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Aspects of the life-history of Cymatogaster aggregata Gibbons Gordon, Charles Douglas 1965

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ASPECTS OF THE LIFE-HISTORY OF CYMATOGASTER AGGREGATA GIBBONS  by  CHARLES DOUGLAS GORDON B.Sc,  The U n i v e r s i t y of B r i t i s h Columbia, 1963  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i  i n the Department of Zoology  We accept t h i s  t h e s i s as conforming to the  r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA NOVEMBER, 1 9 6 5  In the  requirements  British  for  Columbia,  available mission  for  for  purposes his  presenting  reference  extensive  without  this  copying  my w r i t t e n  Department  by  It  thesis  for  of  Jl  jjO  7  at  the Library  of  I  this  t h e Head  of  the University  of  shall  further thesis  of  is understood financial  fulfilment  O  that  gain  for  shall  Columbia  f*?  agree  6  it  that  freely per-  scholarly  copying  L-O&Y'  lt&i/LAA-^A^1  C  make  my D e p a r t m e n t  permission.  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada Date  that  in p a r t i a l  degree  and s t u d y .  may b e g r a n t e d  of  thesis  an advanced  I agree  representatives,,  cation  this  not  or or  be  by publi-  allowed  ii ABSTRACT  Age and growth of the s h i n e r perch, Cymatogaster aggregata Gibbons, were analysed with the a i d of s c a l e s taken from f i s h o b t a i n e d at Keates I s l a n d , B r i t i s h i n 1963 and 1964.  Columbia,  Cymatogaster e x h i b i t s a r e l a t i v e l y con-  s t a n t r e l a t i o n s h i p between s c a l e growth and increment of body l e n g t h throughout i t s l i f e  and based on t h i s observa-  t i o n a new method of b a c k - c a l c u l a t i o n was developed. s c a l e s of Cymatogaster may of  have up to three d i f f e r e n t types  checks, b i r t h checks o r metamorphic  checks, and a n n u l i .  The  annuli,  spawning  The h i g h e s t l e v e l s of instantaneous  growth r a t e s o c c u r r e d d u r i n g the s p r i n g and e a r l y summer, between the time of f o r m a t i o n of an annulus and the f o l l o w i n g spawning check.  I t i s d u r i n g t h i s p e r i o d that water  atures reach a maximum and food i s most abundant.  temper-  The lowest  instantaneous growth r a t e s o c c u r r e d d u r i n g the f a l l  and win-  t e r months between the f o r m a t i o n of a spawning check and the f o l l o w i n g annulus. Seasonal and d i u r n a l movement p a t t e r n s e x h i b i t e d by Cymatogaster were s t u d i e d by means of e x t e n s i v e g i l l net s e t s i n 1963 and 1964 at the Keates I s l a n d study area. fish first  moved i n t o the area i n e a r l y June and l e f t  by mid-October. ter  The again  In June, j u s t p r i o r to spawning, Cymatogas-  e x h i b i t e d a p a t t e r n of d i u r n a l movement that  involved  m i g r a t i o n from deep to shallow water d u r i n g the day, and from  iii  shallow t o deeper water at n i g h t . there was Light  A f t e r the spawning p e r i o d  a complete r e v e r s a l of the d i u r n a l movement  pattern.  i n t e n s i t y appeared t o be the most important f a c t o r  governing the onshore and  o f f s h o r e movements of Cymatogaster.  Stomach content a n a l y s i s i n d i c a t e d that by volume, mussels and  algae were the most important items i n the  diet  of Cymatogaster, although b a r n a c l e s and zooplankton were sometimes eaten i n l a r g e q u a n t i t i e s .  Y e a r l i n g Cymatogaster  f e d a c t i v e l y throughout the time they were present i n the study area but mature f i s h e x h i b i t e d  a marked r e d u c t i o n  feeding  during the spawning p e r i o d .  The  i n g was  governed p r i m a r i l y by  associated with sunrise,  and  i n i t i a t i o n of  an i n c r e a s e  feed-  in light intensity  l i t t l e or no f e e d i n g  d u r i n g the hours of darkness.  of  occurred  Data i n d i c a t e d that the  rate  of passage of food through the d i g e s t i v e t r a c t v a r i e d between adults  and y e a r l i n g s , as w e l l as The  and  seasonally.  r e l a t i o n s h i p s between age  d i u r n a l movement p a t t e r n s ,  and  and  feeding  growth, s e a s o n a l habits  p r e f e r e n c e s of Cymatogaster were c o r r e l a t e d and f a c t o r s of the p h y s i c a l and  biotic  environment.  and  food  r e l a t e d to  iv TABLE OF CONTENTS Page TITLE PAGE  1  ABSTRACT  1  1  TABLE OF CONTENTS  iv  LIST OF FIGURES  vi  LIST OF TABLES  ix  ACKNOWLEDGEMENTS  x  INTRODUCTION  1  MATERIALS AND METHODS  3  AGE AND GROWTH  4  S c a l e Formation and S t r u c t u r e of the S c a l e . . . .  5  Check I d e n t i f i c a t i o n  10  Back-Calculation  15  Lee's Phenomenon  20  Age  24  at M a t u r i t y  Fecundity  25  Instantaneous Growth Rates  26  Length-Weight R e l a t i o n s h i p s  33  SEASONAL AND DIURNAL MOVEMENT PATTERNS Seasonal Movements  36 38  Scuba D i v i n g O b s e r v a t i o n s . . .  40  G i l l Net Data  43  Tagging R e s u l t s  47  D i u r n a l Movements  50  . Adult F i s h  51  . Yearling Fish  54  V  SEASONAL AND DIURNAL FEEDING HABITS AND FOOD PREFERENCES  57  Seasonal Feeding H a b i t s  57  D i u r n a l Feeding H a b i t s  63  DISCUSSION  76  C o r r e l a t i o n o f Age and Growth, Movement, and Stomach Content A n a l y s i s Data  81  SUMMARY  85  LITERATURE CITED  88  vi  L I S T OF FIGURES Page Figure  Figure  Figure  Figure  Figure  Figure  Figure  Figure Figure Figure Figure  Figure  1.  2.  3.  4.  5.  6.  7.  8. 9. 10. 11.  12.  R e l a t i o n s h i p o f body l e n g t h t o a n t e r i o r s c a l e r a d i u s o f b o t h male and f e m a l e Cymatogaster  5  E p i d e r m i s of a 2.4 cm. embryo, c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , s h o w i n g no e v i d e n c e o f s c a l e f o r m a t i o n  7  E p i d e r m i s o f a 2.6 cm. embryo, c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , s h o w i n g evidence of s t a i n a b l e material i nthe s c a l e pocket  7  E p i d e r m i s o f a 2.7 cm. embryo, c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , s h o w i n g f i r s t c i r c u l i l a i d down  8  E p i d e r m i s o f a 4.3 cm. embryo j u s t b e f o r e b i r t h , c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , s h o w i n g f u l l y f o r m e d and o v e r lapping scales  8  Photograph showing c o n c e n t r i c r i n g s o f c i r c u l i s u r r o u n d i n g t h e f o c u s and c o n t i n u i n g o u t t o t h e l e a d i n g edge o f t h e scale  17  P h o t o g r a p h s h o w i n g l a r g e d i s t a n c e between a n n u l u s I and l e a d i n g edge o f s c a l e i n d i c a t i n g Spawning C h e c k I I w i l l n o t be l a i d down. (Scale taken from specimen capt u r e d i n l a t e September)  17  Typical scale year o f l i f e  17  of Cymatogaster  Scale of y e a r l i n g f i s h just t i o n o f Spawning Check I I  i n fourth  after  P h o t o g r a p h s h o w i n g s c a l e where C h e c k I I was n o t l a i d down  forma17  Spawning 17  P o i n t s o f i n t e r c e p t i o n on t h e r e g r e s s i o n l i n e o f t h e B i r t h Check, Spawning C h e c k s , and A n n u l i f o r male C y m a t o g a s t e r  19  P o i n t s o f i n t e r c e p t i o n on t h e r e g r e s s i o n l i n e o f t h e B i r t h Check, Spawning C h e c k s , and A n n u l i f o r f e m a l e C y m a t o g a s t e r  19  vii Page F i g u r e 13. F i g u r e 14. F i g u r e 15.  -Figure 16.  F i g u r e 17.  F i g u r e 18.  F i g u r e 19.  F i g u r e 20.  F i g u r e 21. F i g u r e 22. F i g u r e 23. F i g u r e 24. F i g u r e 25. F i g u r e 26. F i g u r e 27.  C a l c u l a t e d length at the end of each year of l i f e .  21  P l o t s of average instantaneous d a i l y growth r a t e s between A n n u l i  28  P l o t s of average instantaneous d a i l y growth r a t e s between A n n u l i and Spawning Checks....  .28  Average instantaneous monthly growth r a t e s e x h i b i t e d by each age c l a s s of male Cymatogaster  32  Average instantaneous monthly growth r a t e s e x h i b i t e d by each age c l a s s of female Cymatogaster  32  Comparison of the body length - body weight r e l a t i o n s h i p of immature and pregnant f i s h w i t h mature f i s h a f t e r g i v i n g birth  34  Comparison o f the body length - body weight r e l a t i o n s h i p before and a f t e r Spawning Check f o r m a t i o n i n male Cymatogaster  34  I l l u s t r a t i o n showing Keates I s l a n d study area i n c l u d i n g h a b i t a t areas and p o s i t i o n of g i l l net s t r i n g s  37  Seasonal r e l a t i v e abundance y e a r l i n g Cymatogaster  45  of a d u l t and  Seasonal r e l a t i v e abundance of mature male and female Cymatogaster  45  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of y e a r l i n g Cymatogaster  46  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of mature male Cymatogaster  46  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of mature female Cymatogaster  46  D i u r n a l movement p a t t e r n s of mature Cymatogaster i n June  52  D i u r n a l movement p a t t e r n s of mature Cymatogaster i n J u l y  52  viii  Page  F i g u r e 28.  D i u r n a l movement p a t t e r n s of mature Cymatogaster i n August  F i g u r e 29.  D i u r n a l movement p a t t e r n s of y e a r l i n g Cymatogaster i n June  55  D i u r n a l movement p a t t e r n s of y e a r l i n g Cymatogaster i n J u l y  55  D i u r n a l movement p a t t e r n s of y e a r l i n g Cymatogaster i n August  55  Volume and composition of food organisms i n the g a s t r o - i n t e s t i n a l t r a c t at r e g u l a r i n t e r v a l s from June t o October  59  The four s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of Cymatogaster  65  Volume and composition of food organisms i n the four s e c t i o n s of the g a s t r o i n t e s t i n a l t r a c t of mature male Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August  66  Volume and composition of food organisms i n t h e four s e c t i o n s of the g a s t r o i n t e s t i n a l t r a c t of mature female Cymatogaster over 24 hour p e r i o d s i n June! J u l y , and August  68  Volume and composition of food organisms i n the four s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of y e a r l i n g male Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August  70  Volume and composition of food organisms i n the four s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of y e a r l i n g female Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August  72  F i g u r e 30. F i g u r e 31. F i g u r e 32.  F i g u r e 33. F i g u r e 34.  F i g u r e 35.  F i g u r e 36.  F i g u r e 37.  52  ix  LIST OF TABLES Page Table I T a b l e II  Distance between B i r t h Checks, Checks, and A n n u l i  Spawning 12  Average d i s t a n c e from focus of s c a l e t o each s u c c e s s i v e check  14  Average b a c k - c a l c u l a t e d body l e n g t h at time of formation of each check  14  Comparison of average b a c k - c a l c u l a t e d body l e n g t h at time of f o r m a t i o n of each check with a c t u a l body lengths  22  Table V  Length d i s t r i b u t i o n of age groups  23  Table VI  Average number of embryos c a r r i e d by  Table I I I Table IV  adult female Cymatogaster  25  T a b l e VII  Tag r e c o v e r y r e s u l t s  48  Table VIII  T o t a l percentage of t a g r e c o v e r i e s  50  T a b l e IX  P o s i t i o n of tagged f i s h r e c o v e r i e s  50  X  ACKNOWLEDGEMENTS  The author wishes t o express h i s g r a t i t u d e t o Dr. N. J . Wilimovsky who suggested the problem and who gave many worthwhile comments and c r i t i c i s m s i n t h e w r i t i n g of t h i s paper. Lindsey,  S p e c i a l thanks are a l s o due t o Dr. C. C.  Dr. P. A. Dehnel, Dr. I. E. E f f o r d and Dr. J . T.  i'  ,\;  McFadden f o r t h e i r  assistance  i n the preparation  of the  thesis. The author i s indebted  t o Mr. D. T a y l o r , Mr. J .  Hutton, Mr. A. Webster, Mr. F. F r a s e r , others  and t o t h e many  f o r t h e i r a s s i s t a n c e i n f i e l d work.  The w r i t e r  e s p e c i a l l y wishes t o express h i s a p p r e c i a t i o n t o Mr. K. Gay who gave l i b e r a l l y of h i s time and c r i t i c i s m i n the f i e l d . The problem was supported by a r e s e a r c h Dr. Wilimovsky.  grant t o  1 INTRODUCTION  The s h i n e r seaperch, Cymatogaster aggregata, member,of the Family Embiotocidae  is a  and i s abundant along the  P a c i f i c Coast of North America from Alaska t o C a l i f o r n i a . Since l i t t l e was known about the l i f e h i s t o r y of t h i s  fish,  a r e s e a r c h program was s e t up t o a s c e r t a i n the s c a l e growth - body length r e l a t i o n s h i p , the nature of d i f f e r e n t  checks  found on the s c a l e s , whether or not Lee's phenomenon i s p r e s e n t , and the instantaneous growth r a t e s e x h i b i t e d by Cymatogaster d u r i n g d i f f e r e n t stages of i t s l i f e . and 1964, experiments  were conducted  t o determine  In 1963 i f Cymato-  gaster e x h i b i t e d any pronounced s e a s o n a l or d i u r n a l movement p a t t e r n s , and stomach contents were analysed t o a s c e r t a i n f e e d i n g h a b i t s and food p r e f e r e n c e s . The Family Embiotocidae, is  which e x h i b i t s  viviparity,  found e x c l u s i v e l y i n the c o a s t a l waters of the North P a c i -  fic.  