SIZE, AND AGE
Within the ranges of their optimal water temperatures, the energy require-
ments of warmwater fish are greater than those of equally active coldwater
fish of the same size. At the same water temperature, coldwater fish con-
sume more oxygen than warmwater fish, indicating a higher metabolic rate
and greater energy need. Carnivorous fish have a higher metabolic rate
than herbivorous fish because of the greater proportion of protein and
minerals in their diet. Even though fish efficiently eliminate nitrogenous
wastes through the gills directly into the water, more energy is required for
the elimination of wastes from protein utilization than from fats and car-
bohydrates. Species that are less active have lower metabolic rates and
energy requirements for activities than more active ones. In general, the
energy requirements per unit weight are greater for smaller than for larger
fish. Fish never stop growing, but the growth rate slows as the fish becomes
older. The proportional increase in size is greatest in young fish.
PHYSIOLOGICAL CHANGES
Spawning, seasonal, and physiological changes affect the rate of metabo-
lism. Growth rate becomes complicated with the onset of sexual maturity.
212 FISH HATC'HF.RY MANAGKMENT
At this point, energy, instead of being funneled into the building of body
tissues, is channeled into the formation of eggs and sperm. When sex prod-
ucts are released a weight loss as much as 10-I5"/ii occurs. Fish also have
high metabolic rates during the spawning season, associated with the
spawning activities. Conversely, during winter, resting fish have very low
metabolic rates. Fish suffering from starvation have 20% lower metabolic
rates than actively feeding fish. Excitement and increased activity elevate
the metabolic rates. All these affect the amount of energy which must be
supplied by the feed.
OTHER ENVIRONMENTAL FACTORS
Factors such as water flow rates, water chemistry, and pollution can put
added stresses on fish, and result in increased metabolic rates in relation to
the severity of the stress. Water chemistry, oxygen content, and amount of
other gases, toxins, and minerals in the water all affect the metabolic rate.
For many species, darkness decreases activity and energy requirements.
These fish grow better if they have "rest periods" of darkness than they do
in constant light.
Crowding, disease, and cultural practices also can have an affect on the
metabolism and well being of fish.
Digestion and Absorption of Nutrients
Feed in the stomach and intestine is not in the body proper because the
lining of these organs is merely an extension of the outer skin. Feed com-
ponents, such as simple sugars, can be absorbed as eaten. The more com-
plex components such as fats, proteins, and complex carbohydrates, must
be reduced to simpler components before they can be absorbed. This
breaking- down process is termed digestion. Feeds cannot be utilized by the
animal until they are absorbed into the body proper and made available to
the cells.
Absorption of nutrients from the digestive system and movement of the
nutrients within the body is a complicated process and not fully under-
stood. For nutrients to be available for biochemical reactions in the cell,
they must be absorbed from the digestive system into the blood for trans-
port to the cells. At the cellular level, they must move from the blood into
the cell.
Fish also are able to obtain some required elements directly from the wa-
ter, this being especially true for minerals.
A brief anatomical review of a fish's digestive tract will illustrate the
sites of feed digestion and absorption.
The mouth is used to capture and take in feeds. Most fish do not chew
NUTRITION AND FEEDING 213
their food, but gulp it down intact. Pharyngeal teeth are used by some
species to grind feed.
The gizzard serves as a grinding mechanism in some species of fish.
The stomach is for feed storage and preliminary digestion of protein. Very
little absorption occurs in the stomach.
The finger-like pyloric ceca at the junction of the stomach and small intes-
tines are a primary source of digestive juices.
The small intestine is the major site of digestion and receives the digestive
juices secreted by the liver, pancreas, pyloric ceca, and intestinal walls.
The absorption of the nutrients occurs in this area.
Some water absorption occurs in the large intestine, but its primary function
is to serve as a reservoir of undigested materials before expulsion as feces.
Oxygen and Water Requirements
Oxygen and water normally are not considered as nutrients, but they are
the most important components in the life-supporting processes.
All vital processes require energy, which is obtained from the oxidation
of various chemicals in the body. The utilization of oxygen and resulting
production of carbon dioxide by the tissues is the principal mechanism for
the liberation of energy. Oxygen consumption by a fish is altered by size,
feed, stress, water temperature, and activity. The oxygen requirement per
unit of weight decreases as fish size increases. High- nutrient feeds, density,
stress, elevated water temperatures, and increased activity all increase oxy-
gen requirements of fish. As a consequence, adequate oxygen must be sup-
plied to assure efficient utilization of the feed and optimal growth.
Water is involved in many reactions in animal systems either as a reac-
tant or end product. Seventy- five percent of the gain in weight during fish
growth is water. Water that is not provided in the feed itself must be taken
from the environment. Because water always diffuses from the area of
weakest ionic concentration to the strongest, water readily diffuses through
the gills and digestive tract into freshwater fish. In saltwater fish, the blood
ion concentration is weaker than that of marine water, so that the fish loses
water to the environment. This forces the fish to drink the water and ex-
crete the minerals in order to fulfill their requirements.
A nutritionally balanced feed must contain the required nutrients in the
proper proportion. If a single essential nutrient is deficient, it will affect
the efficient utilization of the other nutrients. In severe cases, nutrient defi-
ciencies can develop, affecting different physiological systems and produc-
ing a variety of deficiency signs (Appendix F). Because all essential nu-
trients are required to maintain the health of fish, there is no logic to rank-
ing them in terms of importance. However, deficiencies of certain nutrients
have more severe effects than of others. This is exemplified by a low level
214 FISH HATCHERY MANAGEMENT
of protein in the feed resulting only in reduced growth, whereas the lack of
any one of several vitamins produces well described deficiency signs. Nu-
trients such as protein and vitamins should be present in feeds at levels to
meet minimum requirements, but not in an excess which might be wasted
or cause other health problems.
The nutrients to be discussed in this chapter include (l) protein, (2) car-
bohydrates, (3) fats, (4) vitamins, and (5) minerals.
Protein Requirements
The primary objective of fish husbandry is to produce fish flesh that is
over 50% protein on a dry weight basis. Fish digest the protein in most na-
tural and commercial feeds into amino acids, which are then absorbed into
the blood and carried to the cells.
Amino acids are used first to meet the requirements for formation of the
functional body proteins (hormones, enzymes, and products of respiration).
They are used next for tissue repair and growth. Those in excess of the
body requirements are metabolized for energy or converted to fat.
Fish can synthesize some amino acids but usually not in sufficient quan-
tity to satisfy their total requirements. The amino acids synthesized are
formed from materials released during digestion and destruction of proteins
in the feed. Certain amino acids must be supplied in the feed due to the
inability of fish to synthesize them. Fish require the same ten essential a-
mino acids as higher animals: arginine; histidine; isoleucine; leucine;
lysine; methionine; phenylalanine; threonine; tryptophan; valine. Fish fed
feeds lacking dietary essential amino acids soon become inactive and lose
both appetite and weight. When the missing essential amino acids are
replaced in the diet, recovery of appetite and growth soon occurs.
In fish feeds, fats and carbohydrates are the primary sources of energy,
but some protein is also utilized for energy. Fish are relatively efficient in
using protein for energy, deriving 3.9 of the 4.65 gross kilocalories per
gram from protein, for an 84'a) efficiency. Fish are able to use more protein
in their diet than is required for maximum growth because of their effi-
ciency in eliminating nitrogenous wastes through the gill tissues directly
into the water. Nutritionists must balance the protein and energy com-
ponents of the feed with the requirements of the fish. Protein is the most
expensive nutrient and only the optimal amount should be included for
maximum growth and economy; less expensive digestible fats and carbohy-
drates can supply energy and spare the protein for growth.
Several factors determine the requirement for protein in fish feeds.
These include temperature, fish size, species, feeding rate, and energy con-
tent of the diet. Older fish have a lower protein requirement for maximum
NUTRITION AND FEEDING 215
growth than young fish do. Species vary considerably in their require-
ments; for example, young catfish need less gross protein than salmonids.
The protein requirements of fish also increase with a rise in temperature.
For optimal growth and feed efficiency, there should be a balance between
the protein and energy content of the feed. The feeding rate determines the
daily amount of a feed received by the fish. When levels above normal are
fed, the protein level can be reduced, and when they are below normal it
should be increased to assure that fish receive the proper daily amount of
protein. Fish culturists can reduce feed costs if they know the exact pro-
tein requirements of their fish.
The quality, or amino acid content, is the most important factor in op-
timizing utilization of dietary proteins. If a feed is grossly deficient in any
of the ten essential amino acids, poor growth and increased feed conver-
sions will result, despite a high total protein level in the feed. The dietary
protein that most closely approximates the amino acid requirements of the
fish has the highest protein quality value. Animal protein sources are gen-
erally of higher quality than plant sources, but animal proteins cost more.
Vegetable proteins do not contain an adequate level of certain amino acids
to meet fish requirements. Synthetic free amino acids can be added to feed,
but there is still some question as to how well fish utilize them. Thus, ami-
no acid balance at reasonable cost is best achieved by using a combination
of animal proteins, particularly fish meal, and vegetable proteins.
Fish meal seems to be the one absolutely essential feed item. Most of the
ingredients of standard catfish feed formulas can be substituted for, but
whenever fish meal has been left out poorer growth and food conversion
have resulted.
Fish cannot utilize nonprotein nitrogen sources. Such nonprotein nitro-
gen sources as urea and di-ammonium citrate, which even many non-
ruminant animals can utilize to a limited extent, have no value as a feed
source for fish. They can be toxic if present in significant levels.
The chemical composition of fish tissue can be altered significantly by
the levels and components of ingredients in feeds. Within limits, there is a
general increase in the percentage of protein in the carcass in relation to
the amount in the feed. Furthermore, there is a direct relation between the
percentage of protein and that of water in the fish body. A reduction of
body protein content in fish is correlated with increased body fat; fish fed
lower- protein feeds have more fat and less protein.
PROTEIN IN SALMONID FEEDS
The protein and amino acid requirements for salmon and trout are similar.
The total protein requirements are highest in initially feeding fry and de-
crease as fish size increases. To grow at the maximum rate, fry must have a
216 FISH HATCHERY MANAGEMENT
feed that contains at least 50''] protein; at 6—8 weeks the requirement de-
creases to 40*: of the feed and to about 35% of the feed for yearling sal-
mo nids.
Recor :ein levek in trout feeds as percent of the diet are:
Starter feed fi:y 45—55%
Grower feed fingerlings 35-5%
Production feed (older fish 30-40%
The level of protein required in feed varies with the quality- and propor-
tions :: -^ -:i. r:::e:rLi ihat make up the feed. Between 0.5 and 0.7 pound
;tary- protein is re: _ ri :o produce a pound of trout fed a balanced
jjatcherv rf £ The requireiiient for protein is also temperature- dependent.
The opcLn^ prote:- 'rr'. :- :'-e fe^d for chinook salmon is 4-0 ai 47"F
?? : rzrv rv catts:-: 7zzds
T-r 7^\^:^ :::i5 ;: ri::-;- ire rich •'- T-r-ein. Catfish may mecaboiize
5-:me i r.^r i:::f - :;: r'rrr- Prcte.r .. .:zarion is affected by the pro-
-r - ;:_.-:f i.-i ■• i:f: :-rmrer3.r.:rr. L'-'-t :-:::5h convert the best animal
z:.- 7 ::_::t ::;- —.-.- : : :. — r; z-..-: :-iz :hey do the best plant
--rzr. soyiea.- mei.. I: li - r ::hy thai a combination of protein
ii-rirs T I: iT-r: wrs- "zziwz. Tites :L=.- a.- • wz.z-- source. In catfish
:eeas. a: --'. ' :: .-r iir.ir. i- "r - tt:. :t — t-: should be animal
reins w-e- :-r;. ire red a: cem.-
'"'F cr ce.i'A. Hc-rt'e% er. a mix-
. _-.^v at both extremies. The pax-
- "r pr::rm z-z . Z'—.rri ::: :i:::3- i:^ i : size-rr.i:^
Frv :: : 'irz - z\ \'-^'i
1
Fi-r : - .:- :s 25-^5^
\^rT- :i -r t1 ii mu:- 2^ me- «;!. ea.i. izi -t reed is bala.i:-
xununojc axd feeding 217
beneficial in this regard. The amino acid requirements for catfish have not
been established, but appear to be similar to those for salmonids.
Catfish feeds — or any feeds fed in extensive culrure — are classified as
either complete or supplemental diets. Complete feeds are formulated to
contain all the \"itamins. minerals, protein, and energ^" needed by the fist.
Usually these complete feeds contain 30 to -iO'i total crude protein, of
which fish meal may make up 10 to 25^': of the feed. Complete feeds are
more expensive than supplemental feeds. Complete feeds are fed to fry,
and also to larger fish raised intensively in race\*"ays, cages, or other
en\ixonments where the intake of natural feeds is restricted.
Supplemental feeds are formulated to pro\ide additional protein, energy,
and other nutrients to fish utilizing natural food. Generally, the fish are
expected to eat natural food organisms to supply ifce essential growth fac-
tors absent in the feed. Usually supplemental feeds contain a lower level of
crude protein than complete feeds, and soybean meal is the principal pro-
tein source.
Low stocking rates and low standing crops of fish result in more natural
food and protein being available to each fish. The above factors and oth-
ers, such as season, fish size, feeding rate, water temf>erature, oxygen lev-
els, and disease influence the dietary- protein levels required for maximum
efficiency in growth. Consequently, no one protein level in feeds "v*"ill meet
all conditions and it remains for the fish culturist to choose the feed viith a
protein level that \*ill satisfy' production needs.
PROTEIN IN COOLW.\TER FISH FEEDS
Feeding trials \*ith northern pike, chain pickerel, muskellunge, vt-alle\-e,
and the hybrid tiger muskellunge showed that the hybrid and. to a lesaer
degree, northern pike v^ill accept a dr\ pelleted, formulated feed. A 50'*-
protein e.xperimental feed Appendix F formulated specifically for cool-
water fish provided the highest survival and growth •with fingerlings. Trout
feeds and exf)erimental feeds that contain less protein were inadequate.
Therefore, ii appears that the protein requirement for the fingerlings of
these species is about 50*t of the feed. It is also noteworthy that 60-SO V of
the dietarx protein was supplied by animal protein sources in feeds that
proved satisfiactor>\ Only limited testing has been conducted on feeding
advemced fingerlings of coolwater species, but indications are that the pro-
tein level of the feed can be reduced. This follows the similar pattern for
trout and catfish.
Car bo hydra U Rfquirfmrnts
Carbohydrates are a major source of energy to man and domestic animals,
but not to salmonids or catfish. Onlv limited information is av^ailable on
218 FISH HATCHF.RY MANAGEMF.NT
the digestibility and metabolism of carbohydrates by fish. All of the neces-
sary enzymes for digestion and utilization of carbohydrates have been
found in fish, yet the role of dietary carbohydrates and the contribution of
glucose to the total energy requirement of fishes remain unclear.
There is little carbohydrate (usually less than 1.0"/ii of the wet weight) in
the fish body. After being absorbed, carbohydrates are either burned for
energy, stored temporarily as glycogen, or formed into fat. Production of
energy is the only use of carbohydrates in the fish system. No carbohydrate
requirements have been established for fish because carbohydrates do not
supply any essential nutrients that cannot be obtained from other nutrients
in the feed.
The energy requirement of a fish may be satisfied by fat or protein, as
well as by carbohydrate. If sufficient energy nutrients are not available in
the feed the body will burn protein for energy at the expense of growth
and tissue repair. The use of carbohydrate for energy to save protein for
other purposes is known as the "protein- sparing effect" of carbohydrate.
Carbohydrate energy in excess of the immediate energy need is convert-
ed into fat and deposited in various tissues as reserve energy for use during
periods of less abundant feed. Quantities in excess of needed levels lead to
an elevated deposition of glycogen in the liver, and eventually will cause
death in salmonids.
Fat-infiltrated livers and kidneys in salmonids are a result of fat deposi-
tion within the organ, resulting in reduced efficiency and organ destruc-
tion. This condition results primarily from excess levels of carbohydrates in
the feed.
Carbohydrates also may serve as precursors for the various metabolic in-
termediates, such as nonessential amino acids, necessary for growth. Thus,
in the absence of adequate dietary carbohydrates or fats, fish may make
inefficient use of dietary protein to meet their energy and other metabolic
needs. In addition to serving as an inexpensive source of energy, starches
improve the pelleting quality of fish feeds.
Dietary fiber is not utilized by fish. Levels over 10% in salmonid feeds
and over 20% in catfish feeds reduce nutrient intake and impair the digesti-
bility of practical feeds.
CARBOHYDRATES IN SALMONID FEEDS
Carbohydrates are an inexpensive food source, and there is a temptation to
feed them at high levels. However, trout are incapable of handling high
dietary levels of carbohydrates. The evidence for this is the accumulation
of liver glycogen after relatively low levels of digestible carbohydrate are
fed. Trout apparently cannot excrete excessive dietary carbohydrate. In
higher animals, excessive carbohydrate is excreted in the urine. Such ex-
cretion does not occur in trout even though the blood sugar is greatly in-
NUTRITION AND FEEDING 219
creased. In trout, the accumulation of blood glucose follows the same pat-
tern as that in diabetic humans.
No absolute carbohydrate requirements have been established for fish.
Trout nutritionists have placed maximum digestible carbohydrate values
for feeds at 12-20"o. Digestible carbohydrate values are determined by
multiplying the total amount of carbohydrate in the feed by the digestibil-
ity of the carbohydrates. Digestibility values of various carbohydrates are:
simple sugars, 100%; complex sugars, 90%; cooked starch, 60%; raw starch,
30%; fiber, 0%.
Digestible carbohydrate levels over 20''o in trout feeds will cause an ac-
cumulation of glycogen in liver, a fatty infiltrated liver, fatty infiltrated
kidneys, and excess fat deposition, all of which are detrimental to the
health of the fish.
Levels of carbohydrates up to 20"ii can be tolerated in trout feeds in
55-65°F water. These same feeds fed in water below 50°F will cause exces-
sive storage of glycogen in the liver and can result in death. Carbohydrates
should, therefore, be limited in trout feeds. However, there are definite
beneficial effects from the carbohydrate portion of the feed. It can supply
up to 20"i) of the available calories in a feed, thus sparing the protein. The
energy from carbohydrates available to mammals is 4 kilocalories per gram,
whereas the value for trout is only 1.6 kcal/g, a 40%i relative efficiency.
Most trout feeds do not contain excessive amounts of digestible carbohy-
drate. A balance between plant and animal components in the feeds gen-
erally will assure a satisfactory level of digestible carbohydrate. The major
sources of carbohydrate in trout feeds are plant foodstuffs, including soy-
bean oil meal, cereal grains, flour by-products, and cottonseed meal. Most
animal concentrates such as meat meals, fish meals, tankage, and blood
meals, are low in carbohydrate (less than 1.0%). The high percentages of
milk sugar in dried skim milk, dried buttermilk, and dried whey may cause
an increase in blood sugar and an accumulation of glycogen in the liver if
fed at levels greater than lO"" of the feed.
Pacific salmon have been reported to tolerate total dietary carbohydrate
levels as high as 48"(i, with no losses or liver pathology. The digestible car-
bohydrate value would be lower, depending on the forms of the carbohydrate.
CARBOHYDRATES IN CATFISH FEEDS
Dietary carbohydrates are utilized by catfish, but only limited information
is available on their digestibility and metabolism. Channel catfish utilize
starches for growth more readily than sugars. In feeds containing adequate
protein, fish weight increases with the level of starch, but remains essential-
ly the same regardless of the amounts of sugar in the feed. Liver abnormal-
ities, poor growth, and high mortality observed in salmonids due to high
levels of dietary carbohydrates have not been found in catfish.
220 FISH HAICIIKRV MANAGEMENT
No carbohydrate requirements have been estabHshed for catfish; how-
ever, carbohydrates can spare protein in catfish feeds. In the absence of
adequate dietary carbohydrates or fats, catfish make inefficient use of
dietary protein to meet their energy and other metabolic needs. In channel
catfish, lipids and carbohydrates appear to spare protein in lower-energy
feeds but not in higher-energy feeds.
Fiber is an indigestible dietary material derived from plant cell walls.
Fiber is not a necessary component for optimum rate of growth or nutrient
digestibility in channel catfish production rations. Fiber levels as high as
21% reduce nutrient intake and impair digestibility in feeds for channel
catfish. Fiber in concentrations of less than 8% may add structural integrity
to pelleted feeds, but larger amounts often impair pellet quality. Most of
the fiber in the feed ultimately becomes a pollutant in the water.
Lipid Requirements
Lipids comprise a group of organic substances of a fatty nature that in-
cludes fats, oils, waxes, and related compounds. Lipids are the most con-
centrated energy source of the food groups, having at least 2.25 times more
energy per unit weight than either protein or carbohydrates. In addition to
supplying energy, lipids serve several other functions such as reserve ener-
gy storage, insulation for the body, cushion for vital organs, lubrication,
transport of fat-soluble vitamins, and maintenance of neutral bouyancy.
They provide essential lipids and hormones for certain body processes and
metabolism, and are a major part of reproductive products.
Although each fish tends to deposit a fat peculiar to its species, the diet
of the fish will alter its type. The fat deposited tends to be similar to the
fat ingested. The body fat of fish consuming natural foods contains a high
degree of polyunsaturated (soft) fats similar to those in the food. Because
natural fats are soft fats that are mobilized and utilized by the fish more ef-
ficiently than hard (saturated) fats, soft fats are beneficial for efficient pro-
duction and fish health. Preliminary studies have indicated that some hard
fats can be used by warmwater fish.
The effect of water temperature on the composition of the body fat of
fish is difficult to define clearly due to its influence on the digestibility of
hard and soft fats. Soft fats are digested easily in both warm and cold wa-
ter, but hard fats are digested efficiently only in warm water. Fish living in
cold water have body fats that are highly unsaturated with a low melting
point. These fish are able to more readily adapt to a low environmental
temperature.
Factors to be considered in evaluating dietary lipids for fish feeds in-
clude digestibility, optimal level in the feed, content of fatty acids essential
NUTRITION AND FKEDING 221
for the fish, presence of toxic substances, and the quality of the lipid. Fish
and vegetable oils that are polyunsaturated are more easily digested by fish
than saturated fats such as beef tallow, especially at colder temperatures.
The optimal level of dietary lipid for fish feeds has not been established.
Protein content of the feed, and type of fat need to be considered in deter-
mining the amount to be used in the feed for a given fish species. Lipids
are a primary source of energy for fish and have a protein- sparing effect.
Therefore high levels in the feed would be beneficial. However, high fat
levels in the feed can hamper the pelleting of feeds and cause rapid
spoilage of feed during storage.
Rancidity of lipids, especially of polyunsaturated oils, due to oxidation
can be a problem in fish feeds. Rancid lipids have a disagreeable odor and
flavor and can be toxic to fish. The toxic effects may be due to products of
the oxidation of the lipid itself or to secondary factors such as destruction
of vitamins or mold growth. Oxidation of lipids in the feed often results in
the destruction of vitamins, especially vitamin E. The oxidation process
also produces conditions that favor mold growth and breakdown of other
nutrients. Because rancid lipids in the feed are detrimental to fish, every ef-
fort should be made to use only fresh oils protected with antioxidants.
Feeds should be stored in a cool, dry area to minimize oxidation of the
lipids in the feeds.
Contamination of fish feeds, especially those for fry and broodstock, with
pesticides and other compounds such as polychlorinated biphenols (PCB)
cause many health problems and may be lethal in fish. Fish oil is a com-
mon source of contaminants in fish feeds. Because most contaminants are
fat-soluble they accumulate in the fatty tissues of fish. When fish oil is ex-
tracted from fish meal, these compounds are concentrated in the oil. Fish
used in the production of fish meal and oil pick up these compounds from
their natural foods in a contaminated environment. Feed manufacturers
should select only those fish oils that contain low levels or none of these
compounds. Vegetable oils, which are naturally free of these compounds,
also can be used.
LIPID REQUIREMENTS FOR SALMONIDS
When there is little or no fat in the feed, a trout forms its own fat from car-
bohydrates and proteins. The natural fat of a trout is unsaturated with a
low melting point. Practical-feed formulators use fish oil and vegetable oil
in trout feeds as the primary energy source. These oils are readily digested
by the trout and produce the desired soft body fat. Hard fats such as beef
tallow are not as readily digested because they are not emulsified easily,
especially in cold temperatures. Hard fats can coat other foods and reduce
their digestibility, thus lowering the performance of the feed. Very hard
fats may plug the intestines of small trout.
222 FISH HATCHERY MANAGEMENT
Body fat of a hatchery trout fed production feeds is harder (more satura-
ted) than that of a wild trout, but after stocking the body fat gradually
changes to a softer (unsaturated) type. This can be attributed to both the
change in environment and feed.
Linolenic fatty acids (omega-3 type) are essential for trout and salmon,
and should be incorporated at a level of at least 1% of the feed for max-
imum growth response. This may be supplied by the addition of 3-5% fish
oil or 10% soybean oil.
The level of dietary lipid required for salmon or trout depends on such
factors as the age of the fish, protein level in the feed, and the nature of
the supplemental lipid. The influences of age of the fish and protein level
of the diet are interrelated; young trout require higher levels of both fat
and protein than older trout. For best performance, the recommended per-
centage of fat and protein for different ages of trout and salmon should be
as follows:
% protein % fat
Starter feeds (fry) 50 15
Grower feeds (fingerlings) 40 12
Production feeds (older fish) 35 9
Hatchery personnel can check the protein and fat content of trout feeds ei-
ther on the feed tag for brand feeds or in the feed formulation data for
open-formula feeds to determine if these recommended nutrient levels are
being supplied by the feed they are using.
High levels of dietary fat and, to a lesser degree, excess protein or car-
bohydrates can cause fatty infiltration of the liver. Fatty infiltrated livers
are swollen, pale yellow in color, and have a greasy texture. The level of
fat in affected livers may be increased to several times greater than normal.
This condition usually is accompanied by fatty infiltration of the kidney
and can lead to edema and death by reducing the elimination of wastes
through the urinary system.
Fatty infiltrated livers should not be confused with fatty degeneration of
the liver or viral liver degeneration. Fatty degeneration of the liver is
caused by toxins from rancid feeds, chemical contaminates, certain algae,
or natural toxins. This condition is typified by acute cellular degenerative
changes in the liver and kidney. The liver is swollen, pale yellow in color
with oil droplets in the tissue, but does not feel greasy (Figure 7l). Rancid
fats in feeds stored for long periods (more than six months) or under warm,
humid conditions are the primary cause of this disorder in hatchery- reared
trout. Rainbow trout are most severely affected and brook trout to a lesser
degree, but brown trout are rarely affected by rancid oils in the feed. Viral
liver degeneration differs from the others by the presence of small hemor-
rhagic spots in the liver and swelling of the kidney. Anemia is characteris-
tic of advanced stages of all three liver disorders.
NUTRITION AND FEEDING 223
Figure 71. Rainbow trout with liver lipoid degeneration (ceroidosis) of
increasing severity from top to bottom. Note yellowish- brown coloration of
livers of middle and bottom fish. (Courtesy Dr. P. Ghittino, Fish Disease
Laboratory, Tonino, Italy.)
Figure 72. Folic acid-deficient (top) and control (bottom) coho salmon.
Note the extremely pale gill, demonstrating anemia, and exophthalmia in
folic acid-deficient fish. (Courtesy Charlie E. Smith, FWS, Bozeman,
Montana.)
224 FISH HAICHKRY MANAGEMENT
LIPID REQUIREMENTS FOR CA lEISH
Lipid level and content of essential fatty acids have received little con-
sideration in diets for channel catfish, because little is known about the ef-
fects of, and requirements for, these nutrients in catfish. In practice, the
dietary requirements have been met reasonably well by lipids in the fish
meal and oil-rich plant proteins normally used in catfish feeds and those in
natural food organisms available in ponds.
Weight gain and protein deposition increase as the level of fish oil is
elevated to 15'^ of the dry feed. At the 20'}(i level, the gain decreases. Cat-
fish fed corn oil did not gain as well as those fed fish oil in the feed, show-
ing that fish oil is a better source of dietary lipid.
Beef tallow, safflower oil, and fish oil were evaluated at temperatures
from 68 to 93°F. Maximum growth was obtained at 86°F by catfish fed
each lipid supplement. Highest gains and lowest food conversion rates were
obtained with fish oil, followed by beef tallow and safflower oil. As with
salmonids, catfish have little or no requirement for linoleic (omega-6) fatty
acids in the feed. No requirements for essential fatty acids in catfish feeds
have been determined.
Commercial catfish feeds contain less than 8% dietary lipids. Test feeds
with 10% lipid provided the best growth, whereas 167(1 in the feed did not
improve growth or enhance protein deposition.
Lipids have the most effect on taste and storage quality of fish products.
Tests with animal and vegetable fats showed that fish oil has a significant
adverse effect on the flavor of fresh and frozen fish. Beef tallow also influ-
enced the flavor, but did not induce the "fishy" flavor produced by the
fish oil. Fish reared on safflower oil or corn oil have a better flavor than
those fed beef tallow or fish oil. Catfish producers may be able to use an-
imal fats and oils in fingerling feeds to obtain rapid growth and efficient
deposition of protein, then change to a finishing diet made with vegetable
oils to improve the flavor as the fish approach market size.
Energy Requirements
Energy is defined as the capacity to do work. The work can be mechanical
(muscular activity), chemical (tissue repair and formation), or osmotic
(maintenance of biological salt balance). Fish require energy for growth, ac-
tivity, reproduction, and osmotic balance. Energy requirements of species
differ, as do their growth rates and activities. Other factors that alter the
energy requirements are water temperature, size, age, physiological activity,
composition of the diet, light exposure, and environmental stresses.
Food energy is usually expressed as kilogram calories (kcal or Cal). It is
released in two forms, heat energy and free energy, in animal systems. Heat
energy has the biological purpose of maintaining body temperature in
NUIRITION AND FEEDING 225
warm-blooded animals, but this is of less importance to fish because a fish's
body temperature corresponds to environmental water temperatures. Usual-
ly, the body temperature of a resting fish will be at or near the environ-
mental water temperature. Free energy is available for biological activity
and growth and is used for immediate energy and for formation of body tis-
sue or is stored as glycogen or fat.
Fish adjust their feed intake according to their energy needs. An exces-
sively high energy level in a feed may restrict protein consumption and
subsequent growth. Except for the extremes, fish fed low-energy feeds are
able to gain weight at a rate comparable to those fed high-energy feeds by
increasing their feed intake. If a feed does not contain sufficient nonprotein
energy sources to meet the fish's energy requirements then the protein nor-
mally used for growth will have to be used for energy. Therefore, it is diffi-
cult to determine a specific energy or protein requirement without consid-
ering the relative level of one to the other. Absolute figures on optimum
energy requirements are difficult to state in fish nutrition because fish can
be maintained with little growth on a low-energy intake or be forced to
produce more weight by feeding them in excess. To maintain optimum
growth and the efficiency of a feeding program, the feeding level should be
adjusted if energy levels of the feeds vary significantly. The feeding level
should be increased for low-energy feeds and decreased for high-energy
feeds. Energy needs for maintenance increase with rising water tempera-
tures and decrease when temperatures are reduced, thus requiring changes
in the feeding rates. However, more energy is required to produce weight
gains of fish at lower temperatures than at high temperatures.
Fish normally use about 70"" of the dietary energy for maintenance of
their biological systems and activity, leaving about 30"o available for
growth. Energy requirements for vital functions must be met before energy
is available for growth. A maintenance- type feeding program is designed to
supply the minimum energy and other essential nutrients for the vital func-
tions and activity, with no allowance for growth. Dietary efficiency or feed
conversion are terms used to designate the practical conversion of food to
fish flesh. In this concept of estimating gross energy requirements, the
amount of food (energy) required to produce a unit of weight gain is deter-
mined. In general, if the conversion of food to fish flesh is two or less, en-
ergy requirements are being met. This is because energy for biological
maintenance of fish must be supplied before energy is available for growth.
ENERGY REQUIREMENTS FOR SALMONIDS
Brook, brown, rainbow, and lake trout have similar energy requirements.
Between 1,700 and 1,800 available dietary kilocalories are required to pro-
duce a pound of trout, depending upon the feed being fed and conditions
under which the fish are reared. The amount of available calories from fish
feeds depends upon the digestibility of nutrients by the fish.
226 FISH HATCHERY MANAGEMENT
Gross
Available
kcal
Digestibility
kcal
Nutrient
(per gram)
(percent)
(per gram)
Protein
5.6
70
3.9
Fat
9.4
85
8.0
Carbohydrate
4.1
40
1.6
The values above show that salmonids make more efficient use of energy
from fats than from proteins, and least efficient use of carbohydrates. There
is evidence that trout must use some protein for energy. In trout feeds,
between 55 and 65% of the total available dietary calories are from the pro-
tein.
The available calories in 100 grams of a salmon or trout production feed
can be calculated as follows:
Percent
Available
Energy
Nutrient
of feed
kcal
content
Protein
45%
X
3.9
175.5 kcal
Fat
10%
X
8.0
80.0 kcal
Moisture
10%
X
0
0.0 kcal
Ash
10%
X
0
0.0 kcal
Carbohydrates
25%
X
1.6
40.0 kcal
Total = 295.5 kcal/100 grams or 1,341 kcal/pound
An estimated conversion can be calculated for salmonids by using the
energy requirement to produce a pound of fish and the available calories in
the feed.
kcal to rear a pound of trout (l,700) , 0-7 r i
' -. r = 1.27 teed conversion
Available kcal per pound of feed (1,341)
ENERGY REQUIREMENTS FOR CATFISH
Available kilocalories required to produce a pound of catfish vary from 881
to 1,075, depending on the feed and size of fish. Growth and feed conver-
sions demonstrate that larger catfish require lower levels of protein and
higher levels of energy than smaller catfish. Nutrient digestibility and en-
ergy values for catfish are:
Gross
Available
kcal
Digestibility
kcal
Nutrient
(per gram)
(percent)
(per gram)
Protein
5.6
80
4.5
Fat
9.4
90
8.5
Carbohydrate
4.1
70
2.9
NUTRITION AND FEEDING
227
The available calories in catfish feeds and estimated feed conversions can
be calculated by the same procedures as for salmonid feeds, with appropri-
ate values for catfish being substituted.
Vitamin Requirements
Vitamins are not nutrients, but are dietary essentials required in small
quantities by all forms of plant and animal life. They are catalytic in na-
ture and function as part of an enzyme system.
For convenience, vitamins are broadly classified as fat-soluble vitamins
or water-soluble vitamins. The fat-soluble vitamins usually are found asso-
ciated with the lipids of natural foods and include vitamins A, D, E, and
K. The water soluble vitamins include vitamin C and those of the B com-
plex: thiamine (B,), riboflavin (B^), biotin, folic acid, cyanocobalamin (B12)
and inositol.
Vitamins are distributed widely in ingredients used in fish feeds. Some,
such as yeast, contain high levels of several vitamins. The level of vitamins
supplied by the ingredients in the feed usually is not adequate to meet the
fishes' requirements. These requirements are presented in Table 24. Most
Table 24. vitamin requirements expressed as milligrams or interna-
tional UNITS (lU) PER POUND OF DRY FEED FOR SALMONIDS AND WARMWATER
FISHES. (SOURCE: NATIONAL RESEARCH COUNCIL 1973, 1977.)
WARMWATER FISHES
SUPPLEMENTAL
COMPLETE
vitamin
SALMONIDS
FEED
FEED
A (lU)
908
908
2,497
DgdU)
n
100
454
E (lU)
13.6
5
22.7
K
36.3
2.3
4.5
Thiamine
4.5
0
9.1
Riboflavin
9.1
0.9-3.2
9.1
Pyridoxine
4.5
5
9.1
Pantothenic acid
18.2
3.2-5
22.7
Biotin
0.45*
0
0.04
Choline
1362
200
250
Vitamin B12
0.009
0.0009-0.004
0.009
Niacin
68
7.7-12.7
45.4
Ascorbic acid
45.4
0-45.4
13.6-45.4
Folic acid
2.3
0
2.3
Inositol
182
0
45.4
Required level is not established.
Brown trout require twice the level presented.
228 FISH HATCHERY MANAGEMENT
vitamins can be manufactured synthetically; these are both chemically and
biologically the same as naturally occurring substances. Synthetic vitamins
can be added to feeds with great precision as a mixture (referred to as a
premix) to complement the natural vitamins and balance the vitamin con-
tent of the finished feed.
Calculations of the vitamin levels to be placed in feeds should provide
for an excess, for several reasons: (l) the efficiency with which fish use the
vitamins in ingredients is unknown; (2) vitamins in fish feeds are destroyed
by heat and moisture primarily during manufacturing but also during
storage; (3) breakdown of other substances in the feed (such as oxidation
of oils) may destroy some vitamins; and (4) vitamins react with other com-
pounds and become inactive.
Several vitamins show moderate to severe losses when incorporated into
feeds and stored at different temperatures and relative humidities. Among
them are vitamins A, D, K, C, E, thiamine, and folic acid. Vitamin C (as-
corbic acid) has received considerable attention. Typical losses of vitamin
C in feeds are:
Storage
Feed Temperature Duration Loss
Catfish feeds (dry) 70°F 3 months 50%
Oregon moist pellet — 14°F 3 months None
40-46°F 3 days 85%
70°F 11 hours 81%
Assays performed on Oregon moist pellet that had been stored 5 months
and then thawed for 14 hours showed reductions of vitamin levels as fol-
lows:
Change in
Vitamin concentration (mg/kg diet)
C 893 to 10
E 503 to 432
K 18.6 to 2.0
Folic acid 7.1 to 5.3
Pantothenic acid 106 to 99
Vitamin E is reduced continually from the time the feed is manufactured
until it is fed, due to oxidative rancidity of oils in the feed; vitamin E
serves as an antioxidant. For these reasons, all feeds should be used within
NUTRITION AND FEEDING 229
a 3-month period if at all possible. It is important to store fish feed in a
cool dry place and to avoid prolonged storage if fish are to be provided
with levels of vitamins originally formulated into the feed. Steps can be
taken to help preserve the vitamins in the feed. Some synthetic vitamins
can be protected by a coating of gelatin, fat, or starch. The addition of an-
tioxidants reduces the oxidation of oils and its destructive effect on vita-
mins. Maintaining cool, dry storage conditions to eliminate spoilage and
mold growth preserves the feed quality and vitamins.
Because the metabolic processes and functions of biological systems of
fish are similar to those of other animals, it is safe to assume that all vita-
mins are required by all species. However, the recommended amounts of
the vitamins for different fishes vary. The required levels of vitamins must
be added to the ration routinely in order to prevent deficiencies from oc-
curring (Figures 72 and 73). Deficiencies of most known vitamins have
been described (Appendix F).
The total amount of vitamins required by a fish increases as the fish
grows. Conversely, food intake decreases as a percent of body weight as the
fish increases in size, which can cause a vitamin deficiency if the feed con-
tains only the minimum level of vitamins. Therefore, feeds for older fish
also need to be fortified with vitamins.
As temperature decreases, so does food intake. However, the vitamin re-
quirements of fish do not decrease proportionally. A vitamin deficiency can
occur with low intake of diets containing marginal levels of vitamins.
Complete catfish feeds are formulated to contain all of the essential vita-
mins in amounts required by the fish and are designed to provide normal
growth for fish that do not have access to natural feeds. Supplemental feeds
contain the vitamins supplied by the feed ingredients plus limited supple-
mentation, as the fish are expected to obtain vitamins from natural foods
in the pond.
Mineral Requirements
As nutrients in fish feeds, minerals are difficult to study. Absorption and
excretion of inorganic elements across the gills and skin have an osmoregu-
latory as well as a nutritional function. Absorption of inorganic elements
through the digestive system also affects osmoregulation.
The specific qualitative and quantitative dietary needs will, therefore,
depend upon the environment in which the fish is reared and on the type
of ration being fed. Dietary requirements for most minerals have not been
established for fish, but fish probably require the same minerals as other
230
FISH HATCHERY MANAGEMENT
^-"'^
Figure 73. Gill lamellae from (l) a normal and (2) a pantothenic acid-deficient
rainbow trout. Hyperplasia of the epithelium has resulted in fusion of most
lamellae (arrow) on two filaments of the pantothenic acid-deficient trout. (Cour-
tesy Charlie E. Smith, FWS, Bozeman, Montana.)
animals for growth and various metabolic processes. As mentioned, fish
also use mineral salts and ions to maintain osmotic balance between fluids
in their body and the water.
Many minerals are essential for life, but not all are needed in the same
amount. Seven major minerals are required in large amounts and constitute
60 to 80% of all the inorganic materials in the body. The seven are calci-
um, phosphorus, sulfur, sodium, chlorine, potassium, and magnesium.
NUTRITION AND FEEDING 231
Trace minerals are just as essential as major minerals, but are needed
only in small amounts. The nine essential trace minerals are iron, copper,
iodine, manganese, cobalt, zinc, molybdenum, selenium, and fluorine.
Mineral elements, both major and trace, are interrelated and balance
each other in their nutritional and physiological effects. The minerals that
form the hard and supporting structures of a fish's body (bone and teeth)
are principally calcium and phosphorus. Very small amounts of fluorine
and magnesium also are essential for the formation of bones and teeth. For
normal respiration iron, copper, and cobalt are required in the red cell and
deficiencies of any of these trace elements may cause anemia. Sodium,
chlorine, and potassium play an important role in regulating body
processes and osmotic pressure. Minerals also are required for reproduc-
tion. They are removed from the female system during egg production and
must be replenished by adequate amounts in the feed.
Most researchers agree that fish require all of the major and trace ele-
ments. Under normal conditions, chloride ions are exchanged very rapidly
from both food and water. Calcium and cobalt are absorbed efficiently
from the water but are utilized poorly from feeds. The level of calcium in
the water influences the uptake of the calcium from the food, and vice
versa.
Feeds are a major source of phosphorus and sulfur. Inorganic phosphorus
is absorbed efficiently from the stomach and intestine of trout. The skin
(including the scales) in trout is a significant storehouse for calcium and
phosphorus.
Only one mineral deficiency is recognized definitely in trout; as in
higher animals, a deficiency of iodine causes goiter. The study of the
mineral requirements of fish is incomplete, but it is apparent that both dis-
solved and dietary minerals are important to the health and vigor of fish.
Nonnutritive Factors
Although nonnutritive factors do not contribute directly to the mainte-
nance, growth, or reproduction of fish, they should be considered in the
formulation of rations as they can affect feed efficiency and the quality of
the final marketable product. Three nonnutritive factors — fiber, pigment-
producing factors, and antioxidants — warrant discussion concerning fish
nutrition.
FIBER
Due the simple structure of the gastrointestinal tract of fish, the digestibil-
ity of fiber in fish is extremely low, less than 10"o. Very little microbial
232 FISH HATCHERY MANAGEMENT
breakdown of fiber has been noted. Herbivorous fish can tolerate higher
amounts of fiber than carnivores. It is recommended that crude fiber not
exceed 10% in fish feeds and preferably not more than 5 or 6%. Some fiber
is useful, however, because it supplies bulk and facilitates the passage of
food through the fish.
PIGMENT-PRODUCING FACTORS
Often, producers wish to add color to fish in order to make their product
more attractive to the consumer. This can be achieved through food addi-
tives. Paprika fed at Tin of the feed will improve the coloration of brook
trout. Xanthophylls from corn gluten meal, dried egg products, and alfalfa
meal will increase yellow pigmentation of brown trout skin. Shrimp or
prawn wastes, which contain carotinoids, produce a reddish coloration
when fed to trout. Where regulations allow, canthaxanthin can be incor-
porated into trout feeds to impart a red color to the flesh and eggs. Species
differences have been observed, and it is possible to develop color in one
species of fish, but not another.
ANTIOXIDANTS
Fish feeds contain high levels of unsaturated oils which are easily oxidized,
resulting in breakdown of oils and other nutrients. This can be controlled
by the addition of antioxidants such as butylhydroxytoluene (BHT), bu-
tylhydroxyanisole (BHA), ethoxyquin, and vitamin E. The levels of BHT,
BHA, and ethoxyquin allowed in feeds by regulations often are not ade-
quate to control oxidation of the high levels of unsaturated oils in fish
feeds. Therefore, feed formulators should add antioxidants to the levels
permitted by the regulations to protect the oils in fish feeds and supple-
ment with vitamin E if additional antioxidation is needed. Ethoxyquin and
vitamin E are biological antioxidants that function in the fish's physiologi-
cal system as well as in feed preservation. The level of vitamin E in fish
feeds must be adequate to prevent oxidation of oils and still meet the nu-
tritional requirement of the fish.
Materials Affecting Fish Quality and Flavor
Fish fed wet feeds containing meat or fish products tend to deposit higher
levels of body fat and have soft textured flesh, whereas those fed dry feeds
have a more desirable flavor and firmer flesh. Fresh fish in feeds can im-
part an off- flavor to the flesh of the fish eating it.
NUTRITION AND FEEDING 233
Other substances such as algal blooms, muskgrass, chemicals, and organic
compounds can produce undesirable flavors in fish. When the water tempera-
ture is high, as it is in late summer, there is a greater chance that off-flavors
will occur in fish flesh.
Organic Toxicants in Feeds
Numerous naturally occurring and synthetic organic compounds produce
toxic responses in fish. Tannic acid, aflatoxin, and cyclopropenoid fatty acids
all induce liver cancer in fish. Gossypol, a toxin present in untreated cot-
tonseed meal, causes anorexia and ceroid accumulation in the liver. Phytic
acid, which ties up zinc in the feed, and growth inhibitors found in soybean
meal can be destroyed by proper heating during processing. Chlorinated
hydrocarbons occur as contaminants of fish meal and can cause mortality
when present in fry feeds. Broodfish transfer these compounds from the feed to
their eggs, resulting in low hatchability and high mortality of swim- up fry.
Toxaphene affects the utilization of vitamin C in catfish and can cause the
"broken back syndrome." The environment and feed should be free of toxi-
cants to maintain the health and efficient production of fish. Symptoms of
some organic toxicants are given in Appendix F.
Sources of Feeds
NATURAL FOODS
As the name implies, natural foods are obtained from the immediate en-
vironment. Small fish feed upon algae and zooplankton. As the carnivorous
fish grow, they devour progressively larger animals — insects, worms, mol-
lusks, crustaceans, small fish, tadpoles, and frogs. Many fish remain her-
bivorous throughout their lives.
Pondfish culturists take advantage of the natural feeds present in still
waters. The composition of insects, worms, and forage fish used as fish food
is mostly water (75-80"o). The remaining components are protein (l2-15%),
fat (3-7%), ash (l-4"(i), and a little carbohydrate (less than 1%). During
warm weather when insects hatch and bottom organisms are abundant, a
pond can provide a considerable amount of feed for fish. This production
can be increased by pond fertilization. Because the environment tends to
be highly variable in its production of biomass, natural methods of provid-
ing food are inefficient unless the producer is utilizing large bodies of wa-
ter. Natural food organisms are relied upon to provide nutrients lacking in
the supplemental feeds used in pond culture.
234 FISH HMCHERY MANAGEMENT
FORMULATED FEEDS
Formulated feeds are a mixture of ingredients processed into pellets,
granules, or meals and may be either supplemental or complete rations.
Supplemental feeds are formulated to contain adequate protein and en-
ergy, but may be deficient in vitamins and minerals which the fish are ex-
pected to obtain from natural foods. Such feeds are fed to catfish and other
fish reared at low densities in ponds.
Complete feeds are formulated to provide all essential vitamins and nu-
trients required by fish and are designed to provide optimal growth. If high
densities of fish are being reared, a complete feed must be provided, as na-
tural feeds will be limited or absent. Such feeds must be of a physical con-
sistency that will allow them to be fed in the water without breaking down,
but still be easily ingested and digested by the fish. Properly sized feeds
are required for different sizes of fish because fish normally do not chew
their food. The feed must be palatable to the fish so that it will be readily
consumed and not left to dissipate into the water. Dust and fine particles
that may occur in the large-sized feeds will create problems because they
are not efficiently consumed and, if present in excess, cause water pollution
and gill disease.
Feed Manufacturing
Formulated feeds are manufactured in the forms of meals, granules,
compressed pellets (sinking), expanded pellets (floating), and semimoist
pellets. The use of dry pelleted feeds provides several advantages over oth-
er feeding programs. Such feeds are available at all times of the year in any
quantity. Fish producers can select the size of feed satisfactory for feeding
fish through the rearing cycle. Pelleted feeds give lower feed conversions
and lower feed cost per unit of weight gain than natural or wet feeds and
cause less waste and contamination of the rearing water. No hatchery labor
is required to prepare the feed. Pelleted feeds purchased in bulk provide
additional efficiency in lower costs of handling and storage. The conven-
ience of using automatic feeding equipment is also possible with bulk
feeds.
Compressed or sinking pellets are made by adding steam to the feed as it
goes into the pellet mill. The steam increases the moisture content by 5 to
6% and raises the temperature to 150-I80°F during processing. The mix-
ture is forced through a die to extrude a compressed, dense pellet. The pel-
lets are air- dried and cooled immediately after pelleting. The moisture con-
tent of pellets must be sufficiently low (less than 10%) to prevent mold
growth during storage.
NUTRITION AND FEEDING 235
The manufacture of expanded or floating pellets requires higher tem-
peratures and pressures. Under these conditions, raw starch is quickly gela-
tinized. Bonds are formed within the gelatinized starch to give a durable,
water-stable pellet. The sudden release of pressure following extrusion al-
lows water vapor to expand and the ensuing entrapment of gas creates a
buoyant food particle. The additional cost of producing floating feeds must
be carefully compared to the advantages of using a floating feed. Many
catfish producers prefer the floating feeds because they can observe the fish
feeding. This aids in pond management and reduces feed wastage due to
overfeeding and loss of pellets that sink into the bottom muds. Recent
studies with catfish have shown that feeding 15°<) of the ration as floating
feed and 85% as sinking feed gives better feed utilization and is more
economical than feeding either alone.
Although the extrusion of feeds may result in the destruction of certain
vitamins, amino acids, and fats, the lost materials can be replaced by spray-
coating the pellets before packaging. Color may also be added at this time.
A moist, pelleted fish feed containing 30-35% water can be made with
special ingredients and equipment. No heat is required in pelleting moist
feeds. Mold inhibitors, hygroscopic chemicals, or refrigeration must be used
to protect moist feeds against spoilage. After extrusion the pellets are
quick- frozen and stored at — 14°F. If properly handled, the pellets will
remain separate without lumping. Moist pelleted feed spoils rapidly when
thawed and a major loss of vitamins will result within a few hours.
Moist feeds cost more to manufacture, ship, and store than dry pelleted
feeds because they must be kept frozen. But they are beneficial in feeding
fish that do not accept dry formulated feeds. Fingerlings of some species
prefer the soft moist feeds because they are similar in texture to natural
feeds. Moist feeds have been used successfully as an intermediate stage in
converting fish from natural food to dry formula feeds.
Salmon producers are the major users of moist feeds. The Oregon moist
pellet can be obtained at a competitive price from several commercial feed
companies in the northwest.
Open- and Closed-Formulated Feeds
There are open and closed formula feeds. An open- formula feed is one for
which the complete formula is disclosed. Generally, such feeds have been
developed by state or federal agencies or universities. An open- formula
feed has the following advantages.
(l) The producer knows exactly what is in the feed, including the level
of vitamin supplementation.
23fi FISH HATCHF.RY MANAGEMENT
(2) Because the same formulation and quality of ingredients are used, the
feed will be consistent from one production season to the next.
(3) Competitive bidding is possible for the specified feed.
(4) The feed can be monitored through a quality-control program.
