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The influence of temperature, salinity and photoperiod on aggregations of underyearling chum salmon,… Shelbourn, John Edward 1964

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THE INFLUENCE OP TEMPERATURE, SALINITY AND PHOTOPERIOD ON AGGREGATIONS OF UNDERTEARLING CHUM SALMON, ONCORHYNCHUS KETA (WALBAUM) by JOHN EDWARD SHELBOURN B.Sc. (Hons.), U n i v e r s i t y of B r i t i s h Columbia, 1963  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Zoology  We accept t h i s t h e s i s as conforming to the r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA September, 1964  i  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  the requirements f o r an advanced degree a t the  University  of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference  and  study.  I f u r t h e r agree  t h a t permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may  be granted by the Head of my  or by h i s r e p r e s e n t a t i v e s .  Department  I t i s understood t h a t copying or  p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not allowed without my  written  permission.  ( J . E.  Department of Zoology The U n i v e r s i t y of B r i t i s h Columbia Vane ouver 8, Canada 14 September  1964  Shelbourn)  be  ABSTRACT U n d e r y e a r l i n g chum f r y were h e l d i n f r e s h water and s a l t water a t two d i f f e r e n t temperatures and under two d i f f e r e n t photoperiods. acclimation. water  The f i r s t t e s t s were made a f t e r f o r t y days Aggregations were greater i n s a l t - than i n f r e s h -  (p < 0.01).  A t the lower temperature the f i s h were more  aggregated than they were a t the higher temperature  (p < 0 . 0 5 ) .  Photoperiod e f f e c t s were not s i g n i f i c a n t l y d i f f e r e n t . b i o l o g i c a l meaning of these r e s u l t s i s d i s c u s s e d .  The  I t i s con-  cluded t h a t , under the c o n d i t i o n s of t h i s experiment, chum salmon f r y show true s c h o o l i n g (as d e f i n e d by K e e n l e y s i d e , 1955) only i n s a l t water.  vii ACKNOWLEDGEMENTS I would l i k e to thank Dr. W. S. Hoar f o r h i s encouragement and a s s i s t a n c e d u r i n g t h i s  study.  Dr. ?. S. Hoar, Dr. C. C. Lindsey, Dr. I . E . E f f o r d and Dr. J . T. McFadden c r i t i c i s e d the manuscript. for  Their  suggestions  improvement were much a p p r e c i a t e d . The f o r m u l a t i o n of the aggregation  J . T. McFadden.  index was due to Dr.  H i s help w i t h the s t a t i s t i c a l a n a l y s i s was  e s s e n t i a l t o the i n t e r p r e t a t i o n of the data. Chum f r y were made a v a i l a b l e through Mr. Dixon MacKinnon of the P i s h Culture Branch, Department of F i s h e r i e s .  They were  r e a r e d by Mr. J . G. Terpenning of the P a c i f i c Salmon Commission at the Smith P a l l s Hatchery, Cultus Lake, B. C. This study was made p o s s i b l e by a F i s h e r i e s A s s o c i a t i o n of B. C. S c h o l a r s h i p to the author and by N a t i o n a l Research C o u n c i l of Canada " g r a n t s - i n - a i d " to Dr. ¥. S. Hoar.  iii TABLE OF CONTENTS page Introduction  1  M a t e r i a l s and Methods  6  A.  P r e l i m i n a r y Studies i) ii)  B.  6  Stagnant-water t e s t s  6  Flowing-water t e s t s  7  1964 Studies i)  Holding  7 conditions  7  ii)  T e s t i n g apparatus  9  iii)  T e s t i n g technique  11  Results  12  A*  P r e l i m i n a r y Experiments: 1963 Observations  12  B.  1964 Observations  16  Discussion A*  31  The Experimental R e s u l t s Compared With Those of Some Other Workers  B«  31  The B i o l o g i c a l S i g n i f i c a n c e of the Experimental R e s u l t s i) ii) iii)  33  Salinity effects  33  Temperature e f f e c t s  35  Photoperiod  36  effects  Conclusions  37  References C i t e d  40  Appendix A  Raw data f o r a n a l y s i s of variance  42  Appendix B  Replicate tables  43  T o t a l of R e p l i c a t e s t a b l e  44  TABLE OP CONTENTS (Cont.) page Appendix C  M o r t a l i t y of f r y i n the summer of 1963  Appendix D  References on s c h o o l i n g behaviour taken from Shelbourn (1963) and elsewhere  45  48  V  LIST OP TABLES Table I II  III IV V VI  VII  page Gross t o t a l s f o r the 1964 Chi-square  tests  15  values f o r each d i s t r i b u t i o n  p a t t e r n i n the t e s t i n g tank  17  Temperature e f f e c t s  19  Salinity effects  19  Photoperiod  19  effects  A n a l y s i s of v a r i a n c e f o r the 1964 Model I A n a l y s i s of variance f o r 1964  data, 20  data,  Mixed Model VIII  P a r t i a l a n a l y s i s of v a r i a n c e f o r the  25 1964  data, Mixed Model c o n s i d e r i n g blocks 1-3 only 27  LIST OP FIGURES Figure  page  1  The  1964  t e s t i n g tank  2  Temperature e f f e c t s f o r the f o u r blocks  22  3  S a l i n i t y e f f e c t s f o r the four blocks  23  4  Photoperiod  24  5  The  e f f e c t s f o r the four blocks  8  s a l t water minus f r e s h water t o t a l s  i n each b l o c k f o r the four h o l d i n g tanks  28  1 INTRODUCTION At present n e i t h e r the nature nor the mechanisms of s c h o o l i n g i n the P a c i f i c t o r i l y explained.  salmon (genus Oncorhynchus) are  satisfac-  C o n f l i c t i n g r e p o r t s on n a t u r a l observations  and experimental r e s u l t s are to be found i n the  literature.  Hoar (1951) showed a p o s i t i v e r h e o t a c t i c response f r y under experimental c o n d i t i o n s .  I t was  i n chum  also said that i n  the streams these f i s h were u s u a l l y seen i n d a y l i g h t swimming i n t o the c u r r e n t s a t the time of m i g r a t i o n , maintaining t h e i r position.  The mechanism suggested f o r the n o c t u r n a l downstream  m i g r a t i o n i n chum f r y was  a) the tendency  of the f i s h to r i s e  to the surface as l i g h t decreased coupled with the r h e o t a c t i c response.  A c t i v i t y was  b) a f a i l u r e i n  s a i d to i n c r e a s e a t n i g h t .  This i s emphasized i n Hoar (1953) " ... j u v e n i l e seaward-moving salmon are a c t i v e and v i g o r o u s , but, a t the same time, c a r r i e d seaward by the c u r r e n t s . " (op. c i t . p. 439). Neave (1955) observed the behaviour i n nature.  (He claimed t h a t there was  t h a t chum behaviour was  of p i n k salmon f r y  no evidence to  essentially different).  Pink f r y showed  "negative r h e o t a x i s " during t h e i r downstream m i g r a t i o n . were moving s i n g l y and a t n i g h t . day.  Few  suggest  They  f r y were seen during the  In s l a c k ( t i d a l ) water the migrants were swimming randomly  and were more u n i f o r m l y d i s t r i b u t e d than i n the stream. p o s i t i v e r h e o t a x i s of f r y was captive  The  a post-migratory behaviour i n  fish.  Hoar (1956) p o i n t e d out t h a t h i s observations of chum and p i n k salmon i n experimental tanks showed t h a t these f i s h p r e f e r r e d  2 l i g h t and showed p o s i t i v e r h e o t a x i s .  Chum salmon captured a t  n i g h t and r e l e a s e d during the day would h o l d p o s i t i o n s i n the c u r r e n t but would have moved away by the next morning.  Exper-  imental observations showed t h a t chum schools were somewhat loose.  In c i r c u l a r aquaria the r a p i d l y swimming chums formed  a file-like  formation.  Hoar ( p e r s . comm.) c o n s i d e r s t h a t the  chum salmon i s l e s s s t r o n g l y schooled than the p i n k . his  Comparing  experimental r e s u l t s with Neave's (1955) f i e l d o b s e r v a t i o n s ,  Hoar, r e f e r r i n g to p i n k and chum f r y , s a i d "Not only i s the behaviour of s c h o o l i n g f r y ••• d i f f e r e n t from t h a t o f n o c t u r n a l m i g r a t i n g i n d i v i d u a l s which have never schooled, but d e f i n i t e d i r e c t i o n s of swimming are probably e s t a b l i s h e d ... independently of r h e o t a c t i c responses .... a f t e r the f r y have schooled they no longer seek the p r o t e c t i o n of the g r a v e l and stones but r e l y on the p r o t e c t i o n of the school and i t s a s s o c i a t e d advantages". (Hoar, 1956, p, 323). F u r t h e r experiments  (Hoar e t a l , 1957) showed t h a t chums  p r e f e r r e d l i g h t e d areas when given a choice between those and dark ones. will  These authors recorded t h a t chum f r y when scared  hide under stones, whereas p i n k f r y w i l l  stones.  s c a t t e r above the  Pink f r y are l e s s dependent on the p r o t e c t i o n of the  stones once they have schooled than chums are i n a s i m i l a r  sit-  uation. Neave had denied t h a t schools of pink f r y could be seen i n nature during the day, whereas Hoar's experiments ted  schools of both pinks and chums a t t h i s time.  demonstra-  McDonald  ( i 9 6 0 ) , on the other hand, claimed t h a t s c h o o l i n g was not observed to  occur f o r most of the downstream m i g r a t i o n of chum, coho,  p i n k or sockeye  fry.  