Since 1853, when A g a s s i z f i r s t  d e s c r i b e d the Family, a  c o n s i d e r a b l e amount of r e s e a r c h a s s o c i a t e d w i t h v i v i p a r i t y has been conducted little  has been p u b l i s h e d r e l a t i n g t o e c o l o g i c a l aspects of  i t s members and  on many of i t s s p e c i e s , however, very  l i f e histories.  Hubbs (1921) s t u d i e d the ecology  l i f e h i s t o r y o f Amphigonopterus aurora and other  parous perches of C a l i f o r n i a .  vivi-  Hubbs and Hubbs (1954) con-  ducted r e s e a r c h on s e v e r a l aspects of the l i f e h i s t o r y of  2  another Embiotocid, B r a c h y i s t i u s  frenatus.  w o r k e d on t h e age and g r o w t h o f C y m a t o g a s t e r Sivalingam otoca  Suomela  (1931)  a g g r e g a t a , and  (1956) p u b l i s h e d on t h e age and g r o w t h o f T a e n i -  lateralis.  Carlisle,  Schoth,  and Abramson  (1960),  conducted  a s t u d y on t h e B a r r e d S u r f p e r c h ( A m p h i s t i c h u s  argenteus  Agassiz) i n Southern C a l i f o r n i a .  Wilby the that  (1961) summarize e s s e n t i a l l y  life  histories  are found o f f the coast of B r i t i s h  relate  the r e l a t i o n s h i p s  an a t t e m p t  p r e f e r e n c e s of Cymatogaster and b i o t i c  Columbia. has b e e n made t o c o r -  and f e e d i n g h a b i t s  and r e l a t e  environment.  about  Embiotocidae  between age and growth,  d i u r n a l movement p a t t e r n s ,  the p h y s i c a l  i s known  o f t h e members o f t h e F a m i l y  In t h e d i s c u s s i o n  and  a l l that  Clemens and  seasonal and f o o d  them t o f a c t o r s o f  3  MATERIALS AND METHODS  The which  present  s t u d y was c o n d u c t e d  at Keates  i s l o c a t e d a t t h e e n t r a n c e t o Howe Sound.  d e s c r i p t i o n o f t h e research area at Keates  Island,  A detailed  Island i s given  at t h e b e g i n n i n g o f t h e t h e s i s s e c t i o n on s e a s o n a l and d i u r n a l movements.  The s t u d y a r e a i n c l u d e d w i t h i n i t t h r e e  relatively distinct  h a b i t a t areas; r e e f f a c e s , k e l p beds,  and o p e n w a t e r .  Specimen c o l l e c t i o n s  o b s e r v a t i o n s w e r e made t h r o u g h o u t  and Scuba  1963 a n d 1964.  were c a p t u r e d by t h e u s e o f e i t h e r n y l o n lampara  diving  gill  A l l fish  nets or a  s e i n e and were p r e s e r v e d i n a s o l u t i o n o f 10% forma-  lin. The  study of the l i f e  h i s t o r y of Cymatogaster  includes three r e l a t i v e l y d i s t i n c t and  growth,  a r e a s o f r e s e a r c h ; age  s e a s o n a l a n d d i u r n a l movement p a t t e r n s , a n d  f e e d i n g h a b i t s and f o o d p r e f e r e n c e s .  At t h e b e g i n n i n g of  each o f these t h r e e separate s e c t i o n s o f t h e t h e s i s ,  a  d e t a i l e d d e s c r i p t i o n i s g i v e n o f t h e m a t e r i a l s a n d methods used f o r each i n d i v i d u a l  study.  4  AGE  Age of 603 f i s h .  AND GROWTH  and growth c a l c u l a t i o n s were made f o r a t o t a l A l l specimens were o b t a i n e d from the Keates  I s l a n d study area at r e g u l a r October  to  i n 1963„ A key s c a l e was  fish,  i n t e r v a l s through May  and was  chosen, on the l e f t s i d e of the  l o c a t e d by c o u n t i n g 10 s c a l e s p o s t e r i o r l y  along the l a t e r a l l i n e , then 3 s c a l e s v e n t r a l l y .  If t h i s  key s c a l e proved to be regenerated, then the s c a l e a t e l y p o s t e r i o r was  used.  Measurements were made of two s c a l e s c a l e length s h i p was  and a n t e r i o r s c a l e r a d i u s .  found between the body length  dimensions,  A linear  and  logarithmic  p l o t s , f o r both sexes, throughout the e n t i r e l i f e  history  For the purpose of b a c k - c a l c u l a t i o n ,  measurement of a n t e r i o r s c a l e r a d i u s was  chosen.  g i v e s the r e l a t i o n s h i p between body l e n g t h scale radius  relation-  of the f i s h and the  two s c a l e measurements, on both a r i t h m e t i c  of Cymatogaster.  immedi-  and  f o r male and female Cymatogaster.  l i n e s were p l o t t e d f o r the body length t i o n s h i p , and very l i t t l e  Figure  Regression rela-  found between male  and female f i s h with r e g a r d t o s c a l e growth and body increment  1  anterior  - scale radius  d i f f e r e n c e was  the  length  (Y = 1.8122 + 2.1086 X f o r males, Y = 1.7288 +  2.1086 X f o r females, and Y = 1.7720 + 2.0983 X f o r  com-  5  0  F i g u r e 1.  1  2  3  4  ANTERIOR  SCALE  RADIUS  5  (cm  x  6  22)  R e l a t i o n s h i p o f body l e n g t h t o a n t e r i o r s c a l e r a d i u s o f b o t h m a l e and f e m a l e C y m a t o g a s t e r .  6  bined  m a l e s and  females).  S c a l e F o r m a t i o n and  Structure  of the  Scale  Cymatogaster are s c a l e l e s s u n t i l proximately  2.5  cm.  (Figure 2).  of s t a i n a b l e m a t e r i a l s t a r t s Figure has  been l a i d  there  down.  At t h i s t i m e t h e  i n the  4 shows an embryo o f 2.7 A f t e r the  s c a l e pocket  cm.  where t h e  first  with scales  at w h i c h t i m e t h e  (Figure  The at the  circuli  surrounding  first  i n the  center. the  There are  The  f i e l d s of the  (Figure  6).  E x a m i n a t i o n of the  scale  are  circuli  close together  also concentric  circuli  covered  rings to  of  the  a number o f c h e c k s p r e s e n t w h e r e and  there  s c a l e s of C y m a t o g a s t e r are u s u a l l y not t i n g u i s h e x c e p t i n c a s e s where t h e  s m a l l ; thus the  out  which i s  extend through a l l  d i s c o n t i n u i t y because of b r o k e n c i r c u l i .  The  poc-  s c a l e s of mature Cymatogaster  shows t h a t t h e r e are v e r y  circuli  formed,  embryo i s f u l l y  focus which continue  scale.  scale  3).  5) .  l e a d i n g edge o f t h e  v a n c e d age.  (Figure  s c a l e s of C y m a t o g a s t e r have a f o c u s ,  roughly  ap-  deposition  c i r c u l u s has  i s c o n t i n u o u s d e p o s i t i o n of c i r c u l i  ket u n t i l b i r t h ,  a l e n g t h of  i s evidence The  f i s h had  of  c h e c k s on  too d i f f i c u l t  growth increments of the  the  to  r e a c h e d an  older f i s h  c h e c k s a r e much c l o s e r t o g e t h e r  and  the disad-  are much  Figure  2.  Epidermis of a 2.4 cm. embryo, c l e a r e d i n KOH and s t a i n e d with a l i z a r i n , showing no evidence of scale formation.  Figure  3.  Epidermis c f a 2.6 cm. embryo, c l e a r e d i n KOH and s t a i n e d with a l i z a r i n , showing evidence of s t a i n able m a t e r i a l i n the s c a l e pocket.  F i g u r e 4.  Figure  5.  E p i d e r m i s o f a 2.7 cm, embryo, c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , showing f i r s t c i r c u l i l a i d down.  E p i d e r m i s o f a 4 . 3 cm. embryo j u s t b e f o r e c l e a r e d i n KOH and s t a i n e d w i t h a l i z a r i n , f u l l y f o r m e d and o v e r l a p p i n g s c a l e s .  birth, showing  9 harder t o d i s t i n g u i s h . In v i v i p a r o u s f i s h e s the i n t e r r u p t i o n of the regular  l a y i n g down of c i r c u l i , as evidenced by checks on the  s c a l e , may be a t t r i b u t e d t o one of t h r e e main f a c t o r s :  the  temporary r e t a r d a t i o n of growth caused by change i n e n v i r o n ment and mode of f e e d i n g a f t e r b i r t h - a metamorphic  annulus  (Hubbs 1921) or b i r t h check, the slowing down of growth i n the  winter - an annulus, or by growth r e t a r d a t i o n due t o  some s t r e s s a s s o c i a t e d w i t h r e p r o d u c t i o n - a spawning check. The great m a j o r i t y of young of the year f i s h had no check of any k i n d formed on t h e i r s c a l e s by the time they l e f t t h e study area (before mid-October), and, every one of the  y e a r l i n g f i s h had at l e a s t one check on t h e i r s c a l e s by  the  time they r e t u r n e d t o the study area (by the end of May).  The check c l o s e s t t o the l e a d i n g edge of the s c a l e was p r e sumably  an annulus. More and more c i r c u l i were l a i d down d u r i n g the  summer and the d i s t a n c e from the l a s t edge of the s c a l e i n c r e a s e d .  check t o the l e a d i n g  By mid-August,  another check had  been l a i d down by the great m a j o r i t y of f i s h of both sexes. the  males, a few had formed t h i s check by the end of June,  the  m a j o r i t y , however, formed i t i n the l a s t  e a r l y August. until  part of J u l y or  The females i n v a r i a b l y d i d not form a check  l a t e J u l y or e a r l y August.  The check formed i n l a t e  summer i s apparently a s s o c i a t e d w i t h r e p r o d u c t i o n and thus  In  10  t h i s check can be termed a spawning In check was T h i s was  approximately 1% of the sample,  a definite  observed on the s c a l e s of young of the year f i s h . i n t e r p r e t e d as a b i r t h check or metamorphic  A l s o , i n 1.5% of the sample, d u r i n g the f i r s t  Check  check.  a spawning check was  summer of the f i s h e s  annulus.  formed  life.  Identification  Three methods were used t o t r y t o d i s t i n g u i s h between b i r t h checks, spawning checks, and a n n u l i . was  The  first  d i r e c t o b s e r v a t i o n of the time of check f o r m a t i o n .  The  second was the v i s u a l appearance of the p h y s i c a l f e a t u r e s of the  check.  The t h i r d method i n v o l v e d a study of the d i s -  tance from the f o c u s t o each s u c c e s s i v e check. A l l t h r e e types of checks were found t o be similar in their  appearance.  quite  A l l t h r e e checks, i n the  m a j o r i t y of cases, were continuous around the focus of the scale. the  A l l t h r e e were u s u a l l y c o n c e n t r i c w i t h the margin of  s c a l e and were u s u a l l y q u i t e d i s t i n c t  and e a s i l y r e c o g -  n i z e d as a check. There are, however, s e v e r a l p h y s i c a l f e a t u r e s that may  a i d i n the i d e n t i f i c a t i o n of the d i f f e r e n t type of checks. A n n u l i and B i r t h 1.  Checks  An'annulus never meets another annulus.  11  2.  3.  The  check i s d e f i n i t e l y  the  margin of the  There  i s usually  scale. a great  r u p t i o n of the c i r c u l i  Spawning 1.  edge o f t h e c h e c k t e n d s t o be  broken.  Checks c h e c k s sometimes  There i s u s u a l l y  ior  scale  direct the  relationship  of each check.  could  between body  between body  length,  If this  ing  every y e a r l i n g  to  headed  fish  had f o r m e d  scales  formed  on t h e s c a l e s  A^,  e a c h s u c c e e d i n g c h e c k was  done f o r 539  antera from  forma-  demonstrated,  check.  a l t e r n a t e d w i t h spawning  w i t h t h e column  and  the distance  r e l a t i o n s h i p were  d u r i n g t h e summer, p r e s u m a b l y annuli  length  There i s  and t h e t i m e o f  and t h e l a r g e m a j o r i t y o f t h e s e f i s h  fish,  cir-  distinguish  1 ) , t h e r e f o r e t h e r e s h o u l d be  show t h e n a t u r e o f e a c h Since  i n t e r r u p t i o n of  c h e c k s , and a n n u l i .  f o c u s t o each s u c c e e d i n g check,  tion it  relationship (Figure  less  u s e d t o attempt t o  checks, spawning  radius  annulus  t h a n i n an a n n u l u s .  A t h i r d method was  line  meet an  i t s base.  culi  a straight  inter-  leading  at  between b i r t h  d e a l of  as t h e  Spawning  2.  concentric with  an a n n u l u s ,  a spawning of the  checks.  older  Usually  the d i s t a n c e from the  recorded, (Table I ) .  and t h e a v e r a g e was  check  start-  focus  This  was  taken f o r each of the  Table I.  Distances between B i r t h Checks, Spawning Checks and A n n u l i .  Number  BC  1 2 3 4 5 6  SC j  Al  2.2  2.5 2.8 2.6  2.7  2.6  1.8  2.7 2.7 2.7  7  8 9 10 11 12 13 14 15 16  **  2.3  2.2  Missed  SCJU  Missed  SCJI  £  2.8 2.6 2.6 2.8 2.8 2.6 2.5 3.0  s e n  3.4 3.5 3.5 3.3 3.4 3.3 3.4 3.1 3.0 3.4 3.5  **  3.3 3.2  A  2  3.9 3.6 3.9  3.7 3.7 3.5 3.4  3.7 3.8 3.9  3.7 3.4  BC = B i r t h Check SC = Spawning Check A = Annulus  S C i u  4.3 4.0 4.2 3.9  *  4.2 4.1 4.2 3.9 3.6  A3  SC  4.5 4.3 4.2 4.5 4.3 4.5 4.0  4.6 4.8 4.5  3.7  I V  4.7 4.3 3.9  A  4  4.6 4.9 4.5 4.2  4.7 4.3  13 columns.  The f i g u r e s gave an average d i s t a n c e from the  focus of the s c a l e t o each b i r t h check, spawning check and annulus (Table I I ) . Except f o r the b i r t h check and spawning check I, the average d i s t a n c e from the focus t o each check was g r e a t e r f o r the females than f o r the males. In a few cases, the d i s t a n c e between two checks was very much g r e a t e r than the average.  