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Growth and feeding of juvenile chinook salmon, Oncorhynchus Tshawytscha, in "in situ" enclosures English, Karl K. 1981

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GROWTH AND  FEEDING  OF  J U V E N I L E CHINOOK  ONCORHYNCHUS TSHAWYTSCHA,  IN  "IN SITU"  SALMON,  ENCLOSURES.  By  KARL B.Sc,  A THESIS THE  KRISTOFER  Cornell  SUBMITTED  ENGLISH  University,  1978  IN P A R T I A L F U L F I L M E N T  REQUIREMENTS MASTER  FOR OF  THE  DEGREE  OF  SCIENCE  in THE  FACULTY  OF  (Department  We  accept to  THE  this  GRADUATE of  UNIVERSITY  OF  Karl  as conforming standard  BRITISH  November  ©  Zoology)  thesis  the required  Kristofer  STUDIES  COLUMBIA  1981  English,  1 981  OF  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the  r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t freely  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  agree t h a t p e r m i s s i o n f o r e x t e n s i v e f o r s c h o l a r l y purposes may  copying of t h i s  understood that copying or p u b l i c a t i o n of t h i s gain  <dl&0 A*g y  The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  DE-6  (2/79)  It is thesis  s h a l l n o t be a l l o w e d w i t h o u t my  permission.  Department o f  thesis  be g r a n t e d by t h e head o f my  department o r by h i s o r h e r r e p r e s e n t a t i v e s . for f i n a n c i a l  I further  written  ABSTRACT  A  feeding  growth  rates  zooplankton. were  i n 90 m  enclosures  at  retaining  experimental while  food  zooplankton  f o r salmon  abundance  would  growth examined and  appear  spacing have  previous  of  vary  food  a  zooplankton.  A minimum from  constant  from  was to  six  week  3.9%/day  of  1.4-4.5mm  the s i z e and  of  successful  This  response value i s  capabilities  and  experiments.  to  daily  of the enclosed  variations  abundance.  in  Extremes  water  in  and c o n s i s t e n t e f f e c t  However,  a  relationship  a functional  the o t o l i t h s  i n order  grew  scarce.  with  on  rings.  fish  and abundance of  rate  physical  The  establish  zooplankton.  a significant  growth  a  strong  s t u d i e s and tank  respect  t o have  ranged  directly  o n 1.4-4.5mm  field  for  used  i s  B.C.  ,  circulation  and t h e abundance  t o a salmonids  with  t o be kept  were  There  item.  tshawytscha  Inlet,  gr.owth a n d t h e s i z e  increments  the  when  fish  of pelagic  The e n c l o s e d  rates  was e s t i m a t e d  feeding  in relation  from  were  of a prey  abundance  weight/day  growth  rates  how  and zooplankton  salmon.  methods  growth  3  temperature  the  fish  size  examine  Oncorhynchus  t o -0.5%/day  fish  2.0m /hour  Daily fish  Weekly  of s u c c e s s f u l search  of  results  juvenile  to  i n Saanich  water  o f 1.8% w e t b o d y  between  contrast  discussed  salmon,  i n the enclosures.  Rates  search  rate  the  enclosures  analytical  the  inherent  5-6 g r a m  designed by  ample  was a b u n d a n t ,  relationship  prey.  mesh  3  period.  Several  between  affected  permitted  an a v e r a g e  curve  are  was  J u v e n i l e chinook  raised  while  experiment  water  to establish  food on  temperatures any  closer  i i  relationship  between  food  i  abundance  and  otolith  growth  rings.  iii  TABLE  OF  CONTENTS  INTRODUCTION  DESCRIPTION  .  OF  PROJECT S I T E  P A R T ONE The  1  4  . .•—  ".  .'  6  Methodology The  6  Apparatus Flotation Net  6 Platform  7  Enclosures  7  Protective  Net  Laboratory  H o l d i n g Tank  The  9 10  Procedure  11  Sampling  The  Sampling  The F i s h  General  Zooplankton  1-1 13  Results  13  Quantitative  Data  Zooplankon Fish  Samples  14  Samples  Qualitative Summary  14  22  Data  30  Of R e s u l t s  32  Discussion  32  PART TWO Growth  35 And F e e d i n g  Of A P l a n k t i v o r o u s  Methods Salmon  Fish  •..  35 36  Energetics  Model  37  iv  Multispecies Results Fish  Disc  Equation  And I n t e r p r e t a t i o n Growth  Vs  Relative Rates  Rates  45  Zooplankton  Functional- Response  Prey  42  Abundance  For Planktivorous  Of S u c c e s s f u l  46 Fish  ....  Search  51  Of S e a r c h  53  Distribution  57  Discussion  58  PART T H R E E Growth  63 Patterns  On  T h e O t o l i t h s Of T h e E n c l o s e d  Methods Daily  Increments  66 Growth  Growth  Rings  Patterns  On  66 The S a g i t t a e  66  Discussion  AND  LITERATURE  70  CONCLUSIONS  '  CITED  II.  Handling  75  77  APPENDICIES I.  63  64  Results Daily  Fish  63  Measuring  SUMMARY  49  83 The F i s h  83  Transport  83  Vaccination  84  Weighing  And M e a s u r i n g  Branding  The F i s h  Handling  The Nets  The F i s h  84 85 86  V  Deployment Cleaning III.  Of  The  Calculation  Nets  ...  86  Enclosures Of  Fish  Growth  87 Rates  88  vi  LIST  OF  TABLES  Page Table  Table  Table  Table  Table  Table  Table  1.  2.  3.  4.  5.  Probability values from univariate and m u l t i v a r i a t e a n a l y s e s o f v a r i a n c e f o r "AM" and "PM" zooplankton samples. Symbols: 1 = 9 mm enclosure with fish. 2 = 19 mm enclosure with fish. 3 = 19 mm enclosure without fish. 4 = o u t s i d e the e n c l o s u r e s  18  The dominant s p e c i e s i n t h e t o p 10 m e t e r s o f water at the e x p e r i m e n t a l site from May 12 through June 29. C i r c l e s i z e i n d i c a t e s level o f d o m i n a n c e w i t h i n e a c h week  21  Probability v a r i a n c e of  27  v a l u e s f r o m two stomach content  The juvenile salmons' s u c c e s s f u l s e a r c h f o r the in the e n c l o s u r e s  way data  analysis  of  relative rates of various prey found 52  The correlation m a t r i x f o r the 9 prey groups for which rates of successful search were calculated. Values above .85 indicate s i g n i f i c a n t c o r r e l a t i o n (p<.05) ,  52  S e a r c h r a t e s f o r the range of prey s i z e s found i n t h e e n c l o s u r e s . The maximum search rates were d e r i v e d f r o m l a b o r a t o r y m e a s u r e m e n t s . The probable range assumes that the reactive d i s t a n c e f o r f i s h f e e d i n g i n the e u p h o t i c zone i n 0.3-0.5 o f t h e l a b o r a t o r y v a l u e ,  57  The c o r r e l a t i o n m a t r i x f o r the daily growth increments of six fish (A2,A4,A5,Al0,B8,D); temperature data (Temp); zooplankton data (Zoo); and a combination of temperature and z o o p l a n k t o n d a t a ( T & Z ) . V a l u e s a b o v e .44 are s i g n i f i c a n t (p<.05) and v a l u e s above .56 are highly significant (p<.0l) ,  69  vii  LIST  OF  FIGURES  Page Figure  1. L o c a t i o n Inlet,  of  offshore  platform  in  Saanich  B.C  Figure  2. T h e  Figure  3. F l o t a t i o n p l a t f o r m w i t h the protective s u r r o u n d i n g t h e f i n e mesh e n c l o s u r e s  net  4. T h e spatial and temporal v a r i a t i o n s of z o o p l a n k t o n . The s o l i d line represents data from o u t s i d e samples. S y m b o l s : • 9 mm e n c l o s u r e w i t h fish. • 19 mm e n c l o s u r e w i t h fish. * 19 mm e n c l o s u r e w i t h o u t fish  "AM" the  5. T h e spatial and temporal v a r i a t i o n s of z o o p l a n k t o n . The s o l i d line represents data from o u t s i d e samples. S y m b o l s : • 9 mm e n c l o s u r e w i t h fish. • 19 mm e n c l o s u r e w i t h fish. * 19 mm e n c l o s u r e w i t h o u t fish.  'PM" the  Figure  Figure  Figure  Figure  Figure  fine  5  mesh  enclosure  8  10  15  16  6. N o n - p a r a p e t r i c correlation coefficients. Zooplankton from each enclosure were correlated against samples from o u t s i d e t h e Correlation coefficients above enclosures highly significant the dashed line are (p<.0l). fish. S y m b o l s : 1 = 9 mm e n c l o s u r e w i t h fish. 2 = 19 mm e n c l o s u r e w i t h fish, 3 = 19 mm e n c l o s u r e w i t h o u t 4 = outside the enclosures  19  7. T h e a v e r a g e d a i l y g r o w t h r a t e f o r individual fish i n t h e two o f f s h o r e e n c l o s u r e . The i s t h e b e s t e s t i m a t e o f t h e mean d a i l y g r o w t h r a t e f o r a l l f i s h d u r i n g t h a t week  23  8. C u m u l a t i v e salmon  24  growth  of  the  juvenile  chinook  vi i i  Figure  9. T h e relative types of prey f i s h from the mm e n c l o s u r e Symbols: S = M = L = XL =  •  Figure  10. T h e r e l a t i v e the stomach salmon.  •  importance (IRI) of the v a r i o u s found i n t h e stomachs of the 9 mm e n c l o s u r e ( t o p ) a n d t h e 19 (bottom). s m a l l p r e y (0.7-1.4 mm) medium p r e y ( 1 . 4 - 3 . 0 mm) l a r g e p r e y (3.0-10.0 mm) e x t r a l a r g e p r e y (>10 mm)  = pelagic  prey.  = nonpelagic  prey  29  proportion of each prey group i n contents of the j u v e n i l e chinook  Calanus  species  Calliopius Decapod  larvae  Euphausids 31  Parathemisto Figure  Figure  Figure  Figure  Figure  Figure  11. T h e r e l a t i o n s h i p s b e t w e e n f i s h growth rates and the abundance of a s m a l l (0.7-1.4 mm) zooplankton  47  12. T h e r e l a t i o n s h i p s b e t w e e n f i s h growth rates and the abundance o f a medium (1.4-3.0 mm) zooplankton  47  13. T h e r e l a t i o n s h i p s b e t w e e n f i s h growth rates and the abundance of a large (>3.0 mm) zooplankton  48  14. T h e r e l a t i o n s h i p s b e t w e e n f i s h growth rates and t h e abundance o f a medium and l a r g e ( 1 . 4 4.5 mm) z o o p l a n k t o n  48  15. T h e functional salmon to the zooplankton  50  response density  of j u v e n i l e chinook of 1.4-4.5 mm  16. T h e mean reactive distances ( d a t a ± 95%) o f rainbow t r o u t to low contrast targets of v a r i o u s s i z e s (Ware 1973)  55  ix  Figure  Figure  Figure  17.  18.  19.  The pattern of daily growth increments d e r i v e d from the s a g i t t a e of s i x f i s h raised in the experimental enclosures  66  C o m p a r i s o n o f t h e mean g r o w t h i n c r e m e n t s w i t h water temperature and z o o p l a n k t o n abundance data  68  Sample p h o t o g r a p h s of the s a g i t t a e h a t c h e r y and tank r e a r e d f i s h  72  from  two  X  ACKNOWLEDGEMENTS  Dr.  C.A.S.  stimulated grateful  my to  encouragement to  my  wife,  of  this  interest  in this  D r . T.R. during  Cindy,  and  valuable  other  type  f o r her major  and  like  of feeding for  the i n i t i a l  his  planning  originally  experiment.  t o thank  phase.  D r . R.  I am  assistance I am  contributions during  support,  indebted  each  Hilborn  and Dr. C . J . Walters  and  phase  for his for  his  suggestions.  individuals  especially  b y D r . G.C. L a u r e n c e  Parsons  financial  comments  Many  Cahoon,  and a study  p r o j e c t . I would  patience  would  Hall  like  a n d D. M a r m e r e k .  made  t o thank  important  c o n t r i b u t i o n s , but  D r . E.B. B r o t h e r s ,  B. E g a n ,  I P.  1  INTRODUCTION  Over primary  the  and  past  their  on  yet the  pelagic  difficulties on  natural  prey.  however,  growth  levels Higgs  using  Brett  hour  observation could  be  prey  minimized, of  a  feeding  trials  food  growth  and  body  portion  fish  size,  foods  were  chum  three  young to  salmon  the  and  technical  fish  feeding  to  has  of  the  energy  expended  predator  Lebrasseur. because  and  in  on  Brett  juvenile  longer  growth fed  0.25  In  these  m  tanks  3  searching that  relationship how  rates  various  prey.  the  and  zooplankton,  what  concluded the  ration  used  in  are  1976b).  prey  natural  have  salmon  examine  were  the  investigated  a l . 1969;  to  in  studies  juvenile  determine  to  dependent  these  (1969)  salmon  the  represented  1976a,  classes  distinct  necessary  et  first  Lebrasseur  when  of  Brett  the  sizes  weeks  is strongly  been  metabolism,  offered  were  has  data  Brett  (Brett  1975;  8  item.  new  due  of  foods.  were  prey  grown  well  composition  experiments.  of  marine  has  planktivorous  are  natural  different  obtained  on  physiology  between  is largely  small  Shelborn  times'' of  experiments,  capturing  a  base  zooplankton.  a l . (1968)  on  concentrations  which  and  et  feeding 2  gap  various a r t i f i c i a l  Lebrasseur salmon  only  and  salmon little  experiments  temperature,  1970;  and  studying  f e e d i n g on  rate  by  of  This  c o n c e n t r a t i o n s of  salmon  information  relationship  involved with  literature;  affected  production  critical  feeding  how  the  comparatively  Salmon  examined  years  secondary  consistently, collected  20  much  and  further between  energy  is  2  expended  in  and  (1966);  Davis  Kerr  searching Mann  and  Martin  (1968)  To  escape  the  developed  for  and  capturing  (1966);  d i f f e r e n t prey.  Paloheimo  a l l support  and  this  r e s t r i c t i o n s of  tank  experiments,  new  methodology  involving  experiments.  The  methodology  involved  the was  Oncorhynchus  water  column,  monitored  that  in  dependent  on  encountered The  as  The  prey  is organized  of  this  two  over  the  in  behaviour  concentrations  moved  through  the  rates  are  growth  range  chiook  enclosure  s u r v i v a l , and  that  study  feeding  juvenile  semi-open-,  was  this  situ"  placing  masses  with  and  others,  an  in  juvenile is  apparatus. for  the  of  prey  to  growth  How are growth a v a i l a b l e food  (3)  How  efficient  densities  section  this  study  concludes  of  confirm  These  related  juvenile  or  provides  situ"  on  a  enclosure  evaluating  discussion  a  and  the  proposes  some  q u a l i t a t i v e data  laboratory  resolve  with  one  enclosures.  several  work  to  food by  fish  Brett  uncertainties  are:  size  finding  discussion  refute  J.R.  from  abundance? the  at  by  major  uncertainties  rates affected organisms? are  Part  "in  placed  quantitative  fish  (2)  the  brief  these  feeding.  How  parts.  of  is A  results  attempt  (1)  three  emphasis  fish  The  in  evaluation  integrates  enclosures  of  and  Special  the  about  densities  a  "in  zooplankton  water  hypothesis  applications  Part  natural  and  naturally.  methodology.  practical  growth,  natural  description  performance  where  basic  thesis  detailed  ,  r e l a t i o n to  changed  enclosures.  tshawytscha their  in  (1966);  conclusion.  a  salmon,  Dickie  Warren  of  hypotheses  how  of  the  food? the  findings •  generated  from  3  previous  studies.  Part of  the  their  three  examines  experimental otoliths.  between  daily  The  relative  fish, object  growth  temperature  and  experimental  enclosures.'  and  zooplankton  daily  estimated was the  to  growth from  rates, the d a i l y  establish  daily abundance  for  some  rings  on  relationships  fluctuation observed  in in  water the  4  DESCRIPTION  The  experimental  Saanich  Inlet,  for  following  the  area  for and  water  exceeds  standing  has  crop  relatively is  remote  enough larger  British  low  current  that  of  levels  are  from  at  site  zooplankton;  well  known  open  ocean;  platforms,  and etc.)  enclosures. excellent  and  These  site  to  to (8)  most (9)  PROJECT  that  the  inlet  the  relatively  of  (7)  the  reduced  "in situ"  natural  feeding  the make  enclosures.  