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Rheotaxis in fish, with particular reference to effects of temperature and some hormones on this reaction… Keenleyside, Miles Hugh Alston 1953

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RHEOTAXIS  IN  EFFECTS  FISH,  WITH P A R T I C U L A R R E F E R E N C E T O  OF T E M P E R A T U R E  T H I S REACTION IN  AND SOME HORMONES ON  YOUNG P A C I F I C  SALMON  by  Miles  A THESIS  Hugh A l s t o n  SUBMITTED IN  Keenleyside  PARTIAL FULFILMENT  T H E R E Q U I R E M E N T S FOR T H E D E G R E E  OF  OF  MASTER OF A R T S in  the  Department of  ZOOLOGY  We a c c e p t standard degree  of  this  thesis  required  as  from  conforming  candidates  to  for  the the  MASTER OF A R T S  Members  of  the  Department  Zoology.  THE UNIVERSITY  OF B R I T I S H  April,  1953  COLUMBIA  of  ABSTRACT  Several area of  of  greatest  water.  mon a n d  This  species of turbulence  reaction  is  fish in  artificially  most  into  created  pronounced with  the currents  young  sal-  trout. Treatment  with  thyroxine,  estrogen  compounds s l i g h t l y  eoho  sockeye salmon smolt  and  swim u p s t r e a m  Elevated negative  rheotaxis  circular  currents.  increases the jump  temperatures shown b y  testosterone rate  at  upstream over  increase the  chum f r y  and  coho  and  three  which a  dam.  amount  of  smolt  in  TABLE OF CONTENTS  Page  INTRODUCTION  1  MATERIALS  6  AND METHODS  General  o f Water  6  o r Q u i e t Water  8  Responses t o C u r r e n t s  Preference  of Turbulent  M o d i f i c a t i o n of Rheotaxis Effects  o f Temperature  b y Hormone  Changes o n R h e o t a x i s  9 11 14  RESULTS General  Treatment  Responses t o C u r r e n t s  Preference f o r Flowing  o r Q u i e t Water  14 15  Hormones and R h e o t a x i s  17  T e m p e r a t u r e and R h e o t a x i s  21 23  DISCUSSION Sensory  B a s i s o f Rheotaxis  23  General  Rheotactic Reactions  26  Hormones and R h e o t a x i s  30  T h y r o i d Hormone  32  and A c t i v i t y  Gonad Hormones a n d A c t i v i t y  34  Temperature and a c t i v i t y  36  SUMMARY  3d  ACKNOWLEDGMENTS  39  LITERATURE CITED  40  APPENDIX  45  1  INTRODUCTION  In order c u r r e n t s , aquatic  not t o be c a r r i e d about p a s s i v e l y by animals are v a r i o u s l y adapted t o m a i n t a i n  p o s i t i o n i n t h e i r p a r t i c u l a r e c o l o g i c a l niches. vertebrates  can l i v e  Many i n -  i n f a s t - f l o w i n g waters, and some f i s h e s  have w e l l developed v e n t r a l sucking  s t r u c t u r e s which enable  them t o l i v e i n h i g h l y t u r b u l e n t mountain streams (Hora, 1930). The  P a c i f i c lamprey uses i t s sucking  mouth t o h o l d onto  as i t moves i n t o f r e s h water from t h e ocean t o spawn. fish,  rocks Some  such as chum and pink salmon f r y , are h i g h l y a c t i v e i n  f r e s h water and e x h i b i t a strong tendency t o swim v i g o r o u s l y a g a i n s t f a s t c u r r e n t s , thus h o l d i n g p o s i t i o n i n p a r t i c u l a r areas d u r i n g d a y l i g h t .  Other a c t i v e f i s h l i k e coho salmon  f r y show t e r r i t o r i a l behaviour and tend t o s t a y i n q u i e t e r waters where they remain c l o s e t o p a r t i c u l a r o b j e c t s i n t h e environment  (Hoar, 1951 a ) .  Swimming a g a i n s t the c u r r e n t most f i s h e s t o h o l d p o s i t i o n i n f l o w i n g not a novel  idea.  i s the method used by streams.  This i s  Such a c t i v i t y has been r e c o g n i z e d  by f i s h e r -  men and nature l o v e r s f o r a very l o n g time, and i s now u s u a l l y r e f e r r e d t o i n the s c i e n t i f i c l i t e r a t u r e as r h e o t a x i s .  A  t a x i s i s a d i r e c t e d o r i e n t a t i o n r e a c t i o n i n which movement i s towards or away from a source o f s t i m u l a t i o n (Fraenkel and Gunn, 1940).  Thus, p o s i t i v e and negative  phototaxis  a r e move-  ments by an animal s t r a i g h t towards and away from a l i g h t  2  source.  I t i s suggested here t h a t p o s i t i v e r h e o t a x i s  movement by f i s h upstream a g a i n s t negative It  rheotaxis  should  be  f i s h e s , but brates.  a current  of water,  i s swimming movements with the  emphasized t h a t r h e o t a x i s  i s not  i s a l s o e x h i b i t e d by r e p t i l e s and  Buddenbrock (1952) presents  i s the and  current.  confined t o  the  many i n v e r t e -  a b r i e f o u t l i n e of the  occurrence of r h e o t a x i s throughout the animal kingdom. One  of the aims of t h i s t h e s i s i s t o determine  how  widespread among f i s h e s i s the tendency t o swim a c t i v e l y w i t h or a g a i n s t  c u r r e n t s of water and t o determine how  the type of response i s among s e v e r a l s p e c i e s . s p e c i e s as p o s s i b l e were u t i l i z e d , and, o f experiments was  not  t o s e v e r a l questions in artificially  t h e i r behaviour  are:  Do these f i s h  a l l or most of t h e time ?  swim against  the  I f so, i s there v a r i a t i o n i s the response  or q u i e t water when both are  consistent? avail-  Is there v a r i a t i o n i n the degree of a c t i v i t y shown  by the d i f f e r e n t s p e c i e s when i n t u r b u l e n t waters ? f i s h , but was  answers  c r e a t e d t u r b u l e n t flows i n l o n g narrow t r o u g h s .  Do they p r e f e r t u r b u l e n t ?  although a l a r g e number  were sought by observing  i n the r a t e of i n i t i a l response, and  able  As many  performed w i t h each s p e c i e s , the  Some of these questions current  uniform  not  others,  jump out o f the water ?  a l s o sought between the  c u r r e n t s and  some  Some c o r r e l a t i o n  a c t i v i t y of the animals i n these  the n a t u r a l h a b i t a t i n which they are found.  o t h e r words, do young salmon t h a t show a higher  Do  In  swim about i n l a k e s and r i v e r s  degree of p o s i t i v e response i n a r t i f i c i a l  currents  3 t h a n s c u l p i n s and e e l s , which l i v e mostly on the bottom ? Many o f these questions may e v e n t u a l l y t o understand  be important  i f we  are  the mechanisms governing l o n g - d i s -  tance movements o f some f i s h .  Russell  ( 1 9 3 7 ) has shown t h a t  some marine f i s h e s r e g u l a r l y move w i t h or a g a i n s t the d i r e c t i o n o f f l o w at d i f f e r e n t times during t h e i r l i f e Such g e n e r a l i z a t i o n s do l i t t l e  t o f u r t h e r our  histories.  understanding  of the b a s i c f a c t o r s i n v o l v e d i n the d e l i c a t e balance between f i s h e s and t h e i r environment; f a c t o r s which  ..  initiate,  d i r e c t and c o n t r o l such o u t s t a n d i n g movements o f f i s h as those o c c u r r i n g i n some diadromous (Myers, 1 9 4 9 )  species.  However,  R u s s e l l ' s i d e a s do serve t o emphasize t h a t the movements of f i s h e s i n d i r e c t r e l a t i o n t o c u r r e n t s are not uncommon. The metabolism, a c t i v i t y  and d a i l y l i f e  of p o i k i l o -  thermic animals are probably governed t o a g r e a t e r extent  by  temperature  than by any o t h e r v a r i a b l e  vironment.  Such a g e n e r a l i z a t i o n need not be e l a b o r a t e d on  here.  The r e l a t i o n s h i p of temperature  i n t h e i r e x t e r n a l en-  t o the r e a c t i o n s of  f i s h e s t o c u r r e n t s i s of more p a r t i c u l a r i n t e r e s t , however, when d e a l i n g with s p e c i e s such as the P a c i f i c complicated l i f e h i s t o r i e s . understanding  salmon t h a t have  Of perhaps g r e a t e r importance  the complex of events t h a t l e a d s t o these  in  fish  moving s u c c e s s f u l l y from f r e s h t o s a l t water and back a g a i n i s the r o l e played by hormones. Tinbergen  ( 1 9 5 0 ) has d e s c r i b e d the r e p r o d u c t i o n of  the male t h r e e - s p i n e d s t i c k l e b a c k , s t a r t i n g w i t h m i g r a t i o n and ending w i t h the r e p r o d u c t i v e a c t , as an example of the  4 h i e r a r c h i c a l pattern  i n which the  nervous mechanisms under-  l y i n g i n s t i n c t i v e behaviour i s l a i d on the f a c t t h a t  out.  Emphasis i s  a p p e t i t i v e behaviour (or,  placed  i n t h i s case,  m i g r a t i o n f r o m s a l t or deep, f r e s h water i n t o shallow, f r e s h water) i s the h i g h e s t productive act. the  or  primary l e v e l of the  i n s t i n c t i v e re-  T h i s behaviour i s i n i t i a t e d by the  a c t i o n of  gonad hormone l e v e l of the blood on nervous c e n t r e s i n the  brain.  The  gradual increase  i n length  of day  i n springtime  a c t s on the  p i t u i t a r y g l a n d , which i n t u r n a c t i v a t e s the  nads of the  s t i c k l e b a c k t o secrete  hormones.  go-  i n c r e a s i n g amounts of t h e i r  T h i s i n i t i a t e s , through the b r a i n , the most gene-  r a l i z e d type of a p p e t i t i v e behaviour, i . e . m i g r a t i o n ,  which  c o n t i n u e s u n t i l c e r t a i n s i g n s t i m u l i (or r e l e a s e r s ) , of which h i g h e r temperatures i s one,  release  a more s p e c i a l i z e d type of  a p p e t i t i v e behaviour', i n t h i s case, h o l d i n g a territory.  and  defence of  Wandering about the t e r r i t o r y continues u n t i l  f u r t h e r s i g n s t i m u l i r e l e a s e the e i t h e r f i g h t i n g or nest b u i l d i n g . prime importance i n t h e  Thus, hormone l e v e l i s of  i n i t i a t i o n o f the  type of a p p e t i t i v e behaviour, and external releasers helping a l o n g proper l i n e s .  next most s p e c i a l i z e d a c t ,  most  generalized  temperature i s one  of  t o d i r e c t the behaviour o f the  Such an a n a l y s i s i s , i n p a r t ,  i n t e r n a l s t r e s s e s which l e a d t o a movement out  of one  create area  another. It has  adult  fish  s i m i l a r to  F o n t a i n e ' s (1948) t h e o r y t h a t hormonal changes i n f i s h  into  the  been suggested t h a t the  spawning m i g r a t i o n s o f  P a c i f i c salmon are b a s i c a l l y no more complicated than t h i s  5 reproductive  migration  of  might  too  then,  not  movement  be of  rash,  young  hierarchically which  are  mones  and by  salmon i s  organized  activated  similar  not  been  attempted  has  made  many  to  of  our  stickleback to  by  stimuli  these  nervous  work  to  our  of  part  conducted.  what  extent  and whether Secondly, estrogen in  the  activities  of  positive  and  both  the  effects  of  water  was  considered  ing  the  of  rheotactic  were  fishes  activity  studied.  of  (1951a)  of  such of  study  thesis  to  determine,  is with  is  among f i s h e s ,  in  flowing  rheotaxis  coho and the  sockeye  to  streams,  occur. and  three  sockeye  smolt  possibility  changes r a d i c a l l y  coho and  fac-  has  this  Thirdly,  of  these  of  testosterone  sudden temperature reaction  this  vary  negative  by  reactions  rheotaxis  thyroxine,  compounds on t h e  turbulent  made  is  played  of  purpose  s p e c i e s , how w i d e s p r e a d  Hoar  has  hope  been  several  stickleback  the  part  was  detailed  in  that  F i r s t l y , an attempt  A  however,  it  to  the  hor-  and  fish  threefold.  