This  indicated  e i t h e r a very h i g h growth r a t e d u r i n g that p a r t i c u l a r or a check that f a i l e d t o form.  period  In some cases, the d i s t a n c e s  between checks were much higher than average, but these d i s tances were p r o p o r t i o n a l .  Apparently these p a r t i c u l a r  had a higher than average r a t e of growth.  fish  In other cases,  however, t h e r e were i n s t a n c e s where the d i s t a n c e between two checks was much g r e a t e r than average, but the d i s t a n c e s between the remaining checks were normal. that a check had f a i l e d t o form.  This  indicated  Since every y e a r l i n g  f i s h had an annulus, i f a check was missed, i t would p r e sumably be a secondary or spawning check. from Cymatogaster  Scale  samples  j u s t p r i o r t o the time of departure  from the study area ( l a t e September) confirmed that a very few of these f i s h f a i l t o form a spawning check.  At t h i s  time t h e d i s t a n c e from the l a s t annulus t o the l e a d i n g edge of the s c a l e was almost as great as the average d i s tance from that annulus t o the one that w i l l be formed i n the coming winter (Figure 7 ) , t h e r e f o r e i f a check were  T a b l e I I . Average D i s t a n c e from Focus of S c a l e t o each S u c c e s s i v e  Sex  BC  SCj  Ai  SCjj  A  rf  1.90  2.36  2.62  3.20  3.64  3.91  4.12  4.28  4.52  4.70  9  1.82  2.13  2.67  3.39  3.81  4.06  4.33  4.48  4.70  4.85  Table I I I .  Sex  2  S  C  m  Check.  A  3  S  C  i v  A  4  S C  V  Average B a c k - C a l c u l a t e d Body L e n g t h a t Time o f F o r m a t i o n o f each Check.  SCj  Ai  SCjj  A  o*  5.9  6.7  7.3  8.8  9.6  10.3  10.8  11.1  11.5  12.0  9  5.6  6.3  7.4  9.0  9.9  10.5  11.0  11.4  11.8  12.4  S 2  C  III  A  3  i v  BC  S  C  A  4  S C  V  15  going to be formed, i t should a l r e a d y be p r e s e n t . F i g u r e 8 shows a t y p i c a l s c a l e of a female f i s h i n it's  f o u r t h year of l i f e .  F i g u r e 9 shows the s c a l e of a  y e a r l i n g f i s h r i g h t a f t e r the f o r m a t i o n of S C u . men  from which the s c a l e was  week of August.  taken was  The  speci-  captured i n the  I t can be seen t h a t the c i r c u l i  first  i n the area  of the check appear to be q u i t e c l o s e t o g e t h e r and the d i s tance between the l a s t few c i r c u l i shows a s c a l e where S C J J was between the two  checks  i s increasing.  not l a i d down.  Figure 10  The d i s t a n c e  i s very much g r e a t e r than the  d i s t a n c e between A^ and S C J I , but conforms with the d i s t a n c e between A^ and  average average  A . 2  In summary, by o b s e r v i n g the time of f o r m a t i o n of a check, by s t u d y i n g the p h y s i c a l f e a t u r e s of a check, and  by  t a k i n g the d i s t a n c e from the focus of the s c a l e to a check and comparing i t w i t h the average  d i s t a n c e , the nature of a  p a r t i c u l a r check can be determined  with r e l a t i v e  accuracy.  Back-Calculation  A c c o r d i n g to Van Oosten ( 1 9 2 9 ) , "The  soundness of  the s c a l e method of d e t e r m i n i n g the l e n g t h of the f i s h at s u c c e s s i v e years of i t s l i f e  and  i t s annual growth  increments,  depends upon the v a l i d i t y of the f o l l o w i n g p r o p o s i t i o n s : 1.  That and  the s c a l e s remain constant i n t h e i r number ( r e t a i n t h e i r ) identity^ throughout  the  life  16  of 2.  the f i s h  That the annual increment  i n l e n g t h (or some  other dimension which then must be used) of the s c a l e maintains (throughout the l i f e of the f i s h ) a constant r a t i o w i t h the  annual  increment of body l e n g t h . 3.  That the a n n u l i are formed same time each year  y e a r l y and at the  (or some other d i s c o v e r a b l e  r e l a t i o n e x i s t s between t h e i r f o r m a t i o n and increment of t i m e ) . " The s c a l e s of Cymatogaster  are f u l l y formed  before  b i r t h and appear t o remain constant i n both number and i d e n t i t y throughout  life.  The focus of the c e n t r a l part of the  s c a l e s of o l d f i s h of t h i s s p e c i e s i s s t r u c t u r a l l y w i t h the s c a l e s of young f i s h .  identical  The regenerated s c a l e s ,  which r e p l a c e those a c c i d e n t a l l y l o s t , have a c e n t r a l port i o n that  i s quite e a s i l y recognized.  spawning checks are formed  Both the a n n u l i  and  at s p e c i f i c p e r i o d s of the year,  the a n n u l i predominantly i n m i d - A p r i l and the spawning checks predominantly  i n mid-August.  By p l o t t i n g the r e g r e s s i o n l i n e of body l e n g t h on a s c a l e measurement, a r e l a t i v e l y simple method can be d e r i v e d f o r b a c k - c a l c u l a t i n g the body l e n g t h of f i s h at previous periods i n t h e i r The  l i f e history  (Smith,  1955).  average d i s t a n c e from the focus t o the b i r t h  check and t o each spawning check and annulus was  plotted  on  17  F i g u r e 6. Photograph showing concentric rings of c i r c u l i s u r r o u n d i n g t h e f o c u s and continuing out to the leadi n g edge o f t h e s c a l e .  F i g u r e 7. P h o t o g r a p h s h o w i n g large distance between A n n u l u s I and l e a d i n g edge o f s c a l e i n d i c a t i n g Spawni n g Check I I w i l l n o t be l a i d down. (Scale taken from specimen captured i n l a t e September).  F i g u r e 8. T y p i c a l s c a l e o f Cymatogaster i n f o u r t h year of l i f e .  F i g u r e 9. Scale of yearling f i s h just a f t e r formation of S p a w n i n g Check I I .  F i g u r e 10. P h o t o g r a p h s h o w i n g s c a l e where Spawning Check I I was n o t l a i d down.  18 the r e g r e s s i o n l i n e s obtained - body length r e l a t i o n s h i p .  from the a n t e r i o r s c a l e r a d i u s To b a c k - c a l c u l a t e the body  l e n g t h of a f i s h at any previous  stage i n i t s l i f e h i s t o r y ,  the d i s t a n c e from the focus t o the p a r t i c u l a r p o i n t on the s c a l e i s measured. ior it  The measurement i s marked on the anter-  s c a l e r a d i u s a x i s and a p e r p e n d i c u l a r i n t e r c e p t s the r e g r e s s i o n l i n e .  i s extended u n t i l  The b a c k - c a l c u l a t e d  length i s then read o f f the body length a x i s at a point opposite where the r e g r e s s i o n l i n e i s i n t e r c e p t e d . Figure  11 g i v e s the p o i n t s of i n t e r c e p t i o n on the  r e g r e s s i o n l i n e of the b i r t h check, spawning checks and a n n u l i of male Cymatogaster.  Figure  for  I I I g i v e s the average  the female.  body lengths  Table  12 g i v e s the same  at the time of formation  shows, except at the time of formation  information  back-calculated  of each check and of the b i r t h check  and spawning check I, the average s i z e of the females i s l a r g e r than the males throughout t h e i r  l i f e history.  With the r e g r e s s i o n method of b a c k - c a l c u l a t i o n , the v a r i a n c e s  of mean c a l c u l a t e d lengths may be due t o :  1.  D i f f e r e n c e s i n growth of i n d i v i d u a l f i s h .  2.  Deviations  of the i n d i v i d u a l f i s h from the  "normal" body-scale r e g r e s s i o n . 3.  Deviations  of the examined  s c a l e ( s ) from the  average f o r the i n d i v i d u a l f i s h . 4.  E r r o r s i n l o c a t i n g and measuring checks (Whitney and Carlander,  1954).  19  F i g u r e 11.  P o i n t s of i n t e r c e p t i o n on the r e g r e s s i o n l i n e of the B i r t h Check, Spawning Checks, and A n n u l i f o r male Cymatogaster.  F i g u r e 12.  P o i n t s of i n t e r c e p t i o n on the r e g r e s s i o n l i n e of the B i r t h Check, Spawning Checks, and A n n u l i f o r female Cymatogaster.  0  0  1  2  3  4  5  6  1  2  3  4  5  6  ANTERIOR SCALE RADIUS (cm x 22)  ANTERIOR SCALE RADIUS (cm x 22)  20  Figure the end  13 g i v e s the average c a l c u l a t e d length at  of each year of l i f e f o r both male and To check the accuracy  female.  of t h i s method of  back-cal-  c u l a t i o n , a number of f i s h were examined t h a t had j u s t shed forming a spawning check or annulus.  The  fini-  a c t u a l body  l e n g t h measurements were then compared w i t h average backc a l c u l a t e d body lengths  (Table IV).  The  a c t u a l lengths  respond q u i t e c l o s e l y t o the b a c k - c a l c u l a t e d order t o r e c o g n i z e it  lengths.  corIn  t h a t a check has been formed on a s c a l e ,  i s necessary t o wait u n t i l the growth r a t e i n c r e a s e s .  i s probably  due  t o t h i s reason t h a t the a c t u a l measurements  of the f i s h are s l i g h t l y higher, back-calculated  lengths.  on the average, than  At the time of measurement  had been an average growth of 0.15 check t o the  cm.  (X 22)  groups i s given i n Table V.  group, the females tend t o be observation  the there  from the  last  l e a d i n g edge of the s c a l e .  A r e p r e s e n t a t i v e sample of l e n g t h w i t h i n age  It  distribution  Within  any  one  l a r g e r than the males.  age This  corresponds with the b a c k - c a l c u l a t i o n work that  showed females, on the average, ar,e l a r g e r than the males at the times of check  formation.  Lee's Phenomenon  For v i r t u a l l y every s p e c i e s of f i s h whose s c a l e s have been used f o r b a c k - c a l c u l a t i o n s , i t has  been demon-  21  Figure  13.  Calculated  l e n g t h at the  end  of each year of  life.  T a b l e IV.  Comparison of Average B a c k - C a l c u l a t e d Body Length at time of Formation of each check w i t h A c t u a l Body Lengths  Sex  Length  d  BackCalculated  7.3  Actual  ?  A  l  S C  II  2  III  A  3  s c  4  SC  y  A  S C  8.8  9.6  10.3  10 .8  11.1  11.5  12.0  7.6  8.9  10.1  10 .5  10 .8  11.2  11.6  12.0  BackCalculated  7.4  9.0  9.9  10.5  11.0  11.4  11.8  12.4  Actual  7.6  8.8  10 .2  10.8  11.2  11.6  11.9  12.2  I  V  A  to to  T a b l e V.  Length D i s t r i b u t i o n  Length Interval  BC  a* 4.1 4.6 5.1 5.6 6.1 6.6 7 .1 7.6 8.1 8.6 9.1 9.6 10.1 10 .6 11.1 11.6 12.1 12.6 Total  -  4.5 5.0 5.5 6.0 6.5 7.0 - 7 .5 _ 8 .0 _ 8 .5 — 9 .0 — 9 .5 — 10 .0 — 10 .5 — 11 .0 _ 11 .5 — 12 .0 — 12 .5 13 .0 #  o f Age  SCj  $  d"  ?_  Ai  d*  1 ,11 7 4  23  Groups.  SC  ?  1 8 10 2  21  d*  1 2 3 2  8  A  T I  .?  2 7 8 2 1  20  S C 2  III  d"  ?  d*  1 6 20 11 2 1  3 20 14 8 1  2 2 4 2  41  46  10  A  ?  2 3 1 4 1  11  3  o*  2 6 3  11  s  o.  1 6 4 1  12  c  iv  &  1 4 7 3  15  A  $  2 2 2 1 7  4  S C  d" ?  1 1  V  d*  ?  1  3  2 2 1  2  5  24  s t r a t e d t h a t the computed lengths at the end of the f i r s t year of l i f e decrease as the f i s h i n c r e a s e s w i t h age. another way,  Stated  the o l d e r the f i s h whose s c a l e i s used f o r the  c a l c u l a t i o n , the lower the value o b t a i n e d .  This character-  i s t i c of l e n g t h computations based on s c a l e s i s u s u a l l y r e f e r r e d t o as "Lee's phenomenon of apparent changes i n growth r a t e . "  (Van Oosten,  1929).  In the sample of Cymatogaster s t u d i e d , Lee's phenomenon i s not apparent. two main f a c t o r s .  T h i s , however, may  F i r s t , Cymatogaster has a r e l a t i v e l y  l i f e span and t h i s phenomenon of change not  be due t o  i n growth r a t e  short may  become r e a d i l y apparent over such a b r i e f p e r i o d of time.  Second, very few f i s h were o b t a i n e d that were i n the 4 years p l u s age group.  I t i s e n t i r e l y p o s s i b l e t h a t i f a much  l a r g e r number of f i s h i n t h i s age group had been o b t a i n e d and b a c k - c a l c u l a t i o n s c a r r i e d out w i t h t h e i r s c a l e s , Lee's phenomenon might show up.  Age at M a t u r i t y  Hubbs (1921) determined that the t e s t e s of male Cymatogaster were s e x u a l l y mature  at the time of b i r t h .  He  a l s o demonstrated that s e x u a l m a t u r i t y at b i r t h o c c u r r e d i n the  males of another v i v i p a r o u s perch,  aurora.  Amphigonopterus  The great m a j o r i t y of y e a r l i n g Cymatogaster  had formed a spawning check.  males  'Except i n a very few cases, the  25  male gonads mature each s p r i n g from the f i r s t on, and a spawning check i s formed by In  year of  life  mid-August.  the s p r i n g no y e a r l i n g female was found t o con-  t a i n embryos, but over 99% of the f i s h two or more years of age d i d .  T h i s f i g u r e c o r r e l a t e s w i t h the age and  growth  a n a l y s i s which showed t h a t l e s s than 1% of the females f a i l e d t o form a spawning  T a b l e VI.  check.  Average number of embryos c a r r i e d by adult Cymatogaster.  Length (cm)  Number of A d u l t s  Average Number of Embryos  12  7  - 10 .4  21  9  10.5 - 10 .9  56  9  11.0  - 11.4  19  10  11.5 - 11.9  23  10  - 12.4  11  13  12.5 - 12.9  8  12  9.5 10.0  12.0  -  9.9  female  Fecundity  T a b l e VI g i v e s the average number of c a r r i e d by mature Cymatogaster 5 t o 17 w i t h a mean of 10.  