of  the  production  and  the  food  webs  are  the  site  is  deep  (6)  inlet  migration  of  assemblages also  occur  equipment  cost  major  (4)  vertical  CEPEX  from  depth  the  occurring there  of  selected  species);  phyto-zooplankton  species some  (5)  in  was  the  zone;  few  the  site  a  (3)  pollution;  experiments  is sheltered  high;  relatively  accomodate the  CEPEX  is  area  euphotic  characteristics test  the  ( F i g . 1). T h i s  (2)  the  greatly  of  SITE  velocities;  (i.e.,  sources  the  (1)  salmon;  simple  was  Columbia  reasons:  juvenile  storms  site  OF  of  are the  (buoys,  setting  Saanich  in  the  up  Inlet  the an  5  Figure  1.  L o c a t i o n of o f f s h o r e p l a t f o r m i n S a a n i c h B.C. (Adapted from B a r r a c l o u g h e t a l . 1968)  Inlet,  6  PART ONE  The  The to  concept  study  of  pelagic  large  attention  1975;  et  Gamble  1978). water  Most in a  closed  water  exception rates  for  number new were  were  used  THE  bag  and  the  closed  and  chum  micro-zooplankton.  smaller  and  in this  used  much  Studies  situ" The  et  a  a  column and  chambers  in  determined  than  consisted  of  the  growth  declining  nitex of  designed  net  these  introduced a  fine  rates  of  food  with  steadily,  of  et a l .  fishes  a l . (1978)  made  mesh  of  who  et a l .  Laurence  nonexistent  growth  finer  received  productivity  f e e d i n g on  chambers,  "in  the  column  Davies  enclosing  (1977),  Laurence  1975;  1977;  almost  Parsons  semi-open  assess  system.  salmon  a l .  a l .  water  recently  involved  been  zooplankton.  where  et  et  i n the  has  monitoring  have  Koeller  to  on  developed  of  prey  concept  feeding  studies  juvenile  of  (Takahashi  these  columns  of  systems  Grice  plastic  dynamics  containers placed  a l . 1977;  of  chain  Methodology  marine  significant  •  mesh,  larval by  the  fish  Laurence enclosures  study.  APPARATUS  The  experimental  components:  (1)  the  apparatus flotation  platform;  (2)  the  four fine  major mesh  net  7  enclosures; laboratory  Flotation  a  large  holding  flotation  was  one  of  platform  three  Experimental  describe  the  large  s t r u c t u r e was  Saanich  Net  protection  net;  and  (4)  a  (10  meters  constructed  in diameter  for  Controlled  (CEPEX) p r o j e c t s . M e n z e l flotation  permamently  module  moored  and  originally  in  and  60  meter  Ecosystem  Chase  used  meters  1  (1977)  in  of  CEPEX.  water  in  Inlet.  Enclosures  The  enclosures  permitting  free  Three  to  food  limit  The  the  1  mm  were  movement,  zooplankton.  mesh size  mesh  and  the  with  knotless  were  the  enclosure depth  was  flat  meters  19  nylon of  mm  this  3.1  meters  the  bottom  pursed). the  specific  the  fish  g  fish  size  19mm)  in each  screening). enclosures  while  ranges  were  constructed  experiment  roughly  -above  of  and  5-6  of  selected  enclosure. with  black  The  9  mm  mesh  were  constructed  four  enclosures  mesh.  of  The  retain  9mm,  mesh  one  (not  to  to  was  inside  ( F i g . 2).  roughly  (1mm,  window  two  purposes  placed  out,  enclosure  enclosure  For  i n and  available  (flexible  green  designed  sizes  permascreening  0.5  mesh  tank.  Pollution  The  coarse  Platform  The high)  (3)  The  of  CEPEX  flotation  in diameter each  sides  surface  the  of  and  enclosure of the  the  platforms. 12 was  meters  in  circular  and  enclosures  water  to  Each  retain  extended jumping  8  12 meters  3.1 meters  Figure  2.  The  fine  mesh  enclosure.  9  fish; was  thereby  not a  in  filled net.  rings, a  below  sand  two  the  methods  and g r a v e l  remaining  the  polypipe  to the  nets  ring  was  of  the  bottom  the net a t 4 m and a t 8 m  of these  phytoplankton  n e t was  predators  from  of  seine  11 cm  suspended  from  s i d e s away  fouling  enclosures "are  and t h e  described  in  mesh,  designed damaging  salmon. was  10 m  the f l o t a t i o n from  the  to prevent the  fine  fish  mesh  net,  i n diameter  17 m  and  and  other and  constructed deep.  16 w e i g h t e d  experimental  and  enclosure  The p r o t e c t i v e  platform  four  dog  I t was  ropes  enclosures  held  hanging  (Fig. 3).  Laboratory  The that  supported  One  held  Net  the juvenile  inside  shape.  The deployment  devouring  its  polypipe,  and a t t a c h e d  rings  t o remove  protective  aquatic  predation  I.  Protective  A  o f 38 mm  cylindrical  surface.  used  Appendix  constructed  roughly  with  The  the n e c e s s i t y of a top. Avian  factor.  Three open  precluding  was  Holding  holding  Tank  tank  contained  recycled at a constant  oxygen  from  three  airstones.  tank,  maintained  the water  temperatures day-night  t o those light  liters  rate  temperature offshore  were  of f i l t e r e d  sea water  and s u p p l i e d with  A cooling  i n the  intervals  300  system, at  in  12°C ±  an  adjacent  1°C,  (similar  enclosures).  maintained  adequate  Consistent  and t h e tanks  opaque  Figure  3.  Flotation platform s u r r o u n d i n g the f i n e  with mesh  the protective enclosures.  net  o  11  sides  prevented  activities  THE  the  fish  from  being  disturbed  by  routine  i n the l a b o r a t o r y .  PROCEDURE  On from  18 May  Capilano  1980,  Hatchery,  following  day  offshore  enclosures  220  holding  tank.  placed  in  each  weight  and  85 mm  natural May,  The  more  mean  tank  of  starved  The  fish  and  obtained  daily  movement week  was  qualitative zooplankton  experimental  period.  the  once  a  of were  data.  90m  3  salmon 6.2  g in  feed  on  On  26  starved.  to the laboratory  The  weight  and  length  week. was  evaluated  and weekly  plankton recorded  the  could  Quantitative  samples  The  fouling,  each  with  data fish  both were  samples.  zooplankton  day d u r i n g  the  six  Zooplankton  Zooplankton hours  experimental  added  of the e n c l o s u r e s  feeding  12  recorded  of  juvenile  fish  were  size.  branded.  identical:  enclosed  were  salmon,  i n the l a b o r a t o r y  the  virtually  . salmon  observations  and  of  laboratory fish  fish  Sampling  every  while  i n two  retained  l e n g t h . The  chinook  measured, and  size  was  juvenile  placed  were  t o i n c r e a s e the sample  quantitative  Qualitative  were  initial  i n fork  performance  from  11  enclosure  240  weighed,  fish  and  juvenile  holding each  were  of these  zooplankton  20  approximately  samples at  period.  1000 Two  were and  collected 2200  samples  on  hours were  a day-night  basis  throughout  the  obtained  from  at  least  12  three The  of  five  five  possible  locations  locations  f o r the  plankton  inside  the  19  mm  mesh  enclosure  with  (3)  inside  the  19  mm  mesh  enclosure  without  (4)  outside net.  (5)  outside  A  vertically  between  protective  hauled  best  and  Grice  until  samples  of  were  Samples be  were  splitter  counts.  The  to  than  10  mm  in  were  removed  and  weight  the  counted  sample.  with  other  cards  along clarity  of  phytoplankton; speed  of  the  the  the  and  counted The  bags  split  recorded  >3.0  mm.  data  ml  of  three and  medusa  recorded  the on  a  the  Amphipods any  of  using  for  measuring  were  15  sets  were  to  ends  with  precision  and  (Lawson  cod  recent were  length  the  provided  the  prior  for i t s  comparability  preserved  samples  to  in  hauls  most  counts  1.4-3.0 mm;  ctenophores of  two  The  and  replacable  and  maximize  Zooplankton  0.7-1.4 mm;  greater  emptied  used  chosen  i n CEPEX  in  was  abundance  net  abundance  day.  protective  was  accuracy,  retained  laboratory. each  method  integrated  carefully  analyzed  plankton  Euphausia  precision,  zooplankton  the  urn m e s h  on  i n the  groups:  202  Based  could  subsequent  with  zooplankton  vertically  fish.  x  to  estimate  were:  fish.  inside  ability  1977).  formalin  Net  period.  fish.  This  measure  they  but  net.  Bongo  with  abundance.  experiments,  the  size  enclosures  zooplankton  bags.  Folsom  the  enclosure  hauls  (2)  CEPEX  the  sampling  9 mm  the  mesh  each  the  demonstrated  the  during  (1) ' i n s i d e  sample  of  possible  or wet  5 x  8  relevant qualitative  i n f o r m a t i o n such  as  sample  microzooplankton  and  weather  vertical  in  terms  of  c o n d i t i o n s when haul;  and  the  the  date  sample  and  time.  was  taken;  13  Sampling  the  Fish  Initially using  the  obtained  once  of  the  of  in  subsequent to  with  the  fish  first  an  week  and  forty  fish  for  returned  to  after  they  fish stomach their were  following  water,  in  content  none  fine  material  for  was  too  the  The  rapidly would  fish  structural an  mm an  more  enclosure  mesh  Only  10  were  and  would  fish  were  were  of  were  were  and  One  out  preserved the  not  rinsed  examined,  In  transported  approximately fish  in  net  measured.  rest  m  sacrificed.  immediately The  2.5  were  in  fish  were  one  hour  replaced.  with  fresh  their  bodies  alcohol.  mesh  by  with  would  semi-open  moderate  for  (Laurence be  wave  phytoplankton  suitable  support  Results  permascreening  "in situ"  torn  clogged  be  and  sacrificed  contents  mm  branded  samples  net  enclosure  weighed  and  Fish  19  these  analysis.  preserved  stomach  1  easily  of  each  were  General  The  this  enclosure.  sacrificed  removed.  95%  with  I.  shaped  respective enclosures  day  their  preserved  was  conical  from  they  measured  i n Appendix  tows  in  l a b o r a t o r y where 4  weighed,  a  vertical  weeks  every  was  described  week  the  formalin  The  a  Three  90%  sampled  fish  methods  diameter. recover  every  limited  was  a  suitable  enclosure. This  enclosure  and  tidal  growth.  a  smaller  et  a l . 1978).  to  areas  or  not  action,  Permascreening  enclosure The  time  with  utility periods  and mesh more  of  such  of  low  1  phytoplankton  productivity.  were much more  durable  of  phytoplankton  and  growth  The  could  using  9 mm be  the  and  19  mm  maintained methods  mesh  enclosures  relatively  described  4  in  •free  Appendix  II . The sizes The  of  mesh  small  Euphausia  Zooplankon  the  data  connected For of  were in  an  several  exclude mesh  found  did  the not  and  screen  limit to  be  the  largest  in Saanich  gathered  the  out  9 mm  any  food  impractical. mesh  zooplankton size  was  (adult  class  of  Inlet.  c a t e g o r i e s of  samples with  a  86  Bongo.hauls,  times  night  during  spatial  illustrates  "PM"  and respect  the  gathered  temporal to  size  variations  in  from  more  than  5 depicts similar  data  gathered  samples.  outside  the  In  these  figures,  enclosures  has  113  the been  line. 95%  (Weibe  Replicate hauls  4  Figure  taken  solid  assess  zooplankton  samples.  additional  to  concentrations with  species. Figure  observation  1977).  proved  phytoplankton,  zooplankton  "AM"  from  fish  to  DATA  dominant  from  mm  sizes  Samples  variations  daylight  19  mesh  juvenile  with  to  commonly  Samples  size  different  the  clogged  ) . The  QUANTITATIVE  three  to  enough  zooplankton  and  using  available  1 mm  not  idea  confidence  and  were the  Holland obtained,  limits 1968; at  experimental  each  are  usually  Lawson sampling  and  50-200% Grice  location,  p e r i o d . These  samples  15  31<m6mai920Z125J72«29 JUNE  Figure  -  192:21222320252621:) 5 6 7 I 9 1011 •Zl^r^lSli 1RY JUNE  4. The spatial and temporal v a r i a t i o n s of "AM" zooplankton. The s o l i d l i n e r e p r e s e n t s the data from o u t s i d e samples. Symbols: • 9 mm e n c l o s u r e with f i s h . • 19 mm e n c l o s u r e with f i s h . * 19 mm e n c l o s u r e without f i s h .  Figure  5.  The s p a t i a l and temporal variations of z o o p l a n k t o n . The s o l i d l i n e r e p r e s e n t s t h e from o u t s i d e samples. S y m b o l s : • 9 mm e n c l o s u r e w i t h fish. • 19 mm e n c l o s u r e w i t h fish. * 19 mm e n c l o s u r e w i t h o u t fish.  "PM" data  17  provide class  an  estimate  of zooplankton.  an  observation  for  medium  used  were  the  way  of  to  concentrations  inside  significantly enclosures i n both  The  observation  size  for  small counts  class.  was  (p<.0l)  between  'two  (p<.05)  "PM"  were  enclosure  nonparametric  untransformed mm)  i n t h e 9 mm  not  highly  facts  the  and  zooplankton fish  measured for  were  outside  each  size  were  also  1).  ( F i g .6 ) .  mesh  highly  fish  correlations  data  in  zooplankton  without  those  (Table  variance  differences  with  consistent  samples  of  the  . However,  from  analysis  revealed  enclosures  mesh  and  enclosures.  and d a i l y  analyses  inside  important  analyses  These  19 mm  i n the outside following  most  experimental  the s p a t i a l  results  and  (>3.0  which  the  and  the  concentrations  the enclosures  different  "AM"  on  the  . These  Parametric  counterpart  of an  size  50-150% of  f o r zooplankton  and m u l t i v a r i a t e  differences  outside  category  each  observation  limits  the s i n g l e  concentrations.  concentrations  zooplankton  was  investigate  inside  performed  for were:  49-151%  f o r each  the performance  concentrations  class  count  limits  o f an  zooplankton  univariate  significant  the  10-180%  confidence  enclosures  zooplankton  not  and  95%  comparison  used  zooplankton;  limits  Concentrations  to evaluate Two  95% c o n f i d e n c e  of the f i r s t  Zooplankton  outside  The  for large  The  80-120%  The  t h e 95% c o n f i d e n c e  zooplankton;  zooplankton. were  of  enclosure  correlated  The was  (p<.0l)  large the  only  with  i t s  not  the  samples. suggest  that  the  fish,  18  Samples  Univariate Analysis by S i z e Small Medium Large  Mult ivar i a t e ( W i l k s Lambda)  AM 1 - 4 2 - 4 3 - 4  .0004 .0010 .2675  .0256 .0004 . 1 209  .0202 .0532 .0661  .001 5 .0006 .041 1  PM 1 - 4 2 - 4 3 - 4  .001 1 .0004 .6216  .0010 .0001 .0907  .0214 .0118 .8999  .0048 .0006  Table  and 1. P r o b a b i l i t y values from univariate multivariate analyses o f v a r i a n c e f o r "AM" a n d "PM" z o o p l a n k t o n samples. S y m b o l s : 1 = 9 mm e n c l o s u r e w i t h fish. 2 = 19 mm e n c l o s u r e w i t h fish. 3 = 19 mm e n c l o s u r e w i t h o u t fish. 4 = outside the enclosures.  19  RM  SAMPLES  PM  SAMPLES  .8 +  .6 \ o I—  cr  .4  +  •2 +  S  M  1  Figure  -4  6.  