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The effects of experience on the acquisition of food by juvenile chum salmon, Oncorphynchus Keta, in… Levy, David Alan 1977

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THE EFFECTS OF EXPERIENCE ON THE ACQUISITION OF FOOD BY JUVENILE CHOM SALHON, ONCORHYNCHUS KETA OF THE SQUAHISH RIVER  , IN A TIDAL CREEK  ESTUARY,  B.C.,  By DAVID ALAN LEVY B.Sc,  McGill  A THESIS SUBMITTED  University,  1975  I N PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Dept. o f  5Je a c c e p t  this thesis reguired  Zoology)  as conforming  to the  standard  THE UNIVERSITY OF BRITISH COLUMBIA September, David  1977  Alan Levy,  1977  In p r e s e n t i n g t h i s  thesis  an advanced degree at the L i b r a r y I  further  for  freely  of  the  requirements  B r i t i s h Columbia, I agree  available  for  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 copying o f  this  representatives. thesis for  It  financial  The  of  gain s h a l l not  ZOOLOGY  U n i v e r s i t y o f B r i t i s h Columbia  2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5  Date  September 30. 1977  that  this  thesis or  i s understood that copying or p u b l i c a t i o n  w r i t ten pe rm i ss i on .  Department  for  reference and study.  s c h o l a r l y purposes may be granted by the Head of my Department  by h i s of  fulfilment  the U n i v e r s i t y of  s h a l l make it  agree  in p a r t i a l  be allowed without my  Abstract  The keta  f e e d i n g behaviour  , was  analysed  tecfanigue.  The  were s i m u l a t e d the  Pish  by  creek  of  recaptured.  After  animals  experimental  fish  the  of  River  naturally  contrast,  Hoist  experience,  and  intertidal  subsequently  were  was  tows i n t h e t i d a l  experimental  no of  difference  in  groups.  Only  animals  by  means  o f morning  creek  close  to  i n t r o d u c t i o n s . Anisogammarus was  vertical  m i g r a t i o n and  predators i n the t i d a l of  amphipod-conditiqned  creek  was  apparently  at t h e t i m e  a  measurable  fish  was  attributed  the  amphipod-conditioned  experimental  assessed  fish  i n the  there  both  very  few  compared  to  numbers o f e p i b e n t h i c i n v e r t e b r a t e s p r e s e n t  column  fish  o c c u r i n g chum j u v e n i l e s  juveniles.,  Relative  the  other  the other experimental  o c c u r r i n g chum  lack  Oregon  r e l e a s e d i n t o an  o f Anisogammarus i n t h e d i e t to  of  the  naturally  The  type  Anisogammarus  or  t h e p r o p o r t i o n o f Neomy.sis i n  by  diel  prey  p r o p o r t i o n o f Neomysis i n m y s i d - c o n d i t i o n e d  In  compared  plankton  ,  estuary,  amphipods were a c g u i r e d  water  amphipod  laboratory  were marked and  g r o u p s and  creek.  proportion  a single  field  i n t h e l a b o r a t o r y w i t h one -  days  and  A n a l y s i s o f t h e stomach c o n t e n t s o f i n t r o d u c e d  greater than  tidal  with  Heomysis l e r e e d i s  30  Oncorhynchus  laboratory  experience  types  Squamish  showed t h a t t h e was  combination  feeding animals  , the mysid  the  j u v e n i l e chum s a l m o n ,  of  food  Pellets.,  experimental  using a  effects  following  confervicolug  of  of  the  and  time  in  the  evening of  the  shown t o u n d e r g o a unavailable to the  treatment to t h i s  fish  introductions. effect factor.  in  iii  The was  proportion of  different  a c r o s s a l l treatment  introduction dates. on  the  the  relative  second  b a s i s i n the  Neomyjsis i n t h e d i e t  The  higher  groups  realized  i n t r o d u c t i o n date  tidal  creek.  on  two  availability  indicated  abundance o f v a r i o u s p r e y  of experimental  types  fish  consecutive of  Negmysis  that d i f f e r e n c e s i n occurred  on  a  daily  iv  T a b l e 'Of C o n t e n t s  Abstract  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . .  i i V  L I S T OF FIGURES LI ST OF TABLES  v i  ACKNOWLEDGESENTS  . ... .  w.. :,.;,.>>•;.•.„••,... . . . ..... . . . ... ,  INTRODUCTION  1  HETHODS AND HATERIALS Regular  Sampling  Laboratory Field  ., ...V  4  .•  4  Conditioning  *.  Introductions  Benthic  Sampling  Laboratory  .  .... . . . . . . . . . . . . . ..•< «.  13 14  .. . Sampling  6 11  Stomach A n a l y s i s  RESULTS Regular  viii  .. .  ..............................  16 16  Conditioning  Experiments ..............................  19  Benthic Prey  Samples  33  DISCUSSION  ,.y*-.yv>,.-.>>.,^  36  :  E f f e c t s Of E x p e r i e n c e Prey  Availability  I n The T i d a l  36 Creek  Food Of Chum Salmon I n The Sguamish LITERATURE CITED . . . . . . . . . . . . APPENDICES . .. . ... . . . . . . . . . . . .. .  ^y,, Estuary  43 46  . , ..y , . r .  l?  50  ,. .. v,-.y,:.^.vV..cvV ,•....:/ 53  V  L I S T OF FIGORES  Figure  1. L o c a t i o n  Squamish Figure The Figure  Of The T i d a l  Sguamish  Estuary.  4. View  5.  Of  Diet  The  M y s i d , Neomy.sis  Tidal  Creek  6. D i e t  At  keta•,  Estuary  On A p r i l  m e r c e d i s . ....8 Successive  7., C o m p a r i s o n  15/76.  8. C o m p a r i s o n Selected  C r e e k On J u l y  Tidal  On J u n e 8 And J u l y  1,1976  Of The D i e t Of W i l d Groups R e l e a s e d  Creek  Creek 18  Chum  Juveniles  Into  The T i d a l  ...................................22  Of The D i e t Of  Experimental 16/76  In The T i d a l  I n The  Experimental  Tide  21 And May 26,1976. ... 17  Of J u v e n i l e Chum Salmon Estuary  In A  .... 12  Of J u v e n i l e Chum Salmon  C r e e k On J u l y  And  The  Found I n  ,.  And S e l e c t e d  Figure  In  ...........................3  ,•  Of The Squamish Figure  Crustacea  3. A J u v e n i l e Chum Salmon, Qncorhy.nchus  Of The Sguamish Figure  Area  5  2. Two O f The Common I n t e r t i d a l  Levels. Figure  Study  Estuary.  Tank W i t h The E s t u a r i n e Figure  Creek  Wild  Groups R e l e a s e d ,  Chum Ipto  Juveniles The T i d a l 23  vi  l i I S T OF  Table  1. S i z e s Of D i f f e r e n t  TABLES  Food T y p e s Used I n C o n d i t i o n i n g  Experiments. Table  2.  Tidal Table  ...  Sizes  Of  Juvenile  C r e e k Of The  .. •. 9  Chum Salmon  Squamish  Sampled  July T a b l e 4.  15 And  The  E s t u a r y . . . . . . . . . . . . . . . . . . . . . .9  3. P e r c e n t a g e R e c a p t u r e S u c c e s s And The  A n i m a l s Which  From  Fed D u r i n g T i d a l  Creek  P e r c e n t a g e Of  Introductions  On  16,1976....................................20  Average  Experimental  Length,  Height,  And C o n d i t i o n  A n i m a l s R e c a p t u r e d From  The  Factor  Two  Of  Combined  T i d a l C r e e k I n t r o d u c t i o n s . .,. . . .... .... . . .. . . . . . . . . . . . . . . 21 T a b l e 5.  Correlation  Between  ^ O c c u r r e n c e Methods  Of  Introductions  2.  T a b l e 6.  1 And  Occurrence  of  J u v e n i l e Chum Salmon 2.  Results  Stomach  Of  ^Volume  Analysis  For  And  Combined ...25  Prey  In The Stomach  f o r Combined  Contents  Introductions  1  of And  ...................................................,.27  T a b l e 7.  Results  Conditioning  From  History  3-way  G-test  (C) X P r e y Type  Of I n d e p e n d e n c e F o r (P)  X  Occurrence  (0) .  28  T a b l e 8. R e s u l t s From Type  (P)  X  3-way G - t e s t  Introduction  J u v e n i l e Chum Salmon S m a l l Amphipods. Table  9.  Results  Conditioning Occurrence  For Prey  (I) X O c c u r r e n c e (0) F o r  C o n d i t i o n e d T o Feed  On  Large  And  .... . . . . . . . . ........... .... . . . . . .......28 From  History Of  Date  of Independence  Mysids  3-way (C) (O)  G-test X  Of I n d e p e n d e n c e F o r  Introduction For  Juvenile  Date  (I)  X  Chum  Salmon  Introduced Table  10. The a v e r a g e  Prey  Categories  Groups. Table  I n t o The T i d a l Number  creek. . . And  Consumed  Variation By  Plankton And Table  Numbers  Size  Of  And  Variation  Epibenthic  Tows In E a r l y  After Tidal 13.  Number  Of  Experimental  ................................................30  11. T h e A v e r a g e  12.  In  Different  M y s i d s Consumed By The D i f f e r e n t Table  28  Two-way  (Square-Root  In  Experimental  Of  Groups.  ..32  I n v e r t e b r a t e s Caught I n  M o r n i n g And L a t e  Evening  Prior  To  Creek I n t r o d u c t i o n s Analysis  Of  34  Variance  T r a n s f o r m e d ) Of Anisogammarus  gnoriroosphaeroma  Length  , And I n s e c t L a r v a e  On  Numbers  , Neomysis ,  Caught In  Plankton  Tows . . . . . . . . . . . . . . . . . . . . . . . . . . . .......................,35 Table  14. Numbers Of Amphipods P e r Gram Dry H e i g h t Of F u e u s  Caught  In  Basket  Introductions  Traps  Before  And A f t e r  Tidal  Creek  ................................,.........35  viii  ACKNOWLEDGEMENTS  t o t h e development o f t h i s  Many p e o p l e c o n t r i b u t e d My s u p e r v i s o r .  Dr. J.D. M a c P h a i l ,  constantly  provided  constructive  criticism  and e n c o u r a g e m e n t . Dr.C.p.Levings i n t r o d u c e d  Sguamish  estuary  and  During the formative helpful  advice.  advice.  me t o t h e  e n t h u s i a s t i c a l l y supported t h e research.  stages  of  this  Dr.C.F.fehrhahn  An e a r l y v e r s i o n o f t h i s  substantially  improved  by  work,  K.Hyatt  freguently manuscript  gave  gave was  statistical reviewed  Animal Resource Ecology,  J . K a a t s who p a r t i c i p a t e d i n v a r i o u s N.McDaniel in  at  introductions.  without  the P a c i f i c  members assist the  like  from  the  a s w e l l a s E . S c a n l a n and  stages  access  are  of  the  field  study  Society  my p a r e n t s  not  work.  have  for  their  constant  o f Canada,  of B r i t i s h for their  as  well  moral  staff  willingness to support  as  Columbia. F i n a l l y ,  unceasing  been  facilities  West V a n c o u v e r . The  I acknowledge the f i n a n c i a l  Research C o u n c i l  Research  would  to the e x c e l l e n t laboratory  thanked  me i n my r e s e a r c h .  t o thank  This  Environment I n s t i t u t e ,  there  National  Salmon  I  s u p p l i e d t h e p h o t o g r a p h s f o r t h e t h e s i s and a s s i s t e d  the f i e l d  feasible  and  helpfulness.,  T h a n k s a r e a l s o due t o t h e many g r a d u a t e s t u d e n t s of  much  D r s . T . G . N o r t h c o t e and W . E . N e i l l .  thank t h e s e i n d i v i d u a l s f o r t h e i r  Institute  thesis.  the  of XXV  I would  support.  1  INTRODUCTION  Chum s a l m o n have  evolved  , Oncorhynchus keta  a life  through  a variety  rivers  and  history  , i n the Pacific  Northwest  that involves extensive  migrations  o f h a b i t a t s . F r y hatch  streams  and  migrate  out o f  down t o an e s t u a r y  proportion of the population  resides  into  and e v e n t u a l l y i n t o  marine l i t t o r a l  areas.  Feeding  can take  most f r y a r e t h o u g h t estuary.  areas,  Several  studies  juveniles i n estuaries Dunford, et  1975)  important  feeding only  document  and i n n e a r - s h o r e  i t  apparent  source  gravel  in  where some  before  moving  offshore  marine  (Sparrow, 1968), but after  reaching  the  t h e f e e d i n g h a b i t s o f chum 1972 ;  Mason, 1974;  marine e n v i r o n m e n t s  a l . , 1 9 7 5 ) . ; From  i s  as a food  grows  ( Goodman and V r o o a ,  al.,1973;Feller et  investigations  and  place i n f r e s h water  t o begin  the  the  (Kaczynski  results  of  these  that epibenthic crustaceans are  during the early  phases  of  juvenile  typically  acguire,  existence. Many as  feeding  food, only  organisms  s t u d i e s suggest  a small  in  their  density-independent behavioural differences  of the t o t a l  environment.  