such as  brain  compara-  on the  then,  the  the  and t e m p e r a t u r e  summary,  in  a  of  as hormones  In  of  knowledge  the  latter  It  downstream  centres  media  salmon;  young f i s h  the  the  presence  on the  tors  currents  the  b)«  1951  such as temperature.  Pacific  understanding  to  internal  Tinbergen's with  due  system of  turn  (Hoar,  propose that  also  contributions  behaviour  furthering  in  external  analysis  tive  the  smolt.  modify-  6 M A T E R I A L S AND METHODS  Experiments British in  Columbia from  cement  Sciences gravel  hatchery  Mortality in  general,  commercial on a or  diet  meal  consisted fish  of  I  together  group  of  Responses to  The  time 8°  are  the  up  at  water  University Fish  of  the  hatchery the  was  head thus  salmon mixed such as  whiteworms  from  the  were  was of  run  held  each  through trough.  avoided. with  eels,  of  Biological  Food,  pablum  fed  (Enchytraeus).  with  common a n d the  listed,  with  be  and  more  readily  Daphnia  in  this  in  1  the  to  in  e a c h was  corresponding  studied listed  where  and  the  size  next  Table  II.  The  December  15,  1952,  hatchery  names  described below,  Water.  August  temperature  to  of  are  scientific  locality  Currents  fishes  mean l e n g t h s ,  the  set  the  the  1953.  basement  entering  experiments  General  lasted  the  at  April  Some f i s h ,  lists  utilized  period  in  out  (Tenebrio).  species  their  to  canned  earthworms,  used,  each  1952  in  of  meal.  Table  Under  carried  filters  chlorine  worms  species  Water  charcoal from  May  troughs  building.  and  were  troughs  of  the  caught. the  data.  s e r i e s , and experimental during  f e l l  which  from  18  to  and  19  cm.  C. Metal  deep were Figure  1  periments  troughs  employed shows two to  be  for of  242  cm.  long,  observations these  troughs  described later.  of set  26  cm. wide  fishes up f o r  An o v e r f l o w  in  linear  the pipe  currents.  hormone 2  cm.  in  ex-  Table  I.  used f o r  Common  Species  Oncorhynchus  kisutch  (Walbaum)  coho  (Walbaum)  spring  tshawytscha  0.  keta  ( W a l b aum)  chum  0,  nerka  (Walbaum)  sockeye  Cot t u s  gairdnerii asper  kamloops  Jordan  Ameiurus  nebulosus  (Le  Anguilla  bostoniensis  Sueur)  Le  salmon  salmon  kamloops  prickly  Richardson  Sueur  brown  rheotaxis.  name  salmon  0.  Salmo  studying  salmon  trout  sculpin  catfish  american  eel  Where  Brunette  Nile  it  and  Creek  obtained  Alouette  hatchery,  Rivers,  B.C.  it  Marblemount  hatchery,  Wash.  Smith  hatchery,  Cultus  Deer  Stave  B.C.  Falls  Lake,  B.C.  River,  Becaguimic  B.C.  River,  N.B,  Lake,  B.C.  Table I I  Names and f o r k l e n t h s of f i s h e s studie f o r general response t o c u r r e n t s .  Common name  Mean l e n g t h cm.  Standard d e v i a t i o n cm.  coho salmon  7.7  + O.67  s p r i n g salmon  6.2  _+ 0.5&  brown c a t f i s h  4.5  ±0.71  prickly sculpin  4.3  + 0.99  29.7  +10.26  6.2  +1.15  atlantic eel kamloops t r o u t  Figure 1.  Apparatus f o r o b s e r v i n g jumping o f young salmon. Troughs were a l s o used f o r s t u d y i n g g e n e r a l r e s ponses t o c u r r e n t s , and p r e f e r e n c e o f f i s h f o r flowing or quiet water. t r i f u g a l pump;  P , 1/4  horsepower  F, f r e e z i n g u n i t ;  B,  cen-  sloping  metal c a t c h - b a s i n r e t u r n i n g w a t e r f r o m e x p e r i mental t r o u g h s t o c o o l i n g r e s e r v o i r below freezing unit.  7 diameter,  at  water  pumped i n  was  tubing,  at  the  1/4  Electric Eastern  one  rate  centrifugal  idential  was  screened off All  held  flow  the  at  the  of  8" t o  horsepower  and  long.  end,  other 10  surfaces  water  in  contact  a greater  of  the  hour  the  movements not  with  pumps w e r e  volume,  the  fish  in  each of  to the  trough  minutes. and  the  turned  This  again  holding  light  these  two  periment.  A total  while  with  catfish  coho and were  noted  The  used f o r  surface  salmon,  eight  with  one  time  to  for  the  of  desired  the  the  The 30  fishes'  fish  number  the  centre  replications.  for one  and of  each  each ex-  s p e c i e s Was  s c u l p i n s and  the  returned  taken  after  each  after  were  of  seconds  then  were  Metre  one  d i v i s i o n of  were  in  species  After  repeated  temperatures  experiments  spring  the  every  fish  a Weston L i g h t  six  cm.  perforated  a p o s i t i o n where  p r o c e d u r e was  water  225  was  one  and o b s e r v a t i o n s  later.  the  of  regulated  sections.  Water  at  trough.  equal  recorded with  performed  the  three  t r o u g h was  of  fish  marked  hours  at  12  inflow  s e c t i o n s was  overflow  covered  troughs  lines  troughs.  intensity  were  pencil  recording  constant  fish  between two  in  begun from  into  a  possible.  place  removed,  A General  The  the  glass  smaller  troughs. to  while  cm.  maintain  these  trough  the  1.2  minute.  water  was  current  on,  R e d wax  of  any  no w a t e r  immediately  startled.  hour  of  partitions  area  15  of  experiments  third  two  with  p r o c e d u r e was t o  central  partitions  the  8" c m . ,  at  pump o r t w o  space a v a i l a b l e  By u s i n g f o u r  in  per  used to  in  aluminum p a i n t .  The  liters  pumps w e r e  of  level  end t h r o u g h  centrifugal  so the  number  water  eels,  8  In  all  experiments  screening  covered the In  the  inflow  for  each  for  data,  troughs  in  A modification  of  the  whether  the  of  fish  will  plywood  inflow  75  end o f  partition directed  into  movement  side  partition  of  In  the  any  of  o n one  the  pumped i n t o  of  fish  s e c o n d s was  in  determined  switched  to  made f o r  another  the  illumination  Goho were  partition. to  fish  seconds side  15-minute recorded  salmon,  used  of  inflowing  was  in  Twelve  for and  15  period. after  hour  each  preference  the  of  The  the volume per  was  started  placed  in  the  After  plywood inflow  of  minute.  trough.  the  later  Water  were  was  similar  temperatures  then  records and  experiment.  kamloops t r o u t ,  these  in  side  to  liters  thus  methylene  The  were  Inflowing  plywood,  water  fish  minutes.  one  central  water  of  roam f r e e l y on each  the  10  was  length.  negligible. at  quiet  cm. wide  form a  of  designed  or  A d d i t i o n of  inflow  other  were  only.  24  its  side  the  numbers o f 30  of  experiment  end and p e r m i t t e d  every  side  to  held  outlet  recorded  third  was  turbulent  and  was  side  the  the  into  trough  o n one  catfish  from escaping.  apparatus  long  either  showed, t h a t  hour  30  trough  down o n e  blue  one  fish  plastic  Water.  move  the  turbulence  water  salmon  mean p e r c e n t  above  cm.  creating  opposite  every  Quiet  c o u l d be  dye  the  or  longitudinal water  prevert the  Turbulent  A piece  placed  the  to  and young  species.  determine  water.  of  eels  trough  analysing the  third  Preference  to  involving  eels,  tests.  sculpins Six  and  experiments  9 were  carried  each  of  on each at and  the  the  out other  side end  of  of  P values  difference  with  the  two  varying  periods  whether  or  water.  The  not  means  and of this  methyl  alter  of  of  ability  and b y  some p o t e n c y  Houses,  but  Groups aerated fed  solution  twice  every  daily,  second day.  conditions  in  of in  three  based 20 22  except  litre  glass  o n week  Control  hatchery  (BDH)  tap  salmon  for  determine flowing  2,500,000  1  2,000,000  1  1,600,000  1  1,600,000  1  20,000,000  by  To  et  the  work w i t h in  battery  groups were  used  dictated  immersed  ends,  water.  the  1  (Hoar  were  supplied  were  t  of  immersed  testosterone  on p r e v i o u s  fish  again  used:  estrogens data  and  species.  r e a c t i o n s to  (Nylestin)(BDH)  with  hour  to  (BDH)  experiments  not  were  (BDH)  and  fish  significance  solutions  their  thyroxine  the  each  (BDH)  Concentrations  were  smolt  hormone  Oestradiol  concentrations  for  one  of  with  Treatment.  thyroxine-sodium  Stilboestrol  on p r e v i o u s  salmon  of  five  1946).  Hormone  testosterone  Ethinyl  end  show t h e  hormones were  Dienoestrol  based  in  would  following  the  (Snedecor,  sockeye time  at  to  by  and  mean p e r c e n t a g e  calculated  calculated  synthetic  The  was  Rheotaxis  Coho  The  partition  hours  between  of  salmon and t r o u t ,  species.  were  Modification  the  and  20  jars. the  kept  al,  1952).  by  avail-  British  Drug  fish. liters  of  They  were  solutions  under  control  were  changed  identical  temperatures  the  10 j a r s were s e t i n one o f t h e cement h a t c h e r y rounded by r u n n i n g January t o A p r i l , f r o m 6 t o 9°  water. 1953,  troughs  and s u r -  E x p e r i m e n t s were c a r r i e d  out from  and t e m p e r a t u r e s  + 0.54  cm.) and s o c k e y e  Measurements were mean f o r k  changes i n a c t i v i t y described  a c e n t r a l l y placed  hormones were coho s a l m o n salmon smolt  ( £ . 2 _+ 0.53  was s e l e c t e d a s a t e s t  f o l l o w i n g hormone t r e a t m e n t .  v e r t i c a l dam d i v i d e d them i n t o Water was r e c i r c u l a t e d  (using f r e o n gas) maintained  i n the hatchery. was r e t u r n e d height the  From t h e o u t l e t  tests  equal-sized  by a l / 4 h o r s e -  the temperature  freezing equal  ends o f t h e t r o u g h s  t o the cooling r e s e r v o i r (figures 1  of the overflow  pipe.  a 2 cm. dam, and s o c k e y e , b e i n g cm. t o r e a c h  t h e upper p o o l .  was h e l d a t 14  prevented  fish  cleaned  liters  escaping  r a t u s were c o v e r e d  to that  water  and 2 ) .  The  t o remove  with  over  Coho were made t o jump smaller f i s h ,  p e r minute  i n separate  and p l a s t i c  the sides.  1.5 each  screening  A l l p a r t s o f t h e appa-  aluminum p a i n t and p e r i o d i c a l l y  thoroughly  slime. f r o m two b a t t e r y j a r s were  c o n t a i n e r s i n q u i e t w a t e r f o r one h o u r .  Water c i r c u l a t i o n was s t a r t e d i n t h e t r o u g h s , adjusted  over  h a d t o jump  The w a t e r volume e n t e r i n g  I n any e x p e r i m e n t f i s h placed  metal  o f t h e dam above t h e l o w e r p o o l was r e g u l a t e d b y c h a n g i n g  height  trough  f o r studying  I n these  power G.E. pump f r o m a r e s e r v o i r , where a P a r m e t i c unit  cm.)  The l o n g  p r e v i o u s l y were a g a i n u t i l i z e d .  u p p e r and l o w e r p o o l s .  smolt  lengths.  Jumping b e h a v i o u r  troughs  varied  C.  Fish treated with (£.9  i n the hatchery  so t h e dams were t h e a p p r o p r i a t e  water l e v e l s  height,  were  and one g r o u p  Figure  2.  Apparatus  used t o  pump a c o n s t a n t  water of r e q u i r e d temperature mental troughs. trifugal F,  pump;  twin c o i l  P,  1/4  through  horsepower  I, intake  Parmetic  volume  pipe;  freezing  experi-  G.E.  