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Early life history and possible interaction of five inshore species of fish in Nicola Lake, British Columbia Miura, Taizo 1962

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E A R L Y L I F E HISTORY AND P O S S I B L E I N T E R A C T I O N .OF F I V E INSHORE S P E C I E S O F F I S H I N NICOLA L A K E ,  B R I T I S H COLUMBIA  by TAIZO MIURA B.S., The U n i v e r s i t y o f Kyoto, M.S., The U n i v e r s i t y o f Kyoto,  1953 1955  A T h e s i s Submitted i n P a r t i a l F u l f i l m e n t o f The Requirements f o r t h e Degree o f Doctor o f P h i l o s o p h y i n t h e Department of Zoology We a c c e p t t h i s t h e s i s as conforming t o t h e r e q u i r e d standard  THE  UNIVERSITY OF BRITISH COLUMBIA "•October,  1962  In presenting  t h i s thesis i n p a r t i a l f u l f i l m e n t of  the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available f o r reference and study.  I further agree that permission  f o r extensive copying of t h i s thesis f o r scholarly purposes may granted by the Head of my Department or by his  be  representatives.  It i s understood that copying or publication of t h i s thesis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission.  Department of The University of B r i t i s h Columbia, Vancouver 8, Canada. Date  QgJ&Jlx^  4 .  The University of B r i t i s h  Columbia  FACULTY OF GRADUATE STUDIES  PROGRAMME OF THE FINAL ORAL EXAMINATION FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  of  TAIZO MIURA B.Sc, Univeristy of Kyoto, Japan, 1953 M.Sc, Univeristy of Kyoto, Japan, 1955. PUBLICATIONS 1.  2.  MIURA, T. et a l . 1957. Preliminary report of f i s h production i n Lake Sagami, an impoundment. SUISAN ZOSHOKU 5 (2) : 13 - 28. MIURA, T. 1959. Some ecological studies on f i s h population in Lake Sagami, an impoundment, i n Kanagawa Prefecture, Japan. B u l l . Freshwater Fish. Res. Lab. 9 (1) : 2 3 - 3 9 .  TUESDAY, OCTOBER 2nd, 1962, AT 1:30 P.M. IN ROOM 3332, BIOLOGICAL SCIENCES BUILDING COMMITTEE IN CHARGE Chairman:  F.H. SOWARD  B.M. BARY D.C.G. MACKAY J.F. BENDELL G.G.E. SCUDDER P.A. LARKIN M.D.F. UDVARDY N.J. WILIMOVSKY External Examiner: R.C MILLER University of Saskatchewan  EARLY LIFE HISTORY AND POSSIBLE INTERACTION OF FIVE INSHORE SPECIES OF FISH IN NICOLA LAKE, BRITISH,COLUMBIA ABSTRACT Early l i f e history, d i s t r i b u t i o n , movement, food habits and i n t e r s p e c i f i c relations of five inshore species, largescale sucker (Catostomus macrocheilus), northern squawfish (Ptychocheilus oregonense), peamouth chub (Mylocheilus caurinum), redside shiner (Richardsonius balteatus), and p r i c k l y sculpin (Cottus asper), have been studied during the summers of 1959 1961 in Nicola Lake, B r i t i s h Columbia. Analyses were based on specimens p e r i o d i c a l l y sampled with three types of seine nets from various inshore waters of the lake, observation of behaviour of the f i s h both in nature and i n aquaria, and study of plankton, bottom animals and temperature conditions. After emerging, the fry of a l l species move to the head of the lake where there i s a tendency to form an early-summer aggregation. Later, they diverge from the head of the lake along the shore. Fry of a l l four cypriniform species showed similar diurnal movement. They started to move into the shallow water at dawn and moved out at dusk. In the sculpin, fluctuations in numbers near shore had no direct correlation with time of day. No species was • rigorously r e s t r i c t e d to one habitat, although different habitat preferences were observed. To a certain extent the species were separated by difference in d i s t r i b u t i o n i n r e l a t i o n to depth. These d i f ferences increase with age. A close association among fry of a l l species i n the early summer gradually dissipated. Divergence was also observed i n feeding habits of these species. In early summer they are t y p i c a l l y plankton feeders, but towards the end of summer their i n t e r s p e c i f i c feeding relations gradually become less because of the divergence i n food preference, feeding places and feeding manner. These changes are i n turn largely due to morphological changes, i n particular those of feeding structures.  Since the plankton resources seemed to be i n s u f f i c i e n t in the shallow-inshore area, there may have been competition for food i n early summer. Moreover, the f r y may have been forced into severe competition by an early-summer aggregation at the head of the lake as well as by s i m i l a r i t y i n behaviour and habitat. An alternative approach to the problem of demonstrating i n t e r s p e c i f i c relationships was made from comparison of species associations i n lakes of the Fraser River drainage. A positive correlation between the surface area and the number of species suggests that the larger the lake, the greater the p o s s i b i l i t y of coexistence between these species, and that comp e t i t i o n i n small lakes may be a factor i n eliminating some of the species. These findings are discussed i n r e l a t i o n to the current controversy concerning s p e c i a l i z a t i o n of temperate and t r o p i c a l freshwater fishes. It i s concluded that i n large complex environments freshwater fishes are afforded the opportunity for specialization, whereas i n small or simple environments, more generalized behaviour leads to competition between species. GRADUATE STUDIES F i e l d of Study:  Population biology in fishes  Quantitative Methods i n Zoology Fisheries Biology and Management Marine F i e l d Course ; Seminar i n F i s h e r i e s Biology  P.A. P.A. P.A.  Larkin Larkin Staff Larkin  Related Studies: Fisheries Hydraulics Fisheries Anthropology Introduction to B i o l o g i c a l Oceanography Marine Benthic Organisms and their Environment Marine Zooplankton  E.S. Pretious C. Belshaw R. Scagel R. Scagel B. Bary  ABSTRACT  E a r l y l i f e h i s t o r y , d i s t r i b u t i o n , movement, food h a b i t s and i n t e r s p e c i f i c r e l a t i o n s o f f i v e i n s h o r e s p e c i e s , l a r g e s c a l e sucker macrocheilus), northern  squawfish  (Catostomus  ( P t y c h o c h e i l u s oregonense), peamouth chub  ( M y l o c h e i l u s caurinum), red s i d e s h i n e r ( R i c h a r d s o n i u s b a l t e a t u s ) , and p r i c k l y s c u l p i n ( C o t t u s a s p e r ) , have been s t u d i e d d u r i n g t h e summers o f 1959 - 1961 i n N i c o l a Lake, B r i t i s h  Columbia.  Analyses  were based on  specimens p e r i o d i c a l l y sampled w i t h t h r e e types o f s e i n e n e t s from v a r i o u s i n s h o r e waters o f t h e l a k e , o b s e r v a t i o n o f b e h a v i o u r n a t u r e and i n a q u a r i a , and study o f p l a n k t o n ,  o f t h e f i s h both i n  bottom animals  and temperature  conditions. A f t e r emerging, t h e f r y o f a l l s p e c i e s move t o t h e head o f the l a k e where t h e r e i s a tendency t o form an early-summer a g g r e g a t i o n .  Later,  they  d i v e r g e from t h e head o f the l a k e a l o n g t h e shore. F r y o f a l l f o u r c y p r i n i f o r m s p e c i e s showed s i m i l a r d i u r n a l movement. They s t a r t e d t o move i n t o the shallow water a t dawn and moved out a t dusk. In t h e s c u l p i n , f l u c t u a t i o n s i n numbers near shore had no d i r e c t w i t h time o f a day. although the  No s p e c i e s was r i g o r o u s l y r e s t r i c t e d  d i f f e r e n t h a b i t a t p r e f e r e n c e s were observed.  correlation  t o one h a b i t a t ,  To a c e r t a i n  extent  s p e c i e s were separated by d i f f e r e n c e i n d i s t r i b u t i o n i n r e l a t i o n t o  depth.  These d i f f e r e n c e s i n c r e a s e with age.  A c l o s e a s s o c i a t i o n among f r y  o f a l l s p e c i e s i n t h e e a r l y summer g r a d u a l l y d i s s i p a t e d . Divergence was a l s o observed  i n f e e d i n g h a b i t s o f these  e a r l y summer they a r e t y p i c a l l y p l a n k t o n  species.  In  f e e d e r s , but towards the end o f  summer t h e i r i n t e r s p e c i f i c f e e d i n g r e l a t i o n s g r a d u a l l y become l e s s because  -iiiof the divergence in food preference, feeding places and feeding manner. These changes are in turn largely due to morphological changes, in particular those of feeding structures. Since the plankton resources seemed to be insufficient in the shallow inshore area, there may have been competition for food in early summer. Moreover, the fry may have been forced into severe competition by an earlysummer aggregation at the head of the lake as well as by similarity in behaviour and habitat. An alternative approach to the problem of demonstrating  interspecific  relationships was made from comparison of species associations in lakes of the Fraser River drainage.  A positive correlation between the surface area  and the number of species suggests that the larger the lake, the greater the possibility of coexistence between these species, and that competition in small lakes may be a factor in eliminating some of the species. These findings are discussed in relation to the current controversy concerning specialization of temperate and tropical freshwater fishes. i s concluded that in large complex environments freshwater fishes are afforded the opportunity for specialization, whereas in small or simple environments, more generalized behavior leads to competition between species.  It  A CKNOWLEDGMEN TS  The  a u t h o r wishes t o express  h i s g r a t i t u d e t o Dr. P. A. L a r k i n and D r .  C. C. L i n d s e y , who o f f e r e d v a l u a b l e a d v i c e and s t i m u l a t i o n throughout t h e study and d u r i n g t h e p r e p a r a t i o n o f t h e manuscript. Dr.  Thanks a r e a l s o due t o  J . R. Adams, Dr. J . F. B e n d e l l , Dr. G. G. F. Scudder and Dr. H.  Kasahara f o r a d v i c e and c r i t i c a l l y  r e a d i n g t h e manuscript,  Hamilton f o r c o r r e c t i n g E n g l i s h , t o Dr. T. G. Northcote Magnuson f o r a d v i c e i n f i e l d C. G i l l ,  and Dr. J . J .  work, and Mr. K. Ayyangar, Mr. G. E a l e s , Mr.  Mr. G. Hartman, Mr. K. Kutty, Mr. H. L o r z , Mr. J . MacLeod, Mr. E.  R i c k e r and Mr. T. Ueno f o r a s s i s t i n g w i t h f i e l d due  t o Mr. A. L.  work.  S p e c i a l thanks a r e  t o Mr. E. M a r t i n , f o r m e r l y Game Warden i n M e r r i t t , f o r a s s i s t a n c e . The  author  i s g r a t e f u l t o the. B r i t i s h Columbia Game Commission f o r t h e  o p p o r t u n i t y o f u s i n g the data  c o l l e c t e d by the F i s h e r i e s Research  Division.  TABLE OF CONTENTS Page I.  INTRODUCTION  3  II.  GENERAL DESCRIPTION OF  THE;LAKE  (1)  l o c a t i o n and Morphometry  (2)  P h y s i c a l and  (3)  Fauna and  . . . . . . . . . .  3  . . . . . . .  4 5  F l o r a o f the Lake  5  (a)  Plankton . . . . .  . . . .  (b)  Bottom fauna  (c)  Vegetation  ....ooe..  (d)  F i s h fauna  . . . . . . . . . . 0 0 . « » « . . o o  5  . . . . . . . . . . . . . . . .  B  . . . . . . . .  METHODS  . . . . . . .  MATERIAL AND  IV.  ENVIRONMENTAL CONDITIONS OF INSHORE WATER  (2)  3  Chemical C o n d i t i o n s  III.  (1)  . . . . . . .  .  0  .  0  .  0  .  .  5  .  t  0  .  0  5  0  . . . . . . . . . . .  12  Iirnnological Conditions (a')  Physical  (b)  Bottom type  12  conditions  12  . . . . . . . . . . . . . . . . . . .  12  Plankton  1Z  (  l  V.  (3)  Bottom  (4)  O t h e r F i s h S p e c i e s and O l d e r F i s h  (5)  T e r r e s t r i a l Insects  Fauna  .  (l)  20 . . . . . . . . . . .  MORPHOLOGICAL DESCRIPTION OF LARVAE AND Morphlogical Description  YOUNG  22 23  . . . . . . . . .  18  24  (a)  Largescale sucker  24  (b)  Northern squawfish  26  (c)  Peamouth chub  26  (d)  Redside s h i n e r  30  (e)  Prickly sculpin  30  -V(2)  VI.  (a)  Key t o p o s t l a r v a l f i s h e s o f N i c o l a Lake  (b)  Key t o j u v e n i l e f i s h e s o f N i c o l a Lake  . . . .  DISTRIBUTION AND MOVEMENT (1)  (2)  Spawning and F i r s t Appearence o f F r y on t h e Inshore Area  32 33 35 35  (a)  Largescale sucker  35  (b)  N o r t h e r n squawfish  36  (c)  Peamouth  (d)  Redside  (e)  Prickly sculpin  chub  36  shiner  37  S e a s o n a l Movement r  VII.  32  ,Keys t o P o s t l a r v a l and Young F i s h e s  38 38  (a)  L a r g e s c a l e sucker  38  (b)  Northern squawfish  40  (c)  Peamouth  40  (d)  Redside s h i n e r  40  (e)  Prickly sculpin  44  (f)  Summary o f s e a s o n a l movement  44  chub  (3)  D i u r n a l Movement and D i s t r i b u t i o n i n Inshore Water . .  46  (4)  Vertical Distribution  56  (a)  Field  observation  (b)  Aquarium o b s e r v a t i o n  (5)  Habitat Preference  (6)  Interspecific Association  FOOD HABITS (l)  56 57 60 62 6?  Development o f S t r u c t u r e s R e l a t e d with Feeding . . . .  67  (a)  Largescale sucker  67  (by  N o r t h e r n squawfish  71  -vi(c)  Peamouth chub  74  (d)  lied side shiner  77  (e)  P r i c k l y sculpin  80  (2)  I n t e r s p e c i f i c Overlapping of Stomach Contents  . . . .  (3.)  Relation between Stomach Contents and Net-plankton . .  89  (/+)  Diurnal Rhythm of Feeding A c t i v i t y  90  VIII. GEOGRAPHIC EVIDENCE  83  99  IX.  INTERSPECIFIC COMPETITION  103  X.  DISCUSSION  105  (1)  105  (2)  (3)  Characteristics of Freshwater Fishes and Environments (a)  Characteristics of freshwater environments  (b)  Characteristics of freshwater fishes  . . .  105 106  I n t e r s p e c i f i c Relationships  Ill  (a)  Competition f o r space  112  (b)  Competition f o r food  113  (c)  Factors minimizing competition f o r food  I n t e r s p e c i f i c Competition and Co-existence  . . . .  113 119  XI.  SUMMARY  126  XII.  LITERATURE CITED  129  FIGURES Page F i g u r e 1.  N i c o l a Lake, showing s e i n e s t a t i o n s .  F i g u r e 2.  T y p i c a l t h e r m a l c o n d i t i o n and change i n the i n s h o r e water.  . .  i t s diurnal  ( J u l y 12 -  13,  I960)  F i g u r e 3»  Largescale  sucker  13  F i g u r e 4.  N o r t h e r n squawfish f r y .  F i g u r e 5-  V e n t r a l view o f a n t e r i o r p a r t o f n o r t h e r n squawfish ( A ) , peamouth chub (B) and r e d s i d e s h i n e r ( C ) . D o r s a l view o f head o f peamouth chub (D) and morthern squawfish  25  fry. . :  .  (E)  F i g u r e 6.  Peamouth chub f r y .  F i g u r e 7.  Feed s i d e s h i n e r f r y (A, .3) and s c u l p i n f r y (C, D).  F i g u r e 8.  F i g u r e 9.  F i g u r e 10.  F i g u r e 11.  F i g u r e 12.  27  28 .  29  prickly 31  Percentage o f c a t c h o f l a r g d s c a l e sucker f r y a t 9 s t a t i o n s as i n d i c a t e d by b i w e e k l y seine hauls.  39  Percentage o f c a t c h o f n o r t h e r n squawfish f r y a t 9 s t a t i o n s as i n d i c a t e d by b i w e e k l y ha,uls. • '  41  Percentage o f c a t c h o f peamouth chub f r y a t 9 s t a t i o n s as i n d i c a t e d by b i w e e k l y seine hauls.  42  Percentage o f c a t c h o f r e d s i d e s h i n e r f r y a t 9 s t a t i o n s as i n d i c a t e d by biweekly seine hauls.  . . . . .  Percentage o f c a t c h o f p r i c k l y s c u l p i n f r y a t 9 s t a t i o n s as i n d i c a t e d by b i w e e k l y seine hauls.  F i g u r e 13.  Diagrams showing i n t e r s p e c i f i c a s s o c i a t i o n .  F i g u r e 14.  M o r p h o l o g i c a l development o f l a r g e s c a l e sucker f r y . A. , L a t e r a l view o f head. B. F r o n t a l view o f body. C. First g i l l . D. Pharyngeal t e e t h . . . . . .  !  9  43  45 . . . . .  64  68  -viiiFigure 15. .Morphological development of northern squawfish f r y . A. L a t e r a l view of head. B. Frontal view o f body. G. F i r s t g i l l . D. Pharyngeal teeth. .. Figure 16.  Morphological development of peamouth chub f r y . A. L a t e r a l view of head. B. Frontal view of body. C. F i r s t g i l l . D. Pharyngeal teeth. '.  Figure 17.  Morphological development o f redside shiner f r y . A. L a t e r a l view of head. B. Frontal Vjiew of body. G. F i r s t g i l l . D. Pharyngeal teeth.  Figure 18. Morphological development of p r i c k l y sculpin f r y . A. L a t e r a l view o f head. B. Frontal view o f body. C. F i r s t g i l l . D. Upper pharyngeal teeth. E. Lower pharyngeal teeth. F. M a x i l l a , jugar and vomer teeth. Figure 19.  Diagrams showing i n t e r s p e c i f i c overlapping of stomach contents.  Figure 20.  D i e l f l u c t u a t i o n of number o f animals i n the stomachs o f sucker f r y . Any two means not enclosed by the same bracket are d i f ferent (P_.__0.05). Blank: Planktonic animals. Shaded: Benthic animals.  Figure 2 1 .  D i e l f l u c t u a t i o n o f number of animals i n the stomachs of squawfish f r y . Any two means not enclosed by the same bracket are different (P^.0.05). Blank: Planktonic animals. Shaded: Benthic animals. Lined: T e r r e s t r i a l i n s e c t s . . . . . .  Figure 2 2 .  D i e l f l u c t u a t i o n of number of animals i n the stomachs of peamouth chub f r y . Any two means not enclosed by the same bracket are different (P.40.05). Blank: Planktonic animals. Shaded: Benthic animals. Lined: T e r r e s t r i a l i n s e c t s .  Figure 23- D i e l f l u c t u a t i o n of number of animals i n the stomachs of redside shiner f r y . Any two means not enclosed by the same bracket are d i f f e r e n t ( P ^ . 0 . 0 5 ) . Blank: Planktonic animals. Shaded: Benthic animals. Lined: T e r r e s t r i a l i n s e c t s .  -ixF i g u r e 24 •  F i g u r e 25.  D i e l f l u c t u a t i o n o f number o f a n i m a l s i n the stomachs o f p r i c k l y s c u l p i n f r y . Any two means not e n c l o s e d by the same b r a c k e t are d i f f e r e n t ( P ^ 0 . 0 5 ) . Blank: Planktonic animals. Shaded: B e n t h i c a n i m a l s . Lined: Terrestrial insects. C o r r e l a t i o n between t h e s u r f a c e area ( l o g a r i t h m i c s c a l e ) and the number o f species i n selected lakes o f the Fraser River drainage.  95  101  TABLES Page Table 1.  S p e c i e s compostion o f N i c o l a Lake p l a n k t o n .  Table 2.  D i e l changes o f p l a n k t o n i n t h e i n s h o r e w a t e r . Each number i n d i c a t e s t h e t o t a l o f 6 h a u l s a t Station' N  15  Bottom fauna o f t h e i n s h o r e a r e a a t S t a t i o n N. Each number i n d i c a t e s t h e t o t a l o f s i x replicates.  19  T o t a l c a t c h e s by weekly s e i n i n g a t 5 s t a t i o n s i n t h e n o r t h e a s t e r n b a s i n , 1959. Youngs o f the year a r e excluded  21  Catch d a t a o f s u c k e r f r y s e i n e d Each number i n d i c a t e s t h e t o t a l r e p l i c a t e s i n t h e e a r l y and mid mean o f t h r e e r e p l i c a t e s i n t h e  a t S t a t i o n N. o f two summer, and l a t e summer.  47  Catch d a t a o f s q u a w f i s h f r y s e i n e d a t S t a t i o n N. Each number i n d i c a t e s the t o t a l o f two r e p l i c a t e s i n t h e e a r l y and mid summer, and t h e mean o f t h r e e r e p l i c a t e s i n t h e l a t e summer."  49  Catch d a t a o f chub f r y s e i n e d a t S t a t i o n N. Each number i n d i c a t e s t h e t o t a l o f two r e p l i c a t e s i n t h e e a r l y and mid summer, and mean o f t h r e e r e p l i c a t e s i n t h e l a t e summer.  50  Catch d a t a o f s h i n e r f r y s e i n e d a t S t a t i o n N. Each number i n d i c a t e s t h e t o t a l o f two r e p l i c a t e s i n e a r l y and mid summer, and mean o f t h r e e r e p l i c a t e s i n t h e l a t e summer.  51  Catch d a t a o f s c u l p i n f r y s e i n e d a t S t a t i o n N. Each number i n d i c a t e s t h e t o t a l o f two r e p l i c a t e s i n t h e e a r l y and mid summer, and mean o f t h r e e r e l p i c a t e s i n t h e l a t e summer.  53  Table 10. Catch data o f f r y . o f t h e f i v e s p e c i e s s e i n e d at t h r e e d i f f e r e n t bottom t y p e s by day and by n i g h t .  55  Table 11. P e r c e n t a g e o f v e r t i c a l d i s t r i b u t i o n o f f r y o f the f i v e s p e c i e s i n a q u a r i a a t t h r e e d i f f e r e n t l i g h t conditions.  58  Table 3-  T a b l e 4-  Table 5-  T a b l e 6.  Table 7.  T a b l e 8.  ,Table 9.  6  -xiTable 12.  Average catches of f r y o f the f i v e species at three d i f f e r e n t habitats. Each mean i s based on 6 seine hauls.  61  -Table 13.  Values o f rank correlation c o e f f i c i e n t , i n d i c a t i n g i n t e r s p e c i f i c association.  Table 14.  Stomach contents of four d i f f e r e n t size groups of sucker f r y . Numbers of i n d i v i d uals o f each item are given as percentage o f t o t a l i n d i v i d u a l s i n a l l stomachs of given  Table 15.  Table 16.  Table 1 ? .  Table 18.  Table 19.  Table 20.  . ..  63  70  Stomach contents o f three d i f f e r e n t size groups o f squawfish f r y . Numbers o f individuals of each item are given as percentage of t o t a l individuals i n a l l stomachs of given size range. . . ..  73  Stomach contents of three different size groups of peamouth chub f r y . Numbers of individuals of each item are given as percentage o f t o t a l i n d i v i d u a l s i n a l l stomachs of given size range. . . ..  76  Stomach contents of three d i f f e r e n t size groups o f redside shiner f r y . Numbers o f i n d i v i d u a l s o f each item are given as percentage o f t o t a l i n d i v i d u a l s i n a l l stomachs o f given size range. . . . ..  79  Stomach contents of three d i f f e r e n t size groups of p r i c k l y sculpin f r y . Numbers o f i n d i v i d u a l s of each item are given as percentage of t o t a l i n d i v i d u a l s i n a l l stomachs of given size range.  82  Percent occurence of stomach contents o f f r y of f i v e species i n the three d i f f e r e n t seasons. Numbers p f i n d i v i d u a l s of each item are given as percentage of t o t a l i n d i v i d u a l s i n a l l stomachs of f r y i n d i f f e r e n t seasons.  84  Values of rank correlation c o e f f i c i e n t , i n d i c a t i n g i n t e r s p e c i f i c overlapping o f stomach contents. '.  87  Appendix Table. Surface areas and number of species of Catostomidae, Cyprinidae and Cottidae of 36 lakes of the Fraser River Drainage. . ..  133  I.  INTRODUCTION  It has been shown in both marine and freshwater fisheries that catch is influenced by year class strength, and i t has been generally assumed that the numerical strength of an individual year class i s determined during the f i r s t growing season.  If there are several species present in a  lake and i f there i s similarity in their f i r s t summer's l i f e , interspecific competition may be an important factor i n determining year class strength. In freshwater fishes, i n general, similarity i n their f i r s t summer's l i f e may be commonly observed even though the adults show major differences in habitat preference or in food habits.  Between species, divergence i n  mode of l i f e with growth may reflect reduction i n competition. To investigate these possibilities Nicola Lake was chosen as a working site, because i t provides a wide variety of fish species, and five inshore species, largescale sucker (Catostomus macrocheilus), northern squawfish (Ptychocheilus oregonense), peamouth chub (Mylocheilus  caurinum)redside  shiner (Richardsonius balteatus), and prickly sculpin (Cottus asper), form a close association i n the shallow inshore area in their f i r s t summer's l i f e ( A l i , 1959). In spite of the common occurrence and wide distribution of these inshore species, l i t t l e i s known of their f i r s t summer ecology and there i s no description of the larvae. This thesis presents, i n the f i r s t place, morphological descriptions of the larvae and their general ecology (appearence, distribution, seasonal movement, habitat preference, and food habits).  Secondly, by comparison of  the ecological role of each speoies, interspecific relationships are  -2-  analyzed.  Thirdly, the significance of i n t e r s p e c i f i c competition i n fresh-  water habitats i s evaluated as a factor c o n t r o l l i n g f i s h populations and coexistence between species.  Nicola  II.  GENERAL DESCRIPTION OF  (l)  L o c a t i o n and  Lake l i e s a p p r o x i m a t e l y  THE  LAKE  Morphometry.  45  miles  southwest o f Kamloops, i n the  Southern I n t e r i o r P l a t e a u o f B r i t i s h Columbia, a t 50°N l a t i t u d e and l o n g i t u d e a t an a l t i t u d e o f The  2,056  l a k e , l o c a t e d i n the a r e a  feet. known as the N i c o l a B a s i n , i s p a r t o f  the P r i n c e t o n - N i c o l a - K a m l o o p s Depressions t h i s and o t h e r b a s i n s , d e s c r i b e d  120°W  ( B r i n k and  (1944),  by Mathews  Farsted,  1949).  In  s e r i e s o f l a k e s were  formed i n l a t e P l e i s t o c e n e as m e l t i n g i c e s u c c e s s i v e l y dammed narrow b a s i n outlets.  The  p r e s e n t N i c o l a Lake i s the r e s i d u e o f t h r e e l a r g e r l a k e s  which i n sequence, p r e v i o u s l y o c c u p i e d  the same b a s i n .  The whole Southern I n t e r i o r P l a t e a u , of which the N i c o l a V a l l e y i s a p a r t , has a low a n n u a l p r e c i p i t a t i o n maximum and  a July-August  (15-20  minimum (Chapman,  i n c h e s ) w i t h a marked December  1952).  The  area i s a l s o noted  f o r i t s extreme temperature v a r i a t i o n . The  l a k e i s about 14 m i l e s l o n g and  mile i n width.  The  o f s h o r e l i n e 27.8 f e e t and  77  6,041  feet.  The  volume i s  a c r e s , the  length  the maximum depth  45,900  and  181  the volume  1.27.  l a k e has  f o u r main i n l e t  f l o w throughout the y e a r . the  i s approximately  m i l e s , the shore development 2.5,  the mean depth  development The  s u r f a c e area  i s i n most p l a c e s not more than 1  s p r i n g and  Glimpse Lake and  summers,  A number o f s m a l l streams run i n t e r - m i t t e n t l y i n  e a r l y summer ( L o r z ,  on the e a s t e r n shore,  streams which, except on v e r y dry  1962).  N i c o l a R i v e r , e n t e r i n g the  i s the main t r i b u t a r y , and  v a l l e y s t o the e a s t .  