In using open- formula feeds, however, the buyer assumes full responsi-
bility for feed performance because the manufacturer has followed contract-
ed instructions. This requires the buyer to have concise manufacturing and
formula specifications, which must be updated periodically. Formula specif-
ications for various diets are presented in Appendix F.
A closed-formula feed is one in which the feed formulation is not dis-
closed to the buyer. These feeds are sold by private manufacturers and are
also referred to as "brand name" or proprietary feeds. The advantages of
these feeds follow.
(1) The manufacturer is responsible for the formulation.
(2) The feed is generally a shelf item available at any time.
(3) The diet may be lower in cost due to large-quantity production and
the option of ingredient substitution.
(4) The manufacturer is liable for problems of poor production related to
the diet.
However, the buyer has no control of the feed quality and the content of
the feed largely is unknown. There may be unexpected variations between
batches of feed due to ingredient substitutions or formulation changes.
Handling and Storing Procedures
Formulated fish feeds contain high levels of protein and oil with little fiber.
These feeds are soft, fragile, and prone to rapid deterioration, especially if
optimum handling and storage are not provided.
Normally, the feeds are packaged in multiwalled paper bags to protect
the flavor, aroma, and color. The bags also reduce exposure to air, mois-
ture, and contamination. Plastic liners are used in bags for feeds containing
oil levels over 12% to eliminate oil seepage through the paper bags and to
retard moisture uptake.
Many fish producers receive their feed in bulk, storing it in large bulk
bins (Figure 74). Whether feed is in bags or bulk, proper handling and
storage procedures must be followed to protect the quality of the feed. Be-
cause fish feeds are very fragile in comparison to feeds for other animals,
up to 3% fines can be expected from normal handling. Excess fines are the
result of rough handling or poor physical characteristics of the feed. Do not
NUTRITION AND FEEDING
237
t ^
Figure 74. Bulk storage of pelleted fish feeds. Dust and "fines" are screened out
and collected (arrow), and can be repelleted. This type of storage is preferred to
bins that require angering the feed up into a truck, because angering breaks up
the pellets. (FWS photo.)
throw, walk on, or stand on bagged feed. A motorized belt- type bag con-
veyor causes the least damage to bagged feed. Close- spaced roller gravity
conveyers work well, but the wide-spaced rollers or wheel rollers used for
boxes are not suitable for bags and cause breakage of the granules and pel-
lets. For handling bulk feed, a bucket elevator is preferred, followed by air
lift systems; screw- type augers are least satisfactory.
If proper storage conditions are not maintained, fish feed will spoil ra-
pidly. During storage several factors can cause deterioration of the feed:
238 FISH HATCHF.RY MANAGEMENT
physical conditions (moisture, heat, light); oxidation; micro-organisms
(molds, bacteria, yeast); and enzymatic action.
Feed in bags or bulk should be stored in a cool, dry area. Low humidity
must be maintained because moisture enhances mold growth and attracts
insects. Molds, which grow when the moisture is 13% or above, cause feed
spoilage and may produce toxins. High temperatures may cause rancidity
of oils and deterioration of vitamins. Rancid oils can be toxic, may destroy
other nutrients, will cause off- flavor of the feed, and will produce an un-
desirable flavor in fish eating the feed. The storage area should be kept
clean and adequately ventilated. The stored feed should be protected from
rodents, insects, and contamination.
Ideal conditions for storing bagged dry feed include stacking the bags
not over ten high on pallets so the bags are 3 to 4 inches off the floor.
Space should be provided between the stacks for air circulation and rodent
control. Low relative humidity and low temperature in the storage area
reduce the rate of deterioration in feeds.
The recommended maximum storage time for dry pelleted feeds is
90-100 days. If less than optimal storage conditions exist, the storage time
should be shortened.
Bulk feed should be stored in clean bins free of contaminants or spoiled
feed. The bins must be in good condition to protect the feed from water
and weather elements. Bins located in shaded areas remain cooler. Bins can
be fitted with a screening unit on the discharge to remove dust and fines
from the pellets. In many cases the fines can be returned to the feed mill
for repelleting or be used to fertilize ponds.
Moist pellets should be stored in the freezer at temperatures below 0°F
until they are to be fed, then thawed just prior to feeding.
Feed Evaluation
The performance of feeds often is measured to evaluate or compare them.
The measurements used to evaluate feeds at production hatcheries are: (l)
fish growth (weight and length); (2) feed conversion; (3) cost to rear a
pound of fish; (4) protein and calories required to rear a pound of fish; and
(5) mortality and dietary deficiency symptoms.
Feeding
Feeding once was considered a simple task and was usually assigned to the
least experienced fish culturist. The chore consisted of merely feeding all
NUTRITION AND FEEDING 239
that the fish would consume, and then giving a little more to assure an
abundant supply. Even though given more feed than necessary, the fish
often were underfed because much of the feed was lost as it dispersed in
the water.
Nutrition is not solely a matter of feed composition. While it is true that
fish cannot grow if essential elements are lacking in the feed, it is equally
true that a feed cannot efficiently produce fish unless it can be consumed.
The conversion of food into fish flesh is the measure that commonly is used
to judge the efficiency of a feeding program in a hatchery. If the conver-
sion factor is to be regarded as a measure of efficiency, what can be done
to insure good food conversions?
The most common errors in hatcheries are either to overfeed or to un-
derfeed. Overfeeding is wasteful in terms of unconsumed food, but
underfeeding is just as wasteful in terms of lost production. To obtain max-
imum production and feed efficiency during a growing season, careful at-
tention must be given, on a daily basis, to the amount of food the fish are
receiving.
The quantity of food required is expressed conveniently in terms of per-
cent body weight per day. Because the metabolic rate per unit weight of
fish decreases as the fish grow larger, the percent of body weight to be fed
per day also decreases.
Feeding Guides for Salmonids
There are several methods for estimating feeding rates. Although differing
in complexity, all produce efficient results if properly used.
Table 25 may be used to estimate the amount of dry pelleted feed need-
ed for rainbow trout. For a given fish size, the amount of food increases
with increasing water temperature; for a given water temperature the
amount of feed decreases with increasing fish size.
Table 26 was developed by Oregon Fish and Wildlife Department for es-
timating the amount of moist feed to give to coldwater species. A higher
percent of body weight must be fed than in the case of dry pellets because
of the greater water content in moist feed.
Feeding tables provide a guide for determining the amount of feed to
give salmonids. In general, these yield good results. However, there are si-
tuations in which the amounts should be increased or reduced. When the
water begins to warm in the spring, the fish indicate an accelerated meta-
bolism by their increased activity and by the vigor with which they feed.
At this time of the year, when the photoperiod also is increasing, it is pos-
sible to feed in excess of (up to twice) the amounts in the tables and obtain
240 FISH HATCH F.RV MANAGEMENT
Table 25. recommended amounts of dry feed for rainbow trout per day,
OF different temperatures (or pounds feed per 100 POUNDS of fish), in
1976.)
NUMBER OE
FISH PER PUl Nl)
2,542-
304-
88.3-
37.8-
WATER
2,542 +
304
88.3
37.8
19.7
TEMPERATURE
(°F)
APPRO.XIMATE SIZE IN INCHES
UNDER 1
1-2
2-3
3-4
4-5
36
2.7
2.2
1.7
1.3
1.0
37
2.7
2.3
1.8
1.4
1.1
38
2.9
2.4
2.0
1.5
1.2
39
3.0
2.5
2.2
1.7
1.3
40
3.2
2.6
2.2
1.7
1.3
41
3.3
2.8
2.2
1.8
1.4
42
3.5
2.8
2.4
1.8
1.4
43
3.6
3.0
2.5
1.9
1.4
44
3.8
3.1
2.5
2.0
1.5
45
4.0
3.3
2.7
2.1
1.6
46
4.1
3.4
2.8
2.2
1.7
47
4.3
3.6
3.0
2.3
1.7
48
4.5
3.8
3.0
2.4
1.8
49
4.7
3.9
3.2
2.5
1.9
50
5.2
4.3
3.4
2.7
2.0
51
5.4
4.5
3.5
2.8
2.1
52
5.4
4.5
3.6
2.8
2.1
53
5.6
4.7
3.8
2.9
2.2
54
5.8
4.9
3.9
3.0
2.3
55
6.1
5.1
4.2
3.2
2.4
56
6.3
5.3
4.3
3.3
2.5
57
6.7
5.5
4.5
3.5
2.6
58
7.0
5.8
4.8
3.6
2.7
59
7.3
6.0
5.0
3.7
2.8
60
7.5
6.3
5.1
3.9
3.0
61
7.8
6.5
5.3
4.1
3.1
62
8.1
6.7
5.5
4.3
3.2
63
8.4
7.0
5.7
4.5
3.4
64
8.7
7.2
5.9
4.7
3.5
65
9.0
7.5
6.1
4.9
3.6
66
9.3
7.8
6.3
5.1
3.8
67
9.6
9.1
6.6
5.3
3.9
68
9.9
9.4
6.9
5.5
4.0
NUTRITION AND FP:F.DING
241
GIVEN AS PERCENT BODY WEIGHT. FOR DIFFERENT SIZE GROUPS HELD IN WATER
RELATION TO FISH SIZE AND WATER TEMPERATURE. (SOURCE: LEITRITZ AND LEWIS
NUMBER OK
FISH PER POUND
19.7-
11.6-
7.35-
4.94-
3.47-
Under
11.6
7.35
4.94
3.47
2.53
2.53
WATER
TEMPERATURE
APPRO.XIMATE SIZE IN INCHES
(°F)
5-6
6-7
7-8
8-9
9-10
10 +
0.8
0.7
0.6
0.5
0.5
0.4
36
0.9
0.7
0.6
0.5
0.5
0.4
37
0.9
0.8
0.7
0.6
0.5
0.5
38
0.9
0.8
0.7
0.6
0.6
0.5
39
1.0
0.9
0.8
0.7
0.6
0.5
40
1.1
0.9
0.8
0.7
0.6
0.5
41
1.2
0.9
0.8
0.7
0.6
0.5
42
1.2
1.0
0.9
0.8
0.7
0.6
43
1.3
I.O
0.9
0.8
0.8
0.6
44
1.3
1.1
1.0
0.9
0.8
0.7
45
1.4
1.2
1.0
0.9
0.8
0.7
46
1.4
1.2
1.0
0.9
0.8
0.7
47
1.5
1.3
1.1
1.0
0.9
0.8
48
1.5
1.3
1.1
1.0
0.9
0.8
49
1.7
1.4
1.2
1.1
1.0
0.9
50
1.7
1.5
1.3
1.1
1.0
0.9
51
1.7
1.5
1.3
1.1
1.0
0.9
52
1.8
1.5
1.3
1.1
1.1
1.0
53
1.9
1.6
1.4
1.3
1.1
1.0
54
2.0
1.6
1.4
1.3
1.1
1.0
55
2.0
1.7
1.5
1.3
1.2
1.0
56
2.1
1.8
1.5
1.4
1.2
1.1
57
2.2
1.9
1.6
1.4
1.3
1.2
58
2.3
1.9
1.7
1.5
1.3
1.2
59
2.4
2.0
1.7
1.5
1.4
1.3
60
2.5
2.0
1.8
1.6
1.4
1.3
61
2.6
2.1
1.8
1.6
1.5
1.4
62
2.7
2.1
1.9
1.7
1.5
1.4
63
2.8
2.2
1.9
1.7
1.6
1.5
64
2.9
2.2
2.0
1.8
1.6
1.5
65
3.0
2.3
2.0
1.8
1.6
1.6
66
3.1
2.4
2.1
1.9
1.7
1.6
67
3.2
2.5
2.1
2.0
1.8
1.7
68
242 KISH llAICHKRY MANAGEMENT
Table 26. recommended amounts of oregon moist pellet feed for sal-
weight PER DAY (pounds FEED PER 100 POUNDS OF FISH), RELATED TO FISH SIZE
unpublished.)
NUMBER OF
FISH PER
POUND
WATER
TEMPERATURE
START-
600-
420-
305-
230-
180-
140-
115-
(Fi
600
420
305
230
180
140
115
ilO
40
3.2
2.9
2.6
2.3
2.0
1.9
1.8
1.6
41
3.5
3.2
2.8
2.5
2.2
2.1
2.0
1.8
42
3.9
3.5
3.0
2.7
2.4
2.3
2.2
2.0
43
4.3
3.8
3.2
2.9
2.6
2.5
2.4
2.2
44
4.7
4.1
3.5
3.1
2.8
2.7
2.6
2.4
45
5.1
4.4
3.8
3.4
3.1
2.9
2.8
2.6
46
5.5
4.8
4.2
3.8
3.4
3.2
3.0
2.9
47
6.0
5.2
4.6
4.1
3.7
3.5
3.3
3.1
48
6.4
5.6
5.0
4.5
4.0
3.8
3.5
3.4
49
6.9
6.0
5.4
4.8
4.4
4.1
3.8
3.6
50
7.3
6.4
5.8
5.2
4.7
4.4
4.1
3.8
51
7.7
6.7
6.1
5.5
5.0
4.7
4.3
4.0
52
8.0
7.0
6.4
5.8
5.2
4.9
4.5
4.1
53
8.3
7.3
6.6
6.0
5.4
5.0
4.7
4.3
54
8.6
7.6
6.8
6.2
5.6
5.2
4.8
4.4
55
8.9
7.9
7.0
6.4
5.8
5.3
5.0
4.6
56
9.3
8.2
7.3
6.7
6.1
5.5
5.2
4.8
57
9.6
8.5
7.6
6.9
6.3
5.7
5.4
5.0
58
9.9
8.8
7.8
7.1
6.5
5.9
5.6
5.2
59
10.2
9.1
8.1
7.3
6.7
6.1
5.8
5.4
60
10.5
9.3
8.3
7.5
6.9
6,3
5.9
5.5
excellent conversions and weight gains by the fish. Taking advantage of
such situations increases the efficiency and production of a hatchery. By
the same reasoning, as the temperature starts to fall, metabolism is
depressed and less food than the amounts listed in the tables still will
result in maximum efficiency of food conversion.
As mentioned in Chapter 2, salmonids increase their length at a constant
rate during their first 1^ years or so of life, so long as they are raised at a
constant temperature (see page 6l). The rate of length increase (inches per
day or month), of course, varies with temperature. For a given temperature,
the amount of daily feed needed can be calculated from knowledge of fish
growth and conversion at that temperature from the following formula:
, , , ., Conversion x 3 x A Z, x IQQ
rercent body weight to feed daily =
NUTRITION AND FEEDING 243
MONIDS (BASED ON COHO SALMON) FED TWICE EACH DAY. GIVEN AS PERCENT BODY
AND WATER TEMPERATURE. (SOURCE; OREGON FISH AND WILDLIFE DEPARTMENT,
NUMBER OF FISH PER POUND
WATER
90-
75-
65-
55- 45- 39-
34-
29-
TEMPERATURE
75
65
55
45 39 34
29
25.5
(°F)
1.5
1.3
1.2
1.1 1.0 1.0
0.9
0.9
40
1.7
1.5
1.4
1.3 1.2 1.1
I.O
0.9
41
1.9
1.7
1.6
1.4 1.3 1.2
I.l
1.0
42
2.1
1.9
1.8
1.6 1.5 1.4
1.3
1.2
43
2.2
2.1
2.0
1.8 1.7 1.6
1.5
1.4
44
2.5
2.3
2.2
2.0 1.9 1.8
1.7
1.6
45
2.7
2.5
2.3
2.2 2.1 2.0
1 .9
1.8
46
2.9
2.7
2.5
2.4 2.3 2.1
2.0
1.9
47
3.1
2.8
2.7
2.5 2.4 2.3
2.2
2.1
48
3.3
3.0
2.8
2.7 2.6 2.5
2.3
2.2
49
3.5
3.2
3.0
2.9 2.8 2.7
2.5
2.4
50
3.7
3.3
3.2
3.0 2.9 2.8
2.7
2.6
51
3.8
3.5
3.3
3.2 3.1 3.0
2.8
2.7
52
4.0
3.6
3.5
3.4 3.2 3.1
2.9
2.8
53
4.1
3.8
3.6
3.5 3.4 3.2
3.1
3.0
54
4.3
3.9
3.8
3.7 3.5 3.4
3.2
3.1
55
4.4
4.1
3.9
3.8 3.6 3.5
3.4
3.2
56
4.6
4.2
4.1
3.9 3.7 3.6
3.5
3.3
57
4.8
4.4
4.2
4.1 3.9 3.8
3.6
3.4
58
5.0
4.5
4.4
4.2 4.0 3.9
3.7
3.5
59
5.1
4.7
4.5
4.3 4.1 4.0
3.8
3.6
60
Here, A/, equals the daily increase in length in inches, and L equals the
length in inches at the present time.
To use this equation, an average monthly growth in inches is established
from previous years' records for the same temperature. The daily increase
in length is determined by dividing the average monthly growth by the
number of days in the month. The daily growth then can be used to pro-
ject fish size to any date needed. An expected feed conversion is obtained
from previous hatchery records or calculated from the caloric content of
the feed (see page 225).
For example, on April 13, we have 210,000 fish on hand. Their feeding
rate was last established on April I, when fish were 20 pounds per 1,000
fish, or 3.68 inches. We need to adjust the feeding rate again, knowing
from past records that at this temperature the average length increase per
244
FISH hatchp:ry management
Table 26. continued.
NUMBER OF FISH PER POUND
WATER
11.0
TEMPERATURE
25.5-
22.5-
20.0- 18.0- 16.0-
14.0-
13.0-
12.0-
AND
("F)
22.5
20.0
18.0 16.0 14.0
13.0
12.0
11.0
FEWER
40
0.8
0.8
0.7 0.7 0.6
0.6
0.5
0.5
0.4
41
0.9
0.8
0.8 0.7 0.7
0.6
0.6
0.5
0.5
42
1.0
0.9
0.8 0.8 0.7
0.7
0.6
0.6
0.5
43
1.1
1.1
0.9 0.9 0.8
0.7
0.7
0.6
0.6
44
1.3
1.2
1.1 1.0 0.9
0.8
0.7
0.7
0.6
45
1.5
1.4
1.3 1.2 1.1
1.0
0.9
0.8
0.8
46
1.6
1.5
1.4 1.3 1.2
1.1
1.0
0.9
0.8
47
1.8
1.7
1.6 1.5 1.3
1.2
1.1
1.0
0.9
48
1.9
1.8
1.7 1.6 1.5
1.4
1.3
1.1
1.0
49
2.1
2.0
1.9 1.8 1.6
1.5
1.4
1.3
1.1
50
2.3
2.1
2.0 1.9 1.8
1.7
1.5
1.4
1.3
51
2.4
2.3
2.2 2.0 1.9
1.8
1.6
1.5
1.4
52
2.6
2.4
2.3 2.2 2.0
1.9
1.7
1.6
1.5
53
2.7
2.6
2.4 2.3 2.1
2.0
1.8
1.7
1.6
54
2.8
2.7
2.5 2.4 2.2
2.1
1.9
1.8
1.7
55
2.9
2.8
2.6 2.5 2.3
2.2
2.0
1.9
1.8
56
3.1
2.9
2.8 2.6 2.4
2.3
2.1
2.0
1.9
57
3.2
3.0
2.9 2.7 2.5
2.4
2.2
2.1
2.0
58
3.3
3.1
3.0 2.8 2.6
2.5
2.3
2.2
2.1
59
3.4
3.2
3.1 2.9 2.7
2.6
2.4
2.3
2.2
60
3.5
3.3
3.2 3.0 2.8
2.7
2.5
2.4
2.3
day (AL) is 0.019 inches per day during April, and expected feed conver-
sion is 1.2 pounds of feed per pound of growth. What is our new feeding
rate?
Length, April 1st
Growth, 13 days x 0.019
Length, April 13th
210,000 fish X 24.3 pounds/1,000
3x 1.2 X 0.019 X 100
% to feed daily
0.017X5,103 pounds
3.93
3.68 inches (20 pounds/1,000)
0.25
3.93 inches (24.3 pounds/1,000)
5,103 pounds of fish, April 13th
1.7% (0.017)
87 pounds of feed required
daily, April 13th, for
210,000 fish.
NUTRITION AND FEEDING 245
The proper use of this method helps assure optimum feeding levels. It
determines the feeding level regardless of the caloric content of the feed,
because this is considered in the feed conversion.
When the water temperature, diet, and species remain constant, all
numerator factors in the feeding formula remain constant. Multiplication of
the numerator factors establishes a Hatchery Constant (HC):
HC = 3x conversion x AI x 100.
The percent of body weight to feed daily for any length of fish can be ob-
tained by dividing the Hatchery Constant by the length of fish {L) in
inches.
FfC
Percent of body weight feed daily =
The Hatchery Constant {HC) is used in the following example to calculate
feed requirements. We must calculate the amount of feed required on April
10th for 20,000 fish averaging 100 pounds per 1,000 fish or 6.3 inches on
April 1st. The expected growth during April is 0.60 inches and the feed
conversion is 1.2 pounds of feed per pound of growth.
Length increase per day (AZ-) = 0.60 inches
Length, April 1st = 6.30 inches (lOO pounds/1,000 fish)
Growth, 10 days X 0.020 = 0.20
Length, April 10th = 6.50 inches (llO pounds/1,000 fish)
20,000 fish X 110 pounds/1,000 = 2,200 pounds offish April 10th
//C= 3 X 1.2X0.020 X 100 =7.2
HC 7 2
Percent body weight to feed = = — ' — = 1.1% (O.Oll)
L 6.50
2,200 pounds fish x 0.011 = 24.2 pounds of feed required on
April 10th for the 20,000 fish.
The above method of calculating feed can be used to project the amount
of feed required for a raceway or pond for any period of time. Many sta-
tions use this method to set up feeding programs for the coming month.
246 FISH HATCHF.RY MANAGEMENT
A simplified method to calculate the amount of daily feed is based on
monthly percent gain in fish weight. In conjunction with past records that
establish both growth in inches and conversion, Table 27 can be used to
project daily feed requirements on a monthly basis. To calculate the
amount of feed required for a one month period two values must be deter-
mined: (l) the gain in weight for the month; and (2) the percent gain for
the month.
(1) Gain in weight = weight of lot on hand at the end of the
month minus the weight of lot on
hand the start of the month.
.s „ monthly gain in weight x 100
(2) Percent gain = f-^ ^ ;
weight at start of month
The feed requirement during the month of July for 100,000 fish averag-
ing 100 pounds per 1,000 fish, or 6.30 inches, on July 1st can be calculated
in the following manner. The expected growth for the month of July is
0.60 inches and the feed conversion is 1.3 pounds of feed per pound of
growth.
Length, July 1st 6.30 inches (lOO pounds/1,000 fish)
Expected growth, July 0.60
Length, July 31st 6.90 inches (132 pounds/1,000 fish)
100,000 fish X 100 pounds/1,000 = 10,000 pounds July 1st
100,000 fish X 132 pounds/1,000 = 13,200 pounds July 31st
Expected gain in fish weight, July = 3,200 pounds
The expected gain in fish weight, multiplied by the food conversion
determines the required pounds of feed for the month.
Pounds of feed required for July = 3,200 pounds gain x 1.3 conversion
= 4,160 pounds
„ 3,200 pounds gain „„„,
Percent gain= ■ ^ , ^ , ^ , = 32%
10,000 pounds on hand July 1
Table 27 shows that at the 30% rate of gain, fish should be fed 2.91% of
the monthly feed total per day during the first 8 days; 3.13% during the
second 8 days; 3.34% during the third 8 days; and 3.57% per day the
remaining days of the month.
NUTRITION AND FEEDING
247
Table 27. percent of total monthly feed to give trout daily for dif-
ferent PERCENT GAINS, IF FEED IS TO BE ADJUSTED FOUR TIMES PER MONTH.
(SOURCE: FREEMAN ET AL. 1967.)
EXPECTED
DAYS
MDNTHI Y
ivi yj 1^ 1 ri Li I
PERCENT WEIGHT
1-8
9-16
17-24
25-31
GAIN
(8 DAYS)
(8 DAYS)
(8 DAYS)
(7 DAYS)
10
3.13
3.13
3.25
3.29
20
3.00
3.19
3.31
3.43
30
2.91
3.13
3.34
3.57
40
2.85
3.09
3.38
3.64
50
2.75
3.08
3.40
3.74
60
2.69
3.04
3.36
3.90
70
2.63
3.00
3.45
3.90
80
2..56
2.96
3.48
4.00
90
2.50
2.96
3.49
4.06
100
2.45
2.93
3.50
4.14
110
2.40
2.91
3.51
4.20
120
2.35
2.88
3.53
4.29
130
2.31
2.85
3.55
4.33
140
2.26
2.84
3.56
4.39
150
2.23
2.81
3.59
4.56
160
2.19
2.80
3.58
4.50
170
2.15
2.78
3.59
4.56
180
2.11
2.75
3.60
4.61
190
2.08
2.74
3.61
4.66
200
2.05
2.71
3.63
4.70
210
2.01
2.70
3.63
4.76
220
1.99
2.69
3.63
4.80
230
1.96
2.68
3.63
4.84
240
1.93
2.66
3.64
4.89
250
1.91
2.63
3.65
4.93
260
1.89
2.63
3.65
4.96
270
1.86
2.61
3.65
5.00
280
1.84
2.60
3.65
5.04
290
1.81
2.58
3.66
5.09
300
1.79
2.56
3.68
5.12
248 FISH HATCHERY MANAGEMENT
The amounts to feed would be:
July 1-8; 2.91% X 4,160= 121 pounds/day
July 9-16; 3.13% x 4,160= 130 pounds/day
July 17-24; 3.34% x 4,160 = 139 pounds/day
July 25-31; 3.57% x 4,160= 149 pounds/day
Under normal conditions, adjusting feeding levels four times during the
month should prevent over- or under- feeding. The advantage of this
method is its simplicity.
Feeding Guides for Coolwater Fishes
For many years, fish culture was classified into two major groups. "Coldwa-
ter" hatcheries cultured trout and salmon, and "warmwater" hatcheries cul-
tured any fish not a salmonid. Muskellunge, northern pike, walleye, and
yellow perch prefer temperatures warmer than those suited for trout, but
colder than those water temperatures most favorable for bass and catfish.
The term "coolwater species" has gained general acceptance in referring to
this intermediate group.
Pond culture traditionally has been used to rear coolwater species. This
method of extensive culture involves providing sufficient quantities of
micro-organisms and plankton as natural foods through pond fertilization
programs. If larger fingerlings are to be reared the fry are transferred, when
they reach approximately 1.5 inches in length, to growing ponds where
minnows are provided for food. A major problem in extensive pond culture
is that the fish culturist is unable to control the food supply, diseases, or
other factors. Many times it is extremely difficult to determine the health
and growth of fish in a pond.
In recent years the intensive culture of coolwater fishes in tanks has
been successful. Zooplankton, primarily Daphnia, are cultured in ponds and
each day a supply is placed in the rearing tanks. Fish reared in tanks can
be observed readily and treated for parasites. Fish also can be graded to
size to minimize cannibalism and to provide an accurate inventory.
Pennsylvania fisheries workers successfully fed a diet of lOO'Si Daphnia to
muskellunge for up to 5 months with no significant mortality, but after the
fish attained a length of approximately 2 inches the Daphnia diet did not
appear adequate.
Fisheries workers in Pennsylvania and Michigan have reared coolwater
fishes successfully on dry feed. The W-7 dry feed formulated by the Unit-
ed States Fish and Wildlife Service specifically for coolwater fishes has
given the best results. (See Appendix F for diet formulation.) Starter feed
NUTRITION AND FEEDING 249
is distributed in the trough by automatic feeders set to feed at 5-minute in-
tervals from dawn to dusk (Figures 75 and 76).
Coolwater fish will not pick food pellets off the bottom of the tank so it
is necessary to continually present small amounts of feed with an automatic
feeder. In some situations, coolwater fry are started on brine shrimp and
then converted to dry feed. Pennsylvania workers report that muskellunge
are extremely difficult to rear on artificial feeds. However, the tiger muskie
(northern pike male x muskellunge females) adapts readily to dry feeds.
Northern pike will accept a dry feed and also adapt to culture in tanks.
Walleye fry have been observed feeding on the W-7 diet, but did not
survive well on it. Anemia developed in advanced fingerlings, indicating a
deficiency of some nutrient.
Tiger muskie fry aggressively feed on dry feeds. Fry often follow a food
particle through the entire water column before striking it. Hand-feeding
or human presence at the trough does not disrupt feeding activity. How-
ever, when the fish attain a length of 5-6 inches, human presence next to a
trough or tank can disrupt feeding activity completely. Cannibalism gen-
erally is a problem only during the first 10-12 days after initial feeding,
when the fish are less than 2-3 inches in length. The removal of weak and
dying fry greatly reduces cannibalism.
The methods developed for estimating feeding rates for salmonids can be
adapted for use with coolwater species. Michigan workers use a Hatchery
Constant of 40 to calculate feeding rates for tiger muskellunge raised in
70°F water.
Feeding Guides for Warmwater Fishes
CATFISH
Newly hatched catfish fry live on nutrients from the yolk sac for 3-10 days,
depending upon water temperatures, after which they accept food from a
variety of sources. Generally, feed for trough- feeding of fry should be small
in particle size, high in animal protein, and high in fat. Salmonid rations
are well suited for this purpose. Palatability of lower-quality feed is
enhanced by having a high percentage of fish meal, fish oil, chopped liver,
egg yolk, or other ingredients that serve as attractants.
Overfeeding in the troughs should be avoided and adequate water flows
must be maintained to avoid fouling the water. The fry should be
transferred to ponds with high zooplankton densities as soon as possible to
efficiently utilize the natural food source.
Supplemental feeding of fry in ponds should begin soon after stocking. A
250
FISH HATCHERY MANAGEMENT
Figure 75. In recent years, intensive culture of coolwater fishes in tanks has
been successful. The tanks are covered partially with black plastic to avoid dis-
turbing the fish. Automatic feeders provide a continuous supply of dry feed from
dawn to dusk at 5-minute intervals. (Courtesy Pennsylvania Fish Commission.)
Figure 76. Walleye fingerlings are reared successfully in tanks, with automatic
feeders to dispense dry feed. The fish first are started feeding on live brine
shrimp or zooplankton and then are converted to dry feed. (Courtesy Pennsyl-
vania Fish Commission.)
NUTRITION AND FEEDING 251
high-quality, 36"o protein catfish feed (Appendix F) is an adequate supple-
mental feed for fry and small fingerlings as they will get a large portion of
their nutrients from natural pond organisms.
Feed first should be pelleted or extruded before it is reduced to smaller
particle sizes. Fat sprayed onto the feed after processing reduces the loss of
water-soluble vitamins.
Growth of channel catfish fingerlings is similar with either sinking or
floating pellets, provided that the nutrient contents are the same. Floating
feeds are a valuable management tool to help determine the effects of low
dissolved oxygen content and low or high water temperature on feeding,
general vigor, and health of fish during the feeding season. It also is help-
ful in determining amounts of feed to give fish in special culture systems
such as cage feeding, raceway feeding, and ponds having abundant rooted
vegetation.
Table 28 presents a feeding guide for channel catfish in ponds, and
Table 29 offers one for catfish in raceways. The pond feed is a supplemen-
tal, 36"o protein diet; that for raceways is a complete formulation. See Ap-
pendix F for ingredients.
Low dissolved oxygen levels depress feeding activity of catfish, and fish
should not be fed in early morning for this reason. Neither should they be
fed late in the day because their increased metabolic oxygen requirement
during active feeding and digestion will coincide with the period of low
dissolved oxygen in the pond during the night and early morning. The
best times to feed are between mid- morning and mid- afternoon.
The optimal temperature for catfish growth is approximately 85°F; as
temperature decreases, food consumption decreases proportionally. Gen-
erally, catfish do not feed consistently in ponds when the water tempera-
ture drops below 60°F; below 50°F they will feed, but at greatly reduced
levels and frequencies. Below 60°F, the efficiency of digestion and metabo-
lism drops markedly.
During colder months, feed catfish only on warm days and only what the
fish will consume readily. A recommended guide for winter feeding of cat-
fish in ponds is to feed the fish 0.75-1% of their estimated weight daily
only when the water temperature is above 54°F, and not to feed at lower
temperatures.
There are no reliable data on the best feeds for catfish in the winter.
Catfish do not respond as well to high- protein diets in cool weather as in
warm weather. This may indicate that lower- protein feeds (below 32%) are
more economical in cold water. Digestibility of carbohydrates is suppressed
even more at low temperatures than the digestibility of proteins and fats,
indicating that high-grain feeds are not utilized by catfish in cool weather.
Therefore, winter rations should contain less protein and carbohydrates
than those fed during the summer.
WATER
FISH
PERCENT BODY
TEMPERATURE
SIZE
WEIGHT TO FEED
(T)
(POUNDS)
DAILY
()8
0.04
2.0
72
0.06
2.5
78
0.11
2.8
80
0.16
3.0
83
0.21
3.0
84
0.28
3.0
85
0.35
2.8
85
0.42
2.5
86
0.60
2.2
86
0.75
1.8
83
0.89
1.6
79
1.01
1.4
73
1.10
1.1
252 fish hatchery management
Table 28. typical spring-summerfall supplemental feeding schedule for
channel catfish in ponds, based on stocking rates of 2,000-3,000 fish per
acre.'' (SOURCE: STICKNEY AND LOVELL 1977.)
DATE
April 15
April 30
May 15
May 30
June 15
June 30
July 15
July 30
August 15
August 30
September 15
September 30
October 15
The feed allowances are based on rations containing 36"ii protein and approximately 2.88
kcalories of digestible energy per gram of protein. If feeds of lower protein and energy con-
centrations are used, daily allowances should be increased proportionally.
Fish are fed 6 days per week.
LARGEMOUTH AND SMALLMOUTH BASS
As long ago as 1924, fish culturists attempted to increase yield and survival
of smallmouth bass by providing a supplemental feed of zooplankton.
Ground fresh- fish flesh also was successfully used but costs were prohibi-
tive. These early attempts were discouraging but culturists have continued
to rear bass fry to fingerling size on naturally occurring foods in fertilized
Table 29. feeding rates (percent body weight fed per day) for channel
CATFISH fed a COMPLETE FEED (25% FLOATING, 75% SINKING FEED) IN RACEWAYS.
(SOURCE: KRAMER, CHIN AND MAYO 1976.)
SIZE (INCHES)
1-2 2-5 5-1-
WEIGHT (POUNDS)
WATER
TEMPERATURE 0.001-0.004 0.004-0.04 0.04
Below 55°F 1% 1% 1%
At 55°F 3% 2% 1.5%
Above 55T 5% 3% 2%
NUTRITION AND FEEDING 253
earthen ponds. This method generally results in low yields and is
unpredictable.
Interest in supplemental feeding of bass has been renewed in recent
years due to successful experimental use of formulated pelleted feeds with
largemouth bass fingerlings. Attempts to train swim- up bass fry to feed
exclusively on formulated feeds or ground fish flesh have been unsuccess-
ful, despite the use of a variety of training techniques. The best success in
supplemental feeding has been obtained by rearing bass fry on natural feed
to an average length of 2 inches in earthen ponds before they are put on
an intensive training program to accept formulated feed. A moist feed, such
as the Oregon moist pellet, or a quality dry feed such as the W-7 coolwa-
ter fish feed may be employed. The success of this program has been corre-
lated with initial fingerling size, coupled with sound management practices.
The following steps are suggested for an intensive feeding program with
bass:
By conventional techniques, rear bass fingerlings on natural feed in
earthen ponds to an average total length of 2.0 inches. Harvest and move
fish to raceways and tanks. Grade fish carefully to eliminate "cannibals,"
because uniformly sized fingerlings are needed. Stock the tanks at 0.15-0.4
pounds per cubic foot of water (3,000—7,500 fingerlings per tank).
Treat the fish prophylactically with 4 parts per million acriflavine for 4
hours. Heavy parasite infestations may require treatment with formalin or a
similar chemical. Provide ample aeration during treatment.
Begin feeding a -j^-inch feed granule the following day. Feed at 1- to 2-
hour intervals, five or more times daily. Feed slowly and carefully because
bass will not pick up sunken food particles from the bottom of the tank.
Automatic feeders are excellent for this purpose.
If fish are reluctant to feed, supplement the granule with ground fresh or
frozen fish.
Clean tanks twice daily and remove all dead fish daily.
Begin feeding a ^-inch granule as soon as the fingerlings are feeding
well and able to ingest it.
Perform grading as needed to reduce cannibalism.
After 10-14 days, 65-75% of the fish should be on feed. Reports of
90-95% success are not unusual. The fish should double their weight dur-
ing this 2-week period.
At 2-3 weeks, remove all nonfeeders and move the fish to ponds or race-
ways. Stock ponds at 10,000 per acre. Feed and maintain fish in a res-
tricted area for 2-3 days, then release them to the remainder of the pond.
Grow the bass to 4 inches on a ^-inch pellet. Table 30 presents a sug-
gested feeding guide that can be used when formulated dry feeds are given
to bass fingerlings in raceways or ponds.
254 fish hatciif.ry management
Table 30. bass keeu chart: percent body weight fed per day in raceway
CULTURE for FORMULATED DRY FEEDS.'^ (SOURCE: KRAMER, CHIN AND MAYO 197(i.)
SIZE (INCHES)
1-2 2-3 3-4 4-5 5+
WEIGHT (POUNDS)
WATER
TEMPERATURE
0.002
0.002-.015
0.015-0.03
0.03-0.06
0.06
fi5°F
4.4'^
4.0');,
3.2%
2.4%
1.6%
70°F
5.5'!i,
4.7%
2.5%
2.2"'(,
2.0'!{.
75°F
6.0%
5.0'^i,
4.0%
s.o"-;.
2.0"/,
.80°F
6.5%
5.4%
4.3%
3.3'!';,
2.2%
85°F
7.1%
5.9'},,
4.7%
3.5'!,,
2.4"/;,
90°F
7.5'!^,
6.3%
5.1%
3.9%
2.7%
Feedings
4
4
2
1
1
per
hour
Winter feeding rate: l",, of body weight per day.
STRIPED BASS
Striped bass fingerlings often are fed supplemental diets in earthen ponds
when zooplankton blooms have deteriorated or larger fish are desired. The
fingerlings are fed a high- protein (40-50%) salmonid type of formulated
feed at the rate of 5.0 pounds/acre per day. This is increased gradually to a
maximum of 20.0 pounds/acre per day by the time of harvest. The fish are
fed 2-6 times daily.
When striped bass fingerlings reach a length of approximately 1.5 inches
they will accept salmonid- type feeds readily. Good success can be antici-
pated when a training program is followed, such as that described for
largemouth and smallmouth bass. Striped bass fingerlings can be grown to
advanced sizes in ponds, cages, or raceways.
Attempts to rear swim-up fry to fingerling size on brine shrimp and for-
mulated feeds under intensive cultural conditions have been relatively
unsuccessful.
Time of Initial Feeding
There is considerable difference of opinion among fish culturists as to when
fry should receive their initial feeding. The most common practice is to
offer food when the fry swim up. Swim- up occurs when the fry have ab-
sorbed enough of their yolk sac to enable them to rise from the bottom of
NUTRITION AND FEEDING 255
the trough and maintain a position in the water column. A considerable
amount of work has been conducted to determine when various salmonid
fry first take food. Brown trout begin feeding food approximately 31 days
after hatching in 52°F water, while food was first found in the stomachs of
rainbow trout fry 21 days after hatching in 50°F water.
The upper alimentary tract of rainbow trout fry remains closed by a tis-
sue plug until several days before swim- up. Thus, feeding of rainbow trout
fry before swim- up is useless. Some fish culturists have observed higher
mortality in brook trout fed early than in those deprived of food for up to
5 days after swim-up.
Yolk absorption is a useful visual guide to determine the initial feeding
of most species of fish. Most studies reported in the literature (Table 3l)
indicate that early feeding of fry during swim-up does not provide them
with any advantage over fry that are fed later, after the yolk sac has been
absorbed. Many culturists start feeding when 50% of the fry are swimming
up because if fry are denied food much beyond yolk-sac absorption, some
will refuse to feed. No doubt, starvation from a lack of food will lead to a
weakened fry that cannot feed even when food is abundant.
It is apparent that the initial feeding time for warmwater fishes is much
more critical than for coldwater species because metabolic rates are much
higher at warmer water temperatures. This will lead to more rapid yolk ab-
sorption and a need for fish to be introduced to feed at an earlier date.
Feeding Frequency
The frequency at which fish should be fed is governed by the size of the
fish and how rapidly they consume the feed. When fish are started on feed,
it is desirable to give small amounts of small- sized particles at frequent in-
tervals.
Several factors influence how quickly fish consume feed. The type of
feed, the way it is introduced, and the type of trough or pond in which it
is fed all will affect the rate of consumption. Feeds that are heavier than
water must be fed with more care than those that float. Once a sinking
feed reaches the bottom many fish will ignore it. To avoid their prolonged
exposure to water, sinking feeds should be fed slowly and at greater fre-
quency.
Trout and salmon generally are fed small amounts at hourly intervals
throughout an 8- hour day when they first start to feed. Some fish culturists
feed fry at half- hourly intervals and gradually reduce the number of feed-
ings as the fish increase in length. The general practice has been to feed
trout three times a day until they are 5 inches long (20/pound). Larger
trout are fed twice daily and broodfish are usually fed once each day.
256
FISH HATCHERY MANAGEMENT
Table 31. initial feeding times for various species of fish.
INITIAL
WATER
FEEDING
TEMPER-
(DAYS post-
ATURE
SPECIES
hatching)
rF)
Brook trout
23-35"
52
REMARKS
Brown trout
Cutthroat trout
Rainbow trout
Channel catfish
Tiger muskie
Northern pike,
walleye,
muskellunge
31
23
20-30"
at swim-up
at swim-up
Several fry had food in gut on
23rd day; all fry were feeding
on the 35th day.
52 Evidence of food in stomach on
27th day; all fry feeding on 31st
day.
47-51 Evidence of food in stomach on
14th day; all fry feeding on 23rd
day.
47 Evidence of food in stomach on
21st day (16 days at 50°F).
— 5 to 10 days after hatching,
depending on water tempera-
ture.
68 Food presented at swim- up; most
of yolk sac absorbed after 8
days.
50-70 Food presented at swim-up, up to
12 days post-hatching.
Various reports include a range of initial feeding times and water temperatures. It is
important to note that in some instances, evidence of food in the stomach did not occur until
several days after swim- up.
Table 32 presents feeding frequencies for trout and Pacific salmon finger-
lings.
Successful feeding of dry feeds to coolwater fishes, such as northern pike
and tiger muskie, requires initial feeding of fry at 5- minute intervals, at
10-minute intervals when fry are 2 inches long, and at 15-minute intervals
when they are 4 inches long, from automatic feeders during the daylight
hours.
A rule of thumb used by some fish culturists is to feed iJo of the body
weight per feeding. Therefore, if the fish are being fed at a rate of 10% of
nutrition and feeding 257
Table 32. suggested feeding frequencies for salmonids. (source; washing-
ton DEPARTMENT OF FISHERIES, UNPUBLISHED.)
FiSH SIZE (NUMBER/POUND)
SPECIES 1,500 1,000 750 500 250 125 75 30 10-LARGER
TIMES PER DAY
Coho salmon
9
8
7
6
5
3
3
Fall chinook
salmon
8
8
8
6
5
4
3
Trout
8
8
6
6
6
4
4
body weight, they would receive 10 feedings per day; if they receive T'o of
body weight in feed per day it would be fed in one feeding.
Channel catfish reared in raceways produce more gain when fed twice
daily than when they are fed only once daily. In some situations, more
than two feedings per day will not improve the feed consumption or
growth rate in pond fed catfish.
The following statements relate to feeding frequency:
The feeding frequency does not significantly influence the mortality of
fry once they pass the initial feeding stage.
Frequently fed fingerlings utilize their feed more efficiently than those
fed less frequently, resulting in better feed conversion.
Frequent feeding of fingerlings reduces starvation and stunting of the
small fish in a group. Generally, more frequent feeding results in greater
uniformity in fish size.
The accumulation of waste feed on the bottom of a rearing unit due to
the infrequent feeding of large amounts of feed is a principal factor caus-
ing inefficient utilization of feed.
When uneaten feed lies on the bottom of the tank, water-soluble nu-
trients are leached out, resulting in poor utilization of the feed.
In general, the number of feedings per day should be greater for dry
feed than for soft moist feeds.
A rule of thumb is that 90% of the feed should be eaten in 15 minutes or
less.
Feed Sizes
The size of feed particles is critical in the feeding of fish. If particles are
too large, the fish will not be able to ingest them until the water disin-
tegrates the feed to an acceptable size. When this occurs, nutrients leach
out of the pellet, wasting feed and possibly polluting the water. When the
258
FISH HATCHERY MANAGEMENT
Table 33. recommended sizes for dry formulated feeds given to trout.
GRANULE OR
PELLET
size"
FISH SIZE
us
WEIGHT
NUMBER
SCREEN
PER
PER
SIZE
THOUSAND
POUND
30-40
less than 0.5
2,000+
20-30
0.5-1.25
2,000-800
16-20
1.2.5-4.0
800-250
10-16
4.0-10.0
250-100
6-10
10.0-33.3
100-30
33.3-100.0
30-10
100.0+
10 and fewer
Starter granule
No. 1 granule
No. 2 granule
No. 3 granule
No. 4 granule
— " pellets
_L"
16
pellets
'^Feed sizes — US Fish and Wildlife Service Trout Feed Contract Specifications, Spearfish
Fisheries Center, Spearfish, South Dakota 57783.
particles are too small, the feed dissolves in water and is lost. It is impor-
tant for maximum feed efficiency to provide an acceptable range of feed
sizes for fish during their different growth stages.
Granules or crumbles are made in a range of sizes for fingerlings of dif-
ferent weights (Tables 33-35). Hard pellets are cracked into granules and
the different particle sizes are separated by screening.
When the fish are being shifted from a small granule to a larger size, the
change should be gradual rather than abrupt. The change may be made ei-
ther by mixing the two sizes together and feeding them at the same time,
or by feeding the two sizes separately, starting with a few feedings of the
larger size each day and gradually increasing the frequency until only the
larger particle is fed.
Table 34. recommended sizes for abernathy dry pelleted feed given to
PACIFIC salmon. (SOURCE: L.G. FOWLER, UNPUBLISHED.)
GRANULE OR PELLET SIZE
FISH SIZE (NUMBER PER POUND)
Starter granule
-!--inch granule
- — inch granule
^-inch granule
— inch granule
—-inch pellet
32 ^
—-inch pellet
—-inch pellet
16 ^
800 +
800-500
500-200
200-100
100-75
75-.50
.50-20
Less than 20
NUTRITION AND FEEDING
259
Table 35. optimum feed particle sizes for small channel catfish, crum-
bles OR pellets should be kept to the maximum size that the fish can
ingest. (SOURCE; STICKNEY AND LOVELL 1977.)
CRUMBLE OR PELLET SIZE
FISH SIZE (INCHES)
00 Crumble (starter)
No. 1 crumble
No. 3 crumble
^-inch pellet
Swim-up fry
0.5-1.5
1.5-2.5
2.5-6
Feeding Methods
Automatic feeders with timing devices can be used to reduce labor costs
and to provide fish with small quantities of feed at frequent intervals. Self-
feeders or demand feeders are especially useful in feeding large channel
catfish, particularly during winter months when the fish fed less actively.
Automatic feeders have become quite popular for feeding salmonids and
coolwater fishes. However, most pond- reared warmwater fishes are fed by
hand. Mobile blower- type feeders often are used to feed warmwater fish in
large ponds (Figure 77). One study determined that more frequent feeding
with automatic feeders did not increase growth of channel catfish over those
hand-fed twice per day. Because catfish have relatively large stomachs, they
may consume enough food for maximum growth in two feedings.
FIGURE 77.
pond.
Bulk- feeding of formulated pelleted feed to catfish in a large rearing
260 FISH HATCHERY MANAGEMENT
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NUTRITION AND FEEDING 261
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262 FISH HATCHERY MANAGEMENT
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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
•'^.^^
*
#
^%^
%
*
#
# ■
V*
.^
Figure 103. Sanguinkola davisi, 2,000x magnification. (Courtesy G. L. Hoff-
man, Fish Farming Experimental Station, Stuttgart, Arkansas.)
334
FISH HATCHERY MANAGEMENT
ARGULUS
Argulus spp. have been given the common name of fish lice because of their
ability to creep about over the surface of the fish. On first glance, they
look like a scale but, on closer examination, are seen to be saucer shaped
and flattened against the side of the fish. They have jointed legs and two
large sucking discs for attachment that may give them the appearance of
having large eyes (Figure 104). Argulids have an oral sting that pierces the
skin of the host fish. They then inject a cytolytic substance, and feed on
blood. If these organisms become abundant, even large fish may be killed.
Masoten (registered by the Food and Drug Administration) at 0.25 part per
million active is used for the treatment of Argulus in ponds. Complete dry-
ing of rearing units will kill eggs, larvae, and adults.
LERNAEA
Lernaea spp. are most commonly found on warmwater fish. However, one
species, L. elegans, lacks host specificity and even attacks frogs and
salamanders. Heavy infestations have caused massive mortality in carp and
goldfish populations. The parasite penetrates beneath scales and causes a
lesion at the point of attachment. The damage caused is associated with
loss of blood and exposure to secondary infections by fungi, bacteria, and
possibly viruses.
Lernaea are long (5-22 millimeters) slender copepods which, when at-
tached, give the appearance of a soft sticks with two egg sacs attached at
the distal ends. Actually, the head end is buried in the flesh. This end has
large, horn- like appendages that aid in identification of the parasite (Figure
105).
Figure 104. Argulus sp.
Figure 105. Lernaea sp.
FISH HEALTH MANAGEMENT 335
Masoten at 0.25 part per million active as a pond treatment, repeated
four times at weekly intervals, gives good control of anchor worms. How-
ever, inconsistent results are obtained when water temperatures exceed
80°F or when the pH is 9 or higher. During summer months, Masoten
treatment should be applied early in the morning and it may be necessary
to increase the concentration to 0.5 part per million active for best results.
Packing and Shipping Specimens
Several state agencies have laboratories with biologists trained in the diag-
nosis of fish diseases. In addition, several fish- disease laboratories and a
number of trained hatchery biologists in the United States Fish and
Wildlife Service are available for help in disease diagnosis. In recent years
private consulting biologists also have set up practices in disease diagnosis.
Correct diagnosis depends upon accurate and detailed information re-
garding the fish and the conditions under which they were raised, and
especially upon the proper preparation of material that will be shipped to a
fish- disease laboratory. The more information that is available, the more
likely that the diagnosis will be correct.
If, after a preliminary diagnosis in the hatchery, some treatment already
has been started, specimens and information nevertheless should be sent to
a disease laboratory for verification. Although the symptoms may seem typ-
ical, another disease may be present. It is not uncommon to have two
disease conditions present at the same time, one masking the other.
Although treatments may be effective for one condition, the other disease
may still be uncontrolled. Hatchery personnel should furnish the laboratory
with correctly collected and handled material, including all available infor-
mation, at the earliest possible date. // the required information is not fur-
nished with specimens, conclusive diagnosis may not be possible.
To facilitate the packing and shipping of proper specimens and informa-
tion, a comprehensive checklist, such as the Diagnostic Summary Informa-
tion form (Figure 106), should be included. All instructions and questions
should be read carefully. All questions should be answered. If an answer
cannot be furnished, or a question is not applicable, this should be indicat-
ed in each case. When disease breaks out, specimens should be collected
and preserved before any treatment is given or started. Only a few fish
should be sent for examination, but these should be collected with the ut-
most care. Dead fish or fish that appear to be normal are nearly worthless.