females.  embryos  The range was  T a b l e VI i l l u s t r a t e s that  from there  26  i s a tendency f o r the average number of embryos c a r r i e d by the female t o i n c r e a s e as the body l e n g t h  increases.  Instantaneous Growth Rates  A p r e l i m i n a r y study was monthly and  d a i l y b a s i s , on the  e x h i b i t e d by Cymatogaster.  The  c a r r i e d out,  instantaneous  (1957) and w i l l not be d i s c u s s e d  by the  instantaneous  annual,  growth r a t e s  d e f i n i t i o n of  r a t e s of growth has been given by R i c k e r  The  on an  instantaneous  (1958) and Brown  here.  growth r a t e ( i ) was  calculated  formula log  1 0  where L^- and  L  t  +  1 (cms)  -  l o  Sio  + I are, r e s p e c t i v e l y , the  the f i s h at the beginning  and  The  growth increment i s the  any  one  end  t  instantaneous  )  average i n c r e a s e i n l e n g t h  + 1 "  obtained  during  as  L  t  growth r a t e  by d i v i d i n g the c a l c u l a t e d '  growth r a t e by the number of days of growth  between the two The  c m s  average l e n g t h of  In cases where the average d a i l y instantaneous i s given, the value was  (  of each p e r i o d of growth.  p e r i o d and can be d e f i n e d Lt  L  r e l e v a n t checks.  mean s i z e of a sample i s d e f i n e d as the  average  s i z e of the f i s h w i t h i n a sample at the mid-point of a s p e c i f i c p e r i o d of growth.  Cymatogaster grows l o g a r i t h m i c a l l y ,  27  t h u s t h e term, mean s i z e , s h o u l d be s t a t i s t i c a l l y v a l i d  and  may be c a l c u l a t e d by t h e f o r m u l a  antilog  L a r k i n (1957), i n a paper d i s c u s s i n g t h e growth of  d i f f e r e n t p o p u l a t i o n s of rainbow t r o u t , s t a t e s t h a t  " . . . i t i s d e s i r a b l e t o d i s p e n s e w i t h age as a c r i t e r i o n of  growth r a t e and r e s t r i c t comparisons t o growth r a t e s of  f i s h of t h e same s i z e , i e . p l o t i n s t a n t a n e o u s growth r a t e against s p e c i f i e d s i z e . "  F i g u r e 14 g i v e s such a p l o t f o r  Cymatogaster and was o b t a i n e d by u s i n g t h e average d i s t a n c e s between b i r t h checks and a n n u l i ( T a b l e I I ) .  There i s a  g e n e r a l d e c l i n e i n t h e i n s t a n t a n e o u s growth r a t e from time of  b i r t h t h r o u g h t o t h e o l d e s t f i s h i n t h e sample  19).  (Figure  T h i s c o r r e s p o n d s t o t h e g e n e r a l p a t t e r n as most f i s h  a t t a i n t h e i r h i g h e s t r a t e of growth d u r i n g t h e i r f i r s t of  year  l i f e and t h e r e a f t e r t h e annual growth r a t e r a p i d l y dec-  lines . F i g u r e 15 g i v e s t h e average i n s t a n t a n e o u s d a i l y growth r a t e between t i m e s of b i r t h check, spawning check and annulus f o r m a t i o n .  These d a t a seem t o i n d i c a t e t h a t  t h e r e i s a v e r y h i g h growth r a t e between t h e t i m e of b i r t h check f o r m a t i o n and t h e f i r s t spawning check.  There  fol-  lows a r a p i d d e c r e a s e i n growth r a t e between t h e t i m e of f o r m a t i o n of t h e f i r s t spawning check and t h e f i r s t a n n u l u s .  AVERAGE INSTANTANEOUS DAILY GROWTH RATE  AVERAGE INSTANTANEOUS DAILY GROWTH RATE CO  CuOP  c  SB  Ss 0  r-  CD  H-  3 OQ  ere O  o ct  CD 3 ro1  o  P ct CD  ft  o  cn Hs o* SO  CD rt < CD CD CD  ere > CD 3 HC  a  cn  rt 3 f» a 3 rt f»  a  CD  c c  cn  29  There i s again an i n c r e a s e i n the instantaneous growth r a t e between t h e time of f o r m a t i o n of the f i r s t second spawning check.  annulus  and the  I t i s evident t h a t t h e r e i s a p a t -  t e r n which i s repeated throughout  the l i f e  h i s t o r y of Cymato-  gaster , ( F i g u r e 20). The highest l e v e l s of instantaneous growth r a t e s occur i n the p e r i o d s between the f o r m a t i o n of an annulus  (or b i r t h  check) and the f o l l o w i n g spawning check.  T h i s time p e r i o d corresponds from m i d - A p r i l t o mid-August.  t o the s p r i n g and summer months The lowest  l e v e l s of i n s t a n -  taneous growth r a t e occur i n the p e r i o d between the formation  of a spawning check and an annulus.  corresponds  T h i s time p e r i o d  t o the winter months from mid-August t o mid-  April. The  f l u c t u a t i o n s of instantaneous growth r a t e e x h i -  b i t e d by Cymatogaster f o l l o w a p a t t e r n t h a t would seem r e a s onable t o expect.  The lowest  l e v e l of growth r a t e occurs  over approximately  an e i g h t month p e r i o d d u r i n g the f a l l and  winter when the water temperatures  are low and presumably the  metabolic r a t e s are at a low l e v e l .  Also, there i s a ten-  dency f o r Cymatogaster t o move i n t o deeper water i n t h e f a l l as the water temperatures  begin t o drop,  the a v a i l a b i l i t y of food organisms,  and  both i n q u a n t i t y and  number of s p e c i e s may be g r e a t l y reduced h a b i t a t areas.  ( F i g u r e 21),  i n these deeper  T h i s r e d u c t i o n i n the a v a i l a b i l i t y  of food  coupled w i t h a s l o w i n g down of metabolic r a t e s may be an important  f a c t o r i n v o l v e d i n annulus  formation.  30  A f t e r t h e annulus i s formed sometime around April,  t h e r e i s a t e n d e n c y shown b y C y m a t o g a s t e r  t o move i n t o s h a l l o w e r h a b i t a t starts to rise fish  (Figure 21).  to start  a r e a s as t h e w a t e r  temperature  T h i s movement w i l l b r i n g  i n t o c o n t a c t w i t h an i n c r e a s e d number o f f o o d  which are a s s o c i a t e d w i t h the s h a l l o w e r waters. water temperatures s t a r t t o r i s e it  mid-  the  organisms  As t h e  i n the s p r i n g of the year,  i s assumed t h a t m e t a b o l i c r a t e s a l s o i n c r e a s e .  The  rise  i n water temperature i s a l s o a s s o c i a t e d w i t h the i n c r e a s e i n numbers o f p l a n k t o n i c o r g a n i s m s , f o r when o p t i m u m  spring  t e m p e r a t u r e l e v e l s are r e a c h e d , p l a n k t o n blooms s t a r t  occur-  r i n g with increasing frequency. W i t h an i n c r e a s e i n m e t a b o l i c r a t e s and w i t h i n c r e a s e i n t h e number o f f o o d o r g a n i s m s q u a n t i t y and i n number o f s p e c i e s , t o e x p e c t t h a t t h e r e w o u l d be  an  a v a i l a b l e , both i n  i t w o u l d seem r e a s o n a b l e  an i n c r e a s e i n g r o w t h  rate.  T h i s expected i n c r e a s e i n i n s t a n t a n e o u s d a i l y growth r a t e i n t h e s p r i n g and summer months ( i e . - b e t w e e n t h e f o r m a t i o n o f an a n n u l u s and t h e s u c c e e d i n g s p a w n i n g Figure  check)  i s shown i n  15. The  g e n e r a l tendency f o r the growth r a t e of  an  a n i m a l t o d e c l i n e as i t i n c r e a s e s i n s i z e i s a l s o  demonstra-  t e d b y F i g u r e 20.  increase  There  is,  h o w e v e r , an a p p a r e n t  i n i n s t a n t a n e o u s g r o w t h r a t e b e t w e e n a n n u l u s 4 and  spawning  c h e c k V o v e r t h e p e r i o d b e t w e e n a n n u l u s 3 and s p a w n i n g IV.  T h i s may  be due e i t h e r t o an a c t u a l i n c r e a s e o f  check  growth  31  r a t e i n the f o u r t h year, which i s c o n t r a r y t o the p a t t e r n , or, t h i s i n c r e a s e may The  be due  general  t o sampling e r r o r .  sample s i z e of the four year o l d f i s h i s q u i t e  hence i f f i s h i n t h i s sample happened t o be  small,  l a r g e r than  average, i t would cause a l a r g e c o r r e s p o n d i n g i n c r e a s e i n the  average instantaneous d a i l y growth r a t e . Figures  16 and  17 give the  average monthly i n s t a n -  taneous growth r a t e of Cymatogaster f o r the months of June, J u l y , August and  September, which, due  t o the migratory  na-  t u r e of the f i s h i n the study area, were the only months f o r which a s u f f i c i e n t duct such a study.  The  number of f i s h were a v a i l a b l e t o conmales, except f o r the y e a r l i n g f i s h ,  m a i n t a i n a r e l a t i v e l y constant  growth r a t e through June  J u l y , then the growth r a t e i n c r e a s e s by mid-August 21) .  and  (Figure  During June and J u l y the males, are s t i l l showing d i s -  t i n c t spawning c o l o u r a t i o n and t h e r e  appears t o be  lower r a t e of f e e d i n g than i n e a r l y s p r i n g .  By  a much  mid-August,  however, most s i g n s of spawning c o l o u r a t i o n are gone and r a t e of f e e d i n g increase  increases.  T h i s apparently  the  accounts f o r the  i n the average instantaneous growth r a t e at t h i s  t irae. Cymatogaster females a l l show a d e c l i n e i n growth r a t e i n mid-July, i n some cases to a very 17).  low  level  (Figure  T h i s p e r i o d of decrease of growth r a t e corresponds  c l o s e l y w i t h the time that the females are g i v i n g b i r t h t o t h e i r young.  By the  l a s t week i n June, and u n t i l the  birth-  0Q  OP  3  O  4  CD  05 4 • P  Q  O  s  prtO  c+ CD  MONTHLY  AVERAGE  INSTANTANEOUS  MONTHLY  GROWTH  RATE  >  10  <  CD  i-S  CD  P  X P croc,  CD  H-  <rc  INSTANTANEOUS  CD  P  <<  AVERAGE  to H - CD  •  H-  3  rt-  CD &  CO r+  P  o p E3  cr "< rtCD  P  CD  0  O  c  t r CO  p  30  OP CD  O  rt-  i— c r 1  PCO  h-' <<  CO  GROWTH  RATE  33  i n g p e r i o d i s over,  the f e e d i n g of the Cymatogaster females  ceases almost e n t i r e l y .  T h i s c e s s a t i o n of food intake  pre-  sumably accounts f o r the decrease i n growth r a t e d u r i n g J u l y . A f t e r g i v i n g b i r t h , the females begin t o a c t i v e l y feed which probably  again  accounts f o r the i n c r e a s e i n growth r a t e a t -  t a i n e d by mid-August. The  probable  reason  f o r "the much g r e a t e r s i z e i n c r e -  ases e x h i b i t e d by y e a r l i n g f i s h , both male and female, over the o l d e r year c l a s s e s can be seen i n F i g u r e that y e a r l i n g f i s h s t i l l  15 which shows  have a growth r a t e t h a t i s propor-  t i o n a l l y much g r e a t e r than the o l d e r age groups.  Length-Weight R e l a t i o n s h i p s  F i g u r e s 18 and 19 represent  the length-weight  rela-  t i o n s h i p of male and female Cymatogaster which have been preserved i n 10% f o r m a l i n .  F i g u r e 18 g i v e s a comparison between  pregnant and non-pregnant females and shows t h a t pregnancy causes a g r e a t e r weight f o r any given l e n g t h .  As the t o t a l  embryo weight i n c r e a s e s , t h e r e i s a p r o p o r t i o n a t e l y g r e a t e r i n c r e a s e i n the r a t i o of weight t o l e n g t h . F i g u r e 19 g i v e s a comparison between males before and  a f t e r the spawning check i s formed and shows t h a t  is,  on the average, l e s s weight f o r a given l e n g t h a f t e r the  spawning check i s formed.  there  T h i s i n d i c a t e s t h a t t h e r e i s an  i n c r e a s e i n weight f o r a given body l e n g t h as the male becomes  30  • •• • • •  25  ~  2 0  • •  in  • • •* • •  >Q O  <n 10  .a .**.•  5  0  5  10  15  BODY LENGTH (cm) • IMMATURE a n d PREGNANT FISH • M A T U R E FISH A F T E R GIVING BIRTH  F i g u r e 18. Comparison of the body length body weight r e l a t i o n s h i p of immature and pregnant f i s h with mature f i s h a f t e r g i v ing b i r t h .  5  10  15  BODY LENGTH (cm) • B E F O R E SPAWNING C H E C K • A F T E R SPAWNING C H E C K  FORMATION FORMATION  F i g u r e 19. Comparison of the body l e n g t h body weight r e l a t i o n s h i p b e f o r e and a f t e r Spawning Check f o r m a t i o n i n male Cymatogaster. 03  s e x u a l l y m a t u r e and t h e gon a d s i n c r e a s e i n s i z e  36  SEASONAL AND  Nylon used  gill  nets  and  Estimates  distributions, behavior  and  positions  20  corner  shows t h e K e a t e s gill  and  net  one  of O c t o b e r .  independently  daylight  While  the  recorded  abundance o f  net,  The and,  15" f e e t thest  gill  net  depth  the  The  of  one  the  at  of  the  average  of  once  the  end  o f May  diving  to  area.  i n f o r m a t i o n on  depth  distributions  and  and  their  t o s h o r e was  the  diver and  young o f t h e  year  schooling behavior. out  c o n d i t i o n s , was  designated the  Each  from  designated the  study  the  observa-  study  adults, yearlings,  closest  The  corner  n e t s were s e t i n s t r i n g s  s h o r e was  feet  from  area.  entire  of water throughout  period.  deep n e t  the  shore  shallow  set i n 8 to The  and  net  was  far-  set i n  water.  nylon g i l l  n e t s were f o u n d  with regards  t o mesh s i z e ,  of  the  the year,  indicated,  n e t s were f i s h i n g ,  d e p e n d i n g upon t i d a l  from  t o 40  hours,  habitat preferences  The line.  s e t s are  at t h e N o r t h - E a s t  t i o n s were made t h r o u g h o u t  their  I s l a n d study  C o l l e c t i o n s were made on t h e  a week, d u r i n g t h e  fish,  abundance,  habitat preferences.  