N, unit.  of  cen-  nozzles;  11 of  fish  were the  begun time  upper  f  was  put at  in  the  once  from  battery  and  speed were  current  experiment. a  Fish  treatment  four were  observe  weeks then  their  treatment. solution,  divided 50  for  each  measured  the  and  three of  of  the  and  to  the  fish  jump  returned  to to  light  trout  of  and  the the  intensity each  immediately  (8.9  A t-test  or  was  fish  The  the  one  in  second week.  later  to hormone  ethyl  urethane  formalin. arbitrarily  mean t i m e s  used to  a  following  was  the  the  discontinued.  described  over  of  times  percent  10  and  jump  (in  minutes)  dam w e r e  calculated  determine  the  signifi-  mean v a l u e s  for  experi-  calculations  cover  only  were  currents  in  stages to  six  anesthetized  between  fish.  for  pooled results series  was  thyroxine from  completed  two with  and series the  estrogens.  Temperature  + 0.54  five  metal tubs  were  fish  while  beginning  experimentation  weekly  treated  the  experiments  preserved  Changes  Chum s a l m o n f r y smolt  of  c o n c l u s i o n of  of  circular  fish  the  control  different  Effects  then  the  repeated  in  difference  experiments,  three  in  period  stage.  testosterone of  at  a group  treatment  behaviour  percent  of  of  Then the  into  for  mental  fish)  (10  commenced at  and were  placed  The  cance  sight  Observations  dam.  of  After  of  temperatures,  recorded  Experiments week  each t r o u g h .  were  Water  shows  3  out  Fish  jar.  Figure  of  percent  50  recorded.  appropriate  pool  a point  necessary for  p o o l was  below  lower  cm.)  (4*9  were  on  Rheotaxis.  + 0.43  used  in  cm.) this  and  coho  series.  salmon These  Figure 3 »  Kamloops  t r o u t swimming  below v e r t i c a l current.  D,  dam. dam.  i n turbulent  Most  fish  water  are f a c i n g  12 s p e c i e s were chosen because they show s t r o n g p o s i t i v e r h e o t a x i s and  changes o c c u r r i n g i n the response to d i r e c t i o n  of flow were e a s i l y detected  i n the apparatus d e s c r i b e d below.  Experiments with chum salmon were c a r r i e d out  during the  of 1952  1953.  and those w i t h coho i n the The  tubs 68 cm. and  27  cm.  s p r i n g of  apparatus c o n s i s t e d of two  galvanized  i n diameter a c r o s s the t o p , 212 deep.  cm.  in  (figure 4 ) .  i r o n wash circumference  These were p l a c e d s i d e by s i d e to  comparative o b s e r v a t i o n s  facilitate  A v e r t i c a l pipe 1  i n diameter attached t o the i n s i d e of each tub was  cm.  perforated  along i t s l e n g t h so t h a t water e n t e r i n g at the top was  forced  out the s e r i e s of h o l e s , i n a d i r e c t i o n p a r a l l e l t o the of t h e tub and current. at  19  cm.  produced a comparatively  A c e n t r a l overflow  uniform  pipe maintained  the water l e v e l  and d r a i n e d water back i n t o a r e s e r v o i r while  pipe.  an  perforated  Tubs and r e s e r v o i r s were set i n deep cement troughs  where water, surrounded the r e s e r v o i r s t o m a i n t a i n temperatures. was  side  circular  E a s t e r n c e n t r i f u g a l pump f o r c e d i t up a g a i n i n t o the inlet  summer  The  appropriate  s u r f a c e speed of the c u r r e n t i n each tub  h e l d at 25 - 30 cm.  Aluminum p a i n t covered  per second, measured at the  periphery.  the i n n e r s u r f a c e s of both tubs and  reservoirs. The h o l d two  procedure f o l l o w e d i n any  groups of one  experiment was  to  s p e c i e s s e p a r a t e l y f o r an hour i n q u i e t  water at the temperature of the hatchery  water.  Currents as  d e s c r i b e d above were s t a r t e d i n the t u b s , the temperature i n  Figure 4 .  Rheotaxis tubs with kamloops t r o u t o r i e n t i n g i n c i r c u l a r currents.  R, r e s e r v o i r surrounded  by water t o c o n t r o l temperature; c e n t r i f u g a l pump.  P , Eastern  13  one tub being equal to the holding temperature, and that i n the other 4 or 5° C, above or below.  A group of f i s h was  placed i n each tub and observations begun immediately from behind a screen.  Chum salmon were observed i n groups of 12  and coho i n groups of 10. No attempt was made to obtain a quantitative measure of the a c t i v i t y of the f i s h i n t h i s apparatus, but over a 10 to 15-minute period careful  ob-  servations were made of the rheotactic response of each group.  Fish were described as showing negative  rheotaxis  when they swam faster than the surface flow, and i n the same direction.  I f the f i s h faced the current, swimming into i t  or holding p o s i t i o n i n the flow, they were said to be showing positive rheotaxis. the current.  Occasionally an i n d i v i d u a l d r i f t e d with  This i s not referred to as negative  rheotaxis.  Fish behaving i n t h i s way were classed with those showing positive rheotaxis. was  recorded  Light intensity at the water surface  after every experiment.  Thirty-six  separate  experiments were carried out with chum salmon and 12 with coho.  14  RESULTS General Responses t o Figure  Currents.  5 shows the p r o p o r t i o n of f i v e  the area of g r e a t e s t t u r b u l e n c e minutes a f t e r the flow was represents  started.  Each p o i n t on any  of the t r o u g h over a number o f experiments. together  15  of the l o n g troughs f o r  the mean percentage of f i s h i n the  have been presented  species i n  curve  inflow t h i r d These f i v e  to emphasize the f a c t  curves  that,  although t h e r e are v a r i a t i o n s among s p e c i e s , a l l of these move c l o s e to the i n f l o w and  s t a y there at l e a s t  fish  50 percent  of  the t i m e . On removal of the p a r t i t i o n s h o l d i n g the f i s h the centre of the  trough,  the immediate response was  a g e n e r a l movement by a l l f i s h toward the l e n g t h of time f o r movement toward the p o s i t i o n v a r i e d among the  species  outflow  at  usually  end.  The  i n l e t tube from t h i s  (figure 5).  Both e e l s  and  c a t f i s h showed a r a p i d i n i t i a l response, moving i n t o the most t u r b u l e n t area w i t h i n one o f the t r o u g h . i n f l o w end  minute o f r e l e a s e f r o m the  In c o n t r a s t the  centre  s p r i n g salmon moved i n t o the  i n an average of f o u r minutes and t h e coho i n  seven minutes. Throughout these experiments the showed the g r e a t e s t the t u r b u l e n t  activity.  zone and  more o f t e n t h a n any  s p r i n g salmon f r y  They svram most c o n s i s t e n t l y i n t o  jumped out of the water i n t h i s  other  s p e c i e s except the e e l s .  s p r i n g f r y moved away from the  area  When the  i n f l o w , they swam q u i c k l y i n  Figure  $.  Mean p e r c e n t inflow tervals See  of  five  species  end  of  the  of  30  seconds over  text.  long  metal  of  fish  in  the  troughs  at  in-  a 15-minute  period.  O  EEL I I IO 20 TIME - 1/2 MINUTE INTERVALS  30  15 close  aggregates to the  o u t l e t end  Coho f r y , o n t h e  other  response to the  inflowing  from inflow to looser  of t h e  trough  and  back  hand, showed a l e s s c o n s i s t e n t water.  aggregations.  Jumping n e a r t h e  o f t e n w i t h coho t h a n w i t h s p r i n g of t e r r i t o r y  ( H o a r , 1951  occasionally  seen, but  a;  spring  forth  f r y , and  inflow occurred  salmon.  Nipping  S t r i n g e r , 195 )  by  2  neither  positive  They moved b a c k and  o u t l e t more o f t e n t h a n t h e  r e a c t i o n was  again.  less  and  the  in  defence  coho were  shown by  the  spring f r y . In the  two  three  general,  species  species  o f coho.  fish  to hold the  coho moved about  near the i n the  s i d e s by  inflow.  troughs.  species  i n f l o w o v e r a two minutes.  for  Figure  coho and the  inflow  Preference  6  three  the  The  over the  end  trough.  e e l s were the  species  for  Flowing  or Quiet  The  r e s u l t s of the  given  former minutes  the  there most  were  often  difficult  and  escaped  plastic  current  hours. i n the  while  other  the  over  screening.  same r e s p o n s e t o  response to  are  15  these  that  the  first  as t h e y d i d d u r i n g  s a l m o n f r y o v e r two  of  than  that  On  active f i s h  showed much the  like  most o f t h e t i m e ,  working under the  shows t h e  percent  fact  i n a g g r e g a t e s and  hour p e r i o d  spring  other  by  the  They a r e  j u m p i n g and  All  by  at t h e  The  i s more c o n s i s t e n t  were s c a t t e r e d t h r o u g h o u t  hand, the no  end  above.  i n s m a l l g r o u p s , and  were some f i s h  others  inflow  i s p a r t l y explained  moved s i n g l y o r there  s c u l p i n s and e e l s behave  o f salmon d i s c u s s e d  i n the  This  catfish,  the  first  15  demonstrated  Similar  data  appendix.  W a t e r.  experiments using  the  long  troughs  Figure  6.  Mean  percent  inflow  of  two  species  of  salmon  end  of  the  long  metal  were t a k e n  at  the  time  intervals  circles,  spring  salmon f r y ; periods  salmon f r y ;  vertical  during  which  broken no  troughs;  open  in  the  records  shown.  Solid  circles,  lines,  observations  one  coho  hour  were  made.  IOO o  ••••••  o  o  — O  •••• o  o o  •• •••• •  o  •• o  o  o ° O  o o  o o  • • o  O  ••  • • • °  o  ° oo o  •  o  oo  •  •  ° o  •  o  •  •o  -  •  •  ° o  o  •  oo  o  o o o o o o ooo  •  o  o o°°°  0  O  o  O  oo  o  •  •  •  •  o  50  ••  oo °  0  o o  o o o  •  •  o oo o  •  ••••  o o  o  75  •  o o  -  1 1 o  OQOO  1  1  1 30 TIME -  150 1/2  MINUTE  INTERVALS  270  16 w i t h l o n g t i t u d i n a l p a r t i t i o n s at the i n f l o w end are g i v e n i n T a b l e I I I . F i g u r e s shown are f o r average percentages  of f i s h  i n the t u r b u l e n t and the q u i e t areas over a s e r i e s of e x p e r i ments.  With one  e x c e p t i o n , the  s c u l p i n , these f i g u r e s  in-  d i c a t e t h a t a g r e a t e r p r o p o r t i o n of each s p e c i e s w i l l move i n t o a s t r o n g f l o w of water than i n t o a q u i e t a r e a .  Coho  salmon are most marked i n t h e i r p r e f e r e n c e f o r t u r b u l e n c e . The  experiments were c a r r i e d out i n the l a t e f a l l when s p r i n g  salmon were no l o n g e r a v a i l a b l e , and t h e r e was of  comparing coho w i t h s p r i n g f r y .  no  possibility  Kamloops t r o u t f r y were  used i n s t e a d f o r comparison w i t h coho. Various o b s e r v a t i o n s were made on the behaviour the f i s h d u r i n g these experiments. u s u a l l y remained i n aggregations, r i t o r i a l behaviour results.  was  seen.  The  kamloops t r o u t f r y  but some evidence  of t e r -  T h i s sometimes l e d t o c o n f u s i n g  T e r r i t o r i a l behaviour  and  occasional nipping i n  the t u r b u l e n t water by s e v e r a l t r o u t d u r i n g the f i r s t some experiments l e d t o i n c o n s i s t e n t r e s u l t s and h i g h P v a l u e compared to t h a t f o r t h e second period.  t r o u g h and  hour o f  a relatively  observation  As b e f o r e , the coho f r y moved about i n l o o s e  gregations.  