lake  d r a i n s Douglas Lake,  Moore Creek, e n t e r i n g the l a k e  on  the n o r t h - e a s t e r n  shore,  d r a i n s Frogmore Lake i n the v a l l e y t o t h e north-  Stump Lake Creek a l s o e n t e r s the n o r t h e a s t e r n  end o f the l a k e about a  hundred y a r d s  Creek, e n t e r i n g on the south-  e a s t o f Moore Creek.  e a s t e r n shore, the creek  Quilchena  d r a i n s v a l l e y s t o the south.  d r i e s up o c c a s i o n a l l y d u r i n g  The flow i s r a t h e r s m a l l and  summer.  There i s o n l y one o u t l e t , t h e N i c o l a R i v e r , which has a s i x f o o t h i g h irrigation westerly  c o n t r o l dam a t i t s e x i t from t h e l a k e .  j o i n i n g theTJi'ompson R i v e r a t Spences  (2) The summer.  P h y s i c a l and Chemical  Lorz  (1962)  Bridge.  Conditions.  r e p o r t s the f o l l o w i n g :  depth o f t h e t h e r m o c l i n e  The l a k e shows t h e r m a l  f o r long periods during  one  The t h e r m o c l i n e  strat-  summer.  (area o f r a p i d temperature change) may  t u a t e e x t e n s i v e l y and r a p i d l y under the i n f l u e n c e o f s t r o n g winds.  south-  s u r f a c e temperature o f o f f s h o r e water seldom r i s e s t o 20°C i n  i f i c a t i o n but i s n e v e r s h a r p l y s t r a t i f i e d The  The r i v e r flov>s  fluc-  southeasterly  f l u c t u a t e d between 20 f e e t deep and 65 f e e t d u r i n g  33 hour p e r i o d . Rawson  (1934)  r e p o r t s t h a t the l a k e was stagnant  summer when the bottom oxygen was  0.4  p.p.m.  Lorz  oxygen c o n c e n t r a t i o n a t 50 f e e t ranged from 8-10 o f 1959.  a t the bottom i n t h e  (1962)  reports that  p.p.m. d u r i n g the summer  and t h a t a t no time d u r i n g the study was severe oxygen d e p l e t i o n  noted i n t h e lower s t r a t a . Secchi d i s c readings of The  1959,  although  o f 5 - 7 f e e t were recorded  i n the s p r i n g o f  I960  low summer r e a d i n g s were probably  algae  (Lorz, The  readings o f  throughout the summer  12 f e e t  were  obtained.  due to a heavy bloom o f b l u e - g r e e n  1962).  t o t a l d i s s o l v e d s o l i d s content  o f N i c o l a Lake ranged from 170 p.p.  -5m.  i n s p r i n g to  235  p.p.m. i n autumn ( L o r z ,  (3) (a)  Lorz  animal (b)  F l o r a of the Lake.  Plankton The  and  Fauna and  1962).  s p e c i e s composition  (1962).  1  Table  s p e c i e s observed  Bottom  fauna  Rawson  (1934)  o f chironomid  o f the plankton was  r e p o r t e d by Rawson  shows the s p e c i e s composition  from i n s h o r e water by the  (1934)  i n c l u d i n g the  author.  found a v e r y s c a n t y bottom fauna  i n deep water, composed  l a r v a e , P i s i d i u m , O l i g o c h a e t a and Nematoda.  Bottom samples  were taken from the i n s h o r e area o f the n o r t h e a s t e r n end o f t h e l a k e w i t h 6-inch Ekman dredge.  The bottom fauna  r i c h i n both q u a l i t y and Rawson, chironomid  quantity.  pupae, mayfly  from the i n s h o r e area was  In a d d i t i o n to the a n i m a l s r e p o r t e d  (c)  by  larvae, stonefly larvae, caddisfly larvae,  phantom midge l a r v a e , amphipods, l e e c h e s , s n a i l s and ceans such as A l o n a ,  rather  some b e n t h i c c r u s t a -  Chydorus, o s t r a c o d s and h a r p a c t i d s were  observed.  Vegetation A q u a t i c v e g e t a t i o n i s g e n e r a l l y sparse except i n t h e shallow southwest  b a s i n , the shores o f the n o r t h e a s t b a s i n and t h e bays o f the e a s t e r n edge o f the l a k e .  Ali  (1959)  i n the shallow a r e a s . the bays and  reports:  Na.jas sp., Chara sp. and  A l o n g the e a s t and  back waters,  S c i r p u s sp. and  southeastern  Callitriche  sp.  shore, e s p e c i a l l y i n  Typha sp. a r e abundant.  In the  south-west b a s i n the dominant s p e c i e s a r e Potomageton sp., Z a n n i c h e l l i a p a l u s t r i s , Myriophyllum (d)  Fish Ali  salmonids  sp., S c i r p u s sp, and  Typha  sp.  fauna  (I959)  r e c o r d s f i f t e e n s p e c i e s o f f i s h from N i c o l a Lake.  a r e r e c o r d e d i n t h e l a k e ; kokanee (Oncorhynchus nerka  Five  (Walbaum)),  -6-  Table 1.  Species composition of Nicola Lake plankton.  Myxophyceae:  Chlorophyceae:  Anabaena sp.  Dictvosphaerium sp.  Aphanizomenon sp.  Staurastrum sp.  Microcystis aeruginosa • Microcystis sp. Baccilariaceae: Stephanodiscus sp.  Protozoa: Ceratium hirundinella  Fragillaria sp. Melosira sp. Copepoda:  Cladocera:  Diaptomus spp.  Daphnla longispina  Cyclops sp.  Bosmina longirostris  Harpacticus sp.*.  Leptodora kindtii Simocepharus sp.* Chydorus sp.* Alona spp.*  Amphipoda:  Ostracoda spp.*  Hyallella*  Hydracarina spp.*  Gammarus* Rotifers: Notholca longispina Anuraea cochlearis Triarthra longiseta Branchionus sp. *  Species observed  inshore water by the author.  two anadromous species of salmon ( 0 . kisutch (Walbaum) and 0 . tshawytscha (Walbaum)), Dolly Varden (Salvelinus malma (Walbaum)) and both resident and anadromous forms of rainbow trout (Salmo gairdneri Richardson).  The  mountain whitefish (Prosopium williamsoni (Girard)) i s the only coregonid inhabiting the lake. Six species of cyprinids are present in the lake.  Redside shiners  (Richardsonius balteatus (Richardson)), northern squawfish (Ptychocheilus oregonense (Richardson)) and peamouth chub (Mylocheilus caurinum (Richardson)) are very abundant in number, while carp (Cyprinus carpio Linneaus), chiselmouth chub (Acrocheilus alutaceum Agassiz) and longnose dace (Rhinichthys cataractae (Valenciennes)) are rarely found. species of sucker in the lake:  There are two  Largescale sucker (Catostomus macrocheilus  Girard) i s abundant, and the bridgelip sucker (C. Columbianus (Eigenmann and Eigenmann)) i s extremely scarce.  The catch record of g i l l nets in 1959  shows that bridgelip sucker were caught only 0.7$ as frequently as largescale sucker. The prickly sculpin (Cottus asper Richardson) i s the sole species of Cottidae and i s one of the most abundant fish species. lota Linneaus) i s also present.  The burbot (Lota  III.  MATERIAL AND METHODS  Three t y p e s o f s e i n e n e t s were used was  of l A  f o r survey purposes.  i n c h mesh and measured 8 by 50 f e e t .  The second  The f i r s t  was o f 1/8 i n c h  mesh s i z e , measured 6 by 30 f e e t and had a bag w i t h a n y l o n c h i f f o n (30 meshes/cm.).  liner  The t h i r d was a simple c o n i c a l shaped tow n e t 9 f e e t l o n g  w i t h a r e c t a n g u l a r open mouth 3 f e e t wide and 2__ f e e t h i g h , made o f n y l o n m a t e r i a l w i t h 20 meshes per i n c h . As a u x L l l i a r y  sampling gear, a s m a l l d i p - n e t and a t r a p were a l s o  The t r a p was a cube o f 3 f o o t  used.  s i d e , w i t h wings 5 f e e t l o n g made o f wire  s c r e e n o f l / l 6 i n c h mesh. In 1959 o n l y q u a l i t a t i v e samplings northwestern  were done a t s e v e r a l beaches i n t h e  b a s i n by weekly s e i n i n g w i t h a Type I n e t and by t r a w l i n g with  a Type I I I n e t towed by boat.  These samplings  and n i g h t from J u l y 8 t o August 27.  were c a r r i e d o u t both day  Specimens were a l s o o b t a i n e d by t r a p -  p i n g and by d i p - n e t t i n g a t the beach a t the n o r t h e a s t e r n end,. In I960, t h r e e sampling (l) and  s e r i e s were c a r r i e d o u t .  For studies of d i s t r i b u t i o n ,  interspecific association,  different  s e a s o n a l movement, h a b i t a t p r e f e r e n c e  s e i n i n g s w i t h a Type I I n e t were done a t 9  s t a t i o n s d i s t r i b u t e d a l o n g t h e l a k e - s h o r e ( F i g . l ) on J u l y 3, 18,  August 1 and 18.  Two s e i n e h a u l s were taken a t each s t a t i o n d u r i n g t h e day-  time from 30 f e e t o f f s h o r e t o t h e shore edge, and each covered an area o f approximately  600 square  feet.  The bottom substratum  s t a t i o n was: S t a t i o n s N, W,,  W_>:  sand.  S t a t i o n s W^,  E,, E j :  sand with submerged p l a n t s .  S t a t i o n s W_j,  E  g r a v e l and r o c k .  i }  E'f.  o f each  seining  F i g u r e 1.  N i c o l a Lake, showing s e i n e s t a t i o n s .  -10(2) -For study of diurnal movement, micro-distribution and feeding activity, several series of samples were taken at four hour intervals with a Type III net at Station N on July 12 - 13 and July 3 0 - 31.  Each series  comprised two hauls towed 60 feet parallel to the shore on each of three different areas.  These sampling areas were located at distances between 0  and 5> 1 0 and 1 5 , and 20 and 25 feet from shore and the area sampled in each case was approximately 200 square feet.  For showing the effect of  wave and cloud condition on distribution, the same samplings were carried out several times under different weather conditions during the daytime. Simultaneously, water temperatures were recorded with a Thermistor. (3)  For study effects of bottom types (such as weed beds, gravel and  sand) on diurnal movement, a Type II net was used to seine at three different bottoms in the northeastern basin on July 27 and August 17.  This  was done shortly after noon when the larvae should have been the most abundant and at midnight when they should have been least abundant, according to the data from Station N.  Two hauls were taken at each station from  3 0 feet offshore to the shore edge. In 1961, 24 hour series of seining with a Type III net were carried out at Station N on July 13 - 1U and July 3 1 - August 1.  The seining  method was exactly the same as that of I960. In the late summer (on August 17 - 18) a Type II net was used for sampling because the efficiency of the Type III net decreased sharply as the fry increase in size.  Three seine  hauls, covering an area of approximately 600 square feet, were done at 30 feet from the shore line in each series of samples.  Simultaneously water  temperatures were recorded, and six plankton hauls were also taken with the Wisconsin type net made of No. 10 bolting silk.  The plankton samples were  obtained from 60 foot hauls taken paralell to the shore line.  Duplicate  -11-  samples were taken at four hour intervals at distances of 5 , 1 5 , and 2 5 feet from shore. The organisms associated with the sandy bottom at Station N were sampled on August 1 and 1 8 with a standard 6" Ekman dredge.  The purpose of  these dredgings was to sample the microfauna, which forms an important food resource of the fish larvae. Six samples were taken at each of three depths, located respectively at 5 , 15 and 25 feet from shore.  The bottom  samples were poured into a plastic bucket f i l l e d with water, and mixed to free the organisms.  This mixture containing the suspended organisms was  poured into the plankton net of No 10. bolting silk.  The sand residue was  similarly treated twice. A l l fishes were preserved i n 1 0 percent formalin i n the field and later retained in kO percent isopropyl alcohol i n the laboratory. Plankton and benthos were preserved i n 5 percent formalin. For the study of behaviour and vertical distribution, observations were frequently made at Station N and some other shore areas i n the northeastern basin during the daytime throughout the summers of 1959 and  I960.  In I960 fish behaviour was observed i n aquaria 16 inches l o n g X 8 . 5 inches wide X 1 0 inches deep.  In these tanks bottom was covered with sand and  f i l l e d with lake water to a depth of 7-5 inches. A wax pencil mark on the side was used to distinguish three equal layers.  Three sides were covered  with paper and one side was left uncovered for making observations. The top was also open.  Five or ten fry of each species were kept in separate  aquaria, and the numbers of f r y in each layer were counted at four hour intervals. intervals.  Each count consisted of three duplicates taken at five minute  IV.  ENVIRONMENTAL CONDITIONS OF INSHORE WATER  (l) (a)  Limnological Conditions  Physical conditions The temperature  o f i n s h o r e water ( 3 0  f e e t o f f t o t h e shore l i n e ) i n  summer i s h i g h e r than t h a t o f t h e o f f s h o r e water d u r i n g t h e daytime and up to m i d n i g h t .  T h i s tendency was observed a l l a l o n g t h e l a k e .  the temperature  From midnight  o f i n s h o r e - w a t e r tends t o be lower than o f f s h o r e water.  example o f s u c h . d i e l change o f temperature  An  i s g i v e n i n F i g . 2, the i n v e r -  s i o n s o f t h e r m a l c o n d i t i o n s p r o b a b l y o c c u r r i n g s h o r t l y a f t e r midnight and between 0800 and 1200 hours. hours a l l through the summer.  The h i g h e s t temperature The temperature  was observed a t 1600  gradients are very stable.  The t h e r m a l c l i n e a t 1600 hours i n F i g u r e 2 p e r s i s t e d i n the presence o f 3 i n c h waves. (b)  Even w i t h 10 i n c h waves the t h e r m a l g r e d i e n t was p r e s e n t .  Bottom type There a r e a v a r i e t y o f bottom t y p e s a l o n g t h e shore l i n e o f N i c o l a  Lake, i n c l u d i n g  sand, g r a v e l , rock and mud, any o f which may support growths  of aquatic plants. beaches,  G e n e r a l l y , the a r e a s around  the i n l e t s form  sandy  e s p e c i a l l y a r e a s e a s t t o Q u i l c h e n a Creek, the N i c o l a R i v e r and the  n o r t h e a s t e r n end o f the l a k e , f o r heavy south o r southeast winds a r e p r e v a i l i n g so t h a t p a r t i c l e s from the i n l e t a c t i o n a l o n g t h e shore toward  the east.  creeks a r e c a r r i e d by the wave  A l o n g these exposed  shores t h e r e  i s no development o f Typha o r S c i r p u s a l t h o u g h submerged p l a n t s a r e observed on the bottom a t depths g r e a t e r than 3 f e e t .  By wind a c t i o n two l a r g e  bars have been formed; one a p p r o x i m a t e l y one m i l e n o r t h o f N i c o l a the o t h e r one and h a l f m i l e s n o r t h e a s t o f Q u i l c h e n a .  sand  R i v e r and  I n s i d e these b a r s  -13-  JULY 12 1 6 0 0 ^<*5 23 9  22 1  230  33Q 229  32 B  22 B  22 8  2 3C  23 O  23 O  2, 22  33 O  23 O  33 O 22 8  '245 «,0  32 9  O  P.  23 7  22 8  23 8  22  B  8  22 7  22 3  IO 20 30 40 50 DISTANCE FROM SHORE (FEET)  O  0800  2000 PO?  TO 9 21 O  210  2IO  21 O  ?IO  210  210 21 O  303  S  1  '20  IO 20 30 40 SO DISTANCE FROM SHORE (FEET)  9^2^0  2t.O  21 O  2IO  2IO  2IO  2IO  21 O  21 O  ?l  O •  ^9fl ^19 2 2 IO  O  19 2  19 I  19 2  19  19 t  2  19 2  19 2  20 9 | 21 O  21 O  19 3  21 O 19 2 19 2  9 3  19 2  19 3  ».3  19  19 3  19 1  19 3  3  210  19 2  19 2  21 O  10 20 30 40 50 DISTANCE FROM SHORE (FEET)  1200  2400 ^95 19 5  i9"5  - 19 5 ' " ' t ^ - t 9'5 ,  ul |  X  IO 20 30 40 50 DISTANCE FROM SHORE (FEET)  l9~5  191  !9"5  19 5  19 5  19.5  I9T"  2 1  .19 5  19 5  19 5  \, O  F i g u r e 2.  J,^2I O  21.1 | 2 M  19 5  5  j  211 3 , 02 , 03 , 0  21 O  19 5 19 5 ,  IO 20 30 40 SO DISTANCE FROM SHORE (FEET)  21 O  • 21 2  lo  56  DISTANCE  36  FROM  2IO  2IO  21 0 |  To  SHORE  2IO  21 O  209  (FEET)  T y p i c a l t h e r m a l c o n d i t i o n and i t s d i u r n a l change i n t h e i n s h o r e water. ( J u l y 12 - 13, I960)  -14there are calm bays, where fine sand and mud are deposited. These areas have plenty of vegetation.  The rest of the eastern shore i s predominantly  gravel or rock without vegetation. The wastern shore has no major inlets and i s rarely affected by wave action, so that there i s no appreciable deposition of sand i n this area. The most of the western shore i s covered with gravel or rock mixed with coarse sand where Scirpus forms a narrow (10 - 15 feet wide) band running parallel to the shore.  A steep c l i f f i s present around the Armstrong  Point and extends about one mile east of the point.  Another c l i f f approx-  imatly 200 yards wide i s present just north of Station W4. In the southwestern basin Scirpus and Typha are abundant along both the east and west shores. At the shore line there i s a transition from beach vegetation compact plant zone to submerged aquatic vegetation, rooted in a soft organic mud bottom.  (2)  Plankton  A l l animal species found i n the samples taken at Station N were counted under a microscope after f i l t e r i n g off decayed blue-green algae and other microorganisms with No. 10 bolting silk.  Table 2 summarizes the  composition of these samples. In addition to the animals listed i n Table 2 a variety of insect lavae, chironomids, mayflies, stoneflies, caddisflies and phantom midge, corixlds and water mites were also found i n the samples, although most of them were much less numerous than the crustaceans. Distribution of these animals based on the samples i s tremendously variable.  Wave action may play an important role.  It may not only d r i f t  the animals from the offshore area but also l e t benthic animals such as  -15Table  2.  D i e l changes o f p l a n k t o n  i n t h e i n s h o r e water.  Each number i n d i c a t e s  the t o t a l o f 6 h a u l s a t S t a t i o n N. J u l y 13 - 14, 1961  Date Taxon^v  1600  Time \Wave h e i g h t  3"  2000 1"  2400  14"  0400  0800  0  1200  Total  2h"  ROTATORIA 120  150  700  852  934  765  4166  1645  1828  1008  389  5295  144  559  2228  706  154  3819  4869  743  210  80  140  660  511  444  Diaptomus  38  487  nauplius  28  Brachionus CRUSTACEA Cyclops  239  138  703  Bosmina  19  13  2  62  96  3  4  2  1  10  28  18  5  12  41  92  1065  603  112  2408  2072  6293  Simocepharus Alona Chydorus OSTRACODA  1  AMPHIPODA  2  33  5098  11790  Daphnia  1  4  1  1  8  INSECTA EPHEMEROPTERA PLECOPTERA  larvae  larvae  DIPTERA l a r v a e  20  143  larvae  TRICHOPTERA  larvae  HEMIPTERA  7  61  197  2  2  6  1  26  5 11  9  35  123  97  639  15  DIPTERA pupae PTYCHOPTERA  1  18  '  21  6 14  Corixidae  10  38  2  2  3  27  ACARINA Water m i t e  9  6  3  1  5  -16Table  2.  Continued.  \  J u l y 31 - August 1,  Date  1961  1600  2000  2^00  0400  0800  1200  0  0  0  0  0  1*  1810  1420  830  130  250  350  4790  210  559  463  488 2383  902  5005  Diaptomus  29  23  9  20  39  23  143  nauplius  75  437  820  1741  432  424  3929  Da phnia  14  8  17  10  10  29  88  Bosmina  187  778  239  319  60  87  1670  7  34  73  32  9  3  158  Alona  10  15  6  9  35  24  99  Chydorus  63  491  184  154  748  666  2276  Taxon  \  Time \Wave  height  Total  ROTATORIA Brachionus CRUSTACEA Cyclops  Simocepharus  OSTRACODA  1  1 1  AMPHIPODA  1  1  3  INSECTA EPHEMEROPTERA PLECOPTERA DIPTERA  larvae  larvae  larvae  7  5  4  5  21  6  23  3  2  18  12  63  9  42  97  17  31  31  227  DIPTERA pupae PTYCHOPTERA l a r v a e TRICHOPTERA HEMIPTERA  2  13  22  11  2  16  19  1  4  19  9  6  2  4  9  5  2 3  67  larvae Corixidae  52  A CARINA Water mite  3  29  -17Table 2. Continued.  August 17 - is , 1961  \ Date Taxon  \Time \Wave height  1600 2000 2400 0400 0800 1200 Total 0  0  0  0  1"  1*  ROTATORIA Brachionus  16060  410 2330  156 3780 10450 33186  CRUSTACEA Cyclops Diaptomus nauplius  6H 8 456  810 1079  6869  88 IO56 2702  799  484  60Q8  . 132  68  96  23  775  15  38  150  36  14  119  86  38  497  1196 1636  1538  Daphnia  34  39  24  Boamina  20  10  15  Simocepharus  12  96  140  7  6  13  8  4  4  42  . 131 120  175  84  29  88  627  Alona Chydorus  24 125  1  OSTRAOODA  2  1  AMPHIPODA INSECTA  1  8  23  2  4  8  31  28  37  7  6  21  1  4  1  3  13  23  43  130  16  2  7  199  EPHEMEROPTERA larvae  5  3  6  PLECOPTERA larvae  5  6  6  DIPTERA larvae  6  14  DIPTERA pupae  1  PTYCHOPTERA laevae  1  TRICHOPTERA larvae  1  HEMIPTERA Corixidae  4  1 2  8  155  66  6  241  ACARINA Water mite  10  10  20  -18-  chironomid larvae, Alona, Chydorus and amphipods float up into the shallow water.  Daphnia and Chydorus in the early summer seem to show this effect  (Table 2 ) . Vertical movement by pelagic plankton may be another factor influencing abundance i n inshore water.  After upward migration at night they may  get there either by drifting or by horizontal movement. Predation by fish may affect the number of the animals. section.  This will be discussed in a later  Probably a l l these factors may cause daily fluctuations of their  abundance. There seems to be a trend i n distribution toward the shore.  Cyclops,  Diaptomus, Chydorus and chironomid larvae are much more abundant in the shallowest water than in the deeper water except during late summer (significant at 1% level by F-test).  These animals are the main food for the fish  larvae so that as far as food resources are concerned the shallower near shore zone i s more favouable.  (3)  Bottom Fauna  The numerical analysis of the dredgings i s summarized in Table 3Some pelagic species (Cyclops, Diaptomus, Da phnia etc.) that may have been added during the sorting process are excluded from the table. Chironomids, the dominant forms, made up approximatelly 75% by number of the total bottom fauna.  The majority of the animals were 4 mm-  in total length and individuals exceeding 10 mm. were rarely found.  or less The  animals were most abundant at the intermediate depth and scarcest at the shallowest (highly significant by F-test, Table 3 ) .  The phantom midge  larvae forms about 10% of the total number of animals and are more numerous in the deep area (highly significant by F-test).  Oligochaetes, amphipods,  -19Table 3 « Bottom fauna of the inshore area at Station N. Each number indicates the total of six replicates. Depth : I <( II { i l l  Date Taxon  August  Depth  I  II  1 ,  August 1 8 , 1 9 6 1  1961  III Total  I  II  III Total  CRUSTACEA Harpacticus Alona  13  4  4  1  35  117  165  3  84  187  374 109  Chydorus  1 0 3  ephippium  100  1  8  OSTRACODA  2  1  46  AMPHIPODA  2  2  228  2  71  7 3  2  6  15  23  924  4025  4573  -4  1  •  49 232  5  6  4  28  35  69  88  227  384  9  16  11  27  7  8  1 5  231  83  319  4  7  16  27  1 4  7  7  28  6522  236  2773  2080  5089  1  6  6  2  4  1 2  639  871  4  7  16  27  INSECTA EPHEMEROPTERA larvae PLECOPTERA larvae DIPTERA larvae DIPTERA pupae PTYCHOPTERA larvae  33  1 9 9  NEMATODA OLIGOCHAETA HIRUNIDAE GASTROPODA  1 6  5  -40  58  1 1  8  1 5  11  34  114  9  27  155  191  6  2  1  2  5  1  -20and  two  crustacean  samples a l t h o u g h  genera, Alona and  Chydorus, were commonly found i n the  the f r e q u e n c i e s o f o c c u r r e n c e  were l e s s than 5%.  The  g r e a t e r the d i s t a n c e from the water edge, the more abundant these are, although  with  Chydorus and  the amphipods i t i s not  animals  statistically  significant.  (4)  O t h e r F i s h S p e c i e s and O l d e r  Diurnal onshore-offshore  movement by a d u l t s o f v a r i o u s  f i s h e s has been r e p o r t e d by many b i o l o g i s t s . and  Spoor and  and  o f f s h o r e i n the .morning.  d i u r n a l movement have been r e p o r t e d 1959; Johannes and  I960), B.  C.  and  Evermann and  Schloemer (1938). observed t h a t suckers and  i n s h o r e i n the evening  Ali,  Fish  northern  freshwater Clark  o t h e r f i s h move  S i m i l a r p a t t e r n s of  f o r t h e r e d s i d e s h i n e r (Crossman,  L a r k i n , 1 9 6 l ) , peamouth chub ( A l i , 1959;  squawfish and  (1920),  l a r g e s c a l e sucker  MacLeod,  ( A l i , 1959)  i n various  lakes. Table 4 shows weekly s e i n e catches a t 5 d i f f e r e n t beaches i n the  e a s t e r n b a s i n o f the l a k e d u r i n g the summer o f 1959between 1300  and  1500  hours and  observations  o f the above a u t h o r s ,  movement was  not  clear-cut.  Day  s e i n i n g was  n i g h t s e i n i n g between 2300 and  As f a r as a d u l t f i s h were concerned, the present  During  although  0100  i n the case o f the  northmade  hours.  f i n d i n g s agree with  the  s c u l p i n s the  e a r l y and mid-summer the one  year o l d  s h i n e r s appeared a t the i n s h o r e area d u r i n g the daytime as w e l l as the  1959;  during  night. I t i s p o s s i b l e to conclude t h a t throughout the summer, the i n s h o r e  i s much l e s s crowded by l a r g e r f i s h e s d u r i n g the day  area  than d u r i n g the n i g h t .  -21Table 4 .  T o t a l c a t c h e s by weekly basin,  1959.  s e i n i n g a t 5 s t a t i o n s i n the  Youngs o f the y e a r are  excluded.  July  Date  August  8  15  22  Day Night  30  37  44  35  Large S c a l e Scuker 1 year o l d  Day Night  1 15  7 62  N o r t h e r n Squawfish Adult  Day  N o r t h e r n Squawfish 1 year o l d  Day Night  Peamouth Chub Adult  Day Night  Peamouth Chub 1 year o l d  Day Night  Bedside S h i n e r Adult  Day Night  Redside S h i n e r 1 year o l d  Species Large S c a l e Adult  Scuker  Night  12  36  19 13 12  12  20  26  46  32  24  17  35 30  1 22  2 72  5  2 23  4 14  15  3 2  3 17  4 18  31  2 33  11  19  22  3 15  14  1  90  21 119  Day Night  47  105  Prickly Sculpin Adult  Day Night  122 114  147  5  109  76  B r i d g e l i p Sucker Adult  Day Night  2  Mountain  Day Night  Whitefish  Kokanee  Day Night  Rainbow T r o u t  Day Night  S p r i n g Salmon  Day Night  Burbot  Day Night  215  29  6  1  10  16  northeastern  94  Al  177  1  28  5  10  23  22  45  5  20  4  36  6  428  345  156  1  6 5  3 1  12 141  11  254 75  181 15  179  37  50 373  371 634  388 497  1 1  2  -431  2  55  1  14 136 352  1 1  3  2  1  1 1  1  -22(5)  Terrestrial Insects  Stone f l i e s , may f l i e s , caddis f l i e s and chironomids were identified depositing their eggs close to the shore throughout the length of the shore line.  They tended to be most dense early in the morning and late in the  afternoon.  Starrett (1950) reports that on the Des Moines River the emer-  gence of Ephemeroptera and Tricoptera seemed to be mainly in the late afternoon and dusk hours.  It was also frequently observed that both adult and  fry of redside shiners were feeding on these adult insects along the lakemargin.  V.  MORPHOLOGICAL DESCRIPTION OF LARVAE AND YOUNG  The necessity of correctly identifying the larvae and young of fishes has been long recognized.  Of the five species of interest only the redside  shiner (Weisel and Newman, 1951) and largescale sucker (MacPhee, I960) have been f u l l y described for a l l developmental stages. As a means of identifying larval fishes three characters have been usedj location and concentration of pigment (Pritchard, 1930. Fish, 1929, 1932,  Balinsky, 1948; Wenn and Miller, 1954); myomere counts (Leim,  Fish, 1929,  1924;  1932) and pre-and postanal measurements (Wenn and Miller, 1954).  