on  might a c c o u n t  are  repeated  include  the part  i n the a v a i l a b i l i t y  set of potential  Explanations  exploitation  selection  that  formation  subset  that f i s h  of  t o account f o r perceptual  of the predator, prey  types.  One  f o r t h e changes i n f e e d i n g a b i l i t y  experiences  of a " s p e c i f i c  with  search  a  particular  image"  food  prey  or  as well as mechanism when type  (Tinbergen,1960).  there i s the Here  2  the of  predator the  prey  l e a r n s to r e c o g n i z e morphological  and  Available  t h e r e f o r e " l e a r n s t o see" the laboratory evidence  learning  ability  (eg.  feeding  ability  on  indicates  O'Connell,1960) a  g i v e n prey  with  Beukema,1968; Ware,1971;  Bryan,1973).  frequently contain "runs"  o f one  and  Curio  (1976) i n t e r p r e t s  a learning  ability  searching  ability  studies, only  as  one  Gilbert in  of  study  ecological are  laboratory arrived  B.C.,  cyclopoids, relatively  Vroom  in  the  a  in  low  are  likely  t o have r e p e a t e d  few,  p r e y t y p e s . The  f e e d on  assesses  in  the  environment.  detail  and  compared  to  generalizations  in  the  mysids,  as  with  i n most  of  Squamish  food  types.  i n estuaries chum  with a s i n g l e , present  the  temperate  i n the  juvenile  the  Sguamish amphipods,  Compared  species diversity  encounters  experiments  their  experimentation  the  diversity  (Odum,1971) e s t u a r i n e p r e d a t o r s , s u c h  for  (Rolling,1965)i  ( L a r k i n , 1 9 5 6 ) , chum s a l m o n  relatively  evidence  although  that  insects.  low  types  this.,  report  juveniles  relatively  stomachs  from l a b o r a t o r y  experiment,  confidence  terrestrial  (Ivlev,1960;  field  that,  a  their  improve  Apart  g e n e r a l i z e d f e e d i n g h a b i t s of f i s h  estuary acquire of  to  the  field  (1972)  chum s a l m o n  freshwater ecosystems  Because  fish  Larkin,1972)  argue  in a  possess  fish  considerations and  and  greater  and  improve  experience  prey..  a t more t h a n c o m p e n s a t e s f o r  estuary,  can  d i s c u s s the value of f i e l d  sacrificed  Goodman and  fish  Moreover  the  experience  research  work,  that  as c i r c u m s t a n t i a l  specific  (Bryan  predator  e t al.,(1976)  simplicity  this  the p a r t of  for  prey..  o r a s m a l l number o f p r e y  w e l l as t h e o r e t i c a l fish  importance  on  and  characteristics  salmon, or o n l y a  study  were  3  therefore on  designed  the e f f e c t s  t y p e , on To  assess  feeding  the r o l e  animals  types,  e x t e n s i o n o f p r e v i o u s l a b o r a t o r y work  of p r e d a t o r e x p e r i e n c e , w i t h  subsequent  experimental prey  a s an  then  process  manifested  of  by  of experience  marked and  released into  associative  animal  which h a s  a specific  approach,„  handle,  information  {Ware,1971) s u g g e s t s  and  presumed  a fishes*  After  in  a  the f i e l d ,  experienced  relative  their  fish.  prey  that that  i n the  refers  animal  o c c u r on  to  which i s a  item" r e f e r s to  an  prey  after  to  search  item.  a finite  for,  Laboratory number  of  i s m a x i m i z e d , and i t  the  animals*  ingestion  o f prey  was  experimentally introduced  animals  s t o m a c h c o n t e n t s a n a l y s e d . The  primary  to test  whether e x p e r i m e n t a l a n i m a l s prey  animals of the  previously, r e l a t i v e technique  also  availability  i n t r o d u c t i o n d a t e s , as effect  effects  would o v e r - e x p l o i t  e x p e r i e n c e . The the  creek  Thus  experience,  ingest  period of time,  of the experiment  had  several  efficiency.  were r e c a p t u r e d and aim  of  study an  searching efficiency  that similar  handling  in  salmon,  one  a tidal  present  learning  l e a r n e d , through and  prey  chum  a change i n some a s p e c t o f i t s b e h a v i o u r .  c o n d i t i o n e d t o f e e d on  is  i n juvenile  were c o n d i t i o n e d t o f e e d on  "fish  experiences,  particular  behaviour.  Sguamish e s t u a r y . C o n d i t i o n i n g i n the the  a  well  behaviour  on  as  a  they  to predators lacking  provided a  of different  type  means  prey  means  such  for  assessing  t y p e s on  subsequent  for  the v u l n e r a b i l i t y  ,  determining of the prey  to  the the  4  METHODS AND  To  evaluate  MATERIALS  conditioning  in  mark-recapture experiment  was  history  manipulated  was  previously  Experimental Squamish about  animals  Estuary  45  km.  diet  of these  fish  samples  performed u s i n g  (Fig.1), located at north  of  V a n c o u v e r , B . C.  taken  in  as w e l l  the  was  same  salmon,  whose  a tidal head  Following  compared tidal  in  Howe  the  Sound  recapture,  to  the  creek  as b e n t h i c samples t a k e n  known.  creek  of  a  feeding  therefore  into the  chum  fish  and  were i n t r o d u c e d  •'conditioned" f i s h  introduction,  juvenile  the  diet  of  to  the  prior  d u r i n g and  after  the introduction..,  l§aalar  Before  Sampl.ins  the experiment a beach s e i n e  m i c r o n mesh i n t h e  two  section)  was  to c o l l e c t  from t h e  tidal  estuary  is  used  creek.  shown  drains completely allowed  a  concentrate were  then  sufficiently. in  an  wing p a n e l s  The  and  (2.4m  65  location  when the t i d e  a l l the  to  be  fish  into  a  or  m i c r o n mesh i n the  bag  of the  tidal  used  1.5m.  small  when  the  creek  i n a South C a r o l i n a  the  and  tide  estuary.  Dean  so  This  sampler area.  S i m i l a r methods w e r e u s e d by C a i n and  intertidal  in  level.  as a p a s s i v e  relatively seined  creek  is inter-tidal  i s below t h e  seine  dipnetted  130  m o n t h l y s a m p l e s o f j u v e n i l e salmon  i n Fig.1. T h i s channel  beach  x 36.6m, w i t h  and  These dropped (1976)  6  Sampling level  sere  the  level)  mouth  o f the t i d a l  and a f f i x e d  tidal  i n position  creek.  so that a rapid  a 10% f o r m a l d e h y d e  drop  The n e t was  creek at high tide  positioned (about  dropped  3.7m.  for later  of  sufficiently, a  was d i p n e t t e d and i m m e d i a t e l y  solution  i n tide  by two s t a k e s on e i t h e r s i d e  When t h e water l e v e l  s u b s a m p l e o f 10-15 f i s h in  chosen  o c c u r r e d d u r i n g t h e morning hours.  across  the  dates  laboratory  preserved  analysis.  Laboratory Conditioning  The estuary  animals used  aquarium  i n plastic  facilities  Vancouver, transfers,  B.C.  garbage p a i l s  water  these  temperature  at  o x y g e n was b u b b l e d  fiberglass  The f i s h  the c o n t a i n e r s f o r about  and, i f t h i s  A few f i s h  f e d Oregon  Vibriosis  to  died  Best  10°C by  deficiency,  eg.  was e v i d e n t , p u r e a  one  relieve  during  minute  symptoms o f  transport  and  more t h a n 551 o f t h e t o t a l .  were m a i n t a i n e d tanks  i n c i r c u l a t i n g freshwater  at d e n s i t i e s  o f about  t a n k . B e f o r e , and d u r i n g c o n d i t i o n i n g were  oxygen  sufficient  the  were w a t c h e d f o r any  into  usually  suggest  and  subsequent  a t about  surface,  oxygen s t r e s s .  fish  maintained  to  Institute, a l l  the  apparent  The  and  might  This  but never  Environment  was  samples,  estuary  that  period.  handling,  was  the  transfers,  b l o c k s o f i c e t o t h e water.  congregating  from  at the P a c i f i c  During  abnormal behaviour  liter  were o b t a i n e d f r o m t h e  i n e a r l y J u n e i n t h e same manner a s r e g u l a r  transported  adding  i n t h e experiments  Hoist  i n 125  400 i n d i v i d u a l s p e r  treatments,  a l l animals  P e l l e t s coated with Terramycin  to control  d i s e a s e . T h i s d i s e a s e was known t o be c a r r i e d  by  some  7  of  the wild Two  seine of  species  of  and a p l a n k t o n  t h e prey  species other  types  were:  estuarine crustaceans,  net from  used  the  t h e Squamish e s t u a r y ,  mysid, N e o m j s i s m e r g e d i s Anisoqammarus  and 3 ) . . B o t h  the estuary  about  5  and i t was u s u a l l y  days  of  food  (2.0mm,  depositing  1.19mm,  about  one  trip  downward screens, and  their  and  thousand  0.5mm  addition  the tanks  treatment to  two s l i g h t l y  of  thedifferent  crustaceans stretching Appendages,  were the eg.  food  types  measured animals  certain  areas  Two d i f f e r e n t  a series of 3 mesh  amphipods  submerged  diameter)., on  the  size  After  uppermost  away f r o m a r o u n d t h e s e i v e s crawl  through  the  seive  was t o o g r e a t t o a l l o w f u r t h e r  amphipods  groups  sized  (Stimpson)  numbers  remaining  used a s food  on two o f t h e in  the  small  respectively.  the t h r e e l i v e  different  , and t h e  t o provide adequate  0.5mm  r e c e i v e d o n l y Oregon Moist  of  length  The  T h e two  enough  with  and 1.19mm, were t h e n  l a r g e amphipod In  body d i a m e t e r  penetration.  to  three  acquire  t h e h y d r o p h i l i c amphipods would t h e n  screens u n t i l  over  conditioning.  ( c o a r s e s t ) s e i v e , w a t e r was s i p h o n e d and  (Holmes)  abundant  possible  c l a s s e s o f amphipods were o b t a i n e d seives  by beach  formed  confervicolus  were e x t r e m e l y  i n d i v i d u a l s on any o n e s a m p l i n g for  collected  i n the c o n d i t i o n i n g experiments.  t h e amphipod,  (Figs.2 of  fish.  prey  types,  Pellets.  pellets.  i s given  Fish  fish  i n two o f  were f e d  A summary o f t h e  i n Table  one sizes  1. L e n g t h s o f t h e  w i t h a n o c u l a r m i c r o m e t e r by g e n t l y under  a  antennae and r o s t r a ,  dissecting  microscope.  were n o t i n c l u d e d i n any  measurements.  During  thef i r s t  two weeks o f l a b o r a t o r y c o n d i t i o n i n g a l l  8  F i g u r e 2. Two o f t h e common i n t e r t i d a l C r u s t a c e a found i n the Squamish estuary. The d o r s o - v e n t r a l l y f l a t t e n e d s p e c i e s i s t h e i s o p o d G a o r i m o s p h a e r o m a o r e g o n q n s i s and t h e l a t e r a l l y flattened s p e c i e s i s t h e amphipod Anisoqammarus c o n f e r v i c o l u s .  Fiqure 3. A j u v e n i l e chum s a l m o n , O n c o r h y n c h u s k e t a with the e s t u a r i n e mysid, l e o m y s i s tnercgdis .  i n a tank  9  PELLET TYPE A  PELLET TYPE B  50  50  50  50  1.9  1.6  5. 1  7.9  0-73 1  0.40  •+-  Number Measured Mean Length mm | I  Standard Deviation  11  i Mean I Diameter | mm  1 1  0.8  j Standard I Deviation  1 I  0.04 |  n  rt  T a b l e 1. S i z e s experiments. ;  •  of  It  | Mean | Length | mm  ) | | | ||  I Mean I Height I g  || | |  |  LARGE AMPHTPOD  |  1.00  1.31  -  1  -  0.07  -  |  |  food  M YS ID  +-  0.87  types  21/76 | May 26/76  |  1.91 |  i  used  | June  50  11.9  f  . . M M *  different  \ S a m p l i n g |I A p r i l I Date ||  IN  |  SMALL AHPHIPOD  i n  >  conditioning  8/76 | J u l y  1/76  |  15  |  9  |  15  |  9  |  41.7  I  40.7  |  48.4  |  49.4  |  0.6 3  |  0.63  |  0.98  |  1. 12  |  | a~  0.0085  |  0.0082  |  0.0090  II  I Mean | | | Kfactor* H 0.0081 t _ .._ i i_. -_ . _. *K=wt/0.1L3  _i-  Table 2. Sizes o f j u v e n i l e chum s a l m o n c r e e k o f t h e Sguamish e s t u a r y .  •  sampled  —L_  | ._" .. i  from t h e t i d a l  10  fish  were g i v e n a s much p e l l e t  could  be  consumed  in  a  food, three  shaken i n a beaker and then  the tank,  live  a s m a l l amount a t a t i m e .  food  to  a s many p r e y  f o rtheir  subsequent occur  not  duration  of  the  the l i v e  food.  Animals  w i t h i n 10  near  start  with a dipnet  after  in  the  conditioning  of  the  o f one o f t h e  p e l l e t s f o r the  food  happened  experiment,  10 m i n u t e s .  meal. I n t o t a l ,  10/76 t o J u l y  which  the  spread  Before  marked  of anal,  marking,  the  blade.  animal  received  by  caudal, fish  mark was o b t a i n e d by c u t t i n g scalpel  1-2  were u n a v o i d a b l e days  were days  due t o  the  fish  food a s a replacement f o r  fish  out over  received  30  days  of  a 34 day p e r i o d , f r o m  13/76.  individually  combination  several  t h e prey  At t h e end o f 30 days o f c o n d i t i o n i n g e x p e r i e n c e , were  was s a i d  on  Three gaps o f  i t e m s . On t h e s e  meal o f p e l l e t  experience  pellet  p l a c e . When f e e d i n g d i d  c o n d i t i o n i n g schedule  an a d d i t i o n a l food  two  a s c o u l d be consumed i n a 10 m i n u t e  minutes,  the  on J u n e  c o n d i t i o n e d on l i v e  meal o f t h e d a y , and f i s h  lack of available l i v e  received  June  on o n e  m e a l s . One d a y ' s c o n d i t i o n i n g e x p e r i e n c e  take p l a c e  removed  first  Pellets  Conditioning started  whether o r n o t any f e e d i n g t o o k  occasions  the  and t h e p e l l e t  received  period two  types  as  presented  afternoon.  and t h e o t h e r t h r e e g r o u p s on a c o m b i n a t i o n  food  day,  introduced v i a the i n f l o w i n t o  10,1975. Two g r o u p s were m a i n t a i n e d types,  per  10 minute p e r i o d . F o o d was  t w i c e i n t h e m o r n i n g , and once i n t h e e a r l y were  times  fin-clipping or  dorsal  (either  fins  were a n a e s t h e t i z e d w i t h  fish  one  or a  clipped). HS-222. The  o f f the t i p of a f i n or f i n s  The maximum number o f f i n c l i p s was  were  the  two. F i v e g r o u p s o f f i s h  an  with a  experimental  were d e p r i v e d o f  11  food  f o r two  creek. by  days  before  I n a d d i t i o n , two  their other  experimental  s t a r v i n g some o f t h e p e l l e t - t r a i n e d  days  instead  sticklebacks, effect  on  beginning period  of  2  the l e n g t h o f  the of a  feeding feeding  predators  field  the  the  a  total  have  of  that a  marked the  deprivation  i n an  maximally r e a c t i v e t o were a t o t a l  7 in  hour a f t e r  long  fish  tidal  obtained  showed  initial  used  Thus t h e r e  i n the  a  (1968)  conditioned  be  for  d e p r i v a t i o n can  experiment. I  creek.  t r e a t m e n t g r o u p s used  of 7  attempt the  to  prey  different  experiment.  Introductions  after  several  i n t o the  tidal  period,  about  magnitude  of  trial  creek,  to handling  creek  food  into  g r o u p s were  fish  Beukema  r a t e during  which would  items i n the t i d a l  due  days.  f o r some o f t h e p e l l e t  obtain  h o u r s , would be  or  diel  the  tidal  fish  by  and,  after  the  beach  tidal  creek,  r e l e a s e them  75  meters  and  in  seine  length  normal  { they  of the  was  i n t o the  apparently  o b j e c t s ) . One  tidal  fish  and  sunrise  boat  was the  formed s c h o o l s  Fig.4  was  area.  advantages of using  of the  the tidal  mouth o f  The  of  release  fairly  and  small  the  enclosure  s u r f a c e and  both l i v e  the  estuary,  m e t e r s wide a t  time  attacking  shows  the  at the  at the  effects  to transport to  20  fish  introduction  course  i n place  and  of  t o overcome  the  enclosed  at  long  changes.  procedure followed  behaviour of the  after  necessary  means o f t r u c k  recaptures  a fairly  changes during  mouth. The  observed  that  12  i n t r o d u c t i o n s . The  extended  i n t r o d u c t i o n s and  I decided  experimental  be  introduction  the was  could  inanimate fish  for  12  F i g u r e U. View o f t h e t i d a l c r e e k i n t h e S q u a m i s h estuary at successive tide l e v e l s . A b e a c h s e i n e i s i n p l a c e a t t h e mouth r e s t r i c t i n g t h e movements o f i n t r o d u c e d f i s h .  13  the c o n d i t i o n i n g plasticitydid  the  animals  not apparently  creek  probably  recaptured  (50mm)  proved  was  their  t o be a d a p t a b l e  behavioural  t o h a n d l i n g and  r e g u i r e a long adjustment p e r i o d t o t h e t i d a l  environment b e f o r e  would  the  experiments  be  starting  to  more s i g n i f i c a n t  Handling  f o rlarger  were  bag s e c t i o n o f t h e n e t and u s i n g a d i p n e t t o r e t r i e v e  them.  dragging  a  introductions  small  beach  fish  were  recovered  seine inside the enclosure.  recapture, the animals  were  formaldehyde  and  solution  the  by ' h e r d i n g *  Fish  into  one o f t h e  i n the afternoon  fish.  effects  them  During  a t low t i d e  feed.  immediately stored  preserved  Following in  f o r subsequent  by  a  10%  laboratory  analysis.  Benthic  During used  to  different the  Sampling  the period o f f i s h obtain  prey  use  of  information  types  to  plankton  be  on  i n the t i d a l  basket  traps  Anisoqammarus c o n f e r v i c o l u s found  introductions  effective  the  One o f  assessing  ( L e v i n g s , 1976) .  was  net used as a b e n t h i c  a  0.25mz,350  sampler  by  wire  baskets  F u c u s d i s t i c h u s were s u s p e n d e d the  mouth o f t h e t i d a l  intervals  creek.  d u r i n g and a f t e r  numbers o f amphipods c a u g h t  were  abundance these  the The  involved  numbers  other  micron towing  of  of  method  SCOR/UNESCO beside  the  (20cm x 20cra x 20cm) s t u f f e d  with  a t about  near  s e d g e mats a l o n g t h e m a r g i n s o f t h e t i d a l Replicate  methods  relative  creek.  for  two  creek.,  t h e 3.1m  T h e s e were t h e n  the the course were e x p r e s s e d  tide  level  removed a t v a r i o u s  o f t h e e x p e r i m e n t . The p e r gram  dry  weight  14  of  Fucus . Plankton  evening  after  tows were made o n two m o r n i n g s b e f o r e , and on one the experiment,  by d r a g g i n g  o f t h e s e d g e mat f o r t h e e n t i r e sedge  detritus  was  t h e net a l o n g  length of the t i d a l  collected  by  this  t h e edge  creek.  Much  method and some o f t h e  o r g a n i s m s were p r o b a b l y  a d h e r i n g t o sedge l e a v e s or rhizomes  the  time  The p l a n k t o n  10S?  formaldehyde  of sampling.  solution  and  s a m p l e s were p r e s e r v e d  subsequently  identified  at in a and  counted. ,  Laboratory  The fish  Stomach A n a l y s i s  methods used  obtained throuqh  from  the  rinsed  two  r e g u l a r sampling  i n t r o d u c t i o n s . , The  i n t a p water,  nearest  f o r stomach a n a l y s i s  blotted  and t h e e x p e r i m e n t a l  preserved  individuals  and  weighed  then  O.Q1g on a M e t t l e r H65 b a l a n c e .  under a d i s s e c t i n g  microscope  examined f o r f i n c l i p s . identified  as  to  dissected  from  the  were  counted.  Amphipods  micrometer different volumetric  then  was  spread  with  the  the  were the  measured the  fins  positively  were o m i t t e d  stomach.  o u t on a p e t r i  mysids  were  dish,  measured  0,Imm^ The r e l a t i v e  approximated  displacement  to  fish  stomach  from was  by i n c i s i o n s a t t h e e s o p h a g u s and t h e  caeca  and  and  t h a t c o u l d n o t be  conditioning history  gut  to the nearest prey  mm  Following i d e n t i f i c a t i o n ,  of the p y l o r i c  contents  They were t h e n  t o the nearest  A l l animals  their  subsequent a n a l y s i s .  junction  dry,  were t h e same f o r t h e  of  by  e a c h prey  visually type  The  stomach  i d e n t i f i e d , and by  importance  occular of the  estimating  the  under t h e b i n o c u l a r  15  microscope. the  Percent  number  values  for  Additionally, counted  and  independent percent  of  occurrence  occurrences  the  of  individual  the  numbers  percent  a l l i t e m s and then  prey of  of  and p e r c e n t  to  a  a l l prey  frequency  measurements  occurrence,  v a l u e s were o b t a i n e d  values  summing  s c a l i n g the  percentage  basis.  types i n the d i e t obtained.  stomach c o n t e n t s frequency)  by  were  Thus  were three  ( p e r c e n t volume, determined.  16  RESULTS  Regular  The  Sampling  average  length,  (weight/length )  statistics  3  creek  weight,  condition  f o r the fish  sampled  b e f o r e t h e i n t r o d u c t i o n s a r e shown i n T a b l e  i n d i c a t e an i n c r e a s e i n t h e a v e r a g e the t i d a l  creek  Figures  the t i d a l  over  size  May  26,  there  from  the percent  2. T h e s e  data  captured i n  time. t h e t h r e e methods o f  a p p l i e d t o t h e r e g u l a r samples o f f i s h  creek.  factor  i n the t i d a l  of the f i s h  5 and 6 show t h e r e s u l t s from  stomach a n a l y s i s in  and  On two o f t h e s a m p l i n g  appears  dates,  April  t o be l a r g e d i f f e r e n c e s  frequency  a n a l y s i s o f t h e prey  obtained 21  and  i n the results items  and  the  o t h e r two methods. T h i s d i s c r e p a n c y c a n be e x p l a i n e d by t h e h i g h representation (0.5-1.Omm  of  i n length)  method o v e r e s t i m a t e s The  other  two  on  the  in  of these  and t h e s m a l l percent  y  t h e r e l a t i v e importance  and  results  ftPisogammarus  cyclopoids)  diet  organisms. The  subsequent  of  the  F i g u r e s 5 and 6, i t c a n be s e e n fie.  the  of this  percent  ,  group.  occurrence,  comparisons  are  volume a n a l y s i s .  From  t h a t many o f t h e p r e y  confervicolqs  make up d i f f e r e n t  dietary  size  frequency prey  methods, p e r c e n t v o l u m e and p e r c e n t  show c l o s e a g r e e m e n t based  cyclopoids  terrestrial  organisms  i n s e c t s , and  proportions o f the d i e t  over  time.  17  100 •  %  100  FREQUENCY  v  %  75...  75.  SO.  50-  ES.  es.l  0.  o  H—h—1H 1 !• 5- 3- 4- 5- G« 7- B- 9.10-  FREQUENCY  4=1-  1  JL» £> a « 4« 5« 6- 7. B' 9-10  100 v  1  1O0-  %  75.  OCCURRENCE  50.  so...  25.1  ES...  0  %  75...  OCCURRENCE  0>._ 1» E> 3- 4- 5. E' 7' S- 9'10.  -+-  1- S- 3- 4> 5- G. 7- B. 9>10.  100.  100 v  %  VOLUME  %  75.  75...  50-  SO.  ES.l  E5.I  .  -I—I  !• E' 3- 4. 5. G' 7- B- 9-10.  !• 5- 3- 4. 5- G- 7. B- 9-10-  PREY TYPE  PREY TYPE A P R I L 21/76 N =l5  VOLUME  o  O 2  .5  a  Z  E  e2  o o o c c a M . .3 o H H 1 1  MAY 26/76 N«=9  E g0  1 1 1  1 u1  1  !• E< 3' 4. 5. 6- 7. 8< 9-10-  PREY TYPE  Figure  5. D i e t of j u v e n i l e c h u m s a l m o n i n the t i d a l c r e e k Squamish  of the  e s t u a r y on A p r i l 21 and M a y 26, 1976.  18  100  100 v %  75.1  FREQUENCY  %  75  SO  FREQUENCY  50...  ES.j.  ES...  0  H—I 1—I h ! • E« 3> 4. 5. G' 7- B- 9.10.  !• 5- 3. 4- 5. G« 7- B' 9.10 100.  100. %  75...  OCCURRENCE  T  %  75  50...  50  ES...  E5.I  OCCURRENCE  H 1 1 1. B« 3- 4- 5. G- 7. B' 9-10-  !• S- 3. 4. 5. G> 7- B. 9-10 100.  100 %  75...  VOLUME  %  75.  50...  VOLUME  50.  55...  ES.I !• 2. 3-  A-  5. E« 7. B> 9-10  1. £• 3-' 4.' 5.' G.' 7.' B.' 9.'i0.'  PREY TYPE  PREY TYFE  J U N E 8/76 N = 15  « o  a. E _  J U L Y 1/76 N =9  3  £  E  E 2 O  «  h  c u u o J h> t i i i — i — i — y Z  !