The most desirable fish are those that show most typically the sings of the
disease in question. Moribund, but still living, fish are the best for diagnostic
purposes.
336 FISH HATCHERY MANAGEMENT
DIAGNOS nC SUMMARY INFORMATION
INSTRUCTIONS: Prepare in duplicate, retain one copy at hatchery. Answer all ques-
tions. If information is not available or not applicable, please check
"Na" box. If samples are to be sent separately, note Item 26.
To: From:
1. FISH
Species: Age: Date of collection:
Size: Density: Date of first feeding:
(Number/lb.) (Lbs./cu. ft. of water) (small fingerling only)
2. WATER— CONDITIONS— Na D
Hatchery Trough LJ Dirt Pond I I Circular Pool I I Lake 1 I
Concrete Raceway I I Stream 1 I Dirt Raceway I I Rate of Change: per hr.
Clear I I Turbid I I Muddy I I Colored I I Indicate color
Temp °F pH O2 ppm
3. WATER SOURCE — Na I I (If combination, give percent, temp., and pH of each. If
individual, give temp, and pH only)
Spring I I % Open Stream I I % Reservoir I I %
Well n % Lake D % Runoff rainwater D %
Temp. pH Temp. pH
4. IF POND WATER— Na D
*\Vater Bloom: Abundant I I Surface Algae: Abundant I — I
Moderate I I Partial Cover I I
None LJ None LJ
Type and dates of pond water treatment (if preceded mortality)
For Algae
For course vegetation
Other treatments
* (If bloom is heavy — send preserved sample)
5. FISH FOOD— Na D
Natural I — I Pond fertilization with organic fertilizer I I
Mineral fertilizer Ll None Lj Service Diet LJ
Pellets LJ Pellets with Meat LJ Other diet LJ (Give formula below)
How long Rate of Brand name
diet fed Feeding of pellets
Formula:
Time in storage: Refrigerated: Yes LJ No D
Figure 106. Diagnostic Summary Information form.
FISH HEALTH MANAGEMENT
337
6. FISH COLLECTED FOR SHIPMEN L, INOCULATION OF MEDIA, OR BOTH (Live
(Ish arc superior to preserved fish) — Na I I
Dead I I Moribund I I Appear slightlv abnormal I I Healibv LJ
Not selected in any special way I I
7. PRFA'IOrS TREATMENT (If any)— Na D
Number of treatments: Hours or Davs-
Chemical(s) used:
Sulfamerazine I I
Terramycin I I
Cbloronivcelin I I
PMA D
Calomel I I
Roccal I I
Formalin I I
Other
8. MORTALrriES— Na D
List on a separate page pickofT by days, starting with the first day mortalities seem
abnormal, and indicate on which davs treatments were administered, if any. Mortalities
should be listed as individual tioughs or tanks, as well as by lot. If experimental treatments
are given, a separate list of mortalities in the control trough should be included.
9. OENERAL APPEARANCE— Na D
Normal I I Nervous and scarv I I
Sluggish I I Floating listlesslev I I
Flashing I I Swimming upside I I
down or on the side
Other:
Spiraling or corkscrewing I I
Making spasmodic movements I I
Sinking to the bottom I I
Rubbmg against the bottom I I
10. APPETITE— Na D
Normal I I Reduced I I
Refuse Food I I
1 1 . ARRANGEMENT IN WATER— Na D
Normal Distribution LJ Schooling LJ Near surface I — I
Gasping for air I I Crowding water inlet I I Floating towards outlet I — I
Distribution at even distance, one fish from another, and facing water current I — I
12. BODY SL'RF.\CE— Na D
Normal LJ /Bluish film: in patches I — I or all over I — I
/Grayish-white: patches LJ or tufts I I Swollen areas as furuncles I — I
Deep open lesions with pus and blood LJ /Shallow red ulcers: small I — I large I — I
/Necrotic areas: separate I I confluent I I gray I I It. brown I — I
on head LJ all over LJ lips and head especially I — I
/Granulations: glass bead-like I I pearl-like I I on fins I I
on bodv I I variable in size I I
Figure 106. Continued.
338 FISH HATCHERY MANAGEMENT
12. BOl)\ SURFAC.K— Continued:
/Pinpoinl pimples I I Cysts I I /Pinpoint spots: white I I or black I I
/Paiasiics: verv small, bareh' visible, soil I I oi Ifjnger, hard I I (often with suallowiail
appearance)
/Fish abnormally dark: entire bod% I I certain body areas I I Indicate where
Growth LJ oi Warts I I Iriegiilai I I proliferating I I on surface I I
protruding from: vent I I nostrils I I
mouth LJ gills LJ
color: fish bod\ D red D black D
13. FINS— Na D
Normal I I Swollen I I Necrotic I I Frayed I I
Bluish-white I I Twisted I I Eioded I I
/Spots present: white LJ black LJ /Blood-shot I — I Parasite present I — I
14. CAUD.AL PKDL'NCLE— Na D
Slightly Swollen D Bluish-White D Necrotic D
Very Swollen I I Fungus-like tufts present I I Inflamed I I
15. CILI.S— Na n
Covers open more I I Swollen I I Covered with mucus, I — I
than normallv food and dirt particles
Patches: white I I brown I I gray I I
(IF EXAMINED UNDER MICROSCOPE)
Filaments and Lamellae: Swollen LJ fused I I club-shaped I — I
ballooned I I Cottonv tufts present I I
Small gravish-white objects: on filaments I — I on lamellae I — I
between filaments I I between lamellae I I
Color of gills: deep red LJ pale red I — I
hemorrhagic I I pale pink I — I
16. MUSCULATURE— Na D
Sores I I or Fmuncles I I filled with red pus I I Small red spots I I
i sores I I
or filled with creamy I I or cheesy I I contents
cysts I I
Hard cysts like sand grains: small I I black I I
large I I or \ellow I I
Figure 106. Continued.
FISH HEALTH MANAGEMENT 339
17. EVES— Na D
Normal I I opaque I I W'liiif: lens I I or center I I
Tinv spt)t in lens I I Red spots in cornea I — I
Popeye I I One eye missing I I Both eyes missing I I
If a needle is inserted in the eye socket and the eye is pressed while fish head is under
water, gas bubbles I I or opaque fluid I — I escapes.
IS. BODY CAMTV— Na D
Appears normal LJ Excessive fluid present I — I
/Fluid: Colorless D Opaque D Bloodv D
/Present in lining: Spots U or Hemorrhages LI
/Worms: lape-like LJ or Round LJ /Small Cysts U
19. INTESTINAL TRACT— Na D
Normal LJ Emptv LJ Filled with food I — I
/Filled with mucus: Colorless CH Yellow LJ Reddish lJ
Hind gut bloody LI Blood in vent LI Stomach opened LI
Round worms present LI Flat worms present LI
20. LI\'ER— Na D
Normal D Red D Yellow D Brown D Pale D
Color of coffee w ith cream LJ Marbled LJ Spotty LJ
/Cysts: Small I I or Large I I
/Gall Bladder Bile: Greenish-yellow D Watery Clear D
or Bluish-Bhuk D
21. SPLEEN— Na D
Red D Black-red D Pale D Spotty D
Shrivelled D Swollen D Lumpy D Grosslv Enlarged □
22. PYLORIC CAECA— Na D
Normal LJ Fused together I I Swollen I — I
Worms inside LJ Bloodshot I — I
Figure 106. Continued.
340 FISH HATCHERY MANAGF.MKNT
23. KIDNKY— Na D
Normai Cj /Pinpoint Spots: Gray Lj or White LI
Gray pustules: How many: Where located:
Small CH Creamy consistency Lj Hard and gritty U
Large I I Cheesy consistency I I
24. TUMORS— Na D
Any internal organ: Much enlarged Lj Irregular in shape LI
O IHER CONDITIONS OR SYMPTOMS NOTED: (Continue on reverse, if necessary)
26. If samples are submitted separately from this summary, please identify each test tube,
jar, or other container with the following:
1. Name and address of sender.
2. Dates when specimens were collected, or media inoculated. (See instruction sheet
for packing and shipping specimens.)
Figure 106. Continued.
Shipping Live Specimens
When it is necessary to ship live specimens for diagnostic purposes: (l) as-
sure that everything possible is done to insure that the specimens will be
received alive; (2) take extra precautions to insure that other parcels will
not be damaged by water leakage. Postal authorities have advised that such
shipments should bear the notation "Special Handling" and, in larger
lettering, "LIVE FISH-THIS SIDE UP."
When shipments might exceed 36 to 48 hours duration by other means,
it is best to ship by air express. Air-express packages should bear the name
of the final carrier, final terminal, and any special delivery instructions, in-
cluding a telephone contact. Many shipments can be more economical by
regular air mail. An attempt should be made to determine local schedules
to reduce shipping time.
Whether air-mail or air-express shipments are made, packing should al-
low for gas expansion that occurs in high altitude flights. Fully inflated
packages have burst enroute, causing the contents to leak and the fish to
die. Plastic bags containing about one- fourth water and half or less air or
FISH HEALTH MANAGEMENT 341
oxygen usually provide room for expansion. A general precaution is to use
a double bag system, one bag filled and sealed within another. It is best to
ship a minimum number of specimens. Sick fish and coldwater fish, such as
trout, require greater volumes of water than healthy or warmwater fish.
Twenty volumes of water for each volume of fish usually will be adequate
for healthy fish, but greater volumes should be provided for sick fish. Dur-
ing extreme hot or cold weather, insulated containers may be required.
Expanded polystyrene picnic hampers provide good insulation but are rela-
tively fragile and require protection against damage. They should be
packed, therefore, in a protective corrugated cardboard box or other con-
tainer. Coldwater fish usually ship better if ice is provided. The ice should
be packed in double plastic bags so that it will not leak when it melts.
Shipping Preserved Specimens
Preservatives typically are corrosive and odorous. Containers should be un-
breakable and absorbent material should be provided in the event leakage
does occurs. A good procedure is to fix the fish in a proper fixative for a
day or two, then place the preserved fish, with a very small volume of fixa-
tive, in a plastic bag. The sealed bag should be placed within a second
plastic bag, which also should be sealed. This durable package has minimal
weight. Select representative specimens. Examine them carefully to supply
data in the order given in the Diagnostic Summary Information form.
Bouin's solution is a preferred fixative. Its recipe is: picric acid
(dangerous), 17.2 grams; distilled water, 1,430 milliliters; formalin, 475 mil-
liliters; glacial acetic acid, 95 milliliters. NOTE: picric acid explodes when
rapidly heated. Handle accordingly. Weigh picric acid and place crystals in
a pyrex container large enough to hold 2 liters (2,000 milliliters) and add
distilled water. Heat on a stove. Stir occasionally until all crystals are dis-
solved. Do not boil the solution. When crystals have dissolved, remove the
solution from the stove and cool it completely. Add the formalin and gla-
cial acetic acid to the cooled solution. Stir briefly and pour the mixture
into a jar. This solution will keep well, but should be protected from
freezing.
Volume of the fixative should be at least five to ten times that of the
fish or tissue. (Thus, put only one 6- inch fish in a pint of fixative.) Fish
and tissues should be left in the fixative for at least 24 hours, and then the
fixing solution replaced with 65% ethyl alcohol. However, if alcohol is not
available, retain the specimens in Bouin's fluid.
To facilitate fixation, fish, regardless of size, should be slit down the ab-
domen from the anus to the gills. The air bladder should be pulled out and
broken to permit fixation of the kidney. The kidney of 6-inch or larger fish
should be split along its entire length. The intestines and other organs
342 KISH llAICHKRY MANAGEMENT
should be slit if the fish are larger than fingerlings. It also is desirable to
cut the skin along the back of the fish. If the fish are larger than 6 inches,
the cranial cap should be opened to facilitate fixation of the brain. The
importance of these incisions cannot be overemphasized. If the fish are too
large to ship whole, cut pieces from individual tissues (gill, heart, liver,
etc.), and especially any lesions observed. These pieces should not be larger
than one-half inch square and one-quarter inch thick.
Commercial formalin (containing about 40'^ formaldehyde) also can be
used for preserving specimens and should be mixed with nine parts of wa-
ter to make approximately a 10% formalin solution.
Unless the lesions are very clear and obvious, always preserve several
healthy specimens of the same size and age as the sick fish, and send them
at the same time in a separate container. This important step often determines
whether or not the disease can be diagnosed.
Fish Disease Leaflets
The Fish Disease Leaflet (FDL) series is issued by the United States Fish
and Wildlife Service in order to meet the needs of hatchery personnel for
specific information on fish diseases. Each Fish Disease Leaflet treats a par-
ticular disease or parasite, and gives a brief history of the disease, its etiolo-
gy, clinical signs, diagnosis, geographic range, occurrence, and methods of
control. As new information becomes available, the Fish Disease Leaflets
are revised. They are distributed from the Library, National Fisheries
Center (Leetown), Route 3, Box 41, Kearneysville, West Virginia 25430. In
the following list, leaflets that have been superseded by more recent ones
are omitted.
FDL-1. Infectious pancreatic necrosis (IPN) of salmonid fishes. Ken
Wolf. 1966. 4 p.
FDL-2. Parasites of fresh water fish. II. Protozoa. 3. Ichthyophthirus mul-
tifilis. Fred P. Meyer. 1974. 5 p.
FDL-5 Parasites of fresh water fish. IV. Miscellaneous. Parasites of cat-
fishes. Fred P. Meyer. 1966. 7 p.
FDL~6. Viral hemorrhagic septicemia of rainbow trout. Ken Wolf.
1972. 8 p.
FDL-9. Approved procedure for determining absence of viral hemor-
rhagic septicemia and whirling disease in certain fish and fish
products. G. L. Hoffman, S. F. Snieszko, and Ken Wolf. 1970.
7 p.
FDL-13. Lymphocystis disease offish. Ken Wolf. 1968. 4 p.
FISH HEALTH MANAGEMENT 343
FDL-15. Blue-sac disease of fish. Ken Wolf. 1969. 4 p.
FDL-19. Bacterial gill disease of freshwater fishes. S. F. Snieszko. 1970.
4 p.
FDL-20. Parasites of freshwater fishes. II. Protozoa. 1. Microsporida of
fishes. R. E. Putz. 1969. 4 p.
FDL-21. Parasites of freshwater fish. I. Fungi. 1. Fungi (Saprolegnia and
relatives) of fish and fish eggs. Glenn L. Hoffman. 1969. 6 p.
FDL-22. White-spot disease of fish eggs and fry. Ken Wolf. 1970. 3 p.
FDL-24. Ulcer disease in trout. Robert G. Piper. 1970. 3 p.
FDL-25. Fin rot, cold water disease, and peduncle disease of salmonid
fishes. G. L. Bullock and S. F. Snieszko. 1970. 3 p.
FDL-27. Approved procedure for determining absence of infectious pan-
creatic necrosis (IPN) virus in certain fish and fish products.
Donald F. Amend and Gary Wedemeyer. 1970. 4 p.
FDL— 28. Control and treatment of parasitic diseases of fresh water fishes.
Glenn L. Hoffman. 1970. 7 p.
FDL-31. Approved procedure for determining absence of infectious
hematopoietic necrosis (IHN) in salmonid fishes. Donald F.
Amend. 1970. 4 p.
FDL-32. Visceral granuloma and nephrocalcinosis. Roger L. Herman.
1971. 2 p.
FDL-34. Soft-egg disease of fishes. Ken Wolf. 1971. 1 p.
FDL-35. Fish virology: procedures and preparation of materials for pla-
quing fish viruses in normal atmosphere. Ken Wolf and M. C.
Quimby. 1973. 13 p.
FDL-36. Nutritional (dietary) gill disease and other less known gill
diseases of freshwater fishes. S. F. Snieszko. 1974. 2 p.
FDL-37. Rhabdovirus disease of northern pike fry. Ken Wolf. 1974. 4 p.
FDL-38. Stress as a predisposing factor in fish diseases. Gary A.
Wedemeyer and James W. Wood. 1974. 8 p.
FDL-39. Infectious hematopoietic necrosis (IHN) virus disease. Donald
F. Amend. 1974. 6 p.
FDL-40. Diseases of freshwater fishes caused by bacteria of the genera
Aeromonas, Pseudomonas, and Vibrio. S. F. Snieszko and G. L.
Bullock. 1976. 10 p.
FDL-41. Bacterial kidney disease of salmonid fishes. G. L. Bullock, H.
M. Stuckey, and Ken Wolf. 1975. 7 p.
FDL-43. Fish furunculosis. S. F. Snieszko and G. L. Bullock. 1975. 10 p.
FDL-44. Herpesvirus disease of salmonids. Ken Wolf, Tokuo Sano, and
Takahisa Kimura. 1975. 8 p.
FDL-45. Columnaris disease of fishes. S. F. Snieszko and G. L. Bullock.
1976. 10 p.
344 FISH HATCHERY MANAGEMENT
FDL-46. Parasites of freshwater fishes. IV. Miscellaneous. The anchor
parasite (Lernaea elegans) and related species. G. L. Hoffman.
1976. 8 p.
FDL-47. Whirling disease of trout. G. L. Hoffman. 1976. 10 p.
FDL-48. Copepod parasites of freshwater fish: Ergasilus, Achtheres, and
Salmincola. G. L. Hoffman. 1977. 10 p.
FDL-49. Argulus, a branchiuran parasite of freshwater fishes. G. L. Hoff-
man. 1977. 9 p.
FDL-50. Vibriosis in fish. G. L. Bullock. 1977. 11 p.
FDL-51. Spring viremia of carp. Winfried Ahne and Ken Wolf. 1977.
11 p.
FDL-52. Channel catfish virus disease. John A. Plumb. 1977. 8 p.
FDL-53. Diseases and parasites of fishes: an annotated list of books and
symposia, with a list of core journals on fish diseases, and a list
of Fish Disease Leaflets. Joyce A. Mann. 1978. 77 p.
FDL-54. Pasteurellosis of fishes. G. L. Bullock. 1978. 7 p.
FDL-55. Mycobacteriosis (tuberculosis) of fishes. S. F. Snieszko. 1978.
9 p.
FDL-56. Meningitis in fish caused by an asporogenous anaerobic bac-
terium. D. H. Lewis and Lanny R. Udey. 1978. 5 p.
FDL-57. Enteric redmouth disease of salmonids. G. L. Bullock and S. F.
Snieszko. 1979. 7 p.
FDL-58. Ceratomyxa shasta in salmonids. K. A. Johnson, J. E. Sanders,
and J. L. Fryer. 1979. 11 p.
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FISH HEALTH MANAGEMENT 345
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Washington Department of Fisheries, Seattle.
6
Transportation of Live
Fishes
One extremely important aspect of fish culture and fisheries management
is the transportation of live fishes from the hatchery to waters in which
they are to be planted. The objective of this function is to transport as
many fish as possible with minimal loss and in an economical manner. This
often involves hauling large numbers of fish in a small amount of water,
and, depending upon the time involved, can result in extensive deteriora-
tion of water quality. Sometimes fish arrive at the planting site in poor
physiological condition due to hauling stresses, and may die at the time of
planting or shortly thereafter.
Transportation Equipment
Vehicles
Fish are transported in a variety of ways, ranging from plastic containers
shipped via the postal service to complex diesel truck-trailer units. Air-
planes and seagoing vessels are used to a limited degree (Figure 107). The
extensive stocking of Lake Powell by airplane with rainbow trout and
largemouth bass involved a large, coordinated effort involving several
hatcheries and numerous personnel.
348
TRANSPORTATION OF LIVE FISHES
349
Figure 107. Airplane stocking of trout in a remote lake. (Courtesy Bill Cross,
Maine Department of Inland Fisheries and Wildlife.)
Figure 108. Fish distribution tank mounted on a gooseneck trailer. This unit
can be pulled by a pickup truck.
350 FISH HATCHERY MANAGEMENT
Trucks are the principal means of transporting fish. Most hatcheries
currently use vehicles near 18,000 pounds gross vehicle weight (GVW).
However, units from 6,000 to over 45,000 pounds GVW often are used for
moving fish.
Automatic transmissions are becoming common in all trucks. Automatic
shifting reduces engine lugging or overspeeding, and allows the driver to
concentrate on defensive driving rather than on shifting gears.
Diesel engines also are gaining in popularity. Minimal service and long
life are attractive features but the high initial cost is a major disadvantage.
Cab-over trucks are popular in many areas especially where a short turning
radius is important. Conventional-cab trucks generally are quieter, have
better directional stability, and a less choppy ride because of their longer
wheelbase.
A relatively new and promising innovation in warmwater fish transporta-
tion is the combined use of gooseneck trailers and pickup trucks. These
units are low in cost yet very versatile (Figure 108).
Tank Design
Most new fish-distribution tanks are constructed of fiber glass or alumi-
num, but plywood, redwood, stainless steel, glass, galvanized iron, and
sheet metal all have been utilized in the past.
Aluminum is lightweight, corrosion-resistant, and easily mass-produced.
Alloys in the range 3003H14 to 6061T6 will not cause water-quality prob-
lems.
Fiber glass is molded easily into strong, lightweight tanks and can be
repaired readily. Its smooth surface is simple to clean and sanitize. Alumi-
num and fiber glass appear equally well- suited for fish- transport tanks.
Most tanks constructed in recent years are insulated, usually with styro-
foam, fiberglass, urethane, or corkboard. Styrofoam and urethane are pre-
ferred materials because of their superior insulating qualities and the
minimal effect that moisture has on them. A well-insulated tank miminizes
the need for elaborate temperature-control systems and small amounts of
ice can be used to control the limited heat rises.
Circulation is needed to maintain well-aerated water in all parts of the
tank. Transportation success is related to tank shape, water circulation pat-
tern, aerator type, and other design criteria.
The K factor is the basis for comparing insulation materials. It is the
amount of heat, expressed in BTU's, transmitted in 1 hour through 1
square foot of material 1 inch thick for each degree Fahrenheit of tempera-
ture difference between two surfaces of a material. The lower the K factor,
the better the insulating quality. The following is a list of insulating ma-
terials and their respective K factors:
TRANSPORTATION OF LIVE FISHES
351
Expanded vermiculite
1.60
Oak
1.18
Pine
0.74
Cork
0.29
Styrofoam
0.28
Fiber glass
0.25
Urethane
0.18
The K values indicate that pine must be 4 times as thick as urethane to
give the same insulating quality. Generally, combinations of various materi-
als are used in fabricating distribution tanks.
The distribution tank in Figure 109 is constructed with marine plywood,
insulated with styrofoam and covered inside and out with fiber glass. Units
vary in size and may contain several compartments.
Warmwater distribution tanks generally are compartmented. Compart-
ments facilitate fish stocking at several different sites on a single trip, per-
mit separation of species, and act as baffles to prevent water surges. The
number of compartments used in tanks ranges from two to eight, four be-
ing most common. Tanks in current use have 300-700-gallon capacities,
averaging about 450 gallons. However, 1,200-gallon tanks occasionally are
used to transport catchable size catfish, trout, and bass.
Although most tanks presently in use are rectangular, the trend in recent
years has been towards elliptical tanks, such as those used to transport
milk. This shape has several advantages.
Figure 109. Fiberglass distribution tank with four compartments, each with an
electric aerator (arrow). Additional oxygen is provided through carbon rods or
micropore tubing on the bottom of the tank. (McNenny National Fish Hatchery,
FWS.)
352 FISH HATCHERY MANAGEMENT
(1) "V"-shaped, elliptical, or partially round tanks promote better mix-
ing and circulation of water as the size of the tank increases.
(2) Polyurethane insulation, which has the best insulating qualities, lends
itself ideally to a round or oval tank. It can be injected easily within the
walls of the tank.
(3) These tanks can be constructed with few structural members and
without sharp corners that might injure fish.
(4) Rapid ejection of fish is facilitated by an elliptical tank.
(5) Lowering the water level in these tanks reduces surface area and sim-
plifies the removal of fish with dip nets. The rounded bottom also contri-
butes in this respect.
(6) As this shape of tank is widely used by bulk liquid transport com-
panies, they are mass-produced and readily available.
(7) This shape conforms to a truck chassis and holds the center of grav-
ity towards the area of greatest strength.
(8) Construction weight is less than that of rectangular tanks of the same
capacity.
Circulation
Circulation systems are of various sizes and designs; all have plumbing ad-
ded for the pickup and discharge of water. Suction lines to the pumps lie
on the bottom of the tank and are covered by perforated screens. Water is
carried to the pumps and then forced through overhead spray heads
mounted above the waterline. In most systems, oxygen is introduced in one
of the suction lines just ahead of the pump. This usually is controlled by a
medical gas-flow meter; because of the danger involved in handling and
transporting bottled oxygen, care must be taken to follow all prescribed
safety procedures.
Self- priming pumps powered by gasoline engines are used to circulate
water in many distribution units. Pumps may be close-coupled or flexibly
coupled. Although the former type is more compact, it tends to transfer
heat to the water. Depending upon ambient air temperature, close-coupled
pumps may increase the temperature of 400 gallons of water by about 7°F
an hour, whereas flexible coupling will reduce heat transfer to approxi-
mately 3°F per hour.
Pipes used in conjunction with pumps usually are black or galvanized
steel. Although steel is durable, threads may rust, and replacement or
modification following installation may prove difficult. Aluminum pipe also
has been used in systems of this type, but its advantages and disadvantages
are reportedly similar to those of steel except aluminum pipe does not rust.
Because of the ease of installation, plastic pipe should be considered for
TRANSPORTATION OF LIVE FISHES 353
use. It is noncorrosive, lightweight, and easy to assemble, modify, and
remove.
Friction reduces water flow through a circulation system if there is an
excess of pipe fittings. Further, the diameter of piping should not be re-
duced within the system except at the spray devices.
Generators and electric pumps or aerators sometimes are used, especially
on larger trucks or trailers with multiple tanks. This eliminates the need
for many small engines with all their fuel and maintenance problems. Heat
and noise problems are minimized by placing the generator on the rear of
the unit.
A method of circulating water with 12- volt mechanical aerators uses car-
bon rods and micropore tubing for dispensing oxygen (Figure llO). Aera-
tors alone may not be sufficient to provide the oxygen needed to transport
large loads of fish, but a supplemental oxygenation system can increase the
carrying capacity of the transportation tank. Some advantages of aerator
systems over gasoline- driven water pump systems are:
(1) Temperature increases from aerators are less than 1°F per hour, com-
pared with 2.5°F with pumps.
(2) Aerators and the oxygen injection system can operate independently.
There are advantages to carrying small sizes of certain species of fish on
oxygen alone. Oxygen also can be used as a temporary backup system if
aerators fail.
(3) Usually, aerators have fewer maintenance problems.
(4) Costs of recirculating equipment and aerators strongly favor aerators.
(5) Use of aerators eliminates the space required between the tank and
truck cab for pumps and plumbing, so the overall truck length can be
reduced to assure safer weight distribution. The empty weight of a truck
with a 1,250-gallon tank equipped with aerators is 14,000 pounds — 2,000
pounds less than a similar unit operating with pumps and refrigeration.
The most efficient tanks have the highest water circulation rates, but cir-
culation rates must be balanced with water capacity. Pumping or aerating
systems should be able to circulate at least 40"o of the tank water per
minute when 8-9-inch salmonids are hauled, though lesser rates are ap-
propriate for smaller fish.
Aeration
The purpose of aeration during transport is to provide oxygen and to
reduce the concentration of carbon dioxide. The exchange of gases
between water and the atmosphere is a recognized and important problem
in transporting fish. Transport water must contain adequate oxygen, pH
354 FISH HATCHERY MANAGEMENT
Figure 110. Aerator-oxygen system designed and tested by FWS personnel at
Alchesay National Fish Hatchery, New Mexico, (l) Aerators mounted on top of
an aluminum tank. Note the electrical line for the 12-volt system. (2) Aerator
with a dual manifold extending through the false bottom of a tank. Water is
pulled through manifold (M) and discharged through aerator (A). (3) Aerator in
operation. Water is aerated and circulated and carbon dioxide is removed. (4)
The false bottom of the tank has been removed to show micropore tubing
(arrow) which disperses oxygen into the water. Note bubbling of oxygen through
the water. (Photos courtesy Alchesay National Fish Hatchery, FWS.)
levels must remain within a tolerable range, and toxic levels of dissolved
ammonia and carbon dioxide must be suppressed. A partial solution to this
complex problem is aeration by sprays, baffles, screens, venturi units,
compressed gas liberation, agitators, or air blowers. Bottled gaseous or
liquid oxygen is liberated within tanks in a variety of ways, including per-
forated rubber tubing, carborundum stones, carbon rods, and micropore
tubing, or is injected directly into the recirculation system.
Recent aeration innovations include a miniature water wheel that aerates
water during transport and the Fresh- flo^ aerator. The latter is commer-
cially available in ten sizes. The system depends upon centrifugal force
created by a high speed motor-driven impellor that pulls water into a sys-
tem of vanes, producing the turbulence needed to mix water with air,
while concurrently removing carbon dioxide. This aerator has been highly
satisfactory for transportation of warmwater fish and salmonids.
TRANSPORTATION OF LIVE FISHES 355
The formation of scum and foam on the surface of transport water may
result from drug usage or excessive mucus produced by large numbers of
fish hauled over long distances. Excessive foaming interferes with observa-
tion of fish during transit and inhibits aeration. To alleviate this problem, a
10"o solution of Dow Coming's Antifoam AF emulsion should be used at
the rate of 25 milliliters per 100 gallons of water. For maximum effective-
ness, the compound should be mixed in before drugs are added or fish
loaded. Antifoam is nontoxic to fish.
Water Quality
Oxygen
The most important single factor in transporting fish is providing an ade-
quate level of dissolved oxygen. However, an abundance of oxygen within
a tank does not necessarily indicate that the fish are in good condition.
The ability of fish to use oxygen depends on their tolerance to stress, water
temperature, pH, and concentrations of carbon dioxide and metabolic
products such as ammonia.
The importance of supplying sufficient quantities of oxygen to fish in
distribution tanks cannot be overemphasized. Failure to do so results in
severe stress due to hypoxia and a subsequent buildup of blood lactic acid,
and may contribute to a delayed fish mortality. Ample oxygen suppresses
harmful effects of ammonia and carbon dioxide. Dissolved-oxygen content
of transport water preferably should be greater than 7 parts per million,
but less than saturation. Generally, as long as the oxygen concentration is
at least 6 parts per million, salmonids have ample oxygen; however, should
carbon dioxide levels increase, more oxygen is required by the fish. Oxy-
gen consumption by fish increases dramatically during handling and load-
ing into the transportation tank. For this reason, additional oxygen (as
much as twice the flow normally required) should be provided during load-
ing and the first hour of hauling. The oxygen flow can be reduced to nor-
mal levels (to provide 6 parts per million in the water) after this acclima-
tion period, when the fish have become settled and oxygen consumption
has stabilized (see Stress, page 358).
The addition of certain chemicals such as hydrogen peroxide has been
effective in increasing the oxygen concentration in water. However, a more
practical and economical method is to introduce oxygen directly from pres-
surized cylinders into the circulating water.
Control of water temperature, starving fish before they are transported,
and the addition of chemicals and anesthetics to the water have reduced
hauling stress.
356
FISH HATCHERY MANACJKMENT
Temperature
Insulation and ice have been used to control the temperature of transport
water. Ice sometimes is difficult to find during a delivery trip and can
cause damage to fish and tanks if used in large pieces. The main advantage
of ice is its simplicity; it involves no mechanical refrigeration equipment
that can break down.
Refrigeration units are being used increasingly to mechanically control
water temperature. Such units are expensive and require careful mainte-
nance. Large units easily justify the cost of refrigeration but small systems
require additional development before they become economical (Figure
111).
Because temperature is such an important factor, it should be continu-
ously monitored and controlled. Electric thermometers are readily available
and inexpensive, and provide monitoring of temperature from the truck cab.
Temperature strongly influences oxygen consumption by fish; the lower
the temperature, the lower the oxygen consumption. For each 1°F rise in
temperature, the fish load should be reduced by about 5.6%; conversely, for
each 1°F decrease in temperature, the load can be increased about 5.6%.
Thus, if a distribution tank will safely hold 1,000 pounds of 9-inch trout in
52°F water, an increase in temperature to 57°F decreases the permissible
load by 27.8%i (5° x 5.56%), or to 722 pounds. If the water temperature is
decreased from 52°F to 47°F, the load can be increased by 27.8')(i to 1,278
pounds.
Figure 111. Aluminum elliptical tank with refrigeration unit mounted at the
front. Aeration is by gas-driven pumps and pure oxygen. Note air scoops (arrow)
for CO2 removal on front and rear of tanks. (Ennis National Fish Hatchery,
FWS.)
TRANSPORTATION OF LIVE FISHES 357
Ammonia
When fish are transported in distribution tanks, their excretory products
accumulate in the water. Ammonia is the main metaboHc product of fish
and is excreted through the gills. Total ammonia concentrations can reach
10 parts per million (ppm) or higher in fish distribution tanks depending
on the fish load and duration of the haul. Exposure to 11 to 12 parts per
million total ammonia (0.13 to 0.14 ppm un-ionized ammonia) for 6 hours
and longer adversely affects trout and can reduce stamina.
Temperature and time of last feeding are important factors regulating
ammonia excretion. For example, trout held in water at 34°F excrete 66%
less ammonia than those held in 51°F water, and fish starved for 63 hours
before shipment produce half as much ammonia as recently fed fish. Small
fish should be starved for at least two days prior to shipping. Fish larger
than 4 inches should be starved at least 48 hours; those 8 inches and larger
should be starved 72 hours. If they are not, large losses may occur.
Water temperature during shipping should be as low as can be tolerated
by the fish being handled. Low temperatures not only reduce ammonia
production, but oxygen consumption as well.
The effects of metabolic waste products and related substances on warm-
water fish during transportation have received little attention, but most fish
culturists agree that excretory products, mucus, and regurgitated food de-
grade water quality and stress the fish. Cannibalistic species, such as large-
mouth bass, walleye, and northern pike, obviously should not be starved.
Although proper grading for size of fish will reduce cannibalism, it does
not eliminate it.
Carbon Dioxide
Elevated carbon dioxide concentrations are detrimental to fish and can be
a limiting factor in fish transportation. A product of fish and bacterial
respiration, CO2 acidifies transport water. Although this reduces the per-
centage of un-ionized ammonia in the water, it also reduces the oxygen-
carrying capacity of fish blood. Fish may succumb if CO^ levels are high,
even though oxygen levels are seemingly adequate. Trout appear to
tolerate carbon dioxide at levels less than 15.0 parts per million in the
presence of reasonable oxygen and temperature, but become distressed
when carbon dioxide levels approach 25.0 parts per million.
Fish transported in distribution tanks are exposed to gradually increas-
ing concentrations of carbon dioxide. Unless aeration is adequate, CO^ lev-
els may exceed 20-30 parts per million. In general, for each milliliter of
oxygen a fish consumes, it produces approximately 0.9 milliliters of CO2.
If the CO2 level increases rapidly, as with heavy fish loads, fish become
358 FISH HAICHERY MANAGEMENT
distressed. However, elevated concentrations of CO2 can be tolerated if the
rate of buildup is slow.
Adequate ventilation, such as air scoops provide (Figure 111), is a neces-
sity for distribution units. Tight covers or lids on the units can result in a
buildup of CO2 which will stress the fish. Aeration of the water will reduce
concentrations of dissolved CO2, if there is adequate ventilation. As men-
tioned previously, antifoam agents reduce foaming, which inhibits aeration
and contributes to the buildup of CO2.
Buffers
Rapid changes in pH stress fish, but buffers can be used to stabilize the
water pH during fish transport. The organic buffer trishydroxymethyl-
aminomethane is quite effective in fresh and salt water. It is highly soluble,
stable, and easily applied. This buffer has been used on 29 species of fish
with no deleterious effects. Levels of 5-10 grams per gallon are recom-
mended for routine transport of fish. The least promising buffers for fish
tanks have been inorganic compounds such as phosphates.
Handling, Loading, and Stocking
Stress
Stress associated with loading, hauling, and stocking can be severe and
result in immediate or delayed mortality. When fish are handled vigor-
ously while being loaded into distribution units, they become hyperactive.
They increase their oxygen consumption and metabolic excretion. The first
hour of confinement in the unit is critical. Oxygen consumption remains
elevated for 30-60, minutes then gradually declines as fish become
acclimated. If insufficient oxygen is present during this adjustment period, fish
may develop an oxygen debt. The problem may be alleviated if oxygen is
introduced into the distribution tank 10 to 15 minutes before fish are
loaded, especially if the water has a low dissolved oxygen content. When
fish are in the unit, the water should be cooled. After the first hour of the
trip, the oxygen flow may be gradually decreased, depending on the condi-
tion of the fish.
The total hardness should be raised in waters used to hold fish during
handling and shipping. The addition of 0.1-0.3% salt and enough calcium
chloride to raise the total hardness to 50 parts per million is recommended
for soft waters. Calcium chloride need not be added to harder waters,
which already contain sufficient calcium.
Striped bass are commonly transported and handled in a 1.0% salt solu-
tion. Fingerlings should be held in tanks for 24 hours after harvest to allow
TRANSPORTATION OF LIVE FISHES 359
them to recover from stress before they are loaded. The fish appear to
tolerate handling and transportation much better in saline solutions.
The numbers of bacteria in a warmwater fish transport system should be
kept at a minimum level. Acriflavin at 1.0-2.0 parts per million (ppm),
Furacin at 5.0 ppm, and Combiotic at 15.0 ppm are effective bacteriostats
during transport. Although varying degrees of success have been attained
with the above compounds, sulfamerazine and terramycin are the only bac-
tericides currently registered for use on food fish.
Anesthetics
Experimentation with anesthetics and their effects on fish was most active
during the 1950's. The main benefit of anesthetics is to reduce the meta-
bolic activity of fish, which results in lower oxygen consumption, less car-
bon dioxide production, and reduced excretion of nitrogenous wastes. Such
drugs made it possible to transport trout at two to three times the normal
weight per volume of water. Their tranquilizing effects also reduce injury
to large or excitable fish when they are handled.
Considerable care must be taken to assure that proper dosages of
anesthetics are used. Deep sedation (Table 39) is best for transported fish.
Deeper anesthesia produces partial to total loss of equilibrium, and fish
may settle to the bottom, become overcrowded, and suffocate. If pumps are
used to recycle water, anesthetized fish may be pulled against the intake
screen, preventing proper water circulation.
Methane tricainesulfonate (MS-222) in a concentration of 0.1 gram
MS-222 per gallon of water, appears to be useful in transporting fish.
Reduced mortality of threadfin shad has been attained when the fish were
hauled in a T'o salt solution containing 1.0 gram MS-222 per gallon of
water. Concentrations of 0.5 and 1.0 gram MS-222 per gallon of water are
not suitable for routine use in the transportation of salmon because
anesthetized salmon have both a high oxygen consumption and a long
recovery time.
Golden shiners have been transported successfully in 8.5 parts per mil-
lion sodium Seconal and smallmouth bass in 8.5 parts per million sodium
amytol. A pressurized air system was used in conjunction with the drugs.
However, caution is advised because drugs tend to lose their strength at
temperatures above 50°F. Fathead minnows have been transported safely in
2.3 parts per million sodium Seconal at 50°F. California Department of Fish
and Game personnel have reduced oxygen consumption by transported fish
with 8.5 parts per million sodium amytol. Oklahoma state personnel suc-
cessfully use a mixture of 2.0 parts per million guinaldine and 0.25% salt
for transporting a variety of fish.
360
FISH HATCHERY MANAGEMENT
Table 39. classification of ihk behavioral changes ihai occur in fishes
DURING anesthesia. LEVELS OF ANESIHESIA CONSIDERED VALUABLE TO
FISHERIES WORK ARE ITALICIZED. (SOURCE: McFARLAND 19fi0).
DEFINABLE LEVELS OF ANESTHESIA
STATE PLANE WORD EQUIVALENTS
BEHAVIORAL RESPONSES OF FISH
II
//
///
IV
Normal
1 Light sedation
2 Deep sedation
1 Partial loss of
equilibrium
Total loss of
equilibrium
Loss of reflex
reactivity
Medullary collapse
Reactive to external stimuli, equilibrium
and muscle tone normal.
Slight loss of reaction to external stimuli
(visual and tactile).
No reaction to external stimuli except
strong pressure; slight decreased oper-
cular rate.
Partial loss of muscle tone; reaction only
only to very strong tactile and vibra-
tional stimuli; rheotaxis present, but
swimming capabilities seriously dis-
rupted; increased opercular rate.
Total loss of muscle tone; reaction only to
deep pressure stimuli; opercular rate
decreased below normal.
Total loss of reactivity; respiratory rate
very slow; heart rate slow.
Respiratory movements cease, followed
several minutes later by cardiac arrest.
Carrying Capacity
The weight of fish that can be safely transported in a distribution unit
depends on the efficiency of the aeration system, duration of the haul, wa-
ter temperature, fish size, and fish species.
If environmental conditions are constant, the carrying capacity of a dis-
tribution unit depends upon fish size. Fewer pounds of small fish can be
transported per gallon of water than of large fish. It has been suggested
that the maximum permissible weight of trout in a given distribution tank
is directly proportional to their length. Thus, if a tank can safely hold 100
pounds of 2-inch trout, it could hold 200 pounds of 4-inch trout, and 300
pounds of 6-inch trout.
Reported loading rates for fishes vary widely among hatcheries, and
maximum carrying capacities of different types of transportation units have
not been determined.
Fish loadings have been calculated and reported inconsistently. In the
interests of uniform reporting by fish culturists, it is suggested that loading
densities be calculated by the water-displacement method. This is based on
TRANSPORTATION OF LIVE FISHES
361
Table 40. proximate amount of water displaced by a known weight of fish.
ALL figures rounded TO NEAREST WHOLE NUMBER. (SOURCE: McCRAREN AND
JONES 1978).
WEIGHT
WATER
WEIGHT
WATER
WEIGHT
WAIKR
OF FISH
DISPLACED
OF FISH
DISPLACED
OF FISH
DISPLACED
(LB!
(GAL!
iLB)
(GAL5
fLB)
(GAL)
100
12
1,500
180
2,800
336
200
24
1,600
192
2,900
348
300
36
1,700
204
3,000
360
400
48
1,800
216
3,100
372
500
60
1,900
228
3,200
384
600
72
2,000
240
3,300
396
700
84
2,100
252
3,400
408
800
96
2,200
264
3,500
420
900
108
2,300
276
3,600
432
1,000
120
2,400
288
3,700
444
1,100
132
2,500
300
3,800
4.56
1,200
144
2,600
312
3,900
468
1,300
156
2,700
324
4,000
480
1,400
168
the actual volume of the distribution tank being used, the weight of fish
being transported, and the volume of water displaced by the fish.
Table 40 provides the water displacements for various weights of fish. As
an example, what would be the loading density of 800 pounds of fish trans-
ported in a ,500-gallon tank?
T ,. , . pounds of fish
Loadmg density = *^
( , ,1 \ tank capacity — water displaced by fish
(pounds per gallon) r ; r /
Loading density
Loading density
(gallons)
800
(galic
500-96
1.98 pounds per gallon
TROUT AND SALMON
Normal carrying capacity for 1.5-inch and 2.5-inch chinook salmon is
0.5-1.0, and 1.0-2.0 pounds per gallon, respectively. The carrying capacity
for 4-5-inch coho salmon is 2.0-3.0 pounds per gallon of water.
Under ideal conditions, the maximum load of 8-11-inch rainbow trout is
2.5-3.5 pounds per gallon of water for 8 to 10 hours. Similar loading rates
are appropriate for brook, brown, and lake trout of the same size.
362 FISH HATCHERY MANAGEMENT
CHANNEL CATFISH
Channel catfish have been safely transported at loadings presented in
Table 41. Experience will dictate whether or not the suggested loadings are
suitable for varying situations. If the trip exceeds 16 hours, it is recom-
mended that a complete water change be made during hauling.
Catfish also may be transported as sac fry and in the swim- up stage.
Most transfers of these stages should be of relatively short duration. Oxy-
gen systems alone are satisfactory when fry are hauled, and have some ad-
vantages over the use of pumps because suction and spraying turbulence is
eliminated. If pumps and spray systems are used, the pump should be
operated at a rate low enough to minimize roiling of water in the compart-
ments. Sac fry, 5,000 per 1.5 gallons of water, have been shipped success-
fully in 1-cubic-foot plastic bags for up to 36 hours. Water temperature
should be maintained at the same level fry experienced in the hatchery.
Although it may be advantageous to gradually cool the water for shipping
some warmwater species, it is not recommended for channel catfish fry.
Fingerlings of 1-6 inches ship well for 36 hours. As with salmonids, the
number and weight of fish transported varies in proportion to the size of
the fish and duration of the shipment.
The following guidelines may be of value for hauling channel catfish:
(1) Four pounds of 16-inch catfish can be transported per gallon of water
at 65T.
(2) Loading rates can be increased by 25"o for each 10°F decrease in wa-
ter temperature, and reduced proportionately for an increase in tempera-
ture.
(3) As fish length increases, the pounds of fish per gallon of water can be
increased proportionally. For example, a tank holding 1 pound of 4-inch
Table 41. pounds of catfish that can be transported per gallon of fi5°F
WATER. (SOURCE: MILLARD AND McCRAREN, UNPUBLISHED)
NO. OF FISH TRANSIT PERIOD IN HOURS
PER POUND 8 12 16
1.0 6.30 5.55 4.80
2.0 5.90 4.80 3.45
4.0 5.00 4.1 2.95
50 3.45 2.50 2.05
125 2.95 2.20 1.80
2.50 2.20 1.75 1.50
.500 1.75 1.65 1.25
1,000 1.25 1.00 0.70
10,000 0.20 0.20 0.20
transportation of live fishes 363
Table 42. pounds of centrarchids that can be distributed per gallon of
WATER AT temperatures RANGING BETWEEN fi5° AND H.IT. (AFTER WILSON 19.50.)''
NO. OF FISH
SIZE
.'VPPRO.XIM.ME
NO.
POUNDS OF FISH
PER LB.
(INCHES)
OF FISH PER G
.M..
PER GAL.
25.0
4.0
25.0
1.00
100.0
3.0
67.0
0.66
400.0
2.0
200.0
0.50
1,000.0
1.0
333.0
0.33
'^Although time is not given by Wilson, the literature indicates minimal problems up to 16
hours at these rates.
catfish will safely hold 2 pounds of 8- inch, or 4 pounds of 16-inch fish per
gallon of water.
(4) If the transportation time exceeds 12 hours, the loading rate should
be decreased by 25"n.
(5) If the transportation time exceeds 16 hours, loading rates should be
decreased by 50% or a complete water change should be arranged.
(6) During the winter, hauling temperatures of 45-50°F are preferred,
whereas 60-70°F are preferable during summer months.
LARGEMOUTH BASS, BLUEGILL, AND OTHER CENTRARCHIDS
In keeping with current stocking requirements, centrarchids are transport-
ed primarily as small fingerlings at light densities (Table 42).
Largemouth bass fingerlings of 6-10 inches can be transported at 2.0
pounds per gallon of water for up to 10 hours without loss. This loading
rate was used when several southwestern hatcheries transported larger
largemouth bass fingerlings and most trips were considered highly success-
ful. Aeration was provided by aerators and bottled oxygen introduced at
0.14—0.21 cubic foot per minute.
STRIPED BASS
The Fish and Wildlife Service in the southeastern United States hauled
striped bass averaging 1,000 per pound at a rate of 0.15 pounds per gallon
of water for up to 10 hours with few problems. Fingerlings averaging five
per pound were transported at rates of 1.5 pounds per gallon for 10 hours
and 0.75 pounds per gallon for 15 hours. Recirculation systems and agita-
tors both have been used successfully. The recommended water tempera-
ture for hauling striped bass is 55°-65°F. Successful short hauls have been
made at higher temperatures.
Striped bass averaging 500 per pound have been successfully transported
at loadings approaching 0.5 pound per gallon for periods of 19 to 24 hours.
364 fish harchkry management
Table 43. pounds of northern pike and walleye ihai can be carried per
gallon of water at temperatures between .w" to 6r>°f. (source: raymond a.
phillips, personal communicaiion.)
no. of fish size pounds of transit period
per lb. (inches) fish per gal. ' (hours)
(iO.O 3.0 l.M) 8.0
.■")0().() 2.0 O.fif) H.O
1,000.0 1.0 0. ,''),'■) H.O
Striped bass fry 1 or 2 days old have been shipped successfully in plastic
bags. Very little mortality has been experienced in transporting fry for 48
hours at numbers up to 40,000 per gallon of water. Striped bass less than 2
months old exhibit considerable tolerance when abruptly transferred into
waters with temperatures of 44°F to 76°F and salinities of 4 to 12 parts per
thousand.
This species normally is transported and handled in a 1.0% reconstituted
sea-salt solution to reduce stress. Striped bass do not require tempering
when transferred either from fresh water to 1% saline or from saline to fresh
water.
NORTHERN PIKE, MUSKELLUNGE, AND WALLEYE
Table 43 suggests loading rates that have proved successful for northern
pike and walleye.
Muskellunge fry often are transported in small screen boxes placed in
the tank of a distribution truck. Fry also have been transported successfully
in plastic bags inflated with oxygen. Fingerlings are transported in tanks,
either of 250 or 500 gallons capacity; oxygen is bubbled into the tanks but
no water circulation is attempted. About 0.5 pound of 10-14-inch finger-
lings can be carried per gallon of water, and 1-2 parts per million acrifla-
vine is added to the tank to reduce bacterial growth.
Stocking Fish
It has been an established practice to acclimate fish from the temperature
of the transportation unit to that of the environment into which they are
stocked, a process called tempering. In the past, temperature was the main
reason given for tempering fish. There is some doubt, however, that tem-
perature is the only factor involved. Evidence in many cases has failed to
demonstrate a temperature shock even though there was a difference of as
much as 30°F; changes in water chemistry and dissolved gas levels may be
more important than temperature changes. The fish may be subjected to
Figure 112. Plastic bag shipment of fish. The container should be at least 4-mil
plastic and preferably thicker for catfish and large sunfish. (l) The proper weight
of fish is combined with the required amount of water. (2) Fish then are poured
into the plastic shipping bag. Any chemicals such as anesthetics or buffers
should be added to the water before the fish are introduced. (3) The bag is then
filled with oxygen. All the air is first forced out of the bag, which is then refilled
with oxygen through a small hole at the top of the bag, or the bag can be
bunched tightly around the oxygen hose. Approximately 75"i> of the volume of
the bag should be oxygen. The bag then is heat-sealed or the top is twisted
tightly and secured with a heavy-duty rubber band. (4) Because cool water can
support more fish than warm water, the water temperature in the shipping con-
tainer should be kept as cool as the fish will tolerate. If ice is needed it may be
placed directly with the fish or in separate bags (arrow) next to the fish con-
tainer. In this way the fish and water are cooled simultaneously. (5)
Polyurethane foam - inch thick is excellent insulation for shipping, but it is
heavier and less efficient than foam. (6) The package then is sealed and prop-
erly labelled for shipment. (Photos courtesy Don Toney, Willow Beach National
Fish Hatchery, FWS.)
365
366 fish hatchi.ky management
Table 44. kecommendkd loadings and ireaimenls im:r siiiimmng lmi iok
rainbow or brook iroui l.iod i'lr i'ound). the ccjntalner almosl'ukrl is
blair, elsii and wildliee service, unit bi.isiied.)