I n d i v i d u a l s but not schools were observed  3 i n the spawning streams i n both d a y l i g h t and darkness.  McDonald  admitted t h a t some schools of chum f r y were seen a t the mouth of the  r i v e r system i n which they were spawned (Lakelse R i v e r , B.  C.)  and a l s o f u r t h e r downstream i n the q u i e t waters of the main r i v e r of  the system (Skeena R i v e r , B. C . ) .  The v a r i a t i o n among chum  catches a t d i f f e r e n t times i n the spawning-stream great enough to suggest s c h o o l i n g . the  arguments  the  f r y trapped i n the spawning  initial  t r a p s was not  I t might be p o s s i b l e to combine  of Hoar (1956) and McDonald here and suggest t h a t stream had not y e t undergone  the  s c h o o l i n g r e a c t i o n , whereas t h i s had occurred i n the f i s h  seen f u r t h e r downstream.  I t i s obvious t h a t the nature of the  aggregative behaviour of chum f r y i n f r e s h water has not been completely c l a r i f i e d by these workers. Mclnerney (1961), i n s a l i n i t y p r e f e r e n c e s t u d i e s , made notes on the group behaviour of P a c i f i c salmon f r y .  His r e s u l t s  showed an increase i n the s i z e of groups c r o s s i n g the s a l t water/ f r e s h water p a r t i t i o n of the tanks from the beginning of June u n t i l the t h i r d week i n J u l y .  A decrease i n group s i z e f o l l o w e d  u n t i l i t was almost u n i t y by the f i r s t week i n September.  This  study was not c a r r i e d out w i t h s a l t - w a t e r f r y , making d i r e c t comparisons w i t h these present experiments i m p o s s i b l e . Houston in  (1959) showed that chum f r y would swim more slowly  s a l t water than i n f r e s h water a t maximum s u s t a i n e d speed.  These f i s h were only i n s a l t water f o r some 36 hours.  Houston s f  study i n d i c a t e d t h a t the l o s s of maintained swimming speed was due to the i n c r e a s e d demand f o r energy to do osmotic work i n the  4 s a l t water  environment.  These two papers above do not d e a l p r e c i s e l y w i t h the s u b j e c t matter of t h i s present paper, but they do touch on some aspects to be d i s c u s s e d a f t e r the p r e s e n t a t i o n of the r e s u l t s obtained* The nature of s c h o o l i n g i n f i s h e s was  extensively discussed  by Shelbourn (1963) and i t i s not proposed to repeat t h a t d i s c u s s i o n here,  A l i s t of r e f e r e n c e s from t h a t paper  at the end of t h i s one,  (v. Appendix D).  c r i t e r i o n f o r s c h o o l i n g was  appears  K e e n l e y s i d e s (1955) 1  adopted i n the 1963 paper and i s  s t i l l used i n t h i s one, i . e .  "an aggregation where one  fish  r e a c t s to ,.. other f i s h by s t a y i n g near them". A recent paper by Okuno (1963) records observations on 130 s p e c i e s of marine f i s h e s w i t h regard to t h e i r s c h o o l i n g behaviour i n nature and i n c a p t i v i t y , and c o n t a i n s comments on the type of "chasing behaviour" observed.  T h i s extensive work  covers 76 genera, 35 f a m i l i e s , 12 suborders and 5 orders of fishes —  from which the f a m i l y Salmonidae  i s excluded.  However,  the r e l e v a n t p o i n t i s t h a t Okuno found a change i n s c h o o l i n g behaviour i n some of these f i s h when they were t r a n s f e r r e d from the ocean to small a q u a r i a , but not when they p l a c e d i n a l a r g e tank.  This problem  enters i n t o the s u b j e c t matter of the t h e s i s  and w i l l be d i s c u s s e d l a t e r . The c o n s i d e r a t i o n s of chum salmon f r y behaviour which p r o v i d e d the problems f o r the present work were as f o l l o w s . F i r s t l y , Mclnerney  (1961) showed t h a t s c h o o l i n g behaviour peaked  towards the end of the downstream migratory p e r i o d and then  5 decreased to low l e v e l .  I f t h i s event was  meaningful i t  might c o r r e l a t e w i t h a p e r i o d of e s t u a r i n e residence before p o p u l a t i o n moved i n t o the open waters.  The  noted by Mclnerney would be more appropriate  increase i n  the  aggression  to r e s i d e n t i a l  f i s h e s than to schooled, migrant ones. Secondly, i f t h i s h y p o t h e t i c a l r e s i d e n t i a l behaviour i s r e a l , what are the r e l e a s e r s ?  P r e l i m i n a r y s t u d i e s were con-  ducted i n f r e s h water tanks to a s c e r t a i n the e f f e c t s of changing the d e n s i t i e s of f i s h , changing the s p a t i a l c o n f i g u r a t i o n of the tank, and  of f e e d i n g .  The r e s u l t s were h i g h l y v a r i a b l e and  d i d not produce a change i n behaviour.  Repeated, s i m i l a r exper-  iments might have provided d e f i n i t e r e s u l t s but the p r o j e c t abondoned i n favour described l a t e r .  of a r a d i c a l l y d i f f e r e n t t e s t which w i l l  To provide  the background f o r the new  was be  tests,  the p r e l i m i n a r y s t u d i e s w i l l be o u t l i n e d b r i e f l y . The  hypothesis  developed from the p r e l i m i n a r y experiments  i s t h i s ; since e x t e r n a l f a c t o r s do not a f f e c t the s c h o o l i n g of l a r g e groups of f i s h (>20) phenomenon.  schooling i s an i n n a t e , maturation  I t w i l l be r e l e a s e d by f a c t o r s which a f f e c t  the  growth r a t e of the f i s h ; l i g h t , temperature and the s a l t water environment. the degree of  Changes i n the l e v e l s of these f a c t o r s w i l l change aggregation.  6 MATERIALS AND METHODS T h i s study was conducted over a p e r i o d of two years on the f r y of the chum salmon, Qncorhynchus k e t a .  In the f i r s t  year w i l d coho f r y (0. k i s u t c h ) were used to provide a c o n t r a s t to the chums.  The chums were hatchery reared i n both y e a r s .  A.  P r e l i m i n a r y Studies  Chum f r y were obtained from Smith P a l l s Hatchery, Cultus Lake, B. C. on A p r i l 15, 1963.  They were f e d three  times  d a i l y w i t h f r e s h - f r o z e n b r i n e shrimp * and r e c e i v e d standard aquarium care and a t t e n t i o n . Coho f r y were caught i n the Cheakamus R i v e r , B. C. on the 11th and 15th of June, 1963.  They were t r e a t e d s i m i l a r l y  to the chums. A d a i l y m o r t a l i t y r e c o r d was kept f o r a l l these  fish.  M o r t a l i t y i s d i s c u s s e d i n Appendix C.  i)  Stagnant-water t e s t s  Aerated a q u a r i a were used f o r these t e s t s . f r y were observed  F o r t y chum  i n an aquarium 182 cm long x 20 cm wide.  A  second s i z e 60 x 30 cm was used t o h o l d 30 chums i n some t e s t s and three chums i n other  tests.  Obtained from The Wardley Brine Shrimp Company, Watrous, Saskatchewan.  7 i i ) Flowing-water  tests  Observations were made on f i s h h e l d i n metal measuring 244 x 26.5 cm. non-toxic p a i n t .  tanks  The tanks were p a i n t e d w i t h "Rustoleum"  During a five-minute o b s e r v a t i o n the a c t i v i t y  of the f i s h was recorded by counting each f i s h as i t passed under a s t r i n g s t r e t c h e d mid-way across the tanks.  In a d d i t i o n ,  the number of "chases" and " n i p s " was recorded i n the f i v e minute period.  Both chum and coho, i n groups of v a r i o u s sizes, were  observed i n these tanks. some t e s t s .  Artificial  landmarks were i n c l u d e d i n  In other t e s t s the f i s h were not f e d f o r s e v e r a l  days p r i o r to t e s t i n g . B. i)  1964 S t u d i e s  Holding c o n d i t i o n s  Chum f r y were obtained from the Smith F a l l s Hatchery on 17 A p r i l , 1964. They were held i n four concrete troughs with temperature  and photoperiod c o n t r o l l e d as f o l l o w s :  Tank A  Temperature  Photoperiod  9-12°C (seasonal)  8 hours  B  "  C  7°C  D  7°C  "  .16-17.5 hours (seasonal) "  " 8 hours  On May 21, f o u r metal troughs p a i n t e d with grey  "Clorubite"  cement enamel were p l a c e d i n the f o u r concrete troughs and 2 3  Manufactured  by The Rustoleum C o r p o r a t i o n , Evanston,  Illinois.  Manufactured  by the General P a i n t Company, Vancouver, B. C.  FIGURE  I.  THE  7-5  1964  CM  TESTING  TANK  FIGURE 1.  The 1964 T e s t i n g Tank  LEGEND 1  T e s t i n g Tank  2  Door  3  Double-walled P a r t i t i o n  4  D r a i n Plug  5  Cooling Tank  6  "  "  water  inlet  7  Drain plug  8  Drawstring f o r opening doors  9  Door  10  Partition  11  Cooling Tank  12  Drainage Holes  13  Cooling Tank water  14  Spacer  inlet  9 f i l l e d w i t h s a l t water obtained from the Vancouver P u b l i c Aquarium.  