The chief characteristics used for identification in this study were the location and distribution of pigments and the position of fins and anus. Myomere counts were not done. A l l specimens were taken from the inshore area. Prickly sculpin (Cottus asper) i s the only cottid in the lake.  Bridge-  l i p sucker (Catostomus Columbianus) i s extremely rare. A l i (1959) reports bridgelip suckers are primarily stream dwelling fish with the habit of scraping rocks to collect food, and young-of-the-year of this fish were seen in large numbers in Nicola River outlet. According to Northcote (personal communication) bridgelip sucker has never been found in Moore Creek, one of the main inlets of the lake, whereas many largescale suckers do spawn in this creek in the spring.  Probably bridgelip suckers spawn in  the outlet and young-of-the-year spend the f i r s t summer in the river.  Thus,  i t could be surmised that a l l catostomid larvae found in the lake during the summer are largescale suckers. Carp, one of the cyprinids, i s an extremely rare species.  Only one  -24larva was caught during three summer's surveys.  Whether longnose dace can  be separated from other cyprinids in postlarval stage remains to be determined . Winn and Miller (1954) reported that an oval internal pigment spot near the base of the upturned portion of the vertebral column was characteristic of postlarbae of Ptychocheilus and Gila.  However, such a pigment spot was  also observed in peamouth chub and redside shiner.  Thus, this spot was not  used for seperation by the author.  (l) (a)  Morphological Description  Largescale sucker Post larva:  15.0 mm.  fork length; straight intestine; (Fig. 3-A);  anus distinctively posterior; body remarkably elongated; eye large, mouth terminal and oblique; caudal f i n not forked and without developed f i n rays. MacPhee (i960) reported that the two lobes of the caudal f i n appear in some species when about 14 mm.  in average length, whereas they do not appear in  other fish u n t i l about 16 mm.  in average length.  There i s a row of pigments  spots beginning just behind the opercle, and forming a line on the anterior mid-ventral region of the body. Larva:  20.8 mm.  fork length (Fig. 3-3); with rounded snout; mouth  becoming more ventral; four pairs of dark margins visible on the g i l l s ; with 14 dorsal f i n rays and 7 anal f i n rays; caudal and pectoral fins with f u l l y developed rays; pelvic fins and rays commencing to form; dorsal f i n fold near caudal lost; a larger portion of the ventral f i n fold from behind pelvic fins to anus present.  According to MacPhee (i960) such f i n folds  had disappeared in an individual of the same length. the shape of the letter N.  The intestine takes  In white suckers (Stewart, 1926) this i n i t i a l  -25-  Figure 3.  Largescale sucker fry.  -26-  coiling of the intestine occurs in fry of 16 mm. whereas in largescale sucker i t does not occur until the fry are 17 to 18 mm. long. Young larger than 24-0 mm.  (Fig. 3-C); with round snout and deeply  forked caudalj fins fully developed without f i n folds; dark margins of the g i l l s s t i l l visible; intestine simply coiled. (b)  Northern squawfish Larva:  11.0 mm.  fork length (Fig. 4-A); body elongated; eye large;  mouth terminal oblique; pectoral fins present, rays developed in unforked t a i l ; position of dorsal and anal f i n indicated by a concentration in the marginal f i n fold; two series of black pigment spots on the anterior ventral region of the body beginning from just behind the opercle present (Fig. 5); a oval internal pigment spot near the base of the upturned portion of the vertebral column also present. Larva:  12.2 mm.  fork length (Fig. 4-B); with marked oval caudal spot;  with 8 dorsal f i n rays; anal and pectoral f i n rays not f u l l y developed; caudal f i n with fully developed rays; intestine of the postlarval fish (10.0 to 15.0 mm.)  straight.  Young larger than 19.0 mm.  fork length (Fig. 4-C); with completely  formed fins; the dorsal and anal fins with 8 rays; posterior end of dorsal fin base directly above the front end of the anal f i n base; intestine with the shape of the letter N; occipital pigments forming a heart shape with a median lighter band nearly dividing the pigment area (Fig. 5). Young larger than 20.0 mm.  fork length; with a distinct dark spot at  the base of the candal f i n ; mouth large and extending to the front of eye. (c)  Peamouth chub Larva:  10-3 mm.  fork length (Fig. 6-A); body elongated; eye large;  mouth terminal oblique; pectoral fins present; position of dorsal, anal and  -27-  A  B  C  Figure 4.  Northern squawfish fry.  Figure  5.  V e n t r a l view o f a n t e r i o r p a r t o f n o r t h e r n squawfish ( A ) , peamouth chub^(B) and r e d s i d e s h i n e r ( C ) . D o r s a l view o f head o f peamouth chub (D) and n o r t h e r n ' s q u a w f i s h (E).  -29-  Figure 6. Peamouth chub fry.  -30p e l v i c f i n s not apparent; no f i n r a y s developed i n the unforkeci t a i l ; s e r i e s o f b l a c k pigment spots present body b e g i n n i n g  j u s t behind  l a r v a o f 13.2  mm.  f a i r l y well-developed  on the a n t e r i o r v e n t r a l r e g i o n o f the  the o p e r c l e  ( F i g . 6-B);  three  ( F i g . 5).  with  s l i g h t l y forked  f i n r a y s ; d o r s a l and  c a u d a l f i n with  a n a l f i n s developed; rays formed;  p o s i t i o n o f p e l v i c f i n s i n d i c a t e d ; d o r s a l f i n f o l d a n t e r i o r to the d o r s a l fin  disappeared,  but the r e s t o f i t s t i l l  i n t e s t i n e o c c u r r i n g i n f r y o f 15.0 Young:  22 mm.  exists; i n i t i a l  f o r k l e n g t h ( F i g . 6-C);  o f the d o r s a l f i n base l i e s  anal f i n .  Mouth s m a l l , not  a l l f i n s completed w i t h  r e a c h i n g the f r o n t o f the  a complete h e a r t  the  letter  (d)  and in  Redside  shiner  Larva:  8 mm.  t o t a l l e n g t h ; body e l o n g a t e d ;  straight.  taking  eye ;large; mouth t e r m i n a l  merely as f i n f o l d s ; a few  rays j u s t  evident  pigment spots ( u s u a l l y  These c h a r a c t e r i s t i c s a r e i d e n t i c a l to the  prolarvae  Newman (1951).  J u v e n i l e l a r g e r than 19.0  mm.  f o r k l e n g t h ( F i g . 7-B);  ly  formed; d o r s a l f i n behind  at  the f r o n t o f a n a l f i n ; t a i l d e e p l y  (e)  occipital  on the a n t e r i o r v e n t r a l r e g i o n o f the body ( F i g . 5);  d e s c r i b e d by W e i s e l and  fin  eye;  the  N.  the s l i g h t l y f o r k e d caudal f i n ( F i g . 7-A);  intestine  posterior  shape ( F i g . 5); i n t e s t i n e c o i l e d ,  oblique; p e c t o r a l f i n s appearing  2 t o 4) p r e s e n t  The  well  s l i g h t l y a n t e r i o r to the f r o n t edge o f  pigments forming shape o f the  the  mm.  developed f i n r a y s ; d o r s a l and a n a l f i n s w i t h 8 f i n r a y s . end  c o i l i n g of  pelvic fins;  a l l fins  c e n t e r o f d o r s a l f i n base  completelying  forked; d o r s a l f i n with 9 rays;  l o n g , with 18 r a y s ; i n t e s t i n e taking, the shape o f the l e t t e r  anal  N.  Prickly sculpin Larva,  12.0  mm.  t o t a l l e n g t h ( F i g . 7-C);  dorsal f i n fold originating  -31-  A 3  Figure  7.  R e d s i d e ' s h i n e r f r y (A, B) and  MM  p r i c k l y s c u l p i n f r y (C, D).  -32j u s t behind the head; 29 elements o f d o r s a l f i n r a y s w i d e l y separated the area between 9 t h and o r i g i n a t i n g from anus and  10th f i n r a y s s l i g h t l y depressed;  ventral f i n fold  c o n t a i n i n g 17 elements o f a n a l f i n r a y s ; p e c t o r a l  f i n l a r g e ; c a u d a l f i n round, and  r a y s p r e s e n t ; a few  chromatophores d e v e l -  oped a t the head r e g i o n and on t h e v e n t r a l p a r t o f the body j u s t to  and  anterior  anus. Juvenile:  14.0  mm.  ( F i g . 7-D);  1 s t d o r s a l f i n separated from  d o r s a l ; 1st d o r s a l w i t h 9 f i n r a y s and r a y s ; head s l i g h t l y depressed; mouth l a r g e ,  l.a.  2nd d o r s a l w i t h 20; a n a l f i n with  4 o p e r c u l a r s p i n e s developed;  17  eye s m a l l ,  s t i l l o b l i q u e ; white body marbled with b l a c k chromatophores.  (2) (a)  2nd  Keys t o P o s t l a r v a l and  Young F i s h e s  Key t o p o s t l a r v a l f i s h e s o f N i c o l a Lake D i s t a n c e from f r o n t o f anus t o p o s t e r i o r edges o f c a u d a l f i n l o n g e r  than d i s t a n c e from a n t e r i o r p o i n t o f head to f r o n t o f anus. - - - - Family Cottidae (Cottus asper  l.b.  D i s t a n c e from f r o n t o f anus t o p o s t e r i o r edge o f c a u d a l f i n l e s s  only)  than  t w i c e d i s t a n c e from a n t e r i o r p o i n t o f head to f r o n t o f anus. Family C y p r i n i d a e  I.e.  2  D i s t a n c e from f r o n t o f anus t o p o s t e r i o r edge o f c a u d a l f i n more than  twice d i s t a n c e from a n t e r i o r p o i n t o f head to f r o n t o f anus. - - - - Family (Catostomus  Gatostomidae macrocheilus)  -33-  2.a.  Double bands of black pigment on both ventro-lateral surfaces,  beginning behind opercle (Fig. 5-A)  2.b.  -----  ptychocheilus oregonense  Three bands of black pigment on ventral surface of body; one  median and one on each ventro-lateral surface (Fig. 5-B). - - - - Mylocheilus caurinum  2.c.  One central, or median band of pigment, usually formed with 2 to  k chromatophores, on ventral surface of body (Fig. 5-C). - - - - Richardsonius balteatus  (b) I.a.  Key to juvenile fishes of Nicola Lake Head depressed, two dorsal fins, the f i r s t with spines. - - - - Family Cottidae (Cottus asper only)  l.b.  Head round on top, snout blunt, mouth and lips fitted for sucking,  single, dor sal f i n .  Four pigmented margins of g i l l s visible through the  opercle.  - - - - Family Catostomidae (Catostomus macrocheilus)  I.e.  Head pointed, mouth and lips not fitted for sucking, g i l l margins not  visible through opercle, single dorsal f i n . - - - - Family Cyprinidae - - - - 2  2.a.  Distinct dark lateral band running from base of caudal peduncle  to opercle.  - - - - Rhinichthys cataractae  -342.b.  Without such a distinct band.  3.a.  3  Posterior edge of dorsal fin base lying much behind front  of anal f i n base. Anal f i n base very long. - - - - Richardsonius balteatus  3.b.  Posterior edge of dorsal f i n lying approximately above  front of anal fin base.  4.a.  - - - - 4  Complete heart shaped figure of pigment on occipital  region of head.  No caudal pigment spot. - - - - Mylocheilus caurinum  4«b.  Broken heart shaped figure of pigment on occipital  region of head.  Young larger than about 20 mm. with a  distinct dark spot at base of caudal f i n . - - - - Ptychocheilus oregonense  VI.  (l) (a)  DISTRIBUTION AND MOVEMENT  Spawning and First Appearence of Fry on the Inshore Area  Largescale sucker Geen (1958) states that largescale suckers appear to spawn primarily  in outlet streams i f such are available, but they w i l l , i f necessary, spawn in inlet streams or even lake margins. In several shallow gravelly areas near the shore of Nicola Lake many aggregating adult fishes and numerous depressions were observed.  Similar observation were made of humpback  sucker, %yrauchen texanus (Abbott) in Lake Havasu, California, by Douglas (1952).  Inlet spawners were also observed i n Moore Creek in 1958 - 1959However, i t i s supposed that the inlet spawners, due to their relative infrequency, do not contribute as significantly to the recruitment of the total lake population. Geen (1958) states that the spawning migration of the largescale sucker in British Columbia takes place during April and May depending on the particular locality.  At the middle and end of May, 1959, aggregations of  the spawners and depressions made by them were observed i n the lake margins. According to Northcote (personal communication) the Moore Creek spawners probably migrated into the creek i n the last two weeks of May, 1959, and many spent fish were caught i n the creek on June 13. These records suggest that the suckers start to spawn around the middle of May and probably finish by the middle of June. Postlarval f i s h appeared around the Moore Creek mouth and Station W/ on July 8, 1959. Seine hauls taken on July 3, I960, yielded young larvae  -36at  a l l o f the  s t a t i o n s except S t a t i o n N.  The  as estimated from Geen's data appears to be  incubation  10 days.  period  i n the  At Baker Lake the f r y  remained a p p r o x i m a t e l y a week to 10 days i n the g r a v e l o f the stream before  the y o l k  sac was  w i t h t h a t o f the (b)  Northern  absorbed  f i s h at Nicola  (Geen, 1958)• T h i s f e a t u r e almost  bed  coincides  Lake.  squawfish  Spawning o f squawfish i n N i c o l a Lake has not Cartwright  lake  (1956) r e p o r t s t h a t n o r t h e r n  e a r l y J u l y i n the m a j o r i t y  to date been i n v e s t i g a t e d .  squawfish spawn throughout June  o f l a k e s i n B.  C.  A l s o , he  and  s t a t e s t h a t i n some  l a k e s a t l e a s t , spawning can o c c u r w i t h i n the l a k e as w e l l a s , o r i n s t e a d o f , i n streams. and  E/, and  In N i c o l a . Lake the l a r v a e appear f i r s t around S t a t i o n N  d u r i n g the e a r l y summer t h e y a r e abundant i n the  the n o r t h e a s t e r n  b a s i n o f the l a k e .  shore water a t  Thus, s i n c e n e i t h e r spawning  nor  l a r v a l squawfish have been found i n Moore Creek, the i n d i c a t i o n s a r e  that  the  being  spawning a r e a s a r e i n the main l a k e with the most probable s i t e s  some o f the g r a v e l beaches. 1 i n I960.  Cartwright  The  f i r s t appearence o f the l a r v a e was  (1958) s t a t e s t h a t i t seems u n l i k e l y t h a t the  t i o n p e r i o d o f squawfish i n much g r e a t e r than one i s the  case w i t h o t h e r  c y p r i n i d s t h a t the  week.  squawfish l a r v a e remain i n  Hence i t i s u n l i k e l y t h a t squawfish spawn b e f o r e  June i n t h i s (c)  incuba-  the  sac i s b e i n g  the middle o f  lake.  Peamouth chub A few  spawning peamouth chub were observed i n Stump Creek i n the  middle o f Ma,y, two  July  I t i s probable as  g r a v e l where t h e y were spawned f o r a week or so w h i l e the y o l k absorbed.  on  1959.  MacLeod ( i 9 6 0 ) r e p o r t s t h a t , f o r a p e r i o d o f one  weeks d u r i n g the l a t e r p a r t o f May,  the g r a v e l shores on N i c o l a Lake and  or  chub congregate i n l a r g e numbers on  o f t e n found c l o s e to the  beach.  -37The f i r s t 1959,  appearence  o f the l a r v a e o f chub i n the l a k e was  when a s m a l l number were taken a t the mouth o f Stump Creek.  obvious t h a t these are from the stream p o p u l a t i o n , because e a r l i e r i n the stream than t h e l a k e , and because did  a b u n d a n t l y a t S t a t i o n VI/,  appearances  It i s  spawning o c c u r r e d  In a d d i t i o n ,  c o l d e r than i n the stream and hence i t i s v e r y u n l i k e l y  t h a t development would be f a s t e r i n the l a k e . appeared  On J u l y 2, 1959,  and a t S t a t i o n N on J u l y 4«  were a l s o observed i n I960.  e a r l y J u l y , I960, i t i s supposed  larvae Similar  From the d i s t r i b u t i o n o f the l a r v a e  t h a t the l a k e spawners spawn on the  g r a v e l shores a t the n o r t h e a s t e r n b a s i n , e s p e c i a l l y the shores near VIi and (d)  15,  l a r v a e o f a s i m i l a r stage  not o c c u r i n o t h e r p a r t s o f the l a k e u n t i l much l a t e r .  the l a k e water was  in  on June  Station  E. (  Redside s h i n e r A c c o r d i n g t o C a r l e t a l . (1959) the s h i n e r spawns over an  p e r i o d , from l a t e May  t o e a r l y August.  extended  In some l o c a l i t i e s spawning o c c u r s  over g r a v e l bottoms i n streams, w h i l e i n o t h e r s eggs a r e d e p o s i t e d amongst submerged p l a n t s near the l a k e s h o r e . observed a t S t a t i o n N, E at  /  and VI , f  In N i c o l a Lake the l a r v a e were  first  and t h e y v;ere abundant i n the shore water  the n o r t h e a s t e r n b a s i n o f the l a k e i n the e a r l y summer.  Thus, the  s h i n e r s p r o b a b l y spawn i n s e v e r a l i n s h o r e a r e a s o f the n o r t h e a s t e r n b a s i n . The f i r s t of  data when the l a r v a l f i s h were caught a t s e v e r a l shore  the n o r t h e a s t e r n b a s i n was  J u l y 16, 1959-  found i n the t r a w l i n g samples on August  13-  A- few p o s t l a r v a e were  sites  still  Weisel and Newman (1951) s t a t e  t h a t i t p r o b a b l y takes from 5 to 10 days f o r the eggs to h a t c h i n n a t u r e a t water temperature get  o f 1? - 18°C, and from 17 t o 24 days a f t e r h a t c h i n g t o  the p o s t l a r v a l stage (10.4  21 - 23°C.  to 11.8  S i n c e water temperature  mm.)  a t a l a b o r a t o r y temperature  of  from the middle o f June t o the middle  -38o f J u l y was  12  - 2A°C i n the l a k e , i t i s probable t h a t the f i s h  s t a r t e d to  spawn about the middle o f June, and b r e e d i n g a c t i v i t i e s continued u n t i l the middle o f J u l y , (e)  Prickly  sculpin  Spawning o f p r i c k l y s c u l p i n has not been s t u d i e d .  C a r l et a l .  note t h a t i n d i v i d u a l s o f t h i s s p e c i e s spawn from F e b r u a r y t o June, in  streams under b o u l d e r s .  In mid-June,  the shore water e a s t o f Moore Creek.  (1959)  usually  1959 p o s t l a r v a e were observed i n 3  The r e s u l t o f s e i n i n g on J u l y 3,  I960,  shows t h a t S t a t i o n Vfy. on the west shore of the l a k e had an extremely h i g h c o n c e n t r a t i o n o f l a r v a e as compared w i t h t h a t a t any o f the s t a t i o n s on the east shore.  The evidence was  not s u f f i c i e n t t o determine whether t h e y had  migrated from the streams or had  (2)  been spawned i n the a r e a .  Seasonal Movement  Seasonal movements a r e i n d i c a t e d by the changes i n r e l a t i v e abundance determined  by b i w e e k l y s e i n i n g s taken w i t h a Type I I net a t 9 d i f f e r e n t  stations.  A n a l y s i s was  done a f t e r making the f o l l o w i n g assumptions;  a)  e f f i c i e n c y o f the s e i n e i s the same f o r a l l s p e c i e s a t a l l stages d u r i n g their f i r s t  summer r e g a r d l e s s o f bottom substratum, and  the f r y a r e d i s t r i b u t e d i n the i n s h o r e area w i t h i n 30 between 1000 (a)  f e e t o f the  shore  hours,  Largescale sucker On  July  were s t i l l W^.  and 1600  b) the m a j o r i t y o f  3, I960, the l a r v a e which appeared i n the most i n s h o r e waters  s m a l l i n number though  they v>ere r e l a t i v e l y abundant a t S t a t i o n  On J u l y 18, t h e y showed a h i g h c o n c e n t r a t i o n a t the s t a t i o n s i n the  n o r t h western  p a r t o f the l a k e ( F i g . 8 ) .  These f i g u r e s o f d i s t r i b u t i o n  suggest t h a t the l a r v a l f i s h tended to m i g r a t e toward  the n o r t h i n the  -39-  S T A T O IN S F i g u r e 8.  Percentage o f c a t c h o f l a r g e s c a l e sucker i n d i c a t e d by b i w e e k l y seine h a u l s .  f r y a t 9 s t a t i o n s as  -40-  early summer. However in mid-to late-summer they were relatively abundant at Stations to^and Eg.  Thus, the larvae concentrated in the northeastern  area probably dispersed toward the south along both sides of the lake shore. (b)  Northern squawfish In the early summer the larvae were caught in great numbers at the  northeastern area (Stations N and Wy.) (Fig. 9)they were most abundant at Station E/.  In the mid and latesummer  In the latesummer, however, f a i r  numbers of the fish were also caught at the shore in the central part of the basin. This indicates that they did not migrate significantly in the early summer whereas later on they gradually dispersed themselves along the shore towards the outlet of the lake. (c)  Peamouth chub On July 3 the highest concentration of larvae was at Station "/ which  i s suspected to be the main spawning place (Fig. 10).  On July 18, they  were also abundant at Stations N and E/ as well as Station W/.  Probably  they migrated towards the north and got to Station E j , in the early summer, via the north end beach.  In the midsummer, the catch data shows entirely  different results, the larvae were much more abundant at Stations Wj and Ej. Apparently they moved down toward the south along both shores.  In the late  summer they were caught in greater numbers at the west shore and north end than the east shore.  Thus changes in relative abundance suggests that many  of the fish which had migrated southward in the early and midsummer tended to move back to the northern and western parts of the lake. (d)  Redside shiner On July 18 the majority of the larvae were highly concentrated around  Station E/ (77% of the total).  In mid- and late-summer the curve became  polymodal rather than unimodal (Fig. 11), which suggests that the larvae  -41-  % Figure  W3 W2 W, N E, E2 S T A T O IN S  Percentage o f c a t c h o f n o r t h e r n i n d i c a t e d by b i w e e k l y h a u l s .  E3  E4  squawfish f r y a t 9 s t a t i o n s as  W4 W3 Vh W , N E, E2 S T A T O IN S Figure 10.  E3  E4  Percentage of catch of peamouth chub f r y at 9 stations as indicated by biweekly seine hauls.  -43-  W4 W3 W2 W, N E, E2 S T A T O IN S Figure 11.  E3  E4  Percentage of catch of redside shiner fry at 9 stations as indicated by biweekly seine hauls.  -44-  had dispersed along the shore in both directions. (e)  Prickly sculpin On July 3j 61$ of the total was seined at Station Vty.  were also obtained on August 1 and August IB (Fig. 12). curve takes a polymodal shape.  Similar results  On July 1 the  Station W^, E/ and E j yielded large numbers  of fry whereas no young of the year were caught at Station W^..  These  results suggest that i n the early summer they probably migrated in a northeast direction along the shore towards the head of the lake, and once there, began to move down along the east-shore towards the south.  In the mid-  summer they may have moved back on the same route in the opposite direction. Northcote and Hartman (1959) report that on July 17 and 18, 1958, a group of sculpins, probably yearling fish (26 - 39 mm. in fork length), was moving i n a northeast direction along the rocky shore situated between Station W3 and W4.  It would be possible that fry of the year (15 - 23 mm.  in fork length on the same data in I960 and 14 - 28 mm. in 1961) showed similar "migratory behaviour."  (f)  Summary of seasonal movement There i s a similar trend among these five species. Wherever the  larvae hatched, they moved towards the head of the lake in early summer. In the case of the sculpins, the larvae appeared to continue their migration along the shoreline until eventually they were moving along the east shore towards the foot of the lake.  The four cypriniform species more or  less diverged away from the head of the lake after arriving there. Wo factor which may have caused their northeastern migration has been detected. However, i t i s undoubtedly true that such movement towards the same part of the lake results i n interspecific association which may cause over-crowding.  S T A T O IN S Figure 12.  Percentage of catch of p r i c k l y sculpin f r y at 9 stations as indicated by biweekly seine hauls.  -46Crossman (1959) observed i n Paul Lake t h a t i n m i d - J u l y t h e s h i n e r f r y began t o move o f f s h o r e , so t h a t the d e n s i t y o f s h i n e r s c l o s e to shore was g r e a t l y reduced.  In Nicola  Lake such s e a s o n a l  o f f s h o r e movement was never  observed d u r i n g t h e summer, and s h i n e r s were always abundant near shore d u r i n g t h e daytime.  In mid- and late-summer the number o f chub f r y was  g r e a t l y reduced a t S t a t i o n N (see a l s o Table  7 on d i u r n a l movement).  However, i t i s u n l i k e l y t h a t t h i s r e d u c t i o n o f f r y was caused by a  seasonal  o f f s h o r e movement because a t t h e same time t h e i r numbers were i n c r e a s i n g a t some o t h e r  shore a r e a s o f t h e l a k e . P r o b a b l y s e a s o n a l movement a l o n g t h e  shore i s the p r i n c i p l e cause o f t h e r e d u c t i o n i n number o f chub a t S t a t i o n N.  M o r t a l i t y f a c t o r s would a l s o c o n t r i b u t e t o t h e r e d u c t i o n i n number but  they do n o t e x p l a i n t h e marked d e c r e a s e s r e l a t i v e t o o t h e r  shore  areas,  ( u n l e s s m o r t a l i t y i s g r e a t e s t near S t a t i o n N).  (3) Ali  D i u r n a l Movement and D i s t r i b u t i o n i n Inshore Water  (1959) notes t h a t f o u r c y p r i n i f o r m s p e c i e s i n N i c o l a Lake show  d i u r n a l onshore-offshore  movement a t t h e i r f i r s t  a l s o r e p o r t s t h a t i n Wyoming, young chub, G i l a  summer stage.  John (1959)  s t r a r i a , moved out beyond  one meter depth d u r i n g the n i g h t . The  c a t c h data  taken a t S t a t i o n N i n  I960 and 1961 i n d i c a t e t h a t f r y  o f a l l f o u r c y p r i n i f o r m s p e c i e s showed d i u r n a l o n s h o r e - o f f s h o r e  movement  throughout t h e summer ( T a b l e s 5. 6, 7, 8) a s was p r e v i o u s l y noted by A l i  (1959)stayed  They s t a r t e d to move i n t o the s h a l l o w water a t dawn (around t h e r e d u r i n g the daytime, and then moved out from t h e shallow  a t dusk (around  2000).  Midnight seining u s u a l l y resulted i n a  s m a l l e r number o f f r y b e i n g  caught.  s i g n i f i c a n t depth p r e f e r e n c e .  0400), water  considerably  A l l c y p r i n i f o r m s p e c i e s a l s o showed  The water c l o s e s t t o the edge o f t h e shore  -47T a b l e 5.  