of  They moved a c t i v e l y up and  ag-  down the l e n g t h of the  entered the i n f l o w s i d e of the p a r t i t i o n more con-  s i s t e n t l y t h a n the  other s p e c i e s .  The  young c a t f i s h a l s o moved  i n t o t u r b u l e n t r a t h e r than q u i e t water, but more f r e q u e n t l y stayed i n groups near the o u t l e t s c r e e n . difficult  to keep i n the t r o u g h .  The  e e l s were  Some e e l s t r i e d v i g o r o u s l y  Table I I I .  Mean percent o f f i s h on each s i d e of p a r t i t i o n . Flow changed t o o p p o s i t e s i d e o f trough a f t e r one hour.  Percent f i s h b e f o r e Species  No. of experiments  turbulent water  quiet water  change  Percent turbulent water  t  f i s h a f t e r change quiet water  t  P  6.934 <0.01  39.5  9.2  1.242  O.25  28.8  11.0  2.438  0.04  12.2  1.206  0.27  24.1  4.8  3.O63  0.016  24.4  11.6  1.123  0.30  21.1  14.1  0.986  O.36  27.9  16.7  1.349  0.22  10.3  11.3  0.400  0.5  coho  6  37.8  5.0  trout  6  27.3  12.4  catfish  5  20.4  eel  5  sculpin  5  5.499 < 0 . 0 1  17 t o work t h e i r way o u t u n d e r  the screening,  i n t h e most t u r b u l e n t w a t e r . increased the  activity  on the i n f l o w  proportion of eels  tended  t o stay  f i r s t , hour  This  on t h i s  side  o f t h e p a r t i t i o n and  near t h e c o r n e r s o f t h e t r o u g h .  area.  higher i n  By t h e s e c o n d  S c u l p i n s and c a t f i s h  i n the turbulent  Sculpins  During the  t h e p r o p o r t i o n o f s c u l p i n s was s l i g h t l y  p r e f e r e n c e was s e e n .  when  "escape" behaviour l e d t o  s i d e was d e c r e a s e d .  the t u r b u l e n t t h a n i n the quiet  the water  especially  h o u r no  d i d n o t jump o u t o f  area.  Hormones and R h e o t a x i s The rate  a t which  in figure  7.  different  fish  two  o f t e s t o s t e r o n e and t h y r o x i n e o n t h e  coho s m o l t  jump o v e r a 2 cm. dam a r e summarized  The f o u r week t r e a t m e n t s were d u p l i c a t e d and the g r a p h s  sets of data.  fish for  effects  are the r e s u l t s  The d i f f e r e n c e  and c o n t r o l s v a r i e s .  The s i g n i f i c a n c e  each week h a s b e e n d e t e r m i n e d  values  i n jumping  significant  t i m e between of t h i s  i s this  of experimental f i s h  controls  i s consistent,  and  t  and  P  statis-  However, t h e  t o move o v e r t h e dam f a s t e r  except  treated  difference  difference  at t h e 0.G1 l e v e l f o r coho.  tendency  the  I n o n l y one c a s e , t h e  3rd week o f t e s t o s t e r o n e t r e a t m e n t , tically  o f lumping  statistically  are presented i n Table IV.  with  than  f o r t h e f i n a l week o f t r e a t m e n t  w i t h t h y r o x i n e , where t h e t r e a t e d  fish  seemed i n p o o r  con-  dition. F i g u r e 8 g r a p h i c a l l y p r e s e n t s d a t a f o r an i d e n t i c a l s e r i e s u s i n g sockeye  smolt.  Here a g a i n t h e o v e r a l l r e s u l t i s  Figure  7.  Histograms on the  showing  rate  upstream  at  over  experiments.  the  which a  2  cm.  effects  coho dam.  of  salmon  two smolt  Open b a r s ,  hormones jump control  TESTOSTERONE  THYROXINE  25  • •.  •  "I  15  1 I  21 •«  I  • %  • ••  ••• • •  3  DURATION  4 OF  A  m  • •  2  TREATMENT  3 - WEEKS  4  Table  IV  Time t a k e n during  for  50 p e r c e n t  thyroxine  of  coho  smolt  and t e s t o s t e r o n e  No. o f experiments  jump f r o m l o w e r  to  upper  pool  treatment.  Control  Thyroxine  Week o f treatment  to  Mean t i m e minutes  No. o f experiments  Mean t i m e minutes  second  4  21.9  4  23.3  0.179  third  8  22.4  8  25.6  O.94I  O.36  fourth  8  26.4  8  18.7  2.406  0.03  0.02  Control  Testosterone  Week o f treatment  No. of experiments  Mean t i m e minutes  >0.5  No. of experiments  Mean t i m e minutes  second  4  17.3  4  24.8  3.000  third  9  17.5  9  26.9  3.357  fourth  9  14.9  9  18.1  1.067  <  0.01 0.3  Figure 8 .  Histograms showing the e f f e c t s of two hormones on the r a t e at which sockeye salmon smolt jump upstream over a 1 . 5 cm. dam. t r o l experiments.  Open bars, con-  TESTOSTERONE  I  DURATION OF TREATMENT  THYROXINE  I*. »•• •»• • •  ••  ... *  -  WEEKS  18  f o r treated f i s h t o move upstream f a s t e r than c o n t r o l s . A notable exception occurs w i t h testosterone t r e a t e d f i s h i n the second week of treatment.  The  t  and  P  c a l c u l a t e d for sockeye and presented i n Table  values are V.  The r e s u l t s of i d e n t i c a l experiments with sockeye smolt using three estrogen compounds are shown i n f i g u r e 9» A l l three hormones stimulated the a c t i v i t y of the f i s h , but the change was most pronounced w i t h one group.  Those immersed  i n S t i l b o e s t r o l were the most a c t i v e f i s h seen i n t h i s apparatus.  This increase i n a c t i v i t y was also n o t i c e a b l e i n the  b a t t e r y j a r s , -and when the f i s h were c a r r i e d i n p a i l s . N y l e s t i n , on the other hand, seemed to have a d e t r i m e n t a l effect.  F i s h immersed i n s o l u t i o n s of t h i s compound appeared  to be under s t r e s s and t h e i r movements i n the troughs were e r r a t i c ; while i n the b a t t e r y j a r s they were l e s s a c t i v e than c o n t r o l s .  It. i s i n t e r s t i n g to note, however, that the  mean time f o r h a l f of t h i s group to cross the dam i s s t i l l l e s s than f o r c o n t r o l s .  Table VI presents the  t  and  P  values  f o r s i g n i f i c a n c e of the d i f f e r e n c e between mean values. Figures 7, 8 and 9 show that w i t h few exceptions, both c o n t r o l ' and experimental sockeye and coho move upstream f a s t e r i n the -later stages of treatment than at f i r s t . was  This  e s p e c i a l l y n o t i c e a b l e a f t e r the f i r s t two or three ex-  periments with each group.  The p o s s i b i l i t y of a l e a r n i n g  process being i n v o l v e d i n t h i s increase i n jumping r a t e w i l l be discussed l a t e r . During the many hours of observations necessary  Table V  Time taken f o r 50 percent o f sockeye smolt t o jump from lower t o upper p o o l during t h y r o x i n e and t e s t o s t e r o n e treatments.  Thyroxine Week o f treatment  Control  No. of experiments  Mean time min.  No. o f experiments  Mean time min.  second  5  18.7  5  21.9  0.561  >0.5  third  8  10.9  8  14.2  1.100  0.3  fourth  8  8  11.1  0.857  0.4  Week of treatment  9.9  Testosterone  Control  No. of experiments  Mean time min.  second  6  21.8  6  13.8  1.951  0.08  third  9  10.8  9  12.1  0.929  0.37  fourth  7  7.9  7  10.5  1.857  0.09  No. o f experiments  Mean time min.  Figure  9.  Histograms estrogens salmon dam.  showing the on the  smolt  jump  Open b a r s ,  rate  effects at  which  upstream control  over  of  three  sockeye a 1.5  experiments.  cm.  DURATION OF TREATMENT - WEEKS  Table  VI.  Time  taken  during time  for  three  between  50  percent  of  sockeye smolt  estrogen treatments, each t r e a t e d  Control  group  t  and  and t h e  Stilboestrol  to  jump  P values same  from lower show t h e  to  upper  difference  pool in  control.  Dienoestrol  Nylestin  Week o f treatment No. of experiments  3  second  Mean time min.  15.8  No. o f experiments  4  10.3  t  2.037  P  0.1 6  third  8.2  Mean time min.  6  No. of experiments  4  Mean time min.  19.9  No. of experiments  Mean time min.  3  20.3  0.569  0.803  >0.5 7.5  6  0.46 11.9  6  11.4  t  0.854  3.08*3  1.975  P  0.4  0.01  0.08  5  fourth  13.0  5  t P  <  6.1  5  10.0  5  9.2  3.833  1.667  2.000  0.01  0.12  0.08  19 to  compile the d a t a presented here  of  s o c k e y e and c o h o w e r e e v i d e n t .  some c o n t r a s t s i n b e h a v i o u r A l t h o u g h b o t h s p e c i e s moved  about t h e t r o u g h s i n a g g r e g a t e s , t h e young sockeye more c o m p a c t g r o u p s t h a n t h e c o h o . species during the f i r s t  characteristic  f i s h t o swim b a c k a n d f o r t h  let  s c r e e n t o t h e f a c e o f t h e dam.  i n c l o s e groups from the outT h i s movement was  r a p i d and r e g u l a r l y t i m e d , t h e f i s h only.  f o r a few seconds  the  t i m e spent s t r u g g l i n g i n the t u r b u l e n t water below  f a l l s gradually increased. t h e n emphasized  ly,  some f i s h  H o w e v e r , w i t h i n a few  The  at  s t a y i n g below  dam  was  of both  f e w m i n u t e s o f any e x p e r i m e n t was f o r  all  first  One  stayed i n  the  minutes  c l o s e r g r o u p i n g by  the  sockeye  a s t h e c o h o a g g r e g a t e s b r o k e up more r e a d i -  staying  i m m e d i a t e l y b e l o w t h e dam  and o t h e r s  swimming t o the; o u t l e t . In ing  t h e a r e a a b o v e t h e f a l l s t h i s more c o m p a c t  among s o c k e y e was  again evident.  W h e r e a s some o f t h e  coho i n t h e upper p o o l o f t e n r e s t e d near the bottom of  t h e dam,  i n front  the sockeye s t a y e d m o s t l y i n the a r e a of g r e a t e s t  t u r b u l e n c e , and w h e n swimming t o t h e dam as a  group-  and b a c k a g a i n moved  group. A n o t h e r f e a t u r e of t h e b e h a v i o u r o f t h e s e y o u n g  s a l m o n i s t h e marked t e n d e n c y o f s e v e r a l f i s h t o jump o v e r the  dam-together.  I t was  repeatedly noticed that  m i n u t e s w o u l d p a s s w i t h no f i s h f i s h would  jumping, then f i v e or s i x  move o v e r t h e b a r r i e r w i t h i n s e v e r a l  T h i s h a p p e n e d more o f t e n w i t h Two  several  sockeye t h a n  seconds.  coho.  f u r t h e r p e c u l i a r i t i e s o f qpho b e h a v i o u r i n  t h i s a p p a r a t u s a r e w o r t h y o f comment.  One  i s t h e movement o f  20 f i s h back over the v e r t i c a l face of the dam from the upper to the lower pool.  This a c t i v i t y was  seen i n 26 d i f f e r e n t coho  experiments of which 15 were with treated f i s h and 11 with controls.  The other a c t i v i t y peculiar to coho was chafing, which  has been described previously f o r a species of c'yprinid (Keenleyside, 1952) i n t h i s study.  and was  seen i n 10 separate experiments  Chafing occured both above and below the  dam,  among control and t e s t coho, and by f i s h that were either facing or moving with the current.  Neither downstream move-  ment over the dam nor chafing was seen among sockeye. The prolonged, 4-week treatment with hormones produced evidence of stress.  The f i s h often showed e r r a t i c  movements i n the l a t e r stages of treatment.  For example,  coho smolt during the fourth week of treatment with thyroxine, were very slow to move over the b a r r i e r .  Their jumping below  the f a l l s was weak and e r r a t i c and the same f i s h often had to jump s i x or eight times to cross the dam.  Controls usually  reached the upper pool on the f i r s t t r y .  Furthermore, at  t h i s stage many coho stayed at the outlet end of the trough and did not attempt to jump.  In contrast, some of the treated  sockeye showed increased, but more e r r a t i c , general a c t i v i t y , swimming speed and jumping.  