NlMlil.K
.SI'WIKS
oi- HSU
C(JN lAIM.K
1 \ M 1 \ 1 1 1 1 \
(1)
Largemouth bass
()-l()()
1 -gallon t libilainer
None
(2)
Largemoulh bass
I()5-l.-.()
1 -gallon cubitainer
None
(3)
Largemouth bass
1. '),'")- ,')()()
12 X 2(i-inch, 4- mil
plastK bag
Ncme
(4)
Bluegill
0- 100
1 -gallon cubilainer
None
(5)
Bluegill
lo.v :-!()()
1 -gallon cubilainer
None
(6)
Bluegill
3(),')-8()()
12 X 2H-in(;h, 4- mil
plastii bag
None
(7)
Rainbow or brook
trout
()-:-i(i()
12 - 2K-inch, 4- mil
plastic bag
Newspajjcr
(8)
Rainbow or brook
O-HOO
12 « 24-incli, 4-mil
Rigid poly-
trout
plastic- bag
u re thane foam
carbon dioxide and oxygen tensions in the shipping water that are not
present in the natural environment. Osmotic shock can be a very serious
problem, particularly if fish reared in hatcheries with buffered water from
limestone formations are stocked into dilute acidic waters.
Addition of receiving water to the fish distribution tank before fish are
unloaded requires effort, but the benefits will more than justify the effort
in many situations. As fish are gradually changed from hauling water to re-
ceiving water, they have an opportunity to make some adjustments to their
future environment. Flowing water also aids in removing fish from the tank
with minimum stress.
Shipping Fish In Small Containers
Polyethylene bottles have been used to transport small trout, especially by
horseback to back-country areas. After the bottle is filled with water, fish,
ice, and oxygen, it is placed in an insulated container for shipment.
Plastic bags frequently are used to ship small numbers of tropical fish,
warmwater fish, and trout (Figure 112). Upon arrival at the destination the
plastic bags should be allowed to float unopened in a shaded area of the re-
ceiving water supply for about 30 minutes to acclimate the fish.
There are varying and sometimes conflicting opinions regarding fish
loads, water volume, the use of buffers, and container sizes to be used in
shipping fish. Some suggested shipping loads are presented in Table 44.
The following excerpts from private communications collected at the
TRANSPORTATION OF LIVE FISHES
367
LARGEMOUTH BASS (1,500 FISH PER POUND), BLUEGILLS (2,100 PER POUND), AND
PURE OXYGEN. SHIPPING TIME SHOULD NOT EXCEED 21 HOURS. (SOURCE: ALAN B.
PAR 1 .S PER
GRAMS
MILLILITERS
GALLONS
POUNDS
MILLION
TRIS HLFFER
lERTIARV
OF U ATER
OF ICE
AC'RIFLAVIN
KM [)H
AMVL ALCOHOL
SPECIES
().,')
0
2.5
0
0
(1)
0.5
0
2.5
«i
1.5
(2)
1.5
0
2.5
18
4.5
(3)
0.5
0
2.5
0
0
(4)
0.5
0
2.5
(')
1.5
(5)
1.5
0
2.5
IK
4.5
(6)
1.0
12
0
12
3.0
(7)
0.75
4
0
12
2.0
(8)
Warmwater Fish Cultural Development Center, San Marcos, Texas, may
also be of interest to fish culturists faced with determining a suitable proto-
col for container shipment of fish. All comments relate to containers with
one atmosphere of pure oxygen:
. . . Good survival was achieved shipping 100 bluegill sunfish (l,200 fish
per pound) in ^ gallon of water. If shipment is 30 hours or less, we believe
it safe to ship 200 fish in -; gallon of water in a one-gallon cubitainer.
. . . We had excellent survival on mail distribution. We used ^ gallon
water per one-gallon cubitainer, an oxygen overlay, and largemouth bass
going 900 per pound. Duration of shipment was 24 hours.
. . . Amyl alcohol slightly increased survival time for all species tested
when used at rates of 2.0-3.0 ml per gallon of water. This chemical appears
to tranquilize the fish, thereby reducing metabolism.
. . . When shipping in plastic bags we seldom use ice with largemouth bass,
and never with northern pike and walleye.
. . . We load each bag or box with 50,000 northern pike fry, 70,000 walleye
fry, or up to 600 small largemouth bass fingerlings. We have experienced
mortalities in shipments when using V-bottom plastic bags. All species will
hold for 24 hours but we prefer to get the fish out of the bag in 4-10
hours.
. . . Catfish sac fry were shipped by air from Dallas to Honolulu, Hawaii,
for several years with good success. We used 1 -cubic-foot plastic cubi-
tainers with 12 pounds of water to 6 ounces of fry. Shipments arriving
within 24 hours usually had losses of 5"m or less.
368 FISH HATCHERY MANAGEMENT
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TRANSPORTATION OF LIVE FISHES 369
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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.
0
1
2
3
4
F)
6
7
8
•J
30
1.1
0.6
0.0
0.6
1.1
1.7
2.2
2.8
3.3
3.9
40
4.4
5.0
5.6
6.1
6.7
7.7
7.8
8.3
8.9
9.4
50
10.0
10.6
11.1
11.7
12.2
12.8
1 3.3
13.9
14.4
15.0
60
1,1. fi
16.1
16.7
17.2
17.8
18.3
18.9
19.4
20.0
2().fi
70
21.1
21.7
22.2
22.8
23.3
23.9
24.4
25.0
25.6
26.1
80
26.7
27.2
27.8
28.3
28.9
29.4
30.0
30.6
31.1
31.7
90
32.2
32.8
33.3
33.9
34.4
35.0
35.6
36.1
36.7
37.2
Table A-4. volumetric and weight equivalents of water in metric and
(source: charles l. sowards unpublished.) example: to find the weight in
column; then read horizontally to find 3.78.s in the "kilogram" column,
gram of water at 4°c and on an atmospheric pressure of 760 mm mercury.
CUBIC
CUBIC
YARD
FOOT
CUBIC INCH
GALLON
QU.^RT
PINT
(1)
1.309
35.361
61,095
264.5
1 ,058
2,116
(2)
0.001
0.035
61.09
0.264
1 .058
2.116
(3)
—
—
0.061
—
0.001
0.002
(4)
1
27
46,656
201.98
807.9
1,616
(5)
0.037
1
1,728
7.48
29.92
59.85
(6)
0.005
0.134
231
1
4
8
(7)
0.001
0.033
57.75
0.25
1
2
(8)
0.001
0.017
28.88
0.125
0.5
1
(9)
—
0.016
27.71
0.12
0.48
0.96
(10)
—
0.001
1.805
0.008
0.031
0.062
(11)
—
0.001
1.732
0.007
0.03
0.06
(12)
—
—
1
0.004
0.017
0.035
(13)
—
—
0.061
—
0.001
0.002
CONVERSION lABLES 377
Table A-3. temperatures-centigrade to Fahrenheit, temperature in
DEGREES centigrade IS EXPRESSED IN THE LEFT COLUMN AND IN THF. TOP ROW;
THE CORRESPONDING TEMPERATURE IN DEGREES FAHRENHEIT IS IN THE BODY OF
TABLE.
TEMP°
C.
0
1
2
3
4
5
6
7
8
9
0
32.0
33.H
35.6
37.4
39.2
41.0
42.8
44.(i
46.4
48.2
10
50.0
51.8
53.6
55.4
57.2
59.0
60.8
62.6
64.4
66.2
20
68.0
69.8
71.6
73.4
75.2
77.0
78.8
80.6
82.4
84.2
30
8fi.O
87.8
89.6
!»1.4
93.2
95.0
For intermediate temperatures or those exceeding the range of the tables, the following for-
mulas may be used:
F - 32
F = 1.8XC + 32, C = ^ ^
ENGLISH SYSTEMS. ALL FIGURES ON A HORIZONTAL LINE ARE EQUIVALENT VALUES.
KILOGRAMS OF ONE GALLON OF WATER, FIND THE NUMBER ONE IN THE "GALLON"
METRIC COMPUTATIONS WERE BASED ON 1 LITER BEING THE VOLUME OF 1 KILO-
FLL II)
CLBIC
LITER OR
MILLILITER
OUNCE
METER
KILOGR.'^M
OR GRAM
OUNCE (WT)
POUND
33,854
1
1,000
1,000,000
35,273
2,205
1
33.85
0.001
1
1,000
35.27
2.204
(2)
0.034
—
0.001
1
0.035
0.002
(3)
25,853
0.764
764.5
764,559
26,937
1,683.6
(4)
957.5
0.028
28.317
28,322
997.7
62.428
(5)
128
0.004
3.785
3,785
133.4
8.335
(6)
32
0.001
0.946
946.2
33.34
2.084
(7)
16
—
0.473
473.1
16.67
1.042
(8)
15.36
—
0.454
453.6
16
1
(9)
1
0.03
29.57
1.042
0.065
(10)
0.96
0.028
28.35
1
0.062
(11)
0.554
0.016
16.37
0.577
0.036
(12)
0.034
—
0.001
1
0.035
0.002
(13)
B
Appendix
Ammonia Ionization
Table B-1. percent un-ionized ammonia (NH3) in aqueous ammonia
EMERSON l!t74. AQUEOUS AMMONIA EQUILIBRIUM CALCULATIONS, TECHNICAL
TEMPERATURE,°C
PH
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.00827
0.00899
0.00977
0.0106
0.0115
0.0125
6.1
0.0104
0.0113
0.0123
0.0134
0.0145
0.0157
6.2
0.0131
0.0143
0.0155
0.0168
0.0183
0.0198
6.3
0.0165
0.0179
0.0195
0.0212
0.0230
0.0249
6.4
0.0208
0.0226
0.0245
0.0267
0.0189
0.0314
6.5
0.0261
0.0284
0.0309
0.0336
0.0364
0.0395
6.6
0.0329
0.0358
0.0389
0.0422
0.0459
0.0497
6.7
0.0414
0.0451
0.0490
0.0532
0.0577
0.0626
6.8
0.0521
0.0567
0.0616
0.0669
0.0727
0.0788
6.9
0.0656
0.0714
0.0776
0.0843
0.0915
0.0992
7.0
0.0826
0.0898
0.0977
0.106
0.115
0.125
7.1
0.104
0.113
0.123
0.133
0.145
0.157
7.2
0.131
0.142
0.155
0.168
0.182
0.198
7.3
0.165
0.179
0.195
0.211
0.229
0.249
7.4
0.207
0.225
0.245
0.266
0.289
0.313
7.5
0.261
0.284
0.308
0.335
0.363
0.394
7.6
0.328
0.357
0.388
0.421
0.457
0.495
7.7
0.413
0.449
0.488
0.529
0.574
0.623
7.8
0.519
0.564
0.613
0.665
0.722
0.783
7.9
0.652
0.709
0.770
0.836
0.907
0.983
8.0
0.820
0.891
0.968
1.05
1.14
1.23
8.1
1.03
1.12
1.22
1.32
1.43
1.55
8.2
1.29
1.41
1.53
1.65
1.79
1.94
8.3
1.62
1.76
1.91
2.07
2.25
2.43
8.4
2.03
2.21
2.40
2.60
2.81
3.04
8.5
2.55
2.77
3.00
3.25
3.52
3.80
8.6
3.19
3.46
3.75
4.06
4.39
4.74
8.7
3.98
4.31
4.67
5.05
5.46
5.90
8.8
4.96
5.37
5.81
6.28
6.78
7.31
8.9
6.16
6.67
7.20
7.78
8.39
9.03
9.0
7.64
8.25
8.90
9.60
10.3
11.1
378
AMMONIA IONIZATION 379
SOLUTIONS. (SOURCE: THURSTON, ROBERT V., ROSEMARIE RUSSO, AND KENNETH
REPORT 74-1, MONTANA .STATE UNIVERSITY, BOZEMAN, MONTANA.
TEMPERATURE,°C
PH
6.0
7.0
8.0
9.0
10.0
11.0
6.0
0.0136
0.0147
0.0159
0.0172
0.0186
0.0201
6.1
0.0171
0.0185
0.0200
0.0217
0.0235
0.0254
6.2
0.0215
0.0233
0.0252
0.0273
0.0295
0.0319
6.3
0.0270
0.0293
0.0317
0.0344
0.0372
0.0402
6.4
0.0340
0.0369
0.0400
0.0432
0.0468
0.0506
6.5
0.0429
0.0464
0.0503
0.0544
0.0589
0.0637
6.6
0.0539
0.0585
0.0633
0.0685
0.0741
0.0801
6.7
0.0679
0.0736
0.0797
0.0862
0.0933
0.101
6.8
0.0855
0.0926
0.100
0.109
0.117
0.127
6.9
0.108
0.117
0.126
0.137
0.148
0.160
7.0
0.135
0.147
0.159
0.172
0.186
0.201
7.1
0.170
0.185
0.200
0.216
0.234
0.253
7.2
0.214
0.232
0.252
0.272
0.294
0.318
7.3
0.270
0.292
0.316
0.342
0.370
0.400
7.4
0.339
0.368
0.398
0.431
0.466
0.504
7.5
0.427
0.462
0.,501
0.542
0.586
0.633
7.6
0.537
0.582
0.629
0.681
0.736
0.796
7.7
0.675
0.731
0.791
0.856
0.925
1.00
7.8
0.848
0.919
0.994
1.07
1.16
1.26
7.9
1.07
1.15
1.25
1.35
1.46
1.58
8.0
1.34
1.45
1.57
1.69
1.83
1.97
8.1
1.68
1.82
1.96
2.12
2.29
2.47
8.2
2.10
2.28
2.46
2.66
2.87
3.09
8.3
2.63
2.85
3.08
3.32
3.58
3.86
8.4
3.29
3.56
3.84
4.15
4.47
4.82
8.5
4.11
4.44
4.79
5.16
5.56
5.99
8.6
5.12
5.53
5.96
6.42
6.91
7.42
8.7
6.36
6.86
7.39
7.95
8.54
9.17
8.8
7.88
8.48
9.12
9.80
10.5
11.3
8.9
9.72
10.5
11.2
12.0
12.9
13.8
9.0
11.9
12.8
13.7
14.7
15.7
16.8
380 kish hatchery management
Table B-1. continued.
TEMPERATURE,°C
pH
12.0
13.0
14,0
i:..()
16.0
17.0
(i.O
0.0218
0.0235
0.0254
0.0274
0.0295
0.0318
6.1
0.0274
0.0296
0.0319
0.0345
0.0372
0.0401
6.2
0.0345
0.0373
0.0402
0.0434
0.0468
0.0504
6.3
0.0434
0.0469
0.0506
0.0546
0.0589
0.0635
6.4
0.0547
0.0590
0.0637
0.0687
0.0741
0.0799
6.5
0.0688
0.0743
0.0802
0.0865
0.0933
0.101
6.6
0.0866
0.0935
0.101
0.109
0.117
0.127
6.7
0.109
0.118
0.127
0.137
0.148
0. 1 .59
6.8
0.137
0.148
0.160
0.172
0.186
0.200
6.9
0.173
0.186
0.201
0.217
0.234
0.252
7.0
0.217
0.235
0.253
0.273
0.294
0.317
7.1
0.273
0.295
0.319
0.344
0.370
0.399
7.2
0.344
0.371
0.401
0.432
0.466
0.502
7.3
0.433
0.467
0.504
0.543
0.586
0.631
7.4
0.544
0.587
0.633
0.683
0.736
0.793
7.5
0.684
0.738
0.796
0.859
0.925
0.996
7.6
0.859
0.927
1.00
1.08
1.16
1.25
7.7
1.08
1.16
1.26
1.35
1.46
1.57
7.8
1.36
1.46
1.58
1.70
1.83
1.97
7.9
1.70
1.83
1.98
2.13
2.29
2.47
8.0
2.13
2.30
2.48
2.67
2.87
3.08
8.1
2.67
2.87
3.10
3.33
3.58
3.85
8.2
3.34
3.59
3.87
4.16
4.47
4.80
8.3
4.16
4.48
4.82
5.18
5.56
5.97
8.4
5.19
5.58
5.99
6.44
6.91
7.40
8.5
6.44
6.92
7.43
7.97
8.54
9.14
8.6
7.98
8.56
9.18
9.83
10.5
11.2
8.7
9.84
10.5
11.3
12.1
12.9
13.8
8.8
12.1
12.9
13.8
14.7
15.7
16.7
8.9
14.7
15.7
16.8
17.9
19.0
20.2
9.0
17.9
19.0
20.2
21.5
22.8
24.1
AMMONIA IONIZATION 381
TEMPERATURE,°C
PH
18.0
19.0
20.0
21.0
22.0
23.0
6.0
0.0343
0.0369
0.0397
0.0427
0.0459
0.0493
6.1
0.0431
0.0465
0.0500
0.0.538
0.0578
0.0621
6.2
0.0543
0.0585
0.0629
0.0677
0.0727
0.0782
6.3
0.0684
0.0736
0.0792
0.0852
0.0916
0.0984
6.4
0.0860
0.0926
0.0997
0.107
0.115
0.124
6.5
0.108
0.117
0.125
0.135
0.145
0.156
6.6
0.136
0.147
0.158
0.170
0.183
0.196
6.7
0.172
0.185
0.199
0.214
0.230
0.247
6.8
0.216
0.232
0.250
0.269
0.289
0.310
6.9
0.272
0.292
0.315
0.338
0.364
0.390
7.0
0.342
0.368
0.396
0.425
0.457
0.491
7.1
0.430
0.463
0.498
0.535
0.575
0.617
7.2
0.540
0.582
0.626
0.673
0.723
0.776
7.3
0.679
0.731
0.786
0.845
0.908
0.975
7.4
0.854
0.919
0.988
1.06
1.14
1.22
7.5
1.07
1.15
1.24
1.33
1.43
1.54
7.6
1.35
1.45
1.56
1.67
1.80
1.93
7.7
1.69
1.82
1.95
2.10
2.25
2.41
7.8
2.12
2.28
2.44
2.63
2.82
3.02
7.9
2.65
2.85
3.06
3.28
3.52
3.77
8.0
3.31
3.56
3.82
4.10
4.39
4.70
8.1
4.14
4.44
4.76
5.10
5.47
5.85
8.2
5.15
5.53
5.92
6.34
6.79
7.25
8.3
6.40
6.86
7.34
7.86
8.39
8.96
8.4
7.93
8.49
9.07
9.69
10.3
11.0
8.5
9.78
10.5
11.2
11.9
12.7
13.5
8.6
12.0
12.8
13.7
14.5
15.5
16.4
8.7
14.7
15.6
16.6
17.6
18.7
19.8
8.8
17.8
18.9
20.0
21.2
22.5
23.7
8.9
21.4
22.7
24.0
25.3
26.7
28.2
9.0
25.5
27.0
28.4
29.9
31.5
33.0
382
FISH HATCHERY MANAGEMENT
Table B-1. continued.
TEMPERATURE,
°C
PH
24.0
25.0
26.0
27.0
28.0
29.0
30.0
6.0
0.0530
0.0569
0.0610
0.0654
0.0701
0.0752
0.0805
6.1
0.0667
0.0716
0.0768
0.0824
0.0883
0.0946
0.101
6.2
0.0839
0.0901
0.0967
0.104
0.111
0.119
0.128
6.3
0.106
0.113
0.122
0.130
0.140
0.1,50
0.160
6.4
0.133
0.143
0.153
0.164
0.176
0.189
0.202
6.5
0.167
0.180
0.193
0.207
0.221
0.237
0.254
6.6
0.211
0.226
0.242
0.260
0.279
0.299
0.320
6.7
0.265
0.284
0.305
0.327
0.351
0.376
0.402
6.8
0.333
0.358
0.384
0.411
0.441
0.472
0.506
6.9
0.419
0.450
0.483
0.517
0.554
0.594
0.636
7.0
0.527
0.566
0.607
0.651
0.697
0.747
0.799
7.1
0.663
0.711
0.763
0.818
0.876
0.938
1.00
7.2
0.833
0.894
0.958
1.03
1.10
1.18
1.26
7.3
1.05
1.12
1.20
1.29
1.38
1.48
1.58
7.4
1.31
1.41
1.51
1.62
1.73
1.85
1.98
7.5
1.65
1.77
1.89
2.03
2.17
2.32
2.48
7.6
2.07
2.22
2.37
2.54
2.72
2.91
3.11
7.7
2.59
2.77
2.97
3.18
3.40
3.63
3.88
7.8
3.24
3.47
3.71
3.97
4.24
4.53
4.84
7.9
4.04
4.33
4.63
4.94
5.28
5.64
6.01
8.0
5.03
5.38
5.75
6.15
6.56
7.00
7.46
8.1
6.26
6.69
7.14
7.62
8.12
8.65
9.21
8.2
7.75
8.27
8.82
9.40
10.0
10.7
11.3
8.3
9.56
10.2
10.9
11.6
12.3
13.0
13.8
8.4
11.7
12.5
13.3
14.1
15.0
15.9
16.8
8.5
14.4
15.3
16.2
17.2
18.2
19.2
20.3
8.6
17.4
18.5
19.6
20.7
21.8
23.0
24.3
8.7
21.0
22.2
23.4
24.7
26.0
27.4
28.8
8.8
25.1
26.4
27.8
29.2
30.7
32.2
33.7
8.9
29.6
31.1
32.7
34.2
35.8
37.4
39.0
9.0
34.6
36.3
37.9
39.6
41.2
42.9
44.6
Appendix
c
Volumes and Capacities of
Circular Tanks
Table C-1.
WATER VOLUMES (CUBIC FEET) AND CAPACITIES (US GALLONS) OF CIR-
CULAR TANKS FILLED TO A
1-FOOT DEPTH.
a,b,c
TANK
VOLUME
TANK
VOLUME
DIAMETER
(CUBIC
CAPACITY
DIAMETER
(CUBIC
CAPACITY
(FEET)
FEET)
(GALLONS)
(FEET)
FEET)
(GALLONS)
1.00
0.785
5.87
11.0
95.0
711
1.50
1.77
13.2
11.5
104
777
2.00
3.14
23.5
12.0
113
845
2.,W
4.91
36.7
12.5
123
918
3.00
7.07
52.9
13.0
133
993
3.50
9.62
72.0
13.5
143
1,070
4.00
12.6
94.0
14.0
154
1,1,50
4.50
15.9
119
14.5
165
1,240
5.00
19.6
147
15.0
177
1,320
5.50
23.8
178
15.5
189
1,410
6.00
28.3
212
16.0
201
1,.500
6.50
33.2
248
16.5
214
1,600
7.00
38.5
288
17.0
227
1,700
7.. 50
44.2
330
17.5
241
1,800
8.00
.50.1
376
18.0
254
1,900
8.50
56.8
424
18.5
269
2,010
9.00
63.6
476
19.0
284
2,120
9.50
70.9
530
19.5
299
2,230
10.0
78.5
588
20.0
314
2,3.50
10.5
86.6
641
For water depths less or greater than 1 foot, multiply the tabulated volumes and capacities
by the actual depth in feet.
For tanks larger than 20 feet in diameter, multiply the volume and capacity of a tank
one-half its diameter by four. A 30-foot diameter tank, for example, has a volume of four
times the volume of a 15-foot tank.
For intermediate tank sizes, volume = 3.14 x ( -j diameter) x water depth; capacity =
volume X 7.48.
383
Appendix
D
Use of Weirs to Measure
Flow
The discharge of water through a hatchery channel can be measured easily
if a Cippoletti or a rectangular weir (Figure D-l) is built into the channel.
The only measurement needed is that of the water head behind the weir;
the head is the height the water surface above the crest of the weir itself.
Reference of this head to a calibration chart (Table D-l) gives the
corresponding discharge in gallons per minute.
Water-flow determinations will be inaccurate if the head is measured at
the wrong point or if the weir has not been constructed carefully. The fol-
lowing considerations must be met if weir operation is to be successful.
(1) The head must be measured at a point sufficiently far behind the
weir. Near the weir, the water level drops as water begins its fall over the
weir crest. The head never should be measured closer to the weir than
2 2 times the depth of water flowing over the crest. For example, if 2
inches of water are flowing over the weir crest, the head should be meas-
ured 5 inches or more behind the weir. A practical measuring technique is
to drive a stake into the channel bottom so that its top is exactly level with
the weir crest. Then, the head can be measured with a thin ruler as the
depth of water over the stake. A ruler also can be mounted permanently on
the side of a vertical channel wall behind the weir, if such a wall has been
constructed.
(2) The weir crest must be exactly level and the weir faces exactly verti-
cal, or the standard head-to-discharge calibrations will not apply.
384
WEIRS
385
HOLES FOR lOd
GALVANIZED NAILS
AT 4" 4"0.C
Figure D-1. (Top) Diagram of a Cippoletti weir plate. It should be cut from
No. 8 or No. 10 galvanized iron plate. The trapezoidal notch must be cut to the
exact dimensions as shown. Flov^ rates with this weir will be twice the values
shown in Table D-1. (Bottom) A rectangular weir installed to measure water
flow at the discharge of a fish hatchery. A sight gauge (insert) with a float in an
aluminum cylinder is used to measure water depth over the crest of the weir. It
must be positioned at a distance at least 2.5 times the depth of the water flowing
over the weir.
386 fish hatchery management
Table D-1. relation between head and discharge for cippoletti and rec-
tangular WEIRS, discharge VALUES ASSUME A 1-FOOT-LONG WEIR CREST; FOR
SHORTER OR LONGER CRESTS, MULTIPLY THESE VALUES BY THE ACTUAL LENGTH
IN FEET.
DISCHARGE
DISCHARGE
DISCHARGE
HEAD
(GALLONS
HEAD
(GALLONS
HEAD
(GALLONS
(INCHES)
PER MINUTE)
(INCHES)
PER MINUTE)
(INCHES)
PER MINUTE)
0.250
5.00
4.25
317
8.25
860
0.500
14.0
4.50
346
8.50
900
0.7,50
23.0
4.75
375
8,75
939
1 .00
36.0
5.00
405
9.00
978
1.25
50.0
5.25
436
9.25
1,020
1.50
(ifi.O
5.50
468
9.50
1 ,060
1.75
84.0
5.75
500
9,75
1,100
2.00
102
fi.OO
533
10.0
1,150
2.25
122
6.25
567
10.3
1,190
2.,50
143
6.50
601
10.5
1,230
2.75
165
6.75
636
10.8
1,280
3.00
188
7.00
672
11.0
1,320
3.25
212
7.25
708
11.3
1,370
3.50
237
7.50
745
11.5
1,410
3.75
263
7.75
783
11.8
1,460
4.00
290
H.OO
820
12.0
1,510
(3) The weir crest, formed with a metal plate, must be leak- proof, sharp
or square-edged, and no thicker than ^-inch. The distance of the weir
crest above the bottom of the channel should be at least 2- times the water
head on the weir to minimize approach water velocities.
(4) Air must have access to the underside of falling water as it flows over
the weir crest. Otherwise, air pressure may force water against the down-
stream face of the weir, increasing the rate of discharge above the flow
rates indicated in Table D-1.
(5) The channel above the weir must be straight, level, and clean to
ensure smooth water flow. Sediment and debris should not be allowed to
collect on or behind the weir.
Appendix
E
Hatchery Codes for
Designating Fish Lots
Table E-1. codes for United States national fish hatcheries.
CODE
HATCHERY
CODE
HATCHERY
Ab
Abernathy, Washington
Cf
Crawford, Nebraska
Ac
Alchesay, Arizona
Ct
Creston, Montana
Al
Allegheny, Pennsylvania
DH
Dale Hollow, Tennessee
BD
Bs
Baldhill Dam. North Dakota
Berkshire, Massashusetts
Dt
Ds
Dexter, New Mexico
Dworshak, Idaho
Bl
Bd
Bm
Berlin, New Hampshire
Bowden, West Virginia
Bozeman, Montana
EC
Ed
En
Eagle Creek, Oregon
Edenton, North Carolina
Ennis, Montana
Et
Entiat, Washington
CH
Carbon Hill, Alabama
Ew
Erwin, Tennessee
Cs
Carson, Washington
Cd
Cedar Bluff, Kansas
Ff
Frankfort, Kentucky
CF
Chattahoochee Forest, Georgia
Cr
Cheraw, South Carolina
GD
Garrison Dam, North Dakota
Ch
Cohutta, Georgia
GP
Gavins Point, South Dakota
Cm
Coleman, California
Gn
Genoa, Wisconsin
Cn
Corning, Arkansas
GL
Green Lake, Maine
CB
Craig Brook, Maine
GF
Greers Ferry, Arkansas
387
388
USH HATCHERY MANAGEMENT
Table E-1. continued.
CODE
HATCHERY
CODE
HATCHERY
Hg
Hagerman, Idaho
HL
Harrison Lake, Virginia
Hb
Hebron, Ohio
HF
Hiawatha Forest, Michigan
Hk
Hotchkiss, Colorado
ID
Inks Dam, Texas
IR
Iron River, Wisconsin
Js
Jackson, Wyoming
JH
Jones Hole, Utah
JR
Jordan River, Michigan
Kk Kooskia, Idaho
Lh Lahontan, Nevada
LM Lake Mills, Wisconsin
Lm Lamar, Pennsylvania
Lv Leadville, Colorado
Le Leavenworth, Washington
Lt Leetown, West Virginia
LW Little White Salmon, Washington
Mk Makah, Washington
MS Mammoth Springs, Arkansas
MN McNenny, South Dakota
ML McKinney Lake, North Carolina
Mr Meridian, Mississippi
Ms Mescalero, New Mexico
MC Miles City, Montana
MI Millen, Georgia
Ns Nashua, New Hampshire
Ni Natchitoches, Louisiana
NL New London, Minnesota
No Neosho, Missouri
Nf Norfork, Arkansas
NA North Attleboro, Massachusetts
Or Orangeburg, South Carolina
PB Paint Bank, Virginia
PC Pendills Creek, Michigan
PF Pisgah Forest, North Carolina
Pf Pittsford, Vermont
Qc Quilcene, Washington
Qa Quinauit, Wahington
SM San Marcos, Texas
Sr Saratoga, Wyoming
Sn Senecaville, Ohio
Sf Spearfish, South Dakota
SC Spring Creek, Washington
TC Tehama Colusa, California
Ts Tishomingo, Oklahoma
Tp Tupelo, Mississippi
Uv Uvalde, Texas
VC Valley City, North Dakota
Wh Walhaila, South Carolina
Wm Warm Springs, Georgia
WS Warm Springs, Oregon
Wl Welaka, Florida
WR White River, Vermont
Ws White Sulphur Springs,
West Virginia
Wd Wiilard, Washington
WC Williams Creek, Arizona
WB Willow Beach, Arizona
Wt Winthrop, Washington
Wk Wolf Creek, Kentucky
Wv Wytheville, Virginia
Yk Yakima, Washington
HAICHKRY CODES
389
Table E-2. two-letter state abbreviations.
AL
Alabama
AK
Alaska
AZ
Arizona
AR
Arkansas
CA
California
CO
Colorado
CT
Connecticut
DE
Delaware
DC
District of Columbia
FL
Florida
GA
Georgia
GU
Guam
HI
Hawaii
ID
Idaho
IL
Illinois
IN
Indiana
lA
Iowa
KS
Kansas
KY
Kentucky
LA
Louisiana
ME
Maine
MD
Maryland
MA
Massachusetts
MI
Michigan
MN
Minnesota
MS
Mississippi
MO
Missouri
MT
Montana
NB
Nebraska
NV
Nevada
NH
New Hampshire
NJ
New Jersey
NM
New Mexico
NY
New York
NC
North Carolina
ND
North Dakota
OH
Ohio
OK
Oklahoma
OR
Oregon
FA
Pennsylvania
PR
Puerto Rico
RI
Rhode Island
SC
South Carolina
SD
South Dakota
TN
Tennessee
TX
Texas
UT
Utah
VT
Vermont
VA
Virginia
VI
Virgin Islands
WA
Washington
wv
West Virginia
WI
Wisconsin
WY
Wyoming
Appendix
F
Nutritional Diseases and
Diet Formulations
Table F-1. nutritional diseases in eish. ihe following is presented as a
diagnostic guide. all signs observed in eish are lumped together and
some disorders may not apply to a particular fish species. (source:
HORAK I97r).)
NUTRIENI'
Protein
Crude pi u It in
Amino acids
Fat
SIGNS OF DEFICIENCY OR EXCESS
Signs of deficiency; poor growth; reduced activity; fish remain near
the water surface; increased vulnerability to parasites.
Signs of excess: moderate to shght growth retardation.
Signs of deficiency: deficiency of any essential amino acid can cause
reduced or no growth; lens cataract may result from a deficiency of
any essential amino acid except arginine; lordosis or scoliosis may
result from less than ().2".i tryptophan in the diet; blacktail syn-
drome, loss of equilibrium will result from less than 0.8"ii lysine in
the diet.
Signs of excess: inhibited growth results from excess leucine; dietary
inefficiency may result from extreme ratios of phenylalanine to
tyrosine, high levels of either phenylalanine or tyrosine, and valine
greater than 3"ii.
Signs of deficiency: poor growth, as essential amino acids must be
used for energy; necrosis of the caudal fin; fatty pale liver; fin ero-
sion; dermal depigmentation; edema; increased mitochondrial swel-
ling; mortality; stress- induced violent swimming motion with little
forward movement, followed by motionless floating for 1,') minutes
before recovery; slightly reduced hemoglobin; anemia; liver and
kidney degeneration; soreback; high mortality may occur from corn
or soy oil in diets at near-freezing temperatures.
Signs of excess: plugged intestine; liver and kidney degeneration;
death may result from hard fat (beef); pale, swollen, yellow-brown.
390
nutritional diseases and diets 391
Table F-I. continued.
NUTRIENT SIGNS OF DEFICIENCY OR EXCESS
Fat [continued) fatty infiltrated liver; pigmented insoluble fat (ceroid) in liver;
water edema; amenia; fattv infiltrated kidney and spleen; reduced
weight gain with no increase in carcass fat.
Carbohydrate Signs of deficency: reduced survival of stocked fish; decreased liver
glycogen from carbohydrate-free diet; slow growth, as amino acids
are used for energy.
Signs of excess: glycogen-infiltrated, pale, swollen liver; fatty-
infiltrated kidneys; degenerated pancreatic islets; poor growth;
edema; elevated blood glucose; death from overfeeding or from
digestible carbohydrate greater than 20" of diet.
Vitamins
Vitamin A Signs of deficency: serous fluid in abdominal cavity; edema; ex-
ophthalmus; hemorrhage of anterior chamber of the eye, base of
fins, and kidne%s; light-colored body; poor appetite; poor growth;
eye cataracts; anemia; drying and hardening of mucous-secreting
tissue; clubbed gills; high mortalit) ; bent gill operculum. (Vitamin
A is destroyed by rancid fats.)
Signs of excess: enlargement of liver and spleen; retarded growth;
skin lesions; epithelial keratinization; abnormal bone formation and
fusion of vertebrae; necrosis of caudal fin; elevated levels of body
fat and cholesterol; lowered hematocrit.
Vitamin D Signs of deficency: elevated feed conversion; slightly increased
number of blood cells; impaired absorption of calcium and phos-
phorous from intestine.
Signs of excess: impaired growth; decalcification, especially of ribs;
lethargy; dark coloration; ele\ated blood serum calcium caused by
doses of D3.
Vitamin E Signs of deficency: serous fluid in abdominal cavity; ceroid in liver,
spleen, and kidney; fragility of red blood cells; poor growth; poor
food conversion; cell degeneration; sterility; excessive mortality;
clubbed gills; soreback; general feed rancidity, as vitamin E is a
strong antioxidant. Vitamin E is involved with selenium and vita-
min C for normal reproduction, and may be involved with embryo
membrane permeability and hatchability of fish eggs. It is des-
troyed by rancid fats. Fortification of E can prevent anemia caused
by rancidity of the feed.
Signs of excess: no growth; toxic liver reaction; death; accumulation
of vitamin E in ovary.
Vitamin h Signs of deficency: anemia; pale liver, spleen, and gills; hemorrhagic
gills, eyes, base of fins, and vascular tissues; death.
Signs of excess: none.
Thiamine (B^) Signs of deficiency: poor appetite; muscle atrophy; vascular degenera-
tion; con\ulsions; rolling whirling motion; extreme ner\ousness and
no recovery from excitement; instability and loss of equilibrium
weakness; edema; poor appetite; poor growth; retracted head
sometimes a purple sheen to the body; melanosis in older fish
excessive mortality; anemia; corneal opacities; paralysis of dorsal
and pectoral fins.
392
FISH HATCHERY MANAGEMENT
Table F-1. continued
NUTRIENT
SIGNS OF DEFICIENCY OR EXCESS
Vitamins (continued)
Riboflavin (B2)
Pyridoxine (Bf)
Pantothenic acid
Biotin
Choline
Vitamin B12
Niacin
Ascorbic acid
(vitamin C)
Signs of excess: none.
Signs of deficiency: corneal vascularization; cloudy lens and cataract;
hemorrhagic eyes, nose, or operculum; photophobia; incoordina-
tion; abnormal pigmentation of iris; striated constructions of
abdominal wall; dark coloration; poor appetite; anemia; complete
cessation of growth; dermatitis; high mortality.
Signs of excess: none.
Signs of deficiency: nervous disorders; epileptiform convulsions;
hyperirritability; alexia; loss of appetite; edema of peritoneal cavity
with colorless serous fluid; rapid onset of rigor mortis; rapid jerky
breathing; flexing of opercles; iridescent blue-green coloration on
back; heavy mortality; retarded growth; indifference to light. (A
high tryptophan diet increases requirement for pyridoxine.)
Signs of excess: none.
Signs of deficiency: clubbed gills; necrosis; scarring and cellular atro-
phy of gills; gill exudate; general "mumpy" appearance; eroded
opercles; pinhead; prostration; loss of appetite; lethargy; poor
growth; high mortality; eroded fins; disruption of blood cell forma-
tion.
Signs of excess: none.
Signs of deficiency: loss of appetite; lesions in colon; dark coloration
(blue slime film that sloughs off in patches); muscle atrophy; spas-
tic convulsions; anemia; skin lesions; reduced stamina; contracted
caudal fin; poor growth; elevated feed conversion; small liver size;
abnormally pale liver.
Signs of excess: depression of growth; excessive levels can be coun-
teracted by adding folic acid or niacin.
Signs of deficiency: poor food conversion; hemorrhagic kidney and
intestine; exophthalmia; extended abdomen; light-colored body;
poor growth; fatty infiltrated livers; increased gastric emptying
time; anemia.
Signs of excess: none.
Signs of deficiency: Poor appetite; erratic and low hemoglobin; frag-
mentation of erythrocytes with many immature forms; protein
metabolism disruption; poor growth; poor food conversion.
Signs of excess: none.
Signs of deficiency: loss of appetite; poor food conversion; lesions in
colon; jerky or difficult motion; weakness; reduced coordination;
mortality from handling stress; edema of stomach and colon; mus-
cle spasms while resting; tetany; sensitivity to sunlight and sun-
burn; poor growth; swollen but not clubbed gills; flared opercles;
anemia; lethargy; skin hemorrhage; high mortality.
Signs of excess: none.
Signs of deficiency: scoliosis; lordosis; abnormal opercles; impaired
formation of collagen; impaired wound healing; abnormal cartilage;
twisted, spiraled, deformed cartilage of gill filaments; clubbed gills;
hyperplasia of jaw and muscle; deformed vertebrae; eye lesions;
NUTRITIONAL DISEASES AND DIETS 393
Table F-1. continued.
NLTRItM SIGNS UF DEFICIENCV OR EXCESS
Vitamins [continued] hemorrhagic skin, hver, kidney, intestine, and muscle; retarded
growth; loss of appetite; increased mortality; eventual anemia.
Signs of excess: none.
Folic acid Signs of deficiency: lethargy; fragility of fins, especially caudal; dark
(vitamin H) coloration; reduced resistance to disease; poor growth; no appetite;
infraction of spleen; serous fluid in abdominal cavity; sluggish
swimming; loss of caudal fin; exophthalmia.
Signs of excess: none.
Inositol Signs of deficiency: distended stomach; increased gastric emptying
time; skin lesions; fragile fins; loss of caudal fin; poor growth; poor
appetite; edema; dark color; anemia; high mortality; white-colored
liver.
Signs of excess: none.
Minerals Signs of deficiency: hyperemia on floor of mouth; protrusions at bran-
chial junction; thryoid tumor; exophthalmia; renal calculi (kidney
stones).
Signs of excess: scoliosis; lordosis; blacktail; eroded caudal fin; mus-
cular atrophy; paralysis if there is dissolved lead in the water at 4-8
parts per billion (no toxic effects with lead up to 8, ()()() parts per
million in dry feed); growth retardation; pigmentation changes
when copper is greater than 1 mg/g in dry diet (lOO to 200 times
the daily requirement).
Toxins and chemicals Signs of deficiency: none.
Signs of excess: Hepatocellular carcinoma after 1220 months with
tannic acid at 7. ,1^480 mg/100 g in dry feed; loss of appetite;
grossly visible sundan-ophilic substance in liver; decreased availa-
bility of lysine when greater than 0.04".. free gossypol (yellow pig-
ment from glands of cottonseed meal) is in feed; trypsin inhibition
resulting from low heat-treated soybean meal; liver cell carcinomas;
pale yellow or creamy-colored livers; gill epithelium disruption
resulting from aflatoxin-contaminated oilseed meals (especially cot-
tonseed) with as little as 0.1-0..T parts per billion aflatoxin Bl, or
7.,T mg carbarson/lOO g dry feed; feed with greater than 13".. mois-
ture encourages mold growth which produces the toxin; gill disease
resulting from DDT at 7. ,5 mg/100 g dry diet; cataract caused by
30 mg/100 mg dry diet of thioacetamide for 12 months; broken-
back syndrome; retarded growth produced by toxaphene in water
at greater than 70 parts per thousand; retarded ammonia detoxica-
tion enzymes affected by dieldrin greater than 0.36 parts per mil-
lion in feed; inhibited mobilization of liver glycogen and Cortisol
production in fish under stress and endrin greater than 0.2 in feed;
stimulated thyroid when greater than 0.8 parts per million DDT or
2.0 parts per million DDE is in feed, or 2,4-D in the water; lowered
egg hatching; abnormal fry anemia; mortality; reduced growth;
dark, lethargic fish when greater than 0.2-0..'i parts per million Aro-
clor 12,54 is in feed; yellow-colored flesh when ()"« corn gluten meal
is in feed.
394
FISH HAI'CHERY MANAGEMENT
Table F-2. dry trout feeds developed by the US fish and wh.dijfe serv-
ice. VALUES are percent OF FEED BY WEIGHT. MP = MINIMUM PROTEIN.
INGREDIENT
STARTER
DlEr
SD 7
FINGERLING DIETS
PR fi
PR y
PRODUCTION
DIET
PR 11
Fish meal (MP 60",,)
Soybean meal, dehulled seeds
Flour (MP .SO",,)
Meal (MP 47.5",,)
Corn gluten meal (MP 60";,)
Wheat middlings, standard
Yeast, dehydrated brewer's or torula
Blood meal (MP 80",,)
Whey, dehydrated
Fish solubles, condensed (MP 50" „)
Fermentation solubles, dehydrated
Alfalfa meal, dehydrated
Soybean oil
Fish oil
Vitamin premix no. 30
Choline chloride, 50%
Mineral mixture
4.5
34
35
\5
10
20
6
9.35
li).3
13.3
5
5
5
5
5
10
10
5
8
8
3
3
10
4
5
0.4
0.4
0.4
0.2
0.2
0.2
O.O.T
0.1
0.1
26
25
17.3
5
10
8
3
5
0.4
0.2
0.1
"See Table F «.
Mineral mixture (grams per pound)
MnS04, 94; KIO^, 0.38; inert carrier, 251.37.
ZnS04, 84; FeS04- 7H2O, 22.5; CUSO4, 1.75;
nu tritional. diseases and dieis 395
Table F-3. dry trout feeds developed by Colorado division of wildlife,
values are precent of feed by weight. mp = minimum protein.
STARTER DIETS FINCERLING DIETS REGULAR
PRODUCTION
INGREDIENTS SD 3 SD 3A PR 4 PR 4A DIP. I
Fish meal (MP 60"..) 37 42 31 35 27
Soybean meal, dehulled seeds
Flour (MP 50%) 5
Meal (MP 47.5"..)
Corn gluten meal (MP 60".,)
Wheat middlings, standard 13.8 1.3 19.8 l.xH 23.8
Wheat germ meal 5
Yeast, dehydrated brewer's 4.5 7 3.5 5.5 10
Blood meal (MP 80'..) 7 2 3 2.5
Whey, dehydrated
10
10
5
5
(i
13.8
1.3
19.8
l.x8
4.5
7
3.5
5.5
7
2
3
10
10
10
U)
,T
5
8
8
3
3
8
8
Fi
8
8
4
4
0.5
0.5
0.5
0.5
0.2
0.2
0.2
0.2
1
1
2
2
''See Table F-8.
Maximum zinc content 0.005"ii.
10
Fish solubles, condensed 5 10
Fermentation solubles, dehydrated 5 5 8 8 6.5
Alfalfa meal, dehydrated
Poultry feathers, hydrolyzed
Fish oil 8 8 4 4 3.5
Vitamin premix no. 30" 0.5 0.5 0.5 0.5 0.5
Cholme chloride 0.2 0.2 0.2 0.2 0.2
Salt, trace mineralized 112 2 1
'Md
(ISM MAM MlJ'.y MANAOKMKNf
iMU.t. F i. I>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
0 1
0.4
0.2
0.2
0.1
.•i4
10
4
0.4
0.2
0.1
u ir,'' III ■.^iliii'iii I'-i-
•(Is ;it a
See l.il'l' I '' lii'iMl") iriir.l I" .I'I'I' il I', llii ■;il.iiiiiii |)i'iiir.
level i)( H I'l.iiir, pel |)i)iiii'l nl |iii im •
'Miiii'i.iI iiiixIiik- 'i',i,iiir, |i' I |.miiir|/ /)i,S(>»,(, HI; l'L-,'5U,(' 711^0, 22..'); CU.SU4, 1,7.'>;
MiiSO,,, Ml, KIOj, 0,:iH, lll'll '.iiii'i, 2,".l,:'.7,
NT I Kl I l( )\ \l 1)1 MASKS WlilMI l\ 1")7
TAHI.I, V-Fy. MOIST SALMON M.KDS Dl.Vl.l.OI'l.l) in OKIa;ON SIAIK UNIVLKSin AND
oKi:(;oN nirvKiMiM oi iisii and wiimiii \ \m is aki nun ni (H iim> ii\
wtiGHi.
OKH.dN (ilU(.i)N
SIAKIIK MAUIIK
MASM IM-,l,l,in
INGREnilNI (»M I (ir i
Meal mix
Mi'itini; meal IH
rish inci.l'' 2!»
Wheat genu me.il 10 4
Whey, dehydrated 10 rt
Cottonseed inciil, di Imllrd 17
Shrini|) <>i c tab meal 4
Com distiller's dried solubles 3
Vitamin premix*^ l..'> l.Ti
Wet mix
I una viseera 10
I'urbot, salmon visteia, liemng^ 10
Wet fish'' 30
Hcirmnnir 10 (i.O
Choline chloride (liquid, 70".. iiuhIik () ()..') O.Fi
Miiimniiii /•)' [iiniciii, rn.ixiiiHini .'i"'i NaC'l.
Herring meal (minimum 70". i prnlrui, mnsminm .'i"n NaCi) must be used as !()()"" ol the
fish meal in earh batch of ' -, ^^ -, and ^^ mk Ii jiellels, and at no less than fit)"" of the fish
miid m each batch of large pellets. Make (minimum (>K"" protein), anchovy (domestic or
J'eruvi;iii, miiniinim Grj"/!! protein), or menhaelen (mitiirinmi Mt |prn(cjiil m;iy be used as the
remaining poilion of the fish meal (or larger pellets, provided (he liilal lisli meal is increased
to M)"" of the diet (31"" if menhaden us used).
"^Prepress solvent-extracted; minimum 4K.,'J"" protein, maximum 0 O.'i.V'n free gossypid.
Maximum IV'/n NaCI; muiiriinrii /V' ptoicin (not (onnted as (isli meid in piolein i all ulti
tions
Sec Table I' H, Oregon salmon premix.
^No heads or gills; with livers, pasteurized.
^Turbot, pasteurized salmon viscera (no heads or gills), or pasteuri/.ed heriing.
Limited to tuna viscera, herring, "l)r)tlom fish" (whole or fillet scrap), salmon viscera, dog-
fish, and hake, with the following provisions: (l) two or more must be used in combination,
with no one exceeding l.VJ^i of the total diet; (2) ■- - and ;;7-inch pellets shall contain at least
7.,'>"'ii tuna viscera, but no fillet scrap.
'.Stabilized with 0.,r;. BMA lUIT (l:l); less than IIO".. free fatty acids, and m-t alkaline
reprocessed.
398
FISH HATCHERY MANAGEMENT
Table F-6. dry catfish feeds, values are precent of feed by weighi. mp =
MINIMUM protein.
feeds''
INGREDIENTS
1
2
3
4
Fish meal (MP 60"n)
10
10
12
Soybean meal, dehulled seeds
(MP 44%)
26
52
35
(MP 49"o)
20
Corn gluten meal (MP 60"..)
20
Wheat middlings, standard
IS)
Blood meal (MP H()"„)
3
5
Alfalfa meal, dehydrated
3.4
Meat and bone meal
15
Corn, yellow, dent
21.4
28.65
Distillers dried grains with sol
ubles
5
Dried distillers solubles
7.5
8
Rice bran
25
Rice mill dust
10
Wheat, grain, ground
24.9
5
Cottonseed meal, dehulled (MP 48.5':n)
10
Feather meal
5
Animal tallow
1.5
2
2.5
Dicalcium phosphate
4.5
1
3
Trace mineralized salt
0.5
0.5
0.25
1
Vitamin premix
0.5
0.5
0.5
0.5
Choline chloride, 5()"(i
0.1
0.1
0.1
0.1
Feed 1 was developed by the departments of Biology and Grain Science, Kansas State
University. Feed 2 was developed by the Department of Fisheries and Allied Aquacultures,
Auburn University. Feed 3 was developed by the Skidaway Institute of Oceanography and
Coastal Plain Station, Savannah, Georgia. Feed 4 was developed by the US Fish and Wildlife
Service's Fish Farming Experimental Station, Stuttgart, Arkansas.
See Table F-8, catfish premix.
NUTRITIONAL DISEASES AND DIETS
399
Table F-7. coolwater dry fish feed (w-7) developed for fry and finger-
lings BY the us fish and wildlife service, vall'es are percent of feed by
weight. MP = minimum protein.
INGREDIENTS
W-7
Fish meal (MP (i5"„)
Soybean flour, dehulled seeds (MP 48.,'j"(i)
VV'heat middlings, standard
Fish solubles, condensed (MP 50%)
Blood meal (MP 80",i)
Yeast, dehydrated brewer's
Whey, dehydrated
Fish oil
Vitamin premi.x no. 30
Choline chloride, 50"o
.50
10
5.1
10
5
5
5
9
0.6
0.3
See Table F 8. Vitamin premix (no. 30) is used at 1.5> the level used in trout feeds.
Table F-8. specifications for vitamin premixes for catfish, trout, and
salmon feeds, values are amounts per pound of premix".
CATFISH
TROUT
OREGON SALMON
vitamin
UNITS
PREMIX
PREMIX NO. M)
PREMIX
Vitamin A
lU
500,000
750,000
Vitamin B
lU
90,000
50,000
Vitamin E
lU
4,(S00
40,000
15,200
Vitamin K^
mg
900
1,2.50
545
Ascorbic acid
g
9
75
27
Biotin
mg
10
40
18
Bl2
mg
2
2.5
1.8
Folic acid
mg
4(i0
1,000
385
Inositol
g
9
8
Niacin^
g
9
25
5.7
Pantothenate
g
10
12
3.2
Pyridoxine
mg
1,800
3,500
.535
Riboflavin
g
1.8
6
1.6
Thiamine-'
mg
1,800
4,000
778
"Diluent used to bring the total amount to one pound must be a cereal product.