• E« 3- 4.' 5.' 6« 7.' 0.' g.'io.' PREY TYPE  Figure  6. D i e t of j u v e n i l e c h u m - s a l m o n i n the t i d a l c r e e k of the S q u a m i s h e s t u a r y , on J u n e 8 and J u l y 1, 1976.  19  Conditioning  Recapture trial  Experiments  rates of  introductions  i n t r o d u c e d = 1 2 3 ) and and  44%  recapture a  net.  enclosure,  (no.,  15/76)  the spaces  and  21%(July  a c t u a l experiments losses  and  staghorn  The  two  during  t h e two  weight,  and  16/76)  average  which e a c h  lasted  of  condition  introductions,  factor  floats  statistics  as and  armatus, on  around  f o r the  between t h e r e c a p t u r e r a t e o f  experimental  experimental  of f i s h  account  the percentage  63%  substantially  predating  leakage  p r e d a t i o n by s c u l p i n s ,  (no.  were  seine  observed  processes,  4-hour  21,1976  sculpins , - Leptocottns  were  r e c a p t u r e r a t e s and  two  creek enclosure,  between t h e b e a c h  enclosure,  fish.  April  the l e n g t h of time o f the experimental  The  the the  apparent  experimental  introduction..„  of animals along  with  t h a t fed length,  are given i n Tables  3  4. Comparison o f t h e stomach c o n t e n t s  of  on  for  introduced-9)  period. Substantial  inverse relationship  and  creek  around t h e edges o f t h e t i d a l  the  experimental  animals  These recapture r a t e s are  In a d d i t i o n ^ in  and  1,1976  16% ( J u l y  through  trapped  fish  July  the t i d a l  rates during the  occurred  w e l l as the  the  14-hour t i m e  fish  into  respectively.  higher than  for  experimental  wild  chum  juveniles  and  shown i n F i g u r e s 7  (July  and  detailed  II outline  experimental  the fish  and  selected  15/76) and results  show  volume,  all  percent  8  ( p e r c e n t volume experimental  (July  groups  are  16/76). A p p e n d i c e s I  o f stomach a n a l y s i s three  method)  methods  analysis-  percent  occurrence,  frequency.  T h e r e i s good a g r e e m e n t between t h e  of and  percent  of  the  stomach percent volume  20  CONDITIONING HISTORY  ~rr-  LENGTH OF FOOD DEPRIVATION  r  Introduction  NO. INTRODUCED  f  RECAPTURED  FED  1 J u l y 15/76  Mysid  2 days  90  26%  74%  Small Amph  2 days  95  1515  93%  Large Amph  2 days  90  8%  86%  Pellet Type A  2 days  75  11%  88%  Pellet Type B  2 days  75  12% •,  100%  Pellet Type A  7 days  35  29%  100%  Pellet Type B  7  40  18%  86%  24%  90%  days  • i, i  - _ + +  Mysid  Introduction ; 2 days ;  H  2 J u l y 16/76 , 125  Small Amph  2 days  120  23%  96%  Large  2 days  110  15%  88%  Pellet Type A  2 days  85  18%  100%  Pellet Type B  2 days  105  24%  92%  Pellet Type A  7 days  40  18%  86%  Pellet Type B  7 days  55  9%  100%  i i  T a b l e 3. P e r c e n t r e c a p t u r e s u c c e s s and t h e p e r c e n t a g e o f a n i m a l s which f e d d u r i n g tidal creek introductions on J u l y 15 and 16,1976.  21  - ~ ~rr| N f CONDITIONING | | LENGTH OP FOOD | | HISTORY || DEPRIVATION |  a  I  —|r:  "TT  -1—  "S  | AVE. I AVE. | AVE. | LENGTH | WEIGHT | KFACTOR | mm i g 1  Mysid  |1 2 d a y s  \  53  |  57.9  |  1.76  f  0.0088  |  I Small 1 Amph  | J 2 days | |  J  42  |  53.5  |  1.41  J  0.0087  |  I Large 1 Amph  j j 2 days | |  1 24  |  50.8  I  1.18  J 0.0084  j  | Pellet J Type A  | |2 d a y s |j  | 23  |  55.0  1  1.47  I  0.0084  |  J Pellet 1 Type B  11 2 d a y s M  | 34 J  52. 1  I  1.26  I  0.0083  |  I Pellet J Type A  | | 7 days | |  | 17  I  51 . 5  I  1.13  |  0.0078  |  I Pellet | Type B  || 7 d a y s 19  j 12  |  53.8  1  1.29  I  0.0080  J  t.  —  -  i  a..  '  ..«,  a ......  ,.  -X  _  _ J  iK=Wt/0.1L3 Table 4. A v e r a g e length, weight, and c o n d i t i o n f a c t o r of experimental animals recaptured from t h e two combined tidal creek i n t r o d u c t i o n s .  22 iOOv  JUNE  100.  8/76  MYSID CONDITIONED 75-1 J U L Y 15/76 N=17  N = 15  75 50 4  50..:  55  E5...  n  0  n  O  !• E» 3' 4- 5« 6> 7. 8- 9-10.  ..  -i  n  i  <  1  1 1  1. £• 3> 4- 5- E« 7- 8> 9.10. 100  100.  JULY  75  SMALL  1/76  AMPHIPOD  75... C O N D I T I O N E D J U L Y 15/76 N = 13  N=9  50...  50.  E5...  ES.  0  H  1 1 1 h  1' £• 3- 4. 5' 6> 7. 8- 9«10«  A  PREY TYPE  !• E« 3- 4« 5. 6- 7. B- 9-10. 100-^  A.  PELLET  TYPE A  CONDITIONED  75  J U L Y 15/76 N=7  SO ES.j: 0  « u. ZH O U U J  I  h  4=1-  PREY TYPE  £ 5  c ° £ o £ < UO  1 1 1 1 1 1 r 1 1 1 !• E> 3- 4. 5- B- 7- B« 9-10.  • Figure  H  A  e e  1 1  1' E> 3. 4. 5. 6- 7. 8. 9.10 i 1  PREY'TYPE,  7. C o m p a r i s o n of the diet of w i l d c h u m j u v e n i l e s and s e l e c t e d e x p e r i m e n t a l g r o u p s r e l e a s e d i n t o the t i d a l c r e e k on J u l y 15/76. H i s t o g r a m s r e p r e s e n t p e r c e n t volume results.  23 lOO.  JUNE  75-1  MYSID  8/76  75..  N = l5  CONDITIONED  JULY N =  50-.  16/76  27  E5-.  o.  -n  ~1  1.  E- 3- 4- 5- G- 7« 8' 9-10.  i  —1 i — I — I — i i—I— ! • E« 3- 4. 5. 6. 7- 8' 3'iO-  100.  lOO-  JULY  75.  ""SMALL  1/76  AMPHIPOD  CONDITIONED "  N=9  JULY  50.  N  •-  16/76  = 27  ES=1 i . £. 3<  1 1 1 H—I  H  1. E« 3- 4. 5. 6> 7- B« 9-10. Jk  PREY TYPE  1 1 1 H 1 1—1 4- 5. G- 7- 6- 9.10.  100  A  PELLET  75  TYPE  A  CONDITIONED JULY  50  16/76  N = 15  ES.J: 1»  6  A.  -3' to  2 t£ E 2 o u V  V  Z  H  rt «  £ IS £  .e .e  o u u  5 S  £ £ 2" 5' Sg  -+—I—I—I—-I—-H—I E- 3- 4« 5- G» 7« B> 9-10' PREY T Y P E  C  e  •5 .2 c K <  t. o i. o c ° O O  H H 1 1 1 I 1 « IE- 3IH 4«15-1G. 7. B> 9'10JL.  PREY TYPE  F i g u r e 8. C o m p a r i s o n  of the d i e t of w i l d c h u m j u v e n i l e s and  s e l e c t e d e x p e r i m e n t a l g r o u p s r e l e a s e d i n t o the t i d a l c r e e k on J u l y 16/76. H i s t o g r a m s volume results.  represent percent  A  24  and  percent  coefficients between  occurrence  (Table  the  two  5}  methods and  which t e s t  methods,  are  Spearman r a n k  f o r the  significant  g r o u p s . T h i s i m p l i e s a good g u a l i t a t i v e of  the  two  considered different 8,  as  methods. to  a  the  valid  experimental  w e l l as  evident.  be  Thus  groups.  p r o p o r t i o n , of  to  feed  on  e i t h e r amphipods o r  to  feed  on  either small  acquire  a  other  higher  treatment  between t h e pellets. the  II,  Lastly,  diet,  of various  f o r the To  assess  animals of  similar  treatment  dates,  second,  by  groups f o r the  two  a  conditioned  apparently diet  did  not  than  the  differences in diet types  of  fish  between  lengths  d i f f e r e n c e s i n the geomys.is  of  relative  ,  in  the  between  the  dates. the  differences  occurrence  was  the e f f e c t s  employed due  data  the  in  a  three-way  outlined i n Sokal  i n two  different  diet  the  two  The  the  introduction  of i n d i v i d u a l  i n t r o d u c t i o n dates.  and  ways:  t o c o n d i t i o n i n g I lumped  groups from  comparing  different  are  conditioned  for different  f o r independence as  statistic  and  mysids a c q u i r e d  different  food  7  trends  Second, f i s h  components , n o t a b l y  to  and  on  of  statistically  ( 1 9 6 9 ) . The  on  were no  t o be  introduction  G-test  the  large differences in diet  appear  groups, I used the  classification  first,  two  assess  treatment  Bohlf  there  d i e t s of  in Figures  o f amphipods i n t h e  were no  are  following  o r l a r g e amphipods  conditioned  there  of the  results  results  d i e t t h a n those  pellets.  proportion  groups  volume  to feed  groups. T h i r d , there  Fourth,  proportions  the  mysids i n the  correlation  f o r a l l treatment  From t h e r e s u l t s  p e l l e t - f o o d groups deprived  time.  percent  animals conditioned  higher  of  agreement i n t h e  representation  A p p e n d i c e s I and  First,  lack  correlation  treatment  first  25  #  -  — '•  -T———  | CONDITIONING I| LENGTH OF j SPEAR HAN RANK |J FOOD | HISTORY | CORRELATION || DEPRIVATION | COEFFICIENT J SSVOL VS. %OCC I  "i—  -r  — • •• .—i  | DF 1  T  ! |  2 days  |  0.8542  1 7  |  4.346 * * |  1 Small I Amph  II  2 days  |  0.8152  |  |  3.980 **j  I I  Large Amph  1!  2 days  |  0.8482  1 5  1  3.581 *  | Pellet j Type a  II  2 days  I  0.9732  1 5  |  9.466 * * |  | Pellet | Type B  11  2 days  |  0.7818  1 8  |  3.547 * * |  j Pellet 1 Type A  11  7 days  |  0.8631  |  6  |  4.186 * * |  I Pellet | Type B  11  7 days  |  0.8875  1 7  I  5.096 * * j  i  , .  i  Mysid  ,  ,  .j.!.-.  'A _  8  .a.  1  _  *=.01< P < . 0 5 **= P < .01 Table 5 . C o r r e l a t i o n between r e s u l t s o f ^volume and % o c c u r r e n c e n e t b o d s o f stomach a n a l y s i s f o r combined i n t r o d u c t i o n s 1 and 2. T test evaluates the null hypothesis that the c o r r e l a t i o n between t h e two methods i s z e r o . ,  26  comparison examines  the  effects It  was  had  the occurrence  independence  (C) ",- p r e y  expected  as  of independence  (P) , and  i n Table 6  of  occurrence the  effects  prey c l a s s e s  inclusion  PxC  of the a n a l y s i s (G-value  independence was  non-occurrences  was  i n t e r p r e t a t i o n s one  and  conditioning (0) * which  would h a v e l e d  ( T a b l e 7)  show an  f o r CxPxO i n d e p e n d e n c e =  to  were computed. Note  test  c o u l d not be  designed  (ie.  identical can  well  the  way  of the occurrences  and  f o r the d i f f e r e n t  draw f r o m  as  that a G-value f o r  computed  t h e sum  overall 339.252)  f o r t h e v a r i o u s two-way t e s t s o f i n d e p e n d e n c e ^  the experiment  the  thereof  a n a l y s i s t o omit  t h e CxPxO i n t e r a c t i o n ,  the  lack  presented  G-value.  Since the r e s u l t s  G-values  data  values since their  i n t h e computed  lack  or  type e f f e c t s  necessary i n t h i s  low  error  uses  due  prey  to  types).  The  the r e s u l t s i n Table 7 include  following: 1. CxO  the t o t a l  type  no  significant  of prey  items  f o r the  independence-  the  t h e r e was  occurrence  a significant  accounts  independence. 3.  for  much  of  the  high  overall  of  prey  prey types  G-value  (  |CxPxO) l a c k  of  • • interaction-  and  the  PxC  order i n t e r a c t i o n  conditioning. across  ., •  CxPxO  significant, third  different  effect  o f p r e y . Thus t h e d i f f e r e n t  were n o t e q u a l l y r e p r e s e n t e d i n t h e d i e t . . The 284.146)  difference in  groups.  PxO  on  t h e r e was  number o f o c c u r r e n c e s  treatment 2.  independence-  Thus  the  since  test  was  constitutes lack  the not  CxO  performed,  evidence  o f PxO  test  for  a an  is  not  significant effect  of  independence i s d i f f e r e n t  the v a r i o u s c o n d i t i o n i n g t r e a t m e n t  groups.  27  CONDITIONING HISTORY  PREY  TYPE  NO. OF OCCURRENCES  NO.OF ABSENCES TOTALS  Mysid  Small  Large  Mysids Terr.Insect Amphipods Ins.Larvae I n s . Pupae  Amph  Amph  P e l l e t Food 2-day deprivation  P e l l e t Food 7-day deprivation  TOTALS  Mysids Terr.Insect Amphipods Ins.Larvae I n s . Pupae  Mysids Terr.Insect Amphipods Ins.Larvae I n s . Pupae  Mysids Terr.Insect Amphipods Ins.Larvae Ins.Pupae  Mysids Terr.Insect Amphipods Ins. l a r v a e I n s . Pupae  31 26 2 3 6  13 18 42 41 38  44 44 44 44 44  68  152  220  13 34 5 6 11  27 6 35 34 29  40 40 40 40 40  69  131  200  7 19 5 2 6  14 2 16 19 15  21 21 21 21 21  39  66  105  18 49 5 6 19  36 5 49 48 35  54 54 54 54 54  97  173  270  10 24 4 6 11  17 3 23 21 16  27 27 27 27 27  55  80  135  328  602  930  T a b l e 6. O c c u r r e n c e o f p r e y i n t h e s t o m a c h c o n t e n t s o f j u v e n i l e chum salmon f o r combined introductions 1 and 2. ( T e r r . I n s . = T e r r e s t r i a l I n s e c t ; I n s . L a r v a e = I n s e c t L a r v a e ; I n s . Pupae= I n s e c t Pupae.)  