C a t c h d a t a o f sucker f r y s e i n e d a t S t a t i o n N. indicates  Each number  t h e t o t a l o f two r e p l i c a t e s i n t h e e a r l y and mid  summer, and mean o f t h r e e r e p l i c a t e s i n t h e l a t e  1600  2000  2400  0400  0800  1200  Total  1  121  79  0  0  130  823  1,153  2  1,002  522  11  124  1,391  414  3,464  Time**  3  1,644  655  95  1,288  1,463  1,004  6,149  Depth**  Total  2,767  1,256  106  1,412  2,984  2,241  Mean F. L.  16.1  16.1  15-9  16.0  16.1  16.2  Time  1600  2000  2400  0400  0800  1200  Total  F-test  1  2  2  3  0  0  8  15  2  14  25  36  37  10  34  156  3  18  153  45  95  41  37  389  Total  3-4  180  84  132  51  79  19.8  21.0  23.4  17.8  19.6  19.5  Time. I960  summer.  F-test  Depth  J u l y 12-13  Depth  July  30-31  Mean F. L .  **  S i g n i f i c a n t a t 1% l e v e l .  *  S i g n i f i c a n t a t 5% l e v e l .  Depth**  -48T a b l e 5«  Continued.  1600  2000  2400  O4OO  0800  1200  1  2  0  1  30  1  0  2  342  7  18  84  121  298  870  Time**  3  86  25  16  179  195  412  913  Depth**  430  32  35  283  317  710  Mean, F . L.  21.2  20.7  19.5  19.1  19.6  20.7  Time  1600  2000  O4OO  0800  1200  Total  1  1  10  0  3  6  5  25  2  19  44  12  75  56  92  298  Time**  3  6  20  8  30  23  4l  128  Depth**  26  74  20  108  85  138  Mean F. L .  23.7  21.5  26.1  23.1  23-3  20.8  Time  1600  2000  2400  1400  0800  1200  90  II4  20  47  84  62  30.9  33.5  33.0  33.5  27.0  31.2  Time  1961  July 13-H  Total  F-test  Depth  Total  2A00  . 34  Interaction*  F-test  Depth July  31-  Aug. 1  Total  Aug. 17-18 Mean Mean F. L .  F-test N. S.  -49Catch data o f squawfish f r y seined, a t S t a t i o n N .  Table 6.  Each number  i n d i c a t e s t h e t o t a l o f two r e p l i c a t e s i n t h e e a r l y and mid summer, and t h e mean o f t h r e e r e p l i c a t e s i n t h e l a t e  I960  July 12-13  1600  2000  2400  0400  0800  1200  Total  1  27  2  0  0  8  55  92  2  153  148  9  11  303  119  743  Time**  3  291  113  12  17  397  163  993  Depth**  Total  471  263  21  28  708  337  11.1  11.6  10.8  11.4  11.3  11.7  1600  2000  2400  0400  0800  1200  Total  1  2  0  0  39  7  12  60  2  1318  1  45  78  94  2396  3932  Time**  3  584  7  49  198  458  1778  3074  Depth**  Total  1904  8  94  315  559  4186  Mean F. L.  15.0  15-7  14-7  15-4  14.7  15.6  *\Jime Deptft-  1600  2000  2400  0400  0800  1200  Total  \^ime DeptTr-  Mean F. L.  1961  July 13-14  summer.  "<Cime Depth^  F-test  Inter**  F-test  Inter**  F-test  July 31-  1  6  0  0  0  2  3  11  Aug. 1  2  282  5  0  21  44  44  396  Time**  3  105  6  3  15  55  83  267  Depth**  Total  393  11  3  36  101  130  Mean F. L.  20.2  16.1  21.8  20.2  19.9  19.4  Time  1600  2000  2400  0400  0800  1200  F-test  260  15  0  12  25  72  Time**  28.1  28.6  27.9  29.6  28.5  Aug. 1718  Meanj. Mean F. L.  Inter**  -50-  Table 7.  Catch data of chub fry seined a t Station N. Each number indicates the total of two replicates in the early and mid summer, and mean of three replicates i n the late summer. 1600  2000  2400  0400  0800  1200  Total  1  17  1  0  0  1  36  55  2  18  14  1  5  8  8  54  Time**  3  37  10  6  12  28  22  115  Depth*  Total  72  25  7  17  37  66  15.6  15.9  16.8  16.8  15-2  15-9  1600  2000  2400  0400  0800  1200  Total  1  10  0  0  6  2  6  24  2  432  0  0  5  16  1188  1641  Time**  3  13  0  0  28  68  600  709  Depth**  455  0  0  39  86  1794  19.0  21.2  21.3  ""\T4me  I960  July 12-13  Depth"*--  Mean F. L.  1961  July 13-14  "^--Time DeptK^  Total  20.1  "\3irne  1600  2000  2400  0400  0800  1200  Total  1  0  0  0  0  0  0  0  July 31-  2  5  2  0  0  2  6  15  Aug. 1  3  3  0  0  0  0  9  12  Total  8  2  0  0  2  15  Mean F. L.  26.2  23.0  33-0  29.3  Time  1600  2000  2400  0400  0800  1200  Mean:  26  1  0  0  8  37-3  41.0  Aug. 17-18  Mean F. L.  42.5  39 42.4  F-test  Inter***  Mean F. L.  Deptfi^  F-test  F-test  N. S.  F-test Time**  -51Table 8. Catch data of shiner fry seined at Station N. Each number indicates the total of two replicates in early and mid summer, and mean of three replicates in the late summer.  1960  July 30-31  -~~~Iime Depth""-  1600 2000 2400 0400 0800  July 13-14  F-test  1  0  0  . 0  0  0  1  2  2  5  3  20  19  43  92 Time*  3  128  6  19  73  204  314  744 Depth**  Total  130  11  22  93  223  358  Mean 14.0 • F. L. 11.4  1961  1200 Total  •^-4^me Depth  1600  1  9.7 11.8 11.8 11.3  2000 2400 0400 0800 1200 Total  F-test  1  4  11  39  45  12  2  496  14  77  239  321  3  407  429  123  233 1001 II64  3357 Depth**  Total  907  454  239  517 1334 1951  Inter**  Mean F. L. ^Time Deptn*-  11.9 1600  8.6 10.3 11.5  5-<. 116 7,82  1929  Time**  9-6 10.7  2000 2400 0400- 0800 1200 Total  F-test  1  0  8  2  5  11  5  July 31-  2  90  102  0  270  90  26  578 Time**  Aug. 1  3  108  72  11  194  231  161  777 Depth**  Total  198  182  13  469  332  192  Inter**  Mean F. L.  19.5 13.5 12.1 17-5 18.9  20.6  Time  1600 2000 2400 Q400 0800  1200  F-test  22 1471 1244  Time**  Aug. 17-18  Mean":  621  4  Mean F. L.  26.6  20.1  0  27-1 24-9  23.9  31  -52-  with a depth of approximately 0 to 6 inches had a relatively lower density than the deeper water. A fair number of sucker fry were caught by midnight netting in midsummer, I960, and the mean fork length was significantly greater than that of those caught during the daytime (significant at 1% level by F-test). The same trend in size was also found in mid-summer, 1961. Young peamouth chub and northern squawfish seemed to move out to deeper water earlier than the suckers, and as the catch data in 1961 indicate, they were already almost absent from the shallow water by 2000 hours.  Chubs returned to the shore area later in the morning than the  others.  In other words they occupied this area for less time than the  other species. In the mid-summer, I960, and the early summer 1961, a fair number of fry were taken even at midnight.  Traps set at various distances from shore  at the same place as i n 1959 caught shiner fry both during the day and the night at the time in midsummer when fry were beginning to hatch.  Johannes  and Larkin (1961) report that in early summer shiner fry in Pinantan Lake were i n schools within 6 inches of the surface at 11:30 p.m.  Probably fry  of the earliest free swimming stage have different diurnal behaviour. In the sculpin, fluctuations in the numbers near shore have no direct correlation with time of day (Table 9 ) .  In July before the fry of other  species appeared they show the same depth preferences as the other species, but later on in the summer this i s not the case. The night distribution of a l l of the species i s not well known.  The  results of surface trawling undertaken in offshore waters on July 25, I960, indicate that they do not disperse to the offshore surface water at night. MacLeod (i960) reports that on August 5 - 6 ,  1959, dynamiting at the bottom  Table 9.  Catch data of sculpin fry seined at Station N. Each number indicates the total of two replicates i n the early and mid summer, and mean of three replicates i n the late summer. \Time  I960  July 12-13  1600  2000  2400  0400  0800  1200  Total F-test  DeptfN 1  0  5  13  0  3  1  23  2  96  66  105  83  72  461  Time**  3  23  24  123  129  110  39 30  439  Depth**  119  95  241  212  185  70  Mean F. L.  16.3  16.2  16.1  17.0  16.2  16.3  \Time  1600  2000  2400  0400  0800  1200  Total  Total F-test  Depth^ July 30-31  1961  July 13-14  1  3  143  23  22  24  3  218  2  19  67  23  40  31  271  3  10  91 18  47  10  47  19  151  Total Mean F. L.  32  252  137  55  111  53  23-0  23-7  24-1  22.6  22.5  22.2  \Time  1600  2000  2400  0400  0800  1200  Time**  Total F-test  Depth^ 6  1  0  1  58  53  13  2  48  29  139  55  57  ' 114  442  Time**  113  29  187  82  41  16  468  Depth**  161  59  384  190  104  136  Mean F. L.  20.7  21.9  19-4  21.7  20.7  21.5  \Time  1600  2000  2400  0400  0800  1200  Total  1  5  107  41  66  18  8  245  2  12  56  45  57  60  3  90  75  54  158  9 9  239  42  Total  58  253  161  167  276  26  Mean F. L.  20.3  22.6  22.8  22.9  22.1  22.6  Time  1600  2000  2400  0400  0800  1200  30  20  10  16  26.5  28.2  29.2  28.5  3 Total  131  F-test  Depth^ July 3 1 Aug. 1  Aug. 1 7 - 1 8Mean! Mean F. L.  15 29.5  11  27-7  428  N. S.  F-test Time*  -54250 f e e t from shore produced no young f i s h ,  but a t n i g h t a f t e r a b l a s t a t  the  same s t a t i o n , a number o f young-of-the-year chub were c o l l e c t e d  ing  on t h e s u r f a c e e i t h e r dead o r i n j u r e d .  fry  i n a q u a r i a i n d i c a t e t h a t a l l f o u r c y p r i n i f o r m s p e c i e s tend  the bottom l a y e r a t n i g h t w h i l e  Observations  float-  of b e h a v i o u r o f to stay i n  they occupy the t o p l a y e r d u r i n g the day  ( d e t a i l s w i l l be d i s c u s s e d i n f o l l o w i n g s e c t i o n ) .  These  observations  suggest t h a t a f t e r the o f f s h o r e movement they become w i d e l y d i s p e r s e d on the bottom o f the o f f s h o r e a r e a . D i u r n a l movement d i s c u s s e d above i s based on the data S t a t i o n N where the bottom i s sandy. observed a t bottom t y p e s  collected at  T h i s d i u r n a l b e h a v i o u r was a l s o  such a s weed beds and g r a v e l .  The c a t c h  data  o b v i o u s l y i n d i c a t e t h a t i n both weed beds and g r a v e l s young f i s h - were at  n i g h t w h i l e they were abundant d u r i n g t h e day ( T a b l e 1 0 ) .  concluded The  I t can be  t h a t bottom t y p e s do not modify t h e i r o n s h o r e - o f f s h o r e r e s u l t s o f s e i n e h a u l s taken a t 1300  scant  movement.  hours a t S t a t i o n N i n d i c a t e  t h a t t h e r e i s no s i g n i f i c a n t d i f f e r e n c e i n abundance o f l a r v a e i n the i n s h o r e area  t h a t c o u l d be a t t r i b u t e d to t h e wave c o n d i t i o n s encountered  d u r i n g t h e t h r e e p e r i o d s o f the summer when sampling o c c u r r e d variance a n a l y s i s ) .  ( t e s t e d by  However, waves more than 4 i n c h e s i n h e i g h t kept them  out o f t h e v e r y shallow water w i t h i n 10 f e e t o f shore and u s u a l l y l e s s  than  7 i n c h e s deep. Seine  h a u l s taken under d i f f e r e n t  cloud c o n d i t i o n s i n d i c a t e d t h a t f r y  o f a l l c y p r i n i f o r m s p e c i e s were more abundant near shore on t h e sunny days than on the cloudy days.  By c o n t r a s t , s c u l p i n f r y o c c u r r e d  near shore on the cloudy days ( t e s t e d by v a r i a n c e  analysis).  more f r e q u e n t l y  -55Table 10.  Catch data o f f r y o f the f i v e s p e c i e s seined a t t h r e e  different  bottom t y p e s by day and by n i g h t .  Sucker Date  Bottom Type  Rock & J u l y 27, G r a v e l I960  Day Night  Chub  Shiner  Sculpin  D.  N.  D.  N.  D.  N.  D.  N.  1060  15  27  5  16  0  1017  70  99  90  Reed  119  6  231  1  0  0  351  6  36  36  Sand  ,133  5  • 17  0  1  1  168  0  93  93  161  3  24  2  1  0  807  24  4  57  Reed  39  1  2  1  1  0  246  34  8  19  Sand  547  4  547  4  456  1  3520  2  17  76  Rock & Aug. 17, G r a v e l 1960  Squawfish  -56(/J Observations and  Vertical Distribution  o f b e h a v i o u r i n n a t u r e were f r e q u e n t y made a t S t a t i o n N  some o t h e r shore a r e a s i n t h e n o r t h e a s t e r n b a s i n d u r i n g t h e d a y t i m e ,  t h r o u g h o u t t h e summers o f 1959 and I 9 6 0 .  T h e i r b e h a v i o u r was a l s o  observed  i n aquaria. (a)  Field  observation  Largescale sucker.  I n e a r l y summer t h e f r y u s u a l l y o c c u r i n midwater  w i t h t h e tendency b e i n g f o r them t o be n e a r e r t h e s u r f a c e than t h e bottom. I n midsummer most o f them swim n e a r t h e bottom a l t h o u g h s m a l l s c h o o l s composed o f s m a l l e r i n d i v i d u a l s may o c c u r n e a r e r t h e s u r f a c e .  In l a t e  summer a l l s u c k e r f r y swim c l o s e t o t h e bottom and feed on t h e bottom w i t h t h e i r s u c k i n g mouth. S q u a w f i s h and peamouth chub.  I n e a r l y summer they a r e d i s t r i b u t e d i n  the same p a t t e r n as t h e young s u c k e r s .  I n m i d - and late-summer they  u s u a l l y occupy t h e m i d d l e and upper l a y e r s , and o n l y r a r e l y o c c u r n e a r t h e bottom. Redside s h i n e r .  T h e i r v e r t i c a l d i s t r i b u t i o n i s b a s i c a l l y n o t much  d i f f e r e n t from t h a t o f t h e o t h e r c y p r i n i d s p e c i e s . i t has been f r e q u e n t l y observed  I n l a t e summer, however,  t h a t t h e s h i n e r f r y tend t o s t a y i n t h e t o p  l a y e r and feed a t t h e s u r f a c e on s m a l l e g g - l a y i n g D i p t e r a and o c c a s i o n a l l y t h e y even a t t a c k c a d d i s f l y a d u l t s l a r g e r than Prickly sculpin.  themselves.  The s c u l p i n f r y swim around i n the bottom l a y e r o r  s t a y on t h e bottom, and they n e v e r come up t o t h e s u r f a c e l a y e r s d u r i n g t h e daytime.  Surface t r a w l i n g a t various inshore areas o f the northeastern  b a s i n u n d e r t a k e n d u r i n g t h e summer o f 1959 r e s u l t e d i n scant  catches  d u r i n g t h e daytime and r e l a t i v e l y l a r g e c a t c h e s a t m i d n i g h t . t h a t t h e y move up towards t h e m i d d l e and s u r f a c e l a y e r s d u r i n g  I t appears darkness.  -57-  (b)  Aquarium observation Table 11 shows results of recording v e r t i c a l d i s t r i b u t i o n i n aquaria  i n three periods; day (08C0, 1200, 1600 hours), dawn and dusk (0/+C0, 2000 hours) and night (2400 hours). t i o n a l pattern.  There: seem to be two trends i n d i s t r i b u -  One i s diurnal and the other i s seasonal.  Diurnally, f o r  a l l species, there were more i n the upper layer during daytime and more i n the bottom layer at midnight, dawn and dusk.  In late summer the squawfish  and shiner showed a tendency to reverse t h i s d i u r n a l d i s t r i b u t i o n a l pattern.  Traps set at various distances from shore at Station N i n the  late summer, 1959, also showed that there were some squawfish at midnight.  appearing  Probably fast growing i n d i v i d u a l s had changed t h e i r  from d i u r n a l to nocturnal (as for older f i s h ) .  behaviour  I t i s u n l i k e l y that the  shiners move up to the surface at night i n the l a t e summer i n nature, because catch data never indicated such behaviour  (see Section VI-3) and  also no l i t e r a t u r e has reported i t . It i s remarkable i n the sucker that percentages occupying the bottom layer increase with progress of season both i n day and night.  The rest of  the species do not c l e a r l y show such trend. The sculpin i s e n t i r e l y a bottom dweller i n late summer as the table shows.  As f a r as t h e i r behaviour during daytime i s concerned, f i e l d tions generally coincide with aquarium ones.  observa-  I t i s noticeable that i n  early summer a l l four cypiniform species show s i m i l a r v e r t i c a l d i s t r i b u t i o n , so that they have a good chance of i n t e r s p e c i f i c association, while the sculpin f r y can be the sole bottom dweller i n early summer.  In the  l a t e r season the sucker and sculpin gradually have more chance o f r e l a t i o n  -58-  T a b l e 11.  Percentage o f v e r t i c a l  d i s t r i b u t i o n o f f r y o f the f i v e  i n aquaria a t three d i f f e r e n t l i g h t  Date  Layer  24  24  16  J u l y 24, 25  Aug.  24  Dusk & Dawn  Night  37.8  Middle  23.4  42.8  31.8  13.1  36.6  19.5  Bottom  24.4  35.6  46.7  41.4  45.7  70.8  37.8  1.6  3.3  24.6  15.3  10.0  Middle  17.8  11.7  16.7  15.6  13.7  17.4  Bottom  44.4  86.7  80.0  56.0  71.0  72.6  15.6  1.7  0.0  26.7  Middle  13.3  5.0  3.3  20.5  16.6  20.0  Bottom  71.1  93.3  96.7  52.8  80.0  73.3  5 f i s h p e r aquarium (2 r e p l i c a t e s ) Layer  Day  Dusk & Dawn  Night  9.7  6.7  3.4  10 f i s h p e r aquarium (2 r e p l i c a t e s ) Day  Dusk St Dawn  Night  35.5  8.3  3-3  16.2  28.6  10.9  Middle  27.8  27.2  20.0  43.8  42.1  36.0  Bottom  46.7  65.O  76.7  39-6  35.4  46.9  Top  12.3  6.7  10.0  18.2  12.3  12.3  Middle  28.9  35.0  23.3  29.3  21.0  19-3  Bottom  58.9  58.3  66.7  52.5  66.4  68.3  Top  26.7  21.7  43.3  18.3  12.5  31.7  Middle  18.9  35-0  40.2  25-5  28.4  41-7  Bottom  54.4  43.3  24.3  56.1  59-2  26.7  Top J u l y 15, 16  Day  45.5  Squawfish.'  Date  Night  21.8,  Top Aug.  Dusk & Dawn  15.2  Top July  Day  10 f i s h p e r aquarium (2 r e p l i c a t e s )  52.2  Top July  conditions.  5 f i s h p e r aquarium (2 r e p l i c a t e s )  Sucker  species  - 5 9 -  T a b l e 11.  Continued.  5 Chub Date  Layer Top  f i s h p e r aquarium (2 r e p l i c a t e s ) Dusk & Dawn  Day  10  Night  Day  f i s h p e r aquarium (2 r e p l i c a t e s ) Dusk & Dawn  Night  34-4  25.0  10.0  43.3  35.9  10.0  J u l y 14, 1 6 Middle  13.3  30.0  20.0  28.3  23-3  18.3  Bottom  52.2  45.0  70.0  40.9  40.9  71.7  Top  15.5  15.0  0.0  14.2  14.2  13.3  Middle  47.8  28.4  16.7  21.7  21.7  26.7  Bottom  36.7  56.7  83-3  64.2  6 4 . 2  60.0  Aug.  24,  2 6  Shiner Date  Layer  Aug. 17, 22  Day  Aug. 16  Night  Day  Dusk Sc Dawn  Night  40.0  10.0  43.4  27.1  10.7  Middle  37.8  36.7  20.0  4 1 . 6  34-9  22.3  Bottom  8.7  23-3  70.0  14-9  38.1  67.0  Top  32.2  33.4  40.0  -49-3  45.9  55.0  Middle  46.7  35-5  46.7  28.7  30.9  33.3  Bottom  21.1  28.3  13-3  19.0  23.3  12.7  Sculpin Date  D.usk & Dawn  53.3  Top July 2 4 , 2 6  10 f i s h p e r aquarium (2 r e p l i c a t e s )  5 f i s h p e r aquarium (2 r e p l i c a t e s )  5 f i s h p e r aquarium Layer  Day  Dusk & Dawn  10 f i s h p e r aquarium  Night  Day  Dusk 8c Dawn  Night  Top  4-5  0.0  0.0  1.1  0.0  0 . 0  Middle  0.0  0.0  2.2  0.0  0.0  0.0  Bottom  95-5  100.0  97.8  98.9  100.0  100.0  -60-  with other species on the bottom.  The squawfish, chubs and shiners remain  in association a l l through the summer.  (5)  Habitat  Preference  It has been reported that young fish change habitat requirements with progress of developmental stages; by Miura (1955) in some marine species, by Gee (1961) i n two species of dace, by Crawford (1923) i n white sucker, and by Mizuno et a l . (1958) i n some cyprinids and gobies.  The young i n  Nicola Lake also show habitat preference. The 9 seining stations contained 3 different habitats; 3 sandy, 3 gravel and 3 weed beds.  The catch data at 9 stations were grouped into  three by nature of the habitats (Table 12). The suckers tended to be most abundant i n sand habitat though i t was not statistically significant i n mid-summer.  The chub and squawfish seem  to show the quite similar habitat preference; sand^weed, bed^ gravel i n early summer and weed bed^ sand ^gravel i n mid-summer (not significant i n chub).  Shiners were most abundant i n weed beds i n early summer, but in mid-  and late summer there was no significant difference. The sculpin prefers weed beds a l l through summer although i t was not significant on July .18 when the fry are supposed to be making movement along the shore (see VI-2 Seasonal movement). Although no species i s rigorously restricted to one habitat i t may be concluded from the viewpoint of relative habitat preference that l ) in early summer the sucker, chub and squawfish have the same demand for living site (or habitat), but not i n later parts of the season, 2) the squawfish has the same preference as the sculpin in mid summer and 3) at the time when shiners prefer weed bed the sculpins do not show specific  preference.  -61-  Table  12. Average catches of f r y of the five species at three different habitats.  Date  Sucker Squawfish Chub Shiner Sculpin  August 1, I960  July 18, I960  \Ra.bitat Species^  Each mean i s based on 6 seine hauls.  Sand  Sand Gravel and with rock weeds  August 15, I960  Gravel Sand and with weeds rock  Sand  Sand  Sand Gravel with and weeds sand  1,555  849  934  889  641  311  233  88  38  83  16  5  5  14  1  10  9  7  285  131  39  31  67  2  13  4  16  28  153  11  216  282  218  305  26  130  244  327  226  223  663  56  141  420  47  -62(6)  Interspecific Association  Various indices of interspecific association have been proposed by various biologists (Dice,,  1948;  Cole, 1949;  Fager, 1957  and Morishita,  1959).  Without exception these indices require that to measure degree of association i t i s necessary that at least some samples contain only some of the species.  Where almost a l l species occur in most samples, Fager  (1957)  sug-  gests that Kendall's rank correlation method can be applied to provide a measure of association.  The seining data taken from 9 stations were accord-  ingly analysed by this method. As two hauls were made at each station, 18 ranks exist in each season.  For test of significance Kendall's table  (1955)  was adopted. The results of application of Kendall's rank correlation coefficient are shown in Table 13 and diagramatically shown in Fig. 13.  In the early  summer a l l four cypriniform species are positively correlated with each other although the values o f f variation.  (rank correlation coefficient) show wide  The sculpin was correlated with the sucker and shiner.  In mid-  summer the squawfish, chub and shiner were positively correlated and the sucker was also associated with the squawfish and chub but not with the shiner.  The sculpin was associated with the shiner as in the early summer  and also had positive correlation with the chub. able changes occurred in the associations.  In the late summer remark-  There was no positive correla-  tion among them, but a negative one existed between the chub and sculpin. Fager  (1957)  suggests these alternatives i f there is significant pos-  itive correlation, (i)  The two species have a favourable effect on each other.  (ii)  They prefer the same conditions, and do not interfere with each other.  -63T a b l e 13.  V a l u e s o f rank c o r r e l a t i o n  coefficient, indicating  interspecific  association.  Early  summer ( J u l y 18, I960)  Species  Squawfish  Chub  Sucker  .648*  .737**  .587**  .368*  .806**  •433**  .225  .518**  .307  Squawfish  Shiner  Chub  Sculpin  .389*  Shiner  Mid summer (Aug. 1, i960) Species Sucker  Squawfish  Chub  Shiner  .405*  .500**  .219  .033  .754**  .397*  .288  .732**  .511**  Squawfish Chub  Sculpin  .612**  Shiner  L a t e summer (Aug. 15, i960) Species Sucker Squawfish  Squawfish  .190  Chub  Shiner  Sculpin  • 054  .070  .026  .163  .326  .021  .216  -.421*  Chub  .138  Shiner Significant  a t 1% l e v e l  Significant  a t 5% l e v e l  -64-  J U L Y  CHUB -SHINER  18  SUCKER  SCULPIN  CHUB AUGUST  I  NER  SOUAWFISF SUCKER  SCULPIN  CHUB \  AUGUST  is  SQUAWFISH SUCKER  F i g u r e 13.  \  \\  SHINER \  SCULPIN  POSITIVE CORRELATION  SIGNIFICANT  AT  \"4  L E V E L  POSITIVE CORRELATION  SIGNIFICANT  AT  5  LEVEL  NEGATIVE  SIGNIFICANT  AT  S%  CORRELATION  Diagrams showing i n t e r s p e c i f i c  association.  %  LEVEL  -65(iii)  I f t h e y have presumed p r e y - p r e d a t o r r e l a t i o n , the p r e d a t o r to congregate  (iv)  tends  i n those p l a c e s where i t s p r e y i s abundant.  I f t h e y have presumed h o s t - p a r a s i t e r e l a t i o n , the p a r a s i t e tends t o congregate  i n those p l a c e s where i t s host i s abundant.  There a r e n e i t h e r p r e y - p r e d a t o r r e l a t i o n s h i p n o r h o s t - p a r a s i t e r e l a t i o n s h i p among f r y o f these s p e c i e s , so t h a t ( i i i ) and ( i v ) can be excluded. No a g g r e s s i v e b e h a v i o u r has been observed among them under n a t u r a l cumstances.  cir-  S c h o o l s folined by s e v e r a l d i f f e r e n t s p e c i e s have been commonly  observed i n N i c o l a Lake, e s p e c i a l l y i n e a r l y summer. o b s e r v a t i o n s suggest t h e l i k e l i h o o d o f i n t e r s p e c i f i c  Although  these  s o c i a l a t t r a c t i o n , no  e v i d e n c e t o prove e x i s t e n c e o f a f a v o u r a b l e e f f e c t on each o t h e r has been obtained.  A t l e a s t , these o b s e r v a t i o n s suggest t h a t s o c i a l  interference  w i t h each o t h e r does n o t e x i s t a s a c o n t r o l l i n g factor o f d i s t r i b u t i o n . S i m i l a r i t y i n demand o r mode o f l i f e ,  Possibility  l i k e l y as t h e cause o f p o s i t i v e a s s o c i a t i o n . move toward  (ii),  seems most  In e a r l y summer a l l s p e c i e s  t h e n o r t h e a s t e r n end o f t h e l a k e and i t r e s u l t s i n a h i g h  concentration o f f r y i n the northeastern basin (see Section V I - 2 ) . Though f a c t o r s s t i m u l a t i n g t h i s movement a r e unknown, such c o n c e n t r a t i o n a t a c e r t a i n area may o c c u r a s a r e s u l t o f h a v i n g t h e same demand o r preference f o r l i v i n g  site.  D i u r n a l movements a l s o  the c y p r i n i f o r m s p e c i e s ( S e c t i o n V I - 3 ) ,  show s i m i l a r i t y among  which suggests t h a t t h e i r  pref-  erences o f e n v i r o n m e n t a l c o n d i t i o n s a r e s i m i l a r . O b s e r v a t i o n s o f h a b i t a t p r e f e r e n c e supports P o s s i b i l i t y  (ii).  In  e a r l y summer t h e sucker, squawfish and chub have the same p r e f e r e n c e f o r habitat  (see S e c t i o n  VI-5).  T h i s tendency  i s a s s o c i a t e d w i t h high"?; v a l u e s .  S i m i l a r l y , between t h e squawfish and chub h i g h "Z v a l u e s a r e o b t a i n e d i n midsummer when both o f them tend t o p r e f e r weed beds.  Divergence  i n habitat  -66preference i n late summer may be a factor causing absence of correlation. Vertical distribution should be considered together with association, for significant positive -£ value in a gross sample does not prove existence of very close association, i f two species in the same area occupy different depths of water.  Since a l l cypriniform species tend to stay in the middle  to top layer rather than i n the bottom layer in early summer, a significant "\ value may indicate association among them, while i nraid-summeri t does not indicate presence of association between the sucker and others because the suckers mostly stay in the bottom layer but others rarely stay in this layer.  The same argument i s possible for the sculpin which also occupies  the bottom.  