L  S  M  2  -4  L  S  M  3 - 4  L  S  M  1 -4  L  S  M  2 - 4  L  S  M  3 - 4  Non-parapetric correlation coefficients. Zooplankton from e a c h e n c l o s u r e were correlated a g a i n s t samples from outside the enclosures. Correlation c o e f f i c i e n t s a b o v e the dashed l i n e are highly s i g n i f i c a n t (p<.0l). S y m b o l s : 1 = 9 mm enclosure with fish. 2 = 19 mm enclosure with fish. 3 = 19 mm enclosure without fish. 4 = o u t s i d e the e n c l o s u r e s .  L  20  enclosures,  were  responsible  zooplankton  concentrations.  for The  the  observed  concentration  predators  (juvenile  fish)  enclosures  with  The  zooplankton  inside  enclosures  with  fish  the  zooplankton inside  enclosure  Dominant  12  of  dominant June  Calanus the  were  are  species  experimental  codominant  placed  in  larvae  could  In  the  period.  be  the  codominant  over  a l l others  in  was  the  common  most the  Parathemi sto and  fourth There  sampled never while  in  zero  considered size  outside  concentrations  ( F i g . 4 and  the  the  the  measured than  the  enclosures  or  5).  in Table each  Calanus  individual  pac i f i c u s  species was  adult  in  also  sixth  week.  and  decapod  species  were  Decapod  larvae  were  dominant  Parathemisto  pacificus  species.  common,  fish  week.  species  the  the  most  Euphausia  second  the  class;  in  larval  May  obvious  throughout  and  the  from  is readily  before  Copepod size  It  period  class  week  codominant  medium  2.  size  through  organisms.  dominant  experimental  (the  class,  the  i n s i d e than  outside  the  planktivorous  c o n s i s t e n t l y lower  However,  enclosures)  large  clearly  over  dominated  were  was  fish  listed  i n week  the  were  of  in  Species  species 29  higher  measured  without  Zooplankton  through  that  was  concentrations  the  The  fish.  differences  Pseudocalanus  small  size  especially  minutus  class  while  in  third  the  week. was the  present several  only  one  various in were  obvious  difference  locations. Adult  samples found  in  taken samples  from  in  the  species  Euphausia  p a c i f i c u s were  the  mesh  taken  19  mm  from  the  enclosure 9mm  mesh  21  SIZE  RANGE  0 . 7 - 1 . 4 mm  WEEK  NUMBER  Calanus  species  Decapod  larvae  Epilabidocera Euphausid  larvae  0 1 2 3 4 5 6  1.4-3.0  mm  0 1 2 3 4 5 6  9  >3.0  mm  0 1 2 3 4 5 6  ••• • •  Parathemisto Pseudocalanus  Table  2. T h e dominant s p e c i e s i n t h e t o p 10 m e t e r s o f w a t e r a t t h e e x p e r i m e n t a l s i t e f r o m May 12 through June 29. C i r c l e s i z e i n d i c a t e s l e v e l o f dominance within e a c h week.  22  enclosure. All  the  stomach  Inlet,  al.  Fish  and  contents  Saanich et  genera  of  species the  sampled  fish  in accordance  are  with  i n the  major the  vertical  zooplankton  tows  species  observations  of  and in  Fulton  (1969).  Samples  The  weekly  survival  rates,  fish and  samples  the  prey  were  used  organisms  to  estimate  consumed  by  growth  the  and  juvenile  f ish.  Growth  Rates  Irrespective rates  (Appendix  daily  growth  were in  very the  rates  r a t e s of  high  for  the  to  fish  two  weeks,  in  last  two  the  fish  enclosures for  laboratory.  size Also,  held  then  increased  are  mesh  for  Figure  growth  weeks,  negative mm  8  over  salmon  the  i n the  last  next  shows the  Phillips  the  mesh  to on  drastically  high  weeks,  and  cumulative  by the  week,  week. The  were  for  the  declined of  period.  maximum  Barraclough  and  growth  growth  individuals  excess  The  enclosure  fourth  experimental  close  and  two  growth  ( F i g . 7).  dropped  enclosure  the  raised  9 mm  then  daily  same  in  rates achieved very  the  i n the  two  19  to c a l c u l a t e  remain  first  moderate  (4.9%/day)  similar  fish  enclosure  highest  used  patterns  become  weeks.  i n .each  The  methods  the  i n the  first the  the  week,  declined  of  the  I I I ) , the  third  finally  of  in  these  growth  rates  rations (1978)  in  the  calculated  23  9 MM ENCLOSURE  cr o  5K  o o  CD  UJ  o  CD  —i 2  f  3  r  1  4  WEEK NUMBER  5  19 MM ENCLOSURE cc a  0  a  • a CD  i  a  o  a  !  0  a  §  8  cc  g  CD  —i  2  Figure  7.  1  3  1  4  WEEK NUMBER  r  5  The a v e r a g e d a i l y growth rate for individual fish i n t h e two o f f s h o r e e n c l o s u r e . The is t h e b e s t e s t i m a t e o f t h e mean d a i l y g r o w t h r a t e f o r a l l f i s h d u r i n g t h a t week.  19 25 MAY  Figure  8.  Cumulative salmon.  growth  I  9  of  the  15 JUNE  juvenile  25 29  chinook  25  similar  growth  rates  salmon  residing  in  middle  of  '  juvenile  declined  in  week  was  in  at  period.  fish  the  Inlet  chinook  weight  probably  These  Saanich  for  a l l  from  the  species end  of  of  May  juvenile  through  the  June.  The  six  (4.0%/day)  an  The  salmon,  average rate  of  consistently  bottom  approximately  portion  rate  with  observed  of  of  weight  closely associated  were  starved  the  in  the  0.9%/day  loss  for  their  over  the  level  the  a  fish  activity.  their  against  same  starved of  maintaining  tank  laboratory,  position  current  of  4cm/sec.  Survival  The above the  survival rates  90%  experiment  enclosure, had mm  for  been mesh  and  the 106 97  recovered  in  the  had  survived  to  zero  natural  of  the Of  3  had  mortality  each  period.  initially stocked  enclosure  in  the  in  the  enclosure,  stomach  content  end  of  in  this  the  initially  19  fish  for  experimental  enclosure  At  stocked  the  died  laboratoy the  fish fish  Of  in  experimental  110 110  fish  the in  end  the  mm  40  in  9  the  had  analysis, period. the  of mm  enclosure  stocked  during  were,  been and  There  last  9  66 was  4  weeks  41  were  experiment. the  fish  sacrificed  in  period.  It  did  die;  not  the the  the  week  alive.  enclosure,  sacrificed  six  of of  for  stocked the  is highly  disassembling  rather, 'the  in  the  19  laboratory, probable they  apparatus  and  that  found  mm  a we  mesh 56  most way  survived of  out  found  enclosure,  the of  a  13  the  few  the  full  6  missing enclosure.  places  where  week fish Upon torn  26  meshes  produced  The  a  escape  hole  plus  through  natural  experimental  period  enclosure  0.28%/day.for  The 11  fish  the  and  starved starved  20  fish  starved  fish  Stomach  was  fish for  was  contents  were  differences  and  estimate  to  items  to  two  way  differences the  two  the  items growth  of  analysis in  the  prey  survived The  entire  9 mm  mesh  r a t e s . Of  the  and  13  mortality  enclosures  for  common  9  mesh  (p<.0l)  in  in  with  juvenile  variance  five  weeks  survived rate  for  reasons: the  stomach  of  of the  to  consumed; non-pelagic  sides  used  (Table  of  the  15  contents  to  test  for  contents 3).  (p<.05)  than  (1)  fish.  stomach  different  prey  the  was  the  , greater  the  two  contribution  in  Euphausia  more  for  present  adult  between  The  stomach  in only  one  mm  in  length,  of  the  fish  prey were  from  the  enclosure.  Nonpelagic  pelagic  the  survival  enclosures  the  of  category;  prey  5  associated  significantly  ten  lower  relative  were  growth  for  the  enclosure.  examined  contents  mm  during  1.0%/day.  between  the  (food  enclosures) A  mm  weeks.  approximately  determine  food  19  only  five  rate  escape.  Contents  Stomach  (2)  the  s i x weeks  could  0.086%/day  slightly  for  fish  mortality  only  had  starved  which  of  the  groups in  substrate).  food  sources  were  juvenile chinook found  origin  in  Amphipods,  a  major  in either  stomachs  ( i . e . not.  not  could  commonly  p r i m a r i l y the  contributor  enclosure. safely found  genus  be  Nine  to  the  of  the  considered  attached  Calliopius  to ,  any were  Organism  Enclosure  (>15 mm) Euphausi i d s Calliopius (3.0-15 mm) Euphausi i d s Decapod l a r v a e Calanus spp. (1.4-3.0 mm) Decapod l a r v a e Calanus spp. Parathemisto Pteropoda (0.7-1.4 mm) Parathemisto  Table  to Enclosure  Week  t o Week  .0001 .0769  .0036 1 .0000 .3190 .1829 .5340  . 351 3 .0739 . 1 355  .3190 .6597 .1595 .3496  .3513 .5291 .0000 .0163  .0583  .0000  3. P r o b a b i l i t y v a l u e s v a r i a n c e of stomach  from two way content data.  analysis  28  designated seldom  captured  observed  on  The the  the  the  stomachs  value  et  9  weeks. these  This  a l .  enclosed  of  These  yet  they  organisms  were  were  consistently  enclosures. of  by  the  v a r i o u s prey  means  index  of  an  reflects  the  clearly  diet  figures  of  by  form  the  the  also  during  observations  unimportance  hauls  multiplied  very  in the  These  group.  groups  index sum  the  of  found  of  relative  the  frequency  percent  occurrence  show  the  relative  juvenile  the  nonpelagic  high  the  fish  food  during  relative  previous  basis  importance the  three  to  the  The  relative  growth  of  the  fish. T h e c o n c e n t r a t i o n o f a m p h i p o d s on t h e m e s h steadily increased during the e x p e r i m e n t a l p e r i o d w h i l e the growth r a t e s of the f i s h s t e a d i l y decreased.  (2)  The fishes' growth rates were lowest enclosures when amphipods were the most component of the f i s h stomach c o n t e n t s .  (3)  V e r y few stomachs  (4)  The f i s h were n e v e r of the e n c l o s u r e s .  Several  other prey  prey  Higley  last  weeks.  f o r a s s e s s i n g the  items  of  insignificance  (1)  select  in  1971).  organisms  following  over  ranked  shows  prey  the  importance  was  (Pinkas  nonpelagic  of  of  percentages,  Figure  two  vertical  sides  (IRI).  volume  nonpelagic  i n the  relative  importance and  only  and  alterntive d u r i n g the  studies  drifting,  adhering Bond  to  1973).  prey last  were p r e s e n t two w e e k s .  observed  have  found  floating substrate  or  i n the  feeding off  that  juvenile  swimming  in both important  the  sides  chinook  salmon  water  column  in the  (Engstrom-Heg  fishes'  1968;  Becker  1973;  29  INDEX 200  S N L XL  S N L XL  JLT<£ I  JUNE a  INDEX zoo  OF R E L A T I V E  IMPORTANCE  T  5 M L X L  S N L X L  S M L XL  JUNE IS  JUNE 25  JUNE 29  DF R E L A T I V E  IMPORTANCE  T  160 4-  120 +  ao +  40 +  S  ti  L XL  S N L XL  JUNE 1  Figure  9.  JUNE a  S M L XL  S M L XL  JUNE 15  JUNE 2S  5 M L XL JtNE  29  The r e l a t i v e importance (IRI) of the v a r i o u s types of prey found i n the stomachs of the f i s h f r o m t h e 9 mm e n c l o s u r e ( t o p ) a n d t h e 19 mm e n c l o s u r e (bottom). Symbols: S = s m a l l p r e y (0.7-1.4 mm) M = medium p r e y ( 1 . 4 - 3 . 0 mm) L = l a r g e prey (3.0-10.0 mm)' X L = e x t r a l a r g e p r e y (>10 mm) |  j = pelagic =  prey.  nonpelagic  prey.  30  QUALITATIVE  DATA  Several enclosure through 19mm  qualitative  d i d not the  permit  mesh  mesh.  with  Large  the  Euphausia  were  to  freely were  through sampled  sampling  ease  the  get  However  the  same  19mm  from  their these  mesh.  the  9mm  suggest  difficulty  swimming  out  supported  by  following  the  daylight  hours  mm,  in  moved  body yet,  appendages Euphausia  mesh  -to  move  through  length) none  through  were  Nonetheless,  of  that the  adult  9mm  the  more  large  than  any  the were  of  these  5mm  observed  when  these and  data:  (1)  ten  large  (in  swimming Euphausia  of  fish  stomach  may  the  four  have  had  from  conclusion  meter  vertical  Euphausia  crustaceans are  (2)  in their  Euphausia  enclosure. This  the  contents  observation suggested  could the  patches  they  9mm  not 9mm  tows  during  normally  the  found  e n c l o s u r e had  than  those  is  in  more  i n the  19mm  ( F i g . 10).  Another  During  that  mesh;  enclosure captured  waters;  Euphausia  enclosure  3.0  the  9mm  surface  adult  the  locations. findings  the  that  zooplankton  enclosure  These  through  of  9mm  into  holes.  sizes  (20-25mm  swimming able  a l l  Euphausia  observed  diameter)  observations suggest  of  move  morning  unabated  sample  Epilabidocera  back  and  forth  taken  that, morning  meter  of  water.  through  that  through  taken  on  zooplankton both  9 mm  June  12,  a m p h i t r i t e s were a l l the  produced  over  9,000  and  observed  e n c l o s u r e s . One organisms  as  large  19  mm  as  mesh.  several  dense  moving  freely  of from  the one  samples cubic  31  I oo  ;  FREQUENCY  ) VOLUME  )  FREQUENCY  ; VOLUME  ao +  10 +  20 +  S  ti  L  ti  S  XL  L  XL  L  9 MM ENCLOSURE  Figure  10.  S  ti  L  13 MM ENCLOSURE  The r e l a t i v e the stomach salmon. [  XL  proportion contents  | = Calanus =  of each prey group in of the j u v e n i l e chinook  species  Calliopius  = Decapod  larvae  =  Euphausids  =  Parathemisto  XL  32  SUMMARY  OF  RESULTS  (1)  The any  19mm size  mesh d i d c l a s s of  not impede t h e e n t r a n c e o r e x i t of zooplankton found i n the samples.  (2)  Concentrations of a l l sizes of i n c l u d i n g adult Euphausia , i n s i d e the enclosure without fish were not d i f f e r e n t from c o n c e n t r a t i o n s measured enclosures.  (3)  Zooplankton concentrations measured i n s i d e the two enclosures with f i s h were significantly different from the c o n c e n t r a t i o n s measured o u t s i d e , f o r each size category.  (4)  J u v e n i l e c h i n o o k salmon were a b l e t o a c h i e v e maximal g r o w t h r a t e s w h i l e f e e d i n g on p e l a g i c z o o p l a n k t o n i n a semi-enclosed water column.  (5)  Food sources associated with the side of the enclosures were not a major contributor to the growth of the j u v e n i l e salmon i n e i t h e r e n c l o s u r e .  (6)  T h e 9mm mesh d i d impede adult Euphausia .  the  entrance  zooplankton, 19 mm mesh significantly outside the  and  exit  of  DISCUSSION  This of  the  this for  study  has  semi-open  apparatus  enclosure  does  pelagically  enclosures any  other  and  high  quality  demonstrated  not  apparatus  of  the  feasibility  experimental a  fish; pelagic  completely however,  the  methods  enclosed  used  to  sample  these  Clearly  environment experimental  more  closely  excellent  are  and  suitability  natural  The  fish  and  apparatus.  environment  previously developed.  r a t e s of  the  an  provide  feeding  approximate  growth  as  the  survival  testimony  handle  the  than  to  the  juvenile  salmon. The  major  drawback  to  the  19mm  enclosure  was  that  the  fish  33  cannot  pursue  probability reduced  of  to is  advantage  of  food  past  capturing  zero  drawback  Many  prey  as  these  studies  have  those  that  the  i n the  prey  if  one  of  column.  The  methodology  measured  prey  concentrations  feeding,  and  The  apparatus  potential the  for  and  of  methods to  growth  How r a p i d l y do s a l m o n year while feeding estuary?  (2)  Are hatchery feeders than  but  field  laboratory  reveal  the  errors  associated  results  to  natural  system.  