Levels in this vitamin premix are calculated to supply the recommended amounts in a
complete feed.
Palmitate or acetate.
Stabilized.
Alpha tocopherol acetate.
Menadione sodium bisulfite complex.
■^Niacinamide.
fi , .
D-calcium.
'HCl.
Mononitrate.
400
FISH HATCHERY MANAGEMENT
Table ¥-9. recommended amounts of vitamins in fish feeds, values are
amounts per pound of feed, and include total amounts from
ingredients AND VITAMIN PREMIXES". (SOURCE: NATIONAL ACADEMY OF SCI-
ENCES.)
VVARMWATER FISH FEEDS
SUPPLEMENTAL
COMPLETE
SALMONID
VITAMIN
UNITS
DIET
DIET
FEEDS
Vitamin A
lU
1,000
2,500
1 ,000
Vitamin D3
lU
100
450
R*
Vitamin E
lU
5
23
15
Vitamin K
mg
2.3
4.5
40
Ascorbic acid
mg
23
45
50
Biotin
mg
0
0.05
0.5
B12
mg
0.005
0.01
0.01
Choline
mg
200
250
1,500
Folic acid
mg
0
2.3
2.5
Inositol
mg
0
45
200
Niacin
mg
13
45
75
Pantothenic acid
mg
5
50
20
Pyridoxine
mg
5
9
5
Riboflavin
mg
3
9
10
Thiamine
mg
0
9
5
These amounts do not allow for processing or storage losses but give the total vitamins
contributed from all sources. Other amounts may be more appropriate under various condi-
tions
b
R = required, amount not determined.
Requirement is affected directly by the amount and type of unsaturated fat fed.
G
Appendix
Chemical Treatments:
Calculations and Constant
Flow Delivery
Hatchery systems often receive prolonged- bath or constant-flow chemical
treatments that adjust water quality or control diseases. In prolonged-bath
treatments (without water flow), chemicals are spread over the surface of
the water body, and mixed throughout its volume, by hand or machine.
Many hatchery tanks and most ponds, particularly large ones, are treated
statically. In constant-flow treatments, chemicals are metered at one point
into continously renewed water supplies; the turbulence of the moving
water accomplishes the mixing. Constant-flow treatments typically are used
in intensive culture when even a temporary halt in the supply of fresh
water might cause fish mortality because of oxygen depletion or waste
accumulation.
Chemical applications normally are couched in terms of final concentra-
tions; a pond treatment of 2 parts per million rotenone means the whole
pond should contain this concentration after application. Concentrations,
in turn, typically are weight ratios: weight of chemical in solution (or
suspension) per weight of solvent (usually water). The ratio may be
expressed in terms either of unit solvent weight or of unit solute weight.
Ten pounds chemical per ton of water, and one pound chemical per 200
pounds water (l:200), both represent the same concentration. Even when a
concentration is expressed in terms of volume or capacity (pounds/acre-
foot; milligrams/liter), it is the equivalent weight of that volume of water
that is implied.
401
402 FISH HAICHKRY MANAGEMENT
Calculations for Prolonged-Bath Treatments
The basic formula for computing the amount of chemical needed is:
capacity final
(volume) of concentration correction
water to x desired x factor . , .
, \ weight of
be treated Ippmj , . ,
— = chemical
strength of chemical (decimal) needed
The units of measure and the correction factor (Table G-l) that correlates
volume with weight vary with the size of the unit to be treated. The chem-
ical strength is the fraction of a chemical preparation that is active in-
gredient when purchased; ppm is parts per million.
For example, in smaller hatchery units, gallon capacities usually are
used. Chemicals typically are measured in grams because small amounts
are usually needed, and metric balances are more accurate than English
ones in this range. The correction factor is 0.0038 (grams/gallon).
Examples:
(1) How much Dylox (50"(i active ingredient) is needed for a 0.25 ppm
treatment of a 390-gallon tank?
390x0.25x0.0038 ^ ^,
= 0.74 erams Uyiox
0.50 ^ ^
(2) How much copper sulfate (lOO'/o active ingredient) is needed for a
1:6,000 treatment of that 390-gallon tank?
390x167x0.0038 ^,^ ^ ^^
=- 247 grams CuSO.
1.00 ^ *
Table G-1. correction factors used to convert volume or capacity to
WEIGHT IN calculations OF CHEMICAL CONCENTRATION.
Units Correction Factor
grams (or milliliters)/gaIlon 0.00378
grams (or milliliters)/cubic foot 0.02828
grams (or milliliters)/cubic yard 0.76366
ounces (fluid)/cubic foot 0.00096
ounces (nuid)/cubic yard 0.0258.'i
ounces (weight)/cubic foot 0.00100
ounces (weight)/cubic yard 0.02694
pounds/cubic foot 0.00006
pounds/cubic yard 0.00168
pounds/acre-foot 2.7181
CHEMICAL TREATMENTS 403
For ponds, volumes usually are known in acre-feet (surface area in acres
X average depth in feet). Relatively large amounts of chemicals are
needed for treatment, and these usually can be weighed in pounds. The
correction factor is 2.7 (pounds/acre- foot per part per million).
Example: How much of chemical A (60"() active ingredient) is needed
for a 2-ppm treatment of a 2.0-acre pond that averages 2.5 feet deep?
Volume = 2.0 acres x 2.5 feet = 5.0 acre-feet;
5.0X2.0X2.7 ^, , r . ■ , A
= 45 pounds oi chemical A
0.60
Calculations for Constant-Flow Treatments
The weight of chemical needed for constant-flow treatments is computed
just as for prolonged-bath treatments. However, in this case the volume
(capacity) of water to be treated is equal to the flow rate times the treat-
ment time (for example, 10 gallons per minute x 30 minutes). Correc-
tion factors are the same. The formula is:
flow treatment final correction
rate x time x concentration x factor weight of
= chemical
chemical strength (decimal fraction) needed
Example: A trough receiving a water flow of six gallons per minute is to
receive a 1-hour (60-minute) constant-flow treatment of chemical B (lOO%
active strength) at a concentration of 5 ppm. How many grams of chemical
B must be dispensed to maintain the treatment concentration?
6.0x60x5.0x0.0038 ^ „, r ■ • , t>
= 6.84 grams oi chemical B.
1.00 ^
Constant-Flow Delivery of Chemicals
Of the variety of constant-flow devices that have been adapted to
hatchery use, commercial chicken waterers are the most reliable (Figure
G-1).
All such devices deliver only liquids. Dry chemicals first must be put
into solution before they can be dispensed. If the amount of dry chemi-
cal needed already has been computed by the formula given in the previ-
ous section, it only is necessary to determine the amount of liquid that
will be dispensed from the chicken waterer over the period of treatment.
This is done by simple proportion. For example, if the constant-flow de-
vice delivers 20 milliliters per minute and the treatment is to be 60
minutes long, 1,200 milliliters will be delivered in all. This is the water
404 FISH HATCHERY MANAGEMENT
ISr^^^iiir?'
Figure G-1. A constant- flow device for dispensing liquid chemicals, (l) The de-
vice must be positioned over the water inflow to the fish-rearing unit, to insure
uniform mixing of the chemicals in the water. (2) The device can be made from
a conventional chicken waterer. Note siphon in place (arrow).
volume into which the predetermined weight of chemical should be dis-
solved before treatment begins.
If a 300-gallon tank were receiving a 10-gallon-per-minute water flow,
it would take at least 30 minutes (300 ^ 10) for water in the tank to be
replaced. It would take this long for any chemical to reach a desired
concentration in the tank. Thus, much of the treatment would be wast-
ed. To avoid such waste, it is best to pretreat the tank. The water flow
is shut off briefly, and chemical is quickly added to establish the final
concentration required (according to the formula for static treatment
above). Then the water flow is resumed and chemical metering is begun
with the constant-flow device.
After all the chemical has been dispensed, some time will be required
for the last of it to be flushed from the treated tank. Partial draining of
the tank will flush much of the chemical from the unit. Fish should be
watched for signs of stress after, as well as during, the treatment period.
If effluent from the tank has to be treated for public- health reasons, such
treatment should be continued until all the chemical has disappeared
from the system.
H
Appendix
Drug Coatings for
Feed Pellets
Either gelatin or soy oil may be used as drug carriers for coating feed pel-
lets. A representative sample of pellets should be checked for adequate
coatings before the operation is terminated.
Gelatin: 125 grams gelatin in 3.0 quarts water per 100 pounds of pellets.
(1) Slowly dissolve the gelatin into hot tap water.
(2) Stir the drug into the gelatin solution until all lumps are gone.
(3) Slowly add the drug-gelatin mixture to pellets as they are stirred by
hand or in a small cement mixer. To avoid pellet breakage, stir gently and
only long enough to assure an even drug coating.
Soy oil: 2-3 pounds per 100 pounds of pellets.
(1) Mix drug evenly in warm (100-120° F) oil.
(2) Pour or spray mixture over pellets.
405
I
Appendix
Length- Weight Tables
Guide to Selecting a Condition Factor (C) Table to
Match a Species of Fish
Species
Muskellunge (l,600), tiger muskellunge (l,600)
Northern pike (l,81l)
Lake trout (2,723)
Chinook salmon (2,959), walleye (3,000), chan-
nel catfish (2,877)
Westslope cutthroat trout (3,559), coho salmon
(3,737), steelhead (3,405)
Rainbow, brook, and brown trout (4,055 ac-
cepted rainbow trout C factor)
Largemouth bass (4,606)
The body form of some fishes remains nearly constant until the fish be-
come sexually mature. Therefore, the table can be used for fish longer
than 10 inches, or shorter than 1 inch, if the decimal point is moved as fol-
lows in the tables:
Columns Fish shorter than 7 inch Fish longer than 10 inches
1 and 4 Move three spaces to left Move three spaces to right
2 and 5 Move one space to left Move one space to right
3 and 6 Move three spaces to right Move three spaces to left
406
Condition
factor
(Cx 10^^'
Table
1,500
I-l
2,000
1-2
2,500
1-3
3,000
1-4
3,500
1-5
4,000
1-6
4,500
1-7
5,000
1-8
LENG TH-WKIGH I lABLES 407
Table I-l.
LENGTH-WEIGHT
RELATIONSHIPS FOR FISH WITH C = I,.')00x lo '
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.150
1.0000
6666.664
0.0680
2.540
14697.465
0.154
1.0088
6493.508
0.0699
2.562
14315.719
0.158
1.0175
6329.117
0.0717
2.584
13953.301
0.162
1.0260
6172.844
0.0735
2.606
13608.777
0.1 fi6
1.0344
6024.102
0.0753
2.627
13280.859
0.170
1.0426
5882.359
0.0771
2.648
12968.371
0.174
1.0507
5747.137
0.0789
2.669
12670.250
0.178
1.0587
5617.988
0.0807
2.689
12385.531
0.182
1.0666
5494.516
0.0826
2.709
12113.324
0.186
1.0743
5376.355
0.0844
2.729
11852.824
0.190
1.0820
5263.172
0.0862
2.748
11603.293
0.194
1.0895
5154.652
0.0880
2.767
11364.051
0.198
1.0970
5050.520
0.0898
2.786
11134.477
0.202
1.1043
4950.512
0.0916
2.805
10913.996
0.206
1.1115
4854.383
0.0934
2.823
10702.074
0.210
1.1187
4761.922
0.0953
2.841
10498.227
0.214
1.1257
4672.914
0.0971
2.859
10302.000
0.218
1.1327
4587.172
0.0989
2.877
10112.977
0.222
1.1396
4504.523
0.1007
2.895
9930.762
0.226
1.1464
4424.797
0.1025
2.912
9754.996
0.230
1.1531
4347.844
0.1043
2.929
9585.348
0.234
1.1598
4273.523
0.1061
2.946
9421.496
0.238
1.1663
4201.699
0.1080
2.963
9263.1.52
0.242
1.1728
4132.250
0.1098
2.979
9110.043
0.246
1.1793
4065.061
0.1116
2.995
8961.914
0.250
1.1856
4000.021
0.1134
3.011
8818.523
0.254
1.1919
3937.029
0. 1 1 52
3.027
8679.652
0.258
1.1981
3875.990
0.1170
3.043
8545.082
0.262
1.2043
3816.815
0.1188
3.059
8414.625
0.266
1.2104
3759.420
0.1207
3.074
8288.090
0.270
1.2164
3703.725
0.1225
3.090
8165.305
0.274
1.2224
' 3649.656
0.1243
3.105
8046.105
0.278
1.2283
3597.144
0.1261
3.120
7930.332
0.282
1.2342
3546.121
0.1279
3.135
7817.848
0.286
1.2400
3496.525
0.1297
3.1.50
7708. ,508
0.290
1.2458
3448.297
0.1315
3.164
7602.184
0.294
1.2515
3401.382
0.1334
3.179
7498.754
0.298
1.2571
3355.726
0.1352
3.193
7398.098
0.302
1.2627
3311.280
0.1370
3.207
7300.113
0.306
1.2683
3267.995
0.1388
3.221
7204.688
0.310
1.2738
3225.828
0.1406
3.235
7111.723
0.314
1.2792
3184.735
0.1424
3.249
7021.129
0.318
1.2846
3144.676
0.1442
3.263
6932.813
0.322
1.2900
3105.612
0.1461
3.277
6846.691
0.326
1.2953
3067.506
0.1479
3.290
6762.684
0.330
1.3006
3030.324
0.1497
3.303
6680.711
408
FISH HA rCHEKY MANAGEMENT
Tabu: I-l.
C = l.-WOx 10" ■
', CONIINIJEI)
Wl K.ll 1
l,()(H)
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.334
1.3058
2994.033
0.1515
3.317
6600.703
0.338
1.3110
2958.601
0.1,533
3.330
6522.590
0.342
1.3162
2i)23.9i)8
0.1551
3.343
6446.301
0.34fi
1.3213
2890. li)5
0. 1 5(i9
3.35fi
6371.777
0.350
1.3263
2857. 1()4
0.1588
3.369
<>298.957
0.354
1.3344
2824.880
0.1606
3.382
6227.785
0.358
1.3364
2793.317
0.1624
3.394
6158.199
0.3(i2
1.3413
2762.452
0.1642
3.407
60!)().15()
0.3(i(i
1.3463
2732.261
0.1660
3.419
(i023.598
0.370
1.3511
2702.723
0.1678
3.432
.5958.477
0.374
1 .35()0
2673.817
0.1696
3.444
5894.7,50
0.378
1.3608
2645.523
0.1715
3.456
5832.371
0.382
1.36,56
2617.822
0.1733
3.469
5771.301
0.386
1.3703
2590.694
0.1751
3.481
57 1 1 .492
0.390
1.3751
2,564.123
0.1769
3.493
5652.914
0.394
1.3797
2,538.091
0.1787
3.505
5595.523
0.398
1.3844
2512.583
0.1805
3.516
5539.289
0.402
1.3890
2487.582
0.1823
3.528
5484.172
0.406
1.3936
2463.074
0.1842
3.540
5430.141
0.410
1.3982
2439.044
0.1860
3.551
5377.164
0.414
1.4027
2415.479
0.1878
3.563
5325.211
0.418
1.4072
2392.364
0.1896
3.574
5274.254
0.422
1.4117
236!).<)88
0.1914
3.586
5224.258
0.426
1.4161
2347.438
0.1932
3.597
5175.207
0.430
1.4206
2325.601
0.1950
3.608
5127.063
0.434
1.4249
2304.167
0.19()9
3.619
5079.809
0.438
1.4293
2283.124
0.1987
3.630
,5033.418
0.442
1.4336
2262.463
0.2005
3.641
4987.867
0.446
1.4380
2242.172
0.2023
3.652
4943.133
0.450
1.4422
2222.241
0.2041
3.663
4899.195
0.454
1.4465
2202.662
0.2059
3.674
4856.031
0.458
1.4507
2183.425
0.2077
3.685
4813.621
0.462
1 .45.50
2164.521
0.2096
3.696
4771.945
0.466
1.4591
2145.941
0.2114
3.706
4730.984
0.470
1.4633
2127.678
0.2132
3.717
4690.719
0.474
1.4674
2109.723
0.2150
3.727
4651.137
0.478
1.4716
2092.069
0.2168
3.738
4612.215
0.482
1.4757
2074.707
0.2186
3.748
4573.938
0.486
1.4797
2057.631
0.2204
3.758
4536.293
0.490
1.4838
2040.834
0.2223
3.769
4499.262
0.494
1.4878
2024.310
0.2241
3.779
4462.832
0.498
1.4918
2008.()5()
0.2259
3.789
4426.984
0.504
1.4978
1984.127
0.2286
3.804
4374.246
0.512
1.5057
1953.125
0.2322
3.824
4305. 8i)8
0.520
1.5135
1923.078
0.2359
3.844
4239. (i52
0.528
1.5212
1893.941
0.2395
3.864
4175.418
LENG IH-WEIGHI TABLES
409
Table I-l.
C = l,.')()Ox 10
, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0..')36
1.5288
1865.673
0.2431
3.883
4113.098
0.544
1.5364
1838.237
0.2468
3.902
40.52.614
0.552
1.5439
1811.596
0.2.504
3.921
3993.881
0.560
1.5513
1785.717
0.2540
3.940
3936.826
0.568
1.5587
1760.566
0.2576
3.959
3881.379
0.576
1.5659
1736.114
0.2613
3.978
3827.471
0.584
1.5732
1712.332
0.2649
3.996
3775.041
0.592
1.5803
1689.192
0.2685
4.014
3724.027
0.600
1.5874
1666.670
0.2722
4.032
3674.374
0.608
1.5944
1644.740
0.2758
4.0,50
3626.028
0.616
1.6014
1623.380
0.2794
4.068
3578.937
0.624
1.6083
1602.568
0.2830
4.085
3533.053
0.632
l.(il51
1582.283
0.2867
4.102
3488.332
0.640
1.6219
1562.504
0.2903
4.120
3444.728
0.648
1.6286
1543.214
0.2939
4.137
3402.201
0.656
1.6353
1524.395
0.2976
4.154
3360.711
0.664
1.6419
1,106.029
0.3012
4.171
3320.221
0.672
1.6485
1488.100
0.3048
4.187
3280.695
0.680
1 .65.50
1470.593
0.3084
4.204
3242.099
0.688
1.6615
1453.493
0.3121
4.220
3204.400
0.696
1.6679
1436.787
0.3157
4.236
3167.569
0.704
1.6743
1420.460
0.3193
4.253
3131.574
0.712
1.6806
1404.,")00
0.3230
4.269
3096.388
0.720
1.6869
1388.894
0.3266
4.285
3061.984
0.728
1.6931
1373.632
0.3302
4.300
3028.336
0.736
1.6993
1358.701
0.3338
4.316
2995.420
0.744
1.7054
1344.092
0.3375
4.332
2963.211
0.752
1.7115
1329.793
0.3411
4.347
2931.688
0.760
1.7175
1315.795
0.3447
4.363
2900.828
0.768
1.7235
1302.08!)
0.3484
4.378
2870.612
0.776
1.7295
1288.666
0.3520
4.393
2841.018
0.784
1.7354
1275.516
0.3556
4.408
2812.028
0.792
1.7413
1262.632
0.3592
4.423
2783.624
0.800
1.7472
1250.006
0.3629
4.438
2755.788
0.808
1.7530
1237.630
0.3(i(i5
4.4,53
2728.503
0.816
1.7587
1225.496
0.3701
4.467
2701.753
0.824
1.7(i45
1213.598
0.3738
4.482
2675.523
0.832
1.7701
1201.929
0.3774
4.496
2649.797
0.840
1.7758
1190.482
0.3810
4.511
2624..561
0.848
1.7814
1179.251
0.3846
4.525
2599.801
0.856
1.7870
1168.230
0.3883
4.539
2.575.504
0.864
1.7926
1157.414
0.3919
4.5,53
2551.657
0.872
1.7981
1146.795
0.3955
4..567
2528.248
0.880
1.8036
1136.370
0.3992
4.581
2.505.264
0.888
1 .8090
1126.132
0.4028
4.-595
2482.694
0.896
1.8144
1116.078
0.4064
4.609
2460.527
410
FISH HATCHERY MANAGEMENT
Table I-l.
C = \,5()0x 10 ■
', CONTINUED
WEIGHT/
1,000
LENGIH
FISH/
Wl-.IGHr
I.KNGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.904
1.8198
110(i.201
0.4100
4.622
2438.753
0.912
1.8252
1096.498
0.4137
4.636
2417.360
0.920
1.8305
1086.963
0.4173
4.649
2396.340
0.928
1.83,58
1077.593
0.4209
4.663
2375.682
0.936
1.8410
1068.382
0.4246
4.676
2355.377
0.944
1.8463
1059.328
0.4282
4.689
2335.417
0.952
1.8515
1050.427
0.4318
4.703
2315.791
0.960
1 .8566
1041.673
0.43.54
4.716
2296.493
0.968
1.8618
1033.064
0.4391
4.729
2277.514
0.976
1.8669
1024.596
0.4427
4.742
2258.846
0.984
1.8720
1016.266
0.4463
4.7,55
2240.481
0.992
1.8770
1008.071
0.4500
4.768
2222.413
1 .000
1.8821
1000.000
0.4536
4.780
2204.620
1.080
1.9310
925.927
0.4899
4.905
2041.318
1.160
1.9775
862.072
0.5262
5.023
1900.541
1.240
2.0220
806.455
0.5625
5.136
1777.928
1.320
2.0646
757.580
0.5987
5.244
1670.177
1.400
2.1054
714.291
0.6350
5.348
1574.740
1,480
2.1448
675.681
0.6713
5.448
1489.620
1 .560
2.1828
641.031
0.7076
5.544
1413.230
1.640
2.2195
609.762
0.7439
5.637
1344.293
1.720
2.25.50
581.401
0.7802
5.728
1281.769
1.800
2.2894
555. ,562
0.8165
5.815
1224.802
1.880
2.3228
531.921
0.8527
5.900
1172.684
1.960
2.3553
510.210
0.8890
5.983
1124.820
2.040
2.3870
490.202
0.9253
6.063
1080.709
2.120
2.4178
471.704
0.9616
6.141
1039.928
2.200
2.4478
454.552
0.9!)7!)
6.217
1002,113
2.280
2.4771
438.603
1.0342
6.292
966.952
2.360
2.5058
423.735
1 .0705
6.365
934.174
2.440
2.5338
409.842
1.1067
6.436
903,546
2.520
2.,5611
396.831
1.1430
6.505
874.862
2.600
2.5880
384.621
1.1793
6.573
847.944
2.680
2.6142
373.140
1.2156
6.640
822.632
2.760
2.6400
362.324
1.2519
6.706
798.788
2.840
2.6653
352.118
1.2882
6.770
776.287
2.920
2.6901
342.471
1.3245
6.833
755.019
3.000
2.7144
333.339
1.3608
6.895
734.885
3.080
2.7383
324.681
1,3970
6.955
715.798
3.160
2.7618
316.461
1.4333
7.015
697, ()76
3.240
2.7849
308.647
1.4696
7.074
680,450
3.320
2.8077
301.210
1..5059
7.131
664.053
3.400
2.8300
294.123
1.5422
7,188
648.429
3.480
2.8521
287.361
1.5785
7.244
633.522
3.560
2.8738
280.904
1.6148
7.299
619.286
3.640
2.8951
274.730
1.6510
7.354
605.676
LENGlH-VVtlGHT TABLF.S
411
T.\BLE I-l.
C= l,.TOOx 10 '
', CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GR.AMSJ
iCM)
KH.OGR.AM
3.720
2.9162
268.822
1.6873
7.407
592.6,50
3.800
2.9369
263.163
1.7236
7.460
580.174
3.880
2.9574
257.374
1.7599
7.512
,568.211
3.960
2.9776
252.530
1.7962
7.563
5.56.732
4.040
2.9975
247.529
1.8325
7.614
545.708
4.120
3.0172
242.723
1.8688
7.664
,535.112
4.200
3.0366
238.100
1.9050
7.713
524.919
4.280
3.0557
233.649
1.9413
7.762
515.108
4.360
3.0746
229.362
1.9776
7.810
505.656
4.440
3.0933
225.230
2.0139
7.857
496.545
4.520
3.1118
221.243
2.0,502
7.904
487.757
4.600
3.1301
217.396
2.0865
7.9,50
479.274
4.680
3.1481
213.679
2.1228
7.99(i
471.082
4.760
3.1659
210.088
2.1,591
8.041
463.164
4.840
3.1836
2()6.fil6
2.1953
8.()8f)
455.509
4.920
3.2010
203.256
2.2316
8.131
448.102
5.000
3.2183
200.000
2.2680
8.174
440.924
5.400
3.3019
185.185
2.4494
8.387
4()8.263
5.800
3.3815
172.414
2.6308
8.589
380.107
6.200
3.4575
161.2!)()
2.8123
8.782
355.584
6.600
3.5303
151.515
2.9937
8.967
334.034
7.000
3.6003
142.857
3.1751
9.145
314.946
7.400
3.6676
135.135
3.3,566
9.316
297.922
7.800
3.7325
128.205
3.5380
9.481
282.644
8.200
3.7952
121.951
3.7194
9.640
268.856
8.600
3.8560
116.279
3.9009
9.794
256.352
9.000
3.9149
111.111
4.0823
9.944
244.958
9.400
3.9720
106.383
4.2638
10.089
234.535
9.800
4.0276
102.041
4.4452
10.230
224.962
10.200
4.0816
98.039
4.626()
10.367
2Ui.l40
10.600
4.1343
94.340
4.8081
10.. 501
207.984
11.000
4.1857
90.909
4.9895
10.632
200.421
11.400
4.2358
87.720
5.1709
10.759
193.388
11.800
4.2848
84.746
5.3524
10.883
186.833
12.200
4.3327
81.967
5.5338
1 1 .005
180.707
12.600
4.3795
79.365
5.71.52
11.124
174.;)70
13.000
4.4254
76.923
5.8967
11.240
169.587
13.400
4.4703
74.627
6.0781
1 1 .355
164.524
13.800
4.5143
72.464
6.2595
1 1 .466
159.756
14.200
4.5576
70.423
6.4410
11.576
155.255
14.600
4.5999
68.493
6.6224
11.684
151.002
15.000
4.6416
66.667
6.8039
11.790
146.975
15.400
4.6825
64.935
6.9853
1 1 .893
143.1,58
15.800
4.7227
63.291
7.1667
11.996
139.533
16.200
4.7622
61.728
7.3482
12.096
136.088
1().600
4.8011
60.241
7.5296
12.195
132.808
412
KLSH HATCHERY MANAGEMENT
-7
Table 1-1. c= i.^oox lo , continued
WEIGHT/
1, ()()()
l.KNCriH
FISH/
WKIGH'I
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
17.{)()()
4.8393
58,824
7.7111
12.292
1 29.684
17.400
4.8770
57.471
7.8925
12.388
12(i.7()2
17.800
4.9141
.56.180
8.0739
12.482
123.855
18.200
4.9506
54,945
8.2554
12.575
121.133
18. ()()()
4.9866
53,764
8.4368
12.666
118.528
19.()()()
5.0221
52,632
8.(il82
12.756
116.033
19.400
5.057 1
51.546
8.7997
12.845
113.640
19.800
5.0916
50,505
8.9811
1 2.933
111.344
20.200
5.1257
49,505
9.1625
13.019
109.140
20.600
5.1593
48,544
9.3440
13.105
107.021
21.000
5.1925
47,619
i).5254
13.189
104.982
21.400
5.2252
46,729
9.7069
13.272
103.020
21.800
5.2576
45,872
9.8883
13.354
101.129
22.200
5.2896
45.045
10.0697
13.436
99.307
22.600
5.3211
44.248
10.2512
13.516
97.550
23.000
5.3524
43.478
1().432()
13.595
95.853
23.400
5.3832
42.735
10.6140
13.673
94.215
23.800
5.4137
42,017
10.7955
13.751
92.631
24.200
5.4439
41,322
10.9769
13.827
91.100
24.(i00
5.4737
40,650
11.1 583
13.903
89.619
25.000
5. ,5032
40,000
11.3398
13.978
88.185
25.800
5.5613
38,760
11.7027
14.126
85.4,50
26.600
5.6182
37,594
12.0650
14.270
82.880
27.400
5.6740
36,496
12.4285
14.412
80.460
28.200
5.7287
35.461
12.7913
14.551
78.178
29.000
5.7823
34.483
13.1542
14.687
76,021
29.800
5.8350
33.557
13.5171
14.821
73,980
30.600
5.8868
32.680
13.8800
14.9,52
72,046
31.400
5.9376
31,847
14.2428
15.082
70,211
32.200
5.5)876
3 1 ,056
14.6057
15.209
68,466
33.000
6.0368
30.303
14.9686
15.333
66,807
33.800
6.0852
29.586
15.3314
15.4.56
65,225
34.600
6.1328
28.902
15.6943
15.577
63,717
35.400
6.1797
28.249
16.0572
15.697
62.277
36.200
6.2259
27.624
16.4201
15.814
60.901
37.000
6.2715
27.027
16.782!)
15.930
59,584
37.800
6.3164
26.455
17.1458
16.044
58,323
38.(i00
6.3606
25.907
17.5087
16.156
57,114
39.400
6.4042
25.381
17.8716
16.267
55.955
40.200
(i.4473
24.876
18.2344
16.376
54.841
4 1 .()t)0
6.4898
24.390
18.5973
16.484
53.771
41.800
6.5317
23.923
18.9602
16.591
52.742
42.600
6.5731
23.474
19.3230
16.696
51.752
43.400
6.6140
23.041
19.6859
16.800
.50.798
44.200
6.6544
22.624
20.0488
16.902
49.878
45.000
6.()943
22.222
20.4117
17.004
48.991
LENGTH-WEIGHT TABLES
413
Table I-l.
C = 1,500 X 10
, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
45.800
6.7338
21.834
20.7745
17.104
48.136
46.600
6.7727
21.459
21.1374
17.203
47.309
47.400
6.8113
21.097
2 1 .5003
17.301
46.511
48.200
6.8494
20.747
21.8632
17.397
45.739
49.000
6.8871
20.408
22.2260
17.4!)3
44.992
49.800
6.9244
20.080
22.5889
17.588
44.269
50.600
6.9612
19.763
22.9518
17.682
43.570
51.400
6.9977
19.455
23.3147
17.774
42.891
52.200
7.0338
19.157
23.6775
17.866
42.234
53.000
7.0696
18.868
24.0404
17.957
41.597
53.800
7.10,50
18.587
24.4033
18.047
40.978
54.600
7.1400
18.315
24.7661
18.136
40.378
55.400
7.1747
18.051
25.1290
18.224
39.795
56.200
7.2091
17.794
25.4919
18.311
39.228
57.000
7.2432
17.544
25.8548
18.398
38.677
57.800
7.2769
17.301
26.2176
18.483
38.142
58.600
7.3103
17.065
26..5805
18.568
37.621
59.400
7.3434
16.835
26.9434
18.652
37.115
60.200
7.3762
16.611
27.3063
18.736
36.622
61.000
7.4088
16.393
27.6691
18.818
36.141
61.800
7.4410
16.181
28.0320
18.900
35.673
62.600
7.4730
15.974
28.3949
18.981
35.218
63.400
7.5047
15.773
28.7578
19.062
34.773
64.200
7.5361
15.576
2i).120fi
19.142
34.340
65.000
7..5673
15.385
29.4835
19.221
33.917
65.800
7.5982
15.198
29.8464
19.299
33..505
66.600
7.6289
15.015
30.2092
19.377
33.102
67.400
7.6,593
14.837
30.5721
19.455
32.709
68.200
7.6895
14.663
30.9350
19.,531
32.326
69.000
7.7194
14.493
31.2979
19.607
31.951
69.800
7.7492
14.327
31.6607
19.683
31. .585
70.600
7.7787
14.164
32.0236
19.758
31.227
71.400
7.8079
14.006
32.3865
19.832
30.877
72.200
7.8370
13.8,50
32.7494
19.906
30.535
73.000
7.8658
13.699
33.1122
19.979
30.200
73.800
7.8944
13.5,50
33.4751
20.052
29.873
74.600
7.9229
13.405
33.8380
20. 1 24
29.553
75.400
7.9511
13.263
34.2009
20.196
29.239
76.200
7.9791
13.123
34.,5637
20.267
28.932
77.000
8.0069
12.i)87
34.9266
20.338
28.631
77.800
8.0346
12.853
35.2895
20.408
28.337
78.600
8.0620
12.723
35.6523
20.478
28.049
79.400
8.0893
12.594
36.0152
20.547
27.766
80.200
8.1164
12.469
36.3781
20.616
27.489
81.000
8.1432
12.346
36.7410
20.684
27.217
81.800
8.1700
12.225
37.1038
20.752
26.951
414
FISH HAICHKRY MANAGF.MKNT
TABI. 1,1-1. C=l/)OOxlO SCONTINUED
WEIGHT/
1,(100
LENGTH
KISH/
WEIGH!'
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
82.fi()0
8.19()5
12.107
37.4667
20,819
26.690
83.400
8.2229
1 1 .9i)0
37.829()
2().88()
26.434
84.200
8.2491
11.876
38.1925
20,953
26.183
85.000
8.2751
11.765
38.5553
21,019
25.937
85.800
8.3010
ll.(i55
38.!I182
21.085
25.695
8(i.(i00
8.32(i7
11.547
3<».2K1 1
21,150
25.457
87.400
8.3523
11.442
39.6440
21,215
25.224
88.200
8.3777
11.338
40.0068
21,279
24,996
89.000
8.4030
11.236
40.3697
21,344
24,771
8!). 800
8.4281
11.13(i
40.7326
21,407
24.550
!)().()()()
8.4530
11.038
4 1 .0955
21,471
24.334
91. 400
8.4778
10.941
41.4583
21,534
24.121
92.200
8.5025
10.846
41.8212
21,. 596
23.!) 11
93.000
8.5270
10.753
42.1841
2 1 ,(i59
23.706
93.800
8.5514
10.6(.l
42.5470
21,721
2 3., 503
i»4.(iO()
8.5756
10.571
42,9098
21,782
23.305
95.400
8.5997
10.482
43.2727
21,843
23.109
9().2()()
8.6237
10.395
43.6356
21,904
22.917
97.000
8.6476
10.309
43.!)984
21,965
22.728
97.800
8.6713
10.225
44.3613
22,025
22.542
i)8.fi00
8.6948
10.142
44.7242
22,085
22.359
99.400
8.7183
10.060
45.0871
22,144
22.179
102.000
8.7936
9.804
46.2664
22,336
21.614
110.000
9.0178
9.091
49.8951
22.905
20.042
118.000
9.2313
8.475
53.5238
23.447
18.683
12(i.()0()
!).4354
7.937
57.1526
23.f»66
17.497
134.()()0
!).6310
7.463
60.7813
24.4(i3
16.452
142.000
!).8190
7.042
64.4100
24.940
15.525
150.000
10.0000
6.667
68.0388
25.400
14.697
LENGTH-WEIGHT TABLES 415
Table 1-2.
LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C= 2,000 x
10-7
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS'
(CM)
KILOGRAM
0.200
1 .0000
5000.000
0.0907
2.540
11023.102
0.204
1 .0066
4901.961
0.0925
2.,5.57
10806.965
0.208
1.0132
4807. ()9.5
0.0943
2.573
10599.141
0.212
1.0196
4716.984
0.0962
2..590
10399.160
0.216
1.0260
4629.633
0.0980
2.606
10206..586
0.220
1.0323
4.545.461
0.0998
2.622
10021.012
0.224
1.038,5
4464.293
0.1016
2.638
9842.066
0.228
1.0446
4385.973
0.1034
2.653
9669.402
0.232
1.0.507
4310.3.52
0.1052
2.669
9.502.691
0.236
1.0567
4237.297
0.1070
2.684
9341.629
0.240
1.0627
416().676
0.1089
2.699
9185.938
0.244
1.0685
4098.371
0.1107
2.714
903.5.348
0.248
1.0743
4032.269
0.1125
2.729
8889.617
0.2.'i2
1.0801
3968.266
0.1143
2.743
8748.516
0.2,56
1.0858
3906.262
0.1161
2.758
8611.820
0.260
1.0914
3846.166
0.1179
2.772
8479.332
0.264
1.0970
3787.892
0.1197
2.786
83.50.8.59
0.268
1.1025
3731.356
0.1216
2.800
8226.219
0.272
1.1079
3676.484
0.1234
2.814
8105.246
0.276
1.1133
3623.202
0.1252
2.828
7987.781
0.280
1.1187
3571.442
0.1270
2.841
7873.672
0.284
1.1240
3.521.141
0.1288
2.855
7762.777
0.288
1.1292
3472.237
0.1306
2.868
7654.961
0.292
1.1344
3424.672
0.1324
2.881
75.50.098
0.296
1.1396
3378.393
0.1343
2.895
7448.070
0.300
1.1447
3333.348
0.1361
2.908
7348.766
0.304
1.1498
3289.48!)
0.1379
2.920
7252.070
0.308
1.1548
3246.769
0.1397
2.933
7157.891
0.312
1.1.598
3205.144
0.1415
2.946
7066.121
0.316
1.1647
3164.573
0.1433
2.958
6976.680
0.320
1.1696
3125.016
0.14.51
2.971
6889.469
0.324
1.1745
3086.436
0.1470
2.983
6804.414
0.328
1.1793
3048.796
0.1488
2.995
6721.434
0.332
1.1840
3012.064
0.1506
3.007
6640.453
0.336
1.1888
2976.207
0.1524
3.020
6.561.402
0.340
1.1935
2941.193
0.1542
3.031
6484.211
0.344
1.1981
2906.993
0. 1 560
3.043
6408.813
0.348
1.2028
2873.579
0.1578
3.055
6335.148
0.3.52
1.2074
2840.925
0.1,597
3.067
6263.160
0.35(i
1.2119
2809.005
0.1615
3.078
6192.785
0.360
1.2164
2777.794
0.1633
3.090
6123.977
0.364
1.2209
2747.269
0.1651
3.101
6056.684
0.3()8
1.2254
2717.408
0.1669
3.112
5990.848
0.372
1.2298
2688.188
0.1687
3.124
5926.434
0.376
1.2342
2659.591
0.1705
3.13.5
5863.387
0.380
1.2386
2631. .59.5
0.1724
3.146
5801.664
416
FISH HATCHERY MANAGEMENT
Table 1-2. c= 2,000x10 ', continued
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.384
1.2429
2604.183
0.1742
3.157
5741.230
0.388
1.2472
2577.336
0.1760
3. 1 68
5682.043
0.392
1.2515
2551.037
0.1778
3.179
5624.066
0.396
1.2557
2525.26!)
0.1796
3.189
5567.258
0.400
1.2599
2500.0 Hi
0.1814
3.200
5511.586
0.404
1.2641
2475.264
0.1832
3.211
5457.016
0.408
1.2683
2450.997
0.1851
3.221
5403.516
0.412
1.2724
2427.201
0.1869
3.232
5351.055
0.416
1.2765
2403.863
0.1887
3.242
5299.602
0.420
1.2806
2380.969
0.1905
3.253
5249.129
0.424
1.2846
2358.507
().1!)23
3.263
5199.609
0.428
1.2887
2336.465
0.1941
3.273
5151,016
0.432
1.2927
2314.831
0.1960
3.283
5103.320
0.436
1.2966
2293.594
0.1978
3.293
5056,500
0.440
1.3006
2272.743
0.1996
3.303
5010.535
0.444
1.3045
2252.268
0.2014
3.313
4965.395
0.448
1.3084
2232.159
0.2032
3.323
4921.059
0.452
1.3123
2212.406
0.2050
3.333
4877.512
0.456
1.3162
2192.999
0.20(i8
3.343
4834.727
0.460
1.3200
2173.929
0.2087
3.353
4792.688
0.464
1.3238
2155.188
0.2105
3.362
4751.371
0.468
1.3276
2136.768
0.2123
3.372
4710.758
0.472
1.3314
2118.660
0.2141
3.382
4670.840
0.476
1.3351
2100.856
0.21.59
3.391
4631.586
0.480
1.3389
2083.349
0.2177
3.401
4592.992
0.484
1.3426
2066.132
0.2195
3.410
4555.031
0.488
1.3463
2049.196
0.2214
3.419
4517.695
0.492
1.3499
2032.536
0.2232
3.429
4480.969
0.496
1.3536
2016.145
0.2250
3.438
4444.832
0.500
1.3572
2000.000
0.2268
3.447
4409.238
0.508
1.3644
1968.504
0.2304
3.466
4339.801
0.516
1.3715
1937.985
0.2341
3.484
4272.520
0.524
1.3786
1908.398
0.2377
3.502
4207.289
0.532
1.3856
1879.701
0.2413
3.519
4144.023
0.540
1.3925
1851.854
0.2449
3.537
4082.633
0.548
1.3993
1824.819
0.2486
3.554
4023.033
0.556
1.4061
1798.563
0.2522
3.571
3965.149
0.564
1.4128
1773.052
0.2558
3.589
3908.906
0.572
1.4195
1748.254
0.2595
3.605
3854.237
0..580
1.4260
1724.141
0.2631
3.622
3801.075
0.588
1.4326
1700.683
0.2(i67
3.639
3749.361
0.596
1.4390
1677.856
0.2703
3.655
3699.034
0.604
1.4454
1655.633
0.2740
3.671
3650.041
0.612
1.4518
1633.991
0.2776
3.688
3602.328
0.620
1.4581
1612.907
0.2812
3.704
3555.847
0.628
1.4643
1592.361
0.2849
3.719
3510.550
LENGIH-WKIGHT TABLES
417
Table 1-2.
C = 2,0(){) X 10
\ CONTINUED
WEIGHT/
1. ()()()
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.(i3(i
1.4705
1572.331
0.2885
3.735
3466.393
0.644
1.4767
1552.799
0.2921
3.751
3423.333
0.652
1.4828
1.533.747
0.2!)57
3.766
3381.329
0.660
1.4888
1515.1.56
0.2994
3.782
3340.344
0.668
1.4948
1497.011
0.3030
3.797
3300.340
0.676
1 .5007
1479.295
0.3066
3.812
3261.283
0.684
1 .5066
1461.993
0.3103
3.827
3223.139
0.692
1.5125
1445.092
0.3139
3.842
3185.878
0.700
1.5183
1428.577
0.3175
3.856
3149.469
0.708
1.5241
1412.435
0.3211
3.871
3113.882
0.716
1..5298
1396.653
0.3248
3.886
3079.090
0.724
1 ..5354
1381.221
0.3284
3.900
3045.067
0.732
1.5411
1366.126
0.3320
3.914
3011.788
0.740
1.5467
1351.357
0.3357
3.929
2979.228
0.748
1.5522
1336.904
0.3393
3.943
2947.365
0.7.56
1.5577
1322.757
0.3429
3.957
2916.177
0.764
l.,5632
1308.906
0.3465
3.971
2885.641
0.772
1..5687
1295.343
0.3502
3.984
2855.738
0.780
1.5741
1282.057
0.3538
3.998
2826.449
0.788
1.5794
1269.042
0.3574
4.012
2797.7.54
0.796
1.5847
1256.287
0.3611
4.025
2769.636
0.804
1,5!)00
1243.787
0.3647
4.039
2742.078
0.812
1..5953
1231.533
0.3683
4.0.52
2715.063
0.820
1.6005
121!). 5 18
0.3719
4.065
2688.574
0.828
1.6057
1207.736
0.37.56
4.078
2662..598
0.836
1.6109
1196.178
0.3792
4.092
2637.119
0.844
1.6160
1184.840
0.3828
4.105
2612.123
0.852
1.6211
1173.715
0.3865
4.118
2587.596
0.860
1.6261
1162.797
0.3901
4.130
2563.525
0.868
1.6312
1152.080
0.3937
4.143
2539.898
0.876
1.6362
1141.559
0.3973
4.1.56
2516.703
0.884
1.6411
1131.228
0.4010
4.168
2493.928
0.892
1.6461
1121.083
0.4046
4.181
2471. .561
0.900
1.6510
1111.117
0.4082
4.193
2449.592
0.908
1.6558
1101.328
0.4119
4.206
2428.009
0.916
l.fi()()7
1091.709
0.4155
4.218
2406.804
0.924
1.6655
1082.257
0.4191
4.230
2385.966
0.932
1.6703
1072.968
0.4227
4.243
2365.486
0.940
1.6751
1063.836
0.4264
4.255
2345.354
0.948
1 .6798
1054.85S)
0.4300
4.267
2325.563
0.956
1 .6845
1046.031
0.4336
4.279
2306.102
0.964
1.6892
1037.351
0.4373
4.291
2286.964
0.972
1 .6939
1028.813
0.4409
4.302
2268.142
0.980
1.6985
1020.415
0.4445
4.314
2249.626
0.988
1.7031
1012.1.52
0.4481
4.326
2231.411
0.996
1.7077
1004.022
0.4518
4.338
2213.488
418
FISH HATCHERY MANAGEMENT
Table 1-2.
C= 2,000 X 10
\ CONTINUED
WEIGHT/
1,000
LKNGTH
KISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
1.040
1.7325
961.539
0.4717
4.400
2119.829
1.120
1.7758
892.859
0..5080
4.511
1968.416
1.200
1.8171
833.337
0.5443
4.615
1837.191
1.2H0
1 .85()6
781.254
0.5806
4.716
1722.368
1.360
1.8945
735.299
0.6169
4.812
1621.054
1.440
1.9310
694.449
0.6532
4.905
1530.998
1..520
1.9661
657.900
0.6895
4.994
14,50.420
1 .600
2.0000
625.006
0.7257
5.080
1377.900
l.(i80
2.0328
595.244
0.7620
5.163
1312.287
1.760
2.0646
568.188
0.7983
5.244
1252.638
1.840
2.0954
543.484
0.834()
5.322
1198.177
1.920
2.1253
520.839
0.870!)
5.398
1148.253
2.000
2.1544
500.006
0.9072
5.472
1102.323
2.080
2.1828
480.775
0.9435
5.544
10.59.927
2.160
2.2104
462.969
0.9797
5.614
1020.671
2.240
2.2374
446.435
1.0160
5.683
984.219
2.320
2.2637
431.041
1.0523
5.750
950.28 1
2.400
2.2894
416.673
1.0886
5.815
918.605
2.480
2.3146
403.232
1 . 1 249
5.879
888.973
2.,560
2.3392
390.631
1.1612
5.942
861.193
2.640
2.3633
378.794
1.1975
6.003
835.096
2.720
2.3870
367.653
1.2338
6.063
810.535
2.800
2.4101
357.148
1.2700
6.122
787.377
2.880
2.4329
347.228
1.3063
6.179
765.505
2.960
2.4552
337.843
1.3426
6.236
744.816
3.040
2.4771
328.953
1.3789
6.292
725.216
3.120
2.4986
320.518
1.4152
6.347
706.621
3.200
2.5198
312.505
1.4515
6.400
688.955
3.280
2.5407
304.883
1.4878
6.453
672.152
3.360
2.5611
297.624
1.5240
6.505
656.148
3.440
2..5813
290.703
1.5603
6.557
640.889
3.520
2.6012
284.096
1.5966
6.607
626.323
3.600
2.6207
277.783
1.6329
6.657
612.405
3.680
2.6400
271.744
1.6692
6.706
599.092
3.760
2.6590
265.962
1.7055
6.754
586.346
3.840
2.6777
260.421
1.7418
6.801
574.130
3.920
2.6962
255.107
1.7780
6.848
,562.413
4.000
2.7144
2,50.005
1.8143
6.895
551.165
4.080
2.7324
245.103
1 .8506
6.940
540.358
4.160
2.7,501
240.389
1.8869
6.985
529.967
4.240
2.7676
235.854
1.9232
7.030
519.967
4.320
2.7849
231.486
1 .9595
7.074
510.338
4.400
2.8020
227.277
1.9958
7.117
,501.060
4.480
2.8189
223.219
2.0321
7.160
492.112
4.560
2.8356
219.302
2.0683
7.202
483.479
4.640
2.8521
215.521
2.1046
7.244
475.143
LENGTH-WEIGHT TABLES
419
Table 1-2.
C = 2,000 X 10
, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
4.720
2.8684
211.869
2.1409
7.286
467.090
4.800
2.8845
208.337
2.1772
7.327
459.305
4.880
2.9004
204.922
2.2135
7.367
451.775
4.!)fi()
2.9162
201.617
2.2498
7.407
444.489
5.200
2.9625
192.308
2.3587
7..525
423.965
5.600
3.0366
178.572
2.5401
7.713
393.682
6.000
3.1072
166.667
2.7215
7.892
367.437
6.400
3.1748
156.250
2.9030
8.064
344.472
6.800
3.2396
147.0.59
3.0844
8.229
324.209
7.200
3.3019
138.889
3.26,59
8.387
306.198
7.600
3.3620
131.579
3.4473
8.,539
290.082
8.000
3.4199
125.000
3.6287
8.687
275.578
8.400
3.4760
119.048
3.8102
8.829
262.455
8.800
3.5303
113.637
3.9916
8.967
2,50.526
9.200
3.5830
108.696
4.1730
9.101
239.633
9.600
3.6342
104.167
4.3545
9.231
229.649
10.000
3.6840
100.000
4.5359
9.357
220.463
10.400
3.7325
96.154
4.7173
9.481
211.983
10.800
3.7798
92.593
4.8988
9.601
204.132
11.200
3.8259
89.286
5.0802
9.718
196.842
11.600
3.8709
86.207
5.2616
9.832
190.054
12.000
3.9149
83.334
5.4431
9.944
183.719
12.400
3.9579
80.645
5.6245
10.053
177.793
12.800
4.0000
78.125
5.8060
10.160
172.237
13.200
4.0412
75.758
5.1*874
10.265
167.017
13.600
4.0816
73.530
6.1688
10.367
162.105
14.000
4.1213
71.429
6.3.503
10.468
157.473
14.400
4.1602
69.445
6.5317
10.,567
153.099
14.800
4.1983
67.568
6.7131
10.664
148.961
15.200
4.2358
65.790
6.8946
10.7,59
145.041
15.600
4.2727
64.103
7.0760
10.853
141.322
16.000
4.3089
62.500
7.2574
10.945
137.789
16.400
4.3445
60.976
7.4389
11.035
134.428
16.800
4.3795
59.524
7.6203
11.124
131.227
17.200
4.4140
58.140
7.8018
11.212
128.176
17.600
4.4480
56.818
7.9832
11.298
125.263
18.000
4.4814
55.556
8.1646
11.383
122.479
18.400
4.5144
54.348
8.3461
11.466
119.816
18.800
4.5468
53.192
8.5275
1 1 .549
117.267
19.200
4.5789
52.083
8.7090
11,630
114.824
19.600
4.6104
51.020
8.8904
11.710
112.481
20.000
4.6416
50.000
9.0718
11.790
110.231
20.400
4.6723
49.020
9.2.533
11.868
108.070
20.800
4.7027
48.077
!).4347
1 1 .945
105.991
21.200
4.7326
47.170
!).6161
12.021
103.992
21.600
4.7622
46.296
9.7976
12.096
102.066
420 FISH HAICHKRY MANAGEMENT
Table 1-2. c = 2,000 x lo"'', continued
WEIGHT/
1 ,()()()
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
22.000
4.7914
4.5.455
9.i)7<)()
12.170
100.210
22.400
4.8203
44.(i43
10.1()()4
12.244
98.421
22.800
4.8488
43.860
10.3419
12.316
96.694
23.200
4.8770
43.103
10..5233
12.388
95.027
23.600
4.9049
42.373
10.7048
12.458
93.416
24.000
4.9324
4 1 .667
10.88fi2
12.528
91.859
24.400
4.9597
40.984
11.0()7()
12..598
90.353
24.800
4.9866
40.323
n.2491
12.666
88.896
2.5.400
5.0265
39.370
ll.,5213
12.767
86.796
26.200
5.0788
38.168
11.8841
12.900
84.146
27. ()()()
5.1299
37.037
12.2470
13.030
81.(i52
27.800
5.1801
35.971
12.6099
13.157
79.303
28.600
5.2293
34.965
12.9728
13.282
77.084
29.400
.5.2776
34.014
13.33.56
13.405
74.i)87
30.200
5.3251
33.112
13.6985
13.526
73.000
3L0()()
5.3717
32.258
14.0614
13.644
71.117
3L8()()
5.4175
31.446
14.4243
13.760
69.327
32.600
.5.4626
30.675
14.7871
13.875
67.626
33.400
5.5069
29.940
15.1.500
13.987
66.006
34.200
5.5.505
29.240
1.5.5129
14.098
64.462
35.000
5.5934
28.571
15.8758
14.207
62.989
35.800
5.6357
27.933
16.2386
14.315
61. .581
36.600
5.6774
27.322
16.6015
14.421
60.235
37.400
5.7185
26.738
16.9644
14.525
58.947
38.200
5.7590
26.178
17.3272
14.628
57.712
39.000
5.7989
25.64 1
17.6901
14.729
56.529
39.800
5.8383
25.126
18.0530
14.829
55.392
40.600
5.8771
24.630
18.41,59
14.928
.54.301
4L40()
5.9155
24.155
18.7787
15.025
53.252
42.200
5.9533
23.697
19.1416
15.121
52.242
43.000
.5.9907
23.256
19.5045
15.21()
51.270
43.800
6.0277
22.831
19.8674
15.310
50.334
44.()00
6.0641
22.421
20.2302
15.403
49.431
45.400
6.1002
22.026
20.5931
15.494
48.560
46.200
6.1358
21.645
20.9560
15.585
47.719
47.000
().171()
21.277
21.3188
15.674
46.907
47.800
(i.2()58
20.920
21.6817
15.763
46.122
48.600
6.2403
20.576
22.0446
15.8,50
45.362
49.400
6.2743
20.243
22.4075
15.937
44.628
50.200
6.3080
li).920
22.7703
16.022
43.917
,5L()00
6.3413
19.608
23.1332
16.107
43.228
5L8()()
6.3743
19.305
23.49()1
l(i.l91
42.5(i0
52.(.00
(i.407()
19.011
23.8590
16.274
41.913
,53.400
6.4393
18.727
24.2218
16.35()
41.285
54.200
6.4713
18.4.50
24.5847
16.437
40.676
5.5.000
6..5030
18.182
24.9476
16.517
40.084
LENGTH-WEIGHl TABLES
421
Table 1-2.