Thus, the significant positive "X. values between the sculpin  and sucker or shiner in early summer, and between the sucker and squawfish or chub and between the sculpin and chub or shiner in the mid-summer should not be construed as sufficient evidence for very close association. Fager (1957) proposes that i f there i s significant negative correlation, (i)  The two species paired have an antagonistic effect on each other.  (ii)  They prefer different environmental conditions.  As described above, i t i s unlikely that antagonistic effects exist between the young of the species in Nicola Lake.  Therefore, negative correlation  seems likely to be based on Possibility ( i i ) , for the sculpin seems to prefer weedy habitat, while the chub does not prefer that habitat although i t i s not statistically significant.  VII.  (l)  FOOD HABITS  Development of Structures Related with Feeding  In young fish morphological as well as behavioral changes occur after absorption of the yolk sac. affecting actual feeding.  Such changes could be expected as a factor  As Fryer (.1959 a) shows among Cichlidae, morphol-  ogical characteristics may give an insight into the manner of feeding of a fish.  Comparison of feeding manner may be a powerful weapon i n detecting a  separation of feeding niches, i f two species are closely related i n mode of l i f e , even i f they eat the same type of food i n the same place at the same time. (a)  Largescale sucker The mouth of the postlarva (l6.0 mm. F. L.) i s terminal and slightly  oblique. growth.  As Fig. 1A-A shows, the mouth gradually migrates downward with The juvenile 41.0 mm. i n F. L. has a subterminal mouth that i s  well developed to feed on the bottom by sucking. also peculiar i n suckers.  The pharyngeal teeth are  Many fine teeth form a straight row.  The pharyn-  geal teeth of the juvenile of 30 mm. F. L. have a comb like shape which i s probably used for sorting out food from inorganic particles sucked from the bottom (Fig. 1/+-D).  The g i l l rakers are short and wide, and there are no  s l i t s between each rakers (Fig. 14-C), so i t i s unlikely that the g i l l rakers are functional i n sorting or f i l t e r i n g food particles. The ventral part of the body becomes f l a t , which may be adaptive to swim around close to the bottom and feed on benthic animals (Fig. 14-B). Such changes in structure suggest the necessity of gradual alteration from plankton to bottom feeding.  To analyze dietary change in post larval  -68Figure 14.  Morphological development of largescale sucker f r y . A. Lateral view of head. B. Frontal view of body. C. F i r s t g i l l . D. Pharyngeal teeth.  .-69and  j u v e n i l e s u c k e r s , f o u r l e n g t h c l a s s e s which corresponded  i n the development o f the d i g e s t i v e t r a c t simply c o i l e d and double were counted  ( s t r a i g h t , shape o f the l e t t e r  c o i l e d ) were s e p a r a t e l y examined.  i n the whole d i g e s t i v e  An i n s p e c t i o n o f Table 14  t o f o u r phases  A l l food  N,  items  tract.  r e v e a l s t h a t percentage  o c c u r r e n c e o f the  p e l a g i c group o f food items d e c r e a s e d p r o g r e s s i v e l y with changes i n ' morphology  such as mouth, pharyngeal t e e t h , and i n t e s t i n e .  The  rence o f b e n t h i c group o f food items c o r r e s p o n d i n g l y and increased.  R o t i f e r s and a l g a e were not counted.  percentage  progressively  These organisms  found i n s m a l l number i n the stomachs o f f r y s m a l l e r than 3 0 mm. r o t i f e r s were one  occur-  were although  o f the dominant groups o f animals i n the plankton  samples.  I f t h e y were e s t i m a t e d v o l u m e t r i c a l l y , the percentage would be l e s s than C.05/S o f the stomach c o n t e n t s . table. filled  Thus, these organisms  Among young l a r g e r than 3 0 mm.  were excluded i n the  i n l e n g t h 7 stomachs out o f 126  w i t h a l g a e t o g e t h e r w i t h s m a l l number o f r o t i f e r s and  were  benthic crusta-  ceans. A comparison  o f these data w i t h those presented by MacPhee  (i960)  for  f r y o f the same s p e c i e s from P a y e t t e R i v e r i n Idaho shows s e v e r a l marked differences. diatoms was  In the f i s h from P a y e t t e R i v e r the percentage o c c u r r e n c e o f much g r e a t e r than t h a t found  f o r the f i s h i n N i c o l a Lake.  F u r t h e r , i n the MacPhee's data f r y become a l g a e e a t e r s a t the s i z e range 16.0  -  30.0  mm.  23.5  mni' w h i l e i n N i c o l a Lake a l g a e do not appear u n t i l the f i s h  i n length.  those o f l a r g e s c a l e  These data from N i c o l a Lake r e v e a l s i m i l a r i t i e s  MacPhee  (i960)  s t a t e s t h a t a l t h o u g h diatom consumption was  are  to  s u c k e r s from Shuswap Lake and Okanagan Lake ( C a r l ,  which c o n t a i n e d h i g h percentages o f p e l a g i c c r u s t a c e a n and i n s e c t  of  1936)  larvae.  a s s o c i a t e d with  a change i n p o s i t i o n o f the jaws and an i n c r e a s e i n l e n g t h o f the i n t e s t i n e ,  -70-  Table 14.  Stomach contents of four different size groups of sucker fry. Numbers of individuals of each item are given as percentage of total individuals in a l l stomachs of given size range.  Year  1961  1959  Size  17.0  No. of stomachs Pelagic Cyclops Diaptomus  17.I** 2 3 . 1 ^ 30.1~ 30.0 23.0  17.0  14  24  29  17  25  41.3  1.5  15.0  2.1  26.0  4.1  13.3  .4  17.1~ 23.1~ 30.1/vx 30.0 23.0 195  141  11.6  1/4.9  12.5  3.0  23.3  20.3  17.7  9.9  11.6  14.0  8.8  13.0  1.7  .6  119  nauplius Daphnia  8.7  Simocephalus  1.0  Bosmina  2.9  2.6  11.9 s  Leptodora Water mite Chironomids popue Coryxid  •4 .8  .4  .4  •7  .4  .2  .1  •4  .5  •4  1.0  •4  1.9  1.0  Total  81.7  18.2  31.7  2.5  60.2  Benthic Harpacticus Chydorus  53-4  .1 16.3  66.6  Alona  21.2  33.3  38.1  38.8  5.6  70.1  2.7  4-3  10.5  13-5  AMPHIPODA  T 14.9  .1  11.8  .1  2.9  •4  14.1  37.8  epiphium  Chlronomid larvae  41.2  23-6  15.3  Stonefly larvae  15.1  8.9  T .1 9-7  33.6  T  •7  Coryxid Pelecipods Total  1.3 19.2  T : Traced<^0.05^  81.5  68.3  97.2  39.7  46.7  58.7  86.1  -71i n d i s c r i m i n a t e f e e d i n g on d e t r i t u s was n o t a s s o c i a t e d w i t h the r»sition o f the jaws b u t r a t h e r , w i t h t h e development o f the c o i l e d i n t e s t i n e .  Stewart  (1926) r e p o r t s i n the white sucker t h a t changing from t o p f e e d i n g t o bottom f e e d i n g o c c u r s i n a b r i e f p e r i o d , o n l y a few days i n d u r a t i o n , when t h e f i s h i s 16 t o 18 mm. l o n g . w i t h these  reports.  The data  from N i c o l a Lake o b v i o u s l y  A l t e r a t i o n i n f e e d i n g was n i c e l y a s s o c i a t e d w i t h t h e  p o s i t i o n o f t h e jaws and i t was a g r a d u a l process (b)  disagree  r a t h e r than sudden change,  N o r t h e r n squawfish The  mouth i s t e r m i n a l , s l i g h t l y o b l i q u e and r e l a t i v e l y l a r g e .  P o s i t i o n and shape o f the mouth i s not remarkably d i f f e r e n t i a t e d first  summer ( F i g . 15-A).  curved  The pharyngeal t e e t h a r e c o n i c a l ,  i n the  slightly  a t t h e t i p s , and 9 i n number i n a specimen l a r g e r t h a n 20.0 mm. i n  F. L. ( F i g . 15-D).  Probably  they a r e used i n b r e a k i n g up f o o d .  The g i l l -  r a k e r s a r e s h o r t and s p a r s e , and a r e a p p a r e n t l y n o n - f u n c t i o n a l i n s o r t i n g food  ( F i g . 15-C).  The body becomes s l i g h t l y compressed, and t h e v e n t r a l  p a r t does n o t become f l a t and  ( F i g . 15-B)  round body may not be a d a p t i v e  as i n the sucker.  The t e r m i n a l mouth  f o r s t a y i n g o r f e e d i n g on the bottom.  Table 15 shows t h a t percentage o c c u r r e n c e o f the p e l a g i c group o f food items i s f a r g r e a t e r than t h a t o f the b e n t h i c group, and t h a t o f the t e r r e s t r i a l group was n e g l i g i b l e .  The percentage occurrence o f Chydorus i n t h e  stomachs was h i g h e s t i n the b e n t h i c  group i n t h e e a r l y and mid summer.  A l t h o u g h Chydorus i s u s u a l l y c o n s i d e r e d a s a bottom organism, i n t h e shallow  water t h e y were a l s o found i n t h e p l a n k t o n  windy days ( s e e S e c t i o n IV-2). Chydorus without more e f f i c i e n t  samples e s p e c i a l l y on  I t may thus have been f e a s i b l e t o feed on  v i s i t i n g the bottom.  Such a f e e d i n g manner may indeed  than f e e d i n g on the a n i m a l on t h e bottom.  t i o n i s t r u e , the squawfish i s p r o p e r l y c a l l e d  If this  a t y p i c a l plankton  be  speculafeeder.  l2.OMM.FL.  20.0MM.  300MM. . 5 MM Figure 15.  .  Morphological development of northern squawfish f r y . Lateral view of head. B. Frontal view of body. C. f i r s t g i l l . D. Pharyngeal teeth.  -73Table 15. Stomach contents of three different size groups of squawfish fry. Numbers of individuals of each item are given as percentage of total individuals in a l l stomachs of given size range.  1961  1959  Year Size  ^\>15.0  No. of stomachs  38  23.0 19  23.1^ 20  15.1^  23.1^  85  153  118  1.1  24.3 1.8 .1  ^15.0  23.O  Pelagic  43.8£  Cyclops Dlaptomus nauplius  2.7 2.1  Daphnia Slmocepharus  2.7 7-5  Bosmina  1.4 37.4 71.0  2.8 36.1  11-5  13-7  Leptodora  9.7  44.0  Water mite  5.2  Chironomid pupae  5.2 .1  3.6  .6 .1  72.5  85.9  87-2  13-7 8.6 .8 1.4 1.9  1.3 •4 11.9 57.5 1.1 .2 2.4  T  •7  Coryxid Total  9.2  2.5  57.4  60.8  77.3  15-9  2.3  Benthic  .6  Harpacticus Chydorus  20.5  11.0  28.4 6.1  Alona  •7  epiphium AMPHIPODA Chironomid larvae Mayfly larvae  5-5  2.6  7.2  4.1  2.9  .1  5,0  12.4  14.3  12.5  •5 42.6  3-5 37.9  22.7  •7  Stonefly larvae Caddisfly larvae  .4  .6  Zygoptera larvae Water earth worm  26.7  Total Terrestrial Mayfly adults Total  T : Traced <J>. 05%  14.2  13.7  .1 .1  .1 .1  -74In a few fish.  cases  r o t i f e r s were found i n the stomachs o f the l a r g e r s i z e  of  However, i t i s supposed t h a t r o t i f e r s were taken i n c i d e n t a l l y r a t h e r  than as a food  r e q u i r e d by the  Cartwright of-the-year,  fish.  (1956) r e p o r t s t h a t squawfish under 12  feed on  " t e r r e s t r i a l i n s e c t s " , ( i n which has  midges, m a y f l i e s , c a d d i s f l y , and miscellaneous  i n c l u d i n g youngbeen i n c l u d e d  a l l t h e i r l a r v a e ) , plankton,  items i n that order o f preference.  N i c o l a Lake feed on  cm.,  planktonic crustaceans  The  fish,  and  young-of-the-year i n  i n h i g h p e r c e n t a g e , but none on  f i s h and almost none on a d u l t t e r r e s t r i a l i n s e c t s .  There may  have been d i f -  f e r e n c e s i n food h a b i t between the young-of-the-year and y e a r l i n g s , (c)  Peamouth chub. Morphological  northern  development o f the  squawfish.  The mouth i s t e r m i n a l and  s m a l l e r than t h a t o f the c o n i c a l and i n F. L.  hooked, and  ( F i g . 16-D).  speculated  The  is  pharyngeal teeth are  7 t e e t h a r e developed i n young l a r g e r than 20.0 g i l l - r a k e r s a r e s h o r t , wide and  s l i t s a t the l a t e r stage  stand  ( F i g . 16-C).  side  consequently  shape as i s common among p e l a g i c f a s t  swimmers ( F i g . 16-B).  o g i c a l c h a r a c t e r i s t i c s may  be a d a p t i v e  mm. by  I t could  t h a t the g i l l - r a k e r s are f u n c t i o n a l i n f e e d i n g .  body becomes s l i g h t l y compressed, and  bottom  the  s l i g h t l y o b l i q u e and  squawfish ( F i g . 16-A).  The  s i d e compactly without h a r d l y be  chub i s s i m i l a r t o t h a t o f  forms a t y p i c a l  The  spindle  These morphol-  f o r f e e d i n g on p l a n k t o n  r a t h e r than  animals.  As T a b l e 16 i n d i c a t e s , p l a n k t o n i c c r u s t a c e a n s high frequency  ( o v e r 90$  throughout summer).  s i m i l a r f i n d i n g s ; t h a t the food  were found i n e x t r e m e l y  Clemens et a l . (1939) r e p o r t  of the v e r y young f i s h i n Okanagan Lake  c o n s i s t s c h i e f l y o f water f l e a s , but a l s o of copepods, watermites, midge l a r v a e , s m a l l a q u a t i c and  terrestrial insects.  small  20.0MM.  38.0 MM. Figure 16.  Morphological development of peamouth chub f r y . k. L a t e r a l view of head. 3. Frontal view of body. C. F i r s t g i l l . D. Pharyngeal teeth.  -76Stomach c o n t e n t s o f t h r e e d i f f e r e n t s i z e groups o f peamouth chub  Table 16.  fry. of  Numbers o f i n d i v i d u a l s o f each i t e m a r e g i v e n as percentage  t o t a l i n d i v i d u a l s i n a l l stomachs o f g i v e n s i z e range.  Year Size  1961  1959 /vl8.0  range  No. o f  stomachs  20  18.0^25-0  25.1*v 30  17  •vlB.O  18.0^25.0  25.1~  10  101  65  13-6  21.6  4-1  47-3  17.8  1.6  Pelagic Cyclops  31.3  Dia ptomus  28.5  •4  •4  1.3  2.8  nauplius  •7  20.1  Daphnia Simocepharus Bosmina  9-7  23.6  3-4  85.6  •7  Leptodora  8.9  35-0  86.4  80.1 10.7  2.7  .1  10.9  13-3  2.6  .1  Water m i t e 1.1  Chironomid pupae Total  93-1  97-3  4.2  1.3  •4 90.6  98.1  2.7  .6  91-3  99.7  Benthic Chydorus Alona  .9 3-4  •9  epiphium Chironomid l a r v a e  1.4  Stonefly larvae Zygoptera  larvae  Total  1-3  1.0  1.0  T  .2  T  2.9  T  4.0  .2  8.1  .2  .2 1.4 7.0  2.8  4-4  1.8  Terrestrial Mayfly adults  3-9  Caddis a d u l t s  1.0  Total  4-9 T : Traced ^0.05$  .8  .8  -77I t i s reasonable first and (d)  summer, and  to conclude t h a t the chub i s a p l a n k t o n f e e d e r i n the  shows a s s o c i a t e d m o r p h o l o g i c a l a d a p t a t i o n o f the mouth  body shape, Redside  shiner  The mouth i s t e r m i n a l and markedly o b l i q u e ( F i g . 17-A). g e a l t e e t h a r e sharp and than 18 mm.  slightly  i n F. L., 7 t e e t h were counted.  become sharp, l i k e a needle spaced  hooked ( F i g . 17-D).  ( F i g . 17-C).  larger  rakers  stand s i d e by s i d e w i d e l y  r a k e r s a r e not f u n c t i o n a l i n f e e d i n g .  The body becomes markedly compressed, which may ing  pharyn-  In the f i s h  Short c o n i c a l g i l l  but not so l o n g , and  Probably the g i l l  The  be e f f i c i e n t  f o r quick t u r n -  ( F i g . 17-B). Marked y e a r l y d i f f e r e n c e i n foods was  the f i s h l a r g e r than 13.1  mm.  the f i s h l a r g e r than 13.0  shows t h a t insect  w h i l e a l l s i z e groups f e d on the p e l a g i c  i n 1961. mm.  Table 17  d i d not take p e l a g i c c r u s t a c e a n s but  a d u l t s i n a g r e a t number i n 1959, group t o a h i g h percentage  discovered.  Although  percentage  o c c u r r e n c e was  fed on i n s e c t a d u l t s i n 1961,  shows t h a t t h e i r p r e f e r e n c e f o r the t e r r e s t r i a l  low,  which a p p a r e n t l y  group p r o g r e s s i v e l y  i n c r e a s e s as t h e i r c a p a c i t y f o r c a t c h i n g them. Clemens  (1939)  r e p o r t s i n the f i s h i n Okanagan Lake t h a t the food o f  i n d i v i d u a l s l e s s than 35  mm.  i n l e n g t h c o n s i s t e d l a r g e l y o f copepods w i t h  c o n s i d e r a b l e numbers o f w a t e r - f l e a s and midge l a r v a e ; o t h e r a q u a t i c i n s e c t s and  diatoms ^ o c c u r r e d . t o some e x t e n t .  s u b s i s t on diatoms,  Lindsey  (1953) notes  that shiner f r y  copepods, o s t r a c o d s , and o t h e r s m a l l p l a n k t o n  organisms.  These r e p o r t s as w e l l as present f i n d i n g s i n N i c o l a Lake suggest t h a t s h i n e r f r y have the a b i l i t y to consume a c i n s i d e r a b l e v a r i e t y of food organisms. ganisms.  T h e i r d i e t s may  be e a s i l y a f f e c t e d by abundance o f food o r -  Figure 17.  Morphological development of redside shiner f r y . A. L a t e r a l view of head. B. Frontal view of body. C. F i r s t g i l l . D. Pharyngeal teeth.  -79-  Table 17.  Stomach contents of three different size groups of redside shiner fry. Numbers of individuals of each item are given as percentage of total individuals in a l l stomachs of given size range.  Year  1961  1959  Size  13.0  No. of stomachs  16  13.1~20.0 4  20.  30  W  ^13.0 72  .13.1~20.0 287  20:  W  43  Pelagic Cyclops  5-3  .1  2.0  3.0  Diaptomus  4.0  1.0  .2  .4  74-7  70.9  68.1  1.1  2.7  .9  •4  28.4  nauplius Daphnia Simocepharus  2.4  Bosmina  1.3  2.3  Water mite  1.2  .8  1.4  2.0  .8  4-9  24.7  Chironomid pupae  37-5  Coryxid Total  7-3  .1  3-7 89.2  37-5  11.0  •9  76.8  78.0  6.0  2.6  62.0  Benthic Chydorus  1-3  Alona  .1  epiphium  .1  Amphipoda  .2  Chironomid larvae  2.7  25-0  Mayfly larvae Stonefly larvae  20.7  14.6  16.6  1.2 8.0  2.7  Caddisfly larvae  1.2  Zygoptera larvae Total  14.7  6.8  10.7  25.0  23.1  37-5  62.2  23.3  .1  •4  .1  .6  17.9  24.4  4-2  13.7  4.2  13-7  Terrestrial Chironomid adults Caddis adults Total  2.4 37-5  64.6  -80(e)  Prickly sculpin The mouth of the postlarva i s terminal and oblique.  The position of  the mouth gradually becomes horizontal ventrally (Fig. 18-A, with 32.0 mm.  B).  F. L. has a perfectly horizontal and ventral mouth.  The young The  postlarva has a few spiny teeth on the maxilla and jugal bone, but no teeth developed on the anterior end of the vomer. become more numerous (Fig. 18-D,  E, F).  These teeth subsequently  The larvae 18.0 mm. in length and  larger have a few knob-like g i l l rakers covered with spines (Fig. 18-C). Both the upper and lower pharyngeal teeth are covered with many small conical teeth with slightly hooked sharp tips.  The round body at the post  larval stage gradually becomes dorso-ventrally depressed. of fish 32 mm.  The body shape  in length i s triangular in aross section with a wide ventral  flat surface that i s presumably adaptive staying on the bottom. The large mouth may be advantageous for catching larger animals than the other species do, as was shown in two species of sculpins by Northcote (1954),  ing  and the spiny teeth and g i l l rakers may be advantageous for catch-  and holding active prey animals.  The well differentiated pharyngeal  teeth are apparently used in breaking up food, as i s also the muscular stomach which i s definitely recognizable in fish larger than 18.0 mm.  The  horizontal mouth may not be suitable for feeding on bottom animals partly or wholly in bottom substratum and which can probably be taken by young suckers. Table 18 clearly shows that not only were the pelagic group such as Cyclops, Dia ptomus, and Da phnia important food items, but also chironomid larvae were observed in high percentage in the stomachs of a l l sizes of the sculpin fry.  These findings agree with Clemens (1939) who reports that the  food of small individuals of the same species in Okanagan Lake consisted of  E  I2.0MM. F.L.  fir IJi  • 2 MM  I MM  **i  •Q-5MM -Q-5 M M i  I8.0MM.  32.QMM. \-X/-- •:• ••' : .-i.•••••• V  . 4 MM  Figure 18.  i 2 MM . , 1MM..Q5MM , MM Morphological development of p r i c k l y sculpin f r y . A. Lateral view of head. B. Frontal view of body. C. F i r s t g i l l . D. Upper pharyngeal teeth. E. Lower pharyngealtteeth. F. Maxilla, jugar and vomer teeth. ,  3  -82-  Table 18.  Stomach contents of three different size groups of prickly sculpin fry. Numbers of individuals of each item are given as percentage of total individuals in a l l stomachs of given size range.  Year Size No. of stomachs  I960  A/15.0 72  15.1^5.0  25.0^  ssy 15.0  285  43  18  50.3  19.7  38.2  42;9  Diaptomus  2.8  46.5  12.7  Daphnia  7.9  2.7  2.1  Bosmina  .8  .1  Leptodora  •5  •4  Water mite  •3  1961 15.1*^25.0 25.CW 261  179  Pelagic Cyclops  Chironomid pupae Total  2.6  65.2  .2 69.6  20.4  5-9  2.6  8.5  59.5  5-2  3.0  1-5  .9  .1 .1  5-3  •9 59.2  50.7  .1  1.2  .6  34.2  77.6  Benthic Harpacticus Chydorus  •3  Alona  .8  .1  Amphipoda  •3  .8  1-3  .6  2.6  1.6  .2  7.3  8.0  1-5  Ostracoda Chironomid larvae Mayfly larvae stonefly larvae  .1 23.0  •5  29.4 •4  35.9  45.5  2.9  56.O  23.6  .1  .2  9.9  Zygoptera larvae Total  •3  .1  34-5  Terrestrial Chironomid adults  •3  Total  •3  30.7  •3  40.9  49.4  65.8  32.3  -83copepods, water f l e a e and midge l a r v a e , but do n o t agree w i t h B a i l e y ' s record  (1952) i n a d i f f e r e n t  s p e c i e s , Cottus b a i r d e p u n c t u l a t u s i n South-  western Montana, the l a r v a l i n d i v i d u a l s o f which f e d over 90$ on chironomid larvae. Though t h e young s c u l p i n i s a bottom d w e l l e r (see S e c t i o n VI-4), f i n d i n g s d e f i n i t e l y show h i g h consumption o f t h e p l a n k t o n ! c items.  This f a c t  group o f food  c o u l d be e a s i l y deduced from t h e m o r p h o l o g i c a l  a c t e r i s t i c s o f t h e mouth.  Probably  these  char-  t h e p l a n k t e r s a r e consumed whenever  t h e y come near t h e bottom d w e l l i n g s c u l p i n s .  (2)  I n t e r s p e c i f i c Overlapping  o f Stomach Contents  As was d i s c u s s e d i n t h e p r e v i o u s s e c t i o n , some s p e c i e s show marked changes i n food h a b i t which a r e c o r r e l a t e d w i t h growth i n t h e i r summer o f l i f e and some do not.  Combinations o f the s p e c i e s i n the l a t e  summer w i l l thus not i n v o l v e s i m i l a r foods on f e e d i n g h a b i t s . s p e c i e s t h a t change d i e t from p l a n k t o n t o bottom a n i m a l s  expected first  among them.  Therefore,  But even  as w e l l a s the  r e s t o f the s p e c i e s , a r e d e f i n i t e l y c l a s s i f i a b l e as p l a n k t o n e a r l i e s t f r e e l i v i n g stages.  first  f e e d e r s a t the  c l o s e food r e l a t i o n s h i p may be  However, t h e r e i s a s l i g h t d i f f e r e n c e i n the time o f  appearence o f the d i f f e r e n t  s p e c i e s ( S e c t i o n V I - l ) which may a l s o  l e s s e n t h e time d u r i n g which they o c c u r t o g e t h e r a t t h e same developmental stage.  F o r i n s t a n c e , the s h i n e r p o s t l a r v a e have l i t t l e  postlarvae o f other  species.  Table 19 shows percentage o c c u r r e n c e s of  chance o f meeting  o f food items i n the stomachs  the f i v e s p e c i e s sampled a t the same time a t S t a t i o n N.  apparently overlapped  i n a q u a l i t a t i v e sense.  Stomach  contents  As an i n d i c a t o r showing t h e  q u a n t i t a t i v e degree o f o v e r l a p p i n g o f stomach c o n t e n t s between s p e c i e s ,  -84Table 19.  Percent  occurence  o f stomach c o n t e n t s o f f r y o f f i v e  i n the three d i f f e r e n t  seasons.  Numbers o f i n d i v i d u a l s o f  each i t e m a r e g i v e n a s percentage stomachs o f f r y i n d i f f e r e n t Sea son Species No. o f stomachs Mean Length Pelagic Cyclops D i a ptomus nauplius Daphnia Simocepharus Bosmina Leptodora Water mite Chironomid pupae Coryxid Total  of total individuals i n a l l  seasons.  E a r l y Summer I960 E a r l y Summer 1961 SquawSquawSculSculSucker f i s h Chub p i n Sucker f i s h Chub S h i n e r pin 180 120 180 180 160 262 158 308 251 20.2 10.8 15.8 15-6 21.4 20.7 11.5 15-7 16.4  36.6  18.0  24-0  5-8  1.6  2.7 .1 3-5  3-8  .1  28.8  22.1 .8 •4 1.5  10.6  66.1 30.1  54.2  2.8 25-9  53-5  2.2 .2 .2  t15  5  57-1  Benthic Harpacticus Chydorus .1 •9 .2 Alona .1 .7 •3 epiphium Amphipoda Ostracoda 39.0 Chironomid l a r v a e 4.9 6.7 10.9 .1 .1 Mayfly larvae Stonefly larvae 26.1* 62.6* 25.9* 2.9* Caddis f l y l a r v a e Zygoptera l a r v a e Total 32.6 42.1 69-9 36.9 Terrestrial Chironomid a d u l t s Mayfly adults Caddis a d u l t s Total  species  1-3 2.3 22.6 18.8 14.4 .1 •7 4-9 .1 .7 •7 •4 1.8 1.4 .1 50.1 48.9  13.3 14.8 •5  50.9 .1 11.5 T 2.4 93-5  30.9  .1  .1  10.2  1.1  17.9  •9 •3 2.0  2.8  .1  49.0  19-3 7.8 7.1  .7 .2 .4 1.1 83.1  .1  •3 35-1 3.5  .2 .6 79.6 .5  y: 9  11.4  .7 35.1  .2 .1 1.6 3.7 .1 58.8 •4  1.3  50.3  T 5.0  16.7  1.3  .2  8.8  •4 .1  •3  .6  1.0  1-3  .2  8.8  •5  •3  .6  1.0  64.9  T : Traced<0.05$ *  These s t o n e f l y l a r v a e a r e v e r y s m a l l and supposed to be i n d i v i d u a l s h o r t l y a f t e r h a t c h i n g with p l a n k t o n i c l i f e .  -85T a b l e 19.  Continued.  Mid  Season  summer 1961  Late summer 1961  Suc- SquawSculker fish Chub Shiner pin No. o f stomachs 166 16 158 127 84 Mean Length 22.0 20.1 28.3 18.3 21.9 Pela g i c Cyclops 16.6 36.1 35*1 6.9 23-7 Diaptomus 1.0 1.0 2.9 nauplius .7 1.4 Daphnia 7-8 61.9 17-4 •4 Simocepharus 1.0 2.2 8.7 Bosmina 1.6 13-4 .1 4-0 Leptodora 1.0 .2 .1 Water m i t e .6 .1 •7 3-4 Chironomid pupae 2.0 1.6 1.9 18.5 . coryxid .2 Total 25-5 70.2 99.1 53-6 24-8 Species  Benthic Harpacticus Chydorus Alona epiphium Amphipoda Ostracoda Chironomid larvae Mayfly larvae stonefly larvae Caddisfly larvae Zygoptera larvae Total Terrestrial Chironomid adult Mayfly adults - Caddis a d u l t s Stonefly adult Total  .9 47.6  13.0  10.2  .8  7.1  .1  12.6  .2  11.6  .1  .1  3-2 .2 6.1 •3  27.0  1.9 2.2  Suc- SquawSculker- f i s h Chub Shiner pin ISO 152 58 119 179 33-1 29.2 41.6 26.3 28.6 2.2  15-9 T  .2 •7 12.5 62.5  .1 •5 84-3  •3 19.3  •4 41.7 9.2  4.8 72.5  20.6  .1  14.1  •3 1.1  1.1  •4 1.4 •3 2,2 79-8  .9 1.2  11.4 •3  .1  5-2  57.8 •4  29.0  12.1 .1  •3  3-7 1.5  • 4 30.3 1.5 99.7 40.1  .1 .1 T  .6 78.0  •4 .1 •4 7.4  •1  21.3  14-5 .1  .2  .4 74-4  29.0  .9  37.2  74.0  70.4  19-5  9.1  .2  .1  .3  T •5  .2  9.4  .1  T : Traced <(o. 05$  T .7  •3  21.5  I8.4  18.4  22.1  -86rank c o r r e l a t i o n c o e f f i c i e n t s were c a l c u l a t e d .  Table 20 g i v e s the c o e f f i -  cent v a l u e s , and F i g . 19 d i a g r a m a t i c a l l y shows i n t e r s p e c i f i c and  i t s seasonal succession.  correlation  Here, s i g n i f i c a n t c o r r e l a t i o n means t h a t t h e  o r d e r s o f food items taken by two s p e c i e s have a s i m i l a r tendency t o each o t h e r and t h e h i g h e r t h e c o e f f i c i e n t p o s i t i v e l y (range — 1 t o + l ) , t h e c l o s e r the tendency to agreement. A s e a s o n a l comparison o f these data  shows s e v e r a l marked d i f f e r e n c e s .  F o r t h e e a r l y summer o f I960, when a l l f r y o f t h e s p e c i e s were s m a l l e s t i n s i z e t h e c o r r e l a t i o n c o e f f i c i e n t s have s i g n i f i c a n t p o s i t i v e v a l u e s and t h e v a l u e s among t h e sucker,  squawfish and chub a r e remarkable h i g h .  