28  HYPOTHESIS TESTED CxO i n d e p e n d e n c e PxO i n d e p e n d e n c e PxC i n d e p e n d e n c e CxPxO i n t e r a c t i o n CxPxO  independence  DF 4 4 16 16  3. 868 284.146 ** not tested 51.24 .**  40  33 9.252 **  ** = P< .01 Table 7. R e s u l t s from 3-way G-test of independence c o n d i t i o n i n g h i s t o r y (C) x p r e y t y p e (P) x o c c u r r e n c e CO).  r  —  — >  | HYPOTHESIS TESTED  DF  I | J I  1 3 3 3  1,808 76.980 * * not t e s t e d 1. 170  10  79.956 * *  |  1x0 i n d e p e n d e n c e PxO i n d e p e n d e n c e P x l independence PxIxO i n t e r a c t i o n PxIxO  independence  for  G  a  **=P< .01 T a b l e 8. R e s u l t s from 3-way G - t e s t o f i n d e p e n d e n c e f o r p r e y t y p e (P) x i n t r o d u c t i o n d a t e (I) x o c c u r r e n c e (0) f o r j u v e n i l e chum s a l m o n c o n d i t i o n e d t o f e e d on l a r g e and s m a l l a m p h i p o d s .  HYPOTHESIS TESTED CxO i n d e p e n d e n c e IxO i n d e p e n d e n c e IxC i n d e p e n d e n c e CxIxO i n t e r a c t i o n CxIxO i n d e p e n d e n c e  DF 4 1 4 4  18.692 * * 6.002 * 7.836 8.264  13  40.794 * *  *=.01 < P < .05 **=P< .01 Table 9. R e s u l t s from 3-way G-test of independence for c o n d i t i o n i n g h i s t o r y (C) x i n t r o d u c t i o n d a t e (I) x o c c u r r e n c e o f mysids (0) f o r j u v e n i l e chum s a l m o n i n t r o d u c e d i n t o t h e t i d a l c r e e k o f t h e Sguamish E s t u a r y .  29  S i m i l a r a n a l y s e s were individual Again  treatment  groups  the  group  in  diet  for  s m a l l and l a r g e  introduction dates interaction  date  mysid-conditioned for  on fish  the  given  in  the  of mysids  3-way  of  of  diet.  Similar  significant mysids. that  Figs.,  7  and  i n the diet  results  PxIxO  exist  fish  analysis  for  deprived  suggest  performed  in  CxO  date  diet, on  as  the  confirms t h e t r e n d apparent  the  second  for  the  1x0 on t h e  well  as  occurrence  i n Figs.  i s a h i g h e r r e p r e s e n t a t i o n o f mysids  lack  and  conditioning effect the  a  (0).  an o v e r a l l  significant  of introduction  j u v e n i l e chum s a l m o n f r o m  groups,  on c o n d i t i o n i n g  ( T a b l e 9) i n d i c a t e to  diet  different  (I) x o c c u r r e n c e o f m y s i d s  mysid-occurrences effect  8  f o r a l l treatment  was  date  attributable  This result  there  the  date.  Thus t h e r e i s a s i q n i f i c a n t of  Since  different  t h e r e i s a p p a r e n t l y no e f f e c t o f  independence  of t h i s  independence  number  of  (C) x i n t r o d u c t i o n  G-values.  8.  fish  two d a y s . T h u s no d i f f e r e n c e s i n t h e o v e r a l l  representation  results  one  The r e s u l t s o f  f o r t h e two  Table  of  than  amphipod-conditioned  and t h e p e l l e t - c o n d i t i o n e d  S i n c e a comparison  history  diets  introductions. more  sample s i z e s .  are a t t r i b u t a b l e t o the i n t r o d u c t i o n  G-test  from  amphipod g r o u p s )  i s not s i g n i f i c a n t ,  introduction  food  are  the  i n t h e two d i f f e r e n t  to a c h i e v e adequate  comparison  (combined  The  comparing  i t was n e c e s s a r y t o p o o l t h e r e s u l t s  treatment  of  performed  a of  7 and 8  i n the diet o f  introduction  date  (July  16/76). Summary  statistics  consumed by t h e v a r i o u s t r e a t m e n t  mean  groups  number  of  are provided  prey  types  in  Table  10. The p r e y t y p e s c o n s i d e r e d a r e t h o s e shown i n t h e key on  30  r "—  —  J CONDITIONING | HISTORY  :  -TT  "T—  | | LENGTH OF i | FOOD  N  — i — | | i |  . MEAN NO OF PREY TYPES CONSUMED  i j DEPRIVATION T  ! Mysid  i||i  2 days  I Small | Amph  11  2 days  1 Large 1 Amph  II  2 days  I Pellet I Type A  I |  2 days  I I  Pellet Type B  ||  2 days  | Pellet 1 Type A  I |  7 days  I Pellet J Type B  ||  7 days  J  nn  j j  i  r1 STANDARD | DEV IN I NO OF | PREY TYPES CONSUMED  | | | | | J  i  |  1.70 5  no  I  2.025  21  |  2.000  22  |  32  |  0.878  |  1.050  |  |  1.183  |  1.636  |  0.789  |  1  2.250  |  1.077  J  16  1  2. 188  J  1.328  |  11  I  2.818  |  1.779  |  J  j.  -XI  ,  .. „.  ! i X  .„,  _  .JL _  ••' J."_-ii,r :  1  T a b l e 10. The a v e r a g e number and v a r i a t i o n i n number o f prey categories consumed by t h e d i f f e r e n t e x p e r i m e n t a l g r o u p s . P r e y categories considered were t h o s e listed i n figure 1 and calculations a r e based on t h e combined r e s u l t s f r o m t h e two i n t r o d u c t i o n dates.  31  Figs.5-8. difference  in  significant number  One  way  the  mean  (F=2.358,P  of  prey  The  group  pooled  (Table  the  only  an  in  of .01) 11)  this  either  (Table  with  this  f o r the  m y s i d s were measured a n d  the  the  o f 10 m y s i d s were consumed  variances  in  mysid  in  Sokal  t h e means a c c o r d i n g  o f t h e sample  from  11)  which they  and  ,  the  procedure  o f mysids  one e x c e p t i o n , mysids  amphipod o r p e l l e t -  as  Hohlf  m y s i d s was  (1969).  were t a k e n .  The  difference  results  (F=8.91,P <  a t t a c k e d . - I t c a n be s e e n  fish  conditioned  prey  items i n the t i d a l  conditioned  The  t o the r e c i p r o c a l of the  analysis indicate a significant  larger  length  ( i n d i c a t e d by t h e l a r g e d i f f e r e n c e s  outlined  i n t h e mean s i z e  acquired  for  and t h e small  t h e d i f f e r e n c e i n mean s i z e o f i n g e s t e d  weights  t h a t , with  greater  inconsistent  d e v i a t i o n column i n Table  approximation  variance  i s  t h e mean  prey-size distribution  groups, i n g e s t e d  extremely heterogenous  procedure  was  deprivation)  groups  11) i m p l i e s t h a t a t o t a l  testing  consumed  the  f o r e a c h g r o u p . Thus n=10 f o r t h e l a r g e - a m p h i p o d  i n the standard for  consumed  (2-day  by t h e g r o u p a s a w h o l e . S i n c e were  types  0 . 0 5 ) . With two e x c e p t i o n s ,  differences  treatment  results  prey  indicates  •  assess  various  of  variance  than f o r l i v e - p r e y - c o n d i t i o n e d a n i m a l s  amphipod g r o u p were  To  <  p e l l e t - t y p e A group  generalization.;  of  number  categories  pellet-conditioned 10) .  analysis  fish.  to feed  (Table  on m y s i d s creek  than  32  r-  "  CONDITIONING HISTORY  ••  T"  — r -  || LENGTB OF | NO OF | MYSIDS 1) FOOD { |DEPRIVATION | CONSUMED  |  1 1 1 I  |  l  !  i  1 l  i i  i,.  TT~  Mysid  | |  2 days  |  80  Small Amph  || | |  2 days  |  36  Large Amph  11 | |  2 days  |  J  10  Pellet Type A  11 | J  2 days  |  J  13  Pellet Type B  11 M  2 days  |  29  Pellet Type A  11 | |  7 days  |  3  Pellet Type B  | | ||  7 days  |  12  JUL.  !  J  \ 1  *  MEAN | LENGTH | I OF MYSIDS | | CONSUMED | | MM | ir i_  J J j  \ \  j  j J  !  j \ i  ._—  i  STANDARD DEV IN MYSID LENGTHS  | | | |  T  14.1  |  2.39  |  14.0  |  J  0.81  |  13.0  |  J  1. 09  |  14.2  |  3.06  |  !  11.6  |  j  1.61  |  11.4  |  J  4.31  |  12.7  |  2 . 80  |  ] ,i.  _ j „ .  T a b l e 11. T h e a v e r a g e s i z e a n d v a r i a t i o n i n length of mysids consumed by t h e d i f f e r e n t experimental g r o u p s . M y s i d s were p o o l e d from stomachs o f a l l f i s h from t h e two i n t r o d u c t i o n dates.  33  B e n t h i c Prey. Sjyy>les  A summary  of  the  plankton  net,  Table  To d e t e r m i n e  12.  analysis  the  square  root  July  of  species  chironomid  time  numerous  the  tidal  creek  applied  to  the data  a  was  most  was  analysis and  indicate  sampling  the  2-way  performed organisms  (Table  13). A  normalize pooled  ,  can  the  for July  than  the  variation weeks.,  species  apparent  Snorimosphaeroma creek caught 14.  (Table  to d i e l  variation,  i n amphipod numbers,  in  i n ; the  (July  well  as  sampling vertical  Anisogammarus ,  and  suspended  the  f o r the  basket latter  ( t - v a l u e = 27. 406,P < 12-16) , i t i s e v i d e n t  there e x i s t s  probably  in  12).,  Since the values  4-day s a m p l e s  and  to a d i e l  Oregonensis  16-20) a r e much h i g h e r  initial  , in addition  of  as  13 The  differences  vs.night)  be a t t r i b u t e d  especially  a r e shown i n T a b l e (July  (day  interaction  differences is  significant  times  l a r v a e i n the t i d a l  4-day s a m p l e s  or  in  effects  four  of  numbers o f amphipods  samplers  that  diel  sampling  s a m p l e v a l u e s , and  which  confervjcolus  The  the  caught  the i n t r o d u c t i o n s i s given i n  magnitude of  margin  first-order  These  migration  0.01)  organisms  14 t o p r o v i d e an e s t i m a t e o f t h e d a y t i m e a b u n d a n c e .  significant time.  the  after  transformation  r e s u l t s of t h i s both  and  abundance o f  southern  distribution and  before  of  o f v a r i a n c e on s p e c i e s and  comparing the along  numbers  on a t i m e  a longer scale of  term days  34  1 1 r i • 1-4— r t  | SAMPLING \ TIHE(HHS) f  1 l ! T  i  \ Anisogammarus 1 confervicolas I Neomjsis I mereedis  -4-4— TT^  MORNING JULY  13/76  1 Gnorimosphaeroma 1 oreqonensis  J0LY •  0740 6  904  |  I  0750  10  0710  !  1 | 890  .11 TI  EVENING  34  I  27  Larvae  1 Corophium \ spinicorne I  II—  4  |  1  !!  Hydracarina J.J..  0720  T  I T  5  +  I JULY  19/76  !  !  1  2155 866  _ i_ T  768  _i_  104 4 _1  .. 7  82  _ 1_  _11  I Insect  • T  x _  3 984  T  1 4/76  t  J  1  1  |  1  -j—•  1  | .J. .  5  T  0  1 0  4  f 1 1 -i—  0  i  i  43  I !  ! i  0  2210  1012 844 62 •  49 |  0 a  0  T"  I  -i  1  0  "I  1  - J  T a b l e 12. Numbers o f e p i b e n t h i c i n v e r t e b r a t e s caught i n plankton tows i n e a r l y morning and l a t e evening p r i o r t o and a f t e r t i d a l creek i n t r o d u c t i o n s .  35  r  j  |  —  SOURCE  •f-  !  o?  VARIATION  |  DF  J  ,. 1 .  1  |  7 1 3 3 16  I  23 I  !  j  -  MS  -•  T"  |  | i ]  i  1 1  j I Subgroups ] Time | J Species I Time X S p e c i e s I Within (error) Total  | |  SS  T  3786*0768 505. 0519 2639.4947 641.5302 29.0583  505.0519 879.8316 213. 8434 I 1.8161  3815.1351  1  *  | } |  F  J  | 278.0907 * * I I 484.4512 ** | | 117.746 1 ** | i  1 .  .J—  ;.  1 „  1  **=P < .01 T a b l e 13. Two-way a n a l y s i s o f v a r i a n c e on numbers of benthic organisms collected i n the plankton net a t d i f f e r e n t sampling t i m e s . A s g u a r e r o o t t r a n s f o r m a t i o n was p e r f o r m e d a n d o n l y t h e four most abundant groups Anisogaamarias , Neomvsis , Gnorimosphaeroma . and i n s e c t larvae were considered i n the analysis..  SAMPLING DATES  JULY  12-20 1976  JULY  12-16 1976  STANDARD DEVIATION  16-20 1976  I  NO. OF REPLICATES MEAN NO. OF AMPHIPODS PER GRAM DRY WEIGHT OF FUCUS  I JULY |  6.8  1.1  6.7  3.25  0.07  0. 28  Table 14. Numbers o f amphipods caught i n basket traps before introductions.  p e r gram d r y w e i g h t o f F u c u s and after tidal creek  36  DISCUSSION  E f f e c t s Of  Experience  Experience  i n the f i s h c o n d i t i o n e d to f e e d on Neomvsis f o r  30 days before t h e i r  introduction  manifested  by  i n the d i e t  (Figs.7 and  to  into  G-value  c o n s t i t u t e s evidence treatment  groups.  8) than those groups of f i s h  for  the  through  the  f o r an e f f e c t of The  results  feeding  learning,  food.  