About 1000 chum f r y were p l a c e d i n each tank.  The  f i s h were t o l e r a n t to the s a l t water, the s a l i n i t y of which ranged from 25 to 29°/oo. I n i t i a l m o r t a l i t y was h i g h i n both s a l t and f r e s h water. The populations of these f i s h were s t a b l e by the middle of June. Mortality i s s t i l l  low a t present (14 September).  An e s t i m a t i o n  of p o p u l a t i o n s i z e and the corresponding d e n s i t y i s given below: Tank F r e s h water S a l t water  Water.volume  Population  Density  202 l i t r e s  1500  7.4 f i s h / l i t r e  67 l i t r e s  250  3.7 f i s h / l i t r e  The l e s s e r d e n s i t y of the s a l t water f i s h i s accounted f o r by the l a c k of f l o w i n g water.  The s a l t water was always  s l i g h t l y eloudy a t the time the tanks were cleaned, i n c o n t r a s t to the f r e s h water tanks which were always c l e a r .  Dissolved  m a t e r i a l would l i m i t the oxygen c a r r y i n g c a p a c i t y of the s a l t water and thus the f i s h p o p u l a t i o n .  No p a t h o l o g i c a l  condition  was apparent i n e i t h e r the f r e s h water or s a l t water f i s h .  The  f i s h were f e d f r o z e n brine shrimp and otherwise r e c e i v e d standard aquarium c a r e .  ii)  T e s t i n g apparatus  A sketch of a t e s t i n g tank i s shown i n F i g u r e 1.  Four  such tanks were used, w i t h e i t h e r f r e s h water or s a l t water as d e s i r e d .  A l l f o u r were i d e n t i c a l ,  except t h a t the bottoms  of two tanks used f o r s a l t water were b l i s t e r e d i n p l a c e s ,  10 l e a v i n g a "pebbled" appearance.  Subsequent t e s t s i n d i c a t e d  t h a t t h i s c o n d i t i o n d i d not a f f e c t the r e s u l t s . water f l o w i n g through the tank, nor was was  There was  a i r bubbled i n .  no  Cooling  by an outer water-bath. Boors were slung between the s i x double w a l l s .  opened at the center and the outside edge of the alternately.  partition,  T h i s design prevented the constant-course  d e s c r i b e d by Hoar X.1956).  T h i s behaviour may  iments.  (1955) and as such was  L i g h t was  behind a  to  not d e s i r a b l e i n my  The doors could be opened by draw-strings,  remaining concealed  swimming  be more of a  " f o l l o w i n g " r e a c t i o n r a t h e r than s c h o o l i n g according Keenleyside  Each door  exper-  the  observer  screen.  provided by three v e r t i c a l 40 watt gas  tubes,  each 30 cm i n l e n g t h , which were placed at the end of the double w a l l s , a l t e r n a t e l y . D i f f i c u l t i e s i n c o n s t r u c t i o n prevented there being one tube per w a l l . enabled  the observer,  This arrangement of l i g h t s  l o o k i n g i n t o a m i r r o r at an angle of  45°  above the tank, to see the f i s h w e l l i l l u m i n a t e d without being d a z z l e d by r e f l e c t i o n from the water surface or having obscured by a c e n t r a l l i g h t .  his vision  His presence never d i s t u r b e d the  fish. Three t e s t s were run each day. i n the tank f o r a maximum of two  S i x f i s h would be  hours during the t e s t .  were then returned to the h o l d i n g tank.  The  They  The t e s t i n g tanks were  cleaned, drained and r e f i l l e d every n i g h t . during the n i g h t .  placed  They were aerated  f i s h were f e d i n the holding tanks a  h a l f hour before any were removed f o r t e s t i n g .  11 iii)  T e s t i n g technique  A f t e r one hour of a c c l i m a t i o n the doors were opened and the  number of f i s h i n each s e c t o r was recorded a t 20 second  i n t e r v a l s f o r a t e s t p e r i o d o f ten minutes. A f t e r the f i r s t two weeks of t e s t i n g the f i s h were not t e s t e d u n t i l t e n minutes a f t e r the doors were opened, since t h i s movement seemed to d i s t u r b the f i s h f o r one or two minutes. O c c a s i o n a l l y , a f i s h might become " e x c i t e d " by the opening of the doors and dash-round the tank, d i s t u r b i n g the o t h e r s . Such data were c o n s i d e r e d abnormal and are not i n c l u d e d .  This  event occurred r a r e l y , and g e n e r a l l y when a p a r t i c u l a r l y  small  f i s h was p l a c e d i n the tank.  The r a r i t y was due to the c a r e f u l  s e l e c t i o n of f i s h of the same s i z e f o r t e s t i n g .  "Pinheads" or  e x c e p t i o n a l l y l a r g e f i s h were not p l a c e d i n the t e s t i n g tanks a f t e r the nature of t h i s d i s t u r b a n c e was a p p r e c i a t e d . No morbid behaviour such as " b e l l y i n g - u p " , or the "panting" due to anoxia, was ever seen i n these experiments.  12 RESULTS The p r e l i m i n a r y experiments f a i l e d to r e v e a l any o r d e r l y d i f f e r e n c e s i n behaviour.  This seemed t o be due to poor exper-  imental design r a t h e r than to the v a r i a b i l i t y i n the experimental material. the  These observations were important as the b a s i s f o r  d e s i g n of the 1964 experiments.  As such, they w i l l be  d e s c r i b e d below.  A. In  P r e l i m i n a r y Experiments: 1963 Observations the s t i l l water experiments the f r y behaved d i f f e r e n t l y  i n each of the three tanks.  In the long tank the 40 f i s h swam  c o n s t a n t l y up and down on the f i r s t day, were l e s s a c t i v e and l e s s s t r o n g l y schooled on the second day. they were d i s p e r s e d through the tank. behaviour was f i r s t  By the t h i r d day  At t h i s time a g o n i s t i c  observed.  The 30 f r y i n one of the small a q u a r i a were moving cons t a n t l y round the tank i n n o n - p a r a l l e l f a s h i o n from the time they were f i r s t observed u n t i l they were removed f i v e days  later.  A g o n i s t i c behaviour was observed o c c a s i o n a l l y . In  the other aquarium the 3 f r y were g e n e r a l l y q u i e t .  Whatever a c t i v i t y occurred was a g o n i s t i c , with n i p p i n g and chasing most apparent. As a r e s u l t of these observations the long s t e e l tanks were s e t up f o r the r e s t of the summer's work, because  i t was  r e a l i z e d t h a t although the d e n s i t y of f i s h was an important f a c t o r to c o n s i d e r , i t could be c o n t r o l l e d e a s i l y .  Space on the  13 other hand should i n no way be l i m i t i n g to d e n s i t y e f f e c t s i n these  experiments.  The use of a center l i n e as a "counting gate" was not s u c c e s s f u l because there were occasions on which the f i s h were observed to be a c t i v e l y m i l l i n g a t e i t h e r one end of the tank or the other, but never swimming f a r enough up or down the tank i n order to cross the l i n e .  T h i s technique,  then, would not  provide an accurate measure o f a c t i v i t y . The hatchery-reared  chum f r y were observed to be more  a c t i v e i n swimming up and down the tank than were the w i l d coho f r y of the same y e a r . Mclnerney (1961).  T h i s phenomenon i s a l s o reported by  Coho were more evenly d i s p e r s e d i n the l a r g e r  groups (20 f i s h ) , while i n the smaller groups (5 f i s h ) was f r e q u e n t l y observed ( c f . Chapman 1962).  territorality  A g o n i s t i c behaviour  was r a r e r i n the small groups of chums, and t h e i r s c h o o l i n g i n t e n s i t y (closeness of i n t e r - f i s h d i s t a n c e ) was not as strong as i n the l a r g e r groups of these Feeding  fish.  seemed t o increase the a c t i v i t y of the f i s h .  T h i s was p a r t i c u l a r l y true of chums which had been without f o r 2 to 3 days p r e v i o u s l y . species with t h i s treatment.  Aggressiveness  food  i n c r e a s e d i n both  T h i s was p a r t i c u l a r l y true of  the small groups (5 f i s h ) of coho.  There the dominant f i s h  would remntain a t e r r i t o r y i n the area where the f r o z e n brine shrimp was tossed i n a t feeding  times.  Rocks of v a r i o u s s i z e s and c o n f i g u r a t i o n s d i d not r e l e a s e t e r r i t o r i a l behaviour i n e i t h e r s p e c i e s . t h a t the rocks would form the nucleus  ( I t had been hoped  of a t e r r i t o r y as shown  14 by K a l l e b e r g , 1958). Since no f u r t h e r comment w i l l be made on the p r e l i m i n a r y t e s t s , a summary of t h e i r i n f l u e n c e on the design of the 1964 experiments w i l l be u s e f u l . A c e r t a i n d e n s i t y of f i s h was seen to be necessary f o r the study of s c h o o l i n g i n t h i s experimental  situation.  The presence of a water c u r r e n t was not e s s e n t i a l to schooling. The  availability  of food could a f f e c t behaviour.  