study beach.  relative  d i u r n a l movements o f Cyma-  were made o f r e l a t i v e  o f t h e two  South-West  and  o b s e r v a t i o n s were  d i r e c t i o n a l movement t e n d e n c i e s , s c h o o l i n g  Figure  20  Scuba d i v i n g  t o a s c e r t a i n the seasonal  togaster .  end  DIURNAL MOVEMENT PATTERNS  the  t o be  very  \ i n c h mesh c a u g h t  1 i n c h mesh c a u g h t  mainly  selective  only  yearlings,  young and  the  FIGURE 20.  SHOWING THE KEATES ISLAND STUDY AREA INCLUDING HABITAT AREAS AND POSITION OF GILL NET STRINGS. F ~  APPROXIMATE  HIGH  TIDE  LEVEL  |7~  APPROXIMATE  L O W TIDE  LEVEL  38  \\ i n c h mesh caught  mainly a d u l t f i s h .  Because of the s e l e c -  t i v i t y of the nets, the mesh s i z e s were a l t e r n a t e d i n the s t r i n g s at o p p o s i t e ends of the beach. was  I f the \\ i n c h mesh  set at the shallow end at the South-West corner of the  beach, the \\ i n c h mesh was  set at the deep end of the other  string. The Keates relatively  distinct  I s l a n d study area had w i t h i n i t t h r e e h a b i t a t areas  ( F i g u r e 20).  s t r i n g s of nets were set i n such a way t h r e e areas at a l l times. " r e e f - f a c e " h a b i t a t and was i e n t s found beach.  first  two  t h a t they sampled the  area was  designated a  c h a r a c t e r i z e d by the steep  grad-  around the r e e f s at the South-West corner of the  In p l a c e s these rock w a l l s f a l l o f f almost  t o depths of over a "kelp-bed" tration  The  The  150  feet.  The second  h a b i t a t area and was  area was  vertically  designated  c h a r a c t e r i z e d by a concen-  of s e v e r a l s p e c i e s of sea-weeds, the dominant  being Sargassum muticium.  one  The k e l p beds were found t o ex-  tend along the e n t i r e beach approximately and t e n f e e t below the zero t i d e l e v e l .  f i v e feet  above  The t h i r d area  was  designated an "open-water" h a b i t a t and r e f e r r e d t o the r e g ions over the pebble beach and over the mud  and sand  flats  o u t s i d e the k e l p beds.  Seasonal Movements  The  data o b t a i n e d i n d i c a t e that Cymatogaster  39  e x h i b i t s a complex p a t t e r n of s e a s o n a l movements t h a t v a r i e d w i t h t h e age and sex of t h e f i s h , and t h e t i m e of  t h e i r s t a t e of m a t u r i t y ,  year.  There are a number of complex, i n t e r a c t i n g f a c t o r s which make i t v e r y d i f f i c u l t t o show q u a n t i t a t i v e l y any d i s t i n c t h a b i t a t or a r e a p r e f e r e n c e .  These f a c t o r s  include  changes i n d i u r n a l movement p a t t e r n s , s e a s o n a l changes i n depth p r e f e r e n c e s  and d i r e c t i o n a l movement t e n d e n c i e s ,  and  t h e r i s e and f a l l of t h e t i d e s w h i c h can l e a v e a major p o r t i o n of t h e s t u d y a r e a h i g h and d r y f o r l o n g p e r i o d s of t h e day.  With the data a v a i l a b l e , i t i s a l s o extremely  c u l t t o d i s t i n g u i s h between depth p r e f e r e n c e s preferences.  diffi-  and h a b i t a t  I t i s f o r t h e s e reasons t h a t h a b i t a t  prefer-  ence has been a n a l y s e d o n l y t o t h e e x t e n t of o b t a i n i n g e s t i mates of r e l a t i v e abundance i n each h a b i t a t a r e a f o r ent p e r i o d s d u r i n g t h e t i m e Cymatogaster area.  differ-  i s i n the study  I t i s a l s o f o r t h e p r e c e e d i n g reasons t h a t  habitat  p r e f e r e n c e has been i n c l u d e d under t h e s e c t i o n on s e a s o n a l movements. The r e s u l t s o b t a i n e d from t h e s t u d y of movements are g i v e n under two s e p a r a t e h e a d i n g s ; d i v i n g o b s e r v a t i o n s and g i l l net d a t a . p e r t a i n i n g t o Scuba d i v i n g o b s e r v a t i o n s ,  seasonal Scuba  The f i r s t  section,  describe  seasonal  changes of depth d i s t r i b u t i o n s , s c h o o l i n g b e h a v i o r ,  and r e -  l a t i v e abundance of Cymatogaster b o t h over t h e s t u d y beach a r e a and i n r e g i o n s t h a t c o u l d not be sampled by g i l l  nets.  40 The  second s e c t i o n , p e r t a i n i n g t o g i l l  the s e q u e n t i a l changes, from May  net  data,  describes  through t o October, of  r e l a t i v e abundance of a d u l t , y e a r l i n g , and  young of  year Cymatogaster i n the three r e l a t i v e l y d i s t i n c t areas.  This s e c t i o n also contains  a tagging  program t h a t was  the  the habitat  the r e s u l t s o b t a i n e d from  conducted t o a s c e r t a i n whether or  not Cymatogaster e x h i b i t e d a d i s t i n c t p a t t e r n of  seasonal  d i r e c t i o n a l t e n d e n c i e s of movement. If the two that t h e r e ined by use  sections  are compared, i t can be  i s a c l o s e c o r r e l a t i o n between the r e s u l t s obta-  Scuba d i v i n g o b s e r v a t i o n s  of g i l l  Scuba D i v i n g  and those o b t a i n e d by  Observations  c i e s t o be observed i n the study area.  of the  the r e e f f a c e s majority  s e v e r a l schools  i n depths below 50 f e e t .  and  first  schools  Though the  of i n d i v i d u a l s were observed o f f the were seen over the mud  spe-  Throughout the  week i n June they congregated i n i n c r e a s i n g l y l a r g e  great  the  nets.  Y e a r l i n g Cymatogaster were the f i r s t  off  seen  reefs,  sand f l a t s i n  open water. Several  days a f t e r t h e i r f i r s t  appearance,  schools  of y e a r l i n g s were observed over the study beach i n depths as shallow as 20 f e e t .  S h o r t l y t h e r e a f t e r , by the  week i n June, the m a j o r i t y  of the y e a r l i n g s had  second  moved back  41 i n t o deeper water where they remained u n t i l the l a s t week of June.  At t h i s time, which i s immediately p r i o r t o the spawn-  i n g p e r i o d , t h e r e was  a sudden i n c r e a s e i n the numbers of  y e a r l i n g s i n the shallow waters over the beach.  A week l a t e r ,  however, the great m a j o r i t y had again r e t u r n e d t o deeper waters (from 50 t o 90 f e e t ) o f f the r e e f During the month of June i t was  faces. observed that the  y e a r l i n g Cymatogaster e x h i b i t e d a g e n e r a l d i r e c t i o n a l t e n dency of movement from the South-West t o the North-East. T h i s movement was of the t i d a l  evident r e g a r d l e s s of the d i r e c t i o n of flow  currents.  Through most of J u l y , August, and September,  the  m a j o r i t y of y e a r l i n g f i s h were found i n depths from 35 t o 90 f e e t o f f the r e e f f a c e s .  During t h i s p e r i o d t h e r e were a l -  ways a s c a t t e r e d few i n d i v i d u a l s i n and around the k e l p beds. These i n d i v i d u a l s showed no tendency t o s c h o o l . Tn the l a s t week of September t h e r e was  another  sudden i n c r e a s e i n the numbers of y e a r l i n g s observed i n the shalTow water over the beach.  They remained t h e r e f o r a  r e l a t i v e l y short time and then r e t u r n e d t o deeper waters.  By  mid-October almost a l l the y e a r l i n g s had moved o f f the beach and were s c h o o l e d along the r e e f f a c e s i n depths ranging from 60 t o 110 f e e t .  By the end of October t h e r e were no y e a r l i n g s  observed i n the study area. The f i r s t  adult Cymatogaster were observed moving  i n t o the study area i n e a r l y June, s h o r t l y a f t e r the a r r i v a l  42  of  the y e a r l i n g s .  These f i s h were mature males and they were  c o n c e n t r a t e d o f f the r e e f f a c e s at depths of 60 t o 100  feet.  W i t h i n a r e l a t i v e l y short p e r i o d of time, t h r e e days, the m a j o r i t y o f these f i s h had moved i n t o s h a l l o w water over the beach where they remained f o r about a week. Approximately a week a f t e r the f i r s t the  appearance of  adult males, l a r g e s c h o o l s of adult female Cymatogaster  began t o move i n t o the study area o f f the r e e f  faces.  By the t h i r d week i n June, the males began t o move i n t o deeper water and the females became i n c r e a s i n g l y abundant i n the s h a l l o w water over the beach.  In the l a s t week  of  a great  June, j u s t p r i o r t o spawning, t h e r e was  increase  i n the numbers of adult Cymatogaster, both male and female, found i n the r e g i o n of the k e l p beds. By the f i r s t  week i n J u l y , c o r r e s p o n d i n g t o the  peak of the spawning p e r i o d , l a r g e s c h o o l s of a d u l t s were observed i n the very s h a l l o w areas over the beach, o f t e n i n as l i t t l e as f i v e f e e t of water. By the second week i n J u l y , the m a j o r i t y of a d u l t s had moved o f f the shallow beach i n t o deeper water o u t s i d e the k e l p beds.  From mid-July t o e a r l y October t h e r e were r e l a -  t i v e l y few adult Cymatogaster observed i n the v i c i n i t y of the beach and k e l p beds d u r i n g the d a y l i g h t hours.  The great  m a j o r i t y remained congregated i n l a r g e s c h o o l s o f f the r e e f faces i n depths r a n g i n g from 35 t o 110 f e e t . no adult f i s h were observed i n the study area.  By mid-October  43  The young of the year, from the time of b i r t h , i n e a r l y J u l y , t o mid-August,  remain i n r e l a t i v e l y compact  s c h o o l s i n and around the k e l p beds.  In mid-August the  young of the year begin t o move i n t o deeper water o f f the r e e f f a c e s and over the mud and sand f l a t s . ber  By mid-Septem-  the great m a j o r i t y of f i s h of t h i s age group are t o be  found i n depths below 50 f e e t . By mid-October only s m a l l s c h o o l s of young of the year were observed o f f the r e e f f a c e s i n depths below 80 feet.  There were a s c a t t e r e d few i n d i v i d u a l s i n t h e v i c i -  n i t y of the k e l p beds. the  By the end of October no young of  year were observed i n the study area.  G i l l Net Data  The r e s u l t s o b t a i n e d by the use of g i l l  nets i n d i -  cate t h a t each age group, and both sexes, of Cymatogaster exhibit  a r e l a t i v e l y complex p a t t e r n of onshore and o f f -  shore movements that can vary s e a s o n a l l y . No Cymatogaster were caught by g i l l month of May, the f i r s t June.  nets i n the  being taken i n the f i r s t  week of  At t h i s time t h e great m a j o r i t y of f i s h w i t h i n the  areas sampled by the g i l l  nets were y e a r l i n g s  (Figure 21).  By t h e second week i n June, the numbers of y e a r l i n g s capt u r e d had decreased and adult Cymatogaster began t o be taken in  i n c r e a s i n g numbers ( F i g u r e 21).  The m a j o r i t y of the f i r s t  44  adult a r r i v a l s were s e x u a l l y mature males ( F i g u r e 22), which were found i n much shallower water than were most females (Figures 24 and 25).  By the t h i r d week i n June the numbers  o f . a d u l t males and females taken by the g i l l  nets were  roughly equal over the e n t i r e study area. In ing  the l a s t week of June, j u s t p r i o r t o the spawn-  p e r i o d , t h e r e was  a great i n c r e a s e i n the number of both  adult and y e a r l i n g Cymatogaster  caught by the g i l l  nets.  The  m a j o r i t y of these f i s h were taken i n the deep nets over the mud  and sand f l a t s o u t s i d e the k e l p beds ( F i g u r e s 21 - 25). In  the f i r s t week of J u l y , at the peak of the  spawning season, the great m a j o r i t y of f i s h were taken i n very s h a l l o w water over the beach  (Figures 23 - 25).  At t h i s  time the y e a r l i n g s had again moved o f f the area sampled the  by  nets (Figure 21) . By the second week i n J u l y a great d e a l of spawn-  ing  had taken p l a c e and most of the adult f i s h were concen-  t r a t e d i n the v i c i n i t y of the k e l p beds.  The new  born young  of  the year were a l s o found almost e x c l u s i v e l y i n the r e g i o n  of  the k e l p beds i n compact s c h o o l s .  From mid-July u n t i l  they moved from the study area i n e a r l y October, the numbers of  adult Cymatogaster  remained  taken by g i l l  at a r e l a t i v e l y  low l e v e l  nets i n d a y l i g h t  hours  ( F i g u r e 22).  The number of y e a r l i n g s taken over the study beach a l s o remained  at a low l e v e l from e a r l y J u l y t o the t h i r d  week i n September.  In the l a s t week of that month t h e r e was  45  F i g u r e 21.  Seasonal r e l a t i v e Cymatogaster.  abundance of a d u l t and y e a r l i n g  F i g u r e 22.  Seasonal r e l a t i v e abundance of mature male and female Cymatogaster.  MAY  JUNE  9 23 29  8 16 23 30  5 20 29 12 SEPT. OCT. YEARLING ADULT  I -  100  u.  o CC LU CO  2  50  29 MAY  I  6 9 12 16 24 28 JUNE  3 9 23 29 JULY DATE  •ranniHirl  8 16 23 AUG  30  5 20 29 12 SEPT. OCT. MALE FEMALE  46  F i g u r e 23.  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of y e a r l i n g Cymatogaster.  