size  and  major  measuring are  are an  where  similar  us  the  fish  the were  fish.  paper  questions  to  water  that  feeding this  the  seldom  open  assures  in  major  have  pertinent  to  are:  zooplankton  abundance?  various times pelagic zone  a  field  describes abundance  in  could  studies  experiments  described  prey  of  in  for'the  outlined  the  This  fish.  measure  from  is  enclosure.  Observers  study  taken  grow a t in the  has  two  this  related to  section  Part  they  success)  retain  feeding  experiments  questions  a  to  The  of of  the an  reared fish more or less efficient naturally reared juvenile fish?  laboratory  with  the  stocks.. P o s s i b i l i t i e s  (2)  conjunction  of  feeding.  resolve  enclosure.  importance  estimates  How  above  in  were  (1)  the  are  used  salmon  is fish  the  fish  growth  helping  enhancement  More to  provides  out  i.e. retaining  fish  the  the  (pursuit  wishes  concentrations  vicinity  of  item  moves  expressed the  prey  edge  prey  enclosures,  a v a i l a b l e where  certain  a  the  necessary  the  provide should  how the  fish  be  wherever  methodology with  partial  which  conducted possible.  could  extrapolating  growth  offshore  rates  answers  were  enclosures,  be  in This  used  to  laboratory  related and  to the  34  similarities relationships  and derived  differences from  tank  between experiments.  these  results  and  35  PART  Growth  The  and Feeding  importance  the  growth  has  been  acknowledged  Arthur  Lebrasseur  rate  the  extent  The  Production  related  results  of  to  maximum  survival  acquisition The provided  the  juvenile levels  a  (e.g.  studies  study  natural  Hjort  stages  of  were  larval  review  of  fish.  the  enclosures  a  to  natural  Georgia,  largely  at  resources  part  determining  of v a r i o u s  Hyatt  literature  species  of  of the area.  especially  with  (1976)  presents  pertaining  to  the a  fishes'  environment.  developed  and t h e abundance  of the fish-food  1.965;  concentrations required for  to quantify the relationship  salmon  Wiborg  attempted in  of  incomplete,  i n the natural  experimental  food  fishes  1914;  have  relationship  life  available  and Degtereva  i n the Strait  prey  food  and j u v e n i l e  few s t u d i e s  to the planktonic  of food  data  reports  this  the early  this  respect  comprehensive  of l a r v a l  e t a l . 1 9 6 9 ) was a i m e d  t o which  were  Only  establish  (Lebrasseur  fish  i n many  Fish  of  1956; S h e l b o i i r n e 1957; S y s o e v a  quantitatively  III,  and s u r v i v a l  e t a l . 1969).  environment.  of a Planktivorous  of the q u a n t i t y and type  to  1948;  TWO  in  between  of n a t u r a l  relationship  have  this  been  study  have  t h e growth of  zooplankton. examined:  Three  36  (1)  The r e l a t i o n s h i p between f i s h s i z e and abundance of p e l a g i c  growth prey;  (2)  the relationship between q u a n t i t y of p r e y consumed;  (3)  the functional components of the relationship between t h e p r e y consumed and t h e abundance of t h o s e prey i n the water column.  fish and  rates  growth  and  rates  the  and  the  METHODS  Weekly  fish  corresponding  mean  enclosure. calculate consumed values  column.  of  of  Holling's  number  to  disc  to calculate the  the  9  prey  salmon.  I t was  successful  found  analytical  relationship  are described  that  by  used  i n the  and  in  These  the  used  proportions  prey  type).  to  examine two  Oaten  search  stomach  following  have  between  was  actually attacked  rates  methods  i n the  must  to  the water  to f i ta  data.  rates  of  each  rates.  abundance  density  in  fish  growth  1959)  the  constructed  the  (Murdock  assumed  or d i g e s t i o n  was  relationship  (Holling prey  against  measured  equation  same a s p r o p o r t i o n s  regurgitation The  categories  a  the prey  equation  relative  model  the observed  and  disc  plotted  of c a l o r i e s that  establish  consumed  multispecies  juvenile were  prey  energetics  to sustain  used  were  concentrations  to the consumption verses A  used  t h e minimum  were  rates  zooplankton  salmon  e a c h day  quantity  curve  A  growth  1975) for  contents i n the (no  the  of  was each the  stomach  differential  fish-food  sections.  37  Salmon  Energeties  The  physiological  components partition energy  of the  loss  energy  and  and  estimates  to  to  be  in  the  rates  of  by  so  and  o t h e r s have  into  salmon  that  for  measured  growth  who  This  were  similar  in.  from  arrive and  at  Dickie  approaches  salmon  i s assumed  i s supported  feeding  to  this  rates.  assumption  reported  swimming  estimated  similar  f o r sockeye  salmon.  (1969)  energy  Paloheimo  used  potential  categories:  finally  (1961a),  values  for standard  was  to  major  energy  were  as  five  These  following  Growth  Ivlev  to chinook  Brett  the  fish.  metabolism,  metabolic data  Elliot  a  components  literature  sizes  model  for chinook  sockeye  other  ration  applicable  into  f o r growth.  (1977)  of  n i t r o g e n o u s wastes,  consumption.  this  work  budget  for feeding  energy  Laurence  translate In  and  i n the  of  e s t i m a t e s v a l u e s f o r the  consumed  the  relationships  model  energy  energy  metabolism, study,  the  in feces  metabolism,,  (1966),  Model  metabolic  those measures  for  (1976).  Excretion  Brett literature  and on  They  suggest  their  food  feces  Groves  the  that  energy  and  rates  (1979)  of  fish  energy  feeding  i n wastes.  nitrogenous  combinations  of  significant  effects  loss on  This wastes  temperature of  have  and  thoughly through  examined  excretion  invertebrates  value  takes  and  temperature  into  would  ration. and  lose  Elliot body  for  (1976) weight  "Er".  25-30%  account  apply  the  on  of  both most found fecal  38  energy  loss.  found  in  these  However,  this  effects  for  temperature  effects  described  the  were  temperature not  on  than  5%.  water  temperatures  Standard  and  sufficient  body  to  weight  necessitate  (1965) to  are  standard  very  included reason.  was  output was  little were  A  of  the  between  10  within  any  model  compared  of  the  including  with  two  expected  always  in  the  models  because  model  differed metabolic  and  15°C  and  this  range.  the  Metabolism  Brett metabolism  The  This  change  column  not  metabolism  in this' section.  less  effects  were  following  expenditures  describes  fish minor,  size the  several  and  equations  temperature.  relating Since  following  e q u a t i o n was  =  0.078*Log(W)  used  standard  temperature to  calculate  metabolism:  Log(Mb)  for  of  adjustments.  equations  where  ranges  experiment  Temperature  by  the  "W"  i s the  wet  -0.63  weight  standard metabolism  of  "Mb"  +  the  are  fish  i n grams  milligrams  of  and  oxygen  the per  units hour.  Feeding.Metabolism  Brett metabolism  (1976) "Mf"  described  i n terms  of  the  ration  following size:  equation  for  feeding  39  Mf  where the  "R"  d r y body  milligrams  weight.  which  could  same  "W"  =  i s the f i s h ' s  metabolism are  per hour.  to  calculate  by a f i s h ,  the  depending  maximum  on i t s s i z e  14.5 -  5.l5*Log(W)  wet w e i g h t  i n grams  a n d "Rmax"  has  the  u n i t s a s "R".  Metabolism  Swimming calculated  metabolism  i f one knows  (Brett,  "V"  swimming  i s  the average  =  activity  daily  ( 1.85 + 0 . 2 7 * V  measured  metabolism  m e t a b o l i sm.  or routine  metabolism  swimming  speed  c a n be of  the  1964).  Log(Ms)  where  of  1971).  Swimming  fish  as a percent  f o r feeding  of f i s h  was u s e d  be c o n s u m e d  Rmax  where  The u n i t s  consumed  Ration  following equation  (Brett,  ) - Mb  of the food  of oxygen p e r k i l o g r a m  Maximum  ration  ( 92 + 3 6 . 6 * R  i s the d r y weight  fish's  The  =  "Ms"  in  fish  has  ) -  body  the  same  Log(Mb)  lengths units  per second and as  feeding  40  ' estimate  An used  because  estimate  and  fish.  weight  estimate  of  .  . . swimming  model  was  to  speed  was  provide  an  c a l o r i e s consumed would  require  efficiencies  of  day.  speed  -0.9%/day.  and  (2)  the  nonfeeding  rates In  1  of This  fish  to  by  more  support  Hyatt of  1-2  the  water  (1976)  body  for  achieve  the food  the  per  same  pelagic  feeding  Therefore,  estimate  of  the The  relationship  (1978)  one  minimum  body  length  swimming  equation  C  -  speed  ( R/Rmax  for  the  one  a  rate  stress fish  speed  at  and  speeds  zooplankton  optimal body  second  ration  )  at  starved  body  average  in  search  describes and  an  weight  a  from  percent  with  or  ration.  that  per  feeding.  expended  foraging  about  with  -0.9  kokanee  suggests  average  =  when  is  swimming  V  and  fish  following  between  maximum  stress  obtained  lose  for  into  with  fish  energy  greatest  trout  second  Ware  that  be  fish,  second  divided  was  starved  per  their  that  column.  second.  feeding.  would  found  starved  assumes  is  associated  activity  model,  length  model  lengths  the  speed  associated  swimming  of  the  body  that  swimming  swimming  nonfeeding.activity for  daily  (1)  growth  per  swimming  speed  daily  the  speeds  search  average  activity  negative  least  of  number  swimming  higher  components:  An  or  even  average  function  minimum  Higher  minimum  nonfeeding  of  minimum  rate.  The two  the  primary  the  suggest  growth  the  the  of  juvenile  1  of  foraging  length  is a  size:  per  reasonable  associated a  in  with  conservative  41  where are  "C" i s 1.5  body  as described  design which  above.  of t h e model must  Growth  The energy  have  This  ingested  after  G  transformed  into  consumed  t h e same  units  used  oxygen  and Groves,  1979).  growth  each  the value week  values  weeks  those  have they The  above  the  calories  of the food  model  this  i s  The c a l o r i e s  during  number  an a v e r a g e  can  be  equation per  of  to of  food  ration  in  used f o r  size.  growth  and  In the  consumed estimates  The r e s u l t i n g  each  of  consumed  calories  of c a l o r i e s day  per l i t e r  metabolism,  t h e weekly fish.  had t o  d a y ) . The  up c a l o r i e s  feeding  number  i n the offshore  model  adding  both  until  variables are  kilocalories  by t h e e n c l o s e d  t h e minimum  held  and the other  proportional  adjusted  achieved  consumed were  because are  was  represent  remains  (kilocalories  by  f o r the average  "F"  In  was 4.8  calculated  metabolism  equalled  must  be  and metabolism,  swimming model,  not  i s what  A l l v a r i a b l e s i n t h e above  equivalent  could  of  eguation:  oxycalorific  "F"  number  = F - F*Er - Mb - Mf - Ms  earlier.  (Brett  "Rmax"  by t h e f i s h ) .  catabolism.  i s the calories  be  and  i s consistent with the  t h e minimum  f o r growth  by t h e f o l l o w i n g  described  a n d "RTN"  Consumed  available  as  relationship  consumed  energy  "F"  per second,  ( t oestimate  been  and Food  represented  where  lengths  which of  six  the fish the s i x  enclosures.  translated  into  gross  growth  42  e f f i c i e n c i e s o f approximately  19%  f o r small r a t i o n s and  37%  for  l a r g e r a t i o n s . B i e t t e and Geen (1980) estimate the maximum g r o s s e f f i c i e n c y of food c o n v e r s i o n i n u n d e r y e a r l i n g sockeye be  18%  and  30%  for  small  and  large  rations  respectively.  T h e r e f o r e , the model probably c a l c u l a t e s the minimum food energy  necessary  salmon t o  amount  of  to s u s t a i n a given growth r a t e .  M u l t i s p e c i e s D i s c Equation The  Holling  m u l t i s p e c i e s d i s c equation was  nine prey groups found  i n the stomach contents of  fitted the  f o r the juvenile  f ish:  E(Ni) = - - - — 1 + .where  "E(Ni)"  is  the  p r e d a t o r d u r i n g time category  Ai  eaten  . of  *  Ni  the i t h prey by each  " N i " i s the d e n s i t y of each parameters  e q u a t i o n a r e : " T T " the t o t a l time  the  predator  each  water  and  THi  The  to  the  ^2 *  amount  "TT",  * TT * Ni — — —  column.  exposed  in  Ai  other  each day;  p r e d a t o r , h a n d l i n g each prey of  item; and  i n the above and  "THi" the time  prey  prey  spent, by  " A i " the p r e d a t o r ' s  are the rate  s u c c e s s f u l search. The  amount  extrapolated  from  eaten stomach  "E(Ni)  n  content  during data  equat i o n :  TT E(Ni) =  Tbs  * SCi  an using  entire the  day  was  following  43  where  "SCi"  was  the  mean number of the i t h prey found i n the  stomach c o n t e n t s of 10 f i s h , "Tbs" hours  before  above. The  the  to  purpose  the  "TT"  above  was  daylight  as d e s c r i b e d  relation  I 9 h r s and  their  stomach  salmon h e l d i n 10°C  and  fish  contents.  Nonetheless,  the  (1970)  15°C  11hrs, r e s p e c t i v e l y , t o a c h i e v e 90%  water  digestion  above  relation  t h a t the e n c l o s e d salmon f e e d a t a c o n s t a n t r a t e d u r i n g  the d a y l i g h t h o u r s . T h e r e f o r e , t h i s r e l a t i o n would amount  eaten  by  fish  overestimate  t h a t consume l e s s food d u r i n g each  a d d i t i o n a l d a y l i g h t hour. T h i s f e e d i n g p a t t e r n would be  expected  f i s h t h a t a c h i e v e t h e i r maximum r a t i o n . However, the average  f i s h e s ' stomach was  less  than  half  full  and  d a y l i g h t hours b e f o r e the f i s h were sampled was and  to  greater  the d i s t i n g u i s h a b l e stomach c o n t e n t s . B r e t t and H i g g s  assumes  for  was  17 hours b e f o r e the f i s h were sampled, would not c o n t r i b u t e  require  the  of  r e l a t i o n assumes t h a t the f o o d e a t e n ,  found t h a t j u v e n i l e sockeye  of  for  number  the stomach c o n t e n t d a t a f o r the time when the  were sampled. The than  the  f i s h were sampled, and  primary  standardize  was  12  hours.  Parker  and  Vanstone  the  number  of  always between 6  (1966) showed t h a t young  salmon had a d i u r n a l c y c l e of f e e d i n g i n t e n s i t y and t h a t f e e d i n g was the  continuous during d a y l i g h t hours. above  relation  Under  day.  The d e n s i t y of each p r e y i t e m " N i " was samples  conditions,  would p r o v i d e a r e a s o n a b l e e s t i m a t e of the  amount eaten d u r i n g an e n t i r e  zooplankton  these  derived  from  o b t a i n e d o u t s i d e the e n c l o s u r e s . Data  samples o b t a i n e d i n s i d e the e n c l o s u r e s was  daily from  of l i t t l e v a l u e s i n c e  44  it  often  stomach  d i d not include several contents.  