CxPxO  of  demonstrate t h a t experience with a increases  tidal  creek  was  the f i s h a c q u i r i n g a l a r g e r p r o p o r t i o n of mysids  feed on e i t h e r amphipods o r p e l l e t  significant  the  ability  relative  conditioning  a  other  prey  7)  across  palatable predator  the  (Table  experiment  given  to  addition,  interaction  the  of  In  conditioned  all  therefore prey  type  on t h a t prey,  types  in  the  environment. The  lack  of  a  higher p r o p o r t i o n of Anisoqammarus i n the  d i e t of the amphipod-conditioned experimental  groups  <Figs.7 ;  g e n e r a l i z a t i o n . There are occurred. F i r s t , fish  would  fish  several  and  compared 8)  possible  the  other  contradicts  this  reasons  this  why  i f Anisoqamm ar us i s r e l a t i v e l y u n p a l a t a b l e ,  not be expected  to improve t h e i r f e e d i n g a b i l i t y  t h i s prey type. Second, the amphipod-conditioned would  to  not show an i n c r e a s e i n f e e d i n g a b i l i t y  the d e n s i t y of Anisogammarus i s very low  fish  the on  probably  on amphipods when  relative  to  alternate  prey. Thus i f amphipods were r e l a t i v e l y u n a v a i l a b l e i n the t i d a l creek  at  the  time  of the i n t r o d u c t i o n , a c o n d i t i o n i n g e f f e c t  37  might n o t  be a p p a r e n t .  alternative  i s unlikely.  chum salmon i n t h e Goodman  There  and  are s e v e r a l  other e s t u a r i e s  D u n f o r d , 1975)  makes up a h i g h p r o p o r t i o n o f t h e i r were r e l a t i v e l y be  expected  t o a c q u i r e a lower  be  groups,  expected  (Holling,1965), comparison  the  to  groups  decreased  responsiveness  and  sufficient  express  of  occur  documented  of  avoid  could  on  persist  prey  shows  item not  would  no  prey  available. with  and  evidence fish  for  leaves  a  towards low  but  contention  present i n the  A  the other  groups i n the  the  unpalatable  in  other  fish  that  open tidal  the creek  fish  to  s p e c i e s h a v e been  l a b o r a t o r y s t u d i e s ( I v l e v , 1961; and  and  different  a  field  prey  items  half  more c a p a b l e  and  Beukema,1968;  study  L a r k i n showed, by  for at least  becoming  fish  amphipod-conditioned  (Bryan  repeatedly that  that t h i s  and  sampling  individuals  specialization  a year. Thus t h e s e  repeatedly harvesting a small subset t y p e s and  species  fish  were  t h e stomach c o n t e n t s o f marked r a i n b o w t r o u t , specialized  6;  the  fish  supports  the  experience  Bryan  and  effect.  Bryan,1973)  Larkin,1972).  by  amphipods  experience,  i n a l l treatment  abundance f o r  i n both  Ware,1971;  i f  amphipod-conditioned  t h e s p e c i e s was  a conditioning  Effects  Also,  prey  8)  p r o p o r t i o n s . ,:• T h i s  that  to  alternate  Anispgammarus i s a p a l a t a b l e  in  (Figs.5  at times t h i s  diet.  with  learn  (Figs.7  amphipods- t h e s e p r e y  possibility  and  amphipod-conditioned  treatment  first  p r o p o r t i o n of amphipods t h a n  since,  provided  of  equivalent  the  u n p a l a t a b l e , the amphipod-conditioned  other experimental would  why  Anisogammarus i s a c c e p t a b l e a s f o o d  Squamish and  Vroom, 1972;  reasons  of the t o t a l  a t f e e d i n g on t h o s e  animals set prey  of  were food  animals  38  Ivlev  (1961)  reported  that  in  t r a i n i n g p e r i o d s has an i n f l u e n c e on  carp, the  the number o f p r i o r electivity  value,  E  ( p r o p o r t i o n of food i n the d i e t r e l a t i v e to t h e environment) and that  "the  h a b i t of feeding on c e r t a i n food c o n t i n u e s even with  the o p t i o n o f a much wider  choice."  (1968)  with  demonstrated  that  In  sticklebacks,  experience,  the  Beukema  r i s k t o prey  i n c r e a s e d due t o a higher chance of d i s c o v e r y a f t e r the prey had been p r e v i o u s l y encountered.  In a d d i t i o n , the f i s h  became  r e s p o n s i v e t o i n e d i b l e o b j e c t s which resembled the prey. on  rainbow  Studies  t r o u t show t h a t t r o u t can develop a " t r a i n i n g b i a s "  (Bryan,1973). T h i s familiar  more  means  that  when  given  a  choice  between  and novel food, the f i s h w i l l a c q u i r e t h e type of food  t h a t they have eaten p r e v i o u s l y . Ware (1971) , a l s o working with rainbow t r o u t , r e p o r t e d t h a t experimental responsive  animals  t o t h e prey t h a t they had experienced  became  more  p r e v i o u s l y due  t o an i n c r e a s e i n the r e a c t i v e d i s t a n c e o f the f i s h f o r t h e prey type. Only a low l e v e l o f reinforcement was  necessary  f o r the f i s h  and Ware suggests t h a t trout  allow  polymorphic In  them  the  to  (6 encounters/48  to show an i n c r e a s e d characteristics  learn  to  discover  hours)  responsiveness  shown  by  rainbow  relatively  scarce  prey.  addition  circumstantial  to  the  evidence  listed  from  a  studies,  there  study by LeBrasseur  j u v e n i l e chum salmon which supports the  (1969) on increased  on p r e v i o u s l y experienced prey t y p e s .  LeBrasseur  used d i f f e r e n t s i z e - g r o u p s o f s o r t e d l i v e zooplankton  i n feeding  and by  of  some  an  feeding a b i l i t y  idea  is  growth s t u d i e s and found t h a t euphausiids were a c q u i r e d o n l y fish  which  had  previously  f e d on  euphausiids.  Thus  39  LeBrasseur's  findings  a r e i n accordance  tidal  creek experiment  learn  to  increase  experienced  prey  which show t h a t  their  feeding  with the r e s u l t s juvenile  ability  of  the  chum salmon c a n  on  a  previously  type.  D u r i n g t h e b e h a v i o u r a l c y c l e w h i c h makes up a p r e d a t o r - p r e y interaction,  the  following  components  are  involved  IdeHuiter,1966): 1) S e a r c h of  prey  stimuli  that  inform predator as to exact  location  are absent  2) A p p r o a c h - l o c a t i o n  o f prey  known, prey  outside  grasping  range 3) Capture^-  prey  within grasping  range  4) I n g e s t i o n - c o n t a c t s t i m u l a t i o n To  assess  the  mechanism  predator's feeding a b i l i t y , in  feeding a b i l i t y  hypotheses experience of  time  lags  that  i s mediated  several  the  through  Tinbergen perceptual their  change  in  feeding a b i l i t y  an i n c r e a s e d s e a r c h i n g  of  subsequent songbirds,  (1960). T i n b e r g e n change  on  searching a b i l i t y  the  Most with  efficiency  prey. to  the the occurrence o f insect  their  species  t o r e l a t e t h e change  e x p l a n a t i o n w h i c h was i n v o k e d  between  abundance, and  experience increases a  t o one o r more o f t h e a b o v e c o m p o n e n t s .  suggest  earliest  whereby  prey  i t i s necessary  the predator f o r a s p e c i f i c The  from  appearance P ar us  invokes part  a  sp.  the  mechanism  prey.  food  was p r o p o s e d  The  of by  involving  o f t h e p r e d a t o r which  for a particular  for  l a r v a e i n high  in ,  account  affects  "searching  image h y p o t h e s i s " a s s u m e s : 1)that s p e c i f i c  c h a r a c t e r s a r e used  a  i n t h e s e a r c h f o r prey;  40  2) t h a t of  these  learning  "specific  process  searching  3) t h a t searching the  one  by  characters a r e a s s i m i l a t e d i n a kind  means  member  of  a  pair  are  reaching  thought  their  ability  place  (1971)  to  retina,  for  domestic  chicks  can  coloured  proposed  adopt  prey  adopts  a  the  collected  a new  can  of  by  out  visual  increase  their  searching  conditioning  s p e c i e s o f prey.  evidence  showing  improve  filter  Adoption of a  a process  by  their  that  Dawkins  c o n s i s t e n t with  that  with  searching  g r a i n , and t h a t t h i s  (1970) c r i t i c i z e d an  alternate  efficiency  repeatedly  is  of g r e a t  acq.ui.re a s f o o d .  learns to r e s t r i c t  habitat,  and a c q u i r e s  m o r e - o r - l e s s random necessity that  tits  to on  the  experience ability  likely  due  for to  a  the  insect  effort  developed  responsive  to  a  predisposed  t o capture  increased  larvae  types  in a  particular  that prey.  c e r t a i n prey  in particular  the  predator  Rather, due t o i t s  habitats.  a  particular  Onder Royama^s h y p o t h e s i s  or  they  occurring there i n a  a s i e v i n g mechanism o f t h e v i s u a l  be  and  t o Royama's h y p o t h e s i s ,  i t s searching  fashion.  image h y p o t h e s i s  explain the  According  a l l o f t h e prey  the r e t i n a  effort  the searching  mechanism  predator  searching  birds  change.  Hoyama  no  thus  prey.  some e x p e r i m e n t a l  image h y p o t h e s i s "  searching  and  specific  "searching  perceptual  the  selectively  a f t e r encounters with  provided  cryptically  the  {ma t i n g - p a i r ) ,  when s e e i n g  image i s t h o u g h t t o be t h r o u g h takes  which  f  Predators  searching  of  image", and  image o f i t s mate  latter.  stimuli  specific  the  there  is  stimuli via become predator  more i s  disproportionate  41  a  series  covered  by  (1970)  to  of  experiments  mussel  shells  assess  of  croze  searching  formation  learning prey,  image  interprets  w e l l as t h e  but  the t i d a l  his  juvenile  salmon to  learned  maximize  where  their  of  searching  where t h e  prey  a s s o c i a t e d with  creek). to  {eg,sedge  Thus, assuming  raicrohabitat  thought from  the  fish  morphology t o be  at  olfactory  that the  visual  least  one  fish  of  the  preyi  predators  were  experienced  the  experiments  juvenile  for  olfactory conditioned  food.  experiment  to  by  particular sediment  could not  were  that  since  as i n the learn  to  there et  is  the  respond the  only  with  the  that in  had the  learning prey  types  to on  are  evidence  al.,1962)  as  of  tidal  j u v e n i l e salmon  that  salmon. 1 part i n  previously tidal  chum s a l m o n c o u l d i m p r o v e t h e i r  emerging from  all  features  i n j u v e n i l e sockeye  fish  the  searching  associated  Although  It i s possible that  by  jointly  i n l a b o r a t o r y tanks  (McBride  prey  feed.  efficiency,  a t c o n c e n t r a t i o n s a s low  detectable  particular  cues  unlikely  (Hoar,1958)  perception i s significant  80;000,000,  is  i n the l a b o r a t o r y tanks,  could learn  E x t r a c t s of n a t u r a l foods,  ability  or  the  Image."  occurred  rhizomes  differences  characteristics specific  prey  of  "form  to concentrate t h e i r  with  habitat  characters  l e a r n e d and  it  experiences a r e not  behaviour  acknowledges the importance  experiments  in  Croze  of  previous  the  results  bait  terms  of a S e a r c h i n g  creek  allowed  crows' s e a r c h i n g  h a b i t a t are both  the p e r c e p t u a l template  effort  i n the  colour  where t o s e a r c h . T h u s t h e s p e c i f i c  as  In  different  t h e change  with experience,  on c a r r i o n c r o w s f e e d i n g on  creek  searching  discriminate which t h e y  were  42  The  d i s c u s s i o n thus f a r c o n s i d e r s the  experience  on  the  searching  behaviour  t h e i n t e r a c t i o n s between e x p e r i e n c e of  predation  ingestion.  i n the  An  attributable as t h e  "handling  conditioning  behaviour  the  mouths  that  Alternatively, way caused  thorax  thus  schedule the  they  amphipods  of  to  feed  on  compares  the  predator, responsive  of then  size  size  were  repeatedly  the  observed  items.  