C = 2,000 X 10
, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CMJ
KILOGRAM
F,5.H0{)
6..5343
17.921
25.3105
16..597
39..509
,5fi.fiOO
6.,56.54
17.668
25.6733
16.676
38.951
,57.400
6.,5962
17.422
26.0362
16.754
38.408
,58.200
6.6267
17.182
26.3991
16.832
37.880
,')9.0()0
6.6.569
Ui.949
26.7619
16.909
37.366
,59.800
6.6869
16.722
27.1248
16.985
36.867
fiO.fiOO
6.7166
16.,502
27.4877
17.060
36.380
fi 1.400
6.7460
16.287
27.8506
17.135
35.906
()2.20()
6.77,52
1().()77
28.2134
17.209
35.444
fi3.000
6.8041
15.873
28.57()3
17.282
34.994
63.800
6.8328
15.674
28.9392
17.3.55
34.,5.55
64.600
6.8612
1.5.480
29.3021
17.427
34.127
6.5.400
6.8894
15.291
29.6649
17.499
33.710
66.200
6.9174
15.106
30.0278
17.570
33.302
67.000
6.9451
14.925
30.3907
17.641
32.905
67.800
6.9727
14.749
30.7536
17.711
32.516
68.600
7.0000
14.577
31.1164
17.780
32.137
69.400
7.0271
14.409
31.4793
17.84il
31.767
70.200
7.0540
14.245
31.8422
17.917
31.405
71.000
7.0807
14.084
32.20,50
17.98.5
31.051
71.800
7.1072
13.928
32.5679
18.0.52
30.705
72.fi0()
7.1335
13.774
32.9308
18.119
30.367
73.400
7.1.596
13.624
33.2937
18.18.5
30.036
74.200
7.18.55
13.477
33.6566
18.251
29.712
7.5. ()()()
7.2112
13.333
34.0194
18.317
29.395
7.5.800
7.2368
13.193
34.3823
18.381
29.085
76.600
7.2622
13.055
34.74.52
18.446
28.781
77.400
7.2874
12.920
3.5.1080
18.510
28.483
78.200
7.3124
12.788
35.4709
18.573
28.192
79.000
7.3372
12.658
35.8338
18.637
27.907
79.800
7.3619
12.531
36.1967
18.699
27.627
80.600
7.3864
12.407
36.5595
18.7(i2
27.353
81.400
7.4108
12.285
36.9224
18.823
27.084
82.200
7.43,50
12.165
37.2853
18.885
26.820
83.000
7.4590
12.048
37.6481
18.946
26..562
83.800
7.4829
11.933
38.0110
19.007
26.308
84.600
7.5067
11.820
38.3739
19.067
26.059
8.5.400
7..5302
11.710
38.73(i8
19.127
25.815
86.200
7..5,537
11.601
39.09!)7
19.186
25.576
87. ()()()
7.5770
11.494
39.4625
19.246
25.340
87.800
7.6001
1 1 .390
39.8254
19.304
25.110
88.600
7.6231
11.287
40.1883
1 9.363
24.883
89.400
7.6460
11.186
40.55 1 1
19.421
24.660
90.200
7.6688
11.086
40.9140
19.479
24.441
91.000
7.6914
10.989
41.27(i9
19.536
24.227
91.800
7.7138
10.893
41.()398
19..593
24.015
422 FISH HATCHERY MANAGEMENT
Table 1-2. c = 2,000 x lo"'', continued
WEIGHT/
1,000
LENGTH
FISH/
WEIGH!
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
92.600
7.7362
10.799
42.0026
19.(i5()
23.808
93.400
7.7584
10.707
42.3655
19.706
23.604
94.200
7.7805
10.(il6
42.7284
19.762
23.404
95.000
7.8025
10.52()
43.0912
19.818
23.206
95.800
7.8243
10.438
43.4541
19.874
23.013
96.600
7.8460
10.352
43.8170
19.929
22.822
97.400
7.8676
10.267
44.1799
19.984
22.635
98.200
7.8891
10.183
44.5427
20.038
22.4.50
99.000
7.9105
10.101
44.9056
20.093
22.269
99.800
7.9317
10.020
45.2685
20.147
22.090
106.000
8.0927
9.434
48.0807
20.555
20.798
114.000
8.2913
8.772
51.7095
21.060
19.339
122.000
8.4809
8.197
55.3382
21.542
18.071
130.000
8.6624
7.692
58.96(i9
22.002
16.959
138.000
8.8365
7.246
62.5957
22.445
15.976
1 46.000
9.0041
6.849
66.2244
22.870
15.100
154.000
9.1657
6,494
69.8531
23.281
14.316
162.000
9.3217
6.173
73.4819
23.677
13.609
170.000
9.4727
5.882
77.1106
24.061
12.968
178.000
9.6190
5.618
80.7394
24.432
12.386
186.000
9.7610
5.376
84.3681
24.793
11.853
194.000
9.8990
5.155
87.9968
25.143
11.364
LENGTH-WEIGHT TABLES 423
Table 1-3.
LENCrH-WF.IGH 1
RKI.AIIONSHIPS FOR FISH
WriH C = 2,.iO()x
10- '
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
fish;
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.250
1 .0000
4000.002
0.1134
2..540
8818.480
0.254
1.0053
3937.010
0.1152
2.553
8679.609
0.25S
1.0106
3875.972
0.1170
2.567
8545.043
0.2(i2
1.0157
3816.798
0.1188
2.580
8414.586
0.2()(i
1.0209
3759.403
0.1207
2.,593
8288.055
0.270
1.0260
3703.709
0.1225
2.606
8165.270
0.274
1.0310
3649.641
0.1243
2.619
8046.070
0.278
1.0360
3597.128
0.1261
2.631
7930.301
0.282
1.0410
3546.106
0.1279
2.644
7817.813
().28(;
1.04,59
3496.510
0.1297
2.656
7708.477
0.290
1.0.507
3448.283
0.1315
2.669
7602.1,52
0.294
1 .0555
3401.368
0.1334
2.681
7498.723
0.298
1.0603
3355.713
0.1352
2.693
7398.070
0.302
1 .0650
3311.267
0.1370
2.705
7300.082
0.306
1.0697
3267.983
0.1388
2.717
7204.6,56
0.310
1.0743
3225.816
0.1406
2.729
7111.695
0.314
1.0789
3184.723
0.1424
2.740
7021.102
0.318
1.0835
3144.664
0.1442
2.752
6932.785
0.322
1.0880
3105.600
0.1461
2.764
6846.664
0.32fi
1.0925
3067. 4!)5
0.1479
2.775
6762.660
0.330
1.0970
3030.313
0.1497
2.786
6680.688
0.334
1.1014
2994.023
0.1515
2.797
6600.680
0.338
1.10,58
2958.591
0.1533
2.809
6522.566
0.342
1.1101
2923.988
0.1551
2.820
6446.281
0.346
1.1144
2890.185
0.1569
2.831
6371.7,58
0.350
1.1187
2857.154
0.1588
2.841
6298.938
0.354
1.1229
2824.870
0.1606
2.852
6227.762
0.358
1.1271
2793.308
0.1624
2.863
6158.180
0.362
1.1313
2762.443
0.1642
2.874
6090.133
0.366
1.1355
2732.252
0.1660
2.884
6023.,574
0.370
1.1396
2702.715
0.1678
2.895
5958.457
0.374
1.1437
2673.809
0.1696
2.905
5894.730
0.378
1.1478
2645.515
0.1715
2.915
5832.3.52
0.382
1.1518
2617.813
0.1733
2.926
5771.281
0.386
1 . 1 558
2590. 68()
0.1751
2.936
5711.477
0.390
1.1598
2564.115
0. 1 769
2.946
5652.898
0.394
1.1637
2538.084
0.1787
2.956
5595.,508
0.398
1.1677
2512.575
0.1805
2.966
5,539.273
0.402
1.1716
2487.575
0.1823
2.976
5484.1.56
0.406
1.1754
2463.067
0.1842
2.986
,5430.125
0.410
1.1793
2439.037
0.1860
2.i)!)5
5377.148
0.414
1.1831
2415.472
0.1878
3.005
5325.195
0.418
1.1869
2392.357
0.1896
3.015
.5274.238
0.422
1 . 1 907
2369.681
0.1914
3.024
,5224.246
0.426
1.1944
2347.431
0.1932
3.034
5175.191
424
FISH HATCHERY MANAGEMENT
Table 1-3. c = 2,500 x lo '.continued
WEIGHT/
1 .()()()
LENGIH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.430
1.1981
2325.,594
0.1950
3.043
5127.051
0.434
1.2018
2304.161
0.1969
3.053
.5079.797
0.138
1.2055
2283.118
0.1987
3.062
5033.406
0.442
1.2092
2262.457
0.2005
3.071
4987.855
0.44()
1.2128
2242.166
0.2023
3.081
4943.121
0.450
1.2164
2222.235
0.2041
3.090
4899.184
0.454
1.2200
2202.656
0.2059
3.099
48.56.020
0.458
1.2236
2183.419
0.2077
3.108
4813.609
0.4f)2
1.2272
2164.515
0.2096
3.117
4771.934
0.4fi6
1.2307
2145.936
0.21 14
3.126
4730.973
0.470
1.2342
2127.673
0.2132
3.135
4690.707
0.474
1.2377
2109.718
0.21.50
3.144
4651.125
0.478
1.2412
2092.063
0.2168
3.153
4612.203
0.482
1.2446
2074.702
0.2186
3.161
4573.926
{).48fi
1.2480
2057.626
0.2204
3.170
4536.281
0.490
1.2515
2040.830
0.2223
3.179
4499.250
0.494
1.2549
2024.305
0.2241
3.187
4462.820
0.498
1.2582
2008.045
0.2259
3.196
4426.977
0..504
1.2633
1984.127
0.2286
3.209
4374.246
0.512
1.2699
19.53.125
0.2322
3.226
4305.898
0,520
1.2765
1923.078
0.2359
3.242
4239.652
0.528
1.2830
1893.941
0,2395
3.2,59
4175.418
0.53(i
1.2895
1865.673
0.2431
3.275
4113.098
0.544
1.2958
1838.237
0.24(i8
3.291
4052.614
0.552
1.3022
1811.596
0.2504
3.307
3993.881
0.560
1.3084
1785.717
0.2540
3.323
3936.826
0.568
1.3146
1760.566
0.2576
3.339
3881.379
0.576
1.3208
1736.114
0.2613
3.355
3827.471
0.584
1.3269
1712.332
0.2<)49
3.370
3775.041
0.592
1.3329
1689.192
0.2685
3.386
3724.027
0.600
1.3389
1666.670
0.2722
3.401
3674.374
0.608
1.3448
1644.740
0.2758
3.416
3626.028
0.(il6
1.3,507
1623.380
0.2794
3.431
3578.937
0.624
1.3,565
1602.568
0.2830
3.445
3533.053
0.632
1.3623
1582.283
0.2867
3.460
3488.332
0.640
1.3680
1.562., 504
0.2903
3.475
3444.728
0.648
1.3737
1543.214
0.2939
3.489
3402.201
0.656
1.3793
1524.395
().297<;
3. ,503
3360.711
0.664
1.3849
1506.029
0.3012
3.518
3320.221
0.672
1.3904
1488.100
0.3048
3.532
3280.695
0.680
1 .39.59
1470.593
0.3084
3.546
3242.099
0.(i88
1.4014
1453.493
0.3121
3.5.59
3204.400
0.fi!>6
1.4068
1436.787
0.3157
3.573
3167.569
0.704
1.4121
1420.460
0.3193
3.587
3131.574
0.712
1.4175
1404.500
0.3230
3.600
3096.388
0.720
1.4228
1388.894
0.3266
3.614
3061.984
LENGTH-WEIGHT TABLES
425
Table 1-3.
C = 2, .500 X 10
' , CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHI
LENGTH
FISH,
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.728
1.4280
1373.632
0.3302
3.627
3028.336
0.736
1.4332
1358.701
0.3338
3.640
2995.420
0.744
1.4384
1344.092
0.3375
3.6,54
2963.211
0.752
1.4435
1329.793
0.3411
3.667
2931.688
0.760
1.4486
1315.795
0.3447
3.680
2900.828
0.768
1.4537
1302.089
0.3484
3.692
2870.612
0.776
1.4587
1288.666
0.3520
3.705
2841.018
0.784
1.4637
1275.516
0.3556
3.718
2812.028
0.792
1.4687
1262.632
0.3592
3.730
2783.624
0.800
1.4736
1250.006
0.3629
3.743
2755.788
0.808
1.4785
1237.630
0.3665
3.755
2728.503
0.816
1.4834
1225.496
0.3701
3.768
2701.7,53
0.824
1.4882
1213.598
0.3738
3.780
2675.523
0.832
1.4930
1201.929
0.3774
3.792
2649.797
0.840
1.4978
1190.482
0.3810
3.804
2624.561
0.848
1.5025
1179.251
0.3846
3.816
2,599.801
0.856
l.,5072
1168.230
0.3883
3.828
2575..104
0.864
1.5119
1157.414
0.3919
3.840
2.551.657
0.872
1.5166
1146.795
0.3955
3.852
2528.248
0.880
1.5212
1136.370
0.3992
3.864
2,505.264
0.888
1.5258
1126.132
0.4028
3.875
2482.694
0.896
1.5303
1116.078
0.40f)4
3.887
2460.527
0.904
1.5349
1106.201
0.4100
3.899
2438.7,53
0.912
1.5394
1096.498
0.4137
3.910
2417.360
0.920
1.5439
1086.963
0.4173
3.921
2396.340
0.928
1.5483
1077.593
0.4209
3.933
2375.682
0.936
1.5528
1068.382
0.4246
3.944
23,55.377
0.944
1.5572
1059.328
0.4282
3.955
2335.417
0.952
1.5616
1050.427
0.4318
3.966
2315.791
0.960
1.5659
1041.673
0.4354
3.977
2296.493
0.968
1.5703
1033.064
0.4391
3.989
2277.514
0.976
1.5746
1024. .596
0.4427
3.999
2258.846
0.984
1.5789
1016.266
0.4463
4.010
2240.481
0.992
1.5832
1008.071
0.4,500
4.021
2222.413
1.000
1.5874
1000.000
0.4536
4.032
2204.620
1.080
1.6286
925.927
0.4899
4.137
2041.318
1.160
1.6679
862.072
0.5262
4.236
1900.,541
1.240
1.7054
806.455
0..5625
4.332
1777.928
1.320
1.7413
757.580
0.5987
4.423
1670.177
1.400
1.7758
714.291
0.6350
4.511
1574.740
1.480
1.8090
675.681
0.6713
4..595
1489.620
1.560
1.8410
641.031
0.7076
4.676
1413.230
1.640
1.8720
609.762
0.7439
4.755
1344.293
1.720
1.9019
581.401
0.7802
4.831
1281.769
1.800
1.9310
555.562
0.81()5
4.905
1224.802
1.880
1.9592
531.921
0.8527
4.976
1172.684
426
FISH HAICHKRY MANAGKMKN T
Table 1-3.
c; = 2,. '■)()() > 10 ■
', CONIINl LI)
WEIGHT/
1, ()()()
LKNGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
1 .960
1 .9866
510.210
0.8890
5.046
1 121.820
2.040
2.0132
490.202
0.9253
5.114
1080. 709
2.120
2.03!)2
471.704
0.9(il6
5.180
1039.928
2.200
2.0646
454.552
0.9979
5.244
1002.113
2.280
2.0893
438. (;03
1.0342
5.307
966.952
2.360
2.1134
423.735
1 .0705
5.368
934.174
2.440
2.1370
409.842
1.1067
5.428
!)03.546
2.520
2.1602
396.831
1.1430
5.487
874.862
2.600
2.1828
384.621
1 . 1 793
5.544
847.944
2.680
2.2049
373.140
1.2156
5.601
822.f)32
2.760
2.2267
362.324
1.2519
5.656
798.788
2.840
2.2480
352.118
1.2882
5.710
776.287
2.920
2.2689
342.471
1.3245
5.763
755.019
3.000
2.2894
333.339
1.3608
5.815
734.885
3.080
2.3096
324.681
1.3970
5.866
715.798
3.160
2.3294
316.461
1.4333
5.917
()!)7,676
3.240
2.3489
308.647
1.4(i9(i
5.966
680.450
3.320
2.3681
301.210
1.5059
6.015
6(i4.053
3.400
2.3870
2!)4.123
1.5422
6.0(i3
()48.429
3.480
2.4055
287.361
1.5785
<>.11()
633,522
3.560
2.4238
280.904
1.6148
6.157
(i 19.286
3.640
2.4418
274.730
1.6510
6.202
605.676
3.720
2.4596
268.822
1.6873
6.247
592.650
3.800
2.4771
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
31.051
71.800
5.6410
13.928
32.5679
14.328
30.705
72.600
5.6619
13.774
32.9308
14.381
30.367
73.400
5.6826
13.624
33.2937
14.434
30.036
74.200
5.7031
13.477
33.6566
14.486
29.712
75.000
5.7236
13.333
34.0194
14.538
29.395
75.800
5.7438
13.193
34.3823
14.589
29.085
76.600
5.7640
13.055
34.7452
14.641
28.781
77.400
5.7840
12.920
35.1080
14.691
28.483
78.200
5.8038
12.788
35.4709
14.742
28.192
79.000
5.8236
12.658
35.8338
14.792
27.907
79.800
5.8432
12.531
36.1967
14.842
27.627
80.600
5.8626
12.407
36.5595
14.891
27.353
81.400
5.8820
12.285
36.9224
14.940
27.084
82.200
5.9012
12.165
37.2853
14.989
26.820
83.000
5.9202
12.048
37.6481
15.037
26.562
83.800
5.9392
11.933
38.0110
15.086
26.308
84.600
5.9580
11.820
38.3739
15.133
26.059
85.400
5.9768
11.710
38.7368
15.181
25.815
86.200
5.9954
11.601
39.0997
15.228
25.576
87.000
6.0139
11.494
39.4625
15.275
25.340
87.800
6.0322
11.390
39.8254
15.322
25.110
88.600
6.0505
11.287
40.1883
15.368
24.883
89.400
6.0687
11.186
40.5511
15.414
24.660
90.200
6.0867
11.086
40.9140
15.460
24.441
91.000
6.1046
10.989
41.2769
15.506
24.227
91.800
6.1225
10.893
41.6398
15.551
24.015
92.600
6.1402
10.799
42.0026
15.596
23.808
93.400
6.1578
10.707
42.3655
15.641
23.fi04
94.200
6.1754
10.616
42.7284
15.685
23.404
95.000
6.1928
10.526
43.0912
15.730
23.206
LENGTH-WEIGHT TABLES
453
Table 1-6.
C = 4,(){)() ^ 10
^, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GR.AMSI
(CM)
KILOGRAM
95.800
6.2101
10.438
43.4.541
15.774
23.013
96.600
6.2274
10.352
43.8170
15.818
22.822
97.400
6.2445
10.267
44.1799
15,861
22.635
98.200
6.2616
10.183
44.5427
15.904
22.450
99.000
6.2785
10.101
44.9056
15.947
22.269
99.800
6.2954
10.020
45.2685
15.990
22.090
106.000
6.4232
9.434
48.0807
16.315
20.798
114.000
6.5808
8.772
51.7095
16.715
19.339
122.000
6.7313
8.197
55.3382
17.098
18.071
130.000
6.8753
7.692
58.9669
17.463
16.9.59
138.000
7.0136
7.246
62..5957
17.814
15.976
146.000
7.1466
6.849
66.2244
18.152
15.100
154.000
7.2748
6.494
69.8531
18.478
14.316
162.000
7.3986
6.173
73.4819
18.793
13.609
170.000
. 7.5185
5.882
77.1106
19.097
12.968
178.000
7.6346
5.618
80.7394
19.392
12.386
186.000
7.7473
5.376
84.3681
19.678
11.853
194.000
7.8568
5.155
87.9968
19.9.56
11.364
202.000
7.9634
4.950
91.6256
20.227
10.914
210.000
8.0671
4.762
95.2543
20.491
10.498
218.000
8.1683
4.587
98.8830
20.747
10.113
226.000
8.2670
4.425
102.5118
20.998
9.7.55
234.000
8.3634
4.274
106.1405
21.243
9.421
242.000
8.4577
4.132
109.7692
21.483
9.110
250.000
8.5499
4.000
113.3980
21.717
8.818
258.000
8.6401
3.876
117.0267
21.946
8.545
266.000
8.7285
3.759
120.6.555
22.170
8.288
274.000
8.8152
3.650
124.2842
22.390
8.046
282.000
8.9001
3.546
127.9129
22.606
7.818
290.000
8.9835
3.448
131.5417
22.818
7.602
298.000
9.0654
3.356
135.1704
23.026
7.398
306.000
9.1458
3.268
138.7991
23.230
7.205
314.000
9.2248
3.185
142.4279
23.431
7.021
322.000
9.3025
3.106
146.0566
23.628
6.847
330.000
9.3789
3.030
149.6853
23.822
6.681
338.000
9.4541
2.959
153.3141
24.013
6.523
346.000
9.5281
2.890
156.9428
24.201
6.372
354.000
9.6009
2.825
160.5715
24.386
6.228
362.000
9.6727
2.762
164.2003
24.569
6.090
370.000
9.7435
2.703
167.8290
24.748
5.958
378.000
9.8132
2.646
171.4577
24.926
5.832
386.000
9.8819
2.-59 1
175.0865
25.100
5.7 1 1
394.000
9.9497
2.538
178.7152
25.272
5.595
454
FISH HATCHKRY MANAGEMENT
Table 1-7.
LENGTH-WKIGHI
r RELATIONSHIPS FOR FISH WITH C= 4,500 x
ur'
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.450
1.0000
2222.224
0.2041
2.540
4899.1.56
0.454
1.0030
2202.645
0.2059
2.548
4855.992
0.458
1 .0059
2183.408
0.2077
2.555
4813.582
0.462
1.0088
2164.504
0.2096
2.562
4771.906
0.466
1.0117
2145.925
0.2114
2.570
4730.945
0.470
1.0146
2127.662
0.2132
2.577
4690.684
0.474
1.0175
2109.707
0.2150
2..584
4651.102
0.478
1 .0203
2092.053
0.2168
2.592
4612.180
0.482
1.0232
2074.692
0.2186
2.,599
4573.906
0.486
1.0260
2057.616
0.2204
2.606
4.536.262
0.490
1.0288
2040.820
0.2223
2.613
4499.230
0.494
1.0316
2024.295
0.2241
2.620
4462.801
0.498
1.0344
2008.036
0.22.59
2.627
4426.9,53
0.504
1.0385
1984,127
0.2286
2.638
4374.246
0.512
1.0440
1953.125
0.2322
2.652
4305.898
0.520
1.0494
1923.078
0.23.59
2.665
4239.6.52
0.528
1.0547
1893.941
0.2395
2.679
4175.418
0.536
1.0600
1865.673
0.2431
2.692
4113.098
0.544
1.0653
1838.237
0.2468
2.706
4052.614
0.552
1.0705
1811.. 596
0.2.504
2.719
3993.881
0.560
1.0756
1785.717
0.2540
2.732
3936.826
0.568
1.0807
1760.566
0.2576
2.745
3881.379
0.576
1 .0858
1736.114
0.2613
2.758
3827.471
0.584
1.0908
1712.332
0.2649
2.771
3775.041
0.592
1 .0957
1689.192
0.2685
2.783
3724.027
0.600
1.1006
1666.670
0.2722
2.796
3674.374
0.608
1.1055
1644.740
0.2758
2.808
3626.028
0.616
1.1103
1623.380
0.2794
2.820
3578.937
0.624
1.1151
1602.568
0.2830
2.832
3533.053
0.632
1.1199
1582.283
0.2867
2.844
3488.332
0.640
1.1246
1562. ,504
0.2903
2.856
3444.728
0.648
1.1292
1.543.214
0.2939
2.868
3402.201
0.656
1.1339
1524.395
0.2976
2.880
3360.711
0.664
1.1385
1506.029
0.3012
2.892
3320.221
0.672
1.1430
1488.100
0.3048
2.903
3280.695
0.680
1.1475
1470.593
0.3084
2.915
3242.099
0.688
1.1520
1453.493
0.3121
2.926
3204.400
0.696
1.1565
1436.787
0.3157
2.937
3167..569
0.704
1.1609
1420.460
0.3193
2.949
3131.574
0.712
1.1653
1404.,500
0.3230
2.960
3096.388
0.720
1.1696
1388.894
0.3266
2.971
3061.984
0.728
1.1739
1373.632
0.3302
2.982
3028.336
0.736
1.1782
1358.701
0.3338
2.993
2995.420
0.744
1.1825
1344.092
0.3375
3.003
2963.211
0.752
1.1867
1329.793
0.3411
3.014
2931.688
0.760
1.1909
1315.795
0.3447
3.025
2900.828
LENGTH-WEIGHT TABLES
455
Table 1-7.
C = 4,.-)00 X 10 ■
, CONTINUED
WEIGHT,
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.768
1.1950
1302.089
0.3484
3.035
2870.612
0.776
1.1992
1288.666
0.3520
3.046
2841.018
0.784
1.2033
1275.516
0.3556
3.056
2812.028
0.792
1.2074
1262.632
0.3592
3.067
2783.624
0.800
1.2114
1 250.006
0.3629
3.077
2755.788
0.808
1.2154
1237.630
0.3665
3.087
2728..503
0.816
1.2194
1225.496
0.3701
3.097
2701.7.53
0.824
1.2234
1213.598
0.3738
3.107
2675.523
0.832
1.2274
1201.929
0.3774
3.117
2649.797
0.840
1.2313
1190.482
0.3810
3.127
2624..561
0.848
1.2352
1179.251
0.3846
3.137
2,599.801
0.856
1.2390
1168.230
0.3883
3.147
2575. .504
0.864
1.2429
1157.414
0.3919
3.157
2551.657
0.872
1.2467
1146.795
0.3955
3.167
2528.248
0.880
1.2505
1136.370
0.3992
3.176
2505.264
0.888
1.2.543
1126.132
0.4028
3.186
2482.694
0.896
1.2.580
1116.078
0.4064
3.195
2460.527
0.904
1.2618
1106.201
0.4100
3.205
2438.753
0.912
1.2655
1096.498
0.4137
3.214
2417.360
0.920
1.2692
1086.963
0.4173
3.224
2396.340
0.928
1.2729
1077. ,593
0.4209
3.233
2375.682
0.936
1.2765
1068.382
0.4246
3.242
23,55.377
0.944
1.2801
1059.328
0.4282
3.252
2335.417
0.952
1.2837
1050.427
0.4318
3.261
2315.791
0.960
1.2873
1041.673
0.4354
3.270
2296.493
0.968
1.2909
1033.064
0.4391
3.279
2277.514
0.976
1.2944
1024.596
0.4427
3.288
2258.846
0.984
1.2980
1016.266
0.4463
3.297
2240.481
0.992
1.3015
1008.071
0.4500
3.306
2222.413
1.000
1.3050
1000.000
0.4536
3.315
2204.620
1.080
1.3389
925.927
0.4899
3.401
2041.318
1.160
1.3711
862.072
0.5262
3.483
1900.541
1.240
1.4020
806.455
0..5625
3.561
1777.928
1.320
1.4315
757.580
0.5987
3.636
1670.177
1.400
1.4598
714.291
0.6350
3.708
1574.740
1.480
1.4871
675.681
0.6713
3.777
1489.620
1.560
1.5135
641.031
0.7076
3.844
1413.230
1.640
1.5389
609.762
0.7439
3.909
1344.293
1.720
1.5635
581.401
0.7802
3.971
1281.769
1.800
1.5874
555.562
0.8165
4.032
1224.802
1.880
1.6106
531.921
0.8527
4.091
1172.684
1.960
1.6331
510.210
0.8890
4.148
1124.820
2.040
1.65.50
490.202
0.9253
4.204
1080.709
2.120
1.6764
471.704
0.9616
4.258
1039.928
2.200
1.6972
454.552
0.9979
4.311
1002.113
2.280
1.7175
438.603
1.0342
4.363
966.952
456
FISH HATCHF.RY MANAGEMENT
Table 1-7.
C= 4,.TO()x 10 \
CONTINUED
WEIGHT/
1 ,()()()
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
2.360
1.7374
423.735
1.0705
4.413
934.174
2.440
1.7568
409.842
1.1067
4.462
903.546
2.520
1.7758
396.831
1.1430
4.511
874.862
2.600
1.7944
384.621
1.1793
4.558
847.944
2.680
1.8126
373.140
1.2156
4.604
822.632
2.760
1 .8305
362.324
1.2519
4.649
798.788
2.840
1.8480
352.118
1.2882
4.694
776.287
2.920
1.8652
342.471
1.3245
4.738
755.019
3.000
1.8821
333.339
1.3608
4.780
734.885
3.080
1.8986
324.681
1.3970
4.823
715.798
3.160
1.9149
316.461
1.4333
4.864
697.676
3.240
1.9310
308.647
1.4696
4.095
680.450
3.320
1.9467
301.210
1.5059
4.945
664.053
3.400
1.9622
294.123
1.5422
4.984
648.429
3.480
1.9775
287.361
1.5785
5.023
633.522
3.560
1.9926
280.904
1.6148
5.061
619.286
3.640
2.0074
274.730
1.6510
5.099
605.676
3.720
2.0220
268.822
1.6873
5.136
592.6,50
3.800
2.0364
263.163
1.7236
5.172
580.174
3.880
2.0506
257.737
1.7599
5.208
,568.211
3.960
2.0645
252.530
1.7962
5.244
-556.732
4.040
2.0784
247.529
1.8325
5.279
545.708
4.120
2.0920
242.723
1.8688
5.314
535.112
4.200
2.1054
238.100
1.90,50
5.348
524.919
4.280
2.1187
233.649
1.9413
5.382
515.108
4.360
2.1318
229.362
1.9776
5.415
,505.656
4.440
2.1448
225.230
2.0139
5.448
496.545
4.520
2.1576
221.243
2.0,502
5.480
487.757
4.600
2.1703
217.396
2.0865
5.512
479.274
4.680
2.1828
213.679
2.1228
5.544
471.082
4.760
2.1951
210.088
2.1591
5.576
463.164
4.840
2.2074
206.616
2.1953
5.607
455. ,509
4.920
2.2195
203.256
2.2316
5.637
448.102
5.000
2.2314
200.000
2.2680
5.668
440.924
5.400
2.2894
185.185
2.4494
5.815
408.263
5.800
2.3446
172.414
2.6308
5.955
380.107
6.200
2.3973
161.290
2.8123
6.089
3.55.584
6.600
2.4478
151.515
2.9937
6.217
334.034
7.000
2.4963
142.857
3.1751
6.341
314.946
7.400
2.5430
135.135
3.3566
6.4,59
297.922
7.800
2.5880
128.205
3.5380
6.573
282.644
8.200
2.6315
121.951
3.7194
6.684
268.856
8.()00
2.6736
116.279
3.9009
6.791
256.352
9.000
2.7144
111.111
4.0823
6.895
244.958
9.400
2.7540
106.383
4.2638
6.995
234.535
9.800
2.7926
102.041
4.4452
7.093
224.962
LENGTH-WEIGHT TABLES
457
Table 1-7.
C= 4,.i00> 10 ■
, CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB'
(INCHES)
POUND
'GRAMSl
(CM)
KILOGRAM
10.200
2.8301
98.039
4.6266
7.188
216.140
10.600
2.8666
94.340
4.8081
7.281
207.984
1 1 .000
2.9022
90.909
4.9895
7.372
200.421
11.400
2.9370
87.720
5.1709
7.460
193.388
11.800
2.9709
84.746
5.3524
7.546
186.833
12.200
3.0041
81.967
,5.5338
7.630
180.707
12.600
3.0366
79.365
5.7152
7.713
174.970
13.000
3.0684
76.923
5.8967
7.794
169.587
13.400
3.0995
74.627
6.0781
7.873
164.524
13.800
3.1301
72.464
6.2595
7.950
1.59.756
14.200
3.1600
70.423
6.4410
8.026
155.255
14.600
3.1894
68.493
6.6224
8.101
151.002
15.000
3.2183
66.667
6.8039
8.174
146.975
15.400
3.2467
64.935
6.9853
8.246
143.158
15.800
3.2745
63.291
7.1667
8.317
139.533
16.200
3.3019
61.728
7.3482
8.387
136.088
16.600
3.3289
60.241
7.5296
8.455
132.808
17.000
3.3554
58.824
7.7111
8.523
129.684
17.400
3.3815
57.471
7.8925
8.589
126.702
17.800
3.4072
56.180
8.0739
8.654
123.855
18.200
3.4326
54.945
8.2554
8.719
121.133
18.600
3.4575
53.764
8.4368
8.782
118.528
19.000
3.4821
52.632
8.6182
8.845
116.033
19.400
3.5064
51.546
8.7997
8.906
113.640
19.800
3.5303
50.505
8.9811
8.967
111.344
20.200
3.5540
49.505
9.1625
9.027
109.140
20.600
3.5773
48.544
9.3440
9.086
107.021
21.000
3.6003
47.619
9.5254
9.145
104.982
21.400
3.6230
46.729
9.7069
9.202
103.020
21.800
3.6454
45.872
9.8883
9.259
101.129
22.200
3.6676
45.045
10.0697
9.316
99.307
22.600
3.6895
44.248
10.2512
9.371
97..5.50
23.000
3.7111
43.478
10.4326
9.426
95.853
23.400
3.7325
42.735
10.6140
9.481
94.215
23.800
3.7537
41.017
10.79.55
9..534
92.631
24.200
3.7746
41.322
10.9769
9..587
91.100
24.600
3.7953
40.650
11.1583
9.640
89.619
25.000
3.8157
40.000
11.3398
9.692
88.185
25.800
3.8560
38.760
11.7027
9.794
85.4.50
26.600
3.8954
37.594
12.0656
9.894
82.880
27.400
3.9341
36.496
12.4285
9.993
80.460
28.200
3.9720
35.461
12.7913
10.089
78.178
29.000
4.0092
34.483
13.1.542
10.183
76.021
29.800
4.0458
33.557
13.5171
10.276
73.980
30.600
4.0817
32.680
13.8800
10.367
72.046
31.400
4.1169
31.847
14.2428
10.457
70.211
458
FISH HATCHERY MANAGEMENT
Table 1-7.
C = 4,500 X 1
0 , CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
32.200
4.1516
3 1 .056
14.6057
10.545
68.466
33.000
4.1857
30.303
14.9686
10.632
66.807
33.800
4.2192
29.586
15.3314
10.717
65.225
34.600
4.2523
28.902
15.6943
10.801
63.717
35.400
4.2848
28.249
16.0572
10.883
62.277
36.200
4.3168
27.624
16.4201
10.965
60.901
37.000
4.3484
27.027
16.7829
11.045
,59.,584
37.800
4.3795
26.455
17.1458
11.124
58.323
38.600
4.4102
25.907
17. .5087
1 1 .202
57.114
39.400
4.4405
25.381
17.8716
11.279
55.9.55
40.200
4.4703
24.876
18.2344
11.3,55
54.841
41.000
4.4998
24.390
18..5973
11.429
.53.771
41.800
4.5289
23.923
18.9602
11. .503
52.742
42.600
4.5576
23.474
19.3230
11.576
51.752
43.400
4.5859
23.041
19.6859
11.648
,50.798
44.200
4.6139
22.624
20.0488
11.719
49.878
45.000
4.6416
22.222
20.4117
11.790
48.991
45.800
4.6689
21.834
20.7745
11.8.59
48.136
46.600
4.6960
21.4,59
21.1374
11.928
47.309
47.400
4.7227
21.097
21. ,5003
11.996
46.511
48.200
4.7491
20.747
21.8632
12.063
45.739
49.000
4.77,52
20.408
22.2260
12.129
44.992
49.800
4.8011
20.080
22.5889
12.195
44.269
50.600
4.8267
19.763
22.9518
12.260
43.570
51.400
4.8520
19.455
23.3147
12.324
42.891
52.200
4.8770
19.157
23.6775
12.388
42.234
53.000
4.9018
18.868
24.0404
12.451
41.. 597
53.800
4.9263
18.587
24.4033
12.513
40.978
54.600
4.9506
18.315
24.7661
12.575
40.378
55.400
4.9747
18.051
25.1290
12.636
39.795
56.200
4.9985
17.794
25.4919
12.696
39.228
57.000
5.0221
17. ,544
25.8548
12.756
38.677
57.800
5.04,55
17.301
26.2176
12.816
38.142
58.600
5.0687
17.065
26.5805
12.874
37.621
59.400
5.0916
16.835
26.9434
12.933
37.115
60.200
5.1144
16.611
27.3063
12.991
36.622
61.000
5.1370
16.393
27.6691
13.048
36.141
61.800
5.1593
16.181
28.0320
13.105
35.673
62.600
5.1815
15.974
28.3949
13.161
35.218
63.400
5.2035
15.773
28.7578
13.217
34.773
64.200
5.2253
15.576
29.1206
13.272
34.340
65.000
5.2469
15.385
29.4835
13.327
33.917
65.800
5.2683
15.198
29.8464
13.381
33. .505
66.600
5.2896
15.015
30.2092
13.436
33.102
67.400
5.3107
14.837
30.5721
13.489
32.709
68.200
5.3316
14.663
30.9350
13.542
32.326
LENGTH-WEIGHT TABLES
459
Table 1-7. c = 4,500 x 10
CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
69.000
69.800
70.600
71.400
72.200
73.000
73.800
74.600
75.400
76.200
77.000
77.800
78.600
79.400
80.200
8L000
8L800
82.600
83.400
84.200
8.5.000
8,1.800
86.600
87.400
88.200
89.000
89.800
90.600
9L400
92.200
93.000
93.800
94.600
9.5.400
96.200
97.000
97.800
98.600
99.400
102.000
110.000
118.000
126.000
134.000
142.000
1.50.000
.5.3524
.5.3730
5.3934
5.4137
5.4339
5.4539
5.4737
5.4934
5.5130
5.5324
5.5517
5.5709
5.5899
5.6088
5.6276
5.6462
5.6647
5.6832
5.7014
5.7196
5.7377
5,75.56
5.7734
5.7912
5.8088
5.8263
5.8437
5.8610
5.8782
5.8953
5.9123
5.9292
5.9460
5.9627
5.9793
5.99.59
6.0123
6.0287
6.0449
6.0972
6.2526
6.4006
6.5421
6.6778
6.8081
6.9337
14.493
14.327
14.164
14.006
13.850
13.699
13.5,50
13.405
13.263
13.123
12.987
12.853
12.723
12..594
12.469
12.346
12.225
12.107
11.990
11.876
11.765
11.655
11.547
11.442
11.338
11.236
11.136
11.038
10.941
10.846
10.753
10.661
10.571
10.482
10.395
10.309
10.225
10.142
10.060
9.804
9.091
8.475
7.937
7.463
7.042
6.667
31.2979
31.6607
32.0236
32.3865
32.7494
33.1122
33.4751
33.8380
34.2009
34.5637
34.9266
35.2895
35.6523
35.0152
36.3781
36.7410
37.1038
37.4667
37.8296
38.1925
38.5553
38.9182
39.2811
39.6440
40.0068
40.3697
40.7326
41.0955
41.4583
41.8212
42.1841
42.5470
42.9098
43.2727
43.6356
43.9984
44.3613
44.7242
45.0871
46.2664
49.8951
53.5238
57.1526
60.7813
64.4100
68.0388
13.595
13.647
13.699
13.751
13.802
13.853
13.903
13.953
14.003
14.052
14.101
14.1.50
14.198
14.246
14.294
14.341
14.388
14.435
14.482
14.528
14.574
14.619
14,665
14.710
14.754
14,799
14.843
14.887
14.931
14.974
15.017
15.0()0
15.103
15.145
15.188
15.230
15.271
15.313
15.354
15.487
15.882
16.258
16.617
16.961
17.293
17.611
31.951
31.585
31.227
30.877
30.535
30.200
29.873
29.553
29.239
28,932
28.631
28,337
28,049
27,766
27,489
27,217
26,951
26,690
26.434
26.183
25.937
25.695
25.457
25.224
24.996
24.771
24.5,50
24.334
24.121
23.911
23.706
23..503
23.305
23.109
22.917
22.728
22.542
22.359
22.179
21.614
20.042
18.683
17.497
16.452
15.525
14.697
460
KISH HATCHERY MANAGEMENT
Table 1-7. c- 4,500 x 10
CONTINUED
WEIGHT/
1, ()()()
LENGTH
FISH/
WEIGHT
LENGIH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
158. ()()()
7.0547
6.329
71.6675
17.919
13.953
1()().(){)()
7.1719
6.024
75.2962
18.217
13.281
174.000
7.2853
5.747
78.9250
18. ,505
12.()70
1K2.00()
7.3953
5.495
82.5537
18.784
12.113
190.000
7. ,5021
5.263
86.1825
19.055
1 1 .603
198.000
7.6059
5.051
89.8112
19.319
11.134
206.000
7.7070
4.854
93.4399
19.576
10.702
214.000
7.8055
4.673
97.0687
19.826
10.302
222.000
7.9016
4.505
100.6974
20.070
9.931
230.000
7.9954
4.348
104.3261
20.308
9.585
238.000
8.0870
4.202
107.9549
20.541
9.263
24(i.()00
8.1766
4.065
111.0006
20.769
8,962
254.000
8.2643
3.937
115.2123
20.991
8.680
262.000
8.3502
3.817
118.8411
21.209
8.415
270.000
8.4343
3.704
122.4698
21.423
8.165
278.000
8.5168
3.597
126.0986
21.633
7.930
286.000
8.5977
3.497
129.7273
21.838
7.708
294.000
8.6772
3.401
133.3560
22,040
7.499
302.000
8.7552
3.311
136,9848
22.238
7.300
310.000
8.8318
3.226
140.6135
22.433
7.112
318.000
8,9071
3.145
144.2422
22.624
6.933
326.000
8.9812
3.067
147.8710
22.812
6.763
334.000
9.0541
2.994
151.4997
22.997
6.601
342.000
9.1258
2.924
155.1284
23.180
6.446
350.000
9.1964
2.857
158.7572
23.3.59
6.299
358.000
9.2660
2.793
162.3859
23.536
6.1,58
366.000
9.3345
2.732
166.0146
23.710
6.024
374.000
9.4020
2.674
169.6434
23.881
5.895
382.000
9.4685
2.618
173.2721
24.0,50
5.771
390.000
9.5342
2.564
1 76.9008
24.217
5.653
398.000
9.5989
2.513
180.5296
24.381
5.539
406,000
9.6628
2.463
184.1583
24.544
5.430
414.000
9.7259
2.415
187.7871
24.704
5.325
422.000
9,7881
2.370
191.4158
24.862
5.224
430.000
9.8496
2.326
195.0445
25.018
5.127
438.000
9.9103
2.283
198.6733
25.172
5.033
446.000
9.9703
2.242
202.3020
25.324
4.943
LENG TH-WEIGHT TABLES
461
Table 1-8.
LENGTH-WEIGHT RELATIONSHIPS FOR FISH WITH C= .5,000 x
ur'
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (lb;
iINCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
0.500
1 .0000
2000.001
0.2268
2.540
4409.242
0.50fi
1.0040
1976.285
0.2295
2.5.50
4356.953
0.514
1 .0092
1945.526
0.2331
2.563
4289.145
0.522
1.0145
1915.710
0.2368
2.577
4223.410
0.530
1.0196
1886.794
0.2404
2.590
4159.660
0.538
1.0247
1858.738
0.2440
2.603
4097.809
0.546
1.0298
1831.504
0.2477
2.616
4037.770
0.554
1.0348
1805.056
0.2513
2.628
3979.463
0.562
1.0397
1779.362
0.2549
2.641
3922.817
0.570
1.0446
1754.389
0.2585
2.653
3867.760
0.578
1.0495
1730.107
0.2622
2.666
3814.228
0.586
1.0543
1706.488
0.2658
2.678
3762.157
0.594
1.0591
1683.505
0.2694
2.690
3711.489
0.602
1.0638
1661.133
0.2731
2.702
3662.167
0.610
1.0685
1639.348
0.2767
2.714
3614.139
0.618
1.0732
1618.127
0.2803
2.726
3567.355
0.626
1.0778
1597.448
0.2839
2.738
3521.766
0.634
1.0824
1577.291
0.2876
2.749
3477.328
0.642
1.0869
1557.637
0.2912
2.761
3433.997
0.650
1.0914
1538.466
0.2943
2.772
3391.733
0.658
1.0959
1519.761
0.2985
2.783
33.50.496
0.666
1.1003
1501.506
0.3021
2.795
3310.250
0.674
1.1047
1483.684
0.3057
2.806
3270.960
0.682
1.1090
1466.281
0.3093
2.817
3232.592
0.690
1.1133
1449.280
0.3130
2.828
3195.113
0.698
1.1176
1432.670
0.3166
2.839
31.58.493
0.706
1.1219
1416.436
0.3202
2.850
3122.703
0.714
1.1261
1400.565
0.3239
2.860
3087.715
0.722
1.1303
1385.047
0.3275
2.871
3053.502
0.730
1.1344
1369.868
0.3311
2.881
3020.039
0.738
1.1386
1355.019
0.3347
2.892
2987.302
0.746
1.1427
1340.488
0.3384
2.902
2955.267
0.754
1.1467
1326.266
0.3420
2.913
2923.912
0.762
1.1508
1312.342
0.3456
2.923
2893.215
0.770
1.1548
1298.707
0.3493
2.933
2863.156
0.778
1.1588
1285.353
0.3529
2.943
2833.715
0.786
1.1627
1272.271
0.3565
2.953
2804.873
0.794
1.1667
1259.452
0.3602
2.963
2776.613
0.802
1.1706
1246.889
0.3638
2.973
2748.916
0.810
1.1745
1234.574
0.3674
2.983
2721.766
0.818
1.1783
1222.500
0.3710
2.993
2695.148
0.826
1.1821
1210.660
0.3747
3.003
2669.045
0.834
1.1859
1199.047
0.3783
3.012
2643.443
0.842
1.1897
1187.655
0.3819
3.022
2618.327
0.850
1.1935
1176.477
0.3856
3.031
2593.684
0.858
1.1972
1165.507
0.3892
3.041
2569.501
462
FISH HATCHERY MANAGEMENT
Table 1-8.
C = .5,000 X 10
', CONTINUED
WKKJHIV
1,00(1
LENGTH
FISH/
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
PCJUND
(GRAMS)
(CM)
KILOGRAM
(),8(i(i
1,2009
11.54.740
0.3928
3.050
2545.764
0,S74
1.2046
1144.171
0.3964
3.060
2522.462
0.882
1.2083
1133.793
0.4001
3.069
2499.583
0.890
1.211!)
1123.602
0.4037
3.078
2477.115
0.898
1.21.5,'-)
1113.,592
0,4073
3.087
2455.047
0.906
1.2191
1103.7,59
0,4110
3.097
2433.369
0.914
1.2227
1094,098
0,4146
3.106
2412,071
0.922
1,2263
1084.60,5
0.4182
3.115
2391,142
0.930
1.2298
107,5,27,5
0,4218
3.124
2370,573
0.938
1.2333
1066.104
0,425,5
3.133
23.50,355
0.946
1.2368
10,57,089
0,4291
3.142
2330,479
0.9.54
1.2403
1048,224
0,4327
3.150
2310.936
0.9(i2
1.2438
1()39„507
0,4364
3.159
2291.719
0.970
1.2472
1030,934
0,4400
3.168
2272.818
0.978
1.2.506
1022, .501
0,4436
3.177
2254.227
0.986
1.2.540
1014.205
0,4472
3.185
2235.937
0.994
1.2.574
10()().()42
0.4509
3.194
2217.941
1.020
1.2683
980.393
0.4627
3.221
2161.393
1,100
1.3006
909.093
0.4990
3.303
2004.204
1.180
1.3314
847.461
0.53,52
3.382
1868.329
1,2()0
1.3608
793.6,5,5
0.5715
3.456
1749.707
1,340
1.3890
746.273
0.6078
3.528
1645.249
1,420
1.4161
704.230
0.6441
3.597
1552. .561
1,.500
1.4422
666.672
0.6804
3.663
1469.7.59
1,.S80
1.4674
632.917
0.7167
3.727
1395.342
1,660
1.4918
602.416
0.7530
3.789
1328.097
1,740
1.. 5 1.54
.574.719
0.7892
3.849
1267.036
1,820
l.,5383
.549.4.57
0.8255
3.907
1211.343
1,900
1., 560,5
,526.322
0.86)18
3.964
1160.340
1.980
l.,5821
.50.5.0.57
0.8981
4.018
1113.4.58
2.060
1.6031
48.5.443
0.9344
4.072
1070.217
2.140
1.6236
467.296
0.9707
4.124
1030.210
2.220
1 .6436
4.50.4,57
1.0070
4.175
993.085
2.300
1.6631
434.789
1.0432
4.224
958.544
2.380
1,6822
420.174
1.0795
4.273
926.324
2.460
1,7008
406..510
1.1158
4.320
896.200
2..')40
1,7190
393.707
1.1521
4.366
867.973
2,620
l,73<i9
381.68.5
1.1884
4.412
841.471
2.700
1,7,544
370.376
1.2247
4.456
816.539
2.780
1,7716
3.59.718
1.2610
4.. 500
793.041
2.860
1,7884
349.6.56
1.2973
4.543
770.858
2.940
1,8049
340.142
1.3335
4.584
74!), 883
3,020
1,8211
331.131
1.3698
4.626
730,019
3,100
1,8371
322..586
1.4061
4.666
711.179
3.180
1,8.527
314.471
1.4424
4.706
693.288
3.260
1.8682
306.7.54
1.4787
4.745
676.275
LENGTH-WEIGHT TABLES
463
Table 1-8.