F i g u r e 24.  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of mature male Cymatogaster.  F i g u r e 25.  Seasonal depth d i s t r i b u t i o n s and r e l a t i v e abundance of mature female Cymatogaster.  100 80  I li-  60  ll.  o _ u ca _ _ z  40 20  29 MAY  6 9 JJJNE  12 16 24 2 8 3 9 23 29 JULY  DATE  29 MAY  8 1 6 23 3 0 5 2 0 29 12 AUG SEPT. OCT. DEEP NETS SHALLOW NETS  6 9 12 16 24 2 8 3 9 23 2 9 8 1 6 2 3 30 5 2 0 29 12 JUNE JULY AUG. SEPT. OCT.  DATE  r_ mm  DEEP NETS SHALLOW NETS  47 i  a great i n c r e a s e i n the number of y e a r l i n g s taken over beach ( F i g u r e 23).  The  the  l a r g e s c h o o l s of y e a r l i n g s remained i n  shallow water only a short time before they again moved o f f the beach i n t o deeper water.  Tagging R e s u l t s  D i v i n g o b s e r v a t i o n s , coupled w i t h the f a c t t h a t at c e r t a i n times  of the year the great m a j o r i t y of f i s h were  taken on one p a r t i c u l a r s i d e of the g i l l  nets, i n d i c a t e d  t h a t Cymatogaster e x h i b i t e d g e n e r a l t e n d e n c i e s movement t h a t v a r i e d s e a s o n a l l y . was  of  directional  A l i m i t e d t a g g i n g program  conducted t o see i f these o b s e r v a t i o n s were c o r r e c t (Table  VII) . A t o t a l of 983 inserted just  f i s h were tagged, by a nylon  a n t e r i o r t o the d o r s a l f i n , and then r e l e a s e d  over the study beach between the two  s e t s of g i l l  t o t a l of 84 tagged f i s h were recovered Table  A  (Table V I I I ) .  a r r i v i n g i n the study  tagged f i s h were r e c a p t u r e d i n the g i l l corner of the beach.  flow of the t i d a l c u r r e n t s was North-East.  nets.  IX shows t h a t d u r i n g the month of June, when  the f i s h are f i r s t  North-East  thread  area, 25 of  net s e t s at the  On June 12 the d i r e c t i o n of from the South-West t o the  On June 25 the d i r e c t i o n of flow was  o p p o s i t e , from the North-East  29  t o the South-West.  exactly The  g i n g data i n d i c a t e s t h a t i n the s p r i n g of the year,  tag-  regard-  l e s s of the d i r e c t i o n of flow of the t i d a l c u r r e n t s , Cyma-  Table V I I .  Date  Tag Recovery R e s u l t s .  Age Group  Number Released  Number Recovered  N  P o s i t i o n Recovered _ _ E  g  e  t  w  g  t  June 12  Adult Yearling Young of Year  59 62 0  7 4 0  6 4 0  1 0 0  June 25  Adult Yearling Young of Year  103 109 0  8 10 0  6 9 0  2 1 0  August 30  Adult Yearling Young of Year  28 32 40  3 8 2  0 2 1  3 6 1  September 5  Adult Yearling Young of Year  61 95 144  7 9 3  2 0 1  5 9 2  September 20  Adult Yearling Young of Year  20 50 30  0 2 1  0 0 0  0 2 1  September 29  Adult Yearling Young of Year  29 41 80  2 6 12  0 2 5  2 4 7  00  49 togaster  e x h i b i t s a general  from the South-West t o the  d i r e c t i o n a l tendency of movement North-East.  T a b l e IX shows that i n the f a l l  ( l a t e August  September), 42 of 52 tagged f i s h were r e c a p t u r e d net s e t s at the South-West corner ing  d i r e c t i o n s of t i d a l c u r r e n t  and  i n the  gill  of the beach, d e s p i t e  flow.  The  vary-  data i n d i c a t e s  that i n the f a l l Cymatogaster e x h i b i t s a d i r e c t i o n a l tendency of movement, from the North-East t o the South-West, that i s d i r e c t l y opposite  t o that found i n the  spring.  In summary, based on i n f o r m a t i o n nets and  Scuba d i v i n g o b s e r v a t i o n s ,  i t may  obtained  by  gill  be s t a t e d that  Cymatogaster e x h i b i t s a r e l a t i v e l y complex p a t t e r n of seas o n a l movements that may t h e i r age  and sex.  are y e a r l i n g s .  The  The  vary with the time of year and first  f i s h t o appear i n the study  y e a r l i n g s are c l o s e l y f o l l o w e d by  adult males and then by the  with  adult females.  area  the  Over the beach  area the numbers of both sexes of adult and y e a r l i n g Cymatogaster til  remain at a f a i r l y constant  l e v e l from mid-June  j u s t p r i o r t o the spawning p e r i o d .  is  a great  increase  in  the v i c i n i t y of the k e l p beds.  At t h i s time  there  i n the number of f i s h over the beach During the  un-  and  actual period  of spawning the adult f i s h move i n t o very shallow water over the beach w h i l e the y e a r l i n g s move out the r e e f f a c e s .  i n t o deeper water o f f  A f t e r spawning the a d u l t s a l s o move out  into  deeper water o f f the r e e f faces and remain t h e r e u n t i l they leave the study area i n e a r l y October.  During d a y l i g h t hours,  50  Table VIII.  T o t a l Percentage of Tag Recoveries  Total Fish Released  Total Fish Recovered  Percent Recovered  Adult  300  27  9.00  Yearling  389  39  10.03  Young of Year  294  18  6.12  Totals  983  84  8.54  T a b l e IX.  P o s i t i o n of Tagged F i s h Recovered  Position  Recovered  Time of Year  Age Group  Spring  Adult Yearling Young of Year  12 13 0  3 1 0  Fall  Adult Yearling Young of Year  2 2 6  10 21 11  N.E. Set  S.W.  Set  51 from mid-July  u n t i l e a r l y October t h e r e are r e l a t i v e l y few  a d u l t s over t h e beach and i n the v i c i n i t y of t h e k e l p beds. Except f o r a sudden, but b r i e f , end of September, t h e r e  are very few y e a r l i n g s present i n  shallow water from mid-July in  mid-October.  u n t i l they  The young of the year  J u l y and remain segregated mid-August.  i n c r e a s e i n numbers at t h e  leave the study  area  are born e a r l y i n  i n s c h o o l s i n the k e l p beds u n t i l  At t h i s time they s t a r t t o move i n t o deeper  water and by the end of October they have l e f t the study area.  D i u r n a l Movements  The  data obtained  from a s e r i e s of g i l l  net s e t s  made over a 36 hour p e r i o d , at 2 hour i n t e r v a l s , i n d i c a t e d that Cymatogaster e x h i b i t s a d i s t i n c t p a t t e r n of d i u r n a l movements t h a t v a r i e s s e a s o n a l l y . ences between the behavior  Because of s l i g h t  differ-  of a d u l t s and y e a r l i n g s , the r e s -  u l t s are given s e p a r a t e l y f o r t h e two groups.  The c o l l e c -  t i o n s were made i n mid-June, J u l y and August.  The p o s i t i o n s  of t h e g i l l  net s e t s i n t h e study  area are given by F i g u r e  20 . Adult F i s h F i g u r e s 26, 27 and 28 g i v e t h e d i u r n a l movement p a t t e r n s of a d u l t Cymatogaster i n mid-June, J u l y and August. F i g u r e 26 shows t h a t i n mid-June t h e r e are r e l a t i v e l y  large  52  F i g u r e 26.  D i u r n a l movement p a t t e r n s of mature i n June.  Cymatogaster  F i g u r e 27.  D i u r n a l movement p a t t e r n s of mature in July.  Cymatogaster  F i g u r e 28.  D i u r n a l movement p a t t e r n s of mature i n August.  Cymatogaster  •SUNSET  .SUNRISE  00 TIME  TIME  1300  1500  1700  1900  030oT6soO  21SUNSET 002 |300~ 0 1 0 0 -SUNRISE DEEP NETS I SHALLOW NETS  1 = 1 DEEP NETS ^ SHALLOW NETS m  53  numbers of f i s h over the beach area d u r i n g the d a y l i g h t hours,  from 0500 t o 2100 hours.  Between sunset  and s u n r i s e  (2300 - 0.300 hours), however, very few a d u l t s were taken by the g i l l n e t s .  The p a t t e r n of d i u r n a l movements d u r i n g the  pre-spawning p e r i o d i n v o l v e s the m i g r a t i o n of a d u l t s from over the beach and k e l p beds i n t o deeper water when t h e r e is  a decrease  i n light  i n t e n s i t y caused by sunset.  s u n r i s e , and i n c r e a s i n g l i g h t  With  i n t e n s i t y , t h e r e i s a move-  ment onto the beach area of adult f i s h from deeper water. The the study  r e l a t i v e l y high numbers of f i s h found  area d u r i n g d a y l i g h t hours c o r r e l a t e s w i t h  obtained from the study of seasonal movements.  over data  F i g u r e 22  shows t h a t d u r i n g the e n t i r e pre-spawning p e r i o d a d u l t s are taken  i n f a i r numbers i n the v i c i n i t y  of the k e l p beds and  over the beach. In J u l y and August t h e r e i s complete r e v e r s a l of the d i u r n a l movement p a t t e r n e x h i b i t e d by Cymatogaster i n June ( F i g u r e s 27 and 28). present  over the study area d u r i n g the d a y l i g h t hours, but,  with darkness, of  adult f i s h .  deep nets, then  t h e r e i s an onshore movement of l a r g e numbers The m a j o r i t y of f i s h are f i r s t l a t e r on i n the evening  the shallow n e t s . sity and  There are r e l a t i v e l y few f i s h  caught by the  they are taken i n  As dawn approaches and the l i g h t  i n c r e a s e d , the a d u l t s move i n t o s l i g h t l y are caught by the deep nets again.  very few a d u l t s are found  i n the study  inten-  deeper water  With f u l l d a y l i g h t , area.  54  The  complete r e v e r s a l  of the pattern  movement between m i d - J u n e and J u l y w i t h spawning the  daylight  beach,  a f t e r spawning (Figure  temperature, l i g h t  relatively  Figures  gaster .  Figure  duration  s h a l l o w water  o f t i m e when s u c h as  and t u r b i d i t y r e m a i n  that  Figures  (Figure  increasing  26).  They  the daylight  and August  o f d i u r n a l movement p a t t e r n s  light  follow the are i n  hours, but  darkness.  30 and 31 f o r J u l y  Cymatogaster  movement  f o r y e a r l i n g Cymato-  the yearlings  as t h e a d u l t s  during  the diurnal  and August  over t h e beach d u r i n g  deeper water  same r e v e r s a l  July  29 i n d i c a t e s  same g e n e r a l p a t t e r n  with  hours i n  environmental factors  29, 30 and 31 g i v e  i n mid-June,  decreasing  During the period  over t h e  Fish  patterns  adult  s h a l l o w water  spend  constant. Yearling  in  22).  associated  the adults  t h e y spend t h e d a y l i g h t  r e v e r s a l takes place,  water  i s probably  B e f o r e spawning  hours i n r e l a t i v e l y  deeper water the  activities.  of d i u r n a l  show t h e  exhibited  i s a l s o shown by t h e y e a r l i n g s . i n t e n s i t y there  by With  i s an o n s h o r e movement,  intensity the yearlings  move i n t o  deeper  water . Figure  30 shows t h e e f f e c t o f b r i g h t  on t h e d i u r n a l movement p a t t e r n after by  dark t h e m a j o r i t y  moon  of y e a r l i n g f i s h .  light Just  o f f i s h were t a k e n b y t h e deep  2300 h o u r s t h e f i s h were i n s h a l l o w e r w a t e r  and were  nets,  55  F i g u r e 29.  D i u r n a l movement p a t t e r n s o f y e a r l i n g Cymatogaster i n June. —•  F i g u r e 30.  D i u r n a l movement p a t t e r n s o f y e a r l i n g Cymatogaster in July.  F i g u r e 31.  D i u r n a l movement p a t t e r n s o f y e a r l i n g Cymatogaster i n August.  —  5  NUMBER OF FISH O  u O  i  _»  O  O  u O  —»  i  O  O  NUMBER OF FISH  NUMBER OF FISH  M  O  c  -*  O  n  o O  u  O  i  "O  o O  O  5 on  yi O  -»  O  O  ro  _A  O  Oi  O  O  ro  ui o  56  caught by the shallow n e t s .  Moonrise occured between 2300  and 0100 hours and the y e a r l i n g s moved i n t o deeper water. By 0300 hours they had r e t u r n e d t o the s h a l l o w s , and, w i t h the  dawn between 0300 and 0500 hours, the y e a r l i n g s moved o f f  the  beach i n t o deeper water.  F i g u r e 31 shows the d i u r n a l  movements of y e a r l i n g on two cloudy n i g h t s . increase i n l i g h t  There was no  i n t e n s i t y due t o the moon and no c o r r e s -  ponding movement of the f i s h i n t o s l i g h t l y deeper water.  The  f i s h were f i r s t taken by the deep nets, then between 2300 and 0100 hours they moved i n t o the shallow beach area.  By 0300  hours they were again moving i n t o deeper water and by 0500 hours ( a f t e r s u n r i s e ) t h e r e were very few y e a r l i n g s taken by the  g i l l nets over the study area. It i s suggested that  light  i n t e n s i t y i s the primary  f a c t o r governing the d i u r n a l onshore and o f f s h o r e movements of  adult and y e a r l i n g Cymatogaster.  The cause of the r e v e r -  s a l of the p a t t e r n of d i u r n a l movement between mid-June and mid-July i s not known.  57  SEASONAL AND  DIURNAL FEEDING HABITS AND  FOOD PREFERENCES  Seasonal Feeding Habits  A study was  conducted t o a s c e r t a i n the f e e d i n g  h a b i t s and food p r e f e r e n c e s of Cymatogaster d u r i n g the peri o d the f i s h are present i n the Keates  I s l a n d study area.  The contents of the g a s t r o - i n t e s t i n a l t r a c t s of 217  fish,  which had been taken at r e g u l a r i n t e r v a l s from e a r l y June t o the middle of October, were analysed. e n t i r e t r a c t were emptied  The contents of the  into a small glass dissecting  dish  and then examined with a b i n o c u l a r microscope under m a g n i f i c a t i o n s v a r y i n g from 6.3  to  40X.  Twelve f i s h from each c o l l e c t i o n made through the study p e r i o d were s e l e c t e d f o r examination,  t h r e e male  and t h r e e female a d u l t s , and t h r e e male and t h r e e female lings.  