This  was an e f f e c t on the "mood" of the f i s h . A g o n i s t i c behaviour was most n o t i c e a b l e when the f i s h were of unequal s i z e s . groups of chums.  T h i s was p a r t i c u l a r l y true i n the small  Thus i t was considered d e s i r a b l e to p i c k f i s h  of the same s i z e i n f u t u r e experiments. Measurements of a g o n i s t i c behaviour were because of the number and spacing of the f i s h . of a c t i v i t y  was not accurate  inaccurate The measurement  by the "center gate"  Both these enumerations were omitted  technique.  from the 1964 t e s t s .  Because of these c o n s i d e r a t i o n s , the techniques d e s c r i b e d i n M a t e r i a l s and Methods were adopted.  f o r 1964  The f o l l o w i n g  p o i n t s were considered b a s i c to the study. M u l t i p l e s of 6 f i s h could be used i n any experiment, thus a l l o w i n g d e n s i t y to be c o n t r o l l e d .  (6 was found to be a s a t i s -  f a c t o r y number f o r the s i z e of f i s h t e s t e d ) . P i s h could be maintained i n separate  holding tanks,  thus  e l i m i n a t i n g the problems of the e f f e c t s of f e e d i n g f i s h i n an experimental  tank and having food matter i n the water —  as  TABLE I Gross t o t a l s f o r the 1964 t e s t s F i r s t group, 2 June to 25 June  No. o f tests 12 18 10 13 7 10 9 14  #  Tank and salinity A B C D  f .w. s.w. f.w. s.w. f.w. s.w. f .w. s.w.  Group f r e q . x gp. s i z e 4-6 1-3 1141 1720 975 1195 739 838 846 1441  Gps. 4-6 as $  1019 1520 825 1145 521 962 774 1079  47.2 46.9 45.8 48.9 41.3 53.4 47.7 42.8  1312 2414 1402 2001 1579 2642 2016 2713  28.0 55.9 32.5 50.5 31.3 63.9 40.0 60.2  Groups 4-6 as $ t o t a l f o r temp e r a t u r e s and photoperiods Temperatures high low  47.2$ 46.3$  Photoperiods long short  47.4$ 46.2$  Second group, 30 June to 31 J u l y 26 24 24 22 28 23 28 25  A B C D  f .w. s.w. f .w. s.w. f .w. s.w. f .w. s.w.  3368 1906 2918 . 1959 3461 1498 3024 1787  Temperatures high low  41.7$ 48.9$  Photoperiods long short  44.5$ 46.1$  one t e s t c o n s i s t s of t h i r t y observations over a ten minute p e r i o d . f o r d e t a i l s on tank treatments A,B,C and D see M a t e r i a l s and Methods, p.  16 discussed  previously.  Selection eliminate  of equal s i z e s of f i s h f o r t e s t i n g would  the d i s r u p t i n g  e f f e c t s found p r e v i o u s l y ,  subordinance e f f e c t s would be  B.  1964  i . e . dominance/  minimized.  Observations  These data f a l l i n t o two groups, d i f f e r e n t i a t e d by a s l i g h t change i n experimental method ( M a t e r i a l s p. 11).  T h i s change reduced the i n i t i a l  e f f e c t s of opening the  doors of the experimental tank, which produced for  one or two Totals  and Methods  "startle"  behaviour  minutes. of data f o r a l l the t e s t s are presented i n Table 1,  which shows the frequency of group-size m u l t i p l i e d by the s i z e of that p a r t i c u l a r group.  Thus the t o t a l s show the number of  f i s h p a r t i c i p a t i n g i n any one g r o u p - s i z e . are t o t a l l e d and presented as a c o n t r a s t 4-6,  the stronger aggregations.  presented as a percentage  T h i s 4-6  Groups of s i z e s  1-3  to the t o t a l s of s i z e s groups t o t a l i s a l s o  of the whole to i n d i c a t e  the trends  i n these gross data (from which the samples were taken  later).  The e f f e c t s of s a l t v s . f r e s h water can be judged from the r i g h t - h a n d column of the t a b l e . temperature of the  The percentages f o r the  and photoperiod e f f e c t s are shown beside each  part  table. Since the f i r s t group of t e s t s d i d not show any of the  differences (cf  expected between s a l t water and f r e s h water f i s h  Houston, 1959)  the technique was  second group of t e s t s .  changed to that of the  Only these l a t t e r data compare f a v o u r a b l y  TABLE I I Chi-Square values f o r each d i s t r i b u t i o n p a t t e r n i n the t e s t i n g  D i s t r i b u t i o n of f i s h i n the 6 s e c t o r s  , —  tank  ~ jC  Schooling tendency  000006  30  Strong  000015  20  000024  14  000033  12  000114  12  000123  8  000222  6  001113  6  001122  4  011112  2  111111  0  Weak  18 w i t h the gross e f f e c t s (Table I ) . An a n a l y s i s of v a r i a n c e has been performed second group, u s i n g a randomized blocks design.  on t h i s Only the .results  from one f r e s h water and one s a l t water t e s t i n g tank were used f o r the a n a l y s i s data.  These were s e l e c t e d randomly from the  two f r e s h water and two s a l t water tanks used i n each t r i a l . To o b t a i n a s i n g l e index of aggregation, the t e s t s were r e s c o r e d as f o l l o w s . Each of the t h i r t y d i s t r i b u t i o n s of f i s h i n the t e n minute t e s t was r e s c o r e d w i t h a chi-square value based on 1:1:1:1:1:1 as the h y p o t h e t i c a l d i s t r i b u t i o n f o r non-aggregated fish.  These chi-square values are given i n Table I I . Each  t e s t of t h i r t y chi-square values was summed and the r e s u l t i n g number was named the "aggregation index".  T h i s index provided  the raw data f o r the a n a l y s i s of v a r i a n c e and these are presented as Appendix A. I t was p o s s i b l e to use three r e p l i c a t i o n s of each h o l d i n g tank (treatment) w i t h i n each of f o u r time u n i t s ( b l o c k s ) .  The  blocks covered a p e r i o d of 4-5 days and t h e i r dates are as follows: Block No.  Date  1  4 - 9  July  2  16 - 20  "  3  21-24  "  4  27 - 31  "  Since the t o t a l p e r i o d was l e s s than one month, i t was not expected t h a t seasonal e f f e c t s would show up i n such a  /  TABLE I I I Temperature  Effects Blocks 2 | 3  1  Temperatures Totals  Tanks  Temperatures  A and B  9-12°C  5700  4182 1  4484  4628  18,994  C and D  7°C  5108  6818  4949  4578  21,453  10808  11000  . 9433  9206  40,447  4  Salinities Totals  Block t o t a l s  4  TABLE IV Salinity  E f f e c t s3 B l o c l es 2  1  3  Tanks  Salinities  A,B,C,D  freshwater  3448  4986  3757  4336  16,527  A,B,C,D  s a l t water  7360  6014  5676  4870  23,920  10808  11000  9433  9206  40,447  Block  totals  TABLE V Photoperiod  effects  1  B l o c l ts 2  Photoperiods  Tanks  8 hrs.  A and D B and C  16-17.5 h r s .  Block t o t a l s  Note?  3  4  Photoperiods Totals  5256  4919  4960  5310  20,445  5552  6081  4473  3896  20,002  10808  11000  9433  9206  40,447  data i s i n terms of the aggregation index (v. t e x t ) .  20  TABLE VI Analysis  of Variance f o r the 1 9 6 4 Data  (Model I, blocks as f i x e d e f f e c t s )  Source of e r r o r Temperatures  Sums of squares 62,986  Degrees of freedom  Mean square  calc.  1  62,986  6.91*  1  569,338  2,044  1  2,044  106,425  3  35,475  3.89*  T x S  12,101  1  12,101  1.33  T x P  1,087  1  1,087  T x B  250,277  3  83,426  S x P  3,186  1  3,186  S x B  277,699  3  92,566  P x B  151,084  3  50,361  10.16 5.53  T x S x P  25,299  1  25,299  2.78  T x S x B  9,384  3  3,128  Photoperiods Blocks  .05  **  569,338  Salinities  P  62.51 <1  <1  N  S  N S  N  S  9.16 4  <1  NS #*  N S  N  S  *  T x P x B  80,415  3  26,805  S x P x B  72,635  3  24,212  2.94 2.66  T x S x P x B  122,976  3  40,992  4.49  Residual  582,923  64  9,108  Total  2,329,859  95  N S  3.99 it II  P  .01  7.05 II  tt  2.75  4.11  3.99  7.05  II  II  2.75  4.11  3.99  7.05  2.75 ti  4.11  3.99  7.05  2.75 ti  4.11  ti  it  ti  it  II  it  21 r e l a t i v e l y short p e r i o d of time.  The r e c o r d of seasonal change  i n chum f r y behaviour recorded by Mclnerney change i n l e s s than one month.  (1961) shows l i t t l e  T h i s w i l l j u s t i f y the c o n s i d e r a -  t i o n of t i m e - u n i t s as b l o c k s i n t h i s a n a l y s i s i n s t e a d of assuming t h a t time i s a f o u r t h treatment. The t o t a l s f o r the d i f f e r e n t treatments are presented i n u n i t s of the aggregation index i n Tables I I I , IV and V (p. 19). A l l p o s s i b l e i n t e r a c t i o n s between the three d i f f e r e n t  treatments  and blocks were examined i n the a n a l y s i s of variance which i s presented i n TablesVI and V I I .  The R e p l i c a t e Tables and the  T o t a l of R e p l i c a t e s Table are presented i n Appendix B.  Tables  f o r the i n t e r a c t i o n analyses are r e a d i l y compiled from Appendix B, and are not i n c l u d e d here. Table VI shows the data t r e a t e d as a Model I a n a l y s i s . T h i s model assumes t h a t the b l o c k e f f e c t s are f i x e d , i . e . t h a t they are r e p r o d u c i b l e under the same c o n d i t i o n s of  sampling.  Here the P - t e s t uses the r e s i d u a l mean square as the denominator. Of the main e f f e c t s , the aggregation index i s s i g n i f i c a n t l y higher i n s a l t water, a t the 1$ l e v e l . higher a t the lower temperature a t the 5fo l e v e l . different.  