C = .i,000 X 10 ■
', CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH'
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
3.340
1.8833
299.406
1.51,50
4,784
660.077
3.420
1.8982
292.403
1.5513
4,822
644.637
3..")00
1 .9 1 29
285.719
1.5875
4,859
629.902
3..580
1.9274
279.334
1.6238
4.896
615.826
3.660
1.9416
273.229
1.6601
4.932
602.366
3.740
1.9557
267.385
1.6964
4,967
589.481
3.820
1 .9695
261.785
1.7327
5,003
577.136
3.900
1 .9832
256.415
1.7690
5.037
.565.297
3.980
1.9966
251.261
1.8053
5.07 1
553.935
4.060
2.0099
246.310
1.8415
5.105
543.020
4.140
2.0231
241.550
1.8778
5.139
532.527
4.220
2.0360
236.971
1.9141
5.171
522.432
4.300
2.0488
232.563
1.9504
5.204
512.712
4.380
2.0614
228.315
1.9867
5.236
503.347
4.460
2.0739
224.220
2.0230
5,268
494.319
4.540
2.0862
220.269
2.0593
5.299
485.608
4.620
2.0984
216.454
2.0956
5.330
477.200
4.700
2.1104
212.770
2.1318
5.361
469.077
4.780
2.1223
209.209
2.1681
5.391
461.227
4.860
2.1341
205.765
2.2044
5.421
453.634
4.940
2.1458
202.433
2.2407
5.4,i0
446.288
5.100
2.1687
196.078
2.3133
5.509
432.278
5.500
2.2240
181.818
2.4948
5.649
400.840
5.900
2.2766
169.492
2.6762
5,783
373.665
6.300
2.3270
158.730
2.8576
5.910
349.940
6.700
2.3752
149.254
3.0391
6.033
329,048
7.100
2.4216
140.845
3.2205
6.151
310.510
7.500
2.4662
133.334
3.4019
6.264
293.950
7.900
2.5093
126.583
3.5834
5.374
279.066
8.300
2.5510
120.482
3.7648
6.479
265.617
8.700
2.5913
114.943
3,9462
6..582
253.405
9.100
2.6304
109.890
4.1277
6.681
242.267
9.500
2.6684
105.263
4.3091
6.778
232.066
9.900
2.7053
101.010
4,4905
6.872
222.689
10.300
2.7413
97.088
4,6720
6.963
214.041
10.700
2.7763
93.458
4,8534
7.052
206.040
11.100
2.8105
90.090
5,0349
7.139
198.615
11.. 500
2.8439
86.957
5,2163
7.223
191.707
11.900
2.8765
84.034
5,3977
7.306
185.263
12.300
2.9083
81.301
5,5792
7.387
179.238
12.700
2.9395
78.740
5,7606
7.466
173„593
13.100
2.9701
76.336
5,9420
7.544
168,292
13.500
3.0000
74.074
6,1235
7.620
163.306
13.900
3.0293
71.943
6,3049
7.695
158.606
14.300
3.0581
69.930
5,4863
7.768
1.54.170
14.700
3.0864
68.027
6,6678
7.839
149,975
464
FISH HATCHERY MANAGEMENT
Table 1-8.
C = .S.OOO X 10 ■
' , CONTINUED
WEIGHT/
1, ()()()
LENGTH
FISH/
WEIGH r
LENC/IH
ELSH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
15.100
3.1141
66.225
6.8492
7.910
14(i.()02
15.-500
3.1414
64.516
7.0306
7.979
142.234
15.900
3.1682
62.893
7.2121
8.047
138.656
Hi. 300
3.1945
61.350
7.3935
8.1 14
135.253
l(i.7()0
3.2204
59.880
7.5750
8.180
132.013
17.100
3.2460
58.480
7.7564
8.245
128.925
17.500
3.2711
57.143
7.9379
8.309
125.978
17.900
3.2958
55.866
8.1193
8.371
123.163
iH.aoo
3.3202
54.645
8.3007
8.433
120.471
18.700
3,3442
53.476
8.4822
8.494
117.894
19.100
3.3679
52.356
8.6636
8.554
115.425
19.500
3.3912
51.282
8.8450
8.614
113.058
19.900
3.4142
,50.251
9.0265
8.672
110.785
20.300
3.4370
49.261
9.2079
8.730
108.602
20.700
3.4594
48.309
9.38!)3
8.787
106.503
21.100
3.4815
47.393
9.5708
8.843
104.484
21.500
3.5034
46.512
9.7522
8.899
102.541
21.900
3.5250
45.662
9.9337
8.953
100.668
22.300
3.5463
44.843
10.1151
9.008
98.862
22.700
3.5674
44.053
10.2965
9.061
97.120
23.100
3.5882
43.290
10.4780
9.114
95.438
23.500
3.6088
42.553
10.6594
9.166
93.814
23.900
3.6292
41.841
10,8408
9.218
92.244
24.300
3.6493
41.152
11.0223
9.269
90.725
24.700
3.6692
40.486
11.2037
9.320
89.256
25.200
3.6938
39.682
11.4305
9.382
87.485
26.000
3.7325
38.461
11.7934
9.481
84.793
26.800
3.7704
37.313
12.1563
9.577
82.262
27.600
3.8076
36.232
12.5192
9.671
7!). 877
28.400
3.8440
35.211
12.8820
9.764
77.(i27
29.200
3.8798
34.246
13.2449
9.855
75.500
30.000
3.9149
33.333
13.6078
9.944
73.487
30.800
3.9494
32.467
13.9707
10.031
71.578
31.600
3.9833
31.645
14.3335
10.117
69.766
32.400
4.0166
30.864
14.6964
10.202
68.044
33.200
4.0494
30.120
15.0593
10.285
66.404
34.000
4.0817
29.412
15.4222
10.367
64.842
34.800
4.1134
28.736
15.78,50
10.448
63.351
35.600
4.1447
28.090
16.1479
10.528
61.927
36.400
4.1755
27.472
16.5108
10.606
60.566
37.200
4.2059
26.882
16.8736
10.683
59.264
38.000
4.2358
26.316
17.2365
10.7,59
58.016
38.800
4.2653
25.773
17.5994
10.834
56.820
39.600
4.2945
25.252
17.9623
10.908
55.672
40.400
4.3232
24.752
18.3251
10.981
54.570
41.200
4.3515
24.272
18.6880
1 1 .053
53.510
LENGTH-WEIGHT TABLES
465
Table 1-8.
C = ."S.OOO X 10
', CONTINUED
WEIGHT/
1,000
LENGTH
FISH/
WEIGHT
LENGTH
FISH'
FISH (LB)
(INCHES)
POUND
GR.^MS
ICM)
KILOGR.-\.M
42.000
4.3795
23.809
1!).05()!)
11.124
52.491
42.800
4.4072
23.364
19.4138
11.194
51.510
43.(i00
4.4344
22.936
19.7766
11.263
.50.565
44.400
4.4614
22.522
20.1395
11.332
49.654
4.'). 200
4.4880
22.124
20.5024
11.400
48.775
4(),0()()
4.5144
21.739
20.8652
11.466
47.926
4f).800
4.5404
21.367
21.2281
11.533
47.107
47.fi00
4.5661
21.008
21.5910
11.598
46.315
48.400
4.,')915
20.661
21.9539
11.663
45.550
49.200
4.6167
20.325
22.3167
11.726
44.809
.50.000
4.6416
20.000
22.6796
11.790
44.092
50.800
4.6662
19.685
23.0425
11.852
43.398
51.600
4.6906
19.380
23.4054
11.914
42.725
52.400
4.7147
19.084
23.7682
11.975
42.073
53.200
4.7386
18.797
24.1311
12.036
41.440
54.000
4.7622
18.518
24.4940
12.096
40.826
54.800
4.7856
18.248
24.8569
12.155
40.230
55.600
4.8088
17.986
25.2197
12.214
39.651
56.400
4.8317
17.730
25.5826
12.273
39.089
57.200
4.8545
17.482
25.9455
12.330
38.542
58.000
4.8770
17.241
26.3084
12.288
38.011
58.800
4.8993
17.007
26.6712
12.444
37.493
59.600
4.9214
16.779
27.0341
12.500
36.990
60.400
4.9434
16.5.56
27.3970
12.556
36.500
61.200
4.9651
16.340
27.7599
12.611
36.023
62.000
4.9866
16.129
28.1227
12.666
35.558
62.800
5.0080
15.924
28.4856
12.720
35.105
63.600
5.0292
15.723
28.8485
12.774
34.664
64.400
5.0502
15.528
29.2113
12.827
34.233
65.200
5.0710
15.337
29.5742
12.880
33.813
66.000
5.0916
15.151
29.9371
12.933
33.403
66.800
5.1121
14.970
30.3000
12.985
33.003
67.600
5.1325
14.793
30.6628
13.036
32.613
68.400
5.1526
14.620
31.0257
12.088
32.231
69.200
5.1726
14.451
31.3886
13.138
31.859
70.000
5.1925
14.286
31.7515
13.189
31.495
70.800
5.2122
14.124
32.1143
13.239
31.139
71.600
5.2318
13.966
32.4772
13.289
30.791
72.400
5.2512
13.812
32.8401
13.338
30.451
73.200
5.2704
13.661
33.2030
13.387
30.118
74.000
5.2896
13.514
33.5658
13.436
29.792
74.800
5.3086
13.369
33.9287
13.484
29.473
75.600
5.3274
13.228
34.2916
13.532
29.162
76.400
5.3461
13.089
34.6544
13.579
28.8.56
77.200
5.3647
12.953
35.1073
13.626
28.557
78.000
5.3832
12.821
35.3802
13.673
28.264
466
FISH HATCHERY MANAGEMENT
Table 1-8.
C = .'■),000 X W '
', CONTINUED
WEIGHT/
1,000
LENGTH
ITSH/
WEIGHT
LENGTH
EI.SII/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
78.800
,5.4016
12.690
35.7431
13.720
27.977
79.600
,5.4198
12.563
36.10.59
13.766
27.696
80.400
,5.4379
12.438
36.4688
13.812
27.421
81.200
,5.4,5,58
12.315
36.8317
13.8.58
27.150
82.000
,5.4737
12.195
37.1946
13.903
26.88(i
82.800
,5.4914
12.077
37.5574
13.948
26.626
83.600
,5.,5091
11.962
37.9203
13.993
26.371
84.400
,5. ,5266
11.848
38.2832
14.038
26.121
8,5.200
,5..5440
11.737
38.6461
14.082
25.876
86.000
,5.,5613
, 11.628
39.0089
14.126
25.635
86.800
,5. ,578.5
11. .521
39.3718
14.169
25.399
87.600
,5. ,59,56
11.416
39.7347
14.213
25.167
88.400
,5.6126
11.312
40.0975
14.2,56
24.939
89.200
.5.6294
1 1.211
40.4604
14.299
24.715
90.000
,5.6462
11.111
40.8233
14.341
24.496
90.800
.5.6629
11.013
41.1862
14.384
24.280
91.600
,5.679.5
10.917
41. ,5490
14.426
24.068
92.400
.5.6960
10.823
41.9119
14.468
23.8,59
93.200
,5.7124
10.730
42.2748
14.. 509
23.655
94.000
,5.7287
10.638
42.6377
14.551
23.4,53
94.800
,5.7449
10.549
43.0005
14. .592
23.255
9,5.600
,5.7610
10.460
43.3634
14.633
23.061
96.400
,5.7770
10.373
43.7263
14.674
22.869
97.200
,5.7929
10.288
44.0892
14.714
22.681
98.000
,5.8088
10.204
44.4520
14.754
22.496
98.800
.5.824,5
10.121
44.8149
14.794
22.314
99.()00
,5.8402
10.040
45.1778
14.834
22.135
104.000
,5.92.50
9.615
47.1736
15.049
21.198
112.000
6.0732
8.929
50.8023
15.426
19.684
120.000
6.214,5
8.333
54.4310
15.785
18.372
128.000
6.3496
7.813
58.0598
16.128
17.224
136.000
6.4792
7.353
61.6885
16.457
16.210
144.000
6.6039
6.944
65.3172
16.774
15.310
1,52.000
6.7239
6.579
68.9460
17.079
14. .504
160.000
6.8399
6.250
72.5747
17.373
13.779
168.000
6.9,521
5.9.52
76.2034
17.658
13.123
176.000
7.0607
5.682
79.8322
17.934
12.526
184.000
7.1661
5.435
83.4609
18.202
11.982
192.000
7.268,5
5.208
87.0896
18.462
11.482
200.000
7.3681
5.000
90.7184
18.715
11.023
208,000
7.46,50
4.808
94.3471
18.961
10.599
216.000
7. .5,59,5
4.630
97.9758
19.201
10.207
224.000
7.6.517
4.464
101.6046
10.435
9.842
232.000
7.7417
4.310
105.2333
19.664
9.503
240.000
7.8297
4.167
108.8621
19.887
9.186
248.000
7.91.58
4.032
112,4908
20.106
8.890
LENGTH-WEIGHT TABLES
467
Table 1-8.
C = .'),0{)() X 10 ■
', CONTINUED
WEIGHT/
1,000
LENGTH
FISH
WEIGHT
LENGTH
FISH/
FISH (LB)
(INCHES)
POUND
(GRAMS)
(CM)
KILOGRAM
25fi.()0()
8.0000
3.90(i
IK). 11 95
20.320
8.(il2
264.000
8.0825
3.788
119.7483
20.529
8.351
272.000
8.1633
3.676
123.3770
20.735
8.105
280.000
8.2426
3.571
127.0057
20.936
7.874
288.000
8.3203
3.472
130.6345
21.134
7.655
296.000
8.3967
3.378
134.2632
21.328
7.448
304.000
8.4716
3.289
137.8919
21.518
7.252
312.000
8.5453
3.205
141.5207
21.705
7.066
320.000
8.6177
3.125
145.1494
2 1 .889
6.889
328.000
8.6890
3.049
148.7782
22.070
6.721
336.000
8.7.590
2.976
152.4069
22.248
6..561
344.000
8.8280
2.907
156.03.56
22.423
6.409
352.000
8.89.59
2.841
159.6644
22.596
6.263
360.000
8.9628
2.778
163.2931
22.766
6.124
368.000
9.0287
2.717
166.9218
22.933
5.991
376.000
9.0937
2.660
170.5506
23.098
5.863
384.000
9.1577
2.604
174.1793
23.261
5.741
392.000
9.2209
2.551
177.8080
23.421
5.624
4()().()()()
9.2832
2.500
181.4368
23.579
5.512
408.000
9.3447
2.451
185.0655
23.735
5.403
416.000
9.4053
2.404
188.6942
23.890
5.300
424.000
9.4652
2.358
192.3230
24.042
5.200
432.000
9.5244
2.315
195.9517
24.192
5.103
440.000
9..5828
2.273
199.5804
24.340
5.010
448.000
9.6406
2.232
203.2092
24.487
4.921
456.000
9.6976
2.193
206.8379
24.632
4.835
464.000
9.7540
2.155
210.4667
24.775
4.751
472.000
9.8097
2.119
214.0954
24.917
4.671
480.000
9.8648
2.083
217.7241
25.057
4.593
488.000
9.9193
2.049
221.3529
25.195
4.518
496.000
9.9733
2.106
224.9816
25.332
4.445
Glossary
Abdomen Belly; the ventral side of the fish surrounding the digestive
and reproductive organs.
Abdominal Pertaining to the belly.
Abrasion A spot scraped of skin, mucous membrane, or superficial
epithelium.
Abscess A localized collection of necrotic debris and white blood cells
surrounded by inflamed tissue.
Acclimatization The adaptation of fishes to a new environment or habi-
tat or to different climatic conditions.
Acre-Foot A water volume equivalent to that covering a surface area of
one acre to a depth of one foot; equal to 326,000 gallons or 2,718,000
pounds of water.
Acriflavin A mixture of 2,8-diamino- lO-methylacridinium chloride and
2,8-diaminoacridine. Used as an external disinfectant, especially of liv-
ing fish eggs.
Activated Sludge Process A system in which organic waste continually
is circulated in the presence of oxygen and digested by aerobic bac-
teria.
Acute Having a short and relatively severe course; for example, acute
inflammation.
Acute Catarrhal Enteritis See Infectious Pancreatic Necrosis.
469
470 FISH HAICHKRY MANAGEMENT
Acute Toxicity Causing death or severe damage to an organism by poi-
soning during a brief exposure period, normally 96 hours or less. See
Chronic.
Adaptation The process by which individuals (or parts of individuals),
populations, or species change in form or function in order to better
survive under given or changed environmental conditions. Also the
result of this process.
Adipose Fin A small fleshy appendage located posterior to the main
dorsal fin; present in Salmonidae and Ictaluridae.
Adipose Tissue Tissue capable of storing large amounts of neutral fats.
Aerated Lagoon A waste treatment pond in which the oxygen required
for biological oxidation is supplied by mechanical aerators.
Aeration The mixing of air and water by wind action or by air forced
through water; generally refers to a process by which oxygen is added
to water.
Aerobic Referring to a process (for example, respiration) or organism
(for example, a bacterium) that requires oxygen.
Air The gases surrounding the earth; consists of approximately 78"(i
nitrogen, 21'/o oxygen, 0.9''i) argon, 0.03"ii carbon dioxide, and minute
quantities of helium, krypton, neon, and xenon, plus water vapor.
Air Bladder (Swim bladder). An internal, inflatable gas bladder that
enables a fish to regulate its buoyancy.
Air Stripping Removal of dissolved gases from water to air by agitation
of the water to increase the area of air-water contact.
Alevin A life stage of salmonid fish between hatching and feeding when
the yolk sac still is present. Equivalent to sac fry in other fishes.
Algal Bloom A high density or rapid increase in abundance of algae.
Algal Toxicosis A poisoning resulting from the uptake or ingestion of
toxins or toxin-producing algae; usually associated with blue-green
algae or dinoflagellate blooms in fresh or marine water.
Alimentary Tract The digestive tract, including all organs from the
mouth to the anal opening.
Aliquot An equal part or sample of a larger quantity.
Alkalinity The power of a mineral solution to neutralize hydrogen ions;
usually expressed as equivalents of calcium carbonate.
Amino Acid A building block for proteins; an organic acid containing
one or more amino groups ( — NH7) and at least one carboxylic acid
group (-COOH).
Ammonia The gas NH^; highly soluble in water; toxic to fish in the
un-ionized form, especially at low oxygen tensions.
Ammonia Nitrogen Also called total ammonia. The summed weight of
nitrogen in both the ionized (ammonium, NHj*") and molecular (NHJ
forms of dissolved ammonia ( NH4 — N plus NH3 — N). Ammonia
values are reported as N (the hydrogen being ignored in analyses).
GLOSSARY 471
Ammonium The ionized form of ammonia, NH4 .
Anabolism Constructive metabolic processes in living organisms: tissue
building and growth.
Anadromous Fish Fish that leave the sea and migrate up freshwater
rivers to spawn.
Anaerobic Referring to a process or organism not requiring oxygen.
Anal Pertaining to the anus or vent.
Anal Fin The fin on the ventral median line behind the anus.
Anal Papilla A protuberance in front of the genital pore and behind
the vent in certain groups of fishes.
Anchor Ice Ice that forms from the bottom up in moving water.
Anemia A condition characterized by a deficiency of hemoglobin,
packed cell volume, or erythrocytes. The more important anemias in
fish are (l) normocytic anemia caused by acute hemorrhaging, bac-
terial and viral infection, or metabolic disease; (2) microcytic anemia
due to chronic hemorrhaging, iron deficiency, or deficiency of certain
hematopoietic factors; (S) macrocytic anemia resulting from an
increase in hematopoietic activity in the spleen and kidney.
Anesthetics Chemicals used to relax fish and facilitate the handling and
spawning of fish. Commonly used agents include tricane methane sul-
fonate (MS-222), benzocain, quinaldine, and carbon dioxide.
Annulus A yearly mark formed on fish scales when rapid growth
resumes after a period (usually in winter) of slow or no growth.
Anoxia Reduction of oxygen in the body to levels that can result in tis-
sue damage.
Anterior In front of; toward the head end.
Anthelmintic An agent that destroys or expels worm parasites.
Antibiotic A chemical produced by living organisms, usually molds or
bacteria, capable of inhibiting other organisms.
Antibody A specific protein produced by an organism in response to a
foreign chemical (antigen) with which it reacts.
Antigen A large protein or complex sugar that stimulates the formation
of an antibody. Generally, pathogens produce antigens and the host
protects itself by producing antibodies.
Antimicrobial Chemical that inhibits microorganisms.
Antioxidant A substance that chemically protects other compounds
against oxidation; for example, vitamin E prevents oxidation and ran-
cidity of fats.
Antiseptic A compound that kills or inhibits microorganisms, especially
those infecting living tissues.
Antivitamin Substance chemically similar to a vitamin that can replace
the vitamin or an essential compound, but cannot perform its role.
Anus The external posterior opening of the alimentary tract; the vent.
Aquaculture Culture or husbandry of aquatic organisms.
Artery A blood vessel carrying blood away from the heart.
472 riSH HAICHERY MANAGKMENT
Ascites The accumulation of serum-like fluid in the abdomen.
Ascorbic Acid Vitamin C, a water-soluble antioxident important for the
production of connective tissue; deficiencies cause spinal abnormalities
and reduce wound- healing capabilities.
Asphyxia Suffocation caused by too little oxygen or too much carbon
dioxide in the blood.
Asymptomatic Carrier An individual that shows no signs of a disease
but harbors and transmits it to others.
Atmosphere The envelope of gases surrounding the earth; also, pressure
equal to air pressure at sea level, approximately 14.7 pounds per
square inch.
Atrophy A degeneration or diminution of a cell or body part due to
disuse, defect, or nutritional deficiency.
Auditory Referring to the ear or to hearing.
Autopsy A medical examination of the body after death to ascertain the
cause of death.
Available Energy Energy available from nutrients after food is digested
and absorbed.
Available Oxygen As used in this text, that oxygen present in the
water in excess of the amount required for minimum maintenance of a
species, and that can be used for metabolism and growth.
Avirulent Not capable of producing disease.
Avitaminosis (Hypovitaminosis) A disease caused by deficiency of one
or more vitamins in the diet.
Axilla The region just behind the pectoral fin base.
Bacteremia The presence of living bacteria in the blood with or without
significant response by the host.
Bacterial Gill Disease A disease usually associated with unfavorable
environmental conditions followed by secondary invasion of opportun-
ist bacteria. See Environmental Gill Disease.
Bacterial Hemorrhagic Septicemia A disease caused by many of the
gram-negative rod-shaped bacteria (usually of the genera Aeromonas or
Pseudomonas) that invade all tissues and blood of the fish. Synonyms:
infectious dropsy; red pest; fresh water eel disease; redmouth disease;
motile aeromonad septicemia (MAS).
Bacterial Kidney Disease An acute to chronic disease of salmonids
caused by Renibacterium salmoninarum. Synonyms: corynebacterial kid-
ney disease; Dee's disease; kidney disease.
Bacterin A vaccine prepared from bacteria and inactivated by heat or
chemicals in a manner that does not alter the cell antigens.
GLOSSARY 473
Bacteriocidal Having the ability to kill bacteria.
Bacteriostatic Having the ability to inhibit or retard the growth or
reproduction of bacteria.
Bacterium (plural: bacteria) One of a large, widely distributed group of
typically one-celled microorganisms, often parasitic or pathogenic.
Balanced Diet (feed) A diet that provides adequate nutrients for normal
growth and reproduction.
Bar Marks Vertical color marks on fishes.
Barbel An elongated fleshy projection, usually of the lips.
Basal Metabolic Rate The oxygen consumed by a completely resting
animal per unit weight and time.
Basal Metabolism Minimum energy requirements to maintain vital
body processes.
Bath A solution of therapeutic or prophylactic chemicals in which fish
are immersed. See Dip; Short Bath; Flush; Long Bath; Constant-Flow
Treatment.
Benign Not endangering life or health.
Bioassay Any test in which organisms are used to detect or measure the
presence or effect of a chemical or condition.
Biochemical Oxygen Demand (BOD) The quantity of dissolved oxy-
gen taken up by nonliving organic matter in the water.
Biological Control Control of undesirable animals or plants by means
of predators, parasites, pathogens, or genetic diseases (including sterili-
zation).
Biological Oxidation Oxidation of organic matter by organisms in the
presence of oxygen.
Biotin Vitamin H, one of the B-complex vitamins.
Black Grub Black spots in the skin of fishes caused by metacercaria
(larval stages) of the trematodes Uvilifer ambloplitis, Cryptocotyle lingua,
and others. Synonym: black-spot disease.
Black Spot Usually refers to black cysts of intermediate stages of trema-
todes in fish. See Black Grub.
Black-Spot Disease See Black Grub.
Black-Tail Disease See Whirling Disease.
Blank Egg An unfertilized egg.
Blastopore Channel leading into a cavity in the egg where fertilization
takes place and early cell division begins.
Blastula A hollow ball of cells, one of the early stages in embryological
development.
Blood Flagellates Flagellated protozoan parasites of the blood.
Blue-Sac Disease A disease of sac fry characterized by opalescence and
distension of the yolk sac with fluid and caused by previous partial
asphyxia.
474 FISH HAICHF.RY MANAGEMENT
Blue Slime Excessive mucus accumulation on fish, usually caused by
skin irritiation due to ectoparasites or malnutrition.
Blue-Slime Disease A skin condition associated with a deficiency of
biotin in the diet.
Blue Stone See Copper Sulfatte.
Boil A localized infection of skin and subcutaneous tissue developing
into a solitary abscess that drains externally.
Bouin's Fluid A mixture of 75 parts saturated picric acid, aqueous solu-
tion; 25 parts formalin (40'/(i formaldehyde); and 5 parts glacial acetic
acid. This is widely used for preserving biological material.
Brackish Water A mixture of fresh and sea water; or water with total
salt concentrations between 0.05% and 3.0%.
Branchiae (singular: Branchia) Gills, the respiratory organs of fishes.
Branchiocranium The bony skeleton supporting the gill arches.
Branchiomycosis A fungal infection of the gills caused by Branchiao-
myces sp. Synonyms: gill rot; European gill rot.
Broodstock Adult fish retained for spawning.
Buccal Cavity Mouth cavity.
Buccal Incubation Incubation of eggs in the mouth; oral incubation.
Buffer Chemical that, by taking up or giving up hydrogen ions, sustains
pH within a narrow range.
Calcinosis The deposition of calcium salts in the tissues without detect-
able injury to the affected parts.
Calcium Carbonate A relatively insoluble salt, CaCO^,, the primary
constituent of limestone and a common constituent of hard water.
Calcium Cyanamide (Lime Nitrogen) CaCN;. Used as a pond disinfec-
tant.
Calcium Oxide See Lime.
Calorie The amount of heat required to raise the temperature of one
gram of water one degree centigrade.
Carbohydrate Any of the various neutral compounds of carbon, hydro-
gen, and oxygen, such as sugars, starches, and celluloses, most of
which can be utilized as an energy source by animals.
Carbon Dioxide A colorless, odorless gas, CO7, resulting from the oxi-
dation of carbon-containing substances; highly soluble in water. Toxic
to fish at high levels. Toxicity to fish increases at low levels of oxygen.
May be used as an anesthetic.
Carbonate The C03^ ion, or any salt formed with it (such as calcium
carbonate, CaCO^).
Carcinogen Any agent or substance that produces cancer or accelerates
the development of cancer.
GLOSSARY 475
Carnivorous Feeding or preying on animals.
Carrier An individual harboring a pathogen without indicating signs of
the disease.
Carrier Host (Transport Host) An animal in which the larval stage of a
parasite will live but not develop.
Carrying Capacity The population, number, or weight of a species that
a given environment can support for a given time.
Cartilage A substance more flexible than bone but serving the same
purpose.
Catabolism The metabolic breakdown of materials with a resultant
release of energy.
Catadromous Fish that leave fresh water and migrate to the sea to
spawn.
Catalyst A substance that speeds up the rate of chemical reaction but is
not itself used up in the reaction.
Cataract Partial or complete opacity of the crystalline lens of the eye or
its capsule.
Catfish Virus Disease See Channel Catfish Virus Disease.
Caudal Pertaining to the posterior end.
Caudal Fin The tail fin of fish.
Caudal Peduncle The relatively thin posterior section of the body to
which the caudal fin is attached; region between base of caudal fin
and base of the last ray of the anal fin.
CCVD Channel Catfish Virus Disease.
Cecum (plural: Ceca) A blind sac of the alimentary canal, such as a
pyloric cecum at the posterior end of the stomach.
Channel Catfish Virus Disease (CCVD) A disease caused by a her-
pesvirus that is infectious to channel catfish and blue catfish.
Chemical Coagulation A process in which chemical coagulants are put
into water to form settleable floes from suspended colloidal solids.
Chemical Oxygen Demand (COD) A measure of the chemically oxi-
dizable components in water, determined by the quantity of oxygen
consumed.
Chemotherapy Cure or control of a disease by the use of chemicals
(drugs).
Chinook Salmon Virus Disease See Infectious Hematopoietic Necrosis.
Chromatophores Colored pigment cells.
Chromosomes Structural units of heredity in the nuclei of cells.
Chronic Occurring or recurring over a long time.
Chronic Inflammation Long-lasting inflammation.
Cilia Movable organelles that project from some cells, used for locomo-
tion of one-celled organisms or to create fluid currents past attached
cells.
47r) FISH HATCHERY MANAGF.MF.NT
Ciliate Protozoan One-celled animal bearing motile cilia.
Circuli The more or less concentric growth marks in a fish scale.
Clinical Infection An infection or disease generating obvious symptoms
and signs of pathology.
Cloaca The common cavity into which rectal, urinary, and genital ducts
open. Common opening of intestine and reproductive system of male
nematodes.
Closed-Formula Feed (Proprietary Feed) A diet for which the formula
is known only to the manufacturer.
Coelomic Cavity The body cavity containing the internal organs.
Coelomic Fluid Fluid inside the body cavity.
Coelozoic Living in a cavity, usually of the urinary tract or gall bladder.
Cold Water Disease See Peduncle Disease; Fin Rot Disease.
Coldwater Species Generally, fish that spawn in water temperatures
below 55°F. The main cultured species are trout and salmon. See Cool-
water Species; Warmwater Species.
Colloid A substance so finely divided that it stays in suspension in
water, but does not pass through animal membranes.
Columnaris Disease An infection, usually of the skin and gills, by Flex-
ibacter columnaris, a myxobacterium.
Communicable Disease A disease that naturally is transmitted directly
or indirectly from one individual to another.
Compensation Point That depth at which incident light penetration is
just sufficient for plankton to photosynthetically produce enough oxy-
gen to balance their respiration requirements.
Complete Diet (Complete Feed) See Balanced Diet.
Complicating Disease A disease supervening during the course of an
already existing ailment.
Compressed Applied to fish, flattened from side to side, as in the case
of a sunfish. See Depressed.
Conditioned Response Behavior that is the result of experience or
training.
Congenital Disease A disease that is present at birth; may be infec-
tious, nutritional, genetic, or developmental.
Congestion Unusual accumulation of blood in tissue; may be active
(often called hyperemia) or passive. Passive congestion is the result of
abnormal venus return and is characterized by dark cyanotic blood.
Constant-Flow Treatment Continuous automatic metering of a chemi-
cal to flowing water.
Contamination The presence of material or microorganisms making
something impure or unclean.
Control (Disease) Reduction of mortality or morbidity in a population,
usually by use of drugs.
GLOSSARY 477
Control (Experimental) Similar test specimens subjected to the same
conditions as the experimental specimens except for the treatment
variable under study.
Control Fish A group of animals given essentially identical treatment to
that of the test group, except for the experimental variable.
Coolwater Species Generally, fish that spawn in temperatures between
40° and 60°F. The main cultured coolwater species are northern pike,
muskellunge, walleye, sauger, and yellow perch. See Coldwater Species;
Warmwater Species.
Copper Sulfate (Blue Stone) Blue stone is copper sulfate pentahydrate
(CuS04-5H20). Effective in the prevention and control of external
protozoan parasites, fungal infections, and external bacterial diseases.
Highly toxic to fish.
Cornea Outer covering of the eye.
Corynebacterial Kidney Disease See Bacterial Kidney Disease.
Costiasis An infection of the skin, fins, and gills by flagellated proto-
zoans of the genus Costia.
Cranium The part of the skull enclosing the brain.
Cyanocobalamin (Vitamin Bi^) One of the B-complex vitamins that is
involved with folic acid in blood-cell production in fish. This vitamin
enhances growth in many animals.
Cyst, Host A connective tissue capsule, liquid or semi-solid, produced
around a parasite by the host.
Cyst, of Parasite Origin A noncellular capsule secreted by a parasite.
Cyst, Protozoa A resistant resting or reproductive stage of protozoa.
Cytoplasm The contents of a cell, exclusive of the nucleus.
Daily Temperature Unit (DTU) Equal to one degree Fahrenheit above
freezing (32°F) for a 24- hour period.
Dechlorination Removal of the residual hypochlorite or chloramine
from water to allow its use in fish culture. Charcoal is used frequently
because it removes much of the hypochlorite and fluoride. Charcoal is
inadequate for removing chloramine.
Dee's Disease See Bacterial Kidney Disease.
Deficiency A shortage of a substance necessary for health.
Deficiency Disease A disease resulting from the lack of one or more
essential constituents of the diet.
Denitrification A biochemical reaction in which nitrate (NO3 ) is
reduced to NO2, N2O, and nitrogen gas.
Density Index The relationship of fish size to the water volume of a
rearing unit; calculated by the formula:
Density Index = (weight of fish) -^ (fish length x volume of rearing unit).
478 FISH HATCHERY MANAGEMENT
Dentary Bones The principal or anterior bones of the lower jaw or
mandible. They usually bear teeth.
Depressed Flattened in the vertical direction, as a flounder.
Depth of Fish The greatest vertical dimension; usually measured just in
front of the dorsal fin.
Dermal Pertaining to the skin.
Dermatomycosis Any fungus infection of the skin.
Diarrhea Profuse discharge of fluid feces.
Diet Food regularly provided and consumed.
Dietary Fiber Nondigestible carbohydrate.
Digestion The hydrolysis of foods in the digestive tract to simple sub-
stances that may be absorbed by the body.
Diluent A substance used to dissolve and dilute another substance.
Dilution Water Refers to the water used to dilute toxicants in aquatic
toxicity studies.
Dip Brief immersion of fish into a concentrated solution of a treatment,
usually for one minute or less.
Diplostomiasis An infection involving larvae of any species of the genus
Diplostomum, Trematoda.
Dipterex See Dylox.
Disease Any departure from health; a particular destructive process in
an organ or organism with a specific cause and symptoms.
Disease Agent A physical, chemical, or biological factor that causes
disease. Synonyms: etiologic agent; pathogenic agent.
Disinfectant An agent that destroys infective agents.
Disinfection Destruction of pathogenic microorganisms or their toxins.
Dissolved Oxygen The amount of elemental oxygen, O2, in solution
under existing atmospheric pressure and temperature.
Dissolved Solids The residue of all dissolved materials when water is
evaporated to dryness. See Salinity.
Distal The remote or extreme end of a structure.
Diurnal Relating to daylight; opposite of nocturnal.
Dorsal Pertaining to the back.
Dorsal Fin The fin on the back or dorsal side, in front of the adipose
fin if the latter is present.
Dose A quantity of medication administered at one time.
Drip Treatment See Constant- Flow Treatment.
Dropsy See Edema.
Dry Ration A diet prepared from air-dried ingredients, formed into dis-
tinct particles and fed to fish.
Dylox (Dipterex, Masoten) Organophosphate insecticide effective in the
control of parasitic copepods.
Dysentery Liquid feces containing blood and mucus. Inflammation of
the colon.
GLOSSARY 479
Ectoderm The outer layer of cells in an embryo that gives rise to vari-
ous organs.
Ectoparasite Parasite that lives on the surface of the host.
Edema Excessive accumulation of fluid in tissue spaces.
Efficacy Ability to produce effects or intended results.
Effluent The discharge from a rearing facility, treatment plant, or
industry.
Egg The mature female germ cell, ovum.
Egtved Disease See Viral Hemorrhagic Septicemia.
Emaciation Wasting of the body.
Emarginate Fin Fin with the margin containing a shallow notch, as in
the caudal fin of the rock bass.
Emboli Abnormal materials carried by the blood stream, such as blood
clots, air bubbles, cancers or other tissue cells, fat, clumps of bacteria,
or foreign bodies, until they lodge in a blood vessel and obstruct it.
Embryo Developing organism before it is hatched or born.
Endocrine A ductless gland or the hormone produced therein.
Endoparasite A parasite that lives in the host.
Endoskeleton The skeleton proper; the inner bony and cartilaginous
framework.
Energy Capacity to do work.
Enteric Redmouth Disease (ERM) A disease, primarily of salmonids,
characterized by general bacteremia. Caused by an enteric bacterium,
Yersinia ruckeri. Synonym: Hagerman redmouth disease.
Enteritis Any inflammation of the intestinal tract.
Environment The sum total of the external conditions that affect
growth and development of an organism.
Environmental Gill Disease Hyperplasia of gill tissue caused by pres-
ence of a pollutant in the water that is a gill irritant. See Bacterial Gill
Disease.
Enzootic A disease that is present in an animal population at all times
but occurs in few individuals at any given time.
Enzyme A protein that catalyzes biochemical reactions in living organ-
isms.
Epidermis The outer layer of the skin.
Epizootic A disease attacking many animals in a population at the same
time; widely diffused and rapidly spreading.
Epizootiology The study of epizootics; the field of science dealing with
relationships of various factors that determine the frequencies and dis-
tributions of diseases among animals.
Eradication Removal of all recognizable units of an infecting agent
from the environment.
ERM See Enteric Redmouth Disease.
480 FISH HATCHERY MANAGEMENT
Esophagus The gullet; a muscular, membranous tube between the phar-
ynx and the stomach.
Essential Amino Acids Those amino acids that must be supplied by
the diet and cannot be synthesized within the body.
Essential Fatty Acid A fatty acid that must be supplied by the diet.
Estuary Water mass where fresh water and sea water mix.
Etiologic Agent See Disease Agent.
Etiology The study of the causes of a disease, both direct and predispos-
ing, and the mode of their operation; not synonymous with cause or
pathogenesis of disease, but often used to mean pathogenesis.
European Gill Rot See Branchiomycosis.
Excretion The process of getting rid or throwing off metabolic waste
products by an organism.
Exophthalmos Abnormal protrusion of the eyeball from the orbit.
Exoskeleton The hard parts on the exterior surfaces, such as scales,
scutes, and bony plates.
Extended Aeration System A modification of the activated-sludge pro-
cess in which the retention time is longer than in the conventional
process.
Extensive Culture Rearing of fish in ponds with low water exchange
and at low densities; the fish utilize primarily natural foods.
Eyed Egg The embryo stage at which pigmentation of the eyes becomes
visible through the egg shell.
F| The first generation of a cross.
F7 The second filial generation obtained by random crossing of Fj indi-
viduals.
Fat An ester composed of fatty acid(s) and glycerol.
Fatty Acid Organic acid present in lipids, varying in carbon content
from 2 to 34 atoms (C2-C34).
Fauna The animals inhabiting any region, taken collectively.
Fecundity Number of eggs in a female spawner.
Feeding Level The amount of feed offered to fish over a unit time, usu-
ally given as percent of fish body weight per day.
Fertility Ability to produce viable offspring.
Fertilization (l) The union of sperm and egg; (2) addition of nutrients
to a pond to stimulate natural food production.
Fin Ray One of the cartilaginous rods that support the membranes of
the fin.
Fin Rot Disease A chronic, necrotic disease of the fins caused by inva-
sion of a myxobacterium into the fin tissue of an unhealthy fish.
Fingerling The stage in a fish's life between 1 inch and the length at 1
year of age.
GLOSSARY 481
Fixative A chemical agent chosen to penetrate tissues very soon after
death and preserve the cellular components in an insoluble state as
nearly life-like as possible.
Flagellum (plural: Flagella) Whip-like locomotion organelle of single
(usually free-living) cells.
Flashing Quick turning movements of fish, especially when fish are
annoyed by external parasites, causing a momentary reflection of light
from their sides and bellies. When flashing, fish often scrape them-
selves against objects to rid themselves of the parasites.
Flow Index The relationship of fish size to water inflow (flow rate) of a
rearing unit; calculated by the formula:
Flow Index = (fish weight) ^ (fish length X water inflow).
Flow rate The volume of water moving past a given point in a unit of
time, usually expressed as cubic feet per second (cfs) or gallons per
minute (gpm).
Flush A short bath in which the flow of water is not stopped, but a high
concentration of chemical is added at the inlet and passed through the
system as a pulse.
Folic Acid (Folacin) A vitamin of the B complex that is necessary for
maturation of red blood cells and synthesis of nucleoproteins; defi-
ciency results in anemia.
Fomites Inanimate objects (brushes, or dipnets) that may be contam-
inated with and transmit infectious organisms. See Vector.
Food Conversion A ratio of food intake to body weight gain; more gen-
erally, the total weight of all feed given to a lot of fish divided by the
total weight gain of the fish lot. The units of weight and the time
interval over which they are measured must be the same. The better
the conversion, the lower the ratio.
Fork Length The distance from the tip of the snout to the fork of the
caudal fin.
Formalin Solution of approximately 37% by weight of formaldehyde gas
in water. Effective in the control of external parasites and fungal infec-
tions on fish and eggs. Also used as a tissue fixative.
Formulated Feed A combination of ingredients that provides specific
amounts of nutrients per weight of feed.
Fortification Addition of nutrients to foods.
Free Living Not dependent on a host organism.
Fresh Water Water containing less than 0.05"o total dissolved salts by
weight.
Fry The stage in a fish's life from the time it hatches until it reaches 1
inch in length.
Fungus Any of a group of primitive plants lacking chlorophyll, includ-
ing molds, rusts, mildews, smuts, and mushrooms. Some kinds are
parasitic on fishes.
482 FISH HATCHERY MANAGEMENT
Fungus Disease See Saprolegniasis.
Furuncle A localized infection of skin or subcutaneous tissue which
develops a solitary abscess that may or may not drain externally.
Furunculosis A bacterial disease caused by Aeromonas salmonicida and
characterized by the appearance of furuncles.
Gall Bladder The body vessel containing bile.
Gametes Sexual cells: eggs and sperm.
Gape The opening of the mouth.
Gas Bladder See Air Bladder.
Gas Bubble Disease Gas embolism in various organs and cavities of the
fish, caused by supersaturation of gas (mainly nitrogen) in the blood.
Gastric Relating to the stomach.
Gastritis Inflammation of the stomach.
Gastroenteritis Inflammation of the mucosa of the stomach and intes-
tines.
Gene The unit of inheritance. Genes are located at fixed loci in chromo-
somes and can exist in a series of alternative forms called alleles.
Genetic Dominant Character donated by one parent that masks in the
progeny the recessive character derived from the other parent.
Genetics The science of heredity and variation.
Genital Pertaining to the reproductive organs.
Genus A unit of scientific classification that includes one or several
closely related species. The scientific name for each organism includes
designations for genus and species.
Geographic Distribution The geographic areas in which a condition or
organism is known to occur.
Germinal Disc The disc-like area of an egg yolk on which cell segmen-
tation first appears.
Gill Arch The U-shaped cartilage that supports the gill filaments.
Gill Clefts (Gill Slits) Spaces between the gills connecting the phar-
yngeal cavity with the gill chamber.
Gill Cover The flap- like cover of the gill and gill chamber; the opercu-
lum.
Gill Disease See Bacterial Gill Disease; Environmental Gill Disease.
Gill Filament The slender, delicate, fringe-like structure composing the
gill.
Gill Lamellae The subdivisions of a gill filament where most gas and
some mineral exchanges occur between blood and the outside water.
Gill Openings The external openings of the gill chambers, defined by
the operculum.
Gill Rakers A series of bony appendages, variously arranged along the
anterior and often the posterior edges of the gill arches.
GLOSSARY 483
Gill Rot See Branchiomycosis.
Gills The highly vascular, fleshy filaments used in aquatic respiration
and excretion.
Globulin One of a group of proteins insoluble in water, but soluble in
dilute solutions of neutral salts.
Glycogen Animal starch, a carbohydrate storage product of animals.
Gonadotrophin Hormone produced by pituitary glands to stimulate
sexual maturation.
Gonads The reproductive organs; testes or ovaries.
GPM Gallons per minute.
Grading of Fish Sorting of fish by size, usually by some mechanical
device.
Gram-negative Bacteria Bacteria that lose the purple stain of crystal
violet and retain the counterstain, in the gram staining process.
Gram-positive Bacteria Bacteria that retain the purple stain of crystal
violet in the gram staining process.
Gross Pathology Pathology that deals with the naked-eye appearance
of tissues.
Group Immunity Immunity enjoyed by a susceptible individual by vir-
tue of membership in a population with enough immune individuals to
prevent a disease outbreak.
Gullet The esophagus.
Gyro Infection An infection of any of the monogenetic trematodes or,
more specifically, of Gyrodactylus sp.
Habitat Those plants, animals, and physical components of the environ-
ment that constitute the natural food, physical-chemical conditions,
and cover requirements of an organism.
Hagerman Redmouth Disease See Enteric Redmouth Disease.
Haptor Posterior attachment organ of monogenetic trematodes.
Hardness The power of water to neutralize soap, due to the presence of
cations such as calcium and magnesium; usually expressed as parts per
million equivalents of calcium carbonate. Refers to the calcium and
magnesium ion concentration in water on a scale of very soft (0-20
ppm as CaCOy), soft (20-50 ppm), hard (50-500 ppm) and very hard
(500+ ppm).
Hatchery Constant A single value derived by combining the factors in
the numerator of the feeding rate formula: Percent body weight fed
daily = (3 x food conversion x daily length increase x lOO) ^
length of fish. This value may be used to estimate feeding rates when
water temperature, food conversion, and growth rate remain constant.
Hematocrit Percent of total blood volume that consists of cells; packed
cell volume.
484 FISH HATCHERY MANAGEMENT
Hematoma A tumor-like enlargement in the tissue caused by blood
escaping the vascular system.
Hematopoiesis The formation of blood or blood cells in the living
body. The major hematopoietic tissue in fish is located in the anterior
kidney. Synonym: hemapoiesis.
Hematopoietic Kidney The anterior portion of the kidney ("head kid-
ney") involved in the production of blood cells.
Hemoglobin The respiratory pigment of red blood cells that takes up
oxygen at the gills or lungs and releases it at the tissues.
Hemorrhage An escape of blood from its vessels, through either intact
or ruptured walls.
Hepatic Pertaining to the liver.
Hepatitis Inflammation of the liver.
Hepatoma A tumor with cells resembling those of liver; includes any
tumor of the liver. Hepatoma is associated with mold toxins in feed
eaten by cultured fishes. The toxin having the greatest affect on fishes
is aflatoxin B, , from Aspergillus flavus.
Heterotrophic Bacteria Bacteria that oxidize organic material (car-
bohydrate, protein, fats) to CO2 , NH4 — N, and water for their energy
source.
Histology Microscopic study of cells, tissues, and organs.
Histopathology The study of microscopically visible changes in
diseased tissues.
Homing Return of fish to their stream or lake of origin to spawn.
Hormone A chemical product of living cells affecting organs that do not
secrete it.
HRM See Enteric Redmouth Disease.
Hyamine See Quaternary Ammonium Compounds.
Hybrid Progeny resulting from a cross between parents that are geneti-
cally unlike.
Hybrid Vigor Condition in which the offspring perform better than the
parents. Synonym: heterosis.
Hydrogen Ion Concentration (Activity) The cause of acidity in water.
See pH.
Hydrogen Sulfide An odorous, soluble gas, H^S, resulting from anaero-
bic decomposition of sulfur-containing compounds, especially proteins.
Hyoid Bones Bones in the floor of the mouth supporting the tongue.
Hyper- A prefix denoting excessive, above normal, or situated above.
Hyperemia Increased blood resulting in distension of the blood vessels.
Hypo- A prefix denoting deficiency, lack, below, beneath.
Ich A protozoan disease caused by the ciliate Ichthyophtherius multifilis;
"white-spot disease."
GLOSSARY 485
IHN See Infectious Hematopoietic Necrosis.
Immune Unsusceptible to a disease.
Immunity Lack of susceptibility; resistance. An inherited or acquired
status.
Immunization Process or procedure by which an individual is made
resistant to disease, specifically infectious disease.
Imprinting The imposition of a behavior pattern in a young animal by
exposure to stimuli.
Inbred Line A line produced by continued matings of brothers to sisters
and progeny to parents over several generations.
Incidence The number of new cases of a particular disease occurring
within a specified period in a group of organisms.
Incubation (Disease) Period of time between the exposure of an indivi-
dual to a pathogen and the appearance of the disease it causes.
Incubation (Eggs) Period from fertilization of the egg until it hatches.
Incubator Device for artificial rearing of fertilized fish eggs and newly
hatched fry.
Indispensable Amino Acid See Essential Amino Acids.
Inert Gases Those gases in the atmosphere that are inert or nearly
inert; nitrogen, argon, helium, xenon, krypton, and others. See Gas
Bubble Disease.
Infection Contamination (external or internal) with a disease-causing
organism or material, whether or not overt disease results.
Infection, Focal A well circumscribed or localized infection in or on a
host.
Infection, Secondary Infection of a host that already is infected by a
different pathogen.
Infection, Terminal An infection, often secondary, that leads to death
of the host.
Infectious Catarrhal Enteritis See Infectious Pancreatic Necrosis.
Infectious Disease A disease that can be transmitted between hosts.
Infectious Hematopoietic Necrosis (IHN) A disease caused by infec-
tious hematopoietic viruses of the Rabdovirus group. Synonyms: Chi-
nook salmon virus disease, Oregon sockeye salmon virus, Sacramento
River chinook disease.
Infectious Pancreatic Necrosis (IPN) A disease caused by an
infectious pancreatic necrosis virus that presently has not been placed
into a group. Synonym: infectious catarrhal enteritis.
Inferior Mouth Mouth on the under side of the head, opening down-
ward.
Inflammation The reaction of the tissues to injury; characterized clini-
cally by heat, swelling, redness, and pain.
Ingest To eat or take into the body.
486 FISH HATCHERY MANAGEMENT
Inoculation The introduction of an organism into the tissues of a living
organism or into a culture medium.
Instinct Inherited behavioral response.
Intensive Culture Rearing of fish at densities greater than can be sup-
ported in the natural environment; utilizes high water flow or
exchange rates and requires the feeding of formulated feeds.
Interspinals Bones to which the rays of the fins are attached.
Intestine The lower part of the alimentary tract from the pyloric end of
the stomach to the anus.
Intragravel Water Water occupying interstitial spaces within gravel.
Intramuscular Injection Administration of a substance into the mus-
cles of an animal.
Intraperitoneal Injection Administration of a substance into the peri-
toneal cavity (body cavity).
In Vitro Used in reference to tests or experiments conducted in an artifi-
cial environment, including cell or tissue culture.
In Vivo Used in reference to tests or experiments conducted in or on
intact, living organisms.