The f i s h jumped vigorously, but  i n various directions below the dam and the r e s u l t was  slower  movement to the upper pool than the degree of a c t i v i t y warranted. Such e r r a t i c behaviour was not consistent with any one group, but appeared occasionally among a l l treated sockeye.  21  When t h e s e ..experiments was  were t e r m i n a t e d e a c h g r o u p  p l a c e d i n t h e / r o t a t i n g c u r r e n t i n one  tubs d e s c r i b e d e a r l i e r . c l o s e group  and  held  The  position  from thyroxine solutions darting fast  about.  and  The  against coho.  group  the  No  circular  c u r r e n t s the Positive  both t r e a t e d  and  sockeye  control  g r o u p i n g b e h a v i o u r was  Those t r e a t e d w i t h They a g g r e g a t e d  sockeye  occasionally  degree  active  negative rheotaxis i n these tubs.  carry  of p o s i t i v e  out t e s t s  of treatment  Temperature  rheotaxis.  i n this  o f sockeye  and  and  coho  more but  expected. sockeye.  showed a  not  show possible  stages  salmon.  Rheotaxis  show c o n s i s t e n t  both  chum f r y and  i s positive  results  f o r 36  carried  out f r o m May  coho  negative r h e o t a x i s i n the c i r c u l a r  In water c o l d e r than the h o l d i n g temperature activity  among  about  S o c k e y e d i d not I t was  tub  observed  apparatus during e a r l i e r  At e l e v a t e d t e m p e r a t u r e s smolt  the  darted  o t h e r s and  higher  to  flow.  exhibited  marked t h a n  t h a n the  in  c o h o , however,  S t i l b o e s t r o l were t h e most a c t i v e  more c l o s e l y  much  r h e o t a x i s dominated,  less  coho  d i s t r i b u t i o n both  n e g a t i v e r h e o t a x i s was  behaviour.  the  Those  r h e o t a x i s i n the f a s t e s t  inconsistent  and  flow.  moved as a l o o s e a g g r e g a t i o n around  current.  In these  stayed i n a  movements and  Testosterone treated  vigorous positive  entire  smolt  i n the f a s t e s t  showed e r r a t i c  fish  of t h e r h e o t a x i s  coho  This l e d to a scattered  slow water.  displayed  control  of  rheotaxis.  experiments  Figure 10  dominant  summarizes  w i t h chum s a l m o n .  t o J u l y , 1952  the  tubs.  the  T h e s e were  when t e m p e r a t u r e s  i n the  Figure  10.  Histograms to  circular  Values  showing r e s p o n s e currents  shown a r e  at  range.  rheotaxis;  open b a r s ,  solid bar  circles,  that  were  different  percent  temperature  of. chum s a l m o n  temperatures.  experiments  at  Cross-hatched bars, negative  proportion controls.  of See  fry  each positive  rheotaxis;  experiments text.  in  each  22 hatchery  i n c r e a s e d f r o m 1 0 t o 16°  C.  Most o f t h e chum f r y  showed n e g a t i v e r h e o t a x i s d u r i n g J u l y when c o n t r o l were h i g h . circles.  The The  four  central  bars i n figure  controls with  6-9°  The  and  show most c l e a r l y  e l e v a t i o n and The  and  included  18 - 21°  lowering of  results  Because the p e r i o d  o f 12  identical  spring,  a t 9°  mental  thus emphasizing  the  I t was  no  currents  experiments  i n February  a r e shown i n f i g u r e  11.  C.  the c o n t r o l  about  temperatures  F i g u r e 11 c o v e r s o n l y the the response  at  experi-  extreme  Some c o n t r o l c o h o showed n e g a t i v e r h e o t a x i s found that  observation period  both tubs immediately less  include  were  temperature.  were c o n s i s t e n t  also.  bars which  bar that  o f e x p e r i m e n t a t i o n w i t h coho c o v e r e d  f i v e weeks d u r i n g e a r l y  results,  i n that  solid  marks  the different.response t o  March, 1953, w i t h coho smolt  temperatures.  10 c o n t a i n  p r o p o r t i o n of the bar below the c i r c l e  the p r o p o r t i o n of experiments controls.  temperatures  startling  by w a v i n g  the  fish  a white handkerchief  enhanced the p o s i t i v e  of the dominant r e s p o n s e  suddenly  d u r i n g the  after over  reaction regard-  experiment.  Figure  11.  Histograms smolt  to  showing  circular  peratures.  Values  ments  at  bars,  negative  response currents  at  shown a r e  each temperature  rheotaxis.  of  rheotaxis;  coho  salmon  different percent  range.  tem-  experi-  Cross-hatched  open b a r s ,  positive  23  DISCUSSION  animals times  widespread occurrence  has  been mentioned  i n the  1952). and,  The  literature  Among f i s h e s ,  i n some c a s e s ,  industry,  and  reational  resource.  the  spawning  centrated Since to  this fact  the  migration area  importance t o the as  some c o m m e r c i a l l y  small  fishing and  valuable  ability  creasingly  is desirable.  desirable to direct  Further, the  and  importance  knowledge  Sensory B a s i s of  stream i s  involved.  great  losses to ability  of  the fish  important.  to understand  must be f a m i l i a r  an  i n n a t e r e a c t i o n such  with the  T h e r e a r e d e s c r i p t i o n s i n the  periments designed involved  their  Rheotaxis.  In attempting as r h e o t a x i s one  of  i t i s becoming i n -  h e r e a g a i n knowledge o f t h e  orient in a fast  salmon,  downstream movements o f  y o u n g s a l m o n a r o u n d power dams w i t h o u t population,  con-  profitable.  movements i n r e l a t i o n t o t h e w a t e r masses a l o n g  migration routes  are  o f f i s h e s , s u c h as  spawning m i g r a t i o n upstream, a d e t a i l e d  rec-  species  o n l y t i m e when t h e f i s h  o r i e n t themselves i n c u r r e n t s i s of fundamental  their  recognized  a food  enough t o make f i s h i n g  i t i s b e l i e v e d t h a t the  in their  to  Buddenbrock,  phenomenon i s u n i v e r s a l l y  i s the  aquatic  i s e m p h a s i z e d many-  c o n s e r v a t i o n of f i s h With  among  Gunn, 1940;  ( F r a e n k e l and  i s of d i r e c t  i n the  i n an  and  of rheotaxis  t o d e t e r m i n e what  i n rheotaxis.  penetrating of these  A brief  will  not  be  literature  mechanisms of  ex-  sense o r g a n s a r e p r i m a r i l y  review out  sensory  of  some o f t h e  of place  here.  more  24 f  Lyon of  water  (1904) p l a c e d s e v e r a l f i s h i n a n e n c l o s e d b o t t l e  and suspended  i ti n a river.  with the current, the f i s h when p u l l e d end. of  crowded  orientation.  t o t h e upstream end,  T h i s e x p e r i m e n t was c a r r i e d  of the o p t i c a l  r i u m w i t h a movable  the  He l a t e r  fish  blinded  background  showed  a l o n g each  important  role  reaction,  Lyon  of tactile  Lyon  a l s o emphasized t h e waters  organs i n r h e o t a x i s  been  Dykgraaf  (1933) showed  t h e sense o f touch t o m a i n t a i n p o s i t i o n i n  When t h e f i s h  fish  i n an aquarium w i t h a  moving  t o u c h e d t h e b o t t o m t h e y moved a l o n g w i t h  t h u s swimming t h r o u g h t h e s t i l l stimulation  to detect  has also  (1904) f o u n d t h a t b l i n d e d f i s h o r i e n t e d i n  fishes utilize  that t a c t i l e fish  as b e f o r e .  importance i n h o l d i n g  O t h e r w o r k e r s have  stream by p l a c i n g b l i n d e d  it,  The f i s h  but w i t h o n l y one e y e  occurred  c u r r e n t s when t h e y t o u c h e d t h e b o t t o m .  floor.  side.  i n a n aqua-  1904; Clausen, 1931).  stressed.  a  fish  of t h e eyes i n o r i e n t a t i o n t o f l o w i n g  The r o l e  that  con-  (1909) t h a t b l i n d i n g b o t h e y e s o f  t h e e y e s were o f p r i m e  i n a stream.  of v i s u a l  a l t h o u g h no c u r r e n t was  swimming w i t h t h e b a c k g r o u n d  position  a n d i t was  Lyon f u r t h e r demonstrated the  field  destroyed the l a t t e r  concluded that  (Garrey,  t o the f i s h ,  s t i m u l u s by p l a c i n g  swam a l o n g b e s i d e t h e moving present.  out i n shallow  t h e o b s e r v e d r e a c t i o n was due t o l o s s  t a c t w i t h o b j e c t s on t h e bottom. importance  and  s t a t i o n a r y , t h e r e was a l a c k  w a t e r where t h e b o t t o m was v i s i b l e that  drifted  u p s t r e a m t h e f i s h / q u i c k l y moved t o t h e downstream  When t h e a p p a r a t u s was h e l d  clear  When t h e b o t t l e  pressure  i s o f prime changes  w a t e r . O t h e r s have  argued  importance.in enabling the  i n currents of water.  Buddenbrock (1952) reviews t h i s  literature.  The f u n c t i o n o f the l a t e r a l l i n e emphasized. detect  Dykgraaf  i n rheotaxis  has been  (1933) showed that b l i n d e d f i s h  could  f i n e j e t s o f water d i r e c t e d against t h e i r s i d e s through  a p i p e t t e , and t h a t t h i s d e t e c t i o n ceased when the l a t e r a l l i n e nerves were c u t . the cutaneous  He s t r e s s e d t h e f a c t , however, t h a t  sense organs w i l l d e t e c t  sudden d i f f e r e n c e s i n  water p r e s s u r e i n l a r g e r masses of water such as the f i s h meets i n i t s n a t u r a l h a b i t a t and thus overshadow s t i m u l a t i o n o f the lateral line.  Dykgraaf  concluded t h a t s i g h t and touch are the  primary senses o f o r i e n t a t i o n f o r f i s h e s i n c u r r e n t s , while the l a t e r a l l i n e may be important  i n some s i t u a t i o n s .  The part p l a y e d by t h e ear i n r h e o t a x i s c l e a r l y understood.  Gray  i s not yet  (1937) found b l i n d e d f i s h  could  o r i e n t i n r o t a t i n g but not l i n e a r c u r r e n t s and a t t r i b u t e d t h i s "pseudo-rheotropism" semicircular canals.  t o asymmetrical  I n a review of the sensory c a p a b i l i t i e s  of the l a b y r i n t h Lowenstein are  s t i m u l a t i o n of t h e  (1950) concluded t h a t the c a n a l s  s e n s i t i v e t o angular a c c e l e r a t i o n s while the o t o l i t h s are  capable o f r e s p o n d i n g t o any movement i n v o l v i n g a change i n momentum.  Not a l l workers are agreed, however, t h a t the semi-  c i r c u l a r c a n a l s cannot a l s o d e t e c t l i n e a r movements (Lowenstein, 1950). Jordan (1917) has observed the grouper  Epinephelus  s t r i a t u s o r i e n t i n g t o a stream of water by p o i n t i n g i t s t a i l toward the flow.  C u t t i n g the l a t e r a l l i n e nerves had no e f f e c t  bn t h i s response, but a n e s t h e t i z i n g t h e l i p s r e s u l t e d i n l a c k  26 of orientation. part  of the  most  one  This  h e a d , but  showing t h i s  organs involved majority  l i e v e the  greatest  seems t o be  s e n s i t i v e area  of the  fish  Jordan argues t h a t  type of  After reviewing  the  of t h i s  away a f f o r d s t h e  mouth r e g i o n .  some p a r t  lips  body and  head p o i n t i n g  as t h e  The  of  are  the  orientation with p r o t e c t i o n f o r 'the  any  f i s h ' s body i s p r o b a b l y  g r o u p e r seems t o  some o f the  v i s u a l stimulus labyrinthine  line  may  be  called  General Rheotactic  literature  t o be  the  s t i m u l i are  into play  in  troughs.  v a r i e s among t h e  Spring their before and  first their  sense  also  that  problem today  strongest,  although  important.  betac-  The  lateral  some s i t u a t i o n s .  several  i n the  significant  sculpins, catfish  five  i n t e n s i t y of t h i s  species.  long  points.  