The index i s s i g n i f i c a n t l y  than at the seasonal temperature  Photoperiod e f f e c t s are not  -  f  significantly  The main e f f e c t t o t a l s are presented i n Tables I I I ,  IV and V (p. 19). The  s i g n i f i c a n t b l o c k s e f f e c t i n d i c a t e s t h a t the  t i o n i n d i c e s summed over a l l three treatments d i f f e r among the f o u r b l o c k s . R e p l i c a t e s Table  aggrega-  significantly  The block t o t a l s shown i n the T o t a l of  (Appendix  B) would i n d i c a t e  this.  22  FIGURE 2 . FOR  TEMPERATURE  THE FOUR  EFFECTS  BLOCKS  7000  x  6000  UJ  Q Z  I  O SOOO  3  < IX)  4  o  <• 4 0 0 0  3000 HIGH TEMP.  LOW TEMP.  23  FIGURE FOR  3.  SALINITY  THE FOUR  EFFECTS BLOCKS  eooOi  7000  X Q z  60001  2 3  2 < o  soooi  <  4000  3000  1  FRESH WATER  SALT WATER  i  24  F I G U R E 4. FOR  THE  PHOTOPERIOD FOUR  EFFECTS  BLOCKS  7000  3000  1  SHORT DAYS  LONG DAYS  I  25 TABLE VII. A n a l y s i s of Variance f o r 1964 Data  Mixed Model Source of e r r o r  (Blocks as Random E f f e c t s )  Sums of squares  Degrees freedom  Mean squares  calc. <i  F  .05  P  .01  10.13  K  s  6.15  NS  it  S  tt  62,986  1  62,986  569,338  1  569,338  2,044  1  2,044  106,425  3  35,475  3.89  T x S  12,101  1  12,101  3.87  T x P  1,087  1  1,087  T x B  250,277  3  83,426  S x P  3,186  1  3,186  S x B  277,699  3  92,566  10.16  P x B  151,084  3  50,361  5.53  T x S x P  25,299  1  25,299  <1  N  S  10wl3  T x S x B  9,384  3  3,128  <1  N  S  2.75  T x P x B  80,415  3  26,805  2.94*  2.75  ti  72,635  3  24,212  2.66  2.75  it  T x S x P x B  122,976  3  40,992  4.49  Residual  582,923  64  9,108  2,329,859  95  Temperatures Salinities Photoperiods Blocks  S x P x B  Total  1.Pooled e r r o r M.S. = 45,927.  <1  <1  H  2.75 N  NS  S  9.16** <1  N  S  ** **  NS  4.11  10.13 tt  2.75  4.11  10.13 2.75  4.11  tt  it  tt  4.11  II  No change i n s i g n i f i c a n c e  Note: i n t h i s model the F - t e s t s are as f o l l o w s Mean square  M.S. Tested a g a i n s t  Main e f f e c t s  The main e f f e c t x blocks i n t e r action  Primary i n t e r a c t i o n s ( e x c l . blocks) Main e f f e c t s x blocks i n t e r actions Secondary i n t e r a c t i o n s ( e x c l . blocks Primary i n t e r a c t i o n s x blocks interactions Tertiary interaction  Primary  i n t e r a c t i o n s x blocks  Residual Secondary i n t e r a c t i o n s x blocks Residual Residual  26 Since the primary  i n t e r a c t i o n s between the  treatments  do not show any s i g n i f i c a n c e at the 5$ l e v e l , each  treatment  i s o p e r a t i n g independent of the others i n the a n a l y s i s . the treatments  a l l i n t e r a c t i n d i v i d u a l l y with b l o c k s .  would not be expected of the two  i f the blocks e f f e c t was  l e v e l s of the treatments  each b l o c k are presented  This  the same f o r each  involved.  of each main e f f e c t summed over the other two  However,  I n t e r a c t i o n graphs then p l o t t e d f o r  i n F i g u r e s 2, 3 and 4 (pp. 22-24).  Where  the t r e n d l i n e s are d i v e r g e n t an i n t e r a c t i o n i s i n d i c a t e d . a d d i t i o n , an approximation  of the average r e g r e s s i o n of the four  l i n e s by eye w i l l r e f l e c t the main e f f e c t . n o t i c e a b l e i n the photoperiod significant.  The  effect  This i s p a r t i c u l a r l y  (Figure 4) which i s not  average r e g r e s s i o n l i n e f o r the f o u r blocks  would have a slope approaching One  In  the h o r i z o n t a l .  other f a c t i s apparent from these f i g u r e s .  I t i s not  p o s s i b l e to p o i n t out one p a r t i c u l a r b l o c k as the cause of a l l the i n t e r a c t i o n s .  The  s i t u a t i o n i s d i f f e r e n t f o r each main  effect. The  three-way i n t e r a c t i o n s are only s i g n i f i c a n t i n one  i n s t a n c e , the T x P x B i n t e r a c t i o n . the extremely (v. F i g u r e 3 ) .  This i s p o s s i b l y due  to  l a r g e d i f f e r e n c e s i n the s a l i n i t y e f f e c t of Block I. The  s a l i n i t y v a r i a t i o n may  a l s o be r e s p o n s i b l e  f o r the s i g n i f i c a n c e of the four-way i n t e r a c t i o n . A Mixed-Model a n a l y s i s i s presented expected  i n Table V I I .  The  mean squares are not given, but can be deduced from  the i n f o r m a t i o n given w i t h t h i s t a b l e .  Here the b l o c k s are  considered to be random; t h a t i s subsequent t e s t i n g  should  27 TABLE V I I I P a r t i a l A n a l y s i s of Variance f o r the 1964 Data  Mixed model, c o n s i d e r i n g blocks 1-3 as random e f f e c t s Degrees of freedom  Mean squares  F  653,415  1  653,415  7.19  NS  18.51  60,874  2  30,437  2.01  NS  3.19  S x B  181,714  2  90,857  6.24**  Residual  699,085  48  14,564  2,125,630  71  Sums of squares  Source of e r r o r Salinities Blocks  Total  Note;  calc.  i n t h i s model the F - t e s t s are as follows -  Mean Square  Mean Square Tested  Against  Salinities  S x B interaction  Blocks  Residual  S x B  Residual  *.05  3.19  F  .01  5.08  28  FIGURE  5.  FRESH .  BLOCK  THE  SALT WATER  WATER FOR  TOTALS THE  IN  FOUR  TANKS  1200  800 X  Q  400  <  o  UJ  O <  -400  -800  1  I  2  3 BLOCK  4  MINUS EACH  HOLDING  29 provide a random sample of b l o c k e f f e c t s , not the same f o u r e f f e c t s as was assumed i n Model I , p r e v i o u s l y .  As the F - t e s t  i n d i c a t e s , the d i f f e r e n c e s between the temperature and s a l i n i t y treatments  i n the f o u r blocks do not show up s i g n i f i c a n t l y  as they d i d . f o r the Model I a n a l y s i s . F - t e s t s i s the same as b e f o r e .  The outcome of the other  Since the data i n the l a s t b l o c k  of the raw data t a b l e (v. Appendix A) showed some abnormality f o r the s a l i n i t y treatments  i n h o l d i n g tanks A and B, i t was  decided to r e t e s t the s a l i n i t i e s mean square f o r the f i r s t three blocks o n l y .  i n the mixed model  The a n a l y s i s o f variance i s  presented i n Table V I I I (p. 2 7 ) . No change i n s i g n i f i c a n c e was observed. As a second check, the data i n the mixed model were t e s t e d w i t h a pooled e r r o r term (Table V I I ) . in  Again, no change occurred  significance. F i n a l l y , F i g u r e 5 i s presented i n order to i l l u s t r a t e the  v a r i a b i l i t y among b l o c k s .  Two aspects are immediately  apparent;  the much g r e a t e r d i f f e r e n c e s between f r e s h and s a l t water aggregat i o n i n d i c e s i n the f i r s t block, and the h i g h v a r i a b i l i t y i n the fourth block. behaviour  T h i s v a r i a b i l i t y corresponded  of the f i s h from tanks A and B ( v . Appendix A) and thus  i n v o l v e d a l l three treatments. sidered.  w i t h some unusual  There are two p o i n t s to be con-  I f the data f o r the f i r s t b l o c k are a c c e p t a b l e , then  the lower d i f f e r e n c e s f o r the other three blocks might i n d i c a t e a c o n d i t i o n i n g e f f e c t on the f i s h .  On the other hand,  notes i n d i c a t e an u n u s u a l l y h i g h noise l e v e l  field  i n the b u i l d i n g ,  d u r i n g the f o u r t h b l o c k , which d i s t u r b e d the f i s h .  This d i s t u r b -  30 ance might have been r e s p o n s i b l e f o r the great v a r i a b i l i t y i n that block.  In t h a t case, the values shown i n F i g u r e 5 f o r the  f i r s t b l o c k could be considered abnormally  high, while the means  of the l a s t three blocks could a l l be s a i d to show the same block e f f e c t .  The decrease  i n d i f f e r e n c e between s a l t and  f r e s h water response from the f i r s t b l o c k to t h a t of the other three i s then e x p l a i n e d as a c o n d i t i o n i n g . e f f e c t .  With these  c o n s i d e r a t i o n s i n mind, i t i s proposed to assume t h a t the blocks e f f e c t s are f i x e d .  The Model I a n a l y s i s of variance i s t h e r e -  f o r e p r e f e r r e d to the Mixed Model. made on the assumption of t h i s  F u r t h e r d i s c u s s i o n w i l l be  interpretation.  31 DISCUSSION A.  The Experimental R e s u l t s  Compared With Those Of Some Other  Workers The  experimental data show the h i g h l y s i g n i f i c a n t e f f e c t  of a s a l t water environment i n i n c r e a s i n g the aggregation of chum salmon f r y .  There were a l s o d i f f e r e n c e s due  to temperature  (lower temperature c o r r e l a t i n g w i t h l a r g e r aggregations) which were l e s s extreme than the s a l i n i t y d i f f e r e n c e s .  