Ion Exchange A process of exchanging certain cations or anions in
water for sodium, hydrogen, or hydroxyl (OH ) ions in a resinous
material.
IPN See Infectious Pancreatic Necrosis.
Isotonic No osmotic difference; one solution having the same osmotic
pressure as another.
Isthmus The region just anterior to the breast of a fish where the gill
membranes converge; the fleshy interspace between gill openings.
Kidney One of the pair of glandular organs in the abdominal cavity that
produces urine.
Kidney Disease See Bacterial Kidney Disease.
Kilogram Calorie The amount of heat required to raise the tempera-
ture of one kilogram of water one degree centigrade, also called kilo-
calorie (kcal), or large calorie.
Larva (plural: Larvae) An immature form, which must undergo change
of appearance or pass through a metamorphic stage to reach the adult
state.
Lateral Band A horizontal pigmented band along the sides of a fish.
Lateral Line A series of sensory pores, sensitive to low- frequency vibra-
tions, located laterally along both sides of the body.
LDV See Lymphocystis Disease.
GLOSSARY 487
Length May refer to the total length, fork length, or standard length
(see under each item).
Lesion Any visible alteration in the normal structure of organs, tissues,
or cells.
Leucocyte A white blood corpuscle.
Lime (Calcium Oxide, Quicklime, Burnt Lime) CaO; used as a disinfec-
tant for fish-holding facilities. Produces heat and extreme alkaline
conditions.
Line Breeding Mating individuals so that their descendants will be
kept closely related to an ancestor that is regarded as unusually desir-
able.
Linolenic Acid An 18-carbon fatty acid with two double bonds. Certain
members of the series are essential for health, growth, and survival of
some, if not most, fishes.
Lipid Any of a group of organic compounds consisting of the fats and
other substances of similar properties. They are insoluble in water, but
soluble in fat solvents and alcohol.
Long Bath A type of bath frequently used in ponds. Low concentrations
of chemical are applied and allowed to disperse by natural processes.
Lymphocystis Disease A virus disease of the skin and fins affecting
many freshwater and marine fishes of the world. The disease is caused
by the lymphocystis virus of the Iridovirus group.
Malignant Progressive growth of certain tumors that may spread to dis-
tant sites or invade surrounding tissue and kill the host.
Malnutrition Faulty or inadequate nutrition.
Mandible Lower jaw.
MAS See Motile Aeromonas Septicemia.
Mass Selection Selection of individuals from a general population for
use as parents in the next generation.
Mating System Any of a number of schemes by which individuals are
assorted in pairs leading to sexual reproduction.
Maxilla or Maxillary The hindmost bone of the upper jaw.
Mean The arithmetic average of a series of observations.
Mechanical Damage Extensive connective tisue proliferation, leading
to impaired growth and reproductive processes, caused by parasites
migrating through tissue.
Median A value in a series halfway between the highest and lowest
values.
Melanophore A black pigment cell; large numbers of these give fish a
dark color.
Menadione A fat-soluble vitamin; a form of vitamin K.
488 FISH HATCHERY MANAGEMENT
Meristic Characters Body parts that can be counted (scales, gill rakers,
vertebrae, etc.); useful in species identifications.
Merthiolate, Sodium (Thimerosal) o-Carboxyphenyl-thioethylmercury,
sodium salt; used as an external disinfectant, especially for living fish
eggs.
Metabolic Rate The amount of oxygen used for total metabolism per
unit of time per unit of body weight.
Metabolism Vital processes involved in the release of body energy, the
building and repair of body tissue, and the excretion of waste materi-
als; combination of anabolism and catabolism.
Methylene Blue 3, 7-A/>Dimethylamino-phenazathionium chloride; a
quinoneimine dye effective against external protozoans and superficial
bacterial infections.
Microbe Microorganism, such as a virus, bacterium, fungus, or proto-
zoan.
Micropyle Opening in egg that allows entrance of the sperm.
Migration Movement of fish populations.
Milt Sperm-bearing fluid.
Mitosis The process by which the nucleus is divided into two daughter
nuclei with equivalent chromosome complements.
MJB Coffee can; essential measuring device used by some fish culturists
in lieu of a graduated cylinder.
Monthly Temperature Unit (MTU) Equal to one degree Fahrenheit
above freezing (32° F) based on the average monthly water tempera-
ture (30 days).
Morbid Caused by disease; unhealthy; diseased.
Morbidity The condition of being diseased.
Morbidity Rate The proportion of individuals with a specific disease
during a given time in a population.
Moribund Obviously progressing towards death, nearly dead.
Morphology The science of the form and structure of animals and
plants.
Mortality The ratio of dead to living individuals in a population.
Mortality Rate The number of deaths per unit of population during a
specified period. Synonyms: death rate; crude mortality rate; fatality
rate.
Motile Aeromonas Septicemia (MAS) An acute to chronic infectious
disease caused by any motile bacteria belonging to the genus Aeromo-
nas, primarily Aeromonas hydrophila or Aeromonas punctate (= Aeromonas
liquifaciens) . Synonyms: bacterial hemorrhagic septicemia; pike pest.
Mottled Blotched; color spots running together.
Mouth Fungus See Columnaris Disease.
GLOSSARY 489
Mucking (Egg) The addition of an inert substance such as clay or starch
to adhesive eggs to prevent them from sticking together during spawn
taking. Most commonly used with esocid and walleye eggs.
Mucus A viscid or slimy substance secreted by the mucous glands offish.
Mutation A sudden heritable variation in a gene or in a chromosome
structure.
Mycology The study of fungi.
Mycosis Any disease caused by an infectious fungus.
Myomere An embryonic muscular segment that later becomes a section
of the side muscle of a fish.
Myotome Muscle segment.
Myxobacteriosis A disease caused by any member of the Myxobacteria
group of bacteria. See Peduncle Disease, Cold Water Disease, Fin Rot
Disease, Columnaris Disease.
Nares The openings of the nasal cavity.
Necropsy A medical examination of the body after death to ascertain
the cause of death. Synonym for humans: autopsy.
Necrosis Dying of cells or tissues within the living body.
Nematoda A diverse phylum of roundworms, many of which are plant
or animal parasites.
Nephrocalcinosis A condition of renal insufficiency due to the precipi-
tation of calcium phosphate (CaP04) in the tubules of the kidney.
Observed frequently in fish.
Niacin One of the water-soluble B-complex vitamins, essential for
maintenance of the health of skin and other epithelial tissues in fishes.
Nicotinic Acid See Niacin.
Nitrification A method through which ammonia is biologically oxi-
dized to nitrite and then nitrate.
Nitrite The NO7 ion.
Nitrogen An odorless, gaseous element that makes up 78% of the earth's
atmosphere and is a constituent of all living tissue. It is almost inert in
its gaseous form.
Nitrogenous Wastes Simple nitrogen compounds produced by the
metabolism of proteins, such as urea and uric acid.
Nonpathogenic Refers to an organism that may infect but causes no
disease.
Nostril See Nares.
Nutrient A chemical used for growth and maintenance of an organism.
Nutrition The sum of the processes in which an animal (or plant) takes
in and utilizes food.
Nutritional Gill Disease Gill hyperplasia caused by deficiency of pan-
tothenic acid in the diet.
490 FISH HATCHERY MANAGEMENT
Ocean Ranching Type of aquaculture involving the release of juvenile
aquatic animals into marine waters to grow on natural foods to har-
vestable size.
Open-Formula Feed A diet in which all the ingredients and their pro-
portions are public (nonproprietary).
Operculum A bony flap-like protective gill covering.
Optic Referring to the eye.
Osmoregulation The process by which organisms maintain stable
osmotic pressures in their blood, tissues, and cells in the face of differ-
ing chemical properties among tissues and cells, and between the
organism and the external environments.
Osmosis The diffusion of liquid that takes place through a semiperme-
able membrane between solutions starting at different osmotic pres-
sures, and that tends to equalize those pressures. Water always will
move toward the more concentrated solution, regardless of the sub-
stances dissolved, until the concentration of dissolved particles is
equalized, regardless of electric charge.
Osmotic Pressure The pressure needed to prevent water from flowing
into a more concentrated solution from a less concentrated one across
a semipermeable membrane.
Outfall Wastewater at its point of effluence or its entry into a river or
other body of water.
Ovarian Fluid Fluid surrounding eggs inside the female's body.
Ovaries The female reproductive organs.
Overt Disease A disease, not necessarily infectious, that is apparent or
obvious by gross inspection; a disease exhibiting clinical signs.
Oviduct The tube that carries eggs from the ovary to the exterior.
Oviparous Producing eggs that are fertilized, develop, and hatch out-
side the female body.
Ovoviviparous Producing eggs, usually with much yolk, that are fertil-
ized internally. Little or no nourishment is furnished by the mother
during development; hatching may occur before or after expulsion.
Ovulate Process of producing mature eggs capable of being fertilized.
Ovum (plural: Ova) Egg cell or single egg.
Oxidation Combination with oxygen; removal of electrons to increase
positive charge.
Oxytetracycline (Terramycin) One of the tetracycline antibiotics pro-
duced by Streptomyces rimosus and effective against a wide variety of
bacteria pathogenic to fishes.
Pancreas The organ that functions as both an endocrine gland secreting
insulin and an exocrine gland secreting digestive enzymes.
GLOSSARY 491
Pantothenic Acid One of the essential B-complex vitamins.
Para-aminobenzoic Acid (PABA) A vitamin- like substance thought to
be essential in the diet for maintenance of health of certain fishes. No
requirement determined for fish.
Parasite An organism that lives in or on another organism (the host)
and that depends on the host for its food, has a higher reproductive
potential than the host, and may harm the host when present in large
numbers.
Parasite, Obligate An organism that cannot lead an independent, non-
parasitic existence.
Parasiticide Antiparasite chemical (added to water) or drug (fed or
injected).
Parasitology The study of parasites.
Parr A life stage of salmonid fishes that extends from the time feeding
begins until the fish become sufficiently pigmented to obliterate the
parr marks, usually ending during the first year.
Parr Mark One of the vertical color bars found on young salmonids and
certain other fishes.
Part Per Billion (ppb) A concentration at which one unit is contained
in a total of a billion units. Equivalent to one microgram per kilogram
(l /ug/kg), or nanoliter per liter (l nl/liter).
Part Per Million (ppm) A concentration at which one unit is contained
in a total of a million units. Equivalent to one milligram per kilogram
(l ml/kg) or one microliter per liter (l yul/liter).
Part Per Thousand (ppt or /oo) A concentration at which one unit is
contained in a total of a thousand units. Equivalent to one gram per
kilogram (l g/kg) or one milliliter per liter (l ml/liter). Normally, this
term is used to specify the salinity of estuarine or sea waters.
Pathogen, Opportunistic An organism capable of causing disease only
when the host's resistance is lowered. Compare with Secondary Invader.
Pathology The study of diseases and the structural and functional
changes produced by them.
Pectoral Fins The anterior and ventrally located fins whose principle
function is locomotor maneuvering.
Peduncle Disease A chronic, necrotic disease of the fins, primarily the
caudal fin, caused by invasion of a myxobacterium (commonly Cyto-
phaga psychrophilia) into fin and caudal peduncle tissue of an unhealthy
fish. Synonyms: fin rot disease; cold water disease.
Pelvic Fins Paired fins corresponding to the posterior limbs of the
higher vertebrates (sometimes called ventral fins), located below or
behind the pectoral fins.
Peritoneum The membrane lining the abdominal cavity.
Perivitelline Fluid Fluid lying between the yolk and outer shell
(chorion) of an egg.
492 FISH HATCHERY MANAGEMENT
Perivitelline Space Area between yolk and chorion of an egg where
embryo expansion occurs.
Permanganate, Potassium KMnO,; strong oxidizing agent used as a
disinfectant and to control external parasites.
Petechia A minute rounded spot of hemorrhage on a surface, usually
less than one millimeter in diameter.
pH An expression of the acid- base relationship designated as the loga-
rithm of the reciprocal of the hydrogen-ion activity; the value of 7.0
expresses neutral solutions; values decreasing below 7.0 represent
increasing acidity; those increasing above 7.0 represent increasingly
basic solutions.
Pharynx The cavity between the mouth and esophagus.
Phenotype Appearance of an individual as contrasted with its genetic
makeup or genotype. Also used to designate a group of individuals
with similar appearance but not necessarily identical genotypes.
Photoperiod The number of daylight hours best suited to the growth
and maturation of an organism.
Photosynthesis The formation of carbohydrates from carbon dioxide
and water that takes place in the chlorophyll-containing tissues of
plants exposed to light; oxygen is produced as a by-product.
Phytoplankton Minute plants suspended in water with little or no capa-
bility for controlling their position in the water mass; frequently
referred to as algae.
Pig Trough See Von Bayer Trough.
Pigmentation Disposition of coloring matter in an organ or tissue.
Pituitary Small endocrine organ located near the brain.
Planting of Fish The act of releasing fish from a hatchery into a
specific lake or river. Synonyms: distribution; stocking.
Plasma The fluid fraction of the blood, as distinguished from corpuscles.
Plasma contains dissolved salts and proteins. Compare with Serum.
Poikilothermic Having a body temperature that fluctuates with that of
the environment.
Pollutant A term referring to a wide range of toxic chemicals and
organic materials introduced into waterways from industrial plants and
sewage wastes.
Pollution The addition of any substance not normally found in or
occurring in a material or ecosystem.
Population A coexisting and interbreeding group of individuals of the
same species in a particular locality.
Population Density The number of individuals of one population in a
given area or volume.
Portal of Entry The pathway by which pathogens or parasites enter the
host.
GLOSSARY 493
Portal of Exit The pathway by which pathogens or parasites leave or
are shed by the host.
Posttreatment Treatment of hatchery wastewater before it is discharged
into the receiving water (pollution abatement).
Pox A disease sign in which eruptive lesions are observed primarily on
the skin and mucous membranes.
Pox Disease A common disease of freshwater fishes, primarily minnows,
characterized by small, flat epithelial growths and caused by a virus as
yet unidentified. Synonyms: carp pox; papilloma.
Pretreatment Treatment of water before it enters the hatchery.
Prevention, Disease Steps taken to stop a disease outbreak before it
occurs; may include environmental manipulation, immunization,
administration of drugs, etc.
Progeny Offspring.
Progeny Test A test of the value of an individual based on the perform-
ance of its offspring produced in some definite system of mating.
Prophylactic Activity or agent that prevents the occurrence of disease.
Protein Any of the numerous naturally occurring complex combinations
of amino acids that contain the elements carbon, hydrogen, nitrogen,
oxygen and occasionally sulfur, phosphorus or other elements.
Protozoa The phylum of mostly microscopic animals made up of a sin-
gle cell or a group of more or less identical cells and living chiefly in
water; includes many parasitic forms.
Pseudobranch The remnant of the first gill arch that often does not
have a respiratory function and is thought to be involved in hormone
activation or secretion.
Pseudomonas Septicemia A hemorrhagic, septicemic disease of fishes
caused by infection of a member of the genus Pseudomonas. This is a
stress- mediated disease that usually occurs as a generalized septicemia.
See Bacterial Hemorrhagic Septicemia.
Pyloric Cecum See Cecum.
Pyridoxine (Vitamin B,,) One of the B-complex vitamins involved in fat
metabolism, but playing a more important role in protein metabo-
lism. As a result, carnivorous fish have stringent requirements for this
vitamin.
Quaternary Ammonium Compounds Several of the cationic surface-
active agents and germicides, each with a quaternary ammonium
structure. They are bactericidal but will not kill external parasites of
fish. Generally, they are used for controlling external bacterial patho-
gens and disinfecting hatching equipment.
Radii of Scale Lines on the proximal part of a scale, radiating from
near center to the edge.
494 FISH HATCHERY MANAGEMENT
Random Mating Matings without consideration of definable charac-
teristics of the broodfish; nonselective mating.
Ration A fixed allowance of food for a day or other unit of time.
Ray A supporting rod for a fin. There are two kinds: hard (spines) and
soft rays.
Rearing Unit Any facility in which fish are held during the rearing
process, such as rectangular raceways, circular ponds, circulation race-
ways, and earth ponds.
Recessive Character possessed by one parent that is masked in the
progeny by the corresponding alternative or dominant character
derived from the other parent.
Reciprocal Mating (Crosses) Paired crosses in which both males and
females of one parental line are mated with the other parental line.
Reconditioning Treatment Treatment of water to allow its reuse for
fish rearing.
Rectum Most distal part of the intestine; repository for the feces.
Red Pest See Motile Aeromonas Disease.
Red Sore Disease See Vibriosis.
Redd Area of stream or lake bottom excavated by a female salmonid
during spawning.
Redmouth Disease An original name for bacterial hemorrhagic septicemia
caused by an infection of Aeromonas hydrophila specifically. Synonyms:
motile aeromonas disease; bacterial hemorrhagic septicemia.
Residue, Tissue Quantity of a drug or other chemical remaining in
body tissues after treatment or exposure is stopped.
Resistance The natural ability of an organism to withstand the effects
of various physical, chemical, and biological agents that potentially are
harmful to the organism.
Resistant, Drug Said of a microorganism, usually a bacterium, that can-
not be controlled (inhibited) or killed by a drug.
Reuse, Recycle The use of water more than one time for fish propaga-
tion. There may or may not be water treatment between uses and dif-
ferent rearing units may be involved.
Riboflavin An essential vitamin of the B-complex group (B2).
Roccal See Quaternary Ammonium Compounds.
Roe The eggs of fishes.
Roundworm See Nematoda.
Sac Fry A fish with an external yolk sac.
Safe Concentration The maximum concentration of a material that
produces no adverse sublethal or chronic effect.
Salinity Concentration of sodium, potassium, magnesium, calcium,
GLOSSARY 495
bicarbonate, carbonate, sulfate, and halides (chloride, fluoride,
bromide) in water. See Dissolved Solids.
Sample A part, piece, item, or observation taken or shown as representa-
tive of a total population.
Sample Count A method of estimating fish population weight from
individual weights of a small portion of the population.
Sanitizer A chemical that reduces microbial contamination on equip-
ment.
Saprolegniasis An infection by fungi of the genus Saprolegnia, usually
on the external surfaces of a fish body or on dead or dying fish eggs.
Saturation In solutions, the maximum amount of a substance that can
be dissolved in a liquid without it being precipitated or released into
the air.
Scale Formula A conventional formula used in identifying fishes.
"Scales 7 + 65 + 12," for example, indicates 7 scales above the lateral
line, 6.5 along the lateral line, and 12 below it.
Scales Above the Lateral Line Usually, the number of scales counted
along an oblique row beginning with the first scale above the lateral
line and running anteriorly to the base of the dorsal fin.
Scales Below the Lateral Line The number of scales counted along a
row beginning at the origin of the anal fin and running obliquely dor-
sally either forward or backward, to the lateral line. For certain species
this count is made from the base of the pelvic fin.
Sea Water Water containing from 3.0 to 3.5"o total salts.
Secchi Disk A circular metal plate with the upper surface divided into
four quadrants, two painted white and two painted black. It is lowered
into the water on a graduated line, and the depth at which it disap-
pears is noted as the limit of visibility.
Second Dorsal Fin The posterior of two dorsal fins, usually the soft-
rayed dorsal fin of spiny-rayed fishes.
Secondary Invader An opportunist pathogen that obtains entrance to a
host following breakdown of the first line of defense.
Sediment Settleable solids that form bottom deposits.
Sedimentation Pond (Settling Basin) A wastewater treatment facility in
which settleable solids are removed from the hatchery effluent.
Selective Breeding Selection of mates in a breeding program to pro-
duce offspring possessing certain defined characteristics.
Sensitive, Drug Said of a microorganism, usually a bacterium, that can
be controlled (inhibited) or killed by use of a drug. See Resistant,
Drug.
Septicemia A clinical sign characterized by a severe bacteremic infec-
tion, generally involving the significant invasion of the blood stream
by microorganisms.
496 FISH HATCHERY MANAGEMENT
Serum The fluid portion of blood that remains after the blood is allowed
to clot and the cells are removed.
Settleable Solids That fraction of the suspended solids that will settle
out of suspension under quiescent conditions.
Shocking (Eggs) Act of mechanically agitating eggs, which ruptures the
perivitelline membranes and turns infertile eggs white.
Short Bath A type of bath most useful in facilities having a controllable
rapid exchange of water. The water flow is stopped, and a relatively
high concentration of chemical is thoroughly mixed in and retained
for about 1 hour.
Side Effect An effect of a chemical or treatment other than that
intended.
Sign Any manifestation of disease, such as an aberration in structure,
physiology, or behavior, as interpreted by an observer. Note the term
"symptom" is only appropriate for human medicine because it
includes the patient's feelings (sensations) about the disease.
Silt Soil particles carried or deposited by moving water.
Single-pass System A system in which water is passed through fish
rearing units without being recycled and then discharged from the
hatchery.
Sludge The mixture of solids and water that is drawn off a settling
chamber.
Smolt Juvenile salmonid at the time of physiological adaptation to life
in the marine environment.
Snout The portion of the head in front of the eyes. The snout is meas-
ured from its most anterior tip to the anterior margin of the eye
socket.
Soft-egg Disease Pathological softening of fish eggs during incubation,
the etiological agent(s) being unknown but possibly a bacterium.
Soft Fins Fins with soft rays only, designated as soft dorsal, etc.
Soft Rays Fin rays that are cross-striated or articulated, like a bamboo
fishing pole.
Solubility The degree to which a substance can be dissolved in a liquid;
usually expressed as milligrams per liter or percent.
Spawning (Hatchery context) Act of obtaining eggs from female fish
and sperm from male fish.
Species The largest group of similar individuals that actually or poten-
tially can successfully interbreed with one another but not with other
such groups; a systematic unit including geographic races and
varieties, and included in a genus.
Specific Drug A drug that has therapeutic effect on one disease but not
on others.
Spent Spawned out.
GLOSSARY 497
Spermatozoon A male reproductive cell, consisting usually of head,
middle piece, and locomotory flagellum.
Spinal Cord The cylindrical structure within the spinal canal, a part of
the central nervous system.
Spines Unsegmented rays, commonly hard and pointed.
Spiny Rays Stiff or noncross-striated fin rays.
Spleen The site of red blood cell, thrombocyte, lymphocyte, and granu-
locyte production.
Sporadic Disease A disease that occurs only occasionally and usually as
a single case.
Stabilization Pond A simple waste-water treatment facility in which
organic matter is oxidized and stabilized (converted to inert residue).
Standard Length The distance from the most anterior portion of the
body to the junction of the caudal peduncle and anal fin.
Standard Metabolic Rate The metabolic rate of poikilothermic animals
under conditions of minimum activity, measured per unit time and
body weight at a particular temperature. Close to basal metabolic rate,
but animals rarely are at complete rest. See Basal Metabolism.
Sterilant An agent that kills all microorganisms.
Sterilize To destroy all microorganisms and their spores in or about an
object.
Stock Group of fish that share a common environment and gene pool.
Stomach The expansion of the alimentary tract between the esophagous
and the pyloric valve.
Strains Group of fish with presumed common ancestry.
Stress A state manifested by a syndrome or bodily change caused by some
force, condition, or circumstance (i.e., by a stressor) in or on an organism
or on one of its physiological or anatomical systems. Any condition that
forces an organism to expend more energy to maintain stability.
Stressor Any stimulus, or succession of stimuli, that tends to disrupt the
normal stability of an animal.
Subacute Not lethal; between acute and chronic.
Sulfadimethoxine Sulfonamide drug effective against certain bacterial
pathogens of fishes.
Sulfaguanidine Sulfonamide drug used in combination with sulfamera-
zine to control certain bacterial pathogens of fishes.
Sulfamerazine Sulfonamide drug effective against certain bacterial
pathogens of fish.
Sulfamethazine (Sulmet) Sulfonamide drug effective against certain
bacterial pathogens of fishes.
Sulfate Any salt of sulfuric acid; any salt containing the radical SOf.
Sulfisoxasole (Gantrisin) Sulfonamide drug effective against certain
bacterial pathogens of fishes.
498 FISH HATCHERY MANAGEMENT
Sulfomerthiolate (Thimerfonate Sodium) Used as an external disinfec-
tant of living fish eggs.
Sulfonamides Antimicrobial compounds having the general formula
H^NSO^ and acting via competition with /)-aminobenzoic acid in folic
acid metabolism (for example, sulfamerazine, sulfamethazine).
Superior As applied to the mouth, opening in an upward direction.
Supersaturation Greater- than- normal solubility of a chemical as a
result of unusual temperatures or pressures.
Supplemental Diet A diet used to augment available natural foods.
Generally used in extensive fish culture.
Susceptible Having little resistance to disease or to injurious agents.
Suspended Solids Particles retained in suspension in the water column.
Swim Bladder See Air Bladder.
Swim-up Term used to describe fry when they begin active swimming
in search of food.
Syndrome A group of signs that together characterize a disease.
Temperature Shock Physiological stress induced by sudden or rapid
changes in temperature, defined by some as any change greater than 3
degrees per hour.
Tender Stage Period of early development, from a few hours after fertil-
ization to the time pigmentation of the eyes becomes evident, during
which the embryo is highly sensitive to shock. Also called green-egg
stage, sensitive stage.
Terramycin See Oxytetracycline.
Testes The male reproductive organs.
Therapeutic Serving to heal or cure.
Thiamine An essential B-complex vitamin that maintains normal car-
bohydrate metabolism and is essential for certain other metabolic
processes.
Thiosulfate, Sodium (Sodium Hyposulfite, Hypo, Antichlor) Na2S203;
used to remove chlorine from solution or as a titrant for determination
of dissolved oxygen by the Winkler method.
Titration A method of determining the strength (concentration) of a
solution by adding known amounts of a reacting chemical until a color
change is detected.
Tocopherol Vitamin E; an essential vitamin that acts as a biological
antioxidant.
Topical Local application of concentrated treatment directly onto a
lesion.
Total Dissolved Solids (TDS) See Dissolved Solids.
Total Length The distance from the most anterior point to the most
posterior tip of the fish tail.
GLOSSARY 499
Total Solids All of the solids in the water, including dissolved,
suspended, and settleable components.
Toxicity A relative measure of the ability of a chemical to be toxic.
Usually refers to the ability of a substance to kill or cause an adverse
effect. High toxicity means that small amounts are capable of causing
death or ill health.
Toxicology The study of the interactions between organisms and a toxi-
cant.
Toxin A particular class of poisons, usually albuminous proteins of high
molecular weight produced by animals or plants, to which the body
may respond by the production of antitoxins.
Transmission The transfer of a disease agent from one individual to
another.
Transmission, Horizontal Any transfer of a disease agent between indi-
viduals except for the special case of parent-to-progeny transfer via
reproductive processes.
Transmission, Vertical The parent- to- progeny transfer of disease
agents via eggs or sperm.
Trauma An injury caused by a mechanical or physical agent.
Trematoda The flukes. Subclass Monogenea: ectoparasitic in general,
one host; subclass Digenea: endoparasitic in general, two hosts or
more.
Tumor An abnormal mass of tissue, the growth of which exceeds and is
uncoordinated with that of the tissues and persists in the same exces-
sive manner after the disappearance of the stimuli that evoked the
change.
Turbidity Presence of suspended or colloidal matter or planktonic
organisms that reduces light penetration of water.
Turbulence Agitation of liquids by currents, jetting actions, winds, or
stirring forces.
Ubiquitous Existing everywhere at the same time.
UDN See Ulcerative Dermal Necrosis.
Ulcer A break in the skin or mucous membrane with loss of surface tis-
sue; disintegration and necrosis of epithelial tissue.
Ulcer Disease An infectious disease of eastern brook trout caused by
the bacterium Hemophilus piscium.
Ulcerative Dermal Necrosis (UDN) A disease of unknown etiology
occurring in older fishes, usually during spawning, and primarily
involving salmonids.
United States Pharmacopeia (USP) An authoritative treatise on
drugs, products used in medicine, formulas for mixtures, and chemical
tests used for identity and purity of the above.
500 FISH HATCHERY MANAGEMENT
Urea One of the compounds in which nitrogen is excreted from fish in
the urine. Most nitrogen is eliminated as ammonia through the gills.
Uremia The condition caused by faulty renal function and resulting in
excessive nitrogenous compounds in the blood.
Urinary Bladder The bladder attached caudally to the kidneys; the
kidneys drain into it.
Urogenital Pore External outlet for the urinary and genital ducts.
Vaccine A preparation of nonvirulent disease organisms (dead or alive)
that retains the capacity to stimulate production of antibodies against
it. See Antigen.
Vector A living organism that carries an infectious agent from an
infected individual to another, directly or indirectly.
Vein A tubular vessel that carries blood to the heart.
Vent The external posterior opening of the alimentary canal; the anus.
Ventral Fins Pelvic fins.
VHS See Viral Hemorrhagic Septicemia.
Viable Alive.
Vibriosis An infectious disease caused by the bacterium Vibrio anguil-
larium. Synonyms: pike pest; eel pest; red sore.
Viral Hemorrhagic Septicemia (VHS) A severe disease of trout
caused by a virus of the Rhabdovirus group. Synonyms: egtved
disease; infectious kidney swelling and liver degeneration (INUL);
trout pest.
Viremia The presence of virus in the blood stream.
Virulence The relative capacity of a pathogen to produce disease.
Vitamin An organic compound occurring in minute amounts in foods
and essential for numerous metabolic reactions.
Vitamin D A radiated form of ergosterol that has not been proved
essential for fish.
Vitamin K An essential, fat-soluble vitamin necessary for formation of
prothrombin; deficiency causes reduced blood clotting.
Vitamin Premix A mixture of crystaline vitamins or concentrates used
to fortify a formulated feed.
Viviparous Bringing forth living young; the mother contributes food
toward the development of the embryos.
Vomer Bone of the anterior part of the roof of the mouth, commonly tri-
angular and often with teeth.
Von Bayer Trough A 12-inch V-shaped trough used to count eggs.
Warmwater Species Generally, fish that spawn at temperatures above
60°F. The chief cultured warmwater species are basses, sunfish, cat-
fish, and minnows. See Coldwater Species; Coolwater Species.
GLOSSARY 501
Water Hardening Process by which an egg absorbs water that accumu-
lates in the perivitelline space.
Water Quality As it relates to fish nutrition, involves dissolved mineral
needs of fishes inhabiting that water (ionic strength).
Water Treatment Primary: removal of a substantial amount of
suspended matter, but little or no removal of colloidal and dissolved
matter. Secondary: biological treatment methods (for example, by
contact stabilization, extended aeration). Tertiary (advanced):
removal of chemicals and dissolved solids.
Weir A structure for measuring water flow.
Western Gill Disease See Nutritional Gill Disease.
Whirling Disease A disease of trout caused by the sporozoan protozoan
Myxosoma cere bra lis.
White Grub An infestation by the metacercarcial stage of Neodiplos-
tomum multicellulata in the liver of many freshwater fishes.
White Spot Disease A noninfectious malady of incubating eggs or on
the yolk sac of alevins. The cause of the disease is thought to be
mechanical damage. Also see Ich.
Yellow Grub An infestation by the metacercarial stage of Clinostomum
marginatum.
Yolk The food part of an egg.
Zooplankton Minute animals in water, chiefly rotifers and crustaceans,
that depend upon water movement to carry them about, having only
weak capabilities for movement. They are important prey for young
fish.
Zoospores Motile spores of fungi.
Zygote Cell formed by the union of two gametes, and the individual
developing from this cell.
Index
The Table of Contents for this book also is intended
as a functional index.
Acidity (pH)
natural waters 11, 15
rearing ponds 110-112
Antimycin A, fish control 93
Ammonia
estimation, hatchery water 24-25
ionization tables 378-382
pond effluent 27
production per pound feed 26
removal: chlorine oxidation 23; ion exchange 22; biological
nitrification 21-22
toxicity 20-21
upper limit for fish 14
Bass, largemouth
broodstock: acquisition 132; maturation 136
carrying capacity, ponds 75-76
diseases: bacterial gill disease 301; European gill rot 314—315;
motile aeromonas septicemia (MAS) 309
eggs: disinfection 189; temperature units 191
503
504 FISH HATCHERY MANAGEMENT
Bass, largemouth [continued]
feeding: guides 253-254; habits 136-137
rearing-pond management 102, 137, 151
spawning 136-137, 151, 152, 192; hormone-induced 173
temperature requirements 136-137, 171
transportation: small containers 366; tank carrying capacity
363
treatment, formalin 276
use of forage fish 136
Bass, smallmouth
anesthetics 359
broodstock acquisition 132
disease, European gill rot 314
eggs, temperature units 191
feeding guides 253-254
spawning 136, 152-154
temperature requirements 136-137
Bass, striped
broodstock acquisition 132
carrying capacity, ponds 77
disease, European gill rot 314
eggs: development 160-164; incubation 196; sampling
159-160; temperature units 191
feeding guide 254
grading 83
oxygen requirements 8
rearing-pond management 102
spawning 134-135, 156, 159, 164—165; hormone-induced 173
temperature requirements 134-135
transportation: carrying capacity 363; stress 358—359
treatment, formalin 276
tolerance, pH 1 1
Biological design criteria 51-55
Biological Oxygen Demand (BOD), production per pound feed 27
Bluegill
broodstock acquisition 138
carrying capacity, ponds 76
culture 154
diet 138
disease, bacterial gill disease 301
eggs, temperature units 191
rearing-pond management 102, 138
INDEX 505
Bluegill {continued)
spawning 136; natural 151
temperature requirements 136
transportation: small containers 366; tanks 363
treatment, formalin 276
used as forage fish 140
Box filter 93
Branding 148
Cage culture 48-49
Calcium
fertilizer 100-101
hatchery water 15
Carbon dioxide
hatchery water 15
plant growth 97
pond acidity 110-112
tolerated, fish 9-10
Carp, common
diseases: European gill rot 314; furunculosis 306; hemorrhagic
septicemia 266; Lernaea 334; spring viremia 267
source, pituitary hormone 172
spawning 136; hormone-induced 173
stress, disease 267
temperature requirements 136
Carrying capacity 63-78
Catfish, blue
broodstock selection 148
disease, channel catfish virus disease 298
tolerance, salinity 14
Catfish, channel
broodstock selection 148
capture 132
carrying capacity: pond 138 (broodstock), 76-77 (fingerlings);
raceways 77
diet 138
diseases: Ambiphrya [Scyphidia) 323; bacterial gill disease 301;
channel catfish virus disease 267, 298; Cleidodiscus 330;
Epistylis 319-320; fungus disease (eggs) 314; furunculosis
306; Henneguya 325; Ich 316; Ichtyobodo [Costia) 316; motile
aeromonas septicemia (MAS) 309; Trichophrya 323
F)0(] FISH HATCHERY MANAGEMENT
Catfish, channel [continued]
eggs: handling L')4-155; hatching jars 196; incubation trough
195; temperature units 191
feeds and feeding: conversion '2'26, Til \ energy availability
22^- Til \ fish flavor 224; floating and sinking 23,5; formu-
lated 217, 400; frequency 257; guide 249-252; initial 256;
sizes 259
grading 84
growth, temperature- related 211
light control 171
nutrition: carbohydrates 218-220; diseases 390-393; lipids
224; proteins 217; vitamins 227-228
selective breeding 147
sex determination 138
spawning 134-135; hormone-induced 173; pens and recepta-
cles 155
stress 267
temperature: control 171; requirements 134—135; Standard
Environmental Temperature (SET) 211
tolerance: ammonia 21; nitrite 22; pH 11; salinity 14; tem-
perature 134-137; total dissolved solids 12
toxicity: ammonia 21; nitrite 22; toxaphene, feeds 233
transportation 362-363; small containers 367
treatments: copper sulfate 277; formalin 276; nitrofurans 281;
potassium permanganate 278; salt 275; Terramycin 280
Catfish, flathead
spawning 134-135
temperature requirements 134—135
Catfish, white, broodstock selection 148
Char, Arctic, spawning channels 150
Chemical Oxygen Demand (COD), pond effluent 27
Chemicals {see Drugs and chemicals)
Chlorine
ammonia removal, hatchery water 23
decontamination: equipment 283; hatchery 284
fish control 93
neutralization 283
pond disinfection 90
toxicity 14, 283
Circular rearing units 40-43
Clinoptilolite, ion-exchange ammonia removal 22
Condition factor, calculation 61
INDEX 507
Crayfish, problem in ponds 114
Density Index 71-74
Diseases
bacterial: columnaris 302-303; enteric redmouth (ERM)
306-308; fin rot 304; furunculosis 304-306; bacterial kid-
ney disease 312-313; motile aeromonas septicemia (MAS)
307-310; peduncle disease 303-304; vibriosis 310-311
certification 293
control 263- 265
environmental: blue sac 268; coagulated yolk (white-spot)
268; gas bubble disease 9
fungal 314-315
immunization 286-288
inspections 292-293
leaflets 342-344
nutritional 390-393
parasitic: Ambiphrya [Scyphidia) 321, 323; Argulus 334; Cerato-
myxa 326-327; Chilodonella 319; Cleidodiscus 330, 332; Dac-
tylogyrus 330; Epistylis 319-322; Gyrodactylus 330-331; Hen-
neguya 324-326; Hexamita 323-324; Ichtyobodo [Costia]
315-316; Ichthyophthirius 316-319; Lernaea 334; Pleistophora
328-329; Sanguinicola 332-333; Trichodina 320-321; Tricho-
phrya 322-323
recognition 264—265
regulations 289-292
resistance 286-287
treatment 266-270; constant-flow 272, 403; drug coating, pel-
lets 405; feeding, injection 273; flush 272; prolonged bath
271, 402-403
vaccination 288-289
viral: channel catfish virus disease (CCV) 267, 298; her-
pesvirus disease of salmonids 298-299; infectious hemato-
poietic necrosis (IHN) 267, 296-297; infectious pancreatic
necrosis (IPN) 294; lymphocystis disease 299-300; viral
hemorrhagic septicemia (VHS) 295-296
Dissolved gas criteria 10
Drugs and chemicals
dosages and characteristics: acriflavin 281-282; calcium
hydroxide 282; copper sulfate 276-277; de-«-butyl tin
oxide 282; formalin 275-276; iodophores 282; Masoten
282-283; nitrofurans 280-281; potassium permanganate
277-278; quaternary ammonium compounds 278-279; salt
275; sulfonamides 281; Terramycin 279-280
508 FISH HATCHKRV MANAGEMENT
Drugs and chemicals [continued)
registration 274-27.5
storage 274
Earthen ponds 47-48
Eel, American, infected with Ich 317
Eggs (2see also individual species)
disinfection 189, 275, 282, 285, 314
transportation (shipping) 193
English- metric conversions 375-377
Feeds and feeding [see also individual species)
application practices 238-239
calculations 242-255
conversion 239, 242
Daphnia, food source 248
frequency 255-257
guides: coolwater fishes 248-249; salmonids 239-248; warm-
water fishes 249-254
fish meal 215
formulated: antioxidants 232; closed 236; deficiencies 264,
390-400; specifications 390-400; dust, particles 234, 236,
238; energy levels 225-227; fat-soluble vitamins 227; fiber
content 231, 232, 236; floating 235, 251; mineral levels
229-231; moisture 234, 235, 238; open 235-236; pigmenta-
tion 232, 235; protein levels 215-217, 236; sinking 234;
trace minerals 231; vitamin levels 227-229, 232; water-
soluble vitamins 227
habits, broodfish 132-134
handling 236-238
hatchery constant 245
manufacturing: lipid rancidity 221, 222, 238; lipid toxicity
222; organic toxicants 233, 390-400; pesticide contamina-
tion 221; spray coating 235, 405; temperature 234, 235
natural foods 233
packaging 236
performance 238
storage 235-238
Fertilizers
combinations 101-102
composition 97
pond application 96
INDEX 509
Flow Index 67-71
Forage fish
goldfish 142-143
herring 140
minnow, fathead 141-142
shad 140
shiner, golden 143-144
sucker, white 140-141
tilapia 140, 144
Goldfish
diseases: Ambiphrya [Scyphidia] 323; Chilodonella 319; furuncu-
losis 306; Lernaea 334; motile aeromonas septicemia (MAS)
308
rearing- pond management 102
spawning 136; hormone-induced 172
temperature requirements 136
tolerance, nitrogen gas 9
used as forage fish 140, 142-143
Growth projections 62—63
Hatchery design standards 34-39
Heavy-metal toxicity: cadmium, copper, lead, mercury, zinc 13, 14
Hyamine, pond disinfection 90
Hybrid vigor 148
Hybridization (cross breeding) 144, 148-149
Hydrogen cyanide 10
Hydrogen sulfide
hatchery water 15
rearing ponds 1 12
toxicity 10, 14
Interspecific hybrids 148—149
Inventory methods 78—83
Iron, hatchery water 15
Lamprey, sea, furunculosis 306
Length- weight relationships 60-61; tables 406-467
Lime, pond disinfection 89-90
510 IISH IIAICHKRY MANACJKMEN'r
Magnesium, hatchery water 15
Manganese, hatchery water 15
Metric- English conversions 375-376
Minerals, water enrichment 13
Muskellunge
broodstock acquisition 132
eggs, temperature units 191, 192
feeds and feeding: formulated 248-249, 399, 400; guides
248-249; initial 256
forage fish for 140
hybridization 148
nutrition: diseases 390-393; protein requirements 217
spawning 134-135, 157
transportation, carrying capacity 364
Muskie, tiger {see also Pike, northern; muskellunge), hatchery
constant 249
Nets, seines
broodfish capture 132
inventory 82-83
Nitrate
hatchery water 15
fertilizer 98
pond effluent 27
production per pound feed 26
Nitrite, toxicity 14, 22
Osmoregulation 213
Oxygen
hatchery water 6-8, 15
ponds 108-110
saturation nomogram 5
Ozone
sterilant 18-19
toxicity 14
Pen rearing 50
pH [see acidity)
Phosphorus, phosphate
hatchery water 15
fertilizer 98-100
pond effluent 27
production per pound feed 26
Pickerel, chain, protein requirements 217
INDEX 511
Pike, northern
broodstock acquisition 132
carrying capacity, ponds 11-1%
diseases: European gill rot 314; furunculosis 306
eggs 159; temperature units 191
feeds and feeding: formulated 248, 399, 400; frequency 256;
guide 248-249
forage fish for 140
grading 83
hybridization 148
nutrition: diseases 390-393; protein requirements 217
spawning 134—135, 156-159
sperm storage 168
transportation: small containers 367; tank carrying capacity
364
temperature requirements 134-135
Polychlorinated biphenyls (PCB's), toxicity 14
Potassium, fertilizer 100
Rearing facilities
characteristics 52-53
selection 50
Record keeping
factors considered 114-115
hatchery codes 387-388
lot history production charts 117-122
ponds 126
production summaries 122-126
rectangular rearing units
circulation ponds 46-47
tanks, raceways 43-46
Roccal, pond disinfection 90
Rotational line-crossing 145-147
Rotenone, fish control 93
Salinity 13-14
Salmon
anesthetics 170, 359-360
broodstock acquisition 132
diseases: bacterial gill disease 300; bacterial kidney disease
312-313; Ceratomyxa shasta 326; Chilodonella 319; colum-
naris disease 302; enteric redmouth (ERM) 307; fungus
314; furunculosis 304-306; Gyrodactylis 330, Henneguya 325;
512 KISH HATCHERY MANAGEM KNI'
Salmon [continued]
herpesvirus disease 29H-299; Hexamita salominis 323; Ith
316; Ichtyobodo [Costia] 316; infectious hematopoietic
necrosis (IHN) 296-297; infectious pancreatic necrosis
(IPN) 294; Myxosoma cerebralis 327; peduncle disease
303-304; Trichodina 320; vibriosis 311; viral hemorrhagic
septicemia (VHS) 296
eggs: disinfection 189, 282; incubation 193-200; storage 193;
temperature units 191
feeds and feeding: energy availability 226; formulated 209,
235, 396-397, 400; frequency 255-257; guides 239-248;
sizes 258; spawning activity 133; storage 236-238
handling, loading 85, 358-359
nutrition: carbohydrates 218-219; diseases 390-393; lipids
222-223; proteins 215 (fry), 216 (yearlings); vitamins
227-228
spawning 165-167
sperm storage 193
stress, disease 265-268
temperature: requirements 134-135; Standard Environmental
Temperature (SET) 211
transportation: methods [see Chapter 6); tank carrying capa-
city 361
treatments: acriflavin 281; copper sulfate 276-277; formalin
275-276; nitrofurans 280-281; quaternary ammonium com-
pounds 278-279; salt 275; sulfonamides 281; Terramycin
279-280
Salmon, Atlantic [see also Salmon)
broodstock acquisition 132
diseases: bacterial kidney disease 312; Ceratomyxa shasta 326;
enteric redmouth (ERM) 307; herpesvirus disease 299;
vibriosis 311; viral hemorrhagic septicemia (VHS) 296
egg development 191
spawning 134-135, 165
temperature requirements 134-135
Salmon, chinook [see also Salmon)
diseases: bacterial kidney disease 312; Ceratomyxa shasta 326;
enteric redmouth (ERM) 307; Henneguya 325; infectious
hematopoietic necrosis (IHN) 296
egg development 191
feeding frequency 257
gamete storage 169
nutrition, protein requirements 216
spawning 134-135; channels 150
temperature requirements 134-135
INDEX 513
Salmon, chum {see also Salmon), carbon dioxide tolerance 9
Salmon, coho {see also Salmon)
carbon dioxide tolerance 10
eggs, temperature units 191
feeding guide 242
nutrition, folic acid deficiency 223
oxygen requirements 7-8
spawning 134-135; channels 150
temperature requirements 134—135
Salmon, sockeye {see also Salmon)
diseases: bacterial kidney disease 312; Ceratomyxa shasta 326;
herpesvirus disease 298; infectious hematopoietic necrosis
(IHN) 296
eggs: sensitivity, artificial light 171; temperature units 191
spavining 134-135, 150; photoperiod control 170
sperm storage 169
temperature requirements 134—135
Saltwater fish
flesh flavor 233
protein utilization 214
vitamin requirements 229
Sanger, broodstock acquisition 132
Screens, perforated aluminum 91
Sea (ocean) ranching 50
Sedimentation basins 27-30
Selective breeding 144, 145
Settleable solids
pond effluent 27
production per pound feed 27
Shad, American
spawning 136
temperature requirements 136
Shiner, golden
anesthetics, transportation 359
disease, Pleistophora ovariae 328
spawning 136
temperature requirements 136
used as forage 140, 143-144
Shrimp, tadpole, pond nuisance 113-114
Sock filter 93
Solid waste disposal 30-31
Spawning {see also individual species)
air-spawning 165-166
aquarium 156
hand stripping 156—159
514 FISH HATCHERY MANAGEMENT
Spawning {continued)
natural 149-155
open pond 154
pen 154
species summaries 134-137
Specimen, disease diagnosis
collection, shipping 335-342
preservation 341-342
Standard disease diagnostic procedures 292
Standard Environmental Temperatures (SET) 211
State abbreviations 389
Steelhead {see also Trout)
broodstock acquisition 132
diseases: Ceratomyxa shasta 326; enteric redmouth (ERM) 307
eggs, incubation 199
spawning 165
survival, growth, hatchery-wild crosses 147
Stress
diseases 265-268
factors 265; 267-268
handling 85, 358
Sunfish, redear
disease, bacterial gill disease 301
eggs, temperature units 191
formulated feed 138
rearing-pond management 102
Suspended solids 10-11
Swedish pond 43
Temperature requirements 134-137
Total alkalinity, hatchery water 15
Total hardness, hatchery water 15
Transportation
airplane 348-349
stress 358-359
tanks: aeration 353-355; anesthetics 359-360; carrying capac-
ity 360-364; circulation systems 352-353; design 350-352;
insulation (A"- factor) 350-351; water quality 355-358
trucks 348-350
Trout
anesthetics 170, 359-360
broodstock acquisition 132
INDEX 515
Trout [continued]
diseases: bacterial gill disease 300; bacterial kidney disease
312-313; Ceratomyxa shasta 326; Chilodonella 319; colum-
naris disease 302; copepod parasites 333-334; enteric red-
mouth (ERM) 306-308; Epistylis 319-322; fin rot 304;
fungus 314; furunculosis 300, 304-306; Gyrodactylus
330-331; herpesvirus disease 298-299; Hexamila salmonis
323-324; Ich 316-319; Ichtyobodo [Costia] 315-317; infec-
tious hematopoietic necrosis (IHN) 296-297; infectious
pancreatic necrosis (IPN) 294; motile aeromonas septicemia
(mas) 307-310; Myxosoma cerebralis 327; peduncle disease
303-304; Pleistophora 328-329; Sanguinicola davisi 332; Tri-
chodina 320-322; vibriosis 310-311; viral hemorrhagic septi-
cemia (VHS) 295-296
eggs: coloration 232; development 174-175; disinfection 189,
282; sensitivity, artificial light 190; enumeration 175-185;
incubation 193-198; sorting 185-187; storage 193; tempera-
ture units 190
feeds and feeding: egg coloration 232; energy availability
225-226; fish flavor 232-233; formulated 234-236,
394-395, 400; frequency 255-257; guides 239-248; initial
255; rates 210; sizes 258; skin coloration 232; spawning
activity 133; storage 233-238
handling, loading 358-359
nutrition: carbohydrates 218-219; diseases 222-223 (liver
degeneration), 231 (goiter), 390-393; lipids 221-223; phos-
phorus absorption 231; proteins 214, 216, 236; vitamins
227-229, 232
oxygen requirements 7
spawning methods 156-159
sperm storage 193
stress, disease 265-268
temperature: requirements 134-135; Standard Environmental
Temperatures (SET) 211
tolerance: ammonia 21; nitrite 22; nitrogen gas 9; salinity 13,
total dissolved solids 12
toxicity: ammonia 21; nitrite 22
transportation: methods [see Chapter 6); tank carrying capa-
city 361
treatments: copper sulfate 276-277; formalin 275-276; nitro-
furans 280-281; potassium permanganate 278; quaternary
ammonium compounds 278; salt 275; sulfonamides 281;
Terramycin 279-280
516 IISH HAUHKRY MANAGEMENT
Trout [continued)
used, forage fish 140
Trout, brook [see also Trout)
hybridization 148
initial feeding 256
mineral absorption 13
shipping, small containers 366
spawning 134-135
temperature requirements 134-135
Trout, brown [see also Trout)
initial feeding 256
spawning 134-135
temperature requirements 134-135
Trout, cutthroat {see Trout)
Trout, lake [see also Trout)
hybridization 148
spawning 134-135
temperature requirements 134-135
Trout, rainbow [see also Trout)
anesthetic 170
feeds and feeding: guide 240; initial 256
nutritional diseases 230
selective breeding 145
spawning methods 134-135
temperature requirements 134-135
transportation, small containers 366
Turbidity, ponds 112
V-trap 86- 87
Vertebrates, ponds 114
Volume-weight chemical calculations 402
Walleye
broodstock acquisition 132
carrying capacity, ponds 77-78
disease, lymphocystis 299-300
dissolved solids absorption 14
eggs 159, 192; temperature units 191
feeds and feeding: formulated 248, 399, 400; guide 248-249;
initial 256
forage fish for 140
INDEX 517
Walleye [continued]
nutrition: diseases 390-393; protein 217
oxygen requirements 8
rearing-pond management 102
spawning 132, 134-135
temperature requirements 134—135
transportation: small containers 367; tank carrying capacity
364
Water
loss, ponds 1 13
quality criteria 14, 15
reconditioning 19
supply structures 90
Weed control, aquatic
biological 103-104
chemical 104-105
mechanical 103
Weight- volume chemical calculations 402
Weir operation, use 384—386
6 U.S. GOVERNMENT PRINTING OFFICE: 1982-329-l.iO
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