reduced  the  species)  inside  Baxter 10"  It is'probable  number  general  (1970)  lower  primarily  exposed  and  late  dusk;  The  time  function (1981)  of zooplankton  suggested  that  the  fish  (especially  a  corresponding  threshold  visual  are  that  groups  the enclosures, as suggested  meter-candles,  1  of the prey  for  predators,  " T T " was  equal  each  may  visible  One. of  about  be u s e d  feeders. Since time  17 h o u r s  of the f i s h  has demonstrated  visual  t h e more  i n Part  dusk,  i n the  significantly  intensity  between  as a  salmon a r e  the predator  to the i n t e r v a l  handling  of the size  to late  the t o t a l  approximately spent  light  found  and prey  early  dawn  i n June.  prey  item  "THi"  and t h e s i z e  the emperical  base  i s probably  of the prey. for  the  a  Gazey  following  relationship:  TT  b =  a * W  THi  where  "a"  fish.  The l e f t  number "TT".  and  of  hand  each  side  prey  by  which  reasonable  estimate  consumed  by  equation  was  "a"  assuming  and  respectively.  a  "b"  i s the weight  represents  c a n be c o n s u m e d  that  the  o f t h e maximum  juvenile  fitted  a n d "W"  of the equation  E s t i m a t i o n of the parameters  possible  the  "b" a r e p a r a m e t e r s  salmon  in  amount  in less  i n the time  this  maximum  equation stomach  of prey  than  data  parameters  estimated  The stomach  from  c a p a c i t y was d i v i d e d  maximum interval  was  made  capacity i s a which  17 h o u r s .  to physiological were  the  of the  Brett  can  be  The above  (1971)  and  a s 0 . 1 5 5 a n d 0.77 by  the  size  of  45  the  prey  "Pi"  to  determine  prey  which  could  be  consumed  following a  equation  f u n c t i o n of  prey  the  number  of  a  juvenile  salmon  d e s c r i b e s the  handling  time  size  by  maximum  and  fish  THi  =  each  each  size  day.  for each  of The  prey  as  size:  TT  *  Pi b  a*W  where  a l l the The  variables  rate  estimated  of  using  and  parameters  successful search several nonlinear  resulting  values  should  be  successful  search  because  the  estimated  from  the  absolute  mean  fish  number  stomach  indication  matrices assess  the  consume for  the  degree  contrast  RESULTS  AND  shows  the  contents  10  for  that  of  parametization  of  was  techniques.  The  rates  eaten  estimates  each  day.  However,  provide prey  covariance  in estimates  of  "E(Ni)",  good  each  prey  group  relative  successful search  among  prey  earlier.  not  probably  The  confounding  in densities  are  consumed  numbers  of  as  f o r amount  data,  fish  day.  rates  " A i " for each  values  prey  described  a  of the  reasonable  that  an  average  and  correlation  were  examined  due  to  to  lack  of  the  sizes  and  groups.  INTERPRETATION  Stomach of  each  as  considered  content  relative  these  natural  types  of  contents of  would  stomach  are  contents  zooplankton relative of  fish  were  reexamined  consumed  importance  from  each  of  by  the  to  determine  juvenile  salmon.  each  size  group  enclosure.  With  the  i n the  exception  Figure  9  stomach of  June  46  15  the  contents and  small  size  of  fish  the  Craddock  juvenile  et  chinook  class from  a l .  is  either  (1976)  salmon  not  prefer  represented  enclosure.  the  stomach  Engstrom-Heg  (1968)  also  found  that  food  items  larger  in  naturally than  feeding  1.4  mm  in  length. Figure types  10  i n each  shows size  the  category  were  c o n s i s t e n t l y the  yet  they  the  dominated  zooplankton  Fish  Growth  The that  vs  data  fish  available figures  (Table  2).  during  is  the  mean  growth  rate  the  fitted  curve  crosses  similar  growth  to  between  rates,  while  relationships.  Figure  strongly large  size  of  related classes  the  14  to than  zero  other  suggests  to  contents  classes  of  of  any  line  fitted  figures  single  size  points  The  fish  small  that  the  suggests  size  where  represents  using  of  category.  a  saturation  11  rates  the  achieve  a  indicate  concentration  mean  represents  shows  zooplankton  growth  the  these  the  point  cannot  Figure  of  in  y-intercept  fish.  the  were  combined  by data  equation.  abundance  the  size  prey  species  experiment  growth  which  curves  the  stomach  plotted against  the  starved  the  disc  The  rates  week,  the  below  a  various  Calanus  large  "in situ"  growth  negative  The  the  determined  for each  concentration  of  and  ( F i g . 11-14).  the  ration.  the  largely  organisms  the  Abundance  abundance  relationship  component  samples  Zooplankton  of  enclosures.  medium,  zooplankton  function  both  small,  represent  maintanence  proportion  the  growth  zooplankton  for  smallest  gathered  food  relative  and  no fish  significant are medium  more and  •  9mm enclosure  O 19mm enclosure  5  2  o  c5 ' Maintenance o  100  200  300  400  Small Zooplankton  Figure  500  600  700  800  900  (organisms/m**)  11. T h e r e l a t i o n s h i p s between f i s h the abundance of a small zooplankton.  •  growth rates (0.7-1.4  and mm)  9 mm enclosure  O 19 mm enclosure  o  \P— 10  Figure  20  30  40 50 Medium Zooplankton  12. T h e r e l a t i o n s h i p s the abundance zooplankton.  between of a  I99  (organisms/m^)  f i s h growth rates medium (1.4-3.0  and mm)  •  Figure  Figure  13.  14.  The the  The the mm)  9 mm  enclosure  r e l a t i o n s h i p s between f i s h a b u n d a n c e o f a l a r g e (>3.0  growth r a t e s and mm) zooplankton.  r e l a t i o n s h i p s between a b u n d a n c e o f a medium zooplankton.  growth large  fish and  r a t e s and (1.4-4.5  49  the  Wankowski  (1979)  range  prey  He  found  a  minimum  (1979) food  that  large  in size  Functional  The food  the per  day  the  i n mean  percentage fish  response  1.4-4.5mm  zooplankton. f i t of  The  represents  a  (limit  of be  the  rate  zooplankton sampling 2.0m /hr 3  size  of  each  the  minimum  Figure  this  general  prey  single  3  rate  of  those  of the  disc  If  the  measured  successful  category.  the  response  4.0m /hr.  twice  for  density  species  functional of  was  depicts  represents  search  minimum  15  15  Holling  of  account  the  this  the  consumed to  of  increase  to  to  were  sustain  salmon  data  the  and  amount  weight  ration  in Figure  error),  salmon  length.  to  food  curve  successful  in  body  The  week.  of  optimum  y-coordinates  The  slope  on  medium  mm  the  maximum  the  an  4.5  percent  day.  the  Thorpe  rapidly  the  consumed  converts  concentrations  for  in  and  Fish  have  from  6 mm and  most  to  salmon.  juvenile Pacific  and  j u v e n i l e chinook  initial  actual  would  of  must  per of  grew  prey  mm  of  t r a n s l a t e s to  the  the  gap  Wankowski  estimated  model 14  mm.  This  1.4  model  consumed  functional  of  mouth  salmon  Planktivorous  in Figure  the  equation.  0.8  for  between  for  calories  squares  mm  Most  r a t e s . The  as  least  2.3  juvenile fish  a  of  limitations  juvenile Atlantic  maximum  length.  energetics  expressed change  to  were  Response  shown  to  a  spacing  enclosures.  growth  data  have  fork  mm  classes  energy  morphometric  juvenile Atlantic  1.7  salmon  observed  raker  the  a v a i l a b l e to  salmon  their  of the  sizes  cm  that  times  size  raised  10  gill  found  0.02  food  of  describes  search  50  Figure  15.  The functional response of salmon to the density zooplankton.  juvenile chinook of 1.4-4.5 mm  51  The  next  section  distinct  prey  groups  zooplankton  Relative  and  each  prey  to  prey  and  and  relative  quantify  of  successful prey  were  readily captured less  (Table. item  4).  within  than  the  in  equation  for  contents  (described  routines  rates  9  and  of  earlier)  (Patterson  successful  1978)  search  for  i n t e r r e l a t i o n s h i p s between  by  define density search  the  size  and  of  a  predator's  of  the  that  capacity  prey  d i s t i n g u i s h the  predator  inherent  search  prey  successful  more  group.  For  search  for  large  vs.  each  of  these  size  and  for  opaque  transparent  successful  lowest  rates  higher  Parathemisto  eyes  the  successful  fish  each  calculated  dark  of  the  The  Within  larvae,  stomach  search  from  those  to  is  low.  prey  that  that  were  frequently.  with  successful  were  of  relative  directly  the  search  where  rates  The  disc  optimization  Relative  captured  the  successful  groups.  capture  most  of  Search  multispecies  calculate  group  Rates  in  Successful  nonlinear  used  various  find  of  Holling  several  were  found  rates  samples.  Rates  The  compares  each  size  effectively example, medium  prey.  and  are  bodies  common  to  item  for  the  larger  food  small  the  rates  decapod search  Euphausia  ,  contrast  Calanus  species  rates  decapod  their  species.  of  larvae.  higher  Calanus  vary  prey  higher  for  to  the  C a l l i o p i u s with  much  calculated  category.  vs.  appear  of  compare  categories,  bodies  search  contrast  contrast  pac i f i c u s  search  large objects  The  rates  were  the  S  Calanus M L  ,0  .02  LOW  Parathemisto S M .23  1.50  10.0  .0  CONTRAST  Table  4.  Decapods M L  S  .11  HIGH  Euphausi ids L XL  .34  .31  CONTRAST  The juvenile salmons' s u c c e s s f u l s e a r c h f o r the the e n c l o s u r e s .  relative v a r i o u s prey  1  1  2  .52  1  3  .05  .04  1  4  .03  .05  .00  1  5  .02  .09  -.00  -.01  1  6  .09  . 1 6  .00  .00  -.01  1  7  . 1 4  . 1 4  -.01  -.00  -.01  .00  1  8  . 1 4  .22  .01  -.01  -.02  -.02  -.02  9  .74  .60  .04  .27  .06  .01  .13  1 Para  2 Para  3 Deca  4 Cal  5 Deca  6 Cal  l  1  small  Table  5.  i 1 lI  medium  2.55  large  rates found  of in  1 .15  7 8 Amph Euph - I I  1I  X-  The c o r r e l a t i o n m a t r i x f o r t h e 9 p r e y g r o u p s f o r which rates of successful search were calculated. Values above .85 indicate significant correlation (p<.05).  53  The search, due  to  correlation quantifies  lack  of  None  of  This  analysis  data  to  in  the  the  groups  above  degree  were that  define  column  the  and  that  the  search  was  probably  Figure  15.  The  of  confounding  in densities  was  amount have  salmons'  this  the  3  i s as  groups.  (Table  contrast prey  prey  further  2.0m /hr  estimates  prey  the  each  minimum  support  successful  correlated  of  provided  than  among  between  eaten  of i n the  sufficient  relationship  greater  rates  significantly  enclosed  nature  these  of  there  the  analyses  contention  for  contrast  suggests  clearly  The  the  natural  prey  water  matrix  rate  in  category.  of  to  derived  (2)  F i g u r e 15 reflects the functional response for Calanus species more than other species because Calanus were consistently the most abundant o r g a n i s m s . However, the e n c l o s e d salmons' relative rates of effective search f o r C a l a n u s were lower than those f o r a l l other prey groups within each size class.  Search  The enclosed speed  rate fish  and  of  search  could  reactive  Juvenile  salmon  are  sight  locate  food  to  from  follows:  The c o r r e l a t i o n m a t r i x and the r e l a t i v e .rates of s u c c e s s f u l s e a r c h s u p p o r t the e x c l u s i o n of the s m a l l s i z e c l a s s from F i g u r e 15.  of  my  successful  (1)  Rates  the  density  support  value  5).  salmonid's  vision  search  represents per  distance primarily items.  is divided  unit to  time,  volume  Protasov two  of  considering  potential  pelagic  into  the  prey  predators (1970) visual  water  swimming  (Hyatt  that  fields:  1978).  depend  proposed the  an  upon  that  a  forward  54  field  used  field  warns  diagrams a  right  the  to  locate  the  depict angle  fish the  cone;  d i s t a n c e of  potential of  forward where  visibility  area  reactive  vision  distance.  reactive water,  of  distance the  prey.  Ware  trout  to  following  =  1.57  *  fish  effected  the  d e s c r i b e s the  the  roughy "AV"  backward  Protasov's the  shape  is related  of to  manner.  2  have  and  as  following  D  depends  the  size  reactive  and  fish  that  the  of  the  c o n t r a s t of  sizes  fitted  the  clarity  distances  various  curve  upon  established  by  the  c o n t r a s t t a r g e t s of  equation  while enemy.  vision  feeding  light  (1973) measured low  of  studies  is greatly of  field  i n the  for a  Many  amount  area  "D"  items  approaching  visual  the  AV  The  an  food  of  the  rainbow  ( F i g . 16).  t o Ware's  The  data:  .44 Dr  where  "Dr"  i s the  millimeters. Confer fish  and  studies ideal the  reactive  Data  Blades  attacking reactive  (1975) a  illumination.  *  in Hyatt suggest  variety  P  similar natural  d i s t a n c e s were  measured  to Ware  The  i n most  reactive natural  phytoplankton (1973)  suggests  "P"  (1976),  of  illumination.  due  16.34  d i s t a n c e and  found  e n c l o s u r e s , as  reduced  =  prey. in  waters, blooms  prey  Protasov  reactive  distances  that  i s the  size  in  (1970),  and  distances  for  In  a l l of  these  clear  water  with  for  fish  would and  reactive  feeding be  in  greatly  sub-optimal  distance  would  55  E  0  5 Target  Figure  16. T h e mean reactive rainbow trout to v a r i o u s s i z e s (Ware  10 Length  15 (mm)  distances ( d a t a ± 95%) low contrast targets 1973).  of of  56  be  cut  in  highly  half  by  probable  euphotic  zone  The average  doubling  that  are  2-3  those  equation  rate  for  attenuation  attenuation  times  following search  the  the  of  juvenile  be  It  coefficients  for  laboratory  water.  clear  could  coefficient.  used  salmon  to  estimate  feeding  the  of  in  is  the  natural  waters:  2 SR  where  "SR"  i s the  swimming and to  "Ra" that  model. rates 6).  attenuation  of  clear  Prey  foraging  length  range  apparant  per  i s the  prey  in  P  "V"  3  was  prey  visual for  feeding  speed  second,  speed of  estimate  pelagic  *  i n m /hr;  light  .88  *Ra)  i s the  size  predator's  in millimeters;  natural  water  relative  water.  swimming  the  (.1634  search  i s the  This  The  of  *  "P"  body  for  * v  i n cm/sec.;  reasonable for  rate  optimal  one  56.52  speed  in  The about  =  for as  described,  used  sizes  to  found  capabilities the  minimum  juvenile  pelagic in  the  calculate in  the  suggest  rate  feeding  is  energetics the  search  enclosures that  of  fish  (Table  2.0m /hr 3  successful  is  a  search  salmon.  Distribution  Prey temporal inside patches,  patchiness variation  the  i s one  in  the  enclosures  the  concentrations  fish of  rate were  could prey  of  than  the of  major  successful  clumped  have those  f a c t o r s which  been  search.  into highly feeding  estimated  from  in the  may  If  cause  the  prey  concentrated much  higher  zooplankton  57  Prey  Size  0.7 1.5 3.0 4.5 10.0 20.0  Table  6.  (mm)  Rate of Search (m /hr) maximum probable range 3  11 22 40 57 115 211  1.2-2.7 2.4-5.4 4.4 - 9.9 6.3 - 14.2 12.7-28.7 23.4-52.8  Search rates f o r the range of prey s i z e s found i n t h e e n c l o s u r e s . T h e maximum s e a r c h r a t e s w e r e derived from laboratory measurements. The probable range assumes that the reactive d i s t a n c e s f o r f i s h feeding i n the euphotic zone i s 0.3-0.5 o f t h e l a b o r a t o r y value.  58  samples. of  the  Such  rate  of  significant the of  rate the  the  of  functional  may  the  the  food  medium were  and  both If  still  the  in a  the  fish  prey  patch.  by  these  few  patch  the  Under  these  However, slope  were  in  highly  these  patches  conditions,  successful search  disperses  or  a  numbers  prey  find  obtain  initial  prey  to  of  overestimation  the  and  have  rate  i n an  ration  prey.  higher  before  expect  these  consistently outside  large  On  primarily  visual  In  moves  these  enclosures  other  hand,  inside  small  the  and  of  fact,  for  the  inorder out  of  rates  of  concentrations  concentrations  enclosures the day  enclosures  and  night  measured  contention  medium  fish,  enclosure  outside.  that  fish  samples  of  without  in each  with  of  concentrations  concentrations  zooplankton those  of  high  the  the  the  65%  the the  such  reduce  inside  45%  of  with  significantly  about  80%  consistent with  fish,  zooplankton  zooplankton  above  that  enclosures.  the  concentrations  frequently  could  large  respectively.  are  even  prey  search,  inside  measured  the  pursue  if  i s determined  when  would  only  ration  lowest.  fish  an  might  successful  and  the  result  enclosure. One  of  their  respone were  need  capture  of  successful search  successfully  salmon  would  successful search,  enclosures  and  distribution  portion  concentrated,  to  a  These  juvenile  and were  results  salmon  are  predators.  DISCUSSION  Many predator  experiments consumes  prey  have in  attempted relation  to to  determine their  whether  abundance.  a To  59  establish  this  concentrations -is  one  these  of  were  the  high  prey  are  more  prey  exposure  visual  Ware  accounted  f o r more  contrast  and per  may  or  a  less  than  the  salmons'  with  This  reduce  the  effort  lower  14  prey Ivlev  as  the  size  planktophages,  cues  was  Both  of  prey  affect  the  predation (1972)  of  prey  of  Cladocera  which  supported  size  hunt  importance  search  and  diet  a s s o c i a t e d with The  successful  contrast  Zaret's  importance  that  mostly  i n the  which  from  activity  size.  well  species.  aspects  conventional (1969)  prey  his  Parsons  tank  of  fish  by  the of the  for a l l prey  suspected  size  and  that  fish  suspicions that  and  reveal  feeding  experiments  for c a p t u r i n g prey  c o n c e n t r a t i o n s would (1961b),  low  body-size  pigmentation  prey  examined  between  prey  as  This  eyes.  required  confirmed  to  contrast  Lebrasseur  relationships  through  of  cue  r a t e s of  prey  variation  the  found  of  the  dark  has  bounds  studies.  of  high  large  section  the  degree  visual  relatively  organisms  outside  of  Zaret  consumed  that  The  (1965)  prey  feeding.  small,  elements,  support  important  tract  the  prey.  theory,  contrast.  types  situ"  this  digestive  these  any  of  of  that  e n c l o s u r e s . Data  the  found  are  Dobson  certain  salmon  d e n s i t y or  the  and  the  when  (1973)  prey  of  of  even  exposure  Brooks  be  visually, eye  prey  inherent se  than  be  p r e d a t o r s , were  juvenile  abundant.  inherent  modification  that  prey;  and  must  where  contrast  activity  of  one  advantages  revealed  predator,  hypothesis  measured  chief  enclosures  large,  a  relationship  and  growth.  larger  these  Lebrasseur  tank  that  and  most  l i e "in  experiments thereby  mask  Figures  11  enclosures  and  relationships. (1970)  and  others  60  have  found  measured rates  that in  in  high  nature,  tank  natural  have  to  are  The  of  the  for pelagic  patches.  These  water tank  feeding  column.  of  prey  a  put  i n the  low  are  predator tank,  decreases  as  experiments  and  the  or  describe  initial  provide  support  study.  Ware  prey  capture  recognition capture product rate  of  of  used  and  consume  slope  of  field  success  able  successful  in a  by  search.  Data  high rate.  i t is  high  not prey  growth  changing  suggested the  amount  these  in  would  growth  of  the  fish  in  amount of  these  effect  functional Ware  response of  prey prey  feeding of  prey  was was  the  and  W.E.  recognition  74% at  rate  from  response. Johnson  described  trout.  prey)  times  of  D.M.  rainbow  factors  fish to  (1)  the  prey  follow  search,  to  prey  c o n c e n t r a t i o n to a c c u r a t e l y  fishes'  success)  a  sustain  factors:  removed  prey  of  constantly  None  estimates  ( f o r moving  to  growth  these  that  concentrations  work  for  to  is limited  functional  (pursuit two  a  high  salmon  two  have  enough  a  demonstrate  feeds.  in tanks low  by  that  respect  successful  the  provided  success  these  were  r a t e s of  (2)  f o r the  (1972)  success  salmon  positive  theory,  sustain  juvenile  predator  exploitation  Laboratory  to  infrequently  patchiness  with  fish  confounded  can  conducted  the  enclosed  the their  opportunistically  The  experiments,  inorder  feeding  juvenile  to  are  sustain  contend  position  prey  r a t e s of  while  They  According  its  necessary  rates  to  r e p r e s e n t a t i v e of  maintain  growth  necessary  fish.  environment.  concentrations  c o n c e n t r a t i o n s , which  were  raised  concentrations the  prey  Ware ±  in  success  84%  of  search  Ware  1973  and  found  that  and  prey  15%  least  this  16%.  The  equal  the  ±  was  used  to  61  estimate feeding that  search on  the  rates  3.0mm p r e y  in  appropriate  of  4.4-9.9m /hr  the  euphotic  for  3  minimum  rate  of  zone.  juvenile  These  values  successful search  salmon suggest would  be  2.7m /hr. 3  Data between of  the  5.7  grams  by  salmon  in  data. for  of  sockeye  0.2  very  The  The the  of  response  low  juvenile and  grams  data  lakes  (122  to  are  very  of  date  a  prey. of  rate  species;  rather,  the  study  previous proposed  for  a  specific  studies  appears  functional  of  In  to  the  have lower  the  the  the  1.2  and  abundance  plotted  growth  curve  not  lakes  between  been  the  abundance  these  1961  rates  fitted  include  to  estimate  component  f u n c t i o n of did  not  class  support  response  the  to  on for my  observations  minimum  of  prey  for  a  predator's  a  functional  size,  search  a  this  of  attempt  successful  proposes  to  and  on  did  this  study  size  relationship  depending  attempted  complex  values  grow  a  zooplankton.  because  This  to  data  of  have  absolute  factor  close  Johnson's  probably  camouflage  Johnson  representing  successful search is  days),  salmon Lakes.  i n mid-June  concentrations  studies  describes  Nilkitkwa  from  points  Unfortunately,  Few rate  1961  mid-October  zooplankton. 14.  i n Johnson  in Babine  weighing  Figure  and  growth  zooplankton  sockeye  of  presented  to  organisms.  pelagic  estimate  f o r each  value  minimum  mobility,  value  feeding  prey  for  this  Data  from  and  the  juvenile  salmon. A  major  conventional of  the  problem methods  fish.  In  in  used this  fish to  feeding  obtain  study  growth  growth  experiments  is  data  handling  rates  require  were  estimated  that  from  62  weekly  samples  abundance  data  experimental to  estimation  would  may  provide  disruption Part the  a of  enclosed  daily  otolith  growth  reduce  means fish  fish  of  the  on  handling;  a  daily  daily  such  fish  rate.  the  for measuring  short  ability The  otoliths daily  of  data.  feeding.  fishes'  however,  basis.  estimates  abundance  over  i t s growth  increments  three  food  disturbance  altering  on  provide  daily  significantly  growth  minimize  obtained  fish  frequent  to  would  the  of  artifically daily  was  design  accompany  require  in order  growth  ideal  fish  growth  Conventional  These  recent of  The  intervals  to  food  would  disturbances  feed,  thereby,  discovery  of  juvenile  salmonids  without  frequent  feeding. examines and  growth  the  growth  investigates  increments  and  patterns the  daily  on  the  otolith  relationship zooplankton  of  between  abundance.  63  PART  Growth  Patterns  Recent  studies  rings  on t h e O t o l i t h s o f t h e E n c l o s e d  have  i n the o t o l i t h s  Brothers  et  THREE  revealed  of  many  the existence  fish  a l . 1976; S t r u s a k e r  and Uchiyama  Coble  1977; Barkman  1978; a n d W i l s o n  study  has attempted  to relate  daily  changes  describes growth  in  methods  patterns  these  environmental  pertinent  to  on t h e o t o l i t h s  species  of d a i l y  growth  (Pannella  1971;  1976; T a u b e r t  and L a r k i n daily  Fish  1980).  growth  As  the  analysis  yet'no  increments  f a c t o r s . The f o l l o w i n g of  the  and  to  section various  of the j u v e n i l e chinook  salmon.  METHODS  On  5 May  transported Island.  1980 a p p r o x i m t e l y from  There  they  when  220  until  29 J u n e .  until  they The  The  Capilano  were  were  removed The r e s t  were  Hatchery  retained  on 5  from  the holding  enclosed  fish  were  A  small  random  to Patricia  in a holding  of the f i s h  sacrificed  f o r 24 h o u r s  j u v e n i l e chinook  t o be r e a r e d  fish  water  700  fixed  tank  were  Vancouver  until  19  May  enclosures  i n the holding  tank  June. tank  were  preserved  in formalin  and p r e s e r v e d sample  Bay on  i n the offshore  remained  salmon  o f 20  then  by  rinsed  freezing. with  fresh  i n 95% a l c o h o l . fish  from  the  e n c l o s u r e s , . and  64  10 The  fish  sacrificed  sagittae  Brothers and  at  were  Dr.  labelled  5 June  removed  were  from  used  each  using  Brothers  the  rings  representative Using  of  a of  pictures.  Primary  increments  on  each  daily  each  the  emphasis down  was  otolith sent  described  that  analysis.  to Dr.  Edward  were  ground  otoliths  in Brothers  clearest otolith  et a l .  pictures  and  were,  in his  opinion,  stage  micrometer,  rings.  microscope growth  and  the  photograph  growth  day's  laid  methods  selected  stereo  thickness  the  f o r the  fish  C o r n e l l U n i v e r s i t y . There  photographed  (1976).  on  and  a  increment  was  placed  measuring  daily  were  the  when . t h e  on  fish  measured  in  from  the these  growth offshore  enclosures.  Measur i n q D a i l y  It  is  measuring tenuous  Increments  clear  daily  from growth  process.  Some  of  most  of  the  increments the  otolith  can  be  difficulties  a  pictures  difficult  experienced  that  and are  often listed  below: (1) Where  does  one  growth  ring  stop  and  the  next  start?  ( 2 ) What p a r t o f t h e d a i l y m a r k r e p r e s e n t s t r u e growth; the t h i c k n e s s of the dark s e c t i o n ; the t h i c k n e s s of the l i g h t s e c t i o n ; or t h e i r combined thickness? (3)  How.can rings?  Since the  there  following  center rings,  of  one  d i s t i n g u i s h between  are  no  approach  was  the  labelled  darkest as  such  clear  by  answers  followed. portion Dr.  daily  of  to  The  the  adjacent  was  sub-daily  above  distance  two  Brothers,  and  questions,  between daily  measured.  the  growth  65  In  certain  distinguish the  growth  (see  any  were  areas  of  each change  graphs  in other  the  otolith, in  i t , was  ring  considered to  of  measured  approximation  of  clear  rings  flat  thickness  areas  be  spacing. the  i n F i g . 17). p a r t s of  magnitude  of  the  impossible  the  In  same The  change  these  areas,  distance  apart  relative  otolith  to  increment  depict  in ring  a  rough  spacing.  RESULTS  Daily  Growth  Of were  Rings  the  fish  examined  been  laid  on  these  fish  Dr.  these  on  were  moved  on  20  dates  199  days.  ring  patterns  Growth  Photographs from  19  of  the  otolith  by  chemical  from  Wilson  i n the  of  May laid  fixer.  5 June  growth  prior  able  count  their  to  and  to  The  Larkin  to  the  of  which  start  Hatchery  interval  chinook  several had  of  approximately  Capilano  (1980)  1980,  rings  incubation trays  1979.  to  also  197  records,  the  between  the  rearing  these  observed  two  daily  salmon.  Sagittae  sagittae  to  of  on  otoliths  sagittae  the  number  According  November  P a t t e r n s on  record  was  otoliths.  sacrificed  the  their  Brothers  troughs is  were  determine  down  experiment. rings  to  that  14  June.  down Even  from  from a  In 15  short  six  a l l of June  to  exposure  fish these 29 to  had fish,  June  had  a  continuous the  portion  been  buffered  eroded  formalin  66  i— -° 3  I—  3  -°  cr I I I 1I I I I I I I I I  I  19 20 21 22 23 24 25 26 27 26 29 30 31 MAT  II I  I  I I I 2 3 4 5  ! i I I : I I  I  I  I I I I I I I I I I I I I I I I I I I 10 I 11 I 12 13 14  192021 22 2324 2S 26 27 26 29 30 31 1 2 3 4 : 6 7 6 9 MAT JUNE  6 7 6 9 10 11 i2 13 14 JUNE  r  _  5.0. i—  I I I I l l  I I I I I I  I I  I I I i I 1I  19 20 21 22 23 2 4 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 MAY JUNE  £  I  s  -°  i I : i i  I I I I I I I I I I I I I I I I I I I I | | | | | | |  192O21 22232425262726293031 I 2 3 4 5 6 7 6 9 10 I I 12 13 14 MAT JUNE  1011 12 13 14  7.0  I— » • » .  I- -°. S  I I I I I I I I I I I I I I I I I I  192021 22 23242S2627 2829 30 31 I MAT  Figure  7 8 9 10 II 12 13 14 JUNE  ! ! J  ii i  i  i i I.I M  192021 22 2324 25 26 27 28293031 I MAT  i i  17. T h e p a t t e r n of d a i l y growth increments from the s a g i t t a e of s i x f i s h raised experimental enclosures.  i  5  i i  C  i i i i i-1 i  7 6 9 10 I I 12 13 14 JUNE  derived in the  67  will  destroy Figure  otoliths with  some p a r t 17  of  offshore the  shows  these  respect  to  experimental  of  the  zooplankton Most  "D"  growth  medium  of  the  which  in  with  top  12  7  i s the  data,  data  from  the  represents derived  data  zooplankton  the  analysed  meters -  from  were  data  zooplankton  either  and  daily  of  the  from  are  the  measured  outside  correlation  matrix  temperature  other  is  data,  i s the  with  two  and  following  that  highly  exception  with  the  being  i t s peers. are  are  not  The  highly  temperature  correlated  fish  a  data  data,  with  the  significantly  function . including may  A  more  accurately  multiple  both  predict  regression  was  relation:  c*RTN*TEMP  daily  the  are  set.  increments.  =  that  (A4,A10,B8)  similarly  remaining  zooplankton  the  fish,  correlated  (p<.0l)  data  patterns  fish  suggest  growth  using  growth  (D)  The  results  "OGI"  patterns  zooplankton  large  three  fish  OGI  where  obtained  temperature  Table  have  those  data.  temperature  conducted  and  correlated  zooplankton  otolith  The  i s only^moderately  one  These  The  increment  fish  patterns  correlated  growth  i n the  enclosures.  with  only  patterns  and  ( F i g . 18).  growth  significantly while  These  record.  data.  correlated fish  fish.  records. of  fish  growth  temperature  bathithermograph  the  otolith  temperature  water  concentration  the  the  six  enclosures  mean  of  otolith  +  d*TEMP  growth  +  e  increment;  "RTN"  is  the  68  19 20 21  22  23 24 25 26 27 28 2 9 30 31 I 2 3 4 5 6 7 8 9 10 II 12 13 l« MRY JUNE  i— »•».  13 23 2] 22 23 24 23 26 2 7 2 6 29 30 3! I 2 3 4 S I 7 8 9 10 II 12 13 |4 MRY JUNE  MCDIUn AND Lfi^CE lOCPLfilJiUO*  I  I I I I I I I I I I I I I I I 192021 2223242520 2 7 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 MAY JUNE  Figure  18. C o m p a r i s o n o f t h e mean g r o w t h i n c r e m e n t s w i t h water temperature and zooplankton abundance data.  69  A2  1  A4  .27  1  A5  .32  . 56  1  A1 0  .49  .49  .88  1  B8  .45  .57  .59  .64  1  . 16  .51  .43  .33  . 17  Zoo  .30  .24  .01  -.01  -.01  .72  Temp  .33  .35  .65  .76  .74  -.03  A2  A4  A5  A1 0  B8  D  enclosed  Table  7.  fish  1  D  1 -.23  Zoo  data  The correlation matrix for the d a i l y growth increments of six fish (A2,A4,A5,A10,B8,D); temperature d a t a (Temp); z o o p l a n k t o n d a t a (Zoo); and a c o m b i n a t i o n of t e m p e r a t u r e and z o o p l a n k t o n data (T & Z ) . V a l u e s a b o v e .44 a r e s i g n i f i c a n t (p<.05) and values above .56 are highly significant (p<.0l).  70  percent  o f t h e maximum  concentration, 15;  and  meters,  is  above  model  growth  was  related  close  to  their  record.  consumed food  minus  metabolic  water  are  shown  temperature  coefficients  was b a s e d  maximum Fish  in  Figure  i n t h e t o p 12  estimated  ration  metabolic since  since  (Brett  1971).  squares  temperature  the  daily  otolith  be  responsible  coefficient zero  temperature  by  the  for  only  bulk  of  the  increases  data  to the with  revealed  14% o f t h e v a r i a n c e i n  low  coefficient  " c " was' n o t s i g n i f i c a n t l y  represents  represents  appears  to  variance.  The  probability  of  the explained very  food  related  and temperature  "d" has a  while  also  in the  was  term  term  explain  achieved  earlier,  of a l l the o t o l i t h  increment;  the  (p<.000l)  "TEMP"  otolith  depicted  was d i r e c t l y  metabolism  and r a t i o n growth  t h e weeks  ration  that  fish  T h e "RTN*TEMP"  The  regression  the  described  losses.  of temperature  term  as  1971).  and that  during  maximum  losses,  least  on t h e a s s u m p t i o n s  growth,  growth,  (Brett  temperature  being  mean  to fish  consumed,  temperature  that  the r e l a t i o n s h i p  zooplankton  regression.  The  A  the  " c " , "d", and "e"  otolith  achieved at a specific  estimated using  "TEMP"  multiple  the  ration  of  the r a t i o n -  different  from  zero.  DISCUSSION  These research  results on  are  salmonid  that  temperature  the  development  not  surprising  otoliths.  Several  i s one o f t h e most of  growth  rings  in  authors  important in fish  light  of  have  factors  otoliths  recent  suggested affecting  (eg. Taubert  71  and  Coble  Figure  1977;  19  provide  These of The  first  fish  were  the  rings  removed  otoliths  growth  water  usually The  the  are  than  the  tank  19,  daily  the  day  fish  or  the point 27.  i n the fish  several  recorded a day  in  examined.  days  before  growth  rings  1 would  represent  On  April  anamalous  change  spacing  in  the. on  27,  the  °C  rise  0.7  temperature  is  °C. labelled growth  to  on  rings  Figure  19  laid  down  significantly  about were  6.8 14  °C °C.  f e d an  indicates while  farther  growth.  temperature.  around  was  changes  If  marks,  26  to  hatchery  was  tank  The  are  of  hatchery  Figure  The  attributable  holding  hatchery.  shown  relationship.  in every  occurred  for April  point  representative  the  1)  photographs  abrupt  consistent  in fact  0.2  growth.  holding  largely  the  The  for this  two  Capilano Hatchery  second  hatchery in  from  temperature. less  were  (point  increment at  support  depict  which  anamoly  operators in  further  photographs  otolith  these  B r o t h e r s pers.comm.).  Again The  while  the  fish  is  the of  of  were those  probably  temperature  water  ration  end  than  this  Throughout  excess  the  apart  water  the  in  temperature period  in  shown  Oregon  in  moist  pellets. The growth than  above  increments they  however, (Fig.  18)  reflect  reflect  the  significant rings.  analyses  mean  suggest and  These  day  relative that  food  observations  changes to  consistent  high  and  day  in  suggest  temperature  variation  growth  more  in  food  increments  for  extremes  in  food  effect  on  the  c o n c e n t r a t i o n s , which  that  closely  abundance; six  abundance spacing probably  daily  fish  have  of  a  growth  translate  72  Figure  19.  Sample photographs of h a t c h e r y and tank r e a r e d  the sagittae fish.  from  74  into  high  short  ration,  period This  of  a  study  pelagic  column.  However,  otolith  growth  It  any  in  be  has  kept  an  otolith  the  results  been  the d a i l y To  be  and  this  established.  food  for  that  is  of  only  abundance a  only  very  water  and  a  was  between  to  otolith  growth  have  to  relationship rings.  clear  the d a i l y  this  mask  abundance.  closer  knowledge,  small  completely  food  is a  water  inconclusive.  sensitive  any  i f there  growth  i n the  temperature would  the o t o l i t h and  author's  the  relationship  p a r t i a l l y or  to e s t a b l i s h and  between  abundance  o t o l i t h growth  useful  growth  food  to e s t a b l i s h  abundance  would  and  w h i c h may  indicate  inorder  food  fish.  o t o l i t h growth  relationship  growth  temperature  relationship between  attempt  between  a  fish  increments  constant  between  quantified  feeding  relationship These  affect  time.  appears that  changes  \~  of  apparently  This  connection growth  connection  has  of not  75  SUMMARY  Mesh growth  enclosures  and  results  feeding  surrounding capable  of  water and  second  column  within  each  enclosed  directly  than  1.5mm  response between  related  1.5  successful 2.0m /hr  for  3  items.  for  each  equation. search  This  was  not  within  trends  11 t h r o u g h  a  between growth  functional  abundance  of  that  for  juvenile  salmon  feeding  4.5mm  in  body  f o r the juvenile  this  general  group  prey  densities  ability  length. salmon  by  analysis  more e f f e c t i v e l y  was  (or selection)  fitting revealed  that  for large  zooplankton rate of to  were  be  content  quantify  to capture  the  different estimated  to a multispecies  juvenile  high  to  growth  functional  The stomach  search  the data  on  the  greater  estimated  used  r a t e s of s u c c e s s f u l  fish  The minimum  category. were  of  zooplankton  15 d e p i c t e d a  rates,  abundance  i n the net growth 14 s u g g e s t  mean  response  in zooplankton  Figure  Relative prey  i n the  of prey  length.  relative  prey  for  reflected  to the  and a s s o c i a t e d prey  predators  aggregation  body  and  search  general  zooplankton  used  the relationship  values  general  Figures  curve  method  c o n c e n t r a t i o n and f i s h  which.were  in  the sampling  described  were  fish.  of  fish  column.  parameter  week  The  to the concentrations  the s p a c i a l  zooplankton  There  juvenile  environment.  concentration  similar  However,  section  estimated  equation.  data  water  the  were  determining  10 m e t e r The  was  waters.  to investigate  semi-natural  that  the enclosures  CONCLUSIONS  designed  in a  demonstrated  inside  the  were  AND  disc  salmon  appear  to  c o n t r a s t prey  items.  The  76  relative  rates  of s u c c e s s f u l search  between  prey  groups  that  the enclosed  provided  salmons'  and the l a c k  further  minimum  support  rate  Relationships derived  in recent  made  possible to obtain  independent  i t  successful that  a  search  The to  otolith  possible  that  coupled  with  daily  and  assumption, otolith  a daily  of  is  growth  factors.  The  the  a  juvenile  removed  scale.  is  in  Figure  on  a  an  on  would  the assumption  of and  that  daily  surrounding of  a  functional  affected  growth  otolith provide  not g r e a t l y  fish  attempt  salmon  with  affects  to  15. I t was  salmon's  possibility  between  3 was  correlated  uncertainty  the  be a b l e  prey.  abundance,  i s based  confounding  relationship time  food  highly  otolith  and  shown  studies  suggested  should  in section  was  the r a t e of  studies  f o r 3.0mm  of  relationship  contention  feeding  estimate  These  increments  estimates  growth  growth  functional  a  presented  growth  estimate  Such  environmental  on  daily  3  t o my  fish  salmon  2.7m /hr  relationship  daily  otolith  growth,  analysis  salmon.  juvenile  at least  the  accurate  response.  feeding  search  strengthen  more  for juvenile  visually  successfully  an  covariance  of s u c c e s s f u l search  2.0m /hr. 3  of  by  the  fish other first  temperature estimating food  on a  abundance  77  LITERATURE  Arthur  Barkman  CITED  D.K. 1956. P a r t i c u l a t e f o o d a n d t h e food resources of the larvae of three p e l a g i c f i s h e s , e s p e c i a l l y the Pacific sardine. Ph.D. Thesis, University of C a l f o r n i a , 231 pp. R.C. 1978. The u s e o f o t o l i t h g r o w t h r i n g s silversides, Menidia menidia Atlantic F i s h . Soc , 1 0 7 ( 6 ) : 790-792.  t o age young . Trans. Am.  B a r r a c l o u g h , W.E., D.G. Robinson and J.P. Fulton. 1968. Data record. Number,size composition, weight and f o o d of larval and juvenile fish caught with a two-boat surface trawl i n S a a n i c h I n l e t . A p r i l 23 t o J u l y 21, 1 9 6 8 . F i s h . R e s . B o a r d C a n . M a n u . R e p t . S e r . No. 1004. Becker,  CD. 1973. Food and growth parameters of juvenile chinook salmon i n c e n t r a l C o l u m b i a R i v e r . U.S. Fish. B u l l . 71: 387-398.  Biette,  R.M. and G.H. Geen. 1980. Growth of underyearling sockeye salmon under c o n s t a n t and c y c l i c temperatures in r e l a t i o n to l i v e zooplankton r a t i o n s i z e . Can. J. F i s h , a n d A q u a t . S c i . 37: 2 0 3 - 2 1 0 . .  Blaxter  J.H.S. Ecology 285.  1970. L i g h t : F i s h e s . I n 0. K i n n e ( e d . ) M a r i n e V o l . 1 J o h n W i l e y & S o n s , New York. pp.213-  Brett,  m e t a b o l i sm and swimming J.R. 1964. The respiratory salmon. J, Fish. Res. p e r f o r m a n c e of young sockeye B o a r d Can. 2 1 ( 5 ) : 1183-1226.  Brett,  J.R. 1965. The r e l a t i o n ' of size to rate c o n s u m p t i o n and s u s t a i n e d swimming s p e e d of J . F i s h . Res. B o a r d Can. 2 2 ( 6 ) : 1491-1501.  Brett,  J.R. a n d T.D.D. G r o v e s . 1 9 7 9 . P h y s i o l o g i c a l In F i s h P h y s i o l o g y V o l . 8 Academic Press, pp.280-344.  Brett,  J.R., J.E. S h e l b o u r n a n d C.T. S h o o p . 1969. G r o w t h r a t e and body c o m p o s i t i o n of f i n g e r l i n g s o c k e y e salmon, in r e l a t i o n t o t e m p e r a t u r e and r a t i o n s i z e . J . F i s h . Res. Board Can. 2 6 ( 9 ) : 2363-2394.  Brett,  J . R . a n d D.A. H i g g s . 1 9 7 0 . E f f e c t s o f t e m p e r a t u r e on t h e rate of gastric digestion in fingerling sockeye s a l m o n . J . F i s h . Res. B o a r d Can. 27: 1767-1779.  of oxygen sockeye.  Energetics. New York,  78  Brett,  J.R. 1971. i n t a k e of 409-415.  Satiation time, sockeye salmon. J .  a p p e t i t e a n d maximum f o o d F i s h . R e s . B o a r d Can." 2 8 :  Brett,  J.R. a n d J . E . Shelbourn. 1975. Growth rate salmon in r e l a t i o n t o f i s h s i z e and r a t i o n F i s h . R e s . B o a r d C a n . 3 2 : 2 1 0 3 - 2 1 1 0 . R 30  Brett,  J.R. 1976a. Scope f o r m e t a b o l i s m and growth of sockeye salmon and some related energitics. J. Fish. Res. B o a r d Can. 3 3 ( 2 ) : 307-313.  Brett,  J.R. 1976b. F e e d i n g metabolic rates of young sockeye salmon in relation t o r a t i o n l e v e l and temperature. F i s h , and Mar. S e r . T e c h . R e p t . No. 675.  Brooks,  J . L . and S . I . composition  Brothers,  Confer,  D o d s o n . 1965. P r e d a t i o n , o f p l a n k t o n . S c i e n c e 150:  body size, 28-35.  and  E.B. , CP. M a t h e w s a n d B. L a s k e r . 1976. D a i l y growth increments i n o t o l i t h s of larval and adult fishes. N a t . O c e a n i c A t m o s . Adm. ( U . S . ) F i s h . B u l l . 74: 1-8. J . L . and P.I. planktivorous  Craddock,  of young level. J.  B l a d e s . 1975.omnivorous zooplankton f i s h . L i m n o l . O c e a n o g r . 20: 5 7 1 - 5 7 9 .  and  D.R., T.H. B l a h m a n d W.D. Parente. 1976. Occurrence and utilization of zooplankton by j u v e n i l e chinook salmon i n the lower Columbia R i v e r . T r a n s . • Am. Fish. Soc. 105(1): 72-76.  Davies,  J.M., J.C. Gamble and J . H . S t e e l e . 1975. P r e l i m i n a r y studies with a large plastic enclosure.pp. 251-264. In: E. Cronin Ed. Estuarine Research, V o l . 1. C h e m i s t r y , B i o l o g y and the E s t u a r i n e System, Academic Press, N.y.  Elliot,  J.E. 1969. Prog. F i s h  Elliot,  The o x y g e n r e q u i r e m e n t s C u l t . 3 1 ( 2 ) : 67-73.  chinook  salmon.  J . E . 1976. T h e e n e r g e t i c s o f feeding, metabolism, and growth of brown trout in r e l a t i o n t o body weight, water temperature and r a t i o n s i z e . J o u r n a l of Animal E c o l o g y 45: 9 2 3 - 9 4 8 .  Engstrom-Heg, R. 1968. D i e t a n d e s t u a r i a l impoundment. Fish. 3(1): 5-26. Fulton,  of  growth of j u v e n i l e F i s h . Res. Pap.,  salmon Wash.  i n an Dept.  J.D., O.D. K e n n e d y , K. S t e p h e n s a n d J . S k e l d i n g . Data r e c o r d . P h y s i c a l , c h e m i c a l and biological Strait of Georgia 1 9 6 8 . F i s h . R e s . B o a r d Can.. R e p t . S e r . No. 1049.  1969. data, Manu.  79  Gamble,  J . C , J.M. D a v i e s a n d J . H . S t e e l e . 1 9 7 7 . L o c h Ewe experiment. Bulletin of Marine Science. 27(1): 175.  Gazey,  W.  Grice,  G.d., M . r . R e e v e , P. K o e l l e r a n d D.w. 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F e e d i n g s t r a t e g y . In F i s h P h y s i o l o g y A c a d e m i c P r e s s , New Y o r k . pp. 71-113. V.S. 1961a. growing 374.  Ivlev,  V . S . 1961b. E x p e r i m e n t a l Y a l e U n i v . P r e s s , New  Johnson,  Kerr,  Method fish.  J.  northern research.  Hyatt,  Ivlev,  bag 146—  the patterns of prey and kokanee in Marion Of B.C., V a n c o u v e r . Vol.  8.  