The  temperature  e f f e c t i s more r e a d i l y acceptable since the r e s u l t s are summed over the two  types of tank, the large and  s a l i n i t y r e s u l t s , the  small ones.  In  the  s a l i n i t y e f f e c t i s confounded w i t h a  d i f f e r e n c e i n s p a t i a l c o n f i g u r a t i o n between the f r e s h water the  s a l t water h o l d i n g tanks.  This d i f f e r e n c e i n c o n f i g u r a t i o n  would c a s t some doubt on the s a l i n i t y e f f e c t by prompting following question:  i s the  found no and  tested?  As discussed  or the s i z e of  the  f u l l y below, Mclnerney (1963)  c o n d i t i o n i n g e f f e c t w i t h repeated t e s t s on coho f r y  Okuno (1963) found tank s i z e d i d not a f f e c t the  of f i s h e s w i t h " s t a b l e s c h o o l s " . t h a t the  the  s a l i n i t y e f f e c t r e a l or i s i t due  to the d i f f e r e n c e i n tank s i z e s or d e n s i t y , population  and  I t i s not  s a l i n i t i e s e f f e c t s are due  f r e s h / s a l t water d i f f e r e n c e s per One  behaviour  considered  likely  to anything other than  se.  of the disadvantages i n u s i n g the small tanks  was  t h a t f i s h would be re-sampled more f r e q u e n t l y than i n the more h e a v i l y populated l a r g e ones.  However, Mclnerney (1963) demonstra-  ted t h a t h i s s a l i n i t y preference phenomenon was  not an  artifact  32 due to re-sampling  ( i . e . conditioning).  In the present  exper-  iment, the f i s h were h e l d i n the t e s t i n g tanks f o r a p e r i o d of two hours once every 36; they were never f e d i n these  tanks  9  The p o s s i b i l i t y of c o n d i t i o n i n g i s considered to be u n l i k e l y . Secondly, Houston (1959) claimed t h a t the l o s s of the p r e v i o u s maximum swimming speed i n freshwater chums t r a n s f e r r e d i n t o s a l t water f o r a few hours was a s i t u a t i o n the f i s h would have to face a l l t h e i r l i f e i n such an osmotic The chums used i n the present experiment  environment.  were never  swimming  so r a p i d l y t h a t the aggregations broke up because of the i n a b i l i t y of the f i s h to keep t o g e t h e r .  In f a c t the s a l t water  f i s h were g e n e r a l l y more a c t i v e l y swimming round the tank were the f r e s h water f r y . it  than  In comparison w i t h Houston's f i n d i n g s ,  i s considered t h a t any impairment of the swimming a b i l i t y  i n the f i s h a c c l i m a t e d to s a l t water would not have been g r e a t enough to produce the observed d i f f e r e n c e s i n the aggregation index. The t h i r d problem i n i n t e r p r e t i n g the r e s u l t s of the s a l i n i t y treatment i s one of d e n s i t y and the r e s t r i c t i o n of movement.  Okuno (1963) r e p o r t e d t h a t some marine f i s h e s were  more aggressive when p l a c e d i n small tanks than they were i n the sea.  There was no tendency  f o r aggressiveness i n s t r o n g l y  schooled f i s h e s when p l a c e d i n the small tanks. r e a r e d f i s h i n these tanks. of s t r o n g l y schooled f i s h e s  Okuno a l s o  He found again t h a t the behaviour ("fishes forming s t a b l e  schools")  was not changed i n the smaller tanks; the f i s h which formed "unstable s c h o o l s " would become more aggressive i n smaller tanks  33 than they were i n a l a r g e one.  Most of the f i s h Okuno worked  with were l a r g e r than salmon f r y .  Since the tanks used i n t h i s  present experiment would be considered small by Okuno, i t i s not thought t h a t the s i z e d i f f e r e n c e i n the two tank would a f f e c t the behaviour C e r t a i n l y aggression was tank) f i s h i n my  types of h o l d i n g  of f r y i n the t e s t i n g  tanks.  not higher i n the s a l t water (smaller  experiment.  On the c o n t r a r y , the impression  was  t h a t the f r e s h water f i s h were more a g g r e s s i v e .  B.  The B i o l o g i c a l S i g n i f i c a n c e of the Experimental i)  Salinity  Results  effects  When diadromous f i s h are t r a n s f e r r e d between s a l t f r e s h water, any change i n behaviour w i t h changes i n p h y s i o l o g y .  would without  and  doubt c o r r e l a t e  In nature, changes i n physiology  would probably precede changes i n behaviour.  C o r r e l a t i o n s between  the m i g r a t i o n c y c l e s of salmon f r y and the a c t i v i t y of the t h y r o i d gland have been r e p o r t e d by Hoar and B e l l  (1950), Hoar  et a l (1952), Baggerman (1960) and E a l e s (1963b). Hoar (1953) p o i n t e d out t h a t e l e v a t e d temperatures  and  i n c r e a s e d t h y r o i d a c t i v i t y sometimes modified r e a c t i o n s to c u r r e n t and hastened downstream movement.  He a l s o s t a t e d  "Thyroid glands are normally quiescent i n s c h o o l i n g j u v e n i l e anadromous f i s h ... t h y r o i d hormone i s not normally i n v o l v e d i n any p a r t i c u l a r way d u r i n g seaward movement of these m i g r a t i n g s p e c i e s . However a prolonged stay i n f r e s h water produces an intense a c t i v i t y i n the t h y r o i d t i s s u e . There i s e v i d e n t l y an i n c r e a s e d demand f o r t h y r o i d hormone i n connexion with osmotic r e g u l a t i o n of a f i s h p h y s i o l o g i c a l l y prepared f o r sea water." (Hoar, 1953, p. 440).  34 Eales  (1963b) thought t h a t chum salmon had  i n a c t i v e t h y r o i d s at the m i g r a t i o n  period.  Activity in this  gland i n c r e a s e d when the f r y were a r t i f i c i a l l y f r e s h water.  relatively  retained i n  Baggerman (i960) a l s o found high t h y r o i d a c t i v i t y  i n f r y r e t a i n e d i n f r e s h water.  Eales  (1963a) suggested t h a t  such an i n c r e a s e d t h y r o i d a c t i v i t y might be brought about by the i n c r e a s e d metabolism of the f r y coupled w i t h the low  iodine  l e v e l of the f r e s h water. These f i n d i n g s must be borne i n mind when c o n s i d e r i n g s a l i n i t y e f f e c t on chum aggregation.  The  migratory behaviour but to what extent  i t does i s u n c e r t a i n .  There are two  s a l t water chum f r y .  f i r s t i s that the d i f f e r e n c e i s due r e t e n t i o n of the m i g r a t i n g  Eales  fish.  only to the  The  artificial  T h i s would suggest a patho-  to "osmotic s t r e s s " .  The  discussion  by  (1963a) would accept t h i s s t a t e , while Baggerman (i960)  i s contradictory.  This "osmotic s t r e s s " was  not high enough  to cause the premature death of the f i s h i n my not be considered The  study and  second i n t e r p r e t a t i o n i s i n e t h o l o g i c a l terms.  imbalance i n chum f r y , according i n increased thyroid a c t i v i t y . (i960) who  will  relevant.  i n c r e a s i n g photoperiod leads to g r e a t e r a c t i v i t y and  was  influence  ways of i n t e r p r e t i n g the d i f f e r e n c e s i n  aggregation between the f r e s h and  l o g i c a l c o n d i t i o n due  t h y r o i d may  the  would consider  to E a l e s  an  The  ionic  (1963a); t h i s r e s u l t s  T h i s i s c o n t r a d i c t o r y to Baggerman  that the photoperiod ( p i t u i t a r y ) e f f e c t  d i r e c t l y on the t h y r o i d .  E i t h e r the i o n i c imbalance of  35 E a l e s or the p i t u i t a r y e f f e c t of Baggerman i s to be the stimulus r e l e a s i n g a p p e t i t i v e behaviour. behaviour  considered  The a p p e t i t i v e  i s the i n c r e a s e d a c t i v i t y , or " m i g r a t i o n - d i s p o s i t i o n "  of Baggerman ( i 9 6 0 ) .  The manner i n which such i n c r e a s e d  a c t i v i t y r e s u l t s i n m i g r a t i o n i s not completely shown ( c . f . Hoar (1951), Neave (1955) and Hoar (1956) i n the I n t r o d u c t i o n ) . The  f i n a l r e s u l t i s the same, the entry i n t o s a l t water.  s a l t water e i t h e r the i n c r e a s e expected  i n thyroid  In  activity  ( c . f . E a l e s , 1963a), the more a v a i l a b l e i o d i n e ( c . f . Baggerman, I960) or some other f a c t o r a c t s to t r i g g e r the consummatory behaviour:  t h i s i s the strong aggregative behaviour  f r y i n s a l t water.  I f the change i n the osmotic  does t r i g g e r o f f a change i n behaviour,  of the  environment  i t c o u l d be  considered  a r e l e a s e r i n the L o r e n z i a n model of innate behaviour ( c . f . Tinbergen,  ii)  patterns  1951).  Temperature e f f e c t s  I f the temperature e f f e c t i s c o r r e l a t e d w i t h t h y r o i d a c t i v i t y i n m i g r a t i o n , i t can be a p p r e c i a t e d when the p e r i o d of m i g r a t i o n i s c o n s i d e r e d .  