and  eels  o f the  positive  the  rheotaxis  Such v a r i a t i o n i s not  d i f f e r e n c e s can  natural habits  on t h e  i n f l o w when w a t e r i s pumped t h r o u g h  However, t h e  e x p e c t e d , and  out  salmon, t r o u t ,  move t o w a r d s t h e  only  Reactions.  m e t a l t r o u g h s have b r o u g h t spring  the  of f i s h e s , i t i s evident  Experiments i n v o l v i n g d i f f e r e n t species  Coho and  be  orientation.  of workers i n t e r e s t e d i n t h i s  and  the  an u n j u s t i f i e d c o n c l u s i o n ,  the  i n rheotaxis  tile  most s e n s i t i v e  p r o b a b l y be  un-  correlated with  species.  salmon f r y are  y e a r of l i f e , second y e a r .  and  u s u a l l y found  many of them move out  This  i n some a r e a s many s p r i n g  in rivers  to  movement i s g r a d u a l ,  salmon stay  in their  during sea  .  however,  home s t r e a m s  27 until  their  second  summer.  A careful  a n a l y s i s o f t h e me-  c h a n i s m s r e s p o n s i b l e f o r d o w n s t r e a m movement salmon has not been p u b l i s h e d . suggested here that those d e n c y t o move i n t o f a s t  explanation  fish  which  MacKinnon  show t h e s t r o n g e s t  water are those  (1950)  faster  o f two f l o w s ,  during  the f i r s t  stimuli  disappear.  A  found that  but t h a t  flow  movement  1951a). coho f r y move i n t o t h e  this  preference  two h o u r s o f o b s e r v a t i o n s ,  response to f a s t e r  ten-  most l i k e l y t o be  h a s b e e n o f f e r e d f o r t h e seaward  o f chum s a l m o n f r y ( H o a r ,  spring  However, i t i s t e n t a t i v e l y  swept away a t n i g h t when v i s u a l similar  o f young  i s greatest  a f t e r which t h e  changes t o an i n d i f f e r e n c e .  moved r e a d i l y  The coho  used f o r t h i s  study  long  troughs,  b u t d i d n o t show a c o n s i s t e n t r e s p o n s e , i . e .  they  moved u p and down t h e l e n g t h  t h a n d i d t h e s p r i n g salmon.  i n t o t h e i n f l o w end o f t h e  of the trough  w o u l d be swept  away r e a d i l y  i n t h e e x p e r i m e n t s where t u r b u l e n t side  of a p a r t i t i o n  often  I t i s suggested t h a t t h i s  o f r e s p o n s e w o u l d n o t l e a d coho f r y i n t o s t r o n g where t h e y  more  type  currents  at night.  However,  and q u i e t a r e a s  on e i t h e r  a r e a v a i l a b l e , coho almost i n v a r i a b l y  move i n t o t h e t u r b u l e n t w a t e r .  I n these  experiments,  records  o f t h e p o s i t i o n s o f t h e f i s h were made one h o u r a f t e r t h e flow  s t a r t e d o n one s i d e o f t h e p a r t i t i o n .  difference (MacKinnon,  to faster  1950),  flow  these  only  a f t e r two or t h r e e  results  of the r h e o t a c t i c r e a c t i o n .  I f c o h o show i n hours  may n o t g i v e a t r u e  Figure  6 shows t h a t  picture  whereas  28 spring f r y continue hour p e r i o d , is  the  over a  two  coho r e s p o n s e d e c r e a s e s more r a p i d l y .  It  suggested that  t o the The  contributes  e a r l y d o w n s t r e a m movement o f many s p r i n g  salmon f r y .  that  consistent  most coho f r y s t a y  i n f r e s h water l o n g e r  to their less consistent  positive  Kamloops t r o u t were s t u d i e d partitions bulent  at t h e  side.  inflow  or out  others  may  of  lakes.  of these  larger  ment i n t o f a s t  water.  downstream i n t o l a k e s upstream i n t o lakes The  high  noteworthy.  part  fish  The  the  l a r g e r ones and  i n streams  drawn a s  i n their  at n i g h t the  native  inflow side  or t h e y would  few  o f the  fish this  shown by  more  leading i n streams,  experiments  to the  likely  habitat.  The  s u g g e s t s movecarried  swim  vigorously  young c a t f i s h  s t u d y were t a k e n f r o m  Stave R i v e r ,  same h a u l s .  typical  of the  Both l a r g e Thus, t h e r e  and is  activity  r e s u l t i n the  However, t h e  lack  of  a  small no  more a c t i v e g e n e r a l l y may  is  waters  groups p r e f e r d i f f e r e n t  seem t o be  moving i n t o c u r r e n t s .  tur-  day.  used i n t h i s  d i f f e r e n t age  small  area  T h e r e t h e y would e i t h e r be  during  fish  quiet  From the be  due  troughs with  permanently  usually associate with c a t f i s h .  evidence that  the  can  i n the  c a t f i s h were t a k e n i n t h e  itates.  fry.  r h e o t a c t i c response  The  shallow, quiet anglers  as  particular fish fish  hatched  some s t a y  conclusions  percentage of  i n the  where t h e y p r e f e r r e d t h e  are  While  move i n t o l a k e s  only  is  rheotaxis.  moved i n t o t h e  These f i s h  p e r f o r m e d h e r e no fate  end,  However, t h e y  o f t e n t h a n coho. into  i n f l o w end  positive rheotaxis  fact  i n part  t o move i n t o t h e  habthan  younger  catfish  in  29  fast may  currents be o n l y The  widely a  i n nature  temporary. prickly  s c u l p i n i s a bottom d w e l l i n g  distributed  straight  suggests strong p o s i t i v e rheotaxis  flow  i n f r e s h water.  of the f i s h  i n t h e i n f l o w end o v e r a two h o u r p e r i o d . apparatus they and  showed a b o u t  quiet areas.  The f i s h  equal used  preference  i n these  that  stream f l o w i n g  e x p e r i m e n t s were  with  These f i s h  they  stay  t o descend migration  and i t i s p o s s i b l e t h a t  ries  Figure  i n contact  of t h e t r o u g h s rivers  i n quiet pools  o r behind  rocks.  r i v e r s during  the night  a t t h e t i m e o f seaward  o f young salmon.  Atlantic  of the east  cover  streams i n t o  i n turbulent  Active feeding  s c u l p i n s i n t o f a s t w a t e r where t h e y The  I t i s suggested  often rest  o b j e c t s o n t h e b o t t o m and i n c o r n e r s  (thigmotaxis)  the  o f f .the mouth o f a  i n t o Deer Lake, Burnaby.  dart f o r food.  during  eel lives  coast  S c u l p i n s a r e known  b e h a v i o u r may  on t h e bottom o f r i v e r s  and  o f N o r t h A m e r i c a , where i t h i d e s  estuar  under  d a y l i g h t and moves about more d u r i n g t h e n i g h t .  5 shows t h a t  about  50 percent  of t h e e e l s a r e i n t h e  over a f i f t e e n minute p e r i o d .  proportion  o v e r a two h o u r p e r i o d  i s maintained  With a p a r t i t i o n  preference  lead  a r e c a r r i e d downstream.  i n f l o w end o f t h e t r o u g h  dix).  were  for turbulent  s c u l p i n s p r e f e r q u i e t water near f l o w i n g  which they  with  In the p a r t i t i o n  caught on sandy s l o p i n g b o t t o m immediately small  that i s  I n the experiments  50 percent  o f water about  fish  at the i n l e t  end, t h e y  f o r the t u r b u l e n t over the quiet  This  ( s e e appenshow  area.  slight For a  30 species l i v i n g  i n t u r b u l e n t waters  for  s t r o n g f l o w might  the  e e l s , which  in this to  and t h a t  that  t o e s c a p e , were u n d e r  a true picture  of their  stress  response  c u r r e n t s was n o t o b t a i n e d . Comparisons  the  flow i s s t a r t e d  towards is  response  be e x p e c t e d , b u t i t i s p o s s i b l e  repeatedly tried  apparatus  a greater positive  may be t h a t  The t h r e s h o l d  catfish  meaning o f t h i s catfish  f o r this  spring  initial  move  response  and e e l s t h a n w i t h t h e o t h e r t h r e e  difference and e e l s  i s not e n t i r e l y  are l e s s  c e s s u c h a s shadows a n d v i b r a t i o n s . and  after  i n the long troughs before the f i s h  the inflow.  lower with  The  c a n be made o n t h e l e n g t h o f t i m e  clear,  species.  but i t  sensitive to disturbanI t was e v i d e n t t h a t  s a l m o n and s c u l p i n s were more e a s i l y  coho  d i s t u r b e d by  movements o f t h e o b s e r v e r . Data f r o m experiments of  several  in  nature.  species partly The s p r i n g  on t h e g e n e r a l r h e o t a c t i c  e x p l a i n s the behaviour o f these  and coho  s a l m o n d a t a i s most  w i t h t h e r e l a t i o n between t h e s e f i s h in their  reaction  and c u r r e n t s  fish  consistent  of water  environment.  Hormones and R h e o t a x i s . Hormone t r e a t m e n t of  sockeye  and coho  b r i n g s about  changes i n t h e r e s p o n s e s  salmon smolt t o f l o w i n g water.  p r e t a t i o n o f t h e s e changes,  The i n t e r -  however, i s n o t a s i m p l e  One  o f the c h i e f d i f f i c u l t i e s  was  d e s i g n e d t o d e t e r m i n e w h e t h e r or not t r e a t m e n t w i t h  mones a f f e c t s t h e r a t e This  change i n r a t e  lies  a t which  o f jumping  i n the apparatus,  matter.  fish  jump u p s t r e a m  s h o u l d be a r o u g h  which hor-  o v e r a dam.  measure o f  31  the  change i n g e n e r a l  in this  activity  s i t u a t i o n i s that  does not  of the  treated  s p e e d , and  an  an  increased  on  up  use  by  the  suitable  increase  i n numbers o f  activity  o f young  of d i f f e r e n t  of t h e s e  swimming latter  control  fish,  upper  pool.  e f f e c t s o f hormone g r a d u a l l y be  built  the  most  e x p e r i m e n t s was  the  d e c r e a s e o v e r a p e r i o d o f f o u r weeks i n j u m p i n g  first  Each group of f i s h over the gradually  dam  very  handling  trough.  The an  slowly  of  i s due  the  shows a  decreasing  s p e e d i n g up  controls,  the  Some  i s found.  most a p p a r e n t d u r i n g  toward  successful  the  group i n t o the  experimental  to the  jumps, b u t  salmon w i l l  fish  increased.  jumps o f the  among c o n t r o l as w e l l a s  this  of the  t y p e s of apparatus u n t i l  Another obvious f e a t u r e gradual  be  q u a n t i t a t i v e d e s c r i p t i o n of the  treatment  anomaly  s o c k e y e o c c a s i o n a l l y showed i n c r e a s e d  l e a d i n g t o s l o w e r movement of t h e accurate  The  number o f  swimming s p e e d may  were o f t e n more e r r a t i c t h a n t h e  An  animals.  a change i n a c t i v i t y  n e c e s s a r i l y lead to  jumps, e v e n t h o u g h t h e  of the  this  three  f o r the  first  the  of  adverse e f f e c t  s o o n d e c r e a s e d due  of t h e  namely, m o v i n g trials,  flow  dam  to h a b i t u a t i o n  that  including  presence of the to the  dam  and  test  coho s a l m o n s m o l t t o move  i s strong  on t h i s  then  It i s suggested  in transferring fish  increased  is  observations.  a l l fish,  t e n d e n c y f o r s o c k e y e and  area  few  jumping t i m e .  to habituation to  T h i s change  or f o u r  similar pattern,  j u m p i n g t i m e by  involved  fish.  time  and  it is felt  that  rheotactic reaction i s  (Thorpe,  1950).  32 Thyroid  Hormone and A c t i v i t y . The  of f i s h  r e l a t i o n s h i p between t h e t h y r o i d  i s not c l e a r .  the metabolic r a t e Schneider, 1939),  Treatment w i t h t h y r o x i n e i n c r e a s e s  (Root  ( B a r r i n g t o n , 1952,  of h i g h e r animals  b u t many w o r k e r s have f a i l e d  a change i n m e t a b o l i s m , consumption,in  g l a n d and a c t i v i t y  t o demonstrate  a s measured by d i f f e r e n c e  i n oxygen  f i s h e s t r e a t e d w i t h mammalian t h y r o i d  and E t k i n , 1 9 3 7 ;  Everett, 1943).  