For the  e a r l y summer o f 1961 when these f i s h were l a r g e r i n s i z e than I960, most c o e f f i c e n t s a r e p o s i t i v e l y s i g n i f i c a n t but the v a l u e s a r e s m a l l e r . summer, 1961, t h e c o e f f i c i e n t s i n combinations and  o f t h e squawfish and chub take  summer o n l y t h e squawfish  I n mid-  o f the sucker and squawfish  s i g n i f i c a n t p o s i t i v e value.  and chub were s i g n i f i c a n t l y  In the l a t e -  correlated i n a small  value o f the c o e f f i c e n t . T h i s s e a s o n a l change i n rank c o r r e l a t i o n c o e f f i c i e n t s suggests  that i n  e a r l y summer t h e foods taken a r e s i m i l a r i n k i n d and p r o p o r t i o n but t h e y g r a d u a l l y d i v e r g e i n t h e l a t e r p a r t o f t h e season. Lindstrom's  N i l s s o n (1958) c i t e s  r e p o r t (1955) t h a t the f r y o f three d i f f e r e n t w h i t e f i s h - s p e c i e s  i n the l a k e s Uddjaur and Storavan  consumed almost  the same food  (mostly  Bosmina) and s p e c u l a t e s t h a t t h i s f i n d i n g may i n d i c a t e t h a t t h e b e h a v i o u r mechanism i n v o l v i n g a c h o i c e o f f o o d ( t h e b a s i s f o r t h e f o r m a t i o n o f food n i c h e s ) i s n o t f u l l y developed size.  b e f o r e the f i s h has reached  T h i s s p e c u l a t i o n may be accepted  f o r t h e f r y o f N i c o l a Lake, s i n c e  i n t e r s p e c i f i c s i m i l a r i t y and n o n - d i f f e r e n t i a t i o n i s found behaviour  but a l s o i n m o r p h o l o g i c a l  a considerable  not only i n t h e i r  f e a t u r e s o f t h e i r mouth i n t h e e a r l i e s t  -87Table 20.  Values o f rank c o r r e l a t i o n c o e f f i c i e n t , i n d i c a t i n g i n t e r s p e c i f i c o v e r l a p p i n g of stomach c o n t e n t s .  I960 Early  summer  mean F. L.  sucker  15.8 mm.  squawfi sh  11.5  chub  15.7 16. 4  sculpin  sticker  squawfish  •895**  chub  sculpin  .748** ,641**  .400* .416* .607**  1961 Early  summer  mean F. L.  sucker  20.2  squawfish  15.6  chub  21.4  shiner  10.8  sculpin  20.7  Mid  summer  22.0  squawfish  20.1  chub  28.3  shiner  18.3  sculpin  21.9  Late summer  mm.  33.1  squawfish  29.2  chub  41.6  shiner  26.3  sculpin  28.6  sucker  mm.  , shiner  sculpin  -369*  .069  .237*  .381*  .496**  .067  .020  .355*  squawfish .392*  chub  shiner  .010  .092  .142  • 431*  .270  .074  .184  -.233  sculpin  .047  mean F. L.  sucker  535**  chub  .174  mean F. L.  sucker  sucker ...squawfish  mm.  sucker  squawfi sh .085  **  S i g n i f i c a n t a t 1% l e v e l  *  S i g n i f i c a n t a t 5% l e v e l  chub  shiner  .156  -.133  .032  .199  .141  .013  -.040 .000  .178*  sculpin  EARLY  SUMMER,V 1960 SIGNIFICANT _  I  _  ATI% LEVEL  Q S U A W H S F f  SIGNIFICANT  S U C K E R  S C U L P N I  AT  EARLY SUMMER, 1961  C H U B Q S U A W H S F I  \7\ - f  V — S H N I E R  S U C K E R MID  S C U L P N I  SUMMER  C H U B Q S U A W H S F I S U C K E R LATE  S H N I E R S C U L P N I  SUMMER  C H U B Q S U A W H S F I S U C K E R  S H N I E R S C U L P N I  Figure 19. Diagrams showing interspecific overlapping of stomach contents.  LEVE  -89stages. The squawfish and chub have a close food relationship throughout the summer.  In other words these two species demand the same or similar  organisms as food i n t h e i r f i r s t summer l i f e , while i n late summer the sucker, shiner and sculpin demand d i f f e r e n t organisms o r a t least the same organisms i n d i f f e r e n t proportion from each other and from the chub and squawfish.  (3)  Relation between Stomach Contents and Net-plankton  A comparison of the organisms i n the stomachs with those i n netplankton may give us not only an idea of t h e i r s e l e c t i v i t y i n feeding but also of whether they consume the animals from same or d i f f e r e n t resources. A modification of usual s t a t i s t i c a l techniques may be appropriate i n t e s t i n g the p a r t i c u l a r kind of hypothesis that i s treated here. I f the f i s h select foods i n the same order as they occur naturally then the rank correlation c o e f f i c i e n t w i l l b e - r l .  I f the f i s h take the  foods at random then the correlation w i l l s t i l l be large and positive, f o r the  obvious reason that i n a random sample (the f i s h stomach) the order of  foods w i l l be the same as the order i n the plankton from which the sample i s drawn.  A correlation of 0 may r e f l e c t therefore a marked s e l e c t i v i t y of  foods, and a correlation o f — 1 an astonishing s e l e c t i v i t y . Evidently significance, as measured from the base o f 0 i s meaningless i n these circumstances.  The appropriate technique i s to measure the  probability that any sample departs from the given order i n the plankton sample.  Obviously t h i s i s the probability o f observing a correlation  coefficient r = r  s  when the expectation i s r = l .  According to Kendall (1955)  the problem i s o f a recent nature as f a r as theory of s t a t i s t i c s i s con-  -90cerned  but he r e f e r s to the work o f B r a d l y and T e r r y (1952) and  (1954) on  a  Bradly  related subject.  Where r«L, i t suggests t h a t e i t h e r the f i s h take the foods a t random o r the o r d e r o f foods i n the f i s h the p l a n k t o n .  stomach w i l l be t h e same as the o r d e r i n  Where r i s s m a l l , i t suggests d e p a r t u r e  i n the stomach from t h a t i n the p l a n k t o n , f i s h may be o c c u r r i n g .  o f the o r d e r o f food  and then s e l e c t i v e f e e d i n g by the  Where r i s v e r y s m a l l , i t suggests t h a t the f i s h  s e l e c t i v e l y feed on t h e animals o f v e r y low rank and than c o m p e t i t i o n f o r the food  r e s o u r c e may  be o c c u r r i n g .  The r a t i o o f t h e v a r i o u s k i n d o f p l a n k t e r s may fish.  r e f l e c t g r a z i n g by t h e  T h i s s o r t o f r e f l e c t i o n w i l l be tremendous i f r e s o u r c e s o f p l a n k t e r s  a r e l i m i t e d and a l s o immediate s u p p l y o f those  can not be expected, as was  observed i n the i n s h o r e a r e a o f N i c o l a Lake (see f o l l o w i n g s e c t i o n ) . such c i r c u m s t a n c e ,  t h e B r a d l e y and T e r r y ' s technique  to  may have dubious a p p l i c a t i o n to the d a t a .  t h e i r technique  (4)  D i u r n a l Rhythm o f Feeding  o r even o t h e r s  Under similar  Activity  S e i n i n g a t S t a t i o n N as w e l l as o b s e r v a t i o n o f b e h a v i o u r o f f i s h i n a q u a r i a i n d i c a t e d t h a t f o u r c y p r i n i f o r m s p e c i e s move i n t o the shallow water and  a r e a c t i v e d u r i n g the d a y l i g h t hours, while  they move out and  probably  s t a y on the bottom o f f s h o r e i n i n a c t i v e c o n d i t i o n a t n i g h t (see S e c t i o n VI4).  The d i u r n a l f e e d i n g t r e n d based on f l u c t u a t i o n i n number o f animals i n  the d i g e s t i v e t r a c t s o f these of  s p e c i e s seems t o correspond  with t h i s  pattern  activity. F i g s . 20 - 24 shows the d i u r n a l f l u c t u a t i o n i n numbers o f animals i n  stomach contents  taken a t v a r i o u s times o f day and n i g h t a t S t a t i o n N . i n  the e a r l y summer o f I960 and i n the t h r e e d i f f e r e n t  p e r i o d s o f t h e summer  -91I9 6 0 EARLY S U M M E R N= 308 M E A N L E N G T H =15.8 M M  20 I O  L-—I  O  961 EARLY  30  5  trtmtmJL  SUMMER  N = 180 M . L, = 2 0 . 2  20  2 £  ,0  cO  5 o  MID SUMMER N=I66 M.L. = 2 2 . 0  cO  < 30 Z <  UJ CD  2  2 0 fI O  o  LATE  Z UJ  o < rr UJ  > <  N=  60  SUMMER  I80  M. L.=  33.l  50 40 30 20 IO  I200 2400 0400 0800 T I ME Figure 20. D i e l fluctuation of number o f animals i n the stomachs o f sucker f r y . Any two means not enclosed by the same bracket are different (P^0.05J. Blank: Planktonic animals. Shaded: Benthic animals. 1600  2000  -929 60 EARLY N=25l  20  SUMMER  MEAN L E N G T H = I 1.5 M M  i O  5 o  961  <  EARLY  O 20  N=I58  10  z  SUMMER  M. l_=l 5. 6  I O  CO  MID ^  SUMMER  N = l 27  30  <  M. L. = 20-l  LL  ° tr  20  |  IO  z  o  UJ  UJ  O  LATE  a. 4 0  N=l  >  M. L.=29-2  UJ <  SUMMER  •  52  3 Q 20 I O  600  2CX)0  2400  0400  0800  200  TIME  Figure 21. D i e l f l u c t u a t i o n of number of animals i n the stomachs of squawfish f r y . Any two means not enclosed by the same bracket are d i f f e r e n t (P^0.0$). Blank: Planktonic animals. Shaded: Benthic animals. Lined: T e r r e s t r i a l insects.  -93-  9 60 EARLY SUMMER N=l 60 MEAN LENGTH= I 5.7 MM  IO -  I  u  1 o  961 EARLY SUMMER N=l 2 0 M . L . = 2I.4  o  50  Z  v>  1  25  _J  <  I o  MID  SUMMER  N=( 6  U.200 O  M . L.=28.3  CO  3 IOO z O <  OC  £  LATE  O  SUMMER  N=58 M . L . = 4 1.6  IOO 50  I600  20 0 0  2400 0400  0800  ] 1200  TIME  Figure 22.  D i e l f l u c t u a t i o n of number of animals i n the stomachs of peamouth chub f r y . Any two means not enclosed by the same bracket are d i f f e r e n t (P40.05). Blank: Planktonic animals. Shaded: Benthic animals. Lined: T e r r e s t r i a l insects.  -94-  960 MID  O  SUMMER  N—122  MEAN L E N G T H = 11.9 MM 5 -  I  u < 5  o  961 EARLY  2 5  SUMMER  N = l SO M.L.=IO.B  20 ^ I5 <  < u. O  5  cc Id CD  O  2  MID  SUMMER  N=»I58  O  M . L. = l 8.3  UJ  <  CC  UJ  1  > < 5  •  •-  1  L  L A T E SUMMER N=M9 M. U = 2 6 . 3  -  TTTTT  O  6 OO  2000  2400  0400  0800  200  TIME  Figure 23.  D i e l i'luctuation of number of animals i n the stomachs of redside shiner f r y . «r:y two means not enclosed by the same bracket are d i f f e r e n t (P^0.05). Blank: Planktonic animals, shaded: Benthic animals. Lined: T e r r e s t r i a l insects.  -95-  I 960 EARLY SUMMER N==262  i f  I U <  5 O  MEAN  5 961 EARLY S U M M E R N=I80 M . L.= 2 0 . 7  O  i- I O -  to  I  5 jCO  <  i  O  u. O  ID  <  SUMMUR  •  N = 171  M . L.= 2 1.9  "I •  ct Mi  •  _H__  MID  z < IO  CD 5 z> z  LENGTH = 16.4 M M  • B •  LATE  20 -  SUMMER  N = I79  M . L . = 22. 6  cc  15 -  5  IO -  UJ  ] n 1  5 O  1600  2000  •  24GO  J  0400  TIME  0800  1200  Figure 24. Diel fluctuation of number of animals in the stomachs of prickly sculpin fry. Any two means not enclosed by the same bracket are different (P4 0.Q5). Blank: Planktonic animals. Shaded: Benthic animals. Lined: Terrestrial .insects.  -96o f 1961.  Duncan's M u l t i p l e Range T e s t was  f e r e n c e among t o t a l numbers.  used to t e s t  s i g n i f i c a n c e of d i f -  O r i g i n a l counts were transformed  because empty stomachs were i n c l u d e d as a count, and  toX+0.5,  the d i s t r i b u t i o n i s  not normal but u s u a l l y i s P o i s s o n w i t h v a r i a n c e p r o p o r t i o n a l to the mean and  non-additive  effect  (Snedecor, 1959)'  The  numbers grouped w i t h a  square b r a c k e t on the f a r r i g h t s i d e o f each graph a r e not  significantly  d i f f e r e n t from each o t h e r . The  t o t a l number o f food a n i m a l s i n the d i g e s t i v e t r a c t s o f  s p e c i e s d e c r e a s e s d u r i n g the n i g h t , and d u r i n g the day The  ( w i t h the one  these  t h e r e i s an i n c r e a s e i n f e e d i n g  e x c e p t i o n o f s h i n e r s i n the l a t e summer, 1961).  d e c r e a s e i n number o f animals i n the stomachs c o l l e c t e d a t n i g h t  i n d i c a t e s t h a t these  s p e c i e s do l i t t l e  feeding at night.  seen even i n the s c u l p i n which does not  This trend i s  show c l e a r o n s h o r e - o f f s h o r e  move-  ment. I f food animals a r e (terrestrial,  separated  i n t o t h r e e groups by h a b i t a t d i f f e r e n c e s  p l a n k t o n i c , bottom), each group seems to show d i f f e r e n t  trends of f l u c t u a t i o n .  The animals i n the t e r r e s t r i a l group, D i p t e r a ,  Ephemeroptera, P l e c o p t e r a and  T r i c o p t e r a , were found i n the d i g e s t i v e  t r a c t s o f the s h i n e r throughout the day. seemed t o be afternoon,  eaten  insect adults  to a g r e a t e r e x t e n t e a r l y i n the morning and  l a t e i n the  when the i n s e c t s tended to more f r e q u e n t l y d e p o s i t eggs or to  emerge (see S e c t i o n IV-5). the Des  However, these  Starrett  (1950) r e p o r t s s i m i l a r c o r r e l a t i o n s on  Moines R i v e r , Iowa where an i n c r e a s e o f the emergence o f  Ephemeroptera and  T r i c h o p t e r a was  noted i n the food o f c e r t a i n minnows  c o l l e c t e d a t dusk. I t was dawn and  a l s o n o t i c e d some f i s h e s feed on  plankton  e a r l y i n the morning than a t o t h e r times.  more f r e q u e n t l y a t  The  squawfish, chub and  -97-  shiner definitely showed this tendency, but the sucker and sculpin did not show remarkable fluctuation although they tended to feed on more plankton early in the morning.  There seems to be a correlation between plankton  feeding activity and diurnal fluctuation of plankton in the inshore water. As was described in Section IV-2, Cyclops, Diaptomus, nauplii and Daphnia (the main food items of these fry) showed marked increase between 2000 and O/4OO hours and sudden decrease between 0400 and 0800 hours.  It i s unlikely  that only downward movement as they show i n the deep offshore area, i s responsible for this sudden decrease.  Predation by fry at dusk also should  be considered as a factor. The animals of the benthic group were found in the digestive tracts throughout the day.  There seems to be a trend in these animals.  Their  number in the digestive tracts of these fishes began to increase at 1200 hours and was continued until 2000 hours although i t was not so obvious as was found in the planktonic group. From these results of analysis of stomach contents and of net-plankton, an hypothesis can be set up, as follows. After fry of these species (except the sculpin) move out at dusk, the plankters move toward the surface in the offshore area, and into the inshore area either by themselves or by drifting.  At dawn, fry of the cypriniform species move into  the inshore area and consume the rich plankton resources.  By this vigorous  predation the plankters are virtually eliminated in the morning.  Thus, the  fish are obliged to change food items, turning in the afternoon to animals of the benthic group or on the terrestrial insects.  If this hypothesis i s  acceptable, i t may be true to say that the fish compete for plankton as a limited resource at certain times of the day. However, as was mentioned in the previous section, food preferences  -98are divergent in some combinations of the species, especially in the later part of the summer. At least, they prefer the same animals to different degrees, as the rank correlation shows (Table 20 and Fig. 19).  Also i t i s  highly possible that some of them occupy different food niches from each other although their stomach contents are interspecifically overlapped (see Section VII-1, 2).  These partially competitive relation may play a role i n  reducing competitive interaction.  For the sucker, shiner and sculpin i n  the early summer and for the squawfish and chub i n the whole summer period, however this sort of avoidance of competitive relations is scant because of similarity of their requirements  (see Section VII-1,:.2).  VIII.  GEOGRAPHIC EVIDENCE  An alternative approach to the problem of demonstrating interspecific relationships i s available from comparison of species associations i n lakes. Presumably, i n a smaller lake potentially competitive species would be forced into closer association, and the situation would be resolved more often (or more quickly) than i n larger lakes. This hypothesis can be tested by examining the number and associations of species i n the Fraser River system.  A l l of the lakes chosen for this  examination meet the following requirements: 1) They contain no transplanted fish. 2) No severe density-independent  mortalities such as winter-kill or  summer-kill are experienced. 3) Their altitudes are no higher than the natural tolerance limits of the fish species. 4) No poisoning programmes have been conducted i n their waters. In the appendix table the surface areas and the number of species of Catostomidae, Cyprinidae and Cottidae of the lakes are represented.  These  fishes are inshore inhabitants and they are thought to be i n closer association at least during their early l i f e history. Among suckers bridgelip sucker occur i n Nicola Lake and Tachick Lake which have neither longnose sucker nor white sucker.  Two or more species  of suckers coexist i n the lakes larger than 500 acres, while only one species, largescale sucker, or none occur together in the lakes smaller than 500 acres. The three commonest minnows in the Fraser River system, northern  -100squawfish, peamouth chub and redside shiner, coexist in 20 out of 25 lakes larger than 300 acres.  Carp, chiselmouth chub, longnose dace and leopord  dace which are rather rare species in British Columbia lakes are onlypresent in large lakes,  lake chub can be found in some lakes located in  the Upper Fraser area.  This species exists in large lakes and also in two  small lakes where none or only one other species i s present. Cultus Lake i s the sole lake known to be inhabited by aleutian sculpin. Location of this lake in the Lower Fraser Area suggests that this species has not invaded further than this point.  Prickly sculpin occur more  frequently in larger lakes. There i s the same tendency in each taxonomic group, that i s , the larger the lake i s , the greater the number of related species occur.  If  the seven common species of these three groups, (largescale sucker, longnose sucker, bridgelip sucker, northern squawfish, peamouth chub, redside shiner and prickly sculpin,) are combined, the same trend can be seen. More than six species coexist only in lakes larger than 1,000  acres,  five species only in those larger than 500 acres and 4 species only in those larger than 300 acres with the exception of Squakum Lake that i s inhabited by 4 species in spite of i t s small size. Fig. 25 shows the correlation between the surface area and the number of species of these taxonomic groups.  The figure definitely shows positive  correlation; that i s , the larger the lake i s , the greater the possibility of coexistence between these species. The geologic history of the Fraser River drainage must be an important factor limiting the distribution of fish.  According to Mathews (1944), the  Thompson and Nicola River drainages were connected with the Columbia River drainage in late-Pleistocene when the front of the last ice sheet was  I  r-» O  O I  O IO  Figure 25-  O I O OO I O O O SURFACE AREA CACRE)  Correlation between the surface area (logarithmic scale) and the number of species in selected lakes of the Fraser River drainage.  -102retreating.  At this time, some of the lakes within the present Fraser  drainage contained species of fish that were not found in the neighbouring drainages.  However, during the estimated 10,000 years since the establish-  ment of the present drainage system i t i s certain some movements of fish between lakes has occurred. Elimination of prey populations by predators may have happened in small lakes.  The circumstance of such cases may be similar to those of the  Case III situation-"homogeneous microcosm with immigrations" shown by Gause (1934)•  In this experiment after the predators had devoured a l l the prey,  they shrank in size and finally died. After the death of the predators the immigrating prey initiated a new cycle of population growth.  Actually, in  British Columbia the squawfish, a piscivore, occurs only in lakes inhabited by other fish.  However, some barren lakes may once have contained both  predators and prey and the present absence of fish may be due to elimination of prey and subsequent death of the predators. inhabited only by nonpredacious  Other small lakes  species may once have had a population of  squawfish which by overpredation may have eliminated i t s e l f .  IX.  INTERSPECIFIC COMPETITION  The general aspect of interspecific competition between the fry of the five inshore species in Nicola Lake may be summarized as follows. After emerging, the fry of a l l species move to the head of the lake where there i s a tendency to form an early-summer aggregation.  By late-  summer factors of dispersal and mortality appear to be responsible for decreasing densities.  During the early-summer period the opportunities for  interspecific competition would seem to be at a maximum. To a certain extent the species are separated spatially and temporally by differences i n diurnal movement, distribution in relation to depth and preference for types of habitat. Moreover the various species show morphological adaptations which reflect their differences in behavior and habitat. These differences increase with age. The feeding habits of the fry of the five species are very similar in early summer. At this season they are typically plankton feeders, but towards the end of summer their interspecific feeding relations gradually become less because of the divergence in food preference, feeding places, and feeding manners.  These changes are in turn largely due to morphol-  ogical changes, in particular those of feeding structures. In early summer, severe interspecific competition for the rather scarce planktonic crustaceans i s thought to occur among a l l the species except the sculpin which by this time occupies a bottom habitat. Such severe competition i s probably only continued for two or three weeks, and the evidence i s that i t becomes less and less important as the summer continues.  The rates of divergence i n feeding habits are different between  -104the combinations of species.  Between the squawfish and chub the rate i s  low, and by the end of the summer their modes of l i f e are s t i l l quite similar.  This ecological situation i s reflected by their diets which  showed a significant correlation throughout the summer period. However, the degree of correlation decreased toward the end of the season.  Thus,  competitive relations between the squawfish and chub may be expected even in late summer although they have by this time become somewhat less intense. The rates of divergence i n the food preferences of the remaining combinations of species are usually much higher than that of the squawfish-chub combination, so that competition for food between these species combinations i s likely to be rather mild by mid- and late summer. Nevertheless there remains a substantial residue of interspecific association and a sufficient dependence on a common food supply to make i t likely that competition between species occurs.  For instance, by vigorous  predation by the fry, plankters are virtually eliminated in the morning. Thus, the fish are obliged to change food items.  It suggests that the fish  compete for plankton as a limited resource at certain times of the day. The kinds of interspecific relations in other lakes would be different from that in Nicola Lake.  In a smaller lake potentially competitive species  would be forced into closer association, and in a larger lake they would have more opportunities to share the resources.  Judging by the geographic  evidence competition in small lakes may be a factor in eliminating some of the species.  X.  (l) (a)  DISCUSSION  Characteristics of Freshwater Fishes and Environments  Characteristics of freshwater environments Elton (1946) describes freshwater communities as consisting "mainly of  a few ecological groups, each broadly drawing upon the same natural resources for i t s basic food, with of course the usual predator parasite food cycles rising from i t . "  He also remarks on the relative shortness of  food chains i n freshwater communities and their general similarity to the simple terrestrial communities of Arctic and Subarctic areas. This description i s acceptable as far as stream communities are concerned. follows.  Reid (1961) describes characteristics of stream habitats as "Current-created turbulence tends to maintain a relatively  uniform set of physico-chemical conditions (at least within a given segment) normally free from stratification such as found in lakes.  Sorting  of bottom materials resulting from variable stream velocity produces a great variety of substrates for colonization and the development of communities." Larkin (1956) suggests that the type of vertical stratification existing in lakes is entirely different from that in forests.  Plant cover i s  only afforded at the margins of the uppermost stratum, setting i t aside as the l i t t o r a l zone, a separate community from the epilimnion in the open water area.  In freshwater lakes there i s l i t t l e in the way of substitute  for the cover and the diversity of opportunities for niches that are provided for the animals inhabiting a forest. However, i f the inshore area of a lake i s carefully observed, one w i l l  -106-  find beautiful illustrations of the vertical stratification of animals. For example, in the case of Cladocera, Daphnia occupies the habitat of a typical planktonic animal, Alona walks on the bottom, and Chydorus, the intermediate, i s found either on the bottom or else swimming near i t . similar type of stratification can be found i n copepods.  A  Both Diaptomus  and Cyclops are planktonic. However, Diaptomus i s more active and occupies the whole depth whereas Cyclops i s distributed in somewhat deeper water and consequently i s usually closer to the bottom. Harpacticus, i s restricted to bottom debris. (1961),  The third copepod, As was pointed out by Reid  benthic communities in lakes grade not only horizontally, but also  vertically in relation to depth.  Dendy (1948) showed that several fish  species in three TVA reservoirs .exhibited vertical stratification which could be related to thermal stratification and dissolved oxygen contents. In lakes, such physico-chemical conditions as stratifications in temperature, pressure, illumination, turbidity and dissolved gases and solids probably play as important a role i n the distribution of animals as the microclimatic stratifications produced by plant l i f e in forests. To sum up, Larkin s conclusion "by comparison with the complex type of 1  population interspersion for a forest community, the spatial organization of plants and animals in freshwater habitats i s extremely simple" i s fully acceptable for a stream community.  