The  chum f r y move down i n t o c o o l  P a c i f i c waters before the temperature of the n a t a l streams i s anywhere near the summer maximum. probably more important  Temperature e f f e c t s are  as " s t r e s s " f a c t o r s than as d i r e c t i n g  f a c t o r s i n aggregative behaviour.  The  a l t e r n a t e way  of r e g a r d i n g  the temperature e f f e c t i s to agree t h a t i t i s s t a t i s t i c a l l y but to deny t h a t there i s any b i o l o g i c a l s i g n i f i c a n c e . argument cannot be decided because the temperatures  valid  This  chosen were  36 not widely enough separated.  iii)  Photoperiod  effects  I t i s s u r p r i s i n g t h a t there i s no photoperiod c o n s i d e r i n g the p o s i t i v e e f f e c t s found by Mclnerney Baggerman (i960) and E a l e s (1963a).  Mclnerney,  effect, (1963),  f o r example,  found t h a t the c y c l e of s a l i n i t y preference i n coho f r y was d i s p l a c e d by d i f f e r e n t photoperiods.  In experiments  with lake  chub (Gouesius plumbeus) Ahsan (1964) found t h a t photoperiod was not the dominant f a c t o r i n the c o n t r o l of the t e s t i c u l a r c y c l e , but r a t h e r t h a t temperature  was.  I t could be suggested t h a t since the m i g r a t i o n of chum salmon i s r e l a t i v e l y r a p i d , photoperiod might a c t as a t r i g g e r f o r the i n i t i a l migratory movement and l i t t l e  else.  Both Hoar  e t a l (1957) and McDonald (i960) considered t h a t changing  light  i n t e n s i t y was r e s p o n s i b l e f o r the movement of f i s h from the bottom o f the spawning streams a t n i g h t .  W r i t i n g somewhat  t e l e o l o g i c a l l y , I suggest t h a t there i s no reason to expect photoperiod to a f f e c t s c h o o l i n g when the more constant stimulus i s the s a l t water i n which the f r y are d e s t i n e d to l i v e .  37 CONCLUSIONS The  f o l l o w i n g p r i n c i p l e s can be d e r i v e d from t h i s  of aggregation  study  i n chum f r y .  F i r s t l y , there i s an innate tendency f o r the f r y to school i n s a l t water.  The stimulus, a p p e t i t i v e behaviour  summatory behaviour Secondly,  and con-  are d e s c r i b e d .  the r e t e n t i o n of chum f r y i n f r e s h water c o r r e l a t e s  with an abnormal aggressiveness  and a l e t h a l p e r i o d probably  o c c u r r i n g a t a time when the preadapted t h y r o i d and osmoregulatory systems were no longer s u i t e d to a f r e s h water environment. This aggressive behaviour  can be considered an a r t i f a c t since  i t occurred a f t e r the normal migratory p e r i o d and has not been observed  i n f i s h h e l d i n s a l t water.  T h i r d l y , the e f f e c t o f temperature suggests  t h a t these  f i s h would be i n t o l e r a n t towards the higher temperatures a t which the p a r t i a l l y - r e s i d e n t sockeye and coho l i v e . F o u r t h l y , the greater aggregation  found i n s a l t water  would be appropriate to a f i s h which i s found i n d e f i n i t e  schools  i n the ocean but whose downstream m i g r a t i o n i s probably of individual f i s h .  D i r e c t i n g f a c t o r s i n the stream  (especially  c u r r e n t ) might c o r r e l a t e with s c h o o l i n g i n nature but would be absent  from the t e s t i n g apparatus.  The r h e o t a c t i c f a c t o r would  not be operative i n the ocean. F i n a l l y , the b i o l o g i c a l advantage of s c h o o l i n g i n a s p e c i e s of anadromous f i s h d u r i n g i t s oceanic existence i s t h a t a mechanism e x i s t s to ensure the r e t u r n of the a d u l t p o p u l a t i o n to the n a t a l stream.  Given a normal d i s t r i b u t i o n of "homing a b i l i t y " i n the  38 s c h o o l , the homing success w i l l depend on the mean a b i l i t y of the whole migrant p o p u l a t i o n . stream was  I f the r e t u r n journey to the  l e f t to the e r r a t i c wanderings of each i n d i v i d u a l  some would be expected to home more a c c u r a t e l y than most. however, would be completely l o s t .  fish,  Others,  The advantages of s c h o o l i n g  i n these homing f i s h would seem to support the p h i l o s o p h i c a l p r o p o s i t i o n t h a t the whole i s g r e a t e r than the sum  of i t s p a r t s  ( c . f . Brock and R i f f e n b u r g h , I960). The  s i t u a t i o n i s e n t i r e l y d i f f e r e n t i n the spawning  Here there i s no disadvantage temperature  to not being schooled.  streams.  Increasing  and photoperiod t r i g g e r the m i g r a t i o n of these  fish  by causing them to swim out of the g r a v e l and i n t o the c u r r e n t . The  constant seaward flow of the r i v e r w i l l ensure t h a t the  m i g r a t i o n i s accomplished. In c o n c l u s i o n I would l i k e to p o i n t to two study which remain to be c l a r i f i e d .  aspects of t h i s  The f i r s t i s the q u e s t i o n  of s p a t i a l c o n f i g u r a t i o n . Is i t p o s s i b l e t h a t the behaviour the s a l t water f i s h was tanks?  a l t e r e d by t h e i r confinement  to the small  These t e s t s should be repeated w i t h the f i s h i n s i m i l a r  tanks i n order to prove c o n c l u s i v e l y the s a l i n i t i e s effect.  of  treatment  On the b a s i s of the present study i t i s claimed t h a t  the p o s i t i v e e f f e c t s of s a l i n i t y and temperature as i s the f a i l u r e of the photoperiod treatment The  are r e a l ,  just  to show s i g n i f i c a n c e .  l a s t p o i n t i s t h a t since seasonal d i f f e r e n c e s are  l i k e l y to occur, the experiment as young as p o s s i b l e .  The  an ontogenetic viewpoint  should be s t a r t e d w i t h the f r y  study could then be conducted  ( c . f . Shaw, I960, 1961).  from  T h i s would  39 provide a f u l l e r p i c t u r e of the schooling small f i s h . for  this  phenomenon i n these  The apparatus i s considered both u s e f u l and  purpose.  suitable  40 REFERENCES CITED Ahsan, S. N. 1964. The c o n t r o l of c y c l i c a l changes i n the t e s t i c u l a r a c t i v i t y of the lake chub Couesius plumbeus (Agassiz). Ph.D. t h e s i s , Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia. Baggerman, B. 1960. S a l i n i t y p r e f e r e n c e , t h y r o i d a c t i v i t y and the seaward m i g r a t i o n of four species of P a c i f i c salmon. J . F i s h . Res. Bd. Can., 17: 295-322. Brock, V. E . and R. H. R i f f e n b u r g h . 1960. F i s h a p o s s i b l e f a c t o r i n reducing p r e d a t i o n . 25: 307-317.  schooling, J . du C o n s e i l ,  Chapman, D. W. 1962. Aggressive behaviour i n j u v e n i l e coho salmon as a cause of e m i g r a t i o n . J . F i s h . Res. Bd. Can., 19: 1047-1080 E a l e s , J . G. 1963a. An a n a l y s i s of the t h y r o i d r o l e i n j u v e n i l e steelhead (Salmo g a i r d n e r i Richardson) and f a c t o r s r e s p o n s i b l e f o r i t s seasonal f l u c t u a t i o n i n a c t i v i t y . Ph.D. t h e s i s , Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia. 1963b. A comparative study of t h y r o i d f u n c t i o n i n migrant j u v e n i l e salmon. Can. J . Zool., 41: 811-824. Hoar, W. S. 1951. The behavior of chum, pink and coho salmon i n r e l a t i o n to t h e i r seaward m i g r a t i o n . J . F i s h . Res. Bd. Can., 8: 241-263. 1953. C o n t r o l Rev., 28: 437-452.  and timing  of f i s h m i g r a t i o n .  Biol.  1956. The behaviour of m i g r a t i n g p i n k and chum salmon f r y . J . F i s h . Res. Bd. Can., 13: 309-325. 1958. Rapid l e a r n i n g of a constant course by t r a v e l l i n g schools of j u v e n i l e P a c i f i c salmon. J . F i s h . Res. Bd. Can., 15: 251-274. and G. M. B e l l . 1950. The t h y r o i d gland i n r e l a t i o n to the seaward m i g r a t i o n of P a c i f i c salmon. Can. J . Res., D, 28: 126-136. D. MacKinnon and A. R e d l i c h . 1952. E f f e c t s of some hormones on the behaviour of salmon f r y . Can. J . Z o o l . , 30: 273-286. M. H. A. Keenleyside and R. G. G o o d a l l . 1957. Reactions of j u v e n i l e P a c i f i c salmon to l i g h t . J . F i s h . Res. Bd.  41 Can.,  14: 815-830.  Houston, A. H. 1959. Locomotor performance of chum salmon f r y (Oncorhynchus keta) during osmoregulatory a d a p t a t i o n to sea water. Can. J . Z o o l . , 37: 592-605. Kalleberg/', H. 1958. Observations i n a stream tank of t e r r i t o r a l i t y and competition i n j u v e n i l e salmon and t r o u t . Rept. I n s t . Freshwater Res., Drottningholm, (Sweden), 39: 55-98. Keenleyside, M. H. A. 1955. Some aspects of the s c h o o l i n g behaviour of f i s h . Behaviour, 8: 183-248. McDonald, J . 