H a s l e r a n d Meyer, 1 9 4 2 ;  The t h y r o i d  b e e n shown t o have no e f f e c t (Matthews and S m i t h ,  1947).  c o n c l u d e d t h a t most f i s h However, a t l e a s t  inhibiting  drug,  extract  S m i t h and t h i o u r e a , has  on oxygen consumption o f Fundulus ( F l e i s c h m a n n , 1951) h a s  One a u t h o r  are very i n s e n s i t i v e  one e x c e p t i o n t o t h i s  s t i m u l a t i o n has been p u b l i s h e d .  Smith  lack  to thyroxine. of m e t a b o l i c (1948)  and Matthews  i n c r e a s e d t h e oxygen consumption of specimens o f Bathystoma o v e r 15 grams i n w e i g h t  by treatment  with parrot f i s h  thyroid  extract.  The s u g g e s t i o n i s made b y t h e s e a u t h o r s t h a t t h y r o x i n e  from f i s h  thyroid  malian gland.  i s more e f f e c t i v e  The t h y r o i d  t h a n t h a t f r o m t h e mam-  i s known t o be i n t i m a t e l y  c i a t e d w i t h metamorphosis o f amphibia phases o f f i s h In spite roxine  metabolism  (Hoar,  and d o e s m o d i f y  some  1951b).  of t h e l a c k o f c o n c l u s i v e e v i d e n c e t h a t  increases activity  of f i s h  through  oxygen consumption, t h e r e i s at l e a s t activity  asso-  of f i s h e s  a f t e r treatment  thy-  a change i n r a t e o f  one example o f i n c r e a s e d  with thyroxine.  Hoar e t a l  ( 1 9 5 2 ) f o u n d t h a t chum s a l m o n f r y t r e a t e d f o r one w e e k . w i t h synthetic  t h y r o x i n e showed a n i n c r e a s e i n swimming  speed,  33 and  the  slowed  swimming o f t h o s e m a r k e d l y a f t e r two  measure t h e It gland The  immersed  i n thiourea solution  weeks.  No  oxygen consumption o f t h e s e  i s now  becoming  i s related  change f r o m  increasingly  i n some way  to f i s h  p a r r t o smolt  stage  m i g r a t i n g salmonoids,  and  heightened  has been r e c o g n i z e d a t t h i s 1939,  (Hoar,  salmonoid clear or  evidence  be  (1951b)  Hoar  p a r r by t r e a t m e n t  sockeye  may  and  t o the  fact  that  (1950) held  osmotic There  balance  fish trols  the  to detect.  showed p o s i t i v e  attempted  to  trout  (1949), among No  i n either study.  This partly  H o a r and  Bell  i n chum s a l m o n f r y with  an  time.  i n the  literature Fontaine  of a  relation  (1948)  treated  f r e s h water  with  s e v e r a l d a y s o n l y 20 p e r c e n t o f  r h e o t a x i s , w h i l e 90  exhibited t h i s  coho  changes i n the  normal m i g r a t i o n time  o f t h e European e e l m i g r a t i n g i n t o  still  seen  slight  activity  rheotaxis.  After  thyroid  derivatives.  was  b).  o f young  p a r r marks were a l r e a d y  commenced and  at t h i s  i s evidence  phenylthiourea.  of the  i n some s a l m o n and  with thyroid  increased thyroid  b e t w e e n t h y r o x i n e and elvers  activity  1951  (Hoar,  i s characteristic  thyroid  have i n c r e a s e d s i l v e r i n g  i n f r e s h water past t h e i r  upset  e v i d e n t t h a t the  Further, Robertson  d e p o s i t i o n were d i f f i c u l t relate  made t o  fish.  treated with thyroxine i n t h i s  covered before treatment guanine  was  migrations  of i n c r e a s e d s i l v e r i n g  smolt  due  stage  1948).  Robertson,  (1949)  Smith  attempt  reaction.  show by h i s t o l o g i c a l  percent  Vilter  of t h e  (1944),  inspection that  these  the  con-  however  }  thyroid  34 gland  of  migrating  e l v e r s i s i n the  same s t a t e as t h a t  elvers raised i n captivity.  He  plays  It i s considered  no  part  conclusion The and  i n rheotaxis.  i s not data  based  on t h e  on  that  The  qualitative  observations, can  be  similar to that  advantageous i n t h i s  Gonad Hormones and  of  Most sex  are  f i s h e s with  that  there  may  d e m o n s t r a t e d by  u s e d by  Fry  (Bullough,  1940;  and  be  an  many a c c o u n t s i n t h e  male and  1947;  female the  sex  be  Eversole,  literature  i n d u c t i o n of Bretschneider  1941)  or  sex  by  feeding  them mammalian t e s t i c u l a r  study  The  show t h a t  a f t e r one  i n general  the  are  some  of f i s h e s a f t e r treatment.  the  swimming  s o c k e y e and  the  activity  substance,  s p e e d of  week o f t r e a t m e n t  treatments of  and  reversal  However, t h e r e  (1931) g r e a t l y i n c r e a s e d  increased  treatment  secondary  1937;  Tescher  (1952) showed t h a t  of  ( H o a r , 1951b) •  and  f r y was  apparatus.  (1948) might  Hart  Stanley  al  in  of  hormones  premature  , T a y l o r , 1948").  Hoar e t  with  swimming r a t e  change i n a c t i v i t y  tosterone.  not  increase  more r e f i n e d  e x a m p l e s of  goldfish  does  coho  Activity.  c h a r a c t e r i s t i c s (Berkowitz, Wit,  treated  respect.  of these describe  Duyvene de  evidence.  results i n altered  q u a n t i t a t i v e l y measuring the  There  Vilter's  r e s u l t s s u g g e s t , however, i n c o n j u n c t i o n  r h e o t a x i s which  fish  experimental  such treatment  thyroid  that  jump u p s t r e a m o v e r a dam  rheotaxis.  A method o f  adequate  the  r a t e a t which t h y r o x i n e  sockeye salmon smolt  demonstrate c l e a r l y  concluded that  of  with  of and  chum s a l m o n methyl  coho s m o l t  in  gonad hormones i n c r e a s e d  tes-  this the  35 a c t i v i t y of the f i s h .  T h i s i n c r e a s e was  those f i s h t r e a t e d w i t h S t i l b o e s t r o l . the  c o i n c i d e n t change i n r h e o t a x i s The  e x p e c i a l l y marked i n  The  i s not  s i g n i f i c a n c e of entirely clear.  i n c r e a s i n g s i z e o f the gonads and  of secondary sexual  the  appearance  c h a r a c t e r i s t i c s are w e l l known f e a t u r e s  o f a d u l t salmon during t h e i r spawning m i g r a t i o n .  Increased  a c t i v i t y of the gonads i s not t o be expected i n young salmon moving to sea. organs may  However, i n t e r r e l a t i o n s between the  be very  complex.  of the gonads of f i s h may gland  ( O l i v e r e a u , 1949;  It has been shown t h a t  reduce a c t i v i t y of the  Hoar, 1 9 5 1 ) .  Barrington  endocrine maturation  thyroid (1952) found  t h a t immersion o f L e b i s t e s i n t h i o u r e a s o l u t i o n f o r s e v e r a l months r e s u l t e d i n f a i l u r e of development of the germ c e l l s and  secondary sex c h a r a c t e r s .  f i s h were f e d t h y r o i d . s i t e of p r o d u c t i o n  The  The  l a t t e r appeared when the  p i t u i t a r y i s recognized  of both gonadotrophic and  hormones (Hoar, 1 9 5 1 ) , but  It should  the t r u e p i c t u r e of t h i s  be  gonads i n  s t r e s s e d t h a t the c o n c e n t r a t i o n s  t h r e e compounds a l s o v a r i e s .  The  v a r i a t i o n s might produce i n t h e  of  potency of the  d i f f e r e n c e s t h a t these  a c t i v i t y of the  fish  should  overlooked. Another v a r i a b l e i n the  the  complex  understood.  e s t r o g e n s o l u t i o n s used v a r i e d w i d e l y and  not be  the  thyrotrophic  i n t e r r e l a t i o n s h i p among p i t u i t a r y , t h y r o i d and fishes i s l i t t l e  as  sex hormone experiments  sex r a t i o among the t r e a t e d f i s h .  The  P a c i f i c salmon are w e l l d i f f e r e n t i a t e d , but  was  gonads of y e a r l i n g no method has  yet  36 been d e v i s e d f o r d i f f e r e n t i a t i n g  the sexes f r o m  external  characteristics. Temperature The  and  Activity.  role  of temperature  i n the  movement o f  young s a l m o n  is still  opinion that  i t i s i m p o r t a n t as a d e p a r t u r e s t i m u l u s  1937).  (Foerster, increased current months.  uncertain.  seaward  Hoar  activity  and  (1951)  Some w o r k e r s  found that  a marked t e n d e n c y  as h a t c h e r y t e m p e r a t u r e s  no t i m e do  salmon  swim a c t i v e l y  chum f r y show t o swim w i t h t h e  increase  On the o t h e r h a n d , Huntsman  are o f the  during the  summer  (1948)- s t a t e s t h a t  downstream w i t h t h e  at  current.  On t h e b a s i s o f many o b s e r v a t i o n s of chum f r y and smolt it  i n the rheotaxis  i s concluded that  temperatures, t u b s i s not  tubs used f o r temperature  n e g a t i v e r h e o t a x i s does  and t h a t  active  simply a f a i l u r e (1937)  Foerster f r o m C u l t u s Lake  has  of positive  shown t h a t  and  i t i s suggested that  t o 5 « 0 ° C,  increases,  lead  to active  sudden  salmon  and  o f the  at the  From t h e  experiments  elevation  In conclusion, p o s i t i v e  As t h e  above evidence performed  i n temperature  n e g a t i v e r h e o t a x i s by coho s m o l t and  r i v e r s , thus hastening t h e i r  migrate  an o v e r t u r n o f the w a t e r s i n  as a r e s u l t  here  in  rheotaxis.  s m o l t move o u t of t h e l a k e .  i n the l i t e r a t u r e  occur at h i g h  sockeye  at temperatures of 4 . 4  t h e l a k e , t h e mean t e m p e r a t u r e sockeye  experiments,  downstream movement i n t h e s e  warmer s p r i n g t e m p e r a t u r e s c a u s e  range,  eoho  chum f r y  d o w n s t r e a m movement. rheotaxis  may  h a s b e e n shown i n  37 several  species  degree of normally  o f f r e s h w a t e r and  activity living  i n the  response.  is  only  stream. strong  will  be  gen  such  s a l m o n and  relation  and  are  that  sculpins, hold  the  such f i s h  position  n i g h t when v i s u a l  a l l of these  stimuli  testosterone not  and  definite,  hormones i n c r e a s e  sockeye y e a r l i n g s about a l a k e  hormonal l e v e l  by  the  an  environmental r e l e a s e r l e a d i n g to  of  activity,  an  a c t i v e swimming  which  through  t r o u t i n t o f a s t w a t e r s where  general  i n the  blood.  i n some s p e c i e s downstream.  they  estro'  indicaactivity  I t i s suggested  may  movements o f  be  Temperature  initiated  is  probably  a more s p e c i a l i z e d  at l e a s t  may  aire  three but  a p p e t i t i v e behaviour leading to r e s t l e s s as  however,  Active positive rheotaxis  is still  most  position in a  l e a d t o more a c t i v e p o s i t i v e r h e o t a x i s .  that  fish  showing the  positive rheotaxis,  of t h y r o x i n e ,  compounds t o r h e o t a x i s  tions  as  swept downstream a t The  flowing waters  method u s e d t o m a i n t a i n  p o s i t i v e thigmotaxis.  some y o u n g  lost.  fastest Sustained  Some f i s h e s ,  lead  The  i n c u r r e n t s of water v a r i e s , those  consistent not t h e  diadromous f i s h .  takes  the  form  form  of  38  SUMMARY  1.  The  tendency  flowing 2.  of  stream  of  each  artificially There  is  some  and  coho  shorter  An e s t r o g e n , Qualitative  5.  the  smolt.  Migration appetitive some and  body  by  observations  move  between  degree  of  into  the  a  natural  activity  in  to  has  of  confirm  4 to  negative  is  Pacific  sex  sockeye in  over  marked  a  the dam.  effect.  results.  5°  C.  above  rheotaxis  s a l m o n may  initiated  controlled,  by water  these  in  reflected  upstream  most  and  the in  chum  smolt.  