on  change  region  of the  a  their  head-first.  more  in  buccal  onto  the  easily  i n g e s t e d and  e x p e l l e d from  increased,  This suggests  Further  when  that  conditioned  support 11.  perceptual  c o n d i t i o n e d to feed  on  t o w a r d s s m a l l e r , more c r y p t i c  the  juvenile  for  This  of ingested mysids..If  the  the  conditioning  are the r e s u l t s i n Table  distribution  the  the  handling e f f i c i e n c y  prey  of to  down  number o f e x p e r i e n c e s decreased.  or  creating of  of  mysids i n  fold  the  amphipods. With  expansion  beginning  in  size  mid-dorsal  to  and  the  experience fish  mysid  and  formulated  course  m y s i d s and  in the  be  used  ingested t a i l - f i r s t  Near  specific  hypothesis"  effect  its  their  "handling  an  were  expulsions  chum s a l m o n - i n c r e a s e  were  s u c t i o n c r e a t e d by  reducing  the  ,  experience  to the  l e a r n e d t o manipulate  t h e abdomen o f t h e  particle.  During  towards both  components  with  items  of  ignores  approach, capture  prey  salmon  and  handling  ability  live  m y s i d s were g r a s p e d  mouth. However, a s  freguency  the  predators  that the  cavity  ingestible  The  (Fig.3).  treatments,  handling  a  feeding  hypothesis".  predator  experience,  such  the  e x p e r i m e n t s were l a r g e r e l a t i v e  j u v e n i l e salmon  so  and  to a g r e a t e r h a n d l i n g e f f i c i e n c y can  conditioning  their  in  effects  of predators  behavioural cycle:  increase  possible  table  there i s  ability  of  mysids s h o u l d individuals,  the  the  be more  than  fish  43  conditioned  on f i s h p e l l e t s  or  amphipods.  The  observed  size  d i s t r i b u t i o n however, i s o p p o s i t e t h a t p r e d i c t e d on the b a s i s of perceptual to  discriminatory  J u v e n i l e salmon c o n d i t i o n e d  feed on mysids attacked l a r g e r mysids i n the t i d a l creek  other  treatment  experienced  groups.  This  supports  the  than  hypothesis  that  f i s h l e a r n e d to manipulate the prey b e t t e r than f i s h  conditioned  on  distribution  other  of  large-amphipod to  ability.  food  ingested  types.  ft  amphipods  conditioned  comparison for  the  groups of f i s h :was  the s m a l l number of amphipods eaten by the  of the s i z e small-  and  not p o s s i b l e fish  during  due the  t i d a l creek i n t r o d u c t i o n s .  Prey  Many  flyailability  field  In The  studies  T i d a l Creek  dealing  with the feeding of f i s h  concerned with making i n f e r e n c e s about  prey  availability  p e r c e i v e d abundance of prey organisms t o the f i s h ) . Allen  (1941)  defines absolute a v a i l a b i l i t y  (the  For example,  as the p r o p o r t i o n of  the p o p u l a t i o n which, i n a t y p i c a l h a b i t a t would be v i s i b l e and of s u i t a b l e s i z e and under  consideration,  consideration. detailed  Any  t a s t e t o be eaten by a f i s h  if  the  estimate  understandinq  of  fish of a  had  this  the number, behaviour, environment.  Field  and  the  by Hyatt  type under  requires  a  physiological  and  accurate  assessment  of  d i s t r i b u t i o n a l p a t t e r n of prey i n the  investigators  rarely,  if  ever, have t h i s  i n f o r m a t i o n at t h e i r d i s p o s a l . More o p e r a t i o n a l terms have defined  to,  of the  whole area  parameter  predators*  b e h a v i o u r a l c a p a b i l i t i e s as w e l l as an  are  {in press)  who  defined " r e a l i z e d  been  availability"  to  i n d i c a t e the prey  of  predators, " p o t e n t i a l  organisms can  are  interval, of the  capable  as  present  i n g e s t , and  w e l l as " a p p a r e n t that  present  of  i n the d i e t  availability"  handle,  organisms  physically  present  physically  detect, capture,  time all  that  items  and  detecting,  appear which  as  that  set  and  which t h e  an  sample  of  a  given  to r e f e r  investigator  he t h i n k s t h e  predator  handling,  prey  predators  assimilate in  availability"  to  capturing,  of a given  to  to be  should  ingesting,  be and  assimilating. Perusal ( F i g s . 7 and was  of 8)  higher  treatment  shows t h a t t h e  groups.  second The  (Table  i n t r o d u c t i o n date  9)  creek  on  low  with  mysids over variable  each  mysid  Conseguently, daily  availability  time  density  and  the  i t  16)  3-way  occurrence  a  of  for a l l  and  scale in  is  ebbing probably  the  tidal  availability  out  tide.  Thus  of mysids i n  In c o n t r a s t to  of  for  the  tide tidal  This migration in  from  a  that  day  the  of  highly to  day.  m y s i d s c h a n g e s on  understandable  o f mysids i s d i f f e r e n t  of  results creek  of  significant  mysids.  availability  i n t r o d u c t i o n dates.  diet  G-test  t h e r e was  Neomysis moves i n and  the p o t e n t i a l  basis,  that  (July  the  n e a r t h e s e d g e r h i z o m e s when t h e  flowing  a short  the  realized  t h e two  (Levings,1973),  from  confirm  a d i f f e r e n c e i n the  tidal  creek  p r o p o r t i o n of m y s i d s i n  results  anisogammarus which r e m a i n is  from t h e s t o m a c h c o n t e n t a n a l y s i s  o f i n t r o d u c t i o n . d a t e on  t h e r e was the  results  on * t h e  independence effect  the  a  realized  the  two  introduction  of  the  tidal  dates. One  of  introductions  the was  unanticipated the  low  results  freguency  of  Anisogammarus  creek in  the  45  diet,  particularly  creek  showed t h i s  crustaceans creek,  14)  a  there  that  introductions. shows  amphipod t o be  were c e r t a i n l y  although  (Table  difference  sampling  variance  (Table  and  times 13)  Columbia  Davis  River  vertically  a  d e v i c e , an  1600  2400 h o u r s .  and  of  the  Moreover, t h i s which one sampled hours  diel  observes in  basis  that  and  was  then  evacuation evacuation  peak  on  of at  the e s t u a r y  12.8°C was  the corresponding  the  trap time  data  the effect.  migration  than  evacuation  from  Anisoqammarus  slack tide  i s valid  Since  migration  between tidal  absence  chum  period  salmon  (1600-2400  unavailable to the  stomachs  (Figs.5  and  were e a t e n  information  the  stomachs  12.8°C on rate  rate  indicates a  10  6) 6-17 of hour  temperature  most s a m p l i n g  therefore  fish.  amphipods  (060 0-0900 h o u r s ) on  the  their  f o r the  juvenile  for  migrates  most v u l n e r a b l e t o a low  of  pattern,  evidence  ( B a i l e y e t a l . ,1975) . S i n c e t h e  lower  12)  as f o o d  salmon  fry  the  Thus, i t i s  in  salmon  of  analysis  pattern i m p l i e s t h a t the  chum  data  (Table  migration  Available  chum  tidal  i t would e x p l a i n t h e  were a p p a r e n t l y  t h e morning hours  previously.  in  time  If this relationship  amphipods  of the  a b u n d a n c e o f amphipods a t  (1976) p r e s e n t  amphipods i n t h e s t o m a c h c o n t e n t s .  hours)  of  Holton  the  These  potential availability  epibenthic sled,  after  tow  tidal  item.  basket  at  a strong d i e l  i n the Sguamish e s t u a r y ,  were i n t r o d u c e d  low  the  food  the  plankton  t h a t shows  diel  sampling  from  was  from the  vicinity  t h i s shows up  their  and  Estuary  on  i n the  as a s i g n i f i c a n t  this affects  Recently  creek  and  in  t h a t Anisogammarns has  that  fish.  of the  fish  important  present  density  Examination  marked  an  i s a suggestion  their  different  likely  s i n c e r e g u l a r samples of  longer  dates,  and  than  10  46  hours,  the  data  are  amphipods o b s e r v e d acquired  consistent  in  the  with the hypothesis t h a t the  stomachs  on t h e e v e n i n g b e f o r e  of  chum  juveniles  were  sampling.  Food Of. Clvum Salmgn I n The Squamish E s t u a r y .  The  results  the t i d a l and  creek  although  terrestrial an  o f t h e stomach a n a l y s i s o f f i e l d  ( F i g s . 5 and 6) show much certain  insects)  understanding  predict  size  might  diet  over time  second  in  the  reason  they might  mechanism.  during i n diet  predator  Thus  as  exclude s m a l l e r organisms  proportion of large  (large reason  prey) for  i s evidence  forms.  of c y c l o p o i d s (small  a  (Murdoch  that, at least  et  the from The prey)  volume  mechanism.  change i n the p r o p o r t i o n o f d i f f e r e n t  might  be due t o a c h a n g e i n t h e p o t e n t i a l  o f the d i f f e r e n t  sensitive  supporting t h i s  for  predator  ( F i g s . 5 and 6 ) , and t h e i n c r e a s e i n t h e p e r c e n t  availability  types  switch"  percent frequency  components i n t h e d i e t  are quite  possible  be used t o  p e r i o d s ( T a b l e 2) . t h e d i f f e r e n c e  "developmental  ° f H§2I2§i§ A  on one o c c a s i o n c a n n o t  and i n c l u d e a h i g h e r  reduction  proportions,  a change i n t h e f e e d i n g b e h a v i o u r o f t h e  a  time,  S i n c e t h e j u v e n i l e chums were l a r g e r  two s a m p l i n g  from  Anisogammarus and  occur repeatedly i n d i f f e r e n t  p r e d a t o r s grew l a r g e r , their  with  c h a n g e s i s due t o t h e r e l a t i o n s h i p between  reflect  through  (eg.  f e e d i n g b e h a v i o u r . One  and p r e y s i z e .  the l a t t e r  variation  organisms  of the diet  subsequent  the observed  prey  samples  prey t y p e s . F i s h  to changes i n t h e d e n s i t y al.,1975)  i n the laboratory of alternate  and t h e r e s u l t s i n T a b l e  f o r some p r e y o r g a n i s m s ,  prey  11 show  there are differences i n  47  their  potential  creek,  both  potential  availability.  the developmental  availability  variability  in  Since  Neomysis  dominant,  tidal  creek  surprising proportion account prey  of p r e y  was  i t was  on  all  that  this  f o r a low by  mechanism, and  types  contributed  observed of  from the  is  the p e r s i s t e n c e of  migrates  m i g h t be  results  the estuary  f o r the  variability  i n the  of  exploit  prey  make  i f  highly  prey  greater  patterns parts  an  area  spatial  to  t o become over of  might e f f e c t i v e l y  and  is  profitable  type  different  in  the  it  up a  in not  mechanism  distribution  temporal  the  fish  on  first  stomach the  to  prey in  time.  two  the  allow  of  high  variability,  Since  a  search  of  the  the  be  period  are a  more  i n t r o d u c t i o n dates  these  types  fish, a  analysis  o f n a i v e chum  number o f p r e y  likely of  type  12),  f o r j u v e n i l e chum salmon t o f o r m  prey-conditioned  diversity  the  density  used a s a s i m u l a t i o n o f t h e d i e t  estuary i s  high  prey.  pellet-conditioned  live  the  food  {Table  apparently  stages, t h i s  to their  difficult  image f o r t h e s e The  changed  important,  not  into  a h i g h , prey  d e n s i t y . Due  an  s a m p l e s . One  for  Neomy.sis  estuary at successive t i d a l  did  o f an  time.  it  the  tidal  i n v e r t e b r a t e biomass i n  field  i n i t s a b u n d a n c e and  predator  the  to  acceptable  occasions  crustacean  predator,  an  t o be  the  sampling  utilization  a  t o be  unpredictable Since  in  switch  found  constituent  of the d i e t  type  that  diet.  t h e l a b o r a t o r y and the  It is likely  fry  initial when  feeding  g r o u p s show a  consumed  can  {Table  in  higher  10)  than  e n t r y of f r y i n t o a  relatively  the high  aguired. Naive predators are l i k e l y random  fashion  than  be  to  experienced  48  predators, formation  until  of a search  searching foraging  images ability  controlled search  a  by  significance,  possess  number  of  affects i t s  , and t h i s  (Hare,1971),  can  be s i m u l t a n e o u s l y  will  be  Mendelson  feeding  habits  four sympatric  f o r the prey  the d i s t a n c e of r e a c t i o n type  i t  is  conditioned  many s e a r c h  (1975) p u b l i s h e d a d e t a i l e d  images  account  of  o f t h e minnow Notrop.is i n p o o l s o f Roxbury aim was t o a s s e s s suggests  mechanisms t h a t a l l o w  and t h e y  crows  image, b u t i n r a i n b o w  I t i s n o t known how  s p e c i e s . , He  Predators  that  r e t a i n e d by f i s h .  