1960. The behaviour of P a c i f i c salmon f r y d u r i n g t h e i r downstream m i g r a t i o n to freshwater and s a l t water nursery areas. J . F i s h . Res. Bd. Can., 17: 655-676. Mclnerney, J . E. 1961. An experimental study of s a l i n i t y preference and r e l a t e d migratory behaviour of j u v e n i l e P a c i f i c salmon. M.Sc. t h e s i s , Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia. 1963. S a l i n i t y preference — an o r i e n t a t i o n mechanism i n salmon m i g r a t i o n . Ph.D. t h e s i s , Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia. Neave, F. 1955. Notes on the seaward m i g r a t i o n of p i n k and chum salmon f r y . J . F i s h . Res. Bd. Can., 12: 369-374. Okuno, R. 1963. Observations and d i s c u s s i o n s on the s o c i a l behaviour of marine f i s h e s . Pub. Seto. Mar. B i o l . Lab., 11: 281-336. Shaw, E.  1960. The development of s c h o o l i n g behaviour i n f i s h e s I . P h y s i o l . Z o o l . , 33: 79-86. 1961. The development of s c h o o l i n g behaviour i n f i s h e s I I . P h y s i o l . Z o o l . 34: 263-272.  Shelbourn, J . E . 1963. A d e s c r i p t i o n of s c h o o l i n g behaviour i n j u v e n i l e s of f o u r species of P a c i f i c salmon (Oncorhynchus w i t h p a r t i c u l a r r e f e r e n c e to the chum salmon (0. k e t a ) . B.Sc. graduating essay, Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia. Snedecor, G. ¥. 1959. S t a t i s t i c a l Methods. Press; Ames Iowa.  Iowa State C o l l e g e  Tinbergen, N. 1951. The Study of I n s t i n c t . Press; Oxford, U. K.  Oxford U n i v e r s i t y  42 APPENDIX A Raw Data f o r A n a l y s i s of Variance  Dates i n July  Block No.  Salinities  4 6 7 9 16 17 18 20 21 22 23 24  ©  rl  27 28 29 30 31 4 6 7 9 16 17 18 20 21 22 23 24 27 28 29 30 31  Holding tanks (P.p. and temp, A B C 444  278  372 196 298  298 298  142  318 274 264  232 292  372 408 264  218 312  278 294  512 366  372  400  480 608 508  rl  425 274 382  212  742 672 784  212 445 440  -p  01  624  528 312 542  664 266  622 522  334 162  614  386  152  204 306 554 740 563 156 296 250 240 354  542 666 482  treatments) D 224 400 294 370 388 624  416 250 290  466 274 530 546 564 766  782 628 826 600 454 346  640 466 494  492 538 548  348 498 280  U n i t s are i n terms of the aggregation index. LThese two data were missing but were c a l c u l a t e d  386 332 620  APPENDIX B Replicate  Tables  1st R e p l i c a t e  i/ocks  Treatments Tank  Salinity  1  2  A  f.w. s.w. f .w. s.w. f .w. s.w. f .w. s.w.  372 480 444 742 278 542 224 546  318* 425 232 212 306 782 370 640  B C D  Block T o t a l s  *  Treatments 3  4  Totals  372 528 218 664 563 600 416 492  278 334 512 334 250 348 466 386  1340 1767 1406 1952 1397 2272 1476 2064  3628  3285  3853  2908  13674  196 608 298 672 142 666 400 564  274 274 292 445 554 628 388 466  408 312 312 266 156 454 250 538  294 522 366 162 240 498 274 332  1172 1716 1268 1545 1092 2246 1312 1900  I 2nd R e p l i c a t e A B C D  f .w. s.w. f .w. s.w. f .w. s.w. f.w. s.w.  Block T o t a l s  3rd A B C D  3546  3321  2.696  2688  298 508 298 784 204 482 294 766  264 382 624 440 740 826 624 494  264 542 212 386 296 346 290 548  372 614 400 152 354 280 530 620  1198 2046 1534 1762 1594 1934 1738 2428  3634  4394  2884  3322  14234  12251  Replicate f.w. s.w. f.w. s.w. f.w. s.w. f.w. s.w.  Block Totals  M i s s i n g data v. Snedecor (1959), p. 312.  APPENDIX B (Continued) T o t a l of R e p l i c a t e s Table  Tank  Salinity  A  f .w. s.w. f .w. s.w. f .w. s.w. f .w. s.w.  B C D  Block t o t a l s  Treatments  Blocks  Treatments 1  2  3  4  Totals  866 1596 1044 2198 624 1690 918 1876  856 1081 1148 1097 1600 2236 1386 1600  1044 1382 742 1316 1015 1400 956 1578  944 1758 1278 648 844 1126 1270 1338  3710 5817 4208 5259 4083 6452 4526 6392  10808  11000  9433  9206  40447  45 APPENDIX C M o r t a l i t y of f r y i n the summer of 1963 These are the most accurate  and most o b j e c t i v e of the 1963  data* The  graph folio-wing shows the high m o r t a l i t y of the chum  f r y a t the end of September.  Coho f r y r e t a i n e d t h e i r p r e v i o u s l y  low m o r t a l i t y r a t e during t h i s p e r i o d .  These data are presented  because of t h e i r c l o s e agreement with Baggerman (I960). reported  Baggerman  t h a t her f i s h were healthy u n t i l June, when m o r t a l i t y  began to i n c r e a s e .  By November a l l her chum f r y were dead; her coho  were kept i n good c o n d i t i o n f o r two y e a r s .  In s a l i n i t y  preference  t e s t s both Baggerman and Mclnerney (1961) found t h a t chum f r y always p r e f e r r e d hypertonic discusses  sea water i n c o n t r a s t to f r e s h water.  the i n f l u e n c e of the t h y r o i d gland and "osmotic s t r e s s "  on s a l i n i t y preference, important.  Baggerman  concluding  t h a t the t h y r o i d e f f e c t i s more  The cause of death i n the chums was not e x p l a i n e d .  MORTALITY  O F FRY IN OF  I 9 63  THE  SUMMER  (GRAPH)  CHUM NO  FRY  INCREASE  MORTALITY JULY  IN  FROM  THROUGH  AUGUST  31  INITIAL POPULATION 1240 ±1  COHO NO  FRY  INCREASE  MORTALITY RECORD JANUARY  UNTIL  ENDED 1964  INITIAL POPULATION 9 0 0 11 I I 15  JUNE  JULY  IN  !5  IN  MORTALITY  OF  FRY IN THE  OF  1963  SUMMER  (GRAPH , C O N T I N U E D )  CHUM  FRY  t/i  ><  Q  O 70  u_  O  60  o <  UJ  > <  II  *  50  NO  INCREASE  MORTALITY  UNTIL  RECORD E N D E D JANUARY  1_1 I I  Li  r15 SEPTEMBER  i i i 11 i 1  ! 15  I OCTOBER  IN  19 6 4  IN  48 APPENDIX D References on Schooling Behaviour Taken from Shelbourn (1963) and  A l l e e , W. C. Press.  1931.  Animal Aggregations.  Elsewhere  U n i v e r s i t y of Chicago  A l l e e , HIT. C , and Bowen, E. 1932. Studies i n animal aggregations; mass p r o t e c t i o n a g a i n s t c o l l o i d a l s i l v e r among g o l d f i s h e s . J o u r l . Exp. Z o o l . 61: 185-207. A l v e r d e s , P. 1927. Social l i f e Hareout, Brace.  i n the animal world.  New  York;  Baerends, G. P., and Baerends van Roon, J . M. 1950. An i n t r o d u c t i o n to the s t u d i e s of c i c h l i d . f i s h e s . Behaviour. Supp. 1, 1-242. Breder, C. M. school.  1951. Studies on the s t r u c t u r e of the B u l l . Amer. Mus. Nat. H i s t . 98: 1-28.  fish  1959. Studies on s o c i a l groupings i n f i s h e s . B u l l . Amer. Mus. Nat. H i s t . 117: 397-481. Breder, C. M., and N i g r e l l i , R. P. 1935,. The i n f l u e n c e of temperature and other f a c t o r s on the winter aggregations of the s u n f i s h Lepomis a u r i t u s with c r i t i c a l remarks on the behaviour of f i s h e s . Ecology, 16: 33-47. C a r l , G. C , Clemens, W. A., and Lindsey, C. C. 1959. Fresh-water F i s h e s of B r i t i s h Columbia. British P r o v i n c i a l Museum Handbook No. 5, t h i r d e d i t i o n .  The Columbia 192 pp.  Clemens, W. A., and Wilby, G. V. 1961. Pishes of the P a c i f i c Coast of Canada. F i s h . Res. Bd. Can. B u l l . No. 68, second e d i t i o n , 443 pp. Deegener, P. 1918. Die formen der v e r g e s s e l s c h a f t u n g i n T i e r r e i c h . E i n s y s t e m a t i s c h - s o z i o l o g i s c h e r versuch. (Leipzig.) Hoar, W. S. 1954. The behaviour of j u v e n i l e p a c i f i c salmon w i t h p a r t i c u l a r reference to the sockeye (Oncorhynchus n e r k a ) . J . F i s h . Res. Bd. Can., 11: 69-97, 1958. The e v o l u t i o n of migratory behaviour among j u v e n i l e s of the genus Oncorhynchus. J . F i s h . Res. Bd. Can., 15: 391-428.  49 Loeb, J , 1918. Forced Movements. Tro-pisms. and Animal ( P h i l a d e l p h i a and London.)  Conduct.  McNaught, D. C. and H a s l e r , A. D. 1961. Surface s c h o o l i n g and. f e e d i n g i n the white bass (Roccus chrysops) i n Lake Mendota. Limnol. & Oceanog., 6: 53-60. Magnuson, J . J . 1961. A study w i t h p r e d a t i o n models. P o p u l a t i o n Dynamics, I n s t i t u t e of F i s h e r i e s , U. B. C. Vancouver, 135-153 ( l i m i t e d d i s t r i b u t i o n ) . Morrow, J . E. 1948. Schooling behaviour i n f i s h e s . B i o l . , 23: 27-48. Noble, G. K. 1938. 13: 133-158.  Sexual s e l e c t i o n among f i s h e s .  Quart. Rev. B i o l . Rev.,  P a r r , A. E. 1927. A c o n t r i b u t i o n t o the t h e o r e t i c a l a n a l y s i s of the s c h o o l i n g behaviour of f i s h e s . Occ. Pap. Bingham Oceanog. C o l l . , 1: 1-32. (New Haven, Conn.) Romanes, G. J . R.  1883.  Mental E v o l u t i o n i n Animals.  (London.)  S e t t e , 0. 1950. B i o l o g y of the A t l a n t i c mackerel (Scomber scombrus) of North America. P a r t I I - M i g r a t i o n s and h a b i t s . F i s h . B u l l . U. S. F. W. S. 51: 251-358. Welty, J . C. 1934. Experiments i n group behaviour of f i s h e s . P h y s i o l . Zool., 7: 85-128. Winn, H. E . 1958. Comparative r e p r o d u c t i v e behaviour and ecology of f o u r t e e n species of d a r t e r s ( P i s c e s - P e r c i d a e ) . E c o l . Monog. 28: 155-191.  

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