young  which  is  jump  the  thyroxine  response  increase  fish  salmon  in  rheotactic  produces  behaviour  directed  to  measured.  increase  temperature  downstream  hormones,  the  This  Stilboestrol,  coho  fish  currents.  required  and  been  and  enhances  in  of  suggested  that  temperature  salmon f r y  been  evidence  Sudden e l e v a t i o n holding  has  has  species  salmon time  species  water  created  hormone; l e v e l  4.  of  Some c o r r e l a t i o n habitat  3.  several  currents.  in  part,  by by  be  increase  in  temperature  39  ACKNOWLEDGMENTS  Financial  assistance  i n t h e f o r m o f a summer  scholarship from the National  Research  Council  i s greatly-  appreciated. Thanks a r e extended  t o F.P. Maher and G.E. S t r i n g e r  o f t h e F i s h e r i e s Management D i v i s i o n o f t h e B.C. Game Commission f o r aid i n collecting The w r i t e r  fish.  i sparticularly  i n d e b t e d t o D r . W.S.  of t h e Department of Z o o l o g y f o r a s s i s t a n c e , inspiration are  extended  g u i d a n c e and  throughout the course of t h e p r o j e c t . t o D r . W.A.  Zoology, f o r c o n s t r u c t i v e  C l e m e n s , Head criticisms  Hoar  Thanks  o f t h e Department o f  of t h e manuscript.  40  LITERATURE  Barrington,  CITED  E.J.W.  The  Thyroid  parative  physiology.  gland:  a problem 13  New B i o l o g y ,  in :  com61  -  79,  1952. Berkowitz,  P.  Effects  of  reticulatus  estrogenic  (Guppy).  substances i n  Proc.  Soc.  Exp.  Lebistes Biol.  Med.,  36 : 416 - 4 1 8 , 1 9 3 7 . BretSchneider,  L.H.  and  rinology  of  J . J . Duyvene  de  non-mammalian  Wit.  Sexual  vertebrates.  endoc-  Elseiner,  1947. Buddenbrock,  W.  von.  Yergleichende  Sinnesphysiologie. Bullough,  W.S.  A study  laevis Clausen,  R.G.  L.).  S.  The  steroids  20  W.  R.E.  fresh  I, 1952.  Basel,  in  the  minnow  (Phoxinus  :  475  -  1940.  85  Zool.,  water  Seitenorgane 162  effects  of  501,  fishes.  E c o l o g y , 12  migration  :  nerka).  J.  development  physiology  young Biol.  Amer.  of  in  of  Can.,  and fish :  the  vergl.  salmon  J:  related (Lebistes  6O3-6IO, thyroid  Lecture  temperature  sockeye Bd.  Z.  1933.  pregneninolone  glands.  relation of  214,  an F i s c h e n .  E n d o c r i n o l o g y , 28  Comparative  The  -  on sexual  parathyroid Foerster,  Exp. in  :  reticulatus). Fleischmann,  Birkhauser,  sex r e v e r s a l  Function der  W.J.  Verlag  Band  546, 1931.  Physiol., Eversole,  J .  Orientation  541 Dykgraaf,  of  Physiologie.  Series,  to  the  1941. and  118,  seaward  (Oncorhynchus  421-438, 1 9 3 7 .  1951.  41 F o n t a i n e , M.  Du r o l e joue par l e s facteurs i n t e r n e s dans  c e r t a i n e s m i g r a t i o n s de p o i s s o n s :  Etude  de d i v e r s e s methodes d i n v e s t i g a t i o n . f  15 F r a e n k e l , G.S.  : 284-294,  1948.  and D.L.  Gunn.  Oxford,  critique  J. Conseil,  The o r i e n t a t i o n o f animals.  1940.  F r y , F.E.J, and J.S. H a r t .  C r u i s i n g speed of g o l d f i s h i n  r e l a t i o n t o water temperature.  J . F i s h . Res.  Bd.  Can., 7 •: 169-175, 1948. Garrey, W.E.  A s i g h t r e f l e x shown by s t i c k l e b a c k s .  8 : 79-84-, Gray,  J.  H a s l e r , A.D.  Bull.,  1904  Pseudo-rheotropism  95-103,  Biol.  in fishes.  J . Exp. B i o l . , 14  :  1937.  and R.K.  Meyer.  R e s p i r a t o r y responses of  normal  and c a s t r a t e d g o l d f i s h t o t e l e o s t and mammalian J . Exp. : z b o l . , 91  hormones. Hoar, W.S.  : 391-404,  1942.  The t h y r o i d gland o f the A t l a n t i c salmon. Morph., 65  Hoar, W.S.  : 257-295,  J.  1939.  The behaviour of chum, pink and coho salmon i n r e l a t i o n t o t h e i r seaward m i g r a t i o n .  J . Fish.R'e.s, Bd.  Can., 8 : 2 4 1 - 2 6 3 , 1951a. Hoar, W.S.  Hormones i n f i s h . 59  Hoar, W.S.  a  nd  : Pub. G.M.  Univ. Toronto Stud. B i o l .  Ont. F i s h . Res. Lab., 71 Bell.  1951b.  The t h y r o i d g l a n d i n r e l a t i o n t o  the seaward m i g r a t i o n of P a c i f i c Z o o l . , 28  : 1-51,  Ser.,  : 126-136,  1950.  salmon.  Can. J .  42 Hoar,  W.S.,  D.  MacKinnon and  hormones 30  Zool., Hora,  S.L.  on the :  tachment.  Phil.  171-282, Huntsman,  A.G.  special  of  Effects  of  salmon f r y .  some  Can.  J .  1952.  bionomics  with  Redlich.  behaviour  273-286,  Ecology,  fauna,  A.  and  evolution  reference  Trans.  Roy.  to  of  the  Soc.  the  torrential  organs  London,  of  218  at:  1930.  Salmon and  animal  migration.  161  Nature,  :  3 0 0 - 3 0 2 , 1948. Jordan,  H.  Rheotropic  Block. Keenleyside,  Amer.  M.H.A.  sculpin chub  responses J.  asper  (Mylocheilus Dept.  of  Epinephelus  patterns  Richardson)  caurinus Zoology,  striatus  43 : 4 3 8 - 4 5 4 ,  Physiol.,  Some b e h a v i o u r  (Cottus  thesis,  of  of  1917.  the  and t h e  peamouth  (Richardson)). Univ.  of  prickly  B.A.  British  Columbia,  1952. 0.  Lowenstein,  Labyrinth 4  Biol., Lyon,  E.P.  Physiol.,  E.P.  eye.  D.  equilibrium.  I  II  J.  keta) special  of  the  and t h e  Rheotropism  the  to  the  o n some  thesis,  Zoology,  1950.  of  Exp.  fishes.  Amer.  of  current,  effect of  fish  blind  in  2 4 : 2 4 4 - 2 5 1 , 1909.  salmon f r y  and t e s t o s t e r o n e Dept.  in  light  chum s a l m o n m i g r a n t  coho  reference  Soc.  1904.  Physiol.,  A c o m p a r i s o n of  behaviour  Rheotropism  12:149-161,  Amer.  Symp.  1950.  On r h e o t r o p i s m .  one MacKinnon,  60-82,  On r h e o t r o p i s m .  J. Lyon,  :  and  (0. of  these  Univ.  of  and  grouping  (Oncorhynchus  kisutch)  with  thyroxine, reactions. British  thiourea M.A.  Columbia,  43  Matthews,  S.A.  and D.C.  Smith.  The  effect  oxygen consumption o f Fundulus. 20  Myers,  :  G.S.  161-164,  Usage  o f t h i o u r e a on t h e Physiol.  Zool.,  1947.  o f anadromous, c a t a d r o m o u s and  allied  t e r m s f o r m i g r a t o r y f i s h e s . Cope.ia,.. 1 9 4 9 ( 2 ) O l i v e r e a u , M.  L ' a c t i v i t e t h y r o i d i e n n e de  L.  au c o u r s d u c y c l e  143  : 247-250,  Robertson,  The  thyroid  C.R.  occurrence of increased  gland  i n rainbow t r o u t  : 282-295,  R o b e r t s o n , O.H. trout  110  R o o t , R.W.  by i n t e r m u s c u l a r  Effect  oxygen  F i s h migration . B i o l .  174-175,  P r o c . S o c . Exp.  Biol.  19375  of feeding  Rev.,  1 2 : 320-337, 1 9 3 7 .  t h y r o i d substance.  1 4 : 341-450, 1 9 3 9 .  Q u a r t . Rev. B i o l . , and G.M.  smolt stage i n rainbow  of t h y r o x i n e on  E.S.  S m i t h D.C.  Everett.  The  effect  of t h y r o i d  hormone  on growth r a t e , t i m e of s e x u a l d i f f e r e n t i a t i o n oxygen consumption i n the f i s h , J. S m i t h , D.C.  Exp.  Z o o l . , 94  and S.A.  : 229  Matthews.  and i t s e f f e c t  Zool.,  Zool.,  37  Effects  Physiol.  J . Exp.  Med.,  S c h n e i d e r , B.A.  smolt.  hormone.  c o n s u m p t i o n of t h e t o a d f i s h .  Russell,  of the  1949.  W . Etkin.  :  activity  i n j e c t i o n o f mammalian t h y r o i d  and t h y r o t r o p i c  :337-355,  and  Paris,  1948.  P r o d u c t i o n of s i l v e r y  extract  Soc. B i o l .  at the time of t r a n s -  formation from parr to s i l v e r y 21  canicula  1949.  !  O.H.  sexuel.  Scyllium  89-97.  :  -240,  Lebistes  and  reticulatus.  1943.  Parrot f i s h t h y r o i d  extract  upon oxygen consumption i n t h e  fish  44 Bathystoma. Smith,  S.B.  Amer. J . P h y s i o l . , 153  The e f f e c t s  o f t h y r o x i n e and r e l a t e d compounds  on young salmon and t r o u t .  B.A. t h e s i s ,  Zoology, Univ. of B r i t i s h Columbia, Snedacor, G.W.  : 215-221,1948  S t a t i s t i c a l Methods.  Dept. o f  1949.  Iowa State C o l l e g e  P r e s s , Ames, 1946. S t a n l e y , L.L. and G.L. Tescher. testicular  A c t i v i t y of g o l d f i s h  substance d i e t .  on  E n d o c r i n o l o g y , 15 :  55 - 5 6 , 1 9 3 1 . S t r i n g e r , G.E.  An experimental study of some v i s u a l l y r e -  l e a s e d behaviour p a t t e r n s i n young coho salmon and kamloops t r o u t . Univ. T a y l o r , A.B.  M.A. t h e s i s ,  o f B r i t i s h Columbia,  Dept. of Zoology,  1952.  Experimental sex r e v e r s a l i n the r e d s w o r d t a i l  hybrid Xiphophorus-Platypoecilus.  Trans. Amer.  M i c r . S o c , 6 ? : 155-164, 1 9 4 8 . Thorpe, W.H.  The concepts o f l e a r n i n g and t h e i r  to those o f i n s t i n c t .  relation  Symp. Soc. Exp. B i o l . , 4 :  387 - 4 0 8 , 1 9 5 0 . Tinbergen, N.  The h i e r a r c h i c a l  o r g a n i z a t i o n o f nervous  mechanisms u n d e r l y i n g i n s t i n c t i v e behaviour.  Symp.  Soc. Exp. B i o l . , 4 : 305-312, 1950. V i l t e r , V.  Rheotropisme de l a C i v e l l e  C R . Soc. B i o l . P a r i s ,  et a c t i v i t e t h y r o i d i e n n e  138 : 6 6 8 - 6 6 9 , 1944.  45  APPENDIX  Page Data  on G e n e r a l  Response  Table  1.  Sculpins  Table  2.  Eels  Table  3.  Catfish  to  Currents.  i i i i i i  i  Table  1.  Percent  sculpins  and t h i r d  hours  Percentages  for  in  inflow  of  flow.  six  end d u r i n g Figures  Third i  - 3 0 second intervals  1 2  7  58.3 51.4 47.2  8 -  33.3 48.6  18  51.4 44»4 50.0 43.1 34.7 44* 4 45.8  19 20 21 22  33-3 36.1 56.9 52.8  23 24 25 26 27  34.7 45.8 41.7 54.2 52.8  29 30  34.7 37.5 45.8  13 14 15 16 17  28  fish  mean  hour  ; Time-  i 3 0 second intervals  1 2  55.6 59.7 47.2 50.0 50.0 54.2  3 4 5 6  9 10 11 12  Percent  are  experiments.  Second hour  Time  second  3 4 5 6 . '  7 8. 9 10 11 12 13 14 15 16 17  18 19 20 21 22 23 24 25 26 27  28 29 30  Percent  65.3 59.7 50.0 55.6 54.2 55.6 54.2 55.6  51.4 56.9 . 51.4 56.9 50.0 40.3 44*4  51.4  54.2 50.0 48.6 58.3 56.9 54.2 65.3  61.1  50.0 56.9 63.9 56.9 66.7 56.9  fish  11  Table  2.  Percent hours six  eels  of  in  flow.  inflow  end  Figures  during  are  mean p e r c e n t a g e s  - 30 s e c o n d P e r c e n t intervals  1 2 3 4 5 6 7  8  9 10 11 12  13  14  15  16 17 18 19 20 21 22  23 24 25 26 27 28  29 30  third for  experiments.  Second hour  Time  second and  43.1 41.7 40.3 44.4 54.2 54.2 51.4 45.8 48.6 55.6 40.3 58.3 59.7 61.1 63.9 • 54.2 54.2 51.4 55.6 56.9 56.9 55.6 45.8 59.7 • 55.6 59.7 56.9 55.6 56.9 61.1  Third  fish  Time  hour  - 30 s e c o n d P e r c e n t intervals  1 2 3 4 5 6 7 8 9  10 11 12  13 14 15 16 17 18 19  20 21 22 23 24 25 26 27 28  29 30  51.4 55.6 52.8 52.8 48.6 50.0 58.3 52.8 52.8 50.0 52.8 48.6 50.0 56.9 5^.3 55.6 59.7 54.2 55.6 55.6 56.9 54.2 54.2 56.9 52.8 68.1 53.3 58.3 61.1 62.5  fish  iii  T a b l e 3,  Percent c a t f i s h i n i n f l o w end during second and third  hours o f f l o w .  for eight  F i g u r e s are mean percentages  experiments.  Second hour Time - 30 second intervals  1 2 3 4 5 6 7 8  9  10 11 12 13  14  15 16  17 IS  19 20 21 22 23 24 25  26  27  28  29 30  Percent f i s h  87.5 74.0 71.9 77.1 72.9 70.8 76.0 58.3 69.8 76.0 55.2 65.6 63.5 65.6 70.8 69.8 74.0 77.1 63.5 66.7 80.2 79.2 78.1 80.2  81.3  76.0 79.2 6I.5 74.0 83.3  T h i r d hour Time - 30 second intervals  1 2 3 4 5 6 7 8 9 10 11 12 13 14  15  16 17 18 19  20 21 22 23 24 25 26 27 28 29 30  Percent  61.5 71.9 70.8 64.6 62.5 71.9 60.4 67.7 69.8 58.3 6I.5  65.6  74.0 67.7 75.0 75.0  71.9 71.9  74.0  72.9  77.1 80.2 66.7 74.0 76.0 8I.3 76.0 78.1 76.1 83.3  fish  

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