Recently  C r e e k , Wisconsin....His  indicates  one s e a r c h  does not a f f e c t  predator  feed  prey,  can  evidence  more t h a n  food  to  1)  predator  Available  alternate  alternative  a  the  cause the  t h e r e l a t i v e r a t e s o f l e a r n i n g and f o r g e t t i n g o f  o f an e x p e r i e n c e d  the  image. ., Of  that  ( C r o z e , 1 9 7 0 ) c a n form  on  number o f e n c o u n t e r s  i n t h e n a t u r a l environment  images.  trout,  sufficient  a r e adapted  freguent  resource the  following  possible  coexistence:  to the capture  certain  partitioning i n  of specific  places because t h e i r  kinds of  prey  reside  there. 2) P r e d a t o r s in they  which prey  they  a r e adapted t o p a r t i c u l a r h a b i t a t s , f u n c t i o n most e f f e c t i v e l y ,  indiscriminately  on w h a t e v e r  to  regions  and i n t h e s e  animals  of  a  regions suitable  size are available.,  and  On  the  basis of the s p a t i a l  distribution  prey  and  an  stomach  concludes results  that  examination t h e second  o f many f i e l d  of  alternative  of the predators  contents,  i s more l i k e l y .  and l a b o r a t o r y s t u d i e s  (eg.  Mendelson From t h e  Beukema,1968;  49  Ivlev,1961)  however,  the  evidence  Mendelson's c o n c l u s i o n , f i s h feeding  patterns  and  are highly  rarely,if  i n a density-dependent  tidal  creek  experiments  c a n be  c o n d i t i o n e d t o respond  present study reassessment  i n the t i d a l strongly  of the  in  differently Thus,  that  similar  in  results  alternative  and  the  predators  t o an i d e n t i c a l the  their animals  fashion..Moreover,  favour the f i r s t  problem.,  c o n t r a r y to  discriminate  I demonstrated  creek.  that,  ever, a c q u i r e whatever  are available  food organisms  suggests  set of of  the  demand a  50  L I T E S A I f l l E CITED  Allen,K.R.  1941. S t u d i e s on t h e b i o l o g y o f t h e e a r l y s t a g e s o f t h e s a l m o n ( S a l m o s a l a r ) . J . Anim. E c o l . 10:47-76.  Bailey,J.E.,B.L.Wing and C.R.Mattson. 1975. 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F u n d a m e n t a l s Royama,T.  fish schools for conditioned A n i m a l B e h a v i o u r 8:22 5-22 7.  o f E c o l o g y . W.B.Saunders.  574p.  1970. Factors governing t h e h u n t i n g b e h a v i o u r and s e l e c t i o n o f f o o d by t h e g r e a t t i t . P a r u s major . J. Anim. E c o l . 39:619-668.  deRuiter,L. 1966. Feeding behaviour of v e r t e b r a t e s i n t h e natural environment. In Handbook of Physiology { A m . f h y s i o l . S o c ) S e c t i o n 6: 96-116. S o k a l and R o h l f . 1969. B i o m e t r y .  W.H.Freeman. 776p.,  Sparrow,R.A.H. 1968. A f i r s t r e p o r t o f chum s a l m o n f r y f e e d i n g i n f r e s h w a t e r o f B r i t i s h Columbia. J . F i s h . Res. Board Can. , 25:599-602. Tinbergen,L."...1960. The n a t u r a l c o n t r o l o f i n s e c t s i n p i n e w o o d s . I. F a c t o r s i n f l u e n c i n g t h e i n t e n s i t y o f p r e d a t i o n by s o n g b i r d s . A r c h . N e e r l . Z o o l . 13:265-343. Ware,D.M. 1971. The p r e d a t o r y b e h a v i o u r o f r a i n b o w t r o u t (Salmo g a i r d n e r i ) . Ph.D. T h e s i s . Dept. Zoology. Univ. Of B . C . , V a n c o u v e r , B.C. 185p.  APPENDICES  54 A P P E N D I X I. D i e t of e x p e r i m e n t a l f i s h r e l e a s e d i n t o the t i d a l c r e e k on J u l y 15/7 6. 100  100  % FREQUENCY  75.1 50.  50  £5.1  25.1  0  1 — F = h = 1 — h -I—I—I i . E« 3- 4- 5- 6« 7- 8. a.10.  FREQUENCY  i» £• 3. 4> 5. G> 7. B- 9-10. 100.  IJOO.  % OCCURRENCE  75...  % OCCURRENCE  75.|  50.  SO.  E54  ES-1  0  %  75-1  O !•  1. E- 3« 4. 5. E< 7- 8- 9-10.  B' 3« 4« 5. 6« 7« 8' 9>10-  100.  lOOv  % VOLUME  75  % VOLUME  75..  50-1  50-..  ES.  £5.1  H—-I—I—I H h 1. E- 3- 4. 5- B. 7- B- 9-10.  1. £• 3- 4. 5. B- 7- 8- 9-10.  PREY TYPE  • PREY TYPE MYSID 2-day July 15/76 N = 17  c  3 0.  E  „  E E  SMALL AMPH 2- day July 15/76 N = 13  x. u a U o J I—i—i—i—I—I—l—i—i—i—i 5. G- 7- B- 9-10. 1. E» 3'  PREY TYPE Diet of juvenile chum salmon conditioned to feed on mysids and small amphipods (2-day food deprivation) during first tidal creek introduction- July 15/76.  55 A P P E N D I X I. [ C O N T ' D ]  1O0.  1D0-  % FREQUENCY  75... 50...  50...  £5  E5...  0  H  h—1  1  0:~.  h  100-  100  H  1  5- 6' 7. B- 9>10.  T  75 50  ES...  ES  0  1  H  H—1 . . H—f1. E- 3> 4- 5- £• 7. B> 9 - 1 0 .  !• 2- 3« A' 5« 6- 7. B« 9«10.  100.  100v  % VOLUME  % VOLUME  75  75...  50  SO-.  254  E5..r  0  1  4.  % OCCURRENCE  % OCCURRENCE  50...  0  H  1. E« 3«  !• E« 3> A' 5« 6- 7- B- 9>10.  75  % FREQUENCY  75...  .  . -i  1. E« 3-  4=1  0...  H 1 r—+H 1 !• E- 3- 4. 5. E> 7. B- 9-10.  1—I—I—I—I—I—I 4.  5. E« 7. B« 9<10-  PREY TYPE  PREY TYPE LARGE AMPH 2-day July 15/76 N=6  "2  •a  t 6  C u£ £ri  v *> a  v  o  I  « 22  J t  - -g  o o o ^  •>  e  «> ' o  o  v  •I |  o  S" S j E- E !'! E .£ 2 c 5 £ . 2 S tog  .S I 2.  C  , i  C  D  o  n  .  -  o  ;  ?  «  u  M  «  o  j  i  P  PELLET TYPE A 2- day July 15/7 6 N=7  o  >-  „  „  j •  -e J= ^ « c .° , \ ° U U U > J X < < > U 1 1 1 1 1 1 1 1 1  1 1. 2. 3> PREY 4. 5. TYPE G« 7« B« 3<10.  Diet of juvenile chum salmon conditioned to feed on large amphipods and pellet typc-A (2-day food deprivation) during first tidal creek introduction- July 15/76.  56 A P P E N D I X I. [ C O N T ' D ]  100.  100.  % FREQUENCY  % FREQUENCY  75...  75...  50...  50... 25... 1  H  2. 3. 4« 5. 6- 7- 8- 9.10-  !• 2« 3- 4. 5« 6> 7. 8- 9.10« 1O0. 75  % OCCURRENCE  50...  SO-  25...  BS •!  3=F  0  1  H  !• 2. 3. 4> 5. G> 7- 8- 9-10.  H 1 2. 3- 4- 5. 6. 7. B- 9-10.  1.  100 v  100 v 75-  % OCCURRENCE  75...  % VOLUME  % VOLUME  75  50-  50...  25.1  25... 1  H  7- 8. 9-10-  1. 2« 3^ 4«' 5. G« 7. B" 9-10.  PREY TYPE  PREY TYPE PELLET TYPE B 2-day July 15/76 N=9  PELLET TYPE A 7 -day July 15/76 N = 10  5 E •E .2 X  E E o  c  u  «  e • x. fO  Z  I  1  1 1.  o  1  o  o  x.  1  U  o o  «  s-  «  O -J 1 1 1  ?  °  o  v. X  c <  ° •= <J u  1  1  i.  1  1  2- 3- 4. 5- G- 7« B- 9-10-  PREY TYPE Diet of juvenile chum salmon conditioned to feed on pellet type-B(2-day food deprivation) and pellet type-A (7-day food deprivation) during first tidal creek introduction- July 15 /76.  APPENDIX  100  I. [ C O N T ' D ]  v  % FREQUENCY  75 50 2S.J.  0 !• E> 3« 4. 5. 6« 7.'  9.10.'  lOOv  % OCCURRENCE  75 SO B5.I  1' E« 3> 4« 5« 6. 7. B* 9«10. 100  % VOLUME  75. 50... ES... 0  <  M - n u  i ~i  i  i  i i  !• £• 3> 4. 5. B> 7. B» 9-10.  PREY TYPE PELLET TYPE B 7-day July 15/76 N=6  tl  CL —<  j t  i i  o o »p « V. o o .  fl  Z  I  c  U  H  1  1  1  !• E« 3-  U  c  J  o U  H (H 1 •+-G. 7- B« 9<10-  h5>  PREY'TYPE Diet of juvenile chum salmon conditioned to feed pellet type-B(7-day food deprivation) during first tidal creek introduction- July 15/7 6.  58 A P P E N D I X II. D i e t of e x p e r i m e n t a l f i s h r e l e a s e d i n t o the t i d a l c r e e k on J u l y 16/76.  100  100.  %  75...  }  FREQUENCY  %  FREQUENCY  75.X  50...  50. ES..: 25. !•  -F=l—I—h—1—I—I—I E« 3> 4 . 5 . £ • 7 . 8 - 9 - 1 0 .  !•  E« 3 .  -I 1 1 h 4 . 5 » G» 7 . B -  •H 1 9-10.  100.  100.  % OCCURRENCE  75...  75...  50.  SO...  E5-.  25...  !•  E> 3 «  H—I I I—I—I 4- 5 - G - 7 . B» 9 - 1 0 .  % OCCURRENCE  1-  E« 3 .  4.  -f 1 I I H 1 5 . G- 7 . 8- 9 . 1 0 .  100.  100.  % VOLUME  75...  SO...  50...  E5.  25.  1-  % VOLUME  75...  H 1—h H—I E« 3 « 4« 5 . G> 7« B> 9 . 1 0 -  =1 1 I 1 1 1 1-—l £ • 3 - 4- 5 . G - 7 . S- 9 . 1 0 .  !•  PREY. TYPE  PREY TYPE MYSID 2-day July 16/76 N=27  u  u  £  .a. S £ v  £ £2£  O 0 o C C D . - ;  t»  Z  t  1.  0 v  0  £  ?  » rt ™ _ a-5 »  £  c  •S 2 I °" • a. E GO  « - s* c  U O o o u J H 1 1 h H h £ • 3 . 4 . 5 . G . 7 . B« 9 - 1 0 .  H  I-  0  .c .c  s  SI/ALL AMPH 2-day July 16/76 N = 27  PREY TYPE Diet of juvenile chum salmon conditioned to feed on mysids and small amphipods (2-day food deprivation) during second tidal creek introduction- July 16/76.  59 A P P E N D I X II. [ C O N T ' D ]  100 v  100  %  75.  FREQUENCY  so.1  50-..  ES.  ES..  0-  -i—I •i 5-1 E« h 7- B. 9.101. E« 3' 4.  FREQUENCY  =1  1« E« 3.  100.  4.  1  1  >—I  1  1  5. B> 7- 8- 9-10-  100.  75...  %  OCCURRENCE  SO-  E5._  ES.  1" E« 3-  %  75-.  50...  OCCURRENCE  1  S. 6« 7. B- 9-10.  4-  !• E« 3-  100. 75>.  %  75-..  4.  P=l  1—I  5- 6» 7- B- 9«10.  100.^  %  VOLUME  %  75  50.  50...  ES.I  ES-.r  !• E» 3-  4.I  r~i  i  5-I G>I 7. B> 9-10  VOLUME  1=1-+.-I  1  1- E« 3-  PREY TYPE  4-  1 r—( 1 1 5- 6. 7. B' 9>10.  PREY T Y P E o  LARGE AMPH 2- day July 16/76 N = 15  E E .2 c E o  O  O  c  c a  U  H  1  O 1 1  !• E« 3-  4-  -Eg  O  "3  rt  1  E °  rt  y  1  o £  PELLET TYPE A 2-day July 16/76  N=l 5  M  c o C X <. U O 1  1  1  1  5. 6- 7. B- 9-10.  PREY TYPE  Diet of juvenile chum salmon conditioned to feed on large amphipods and pellet type-A (2-day food deprivation) during second tidal creek introduction- July 16/76.  60 APPENDIX  100  II.  [CONT'D]  too.  V  %  75  FREQUENCY  SO  50...  55.1  25...  0  -i 1 1 1 1 I I !• £ • 3- 4 . 5« G- 7. 8- 9.10-  0..:  100.,.  %  OCCURRENCE  i 1 H 1 I I !• 2- 3- 4 - 5« 6> 7. B> 9-10  50...  ES...  25v.  0  %  75...  50...  0...  -f=F  I  100-  %  VOLUME  T  %  75  50  50.1  25.1  25-t—I—(—+• !• 2- 3> 4 . 5- B« 7. 8- 9.10.  1- 2» 3-  PREY TYPE PELLET TYPE B 2-day J u l y 16/76 N=23  OCCURRENCE  H 1 I 1 1 1 . 1. g . 3 . 4 . 5. E- 7. 8- 9 « 1 0 .  !• 2« 3« 4 « 5« 6* 7« 8. 9«10«  75.|  FREQUENCY  100.  75  100.  %  75...  VOLUME  H-  -+-  H  h  5- E> 7. B> 9'10-  PREY TYPE •PELLET T Y P E A 7 -day J u l y 16/76 N=6  3  P.  E  i t o  Z  E O.  6 o  o H  X.  X. >•  u  o o  L.  O  u  . . . U)  i.  O  u  I. C O  o  I—i—i—i—i—I—i—i—-t—^ J.. E- 3' 4. 5. G« 7. B- 9-10.  PREY"TYPE D i e t of j u v e n i l e c h u m s a l m o n c o n d i t i o n e d t o f e e d o n pellet t y p e - B ( 2 - d a y food d e p r i v a t i o n ) a n d p e l l e t t y p e - A (7-day f o o d d e p r i v a t i o n ) d u r i n g s e c o n d t i d a l c r e e k i n t r o d u c t i o n - J u l y 16/76.  A P P E N D I X II.  [CONT'D]  100. % FREQUENCY SO ES-l  H (1. E« 3« 4. S- 6- 7. 8« 9>10.  lOOv  % OCCURRENCE  75. SOE3.  m  O.  100-  H h . . . . !• £• 3« 4« 5- 6- 7- B- 9.10'  I  75.J  % VOLUME  SO55-1  - t — I — t - -t-i 1« 5« 3' A- 5. 6* 7. B> 9.10.  PREY TYPE PELLET TYPE B 7 -dayJuly 16/76 N=5  .5 £ ~  £  ... «  £ P.  £ 2  E  o  J2 u. O u u VV . I—I—I—I—I—I—I—(-  o  1. E> 3.  -I-  u o .  5- 5. 7. B- 9-10-  PREY TYPE Diet of juvenile chum salmon conditioned to feed on pellet type-B(7-day food deprivation) during second tidal creek introduction- July 16/76.  

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