of e s t i m a t i n g the food utilized by F i s h . R e s . B o a r d C a n . T r a n s l . S e r . No.  ecology of the H a v e n , 302 p .  W.E. 1961. A s p e c t s of the zooplankton-eating f i s h . Verh. 14: 727-731.  feeding  fishes.  ecology of a pelagic, Int. Verein. Limnol.  S.R., and N.V. Martin. 1968. T r o p h i c - d y n a m i c s o f l a k e t r o u t p r o d u c t i o n systems. In J.H. S t e e l e ( e d . ) Symp. M a r i n e F o o d C h a i n s , A a r h u s , 1968.  Koeller,P.  and T.R. Parsons. 1977. The growth of young salmonids: c o n t r o l l e d ecosystem p o l l u t i o n experiments. B u l l e t i n o f M a r i n e S c i e n c e 27 ( 1 )': 1 1 4 - 1 1 8 .  Laurence,  G.C 1977. A b i o e n e r g e t i c model' f o r t h e a n a l y s e s of feeding and survival potential of winter flounder larvae during the period from hatching to metamorphasis. F i s h . B u l l . V o l . 75(3): 529-546.  80  Laurence,  Lawson,  G.C., T.A. H a l a v i k , B.R. B u r n s and A.S. Smigielski. 1978. An e x p e r i m e n t a l c h a m b e r f o r m o n i t o r i n g " i n s i t u " growth and s u r v i v a l of l a r v a l f i s h e s . N a t i o n a l Marine Fisheries Service, Northeast Fisheries Centre.  T . J . G.D. G r i c e . 1977. Zooplankton controlled ecosystem pollution Mar. S c i . 2 7 ( 1 ) : 80-84.  sampling variability: experiments B u l l , of  Lebrasseur, R.J. 1969. Growth of juvenile chum (Oncorhynchus keta) under d i f f e r e n t f e e d i n g J . F i s h . R e s . 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F i s h a n d Game, F i s h . B u l l . 152: 1-105. Protasov,  V.R. 1970. Vision and near Translated by M. R a v e h . I s r a e l Translations L t d . I P S T C a t . No.  Shelbourne, J.E. 1957. The larvae i n good and Ass. U.K. V o l . 36:  feeding and bad p l a n k t o n 539-552.  orientation Program f o r 5738.  of fish. Scientific  condition patches. J.  of Mar.  plaice Biol.  Strusaker,  P. a n d J.H. U c h i y a m a . 1976. Age and g r o w t h of nehu f r o m t h e H a w a i i a n I s l a n d s a s i n d i c a t e d , by d a i l y g r o w t h i n c r e m e n t s of sagittae. Natl. Oceanic Atmos. Adm. ( U . S . ) F i s h . B u l l . 74: 9-19.  Sysoeva,  T.K., and A.A. D e g t e r e v a . 1965. The r e l a t i o n between the f e e d i n g of cod larvae and pelagic fry and the distribution and abundance of t h e i r p r i n c i p l e food o r g a n i s m s . S p e c . P u b i s . I n t . Comm. N.W. Atlant. Fish. V o l . 6: 411-416.  Takahashi,  M., W.H. Thomas, D.L.R. Seibert, J. Beers, P. K o e l l e r , a n d T.R. P a r s o n s . 1975. The replication of biological events in* e n c l o s e d w a t e r c o l u m n s . A r c h i v . H y d r o b i o l . 76: 5-23.  Taubert,  B. a n d three Fish.  D.W. C o b l e . 1977. Daily rings in otoliths species of L e p o m i s and T i l a p i a mossambica . Res. B o a r d Can. 34: 332-340.  of J.  Wankowski,  J . W . J . 1979. Morphological limitations, prey size selectivity, and g r o w t h r e s p o n s e of j u v e n i l e Atlantic s a l m o n . J . F i s h B i o l o g y 14: 89-100.  Wankowski,  J.W.J, and J.E. Thorpe. 1979. The role particle size in the growth of juvenile s a l m o n . J . F i s h B i o l o g y 14: 351-370.  Ware,  D.M.  1972. P r e d a t i o n by r a i n b o w t r o u t : hunger, prey density, and prey B o a r d Can. 29: 1193-1201.  Ware,  D.M.  1973. trout.  Ware,  D.M.  1975. Growth, m e t a b o l i s m and o p t i m a l of a p e l a g i c f i s h . J . F i s h . Res. Board  Ware,  D.M.  the size.  of food Atlantic  influence J. Fish.  R i s k o f e p i b e n t h i c p r e y t o p r e d a t i o n by J . F i s h . Res. B o a r d Can. 30: 787-797. swimming Can. 32:  of Res.  rainbow  speed 33-41.  1978. Bioenergeties of pelagic fish: theoretical c h a n g e i n swimming s p e e d and r a t i o n w i t h b o d y s i z e . J.F i s h . Res. B o a r d Can. 35: 220-228  82  Warren,  Wiborg,  Wilson,  Winberg,  Zaret,  C.E., a n d G.E. Davis. 1966. Laboratory studies on the f e e d i n g , b i o e n e r g e t i e s and growth of f i s h , p. 175-214. In S.D. G e r k i n g (ed.) Symposium: the b i o l o g i c a l basis of freshwater f i s h p r o d u c t i o n . John Wiley and Sons, L o n d o n . 495 pp. R.F. 1948. I n v e s t i g a t i o n s on c o d l a r v a e i n t h e w a t e r s of n o r t h e r n Norway. O c c u r e n c e of cod and occurence of food organisms in the c o n t e n t s and i n t h e s e a . Rep. Norw. F i s h . Mar. 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HANDLING  THE  Chinook Vancuver, All  tank  The  of  5-6  4 mm  fish  salmon  and f r e s h l y  weighing  used  reared  to being  hatchery  for  6  time,  the f i s h  caught  t h e 48 h o u r s  months  transferred  in this  in  as the experiment  Sciences Institute  remained  this  Capilano  were  had been  a t t h e Ocean  intervals,  before  the  Columbia  During  OMP  from  (OMP) p r i o r  young  weeks.  two  g  Pellets  holding  two  salmon  British  these  Moist  FISH  3.2m were  animal.  on  to a  Oregon  fresh  at Patricia holding  3  North  Bay.  tank  f e d an e x c e s s  zooplanton with  before vaccination  water  for  ration  the exception a n d t h e 48  of  hours  and b r a n d i n g .  Transport  The five  fish  large  were  garbage  OTABS  were  oxygen  f o r 100  of  700  cans  placed  in  because  The t o t a l  juvenile  lined each  fingerlings.  the containers  depletion.  transported  chinook  i n 70 with  litres  plastic  garbage  There  was  salmon.  was  garbage  bags.  can to p r o v i d e very  of overcrowding  mortality  of h a t c h e r y water  153 f i s h  high  Three  sufficient  mortality  resulting  in  in  i n two oxygen  out of approximately  84  Vacc inat ion  Fish Inorder not  be  to vaccinate  fed the f i r s t  Patricia An the  container  The  fish  from  for  10  could was  recovery this  were  moved  easily  designed  hours  soon they  prior  to v a c c i n a t i o n .  as p o s s i b l e , were  ml  at  14°C. A  seconds; to  was  the f i s h  i n the holding  were  tank  period  parts/thousand  and  at  fish  of 8 days The  water  i n about  used were  held  solution  was The  salt  water  4 hours  In  450  were  air  seconds; cases  associated allowed  was  not a  ml  10-15  most  an  introduced  replaced  and  The  i n the  f o r 10  water  was  bath.  with  no m o r t a l i t y fish  shallow  to select  recover.  before  fresh  mixed  into where  A  vaccine  (Hivax)  to  there  procedure.  tank.  salt  tank  tank  vaccinated.  d i p n e t was The  vaccine  holding  aireated  i n the vaccine  rapid  vaccination  and  vaccine  tank.  large  very  small  the well  small  holding  dunked  to get the v i b r i o  into a  of v i b r i o  the  the holding  used  removed  t o be  50  the small  immunization into  as  that  was  be  water  returned  with  days  method  fish  contained  fresh  and  f o r 48  the f i s h  two  immersion  fish.  bath  starved  Bay.  several  of  should  with  single  28 fish  died.  Weighing  The a  and M e a s u r i n g  first  step  was  solution containing  of  salt  water.  and  operculum  As  the F i s h  to anesthetize  15-20 soon  movement  as  ml  of  4 methyl  the f i r s t  slowed,  4 fish  i t was  fish  by  placing  2 pentanol rolled  removed,  and  onto  rolled  them i n 500  ml  i t s side  over  lense  85  paper  to  remove  Electronic digital  Balance.  readout  specifically fish  were  where  the  a  Branding  and  the  the was  of  of  pairs of  on  bars  would  quadrant  line.  The protruding  from  handle.  copper  quadrants.  for a  Metier from  the  using  a  tray  and  recovery  period  handling had  bucket  of of  30-60  the  fish  no  observable  and  one  to  were 6  of  at  the  the  fish,  the  dorsal  2  forms  sets of  various  by  lateral  possible  brand  each  consisted directions  fish.  the  administered  of  The  deliniated  f i n and  were  brand.  oriented  side  were  brands  measuring  two  line.  For  f i n and to  the  of  brands  physical example,  below same  the  side  quadrants; ; and  of  of 10  course,  fish.  branding  nitrogen  on  and  "V"  orientations;  every  The  aerated  process  distinct  anterior  There  brand  to  be  a V s  dorsal  Both  individual.  sides  or  quadrants  one  2  recorded  measurement  necessary  this  weighing  quadrants  the  of  the  a  measured  The  well  on  fish.  with  "|"  structures:  pairs  was  tray.  in a  case  the  then  unconscious  reduced  initial  four  lateral  dipped  remain  marked  four  The  was  placed  Fish  individual  the  measurement  in every  effect  During  two  would  weight  and  fork-length  T h i s method  detrimental  in  and  subsequently  minimum  moisture,  Its  designed  fish  seconds. to  surface  implement a  then  small end  was  applied  consisted  mass  of  dipped to  the  of  copper in  a  fish  a  copper  attached thermos in  the  wire  to a  wooden  of  liquid  appropriate  86  This  method  of d i s t i n g u i s h i n g  very  successful.  Brands  marks  d i d not appear  were  each  easily  to effect  individual  read  after  the fishes'  proved  1-2  days  ability  to  to  be  and the swim  or  feed.  II.  HANDLING  Deployment  The The  THE  of  NETS  Nets  protective  n e t was  t o p o f t h e n e t was  positions  roughly  2  lashed m  a t t a c h e d to the bottom  were  lowered  ropes  Twelve  more  weighted  sides  of  the  were  by  flotation  platform  protective  net.  a l l  then  ropes  tying  one  to  net  surface  easily  the  same  polypipe  four  rings  t o space  weights  shape.  platform.  to  hold  the  ropes  ropes  the rest  of the rope  the  of  kg w e i g h t s  Their  were  to  the  into  the  three  the bottom  provided  other of the  from  the  ropes.  experimental  technique. F i r s t ,  kg c o r n e r  nylon  through  18  weights  These  help  at  4 corner  the f l o t a t i o n  place.  pulled  n e t a n d a t t a c h e d t o 20  The  and 20  position.  platform  desired  heavy  with  were  detached  set into  positioned  in  protective on  to be  tossing  ropes  line  the  of the  Subsquently,  the  on tied  had  end  and  lead  o f t h e n e t . The  protective  positioned  divers,  A  the net took  supporting  t o be  to the f l o t a t i o n  apart.  were  until  the f i r s t  e n c l o s u r e s were  four  ropes  the rings  4m  were apart.  a l ldeployed  using  attached to the three Second,  the  rings  87  and  ropes  net  were  placed  stretched  tight  enclosure  was  to  the  the  bottom  ring.  The  into  the  ring  net  of  short  Cleaning  designed  4m  of  mesh method  occurred, The  a  the  handle,  the  rubber  boat  weights  boat  to  of  the  to  check  of  the  the  whole  and  transported  were  attached  and  the  net  to was  inside  the  flotation  ropes  and  released  the  the  bottom  Next,  process,  once  most  the  ring.  guide  attached  ropes  and  the  four  waiting  ropes  guide  of  sinking  small to  nets  aluminum  There,  up a  mesh  4.8m  site.  The  rings  of  enclosure weight  polytubing  net to  was  fully  the  guide  2.  dive  was and  necessary to  nets the  make  were fish  the  the  necessary  thoroughly to  on  shape  and  depth  adjustments.  inspected  During  f o r broken  mesh  escape.  Enclosures  to  were  remove  without was  used  removing to  removing pool  removing  the  loosened  tubing  and  dumped  clean  the  amounts the  the  clumps  i t outside  the  the  water.  fouling,  was  used  brush,  on  phytoplankton  phytoplankton the  from  method top The  wherever  enclosure.  fouling of  from  extensive  enclosures. A  the  fouling  enclosure  remove  the  e n c l o s u r e s . One  of  cleaning apparatus  loosened  sucked  to  moderate  suitable  after  modified  without  4.8m  into  secured  methods  was  mesh  bottom  transferred  permit  the  Two  it  the  into  the  enclosure  would  second  to  Figure  same d i v e  that  was  This  see  each  the  to  speed  water.  extended.  A  to  partly  secured  ropes,  the  experimental  transferred  were  lifted  inside  flotation  to the  the  end  the  while  through ring.  clean  the  of  the  pump  vacuum  88  Extensive the  removal  thoroughly  buildup of  cleaned  suspended  from  removed  a  by  modified  each  of  enclosure, out  a  of  cleaning  to  was  raised  up  and  down  type  action;  (3)  The  net  dried  enclosure  experimental the  III.  rate the  Two  were  methods the  fish  following  end  The  brushed  the  water dry  on the  and  4.8m  mesh; in a the  cleaned  p o s s i b l e to  remove  was  (1)  The  handle,  was  (2)  The  washing pier  next  were  fouling  techniques:  the  off  removed  GROWTH  used  in each  =  1,  GT  and  the  100  individuals  are  the  for  and  the rate  mean  disadvantage  estimate  to  the  be  net  machine  over  night  morning. once  during  the  than  90%  better  method.  FISH  GR  growth  estimate  left  could  to  RATES  calculate  the  enclosure  each  (LOGeGT  LOGeGt)  average  weeks.  daily  Both  growth  models  used i  formula.  method  the  was  they  enclosures  while  minus  the  so  The  tide  off  mesh n e c e s s i t a t e d  time,  following  through  was  this  OF  estimated to  by  low  fouling  I t was  CALCULATION  of  the  was  period.  fouling  In at  spray  phytoplankton  Each  of  and  a  the  water.  at  the  on  at  apparatus,  used  and  brush  of  one  the  large pier  combination  pool  phytoplankton  X  Gt  the  beginning (GR)  of  sizes of  f o r each  growth  rate  this  captured the  are  -  in  average  for  method two  a  of  T  an  week  the  "T"  could  population  i s obvious  rate  individual  with  individual  successive  growth  /  of  weeks. the  fish  days.  be  The  combined  that  when  fish  week.'  very  For  few  example,  i n the  9  mm  89  mesh e n c l o s u r e d u r i n g the second week i s based on  only  2  fish  ( F i g . 7).. In  method  2,  GT and Gt are the average s i z e s of the f i s h  sampled at the end and the beginning of a weeks with In  days.  t h i s case GR would be the, estimate of the average growth  for  the  population  significant or  "T"  sample  that  week.  This  method q u i c k l y  b i a s . Some samples had  rate  revealed  predominantly  larger  s m a l l e r than average f i s h . T h e r e f o r e , i f smaller than average  fish  were  sampled  sampled  one  week and l a r g e r than average f i s h were  the next week, the  calculated  growth  rates  would  be  b i a s e d upwards. An estimate of sample the  average  growth  b i a s c o u l d be obtained by c a l c u l a t i n g  rate using the average i n i t i a l  s i z e s of the  f i s h sampled each week. The best estimate of the mean growth rate o f the p o p u l a t i o n for  each week was c a l c u l a t e d  attributable  to  sample  bias  by  subtracting from  estimated i n method 2 ( F i g . 7 ) .  the  the  average  growth  rate  growth  rate  

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