However, in lakes a rather complex  distribution of organisms does exist and i s probably related to the stratification of physico-chemical factors, (b)  Characteristics of freshwater fishes. There are two entirely different opinions about the characteristics of  freshwater fishes.  According to one view freshwater fishes are apparently  very generalized (Larkin, 1956).  However Fryer (1959 a) takes another view  -107and argues that many t r o p i c a l freshwater f i s h e s are on the contrary highly specialized.  Before discussing the i n t e r s p e c i f i c r e l a t i o n s h i p of the  l a r v a l f i s h i n Nicola Lake, i t i s necessary to point out why  such opposite  opinions could have been proposed. Larkin (1956) states that studies of food habits of f i s h suggest that f l e x i b i l i t y and a d a p t a b i l i t y are the general rule, and that c l e a r cut cases of a demand on a readily defined mutual supply are rare.  His idea seems to  be based on the following phenomena; l ) i n t e r s p e c i f i c overlapping of stomach contents, 2) seasonal v a r i a t i o n of food habit, 3) temporary changes in feeding habits which can be related to the changing a v a i l a b i l i t y of food organisms.  He suggests that the simplicity of organization of  freshwater  environments i s the mechanism responsible f o r bringing about these phenomena. Many workers have reported that i n t e r s p e c i f i c overlapping of stomach contents i s a common occurrence. tendency i n Lake Nyasa. t e r r e s t r i a l animals.  EVen Fryer (1959 a) notes the same  This phenomenon i s also common among various  MacArthur (1958) has shown that some warblers  d i f f e r i n g main food items s t i l l show a certain overlapping of these  with items.  Hartley (1953) reports that the great t i t , blue t i t , coal t i t , and marsh t i t often feed on l e a f - e a t i n g c a t e r p i l a r s i n May and beechmast i n autumn when these foods are temporarily superabundant.  Hawbecker (1944) reports  that the giant kangaroo rat i n a Californian forest feeds c h i e f l y on seeds of the red brome.  These seeds also form a s i g n i f i c a n t portion of the food  of the San Joaquin antelope s q u i r r e l and other sympatric  rodent species.  In the temperate and subarctic regions seasonal and temporary changes of food items may not only be c h a r a c t e r i s t i c of freshwater fishes but also commonly of vertebrates i n general.  Lack (1954) describes many examples of  -108-  seasonal changes of food in birds, and indicates as does Hartley that common birds feed on the items which are often the easiest to obtain.  Thus,  f l e x i b i l i t y and adaptability in feeding habits are found not only in freshwater fishes but also quite commonly in terrestrial vertebrates of the temperate regions as well. Fryer (1959 a, b) states that the very striking adaptations shown by many fishes in Lake Nyasa rigorously restrict most of them to one habitat and to one kind of food.  He speculates that the specializations shown by  these Nyasan fishes can be regarded as a reflection of the relatively permanent nature of their environment. It may be accepted that temporary or seasonal changes in the diets of fish are extremely rare in tropical lakes.  However, i t i s doubtful that  these same species of fish would show the same feeding specializations i n other aquatic communities, in which just simple habitat stratification i s present.  Miuz-a (1959) notes very significant dietal differences between  the same species of fish living in a natural lake and a reservoir. In summer most cyprinids in the reservoir fed on planktonic crustaceans such as Bosmina, Bosmlnopsis and Cyclops.  These apparently generalized feeding  habits were due to the extreme sparcity of available food organisms, but in a natural lake where the types of food available was more diversified these cyprinids showed specializations in feeding habits.  Even the bottom  dweller zezera (Blwia zezera), which has an inferior sucking type mouth as i s the case with catostomids, feeds mainly on planktonic crustaceans.  This  example indicates that regardless of how a fish may be adapted to a specific mode of l i f e in both morphological and behavioral features, this fish may under certain circumstance consume a food item which one would hardly have expected.  Fryer himself (1959 a) notes that some species of  -109-  fish show variations in diet according to the particular circumstances under which they live.  Pseudotropheus tropheops and Labeotropheus  fuelleborni which eat Galothrix  at Nkata Bay and elsewhere, feed on only  loose Aufwuchs  Secondarily, Fryer states that such spe-  ll  at Mbamba Bay.  cialisation of fishes can be regarded as a reflection of the relatively permanent nature of their environment and that because of the essentially transient condition of most freshwater situations the fishes would show quite opposite tendencies.  However, Myers ( i 9 6 0 ) introduces similar  examples in the temperate region. i c a l l y disturbed.  "Stream environments are usually period-  However, in the far richer temperate freshwater fish  faunas (e.g. of north-central China, the rivers of Ohio or Virginia, or the vicinity of Buenos Aires) a river i s usually inhabited by five or ten times as many species as those of a comparable British or Canadian stream, the number of species i s often or usually much larger than in any known lake fauna, and narrow trophic and habitat specialisations are the rule." It i s apparently reasonable to assume that the diversity of habitats in an aquatic community as well as the permanency of environmental conditions reflects on the characteristics of fishes. As was mentioned at the beginning of this discussion, the diversity of niches in a lake i s not to be expected in a stream.  In the stream habitats  i t i s natural for the feeding habits of fishes to converge because there i s often l i t t l e opportunity for vertical stratification in distribution and the fish are therefore often compelled to consume the same food.  Frequently  fish segregate spatially in a horisontal direction under such conditions 1/  The German term "Aufwuchs"", i n i t s widest sense includes also a l l the animals living among the algae, but which i s here restricted to the plant constituents of the association.  -110rather than enter into severe competition and consequently may be required to change their diets.  Miyadi et a l . (1952) reports that pale chub (Zacco  platypus) occupied the central part of a river-rapid when ayu (Plecoglossus a l t i v e l i s) were absentfromthe river.  When ayu ascended the river and  gradually settled down in the rapid, the chub were forced to move to suah less favourable places as the river-periphery or the boundaries between a rapid and a pool.  Kawanabe (1959) also observed that a dense population of  ayu occupied a l l the areas in which bottom algae were growing on gravel or stones; and the chub were driven away to a much more marginal existence in quiet areas under willows or without stones.  A similar amensalismic segrega-  tion of living sites was reported by Lindstrom (1955) between fry of Salmo salar and of S. trutta in a Swedish river. Imanishi (1951) observed competitive spatial segregation between two salmonids in streams in Japan.  Iwana (Salvelinus pluvius) was distributed  along the upper parts of the streams while yamame (Onchoryncus masou) was distributed the lower parts of the streams.  This distribution can be  related to the fact that iwana prefers a colder water temperature than yamame. However, the boundary of distribution between these species may not be settled by temperature but rather by social interaction.  This view  is supported by the fact that ivana expands i t s distribution in a down stream direction i f yamame i s absent in the river and vice versa.  To the  author's knowledge no examples of the existence of such a phenomenon in lakes have been reported.  Thus, the distribution of freshvjater fishes may  be modified markedly by the environmental conditions of the habitats. Fryer's suggestion that freshwater fishes may be highly specialized seems to be acceptable not only for fishes in tropical lakes but also for fishes in large horizontally and vertically stratified temperate lakes and  -Illrivers where there i s opportunity for spatial segregation and specialization of habitat preference.  Larkin*s idea of f l e x i b i l i t y and adaptability  in feeding habits i s usually true of fishes in a simple environment such as streams, U-shaped reservoirs or a small environment where resources are sufficiently limited that species are forced into coexistence.  In short,  freshwater fishes express their potential for specialization only in environments which provide appropriate opportunity. The writer concludes that characteristically freshwater fishes are specialized by nature but with a degree of f l e x i b i l i t y and adaptability which w i l l allow them to adjust to a limited range of factors.  (2)  Interspecific Relationships  Many biologist have noted species of fish, which as adults show interspecific divergence, may have very similar modes of l i f e i n their early larval stages.  The process of divergence in their modes of l i f e with the  progression of developmental stages was traced i n the five inshore species in Nicola Lake. Emphasis was put on their microhabitat preferences and feeding habits (see Section VI-4 and VII).  It i s natural that the inter-  specific relationships among these five species change as their modes of l i f e are altered. Mutualism, commensalism, amensalism, parasitism and predation never occur among these species during their f i r s t summer.  The possibility of  interspecific competition occurring should be considered because a l l the species occurred together i n the inshore area during the daytime, and large interspecific aggregations usually containing a l l five of the species were not unusual in the lake.  -112-  (a)  Competition for space Living space, which can be defined as a quantity of water which  satisfied the conditions required to sustain a fish, has been considered as an ecological factor (see Allee et a l . 1949, P- 22; Larkin, 1956; Magnuson, 1961).  Magnuson summarizes several previous contributions and concludes  that i f food i s supplied in excess, the need for space, per se, in aquatic animals i s primarily a consequence of accumulating waste products.  However,  the large volume of water and the mixing of water near the shore makes i t doubtful that such conditioning of the environment has any significant effect on the mortality and growth rates in Nicola Lake. Many biologists have reported that some t e r r i t o r i a l fish species require a certain volume or area of environment as a living site (Miyaji et a l . , 1952, Kawanabe 1958 in ayu; Lindroth 1955, Newman 1956, Kalleberg 1958, in salmonids).  Neither t e r r i t o r i a l behaviour within species nor that  between species has been observed in the fry of the five species in Nicola Lake. Another type of interspecific competition for space may exist among non-territorial fishes. Nilsson (1955) notes that in Lake Ransaren in North Sweden, Salmo trutta inhabits mainly the shallow, interior parts of the region and S. alpinus inhabits the deeper exterior parts.  However, in  lakes inhabited only by either S. trutta or S. alpinus, the population has a more even distribution over the entire lake.  This difference in distribu-  tion indicates that the presence of one species exerts a sort of pressure which keeps the second species out of the area. The netting results from Station N did not indicate interspecific differences in the horizontal distribution of the five species (Section VI3, Table 5 ) . Also as was discussed in Section VI-5, analysis of rank correlation coefficents as an indicator of interepecific association did  -113not r e v e a l the e x i s t e n c e o f p o s s i b l e a n t a g o n i s t i c p r e s s u r e s between s p e c i e s . The  f i s h do  show s t r a t i f i c a t i o n i n v e r t i c a l d i s t r i b u t i o n d u r i n g l a t e the  summer,  but i t seems more l i k e l y t h a t the reasons  f o r occupying  different  h a b i t a t s a r e because o f m o r p h o l o g i c a l and  e t h o l o g i c a l a d a p t a t i o n s to the  h a b i t a t r a t h e r than a n t a g o n i s t i c p r e s s u r e s (see S e c t i o n V I I - 1 ) . Thus, i t may not important  be concluded  o r a t l e a s t not  t h a t i n t e r s p e c i f i c c o m p e t i t i o n f o r space i s so severe among the f r y i n N i c o l a Lake as  among stream i n h a b i t a n t s . (b)  Competition  f o r food.  The o t h e r important  environmental  resource i s food.  Obviously  two  s p e c i e s consuming d i f f e r e n t  food items do not compete d i r e c t l y f o r food  though i t might be expected  t h a t they compete i n d i r e c t l y f o r food as a  r e s u l t o f c o m p e t i t i o n f o r o t h e r r e s o u r c e s such as space. g e n e r a l r u l e , two  sympatric  u s u a l l y c o e x i s t without 1954;  F r y e r , 1959 The  species with d i f f e r e n t  competition  food  ( G r i n n e l l , 1904;  However, as a requirements  Crombie, 1947;  Lack,  a, b ) .  food p r e f e r e n c e s of t h e f r y i n N i c o l a Lake, a s i n d i c a t e by  stomach c o n t e n t s , are the  same o r a t l e a s t  but, w i t h the e x c e p t i o n o f the squawfish  their  very s i m i l a r i n the e a r l y summer,  and  chub t h e i r demands f o r food  d i v e r g e i n the l a t e r p a r t o f the summer (see S e c t i o n V I I - 2 ) . gence i n food p r e f e r e n c e s i s a q u a n t i t a t i v e r a t h e r than a  This d i v e r -  qualitative  change a l t h o u g h the i n t e r s p e c i f i c o v e r l a p p i n g o f stomach c o n t e n t s i s markedly reduced  towards the l a t e  summer.  such d i v e r g e n c e s h e l p to a v o i d s e r v e r e (c)  Factors minimizing  I t can s a f e l y be assumed t h a t  competition.  c o m p e t i t i o n f o r food  Superabundance o f f o o d :  The  fact that d i f f e r e n t  s p e c i e s o f f i s h eat  the same foods i s not j u s t cause f o r assuming they a r e competing ( L a g l e r ,  1944;  Larkin,  1956).  -114-  Several mechanisms to avoid severe competition  between animals eating the same foods have been reported.  Crombie  (1947)  states that a common diet for closely related species living in the same habitat can be interpreted either as a sign of temporary superabundance of food or as an indication that parasites or predators are controlling the numbers of both species. freshwater fishes.  Such ecological phenomena have been reported in  Nilsson  (1955)  found that when the organic production  in Lake Blasjon was very high and the fishes (Salmo trutta and S. alpinus) consequently were in good condition, an obvious breakdown of the limits of the niche occurred.  He interprets this phenomenon as suggesting that the  two species could feed on the same food without competing because of the super-abundance of food.  The idea of conserving the condition of super-  abundant food has long been discussed in fisheries management (Lagler, Bennett,  1944, 1947;  Swingle and Smith,  1941).  1944;  It has been suggested that  this be accomplished by removing a number of the fish by human or natural predation.  Fryer (1959  a, B) speculates that the presence of predators  w i l l tend to favour the survival of certain non-predacious species in Lake Nyasa.  Daiber  (1956)  notes an example of how the physiological condition  of the fish can serve a similar function.  Under low temperatures in winter  the two benthic stream fishes, Etheostoma f. flabellare and Cottus b.bairdi, show a reduced demand for food because of a lower metabolic rate.  He  states that such a condition can reduce or even eliminate any competition between two species even though the diet remains qualitatively the same. It i s d i f f i c u l t to detect whether food i s super-abundant or not in a natural environment.  However, in the inshore area of Nicola Lake a super-  abundance of planktonic crustaceans in hardly possible, because by midmorning the fish fry have consumed most of the rich plankton resource  -115-  supplied to the area during the night by the offshore plankton populations, and by afternoon they have begun to feed primarily on benthic organisms (see Section VII-4).  In the early summer when the principal food of the  fry of a l l the five species i s planktonic crustaceans, there is a chance that they may be involved i n severe competition for food. Spatial separation of feeding place:  The possibility exists that  different species effectively separate themselves spatially.  For example,  each may eat the same foods but in different parts of a lake (larkin, 1956). Fryer (1959 a) has shown some good examples in Lake Nyasa.  Two out of  seven common Aufwuchs eating species live close inshore and have a different horizontal distribution than the rest.  In addition two insect  eaters, Labidochromis vellicans and Haplochromis omates, have very similar diets but seldom come into contact because of their different horizontal ranges.  A spatial separation among fish species eating the same food has  been observed on many occasions.  Two examples from this continent include  the separation among; suckers, minnows and salmonids i n Okanagan Lake (Clemens et a l . 1959), and between yellow perch and salmonids in Thompson Lakes (Echo, 1954)-.  In Europe Lindroth (1955) and Nilsson (1955) have  found a spatial separation between two salmonid species i n the River Indalsalven and Lake Ransaren respectively. In Japan similar distribution patterns have been noted for ayu and pale chub i n the Kamikatsura River (Miyadi et a l . , 1952).  One would expect competition to be minimized by the  different horizontal distributions of the fish involved. The fry of the fishes in Nicola Lake did not show such distributional differences. distributions.  However by late summer they did have different vertical The sucker and sculpin formed one association on the bottom  and the squawfish, chub and shiner formed a pelagic association (see Section  -116-  VI-3).  W i t h i n each a s s o c i a t i o n some degree o f c o m p e t i t i o n i s t o b e .  expected, two  b u t d e s p i t e the p a r t i a l o v e r l a p p i n g o f food p r e f e r e n c e  a s s o c i a t i o n s i t i s p o s s i b l e t h a t severe i n t e r - a s s o c i a t i o n  i s l a r g e l y avoided  between  competition  by t h e d i f f e r e n t v e r t i c a l d i s t r i b u t i o n p a t t e r n s .  Microhabitat segregation:  I f a f i s h h a b i t a t was more m i n u t e l y  examined, i t i s p o s s i b l e t h a t d i f f e r e n c e i n the s o - c a l l e d m i c r o h a b i t a t might be shown between two s p e c i e s which a p p a r e n t l y have t h e same h a b i t a t . Such m i c r o h a b i t a t d i f f e r e n c e s may g i v e t h e f i s h e s an o p p o r t u n i t y t o occupy separate n i c h e s . stand  Allen  (1941) d i s c u s s e s t h i s e c o l o g i c a l s i t u a t i o n from the  p o i n t o f food a n i m a l s .  He s t a t e s t h a t the h a b i t s o f a p o t e n t i a l  a n i m a l a f f e c t t h e extent t o which i t i s eaten, e x t e n t t o which i t o c c u r s i n ing f i s h .  p l a c e B  s i n c e they determine t h e  where i t i s l i k e l y t o be seen by a f e e d -  As an example he d e s c r i b e s a s a p o s s i b l e case t h a t o f t h e fauna  o f a stony r i v e r - b e d j those a n i m a l s exposed  food  which l i v e l a r g e l y upon t h e upper,  s u r f a c e s o f t h e stones can be seen much more f r e q u e n t l y by f i s h  l y i n g above t h e stones than  can those which l i v e h a b i t u a l l y on the under  s u r f a c e s and the beneath the s t o n e s .  F r y e r (1959 a) g i v e s as an example i n  Lake Nyasa t h e i n v e r t e b r a t e f e e d e r s B a t h y c l a r i a s w o r t h i n g t o n i and Mastacembelus s h i r a n u s which a c t u a l l y l i v e beneath t h e r o c k s , thus i n g a d i f f e r e n t m i c r o h a b i t a t from t h a t o c c u p i e d  by the o t h e r  frequent-  s p e c i e s which  never go beneath r o c k s f o r a n y t h i n g more than temporary s h e l t e r .  Although  the f r y o f t h e f i s h e s i n N i c o l a Lake a r e grouped i n t o two a s s o c i a t i o n s by v e r t i c a l h a b i t a t d i f f e r e n c e s , o b s e r v a t i o n s o f t h e i r l i f e a t S t a t i o n N and o f t h a t i n an aquarium do not i n d i c a t e the presence o f more micro h a b i t a t differences. D i f f e r e n c e i n f e e d i n g time:  Difference i n d i e l feeding a c t i v i t y  between two s p e c i e s having t h e same food requirement  may be a n o t h e r  -117-  mechanism to avoid severe overt competition.  Hawbecker (1944) reports this  mechanism i n rodents in a forest in California.  The giant kangaroo rat  (Dipodomys ingeus) and San Jouquin antelope squirrel (Citellus nelsoni) occupy the same territory and feed partially on the same food, but they do not compete, since the former i s abroad at night and the latter during the daytime.  The fry of a l l five species in Nicola Lake showed active feeding  in the light and l i t t l e feeding in the dark.  As a general rule the fry fed  more on the planktonic organisms i n the morning and on the benthic organisms in the afternoon (see Section VII-5). Morphological differences:  Fryer (1959 a) reports that morphological  difference in the mouth may give the fish an opportunity of consuming the same food but at different place.  For example, because Haplochromis  fenestrates has a narrow mouth i t may be able to collect loose Aufwuchs from cracks which are inaccessible to five other species feeding on the same food. In the mid- and late summer a striking example of such a case in Nicola Lake i s offered by the fry of sucker and sculpin when each of the species occupy the bottom habitat, and their stomach contents show overlapping of food habits.  Because of the subterminal mouth of the sucker fry  they may be able to eat the animals staying on the bottom by sucking them in and with the help of their comb-like pharyngeal teeth sort them out from the inorganic particles.  The sculpin, on the other hand, has a horizontal  mouth and no adaptive structure for sorting out inorganic particles and hence in a l l probability has a somewhat different feeding niche.  The  rarity of sand grains and benthic algae in the stomachs of sculpin fry does in fact seem to indicate that they pick out rather than suck up their food. The strongly oblique mouth of the shiner fry i s probably best adapted for  -118c a t c h i n g t e r r e s t r i a l i n s e c t s on the water s u r f a c e , and chub and  squawfish  advantageous.  f r y seldom a t t a c k t h e s e i n s e c t  Thus,morphological  s i n c e the p e l a g i c  such f e e d i n g h a b i t s a r e  c h a r a c t e r i s t i c s o f the mouth i n a s s o c i a t e d  w i t h these o f the r e s t o f the body a r e a r e f l e c t i o n o f the manner o f f e e d i n g . As was  p o i n t e d out by MacArthur (1958), d i f f e r e n t manner o f f e e d i n g i s an  important  reason why  under d i f f e r e n t  two  s p e c i e s may  eat d i f f e r e n t foods o r the same  situations.  S i z e range o f mouth:  The  s i z e range o f animals  which may  a g i v e n s p e c i e s o f c a r n i v o r o u s f i s h o f a g i v e n s i z e w i l l have definite limits a s p e r and  ( A l l e n , 1941).  Northcote  (1954) observed  be eaten  be r e l a t e d to t h e i n c r e a s e i n mouth s i z e .  t h a t the mouth s i z e o f e x p e r i m e n t a l  l i m i t on t h e s i z e o f food swallowed, but the f o o d organisms may o f the prey and  certain  t h a t as  Cottus  Hartman (1958)  Salmo g a i r d n e r i imposes a s t r u c t u r e and  reactions of  r e s u l t i n a c o n s i d e r a b l e d i s c r e p a n c y between t h e w i d t h  the mouth w i d t h o f the s m a l l e s t f i s h which can prey upon i t .  A s i m i l a r o b s e r v a t i o n i n char has been r e p o r t e d by Lindstrom  (1955).  He  found t h a t t h e r e i s an approximate c o r r e l a t i o n between the s i z e o f the and fish  the s i z e o f the f i s h .  The  f o r d i f f e r e n c e s between p o p u l a t i o n s i n  These o b s e r v a t i o n s i n d i c a t e t h a t i f t h e r e  d i f f e r e n c e s i n mouth s i z e between two by consuming the animals  severe  competition.  The  s p e c i e s e a t i n g the same a n i m a l ,  i n g and  they  s c u l p i n f r y i n N i c o l a Lake have a much l a r g e r  i r a k e r s and  are  w i t h i n d i f f e r e n t s i z e ranges not e n t e r i n t o  mouth than the f r y o f the o t h e r s p e c i e s and  teeth, g i l l  food  c o r r e l a t i o n i s v a l i d both f o r d i f f e r e n c e s i n  s i z e w i t h i n a p o p u l a t i o n and  the average i n d i v i d u a l s i z e .  may  by  C. rhotheus i n c r e a s e i n l e n g t h t h e y e x i b i t a marked change i n  d i e t which may observed  foods  t h i s along with t h e i r  spiny  i pharyngeal  t e e t h a r e l i k e l y o f advantage i n c a p t u r -  h o l d i n g l a r g e food a n i m a l s .  tend t o consume l a r g e r food  Hence i t i s to be  organisms.  expected  that  they  -119Difference in activity of food animals:  Lindstrb'm (1955) discusses  how the vigorous activity of a food animal may act as a mechanism of food selection by preventing the fish from capturing i t .  Fry in Nicola lake  were frequently observed trying i n vain to catch a copepod.  The sculpin  probably catches food animals by rapid movements which take them only short distances from their places of repose.  Thus, the sculpin fry may be able  to consume individuals of a more vigorous nature than those that can be consumed by the fry of the other species. Body shape and size:  Fryer (1959 a) reports that in Lake Nyasa  another mechanism of avoidance of competition occurs and i s related to differences i n body shape and body size.  