Before the contents of the g a s t r o - i n t e s t i n a l t r a c t  were p l a c e d i n the d i s s e c t i n g d i s h , a v i s u a l estimate made of the percentage was  year-  of the t o t a l volume of the t r a c t  taken up by food organisms.  i n g microscope,  was  With the a i d of the  the food organisms  under the g e n e r a l headings  that  dissect-  were i d e n t i f i e d and p l a c e d  of mussels  (Mytilus edulus),  algae, and b a r n a c l e s , which are a s s o c i a t e d with the ocean bottom, and zooplankton  which are g e n e r a l l y c o n s i d e r e d t o  be f r e e f l o a t i n g organisms. t o Order or Sub-Class  The zooplankton were i d e n t i f i e d  and p l a c e d under two  g e n e r a l headings:  58 the  first  b e i n g l a r g e zooplankton which i n c l u d e d amphipods,  isopods, mysids, chironomids, and l a r g e copepods.  The second  heading was s m a l l zooplankton under which were grouped s m a l l copepods  and the c y p r i s and n a u p l i u s stages of t h e l i f e  c y c l e of s e v e r a l c r u s t a c e a n s .  A f t e r the food organisms had  been i d e n t i f i e d and grouped, e s t i m a t e s were then made of t h e approximate percentage each group made up of t h e t o t a l  food  volume. F i g u r e 32 shows the volume and percentage composit i o n of t h e food organisms found i n the g a s t r o - i n t e s t i n a l t r a c t of Cymatogaster to  mid-October.  at r e g u l a r i n t e r v a l s from e a r l y  June  F i g u r e 39 i n d i c a t e s that at times t h e r e are  d i f f e r e n t f e e d i n g and food p r e f e r e n c e s e x h i b i t e d by adult and y e a r l i n g f i s h and s l i g h t  d i f f e r e n c e s between males and  females as w e l l as many s i m i l a r i t i e s . The t o t a l volume of food found i n the stomachs of a d u l t s and y e a r l i n g s v a r i e s throughout the time t h e f i s h are i n the study area.  At t h e time when Cymatogaster  f i r s t move  i n t o t h e r e l a t i v e l y s h a l l o w waters of the study area, t h e water temperatures are warming up and food organisms are becoming more abundant  and a v a i l a b l e .  occuring with increasing r e g u l a r i t y  P l a n k t o n blooms s t a r t  (Hardy, 1956) and the  young b a r n a c l e s and mussles are b e g i n n i n g t o s e t t l e and grow. An i n c r e a s e i n water temperature may a l s o cause an i n c r e a s e i n the m e t a b o l i c r a t e s of the f i s h and, r e l a t e d t o t h i s , an o v e r a l l i n c r e a s e i n a c t i v i t y i n c l u d i n g f e e d i n g (Brown,  1957).  YEARLING  MALES  FULL 1/2 EMPTY  FULL  1/2 EMPTY  FULL  1/2  EMPTY  9 JUNE  13  MATURE FULL  l/  16  2 0  24  29  4 JULY  9  12  23  8 AUG.  16  23  30  5 SEPT.  20  29  24  29  4 JULY  9  12  23  8 AUG.  16  23  30  5 SEPT  20  29  FEMALES  1—  minium  2  EMPTY  «-  9  JUNE  13  16  2 0  nffll  ALGAE  ggg  MUSSLE  EHJ  F i g u r e 32.  Volume and composition of food organisms r e g u l a r i n t e r v a l s from June to October.  • •  LARGE  ZOOPLANKTON  SMALL  ZOOPLANKTON  BARNACLE  i n the g a s t r o - i n t e s t i n a l t r a c t a t g  60  In e a r l y tonic tial  s p r i n g the y e a r l i n g  organisms.  The  adult f i s h  amount o f z o o p l a n k t o n ,  f o r m an  important  June t h e  segment  m a j o r i t y of f i s h  are  of t h e i r  had  tracts  on t h e  diet.  During  half  planksubstan-  and  t h e month o f  a d u l t and  full,  yearling  the  great  b e e n f e e d i n g t o some e x t e n t .  In  early  and  their  t o f e e d more i n t e n s i v e l y  hand,  almost  t o be  stop  full.  The  adult  feeding entirely.  adult f i s h  embryos w i t h i n t h e u t e r u s s i d e r a b l e volume o f t h e  of the  Both sexes of y e a r l i n g  just  e a r l y October. the  leave the At t h i s  time  amount o f f o o d f o u n d The  early  August  of  September when t h e r e  of  food found The  both  yearling  l e a v i n g the  i n the  area  t o eat  in late  study  September  to feed actively  intensively until  or  adult Cymatogaster i s probably  in  the  i s a marked r e d u c t i o n i n t h e  gastro-intestinal  area  until  digestive tract.  end  amount  tract.  r e d u c t i o n of f e e d i n g i n t e n s i t y and  July  a  i s a marked r e d u c t i o n i n  again begin  continue  the  a con-  Cymatogaster m a i n t a i n  there  i n the  adult f i s h and  study  to  cavity.  i n t e n s i v e r a t e of f e e d i n g from e a r l y  before they  and  f e m a l e a r e t a k i n g up  abdominal  This  corresponds  p e r i o d when t h e male t e s t e s a r e g r e a t l y e n l a r g e d  relatively  mussels  but  marked r e d u c t i o n i n f e e d i n g by t h e the  barnacles,  of both  are u s u a l l y found  other  on  also eating a  algae,  more t h a n  yearlings begin  digestive fish,  but  feed primarily  gastro-intestinal tracts  C y m a t o g a s t e r were r a r e l y  J u l y the  fish  just  e x h i b i t e d by  prior  to  associated with  their decreas-  61  i n g water temperatures.  As temperature  l e v e l s d e c l i n e , the  metabolic r a t e s and o v e r a l l a c t i v i t y l e v e l s of the f i s h decline.  also  At t h i s time of year both the a d u l t s and y e a r l i n g s  s t a r t t o move out i n t o deeper water where food become l e s s a v a i l a b l e .  organisms  A decrease i n f e e d i n g a c t i v i t y ,  a s s o c i a t e d w i t h lower water temperatures,  coupled w i t h a r e -  d u c t i o n i n t h e amount of food a v a i l a b l e presumably  accounts  f o r the r e d u c t i o n i n the amount of food found i n t h e d i g e s t i v e t r a c t s of Cymatogaster i n t h e l a t e  fall.  Adult and y e a r l i n g Cymatogaster show many s i m i l a r i t i e s i n t h e i r p r e f e r e n c e of food organisms. mussels  By volume,  and algae make up the most important c o n s t i t u e n t s of  Cymatogaster's  diet.  Mussels were found i n 44.5% of a l l d i -  g e s t i v e t r a c t s examined and algae was found i n 57.4%. copepods were t h e most f r e q u e n t l y encountered  food  Small  organism.  They were present i n 51.2% of t h e a d u l t s sampled and 94.2% of the y e a r l i n g s .  At d i f f e r e n t p e r i o d s of t h e year b a r n a c l e s  appear t o be an important c o n s t i t u e n t i n the d i e t of Cymatogaster and were present i n v a r y i n g q u a n t i t i e s i n 25.3% of the d i g e s t i v e t r a c t s examined.  Large zooplankton were r a r e l y an  abundant item i n Cymatogaster's  d i e t , though they were pre-  sent i n l i m i t e d q u a n t i t i e s i n 16.5% of the specimens examined. D i f f e r e n c e s i n food p r e f e r e n c e s are e x h i b i t e d by adult and y e a r l i n g Cymatogaster and t h e r e are a l s o d i f f e r e n c e s shown by male and female f i s h . copepods, make up an important  Small zooplankton,  mainly  segment of the d i e t of year-  62  ling  fish  and were f o u n d  of t h e d i g e s t i v e t r a c t s 50%  i n varying quantities examined.  h a d t a k e n some s m a l l z o o p l a n k t o n ,  duals than d i dthe y e a r l i n g up  Adult f i s h ,  f a r less of the t o t a l  yearlings  first  month o f J u n e , of t h e t o t a l During t h i s eat  arrive  i n t h e s t u d y a r e a , and t h r o u g h t h e  period the adults,  females  other  group  found  i n over  i n their  feed mainly  as t h i s  40% of t h e females  on b a r n a c l e s , mus-  a n a l y s i s showed  food organism  sampled  deal of s i m i l a r i t y  that  there i s a great  and y e a r l i n g C y m a t o g a s t e r .  a l g a e and s m a l l m u s s e l s ,  time  are present  greater  items  area.  though  they  are found  i n larger  i n the digestive tracts  during the  Small  a r e t a k e n r e g u l a r l y by b o t h  frequency  Barnacles  i n the study  Two t y p e s  make up most o f  volume o f f o o d e a t e n by C y m a t o g a s t e r  yearlings,  was  and o n l y 11.4% o f  the t o t a l  m a i n l y copepods,  do any  i n t h e f e e d i n g h a b i t s and f o o d p r e f e r e n c e  of adult  of f o o d organisms,  they  that  combined.  In summary i t may be s a i d  of both sexes  tracts.  however, a l t h o u g h t h e y do  The d i g e s t i v e t r a c t  o f Cymatogaster,  portion  digestive  t e n d t o e a t many more b a r n a c l e s t h a n  the o t h e r groups  indivi-  When t h e  s m a l l z o o p l a n k t o n make up t h e m a j o r  and a l g a e .  over  and t h e s m a l l z o o p l a n k t o n made  volume o f f o o d f o u n d  adult  although  a t e f a r fewer  volume o f f o o d e a t e n .  some s m a l l z o o p l a n k t o n ,  sels  i n over 90%  zooplankton,  a d u l t s and  numbers and w i t h of the y e a r l i n g s .  and," l a r g e z o o p l a n k t o n may a t t i m e s be i m p o r t a n t  i n the diets  o f a l l groups  o f Cymatogaster,  and m a t u r e  63 females  tend t o eat more b a r n a c l e s than the other t h r e e  groups combined. In June, when they f i r s t  move i n t o the area, a l l  groups of Cymatogaster are f e e d i n g a c t i v e l y though t h e i r d i g e s t i v e t r a c t s are r a r e l y more than h a l f f u l l .  In e a r l y  J u l y the f e e d i n g i n t e n s i t y of the y e a r l i n g s i n c r e a s e s and at t h i s time t h e r e i s a l s o a marked r e d u c t i o n of the f e e d ing i n t e n s i t y e x h i b i t e d by the adult f i s h .  By e a r l y August  the a d u l t s are a c t i v e l y f e e d i n g again and both a d u l t s and y e a r l i n g s maintain a high r a t e of f e e d i n g a c t i v i t y August and most of September.  through  J u s t p r i o r t o the time when  they leave the study area, both a d u l t s and y e a r l i n g s e x h i b i t a marked r e d u c t i o n i n f e e d i n g .  D i u r n a l Feeding  Habits  A study was  conducted  t o a s c e r t a i n the  diurnal  f e e d i n g h a b i t s and food p r e f e r e n c e s of Cymatogaster. samples were taken at two  hour i n t e r v a l s over  hour p e r i o d s i n mid-June, J u l y , and August. of the d i g e s t i v e t r a c t s of 430 same m i c r o s c o p i c techniques  Serial  thirty-six The  contents  f i s h were examined by  as were a p p l i e d i n the  the  seasonal  f e e d i n g study and the i n d i v i d u a l food organisms were grouped under the same  headings.  For each two  hour i n t e r v a l two  adult females were examined as were two  adult male and y e a r l i n g males  two and  64 two  yearling  females.  s p e c i m e n was An  divided  e s t i m a t e was  each s e c t i o n of  into  made o f  t h a t was  gastro-intestinal four d i s t i n c t  by  food  and  composition  of  the d i g e s t i v e  g i v e s a composite  tract  data obtained from were combined iod.  each  and  t o t a l volume o f then  the  contents  2100  and  36  Detailed  and  37  yearling of  The  These data  are p l o t t e d  over  vals,  e s t i m a t e s may  tract.  The  a l s o be  compared on  items  times  of  very  adult  the  m a l e s , and  this  hour  hauls  hour  can  h o u r p e r i o d a t two  be o b t a i n e d o f t h e t i m e through  initiation  the  per-  yield  a  and  the  and  hour  inter-  i t takes f o r  c e s s a t i o n of  A l l t h e above f a c t o r s may  c o n d i t i o n continued  given.  gastro-intestinal  and  i n the g a s t r o - i n t e s t i n a l  (2300-0300).  s e t s of  food organisms are  shows t h a t i n J u n e , a t 2100  food  24  respectively.  figures  a s e a s o n a l b a s i s as w e l l as age  little  of darkness  a 24  to pass  ascertained.  F i g u r e 34  volume  t o t a l volume o f f o o d  by volume o f  food  two  f o r a 24  females  these  composition  individual  the  g i v e t h e same d a t a f o r m a t u r e  examination  information.  The  i n t h e 36  picture  percentage  thus  of  i n the f o u r s e c t i o n s  August.  t o 0500 h o u r s  y e a r l i n g m a l e s , and  great d e a l of  picture  of a d u l t Cymatogaster males over  t o g i v e an o v e r a l l  F i g u r e s 35,  females,  was  the  food organisms found  hour p e r i o d s i n mid-June, J u l y  may  of  s e c t i o n s (Figure 33).  the f r a c t i o n of  occupied  tract  e a c h s e c t i o n were e x a m i n e d s e p a r a t e l y . F i g u r e 34  of  The  feeding then  be  sex. hours  tract  of  throughout  S h o r t l y a f t e r dawn, w i t h  there the  the  the  hours  increase  F i g u r e 33.  The f o u r s e c t i o n s of the g a s t r o - i n t e s t i n a l of Cymatogaster.  tract  M A T U R E  M A L E S  2 1 0 0  FULL  2 3 0 0  0 1 0 0  0 3 0 0  0 5 0 0  0 7 0 0  0 9 0 0  1 1 0 0  1 3 0 0  r-  1 5 0 0  1 7 0 0  1  1 / 2  EMPTY  1  1  1 iI 1P 11 1  1 2  3  1 9 0 0  1  4  J U N E  2 1 0 0  2 3 0 0  0 1 0 0  0 3 0 0  0 5 0 0  0 7 0 0  0 9 0 0  1 1 0 0  1 3 0 0  15 0 0  1 7 0 0  1 9 0 0  FULL  1 / 2  EMPTY  1 2 3 4 J  1  2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  _ 1  ____ 2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  3  4  U L Y  2 1 0 0  2 3 0 0  0 1 0 0  0 3 0 0  0 5 0 0  0 7 0 0  0 9 0 0  1 1 0 0  1 3 0 0  1 5 0 0  1 7 0 0  1 9 0 0  FULL i 1 / 2  EMPTY  -  M 1  2  3  4  1  2  3  A U G U S T  F i g u r e 34.  