Of six important invertebrate  eaters Labidochromis vellicans can take food from crannies inaccessible to a l l save L. caerulus and the smallest specimens of the other species and thus must be partially isolated in respect to i t s food even when i t s horizontal range overlaps that of i t s possible competitors.  Two crab and  ostracod eaters, Bathyclarias worthingtoni and Mastacembelus shiranus, for the most part occupy separate niches, since M. shiranus because of i t s eellike form i s able to enter and feed in crannies inaccessible to B. worthingtoni.  In Nicola Lake this type of mechnism was not observed among  the fry. Although not a strict parallel with examples from Lake Nyasa, one supposes that the flat ventral body surface of the sucker and sculpin may better adapt them to l i f e on the bottom than the cylindrical or laterally compressed bodies of the other species and thus the overall body form of the fry may, to a limited extent, indicate their choice of food.  (3)  Interspecific Competition and Co-existence  (Srinnell (1904), as recently quoted by Udvardy (1959), said:  "Every  -120animal  tends t o i n c r e a s e a t a geometric  o f food  supply.  I t i s only  r a t i o , and i s checked o n l y by l i m i t  by a d a p t a t i o n s to d i f f e r e n t s o r t s of food, o r  modes o f food g e t t i n g , t h a t more than one s p e c i e s can occupy t h e same locality.  Two s p e c i e s o f a p p r o x i m a t e l y  to remain l o n g enough e v e n l y balanced w i l l crowd o u t the o t h e r . " l a b o r a t o r y w i t h protozoans weevils  (Utida,  1953),  t h e same food h a b i t s a r e n o t l i k e l y  i n numbers i n t h e same r e g i o n .  T h i s p r i n c i p l e has been demonstrated i n t h e (Cause,  1934),  and c l a d o c e r a n s  f l o u r b e e t l e s (Park, 1954), bean  (Frank,  1952).  Examples from  have o f t e n been r e p o r t e d o f an i n v a d e r r e p l a c i n g a c l o s e l y r e l a t e d preoccupying and  the niche.  Swallows i n United S t a t e s , t h r u s h e s  bees i n A u s t r a l i a can serve a s examples (Darwin, 1869)  weasels i n Japan (Tokuda,  One  nature  species  i n Scotland,  as can mice and  1954).  I f each s p e c i e s o c c u p i e d  a d i f f e r e n t e c o l o g i c a l n i c h e , then  competi-  t i o n f o r t h e r e s o u r c e s o f the environment would be e l i m i n a t e d and two s p e c i e s would be expected 1947;  Lack, 1954).  t o c o e x i s t ( G r i n n e l l , 1904;  The g e n e r a l a p p l i c a b i l i t y o f t h i s p r i n c i p l e i s best  demonstrated i n t h e f i e l d w i t h b i r d s (Lack, R e c e n t l y F r y e r (1959  Gause, 1934; Crombie,  1954;  MacAuthur,  a, b) demonstrated t h i s p r i n c i p l e  1958).  i n the f i s h e s o f a  t r o p i c a l lake. However, t h e r e a r e many e c o l o g i c a l l y more o r l e s s coexist.  Such a s i t u a t i o n can continue  s i m i l a r species that  e i t h e r i f t h e p o p u l a t i o n s a r e main-  t a i n e d below the c a r r y i n g c a p a c i t y by c e r t a i n c o n t r o l l i n g f a c t o r s o t h e r than c o m p e t i t i o n , o r i f /there i s a mechanism by which two s p e c i e s share t h e r e s o u r c e s they r e q u i r e . In a q u a t i c h a b i t a t s , which a r e p h y s i c a l l y more s t a b l e , b i o l o g i c a l f a c t o r s would undoubtedly have an i n f l u e n c e on p o p u l a t i o n c o n t r o l s , although  i n some a q u a t i c h a b i t a t s and f o r some s p e c i e s o f f i s h ,  climatic  -121c o n t r o l s would seem t o outweigh b i o l o g i c a l f a c t o r s i n c o n t r o l l i n g  popula-  t i o n s ( L a r k i n , 1956). The  r e s u l t o f f i s h c o n t r o l programs i n ponds and  demonstrated t h a t p r e d a t o r s do l i m i t p o p u l a t i o n 1944,  1947;  Swingle and  overpopulation  and  Smith, 1941).  natural predators,  l a g l e r (1944), w h i l e  the r e s e a r c h done on o t h e r a n i m a l s , p r e d a t i o n may predators  be l i t t l e d i f f e r e n t  been a b s e n t .  shiner population. icantly limit  He  recruitment  small a population  of  basing h i s d i s c u s s i o n i n part  effect following  b) estimated  t h a t i n P a u l Lake the o n l y 5% o f the  t h a t p r e d a t i o n by t r o u t does not  o f young s h i n e r s to the p o p u l a t i o n .  total  signif-  Supporting  h i s argument i s the r e s u l t s o f t h e stomach a n a l y s i s which i n d i c a t e t h a t h e a v i e s t p r e d a t i o n was had  already  i n August a t a time when most of t h e a d u l t  the  shiners  spawned, and a l a r g e p r o p o r t i o n o f the s h i n e r s consumed a t t h a t  time would not have s u r v i v e d u n t i l t h e next spawning season. lakes at l e a s t predation f a c t o r o f prey  should not be o v e r e s t i m a t e d  as a  Thus, i n some  controlling  populations.  P a r a s i t i s m may population  on  from t h a t which would have r e s u l t e d had  by Kamloops t r o u t was  concluded  Bennett,  r e p o r t s emphasize t h a t  suggests t h a t the end  Crossman (1959  number o f r e d s i d e s h i n e r s eaten  s i z e ( L a g l e r , 1944;  Most o f these  s t u n t i n g a r e a r e s u l t o f too  l a k e s have f r e q u e n t l y  size.  be a n o t h e r important  Johannes and  s h i n e r s i n P a u l Lake, B.  C,  biological factor controlling  Larkin (I96l) report that i n d i v i d u a l  probably  consumed s i g n i f i c a n t l y l e s s food  y e a r s when they were h e a v i l y p a r a s i t i z e d . s i z e o f the s h i n e r may  t i o n s ( R o u n s e f e l l and  In t h i s case, the  be i n f l u e n c e d by the p a r a s i t e .  w e l l e s t a b l i s h e d as t o how  There seem t o be two  in  population  However, i t i s not  e f f e c t i v e parasites are i n l i m i t i n g f i s h  Everhart,  redside  popula-  1953)-  types o f s h a r i n g r e s o u r c e s by two  o r more s p e c i e s .  -122I t i s known t h a t p o p u l a t i o n s o f c l o s e l y r e l a t e d , a l l o p a t r i c a l l y s p e c i e s can have c l o s e l y s i t u a t e d e c o l o g i c a l optima, and intraspecific  competition alone  a l l i t s e c o l o g i c a l potency.  can compel each o f the  living  that i n t h i s  case  s p e c i e s to u t i l i z e  I f , on the o t h e r hand, the p o p u l a t i o n s  live  s y m p a t r i c a l l y , and under i n t e r s p e c i f i c c o m p e t i t i o n , the optima a r e removed from each o t h e r , w h i l e a t the same time, the amplitudes  around these  optima become narrower (Svardson,  1956,  K a l l e b e r g , 1958). of  1949;  N i l s s o n , 1955,  Some examples, mentioned p r e v i o u s l y , o f how  the optima can produce a s h a r i n g o f l i v i n g  ayu and  p a l e chub, M i y a d i e t a l . (1952),  yamame, I m a n i s h i Lindstrb'm  (1955);  cited  (1951); and  new by  displacement  space i n c l u d e t h a t between  Kawanabe (1959);  between f r y o f Salmo s a l a r and  between Salmo t r u t t a and  between iwana  and  o f S. T r u t t a ,  S. a l p i n u s N i l s s o n (1955) •  In streams t h i s phenomenon has been produced by an a l t e r a t i o n o f the optimum food c o n d i t i o n ( H a r t l e y , 1948; such d i s p l a c e m e n t was to  S t a r r e t t , 1950;  Kawanabe, 1959).  If  o f the optima o c c u r r e d o n l y t e m p o r a r i l y o r s e a s o n a l l y , as  the case between ayu and  p a l e chub, i t would be p o s s i b l e f o r the  r e c o v e r from these unfavourable  a b l e to s u r v i v e , t h e r e may ment o f the optimum was  periods.  fish  In such cases, i f the f i s h i s  be few d e t r i m e n t a l e f f e c t s .  However, i f d i s p l a c e -  continued f o r a p e r i o d o f s e v e r a l y e a r s , a  popula-  t i o n would c e r t a i n l y be h a r m f u l l y a f f e c t e d . The degree o f success t h a t a s p e c i e s o f f i s h w i l l have i n a d a p t i n g to c o n d i t i o n s present a f t e r displacement circumstances  o f the optima w i l l depend on the  o f the p a r t i c u l a r h a b i t a t and on the range o f p l a s t i c i t y  the modes o f l i f e o f the f i s h .  A f t e r displacement  o f the optima  in  small  l a k e s u s u a l l y do not o f f e r many o p p o r t u n i t i e s f o r t h e f i s h to adapt, because the s m a l l e r the l a k e , the s i m p l e r the s t r a t i f i c a t i o n I t has o f t e n been r e p o r t e d t h a t c o m p e t i t i o n f o r food and  of habitats.  habitat despoil-  -123-  tnent in a small or shallow lake usually results in only a few dominant species of fish.  The remaining species tend to be rather rare (Cahn, 1929;  Ricker and Gottschalk, 1941; Thompson, 1941)-  Cahn (1929) described the  process of replacement of native gamefish by carp when conditions optimum for the gamefish were altered by the presence of carp.  The game fishes,  most of which had very strict environmental requirements, were unable to adapt to new conditions and consequently they were often completely replaced.  Ricker and Gottschalk (1941) showed in Bass Lake, Indiana, that  even partial removal of undesirable species bring about improvement in angling for desired species.  Van Oosten (1949) reported that in the Great  Lakes the coarse fish have failed to occupy a l l the niches left by the poorly managed and decreased populations of more desirable species.  Van  Oosten's report definitely shows that in a large lake, fishes can coexist i f there i s a slight displacement of the optima.  It seems probable that a  variously stratified environment as well as plentiful living space is the basic requirement for successful coexistence in larger lakes. The second type, in which the area i s shared without any changes in the optima, has been hardly discussed.  Fryer (1959 b) discusses the size  of Nyasa Lake as an important factor i n isolation of the fishes.  "Even  planktonic organisms (Diaptomus mixture and Daphnia humboltzi) which can easily be dispersed by currents, can be isolated.  It suggests that those  animals that are capable of resisting such chance dispersal are even more l i k e l y to be isolated as a result of the great size of the lake. could not occur in a small lake."  This  If there were partitions semi-closed by  such barriers as sand bars or bands of aquatic plants, coexistence by isolation would be made easier. Thus, lake size may play an important role as a factor affecting the  -124degree of interspecific competition.  In Nicola Lake the five species show  marked divergence i n feeding habits, as well as spatial occupation, during their f i r s t summer of l i f e .  Such a divergence, to a greater or similar  degree, may be expected among the adults, at least during the summer period when their growth rate i s at a maximum. Although convergence could be expected during the winter period, a lower metabolic rate, caused by a lowering of temperatures, may be able to reduce or eliminate any competition.  This has been demonstrated i n sculpins by Daiber ( 1 9 5 6 ) .  questions can be proposed.  Several  For examples, would these fish show similer  behavioral divergences in a body of water smaller i n size than Nicola Lake? On the other hand, i n a larger lake would there s t i l l be severe interspecific competition?  Would the squawfish and chub have to have a more or  less competitive relationship during the whole summer period? The positive correlation between surface area and number of the species coexisting indicates that the larger the lake the greater the possibility of coexistence between these species (Section VIII).  It also suggests that  in a smaller lake, potentially competitive species would be forced into closer association, and the situation would be resolved more often (or more quickly) than in larger lakes. In summary, the writer suggests that interspecific competition i s the reason why there i s a good positive correlation between the number of species of fish in a lake and the size of the lake.  This competition i s  less in large lakes because they usually show more varieties of habitats to choose from and they have a greater area for regional isolation to develop. It i s also possible that some other factors associated with size of lakes may be involved, for by virtue of size alone there are many more opportunities for vicissitudes of conditions which by their incidence may preserve  -125-  a competitive relationship that would otherwise be resolved.  XI.  1.  SUMMARY  Early l i f e history, distribution, movement, food habits and inter-  specific relations of five inshore species, largescale sucker (Gatostomus macrocheilus), northern squawfish (Ptychocheilus balteatus)» peamouth chub (Mylocheilus caurinum), redside shiner (Richardsonius balteatus), and prickly sculpin (Cottus asper), have been studied during the summers of 1959 - 1961 i n Nicola Lake, British Columbia. 2.  Analyses were based on specimens periodically sampled with three  types of seine nets from various inshore waters of the lake, observation of behaviour of the f i s h both i n nature and in aquaria, and study of plankton, bottom animals and temperature conditions. 3.  Morphological development of the fryof these five species was  described. 4.  Keys to postlaval and young fishes were represented.  Wherever the larvae hatched, f r y of a l l these species move  towards the head of the lake i n early summer, and later on they more or less diverged away from the head of the lake. 5.  Fry of a l l four cypriniform species showed similar diurnal move-  ment. They started to move into the shallow water at dawn and move out at dusk.  In the sculpin, fluctuations i n numbers near shore had no direct  correlation with time of a day. 6.  Although no species i s rigorously restricted to one habitat, i n  early summer the sucker, chub and squawfish prefer a sand habitat for living site, but i n later parts of summer i t diverges.  Sculpins prefer  weed beds i n mid- and late summer. 7.  A l l cypriniform species tend to stay i n the middle to top layer  -127rather than i n the bottom layer i n early summer, while i n mid- and late summer the suckers mostly stay i n the bottom layer but others rarely stay i n this layer i n nature.  The sculpin stay i n the bottom layer throughout  summer. Aquarium experiments agreed with these observations. 8. Aquarium experiment did not suggest any aggressive behaviour; nor did the presence of one species influence the vertical distribution of another. 9.  These similarities or differencies i n movement, distribution and  habitat preference are reflected by interspecific association among them. A close association among f r y of a l l species i n the jsarlycsummer gradually dissipated later on. 10.  In early summer they are typically plankton feeders, but towards  the end of summer their interspecific feeding relations gradually become less because of the divergence i n food preference, feeding place and feeding manner. These changes are i n turn largely due to morphological changes, i n particular those of feeding structures. 11.  Since the plankton resources seemed to be insufficient i n the  shallow inshore area, there may have been competition for food i n early summer. Moreover, the f r y may have been forced into severe competition by an early summer aggregation at the head of the lake as well as by similarity i n behaviour and habitat. 12.  An alternative approach to the problem of demonstrating  inter-  specific relationships was made from comparison of species associations i n lakes of the Fraser River drainage.  A positive correlation between the  surface area and the number of species suggests that the larger the lake, the greater the possibility of coexistence between these species, and that competition i n small lakes may be a factor i n eliminating some of the  -128-  species. 13.  These findings are discussed i n relation to the current contro-  versy concerning specialization of temperate and tropical freshwater fishes are affored the opportunity for specialization, whereas i n small or simple environments, more generalized behavior leads to competition between species.  XII.  LITERATURE CITED  Allee, W. C , Alfred E. Emerson, Orlando Park, Thomas Park, and Karl P. Schmidt. 1 9 4 9 . Principles of animal ecology. W. B. Saunders Co., Philadelphia. 8 3 7 p. A l l e n , K . R. 1 9 4 1 . Studies on the biology of the early stages of the salmon (Salmo salar). II. Feeding habits. J . Animal Ecol. 10:47-76.  A l i , M. Y.  1 9 5 9 . Spatial distribution of fish in summer in Nicola Lake, British Columbia. M. A. Thesis, Univ. British Columbia. 1 3 2 p.  Balinsky, B. I. 1 9 4 8 . On the development of specific characters in cyprinid fishes. Proc. Zool. Soc. London 1 1 8 ( 2 ) : 3 3 5 - 3 4 4 . Bennet, G. 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Kalleberg, H. 1958. Observation i n a stream tank of t e r r i t o r i a l i t y and competition in juvenile salmon and trout (Salmo salar L. and S. trutta L.). Rept. Inst. Freshwater Res., Drottningholm 39:5598.  -132Kawanabe, H. 1958. On t h e s i g n i f i c a n c e o f the s o c i a l s t r u c t u r e f o r t h e mode o f d e n s i t y e f f e c t on a s a l m o n - l i k e f i s h , "Ayu", P l e c o g l o s s u s a l t i v e l i s Temminck e t S c h l e g e l . Mem. C o l l . S c i . Univ. Kyoto, ( B ) , 26(TT: 253-268. Kawanabe, H. 1959- Food c o m p e t i t i o n among f i s h e s i n some r i v e r s o f Kyoto P r e f e c t u r e , Japan. I b i s 25:171-180. K e n d a l l , M. G. 1955• Rank c o r r e l a t i o n methods. London 196 p.  C h a r l e s G r i f f i n Co*  v  Lack, D.  1954- The n a t u r a l r e g u l a t i o n o f animal numbers. Oxford. 343 ?.  L a g l e r , K. F. 1944- Problems o f c o m p e t i t i o n and o r e d a t i o n . W i l d l i f e Conf. 9:212-219-  Clarendon  Press,  Trans. Am.  L a r k i n , P. A. 1956. I n t e r s p e c i f i c c o m p e t i t i o n and p o p u l a t i o n c o n t r o l i n freshwater f i s h e s . J . F i s h . Res. Bd. Canada 13(3):327-342. Leim, A. H. 1924. The l i f e h i s t o r y o f the shad ( A l o s a s a p i d i s s i m a ( W i l s o n ) ) w i t h s p e c i a l r e f e r e n c e t o t h e f a c t o r s l i m i t i n g i t s abundance. C o n t r i . Canadian B i o l . N. S. 2 ( P t . I):161-284. L i n d r o t h , A. 1955D i s t r i b u t i o n t e r r i t o r i a l behaviour and movements o f sea t r o u t f r y i n the R i v e r I n d a l s a l v e n . Rept. I n s t . Freshwater Res., Drottningholm 36:104-119 L i n d s e y , C. C. 1953V a r i a t i o n i n a n a l r a y count o f the r e d s i d e s h i n e r , Richardsonius paIteatug (Richardson). Canadian J . Z o o l . 31: 211-225• Lindstrom,  T. 1955- On t h e r e l a t i o n f i s h s i z e - food s i z e . Freshwater Res., Drottningholm. 36:133-147.  Rept. I n s t .  L o r z , H.  1962. S p a t i a l d i s t r i b u t i o n and spawning m i g r a t i o n o f kokanee (Oncorhynchus nerka) i n N i c o l a Lake, B r i t i s h Columbia. M. Sc. Thesis. Univ. B r i t i s h Columbia. 76 p.  MacArthur, R. H. 1958. P o p u l a t i o n e c o l o g y o f some w a r b l e r s o f n o r t h eastern coniferous f o r e s t s . E c o l o g y 39(4) '• 599-619. MacPhee, C. I960. P o s t l a r v a l development and d i e t o f the l a r g e s c a l e sucker, Catostomus m a c r o c h e i l u s , i n Idaho. Copeia 1960:119-125. MacLeod, J . C. I960. The d i u r n a l m i g r a t i o n o f peamouth chub M v l o c h e i l u s caurinum ( R i c h a r d s o n ) , i n N i c o l a Lake, B r i t i s h Columbia. M. Sc. Thesis. Univ. B r i t i s h Columbia. 54 p. Magnuson, J . J . 1961. An a n a l y s i s o f a g g r e s s i v e b e h a v i o r , growth, and c o m p e t i t i o n f o r food and space i n medaka ( O r y z i a s l e t i p e s ) P i s c e s , C y p r i n i d o n t i d a e . Ph. D. T h e s i s . Univ. B r i t i s h Columbia. 105 p.  -133Mathews, VI. H. 1944- Glacial lakes and ice retreat in south-central British Columbia. Trans Roy. Soc. Canada 38(4):39-57Miura, T. 1955• Seasonal trophic dynamics of an eel-grass community in Kasaoka Bay, Okayama Prefecture, Japan. M. Sc. Thesis. Univ. Kyoto. 87 p. ( In Japanese). Miura, T. 1959- Some ecological studies on fish populations in Lake Sagami, an impoundment, i n Kanagawa Prefecture, Japan. Bull. Freshwater Fish. Res. Lab. 9 ( 1 ) : 2 3 - 3 9 Miyadi, D., H. Kawabata and K. Ueda. 1952. Standard density of "Ayu", Plecoglossus a l t i v e l i s , on the basis of i t s behaviour and grazing unit in area. Contr. Physiol. Ecol. Kyoto Univ. 75:1-34- (In Japanese). Mizuno, N. et. a l . 1958. Life history of some stream fishes with special reference to four cyprinid species. Ibis 8 1 : 1 - 4 8 . (In Japanese) Morishita, M. 1959- Measuring of interspecific association and similarity between communities. Mem. Fac. Sci. Kyushu Univ. (E) 3 ( l ) : 6 5 - 8 0 . Myers, G. S. I960.  Fish evolution in Lake Nyasa.  Evolution 14(3):394-396.  Newman, M. A. 1956. Social behavior and interspecific competition in two trout species. Physiol. Zool. 29:64-81. Nilsson, Nils-Arvid. 1955- Studies on the feeding habits of trout and char in North Swedish Lakes. Rept. Inst. Freshwater Res., Drottningholm.  36:163-225.  Nilsson, N. 1956. Om konkurrensen i naturen. Cited from Kalleberg (1958).  Zoologisk Revy  1956:40-47.  Nilsson, Nils-Arvid. 1958. On the food competition between two species of Coregonus in a North-Swedish Lake. Ibis 36:146-161. Northcote, T. G. 1954- Observations on the comparative ecology of two species of fish, Cottus asper and Cottus rhotheus, in British Columbia. Copeia 1954:25-28. Northcote, T. G. and G. F. Hartman. 1959- A case of "schooling" behavior in the prickly sculpin, Cottus asper Richardson. Ibis 1959:156158.  Park, T. 1954. Experimental studies of interspecies competition II. Temperature, humidity and competition in two species of Tribolium. Physiol. Zool. 27(3):177-238. Pritchard, A. C. 1930. Spawning habits and fry of the cisco (Leucichthys artedi) in Lake Ontario. Contr. Canadian Biol, and Fish N. S. 6(9):225-240.  -134Rawson, D. S. 1934P r o d u c t i v i t y s t u d i e s i n Lakes o f the Karaloops r e g i o n , B r i t i s h Columbia. B u l l . B i o l . Bd. Canada 42:1-31R e i d , Or. D. 1961. E c o l o g y o f i n l a n d water and e s t u a r i e s . P u b l i s h i n g C o r p o r a t i o n , New York. 375 P-  Reinhold  R i c k e r , W. E. and J . G o t t s c h a l k . 1941An experiment i n removing coarse f i s h from a l a k e . Trans. Am. F i s h . Soc. 70:382-390. R o u n s e f e l l , G. A. and W. H. E v e r h a r t . 1953F i s h e r i e s s c i e n c e i t s method and a p p l i c a t i o n s . John W i l e y & Sons, Inc., New York. 444 PSnedecor,  G. W.  1959-  S t a t i s t i c a l methods a p p l i e d t o experiments i n  a g r i c u l t u r e and b i o l o g y 5th ed.  Iowa S t a t e C o l l . P r e s s , Ames  534 PSpoor, W. A. and C. L. Schoemer. 1938- D i u r n a l a c t i v i t y o f the common sucker (Catostomus commersoni Lac) and t h e rock bass ( A m b l o p l i t i s r u p e s t r i s Rafinesque) i n Maskellunge Lake. Trans. Am. F i s h . Soc.  68:211-220.  S t a r r e t , W. C. 1950- Food r e l a t i o n s h i p o f t h e minnows o f the Des Moines R i v e r , Iowa. E c o l o g y 31:216-233'Stewart, N. H. 1926. Development, growth and food h a b i t s o f t h e white sucker, Catostomus commersonii Le Sueur. B u l l . U. S. Bur. F i s h . 42:147-184Svardson,  G.  1949- Competition and h a b i t a t s e l e c t i o n i n b i r d s .  Oikos  1:157-174Swingle,  H. S. 1950R e l a t i o n s h i p s and dynamics o f balanced and unbalanced f i s h p o p u l a t i o n . Alabama Agr. Exp. S t a . B u l l . 274:1-74-  Thompson, D. H. 1941The f i s h p r o d u c t i o n o f i n l a n d streams and l a k e s . In a Symposium on H y d r o b i o l o g y , Univ. Wisconsin P r e s s , Madison: 206-  217-  Tokuda, M. 1954- E v o l u t i o n . Japanese).  Iwanami P r e s s Co., Tokyo.  392 p. ( I n  Udvardy, M. D. F. 1959- Notes on t h e e c o l o g i c a l concepts o f h a b i t a t , b i o t o p e and n i c h e . E c o l o g y 40:725-728. U t i d a , S.  1953I n t e r s p e c i f i c c o m p e t i t i o n between two s p e c i e s o f bean w e e v i l . E c o l o g y 34:301-307-  Van Oosten, J . 1949- The present s t a t u s o f the United S t a t e s commercial f i s h e r i e s o f the Great Lakes. Trans. N. A. W i l d l i f e Conf. 14:  319-329-  W i e s e l , G. F. and H. W. Newman. 1951Breeding h a b i t s , development and e a r l y l i f e h i s t o r y o f R i c h a r d s o n i u s b a l t e a t u s , a northwestern minnow. Copeia 1951:18' -194-  -135Wenn, H. E. and R. R. Miller, 19'5A- Native postlarval fishes of the lower Colorado River basin, with a key to their identification. Calif. Fish; and Game 40(3) : 273-285.  -136Appendix Table.  Surface areas and number of species of Catostomidae, Cyprinidae and Cottidae of 36 lakes of the Fraser River Drainage. J3 (0 •rl  u  u  Shuswap Canim Sheridan Culculz Nicola Lac La Hache Tachick Nulki Horse Shamway Spout Dragon Cultus White Nadsilnick Chimney Bouchie Eulutazella Timothy Tyee McLease Watch Heffley Pinaus Dempsey Echo Alleyne Brenda Pillar Silver Schkam Fa wi Squakam Twine Welcome Mike  78,720 20,237 10,063 6,223 6,041 5,685 5,442 4,080 2,872 2,285 1,695 1,627 1,504 1,381 1,224 1,218 1,168 1,100 1,098 1,012 841 646 501 417 339 174 135 117 107 99 98 80 64 49 11 10  (0 O  CO CU 60 U  o  10  CO CQ O e  3. (0 co •p •H  g  X!  to  •a rl  H  CO t>0  5b c •rl  x  CO  o  in  a>  u  A!  T3  Br  U (0  CO H  u  Lo  CD •—N -(-, co CO ?> co o  3 CO  on  CO  cu  CO  X X X  cc-  T!  a  u  8  CO TJ  I  Cr  co  E  co  x:  Xi  3  3  x;  o  x;  8  u o  CO CO CL,  s  X! O• x: +5  CO 0  T3  I  X! O  (O •rl  CO  "E S  CO  x: o  3  X  X X X  X  X X X  X X  X X X X X  X X X X X  X X X X - X X X X X X X X X  X X X X  X X X  X X X X  X X X X  X X X X  X X  X  X X  X  X  X X X  X X X X X X  X X X X X X X  X  X X  X  X X  X X X X  o CO  o CO  u  •rl Si  ? ?  X X  X  X X X X X  D. H  3  X  X  X  1 I  a  H  a.  X X X  X  CO  c •c •rl  •rl  3 3 3  X  X  TJ  XI  X  X  CO  CO o (0  3  X X X X X X  X  X  •rl  Re  CO  M u  X X X X X  X X  X X X  X X  X X  X  X X  X X X  X  X  X  3  c  rO •rl •P  3  

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