4  1  2  3  4  1  2  3  _ 4  _ 1  2  3  4  1  2  3  4  1  2  3  4  1  2  3  4  _LTJ _J E3  1  2  3  4  ALGAE MUSSLE BARNACLE  1  2  3  4  1  2  3  LARGE SMALL  4  1  2  ZOOPLANKTON ZOOPLANKTON  Volume and composition of food organisms i n the f o u r s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of mature male Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August.  67  in  light  i n t e n s i t y , the males began t o f e e d on l a r g e zoo-  plankton  (copepods).  By 0700 the f i r s t  s e c t i o n of the gut  was f u l l  and there were some food organisms i n the second  and t h i r d s e c t i o n s , and by 0900 there was food i n a l l four sections.  The adult males stopped" f e e d i n g between the hours  of 0900 and 1100 and as time passes the s u c c e s s i v e  reduction  of the volume of food can be seen i n s e c t i o n s one t o four of the g a s t r o - i n t e s t i n a l t r a c t , u n t i l by 2100 hours there were only t r a c e s of food organisms t o be found i n s e c t i o n f o u r . In J u l y , the adult males appear t o feed at a lower o v e r a l l i n t e n s i t y as t h e i r stomachs were never f u l l ,  but they  must f e e d c o n s t a n t l y from dawn t o dark (0700 t o 2100) as t h e r e was u s u a l l y always some food i n the f i r s t the d i g e s t i v e t r a c t . fed  mainly on algae  s e c t i o n of  At t h i s p e r i o d of the season the f i s h and m y t i l u s .  As i n June, l i g h t i n t e n s i t y  seemed t o govern the i n i t i a t i o n of f e e d i n g . The  f e e d i n g h a b i t s and f o o d p r e f e r e n c e s  exhibited  by mature male Cymatogaster i n August were q u i t e s i m i l a r t o those of J u l y except that the f e e d i n g i n t e n s i t y had i n c r e a s e d t o some extent tinal tract,  as was i l l u s t r a t e d by the f u l l  gastro-intes-  and the f i s h stopped f e e d i n g by 1700 hours.  Again f e e d i n g seemed t o be i n i t i a t e d w i t h the i n c r e a s e d light  i n t e n s i t y a s s o c i a t e d with  sunrise.  F i g u r e 35 shows that by 2100 hours i n June the mature females have stopped a c t i v e l y f e e d i n g and that was no f e e d i n g throughout the hours of darkness.  there  With sun-  MATURE 2100  FEMALES 2300  0100  030O  0500  0700  0900  1100  1300  1500  1700  1900  2300  0100  0300  0500  0700  0900  1100  1300  1500  1700  1900  JUNE  2100 FULL  t—  JBmH  EMPTY  12  2100  AUGUST  Figure 3 5 .  2300  34  12  3 4  0100  12  0300  34  12  0500  3 4  12  0700  3 4  12  0900  3 4  12  3 4  11 0 0  12  3  4  1300  12  3 4  1500  _  1 2  3 4  1700  12  3 4  1900  _  HUD  ALGAE  ^  LARGE  ZOOPLANKTON  659  MUSSLE  • •  SMALL  ZOOPLANKTON  EZD  BARNACLE  Volume and composition of food organisms i n the f o u r s e c t i o n s o f the g a s t r o i n t e s t i n a l t r a c t o f mature female Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August.  69  rise  (0500 hours) they s t a r t e d e a t i n g l a r g e zooplankton  (cope-  pods) , and by 0700 hours many of the p l a n k t o n have reached the second s e c t i o n of the gut.  A f t e r the i n i t i a l  f e e d i n g on  copepods the females s t a r t e d t o f e e d on m y t i l u s and algae between 0700 and 0900 hours and c o n t i n u e d t o do so u n t i l hours when, w i t h d e c r e a s i n g l i g h t  1900  i n t e n s i t y , they ceased f e e d -  ing. In the mid-July sample, which was  taken j u s t  follow-  ing the peak of the spawning p e r i o d , the mature females a l most ceased f e e d i n g e n t i r e l y .  Throughout  the e n t i r e 24  p e r i o d t h e r e were o n l y t r a c e s of food organisms  hour  found i n the  gastro-intestinal tract. In August, again.  the mature females were a c t i v e l y f e e d i n g  They s t a r t e d t o eat w i t h the i n c r e a s e i n l i g h t  s i t y and c o n t i n u e d u n t i l around ceased.  1700  hours when f e e d i n g  During t h i s p e r i o d most d i g e s t i v e t r a c t s were  which i n d i c a t e s t h a t the f i s h were f e e d i n g q u i t e P r o g r e s s i v e l y l e s s food was of  inten-  full  intensively.  found i n the gut d u r i n g the hours  darkness. In mid-June, at the time of sampling, the y e a r l i n g  males ( F i g u r e 36) were mainly f e e d i n g on l a r g e copepods. the mature males, they s t a r t e d e a t i n g a f t e r s u n r i s e and c o n t i n u e d f e e d i n g u n t i l around ing  activity  1300  Like  (0500)  hours when a l l f e e d -  stopped.  In J u l y , the y e a r l i n g males again s t a r t e d f e e d i n g with the s u n r i s e and c o n t i n u e d t o eat a c t i v e l y u n t i l  darkness  Y E A R L I N G  2100  M A L E S  2300  0100  0300  0500  0700  0900  1100  1300  1500  1700  1900  2300  0100  0300  0500  0700  09OO  1100  1300  1500  1700  1900  2300  0100  0300  0500  0700  0900  1100  1300  1500  1700  1900  J U N E  2100  J U L Y  FULL i —  2100  1/2  E M P T Y L-  F i g u r e 36.  LUffl  ALGAE  _  3  LARGE  ZOOPLANKTON  _ _  MUSSLE  MM  SMALL  ZOOPLANKTON  _ _  BARNACLE  Volume and composition of food organisms i n the f o u r s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of y e a r l i n g male Cymatogaster over 24 hour p e r i o d s i n June, J u l y , and August.  o  (2100 h o u r s ) .  At t h i s time of year the f i s h f e e d a c t i v e l y a l l  day long as i s evidenced by the f u l l d i g e s t i v e t r a c t s .  Their  d i e t c o n s i s t s mainly of M y t i l u s and algae w i t h some s m a l l zooplankton . In  August the y e a r l i n g males again s t a r t  w i t h the dawn, eat i n t e n s i v e l y u n t i l around  feeding  1700 hours, when  food i n t a k e i s reduced, and then cease t o f e e d w i t h darkness. In  August,  s i m i l a r t o J u l y , t h e i r main d i e t a r y  constituents  were M y t i l u s and algae, w i t h some s m a l l copepods and b a r n a c l e s . The f e e d i n g h a b i t s and food p r e f e r e n c e s of y e a r l i n g females  ( F i g u r e 37) are v e r y s i m i l a r t o those of y e a r l i n g  males throughout t h e sampling p e r i o d , except that females c o n t i n u e f e e d i n g u n t i l  i n June t h e  1900 hours i n s t e a d of 1300 hours.  Estimates were made o f the time i t took food t o pass from the f i r s t to  s e c t i o n of the g a s t r o - i n t e s t i n a l t r a c t  the l a s t s e c t i o n  appearance first  through  (four) by n o t i n g the time of the f i r s t  of food i n s e c t i o n one ( j u s t a f t e r s u n r i s e ) and the  appearance  of the same type of food i n s e c t i o n f o u r .  E s t i m a t e s were a l s o made of the time i t took f o r the gut t o become empty a f t e r f e e d i n g had ceased. In  June, when the f i s h were e a t i n g l a r g e  copepods,  i t took approximately f o u r hours f o r these food organisms t o pass from s e c t i o n one t o s e c t i o n four i n the mature f i s h f o r both males and females.  In the d i g e s t i v e t r a c t s of the y e a r -  l i n g male and female Cymatogaster, to  i t took food items e i g h t  t e n hours t o move from s e c t i o n one t o s e c t i o n  four.  YEARLING  F E M A L E S  2100  230 0  0100  0300  0 5 00 '  FULL  1/2  I  EMPTY  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  I.  0700  1 2 3 4  0900  1 2 3 4  1100  I  1 2 3 4  1300  1 2 3 4  1500  1700  1 2 3 4  1900  1 2 3 4  1 2 3 4  JUNE  FULL  00  2300  0100  0300  050 0  0700  0900  1100  130 0  150 0  1700  1900  2100  2300  0 1 0 0  0300  0500  0700  0900  1100  13QO  1500  1700  1900  i —  1/2  EMPTY  FULL  i-  1/2  • E M P T Y «-  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  1 2 3 4  AUGUST EID  F i g u r e 37.  ALGAE  G53  MUSSLE  EUl  BARNACLE  E •  1 2 3 4  1 2 3 4  LARGE  ZOOPLANKTON  SMALL  ZOOPLANKTON  Volume and composition of food organisms i n the f o u r s e c t i o n s of the g a s t r o - i n t e s t i n a l t r a c t of y e a r l i n g female Cymatogaster over 24 hour periods i n June, J u l y , and August.  to  73 During t h i s hours  p e r i o d of the  i t took  f o r t h e stomachs of b o t h In J u l y ,  and  year  a d u l t s and  when t h e main d i e t a r y  algae, i t took  through  approximately  to section  It took  hours  i t e m s were m y t i l u s  s i x hours  approximately  t h e same p a s s a g e i n b o t h male and  female  eight  y e a r l i n g s t o empty.  f o r food to  f o u r i n t h e m a t u r e m a l e s and  t h e mature f e m a l e s .  six to eight  approximately  t e n hours  f o u r hours  yearlings.  f o r t h e stomachs of the  pass in  t o make It  a d u l t s and  took  year-  l i n g s t o become empty. In August, w i t h the d i e t in July,  it still  reach section  took  approximately  I t a l s o r e q u i r e d about  y e a r l i n g m a l e s and  females.  machs t o become empty was  rates  however, was  t h e s t u d y p e r i o d , and initiated  The  by t h e  time  again from  feeding habits,  o f C y m a t o g a s t e r may  feature,  s i x hours  f o u r i n t h e mature males, but  i n the females.  The  very similar  to that f o r food  only four  f o u r hours  s i x to eight  i n the  e x h i b i t e d by t h i s was  that  increased light  digestive  and  a l l f o u r groups  sex.  One  throughout  f e e d i n g seemed t o  intensity  sto-  hours.  f o o d p r e f e r e n c e s , and age  to  hours  r e q u i r e d f o r the  vary w i t h season,  found  be  associated with  sunrise. D u r i n g t h e pre-spawning p e r i o d i n June, the and  yearling  fish  but  the males f e d o n l y u n t i l  continued u n t i l time  i t took  of both  evening.  sexes  started  early  sunrise,  afternoon while the  During t h i s  f o r f o o d organisms  feeding with  mature  females  p e r i o d of the year,  t o pass  from  the f i r s t  the  sec-  74 tion  of the g a s t r o - i n t e s t i n a l t r a c t  g r e a t l y between a d u l t s twice time had  as  and y e a r l i n g s ,  long i n the y e a r l i n g s .  The  last  digestive  c e a s e d , were a p p r o x i m a t e l y t h e same and  period,  the i n t e n s i t y  greatly  reduced,  dawn and may  The  f o r both  t h e peak o f t h e  spawning  almost  or n i g h t .  t a k e i n a few At t h i s  around  i n the males t e n hours  t o remain  of the y e a r l i n g s ,  feeding  food  organisms  time of year the  instead  of f o u r .  eight  The  hours.  increased their  the time).  The  than  digestive  same.  The  tinued  eating u n t i l  yearlings started  By  late  mid-August  feeding  i t d i d i n June  rates  remained  rate  of  (about  and  digestive  Both  sexes  feeding  one  the half  approximately the  to feed with sunrise  and  con-  of both sexes  were  continued to  feed  evening. t h e mature f i s h  a g a i n and t h e y e a r l i n g s  an i n t e n s i v e r a t e .  rate  a l s o d e c r e a s e d in< t h e  and t h e f o o d p a s s e d much more q u i c k l y t h r o u g h  gastro-intestinal tract  at  until  approximately s i x hours  at a r o u n d  however,  was  entirely  time the males s t a r t e d  f e m a l e s may  taking  appeared  actively  the  feeding  of t h e mature f i s h  o f f o o d t h r o u g h t h e gut  the females  in July  after  or  (8 h o u r s )  t h e f e m a l e s had  At t h i s  o f t h e day  mature f i s h ,  rates  least  rates,  c o n t i n u e t o e a t s m a l l amounts o f f o o d  evening.  of passage  after  of f e e d i n g  i n fact  stopped feeding.  anytime  at  yearlings. In m i d - J u l y , j u s t  late  differed  requiring  i t t a k e s f o r a s t o m a c h t o empty i t s e l f  adults  at  t o the  F e e d i n g was  i n i t i a t e d with  increased  75 light  i n t e n s i t y and continued u n t i l evening.  The r a t e of  passage through the d i g e s t i v e t r a c t of food remained a p p r o x i mately t h e same f o r t h e mature males and both sexes of yearl i n g s , but was g r e a t l y i n c r e a s e d i n the mature females.  The  d i g e s t i v e r a t e s again remained the same. In summary i t may be s t a t e d t h a t the f e e d i n g h a b i t s , food p r e f e r e n c e s , r a t e of passage of food through t h e d i g e s tive tract  and the d i g e s t i v e r a t e s of Cymatogaster may vary  w i t h time of year, age and sex.  76  DISCUSSION  Cymatogaster e x h i b i t s r e l a t i v e l y complex p a t t e r n s of s e a s o n a l and d i u r n a l movements t h a t may time of year and w i t h the age  vary w i t h the  and sex of the i n d i v i d u a l  fish.  Most authors have been able t o c o r r e l a t e v a r i o u s environmental  f a c t o r s such as l i g h t , temperature,  f e r e n c e s or a combination  food p r e -  of these f a c t o r s w i t h d i u r n a l move-  ments and s e a s o n a l depth p r e f e r e n c e s .  Throughout the present  study, Cymatogaster seemed t o be i n f l u e n c e d more by  light  than by any other aspect of t h e i r p h y s i c a l environment. In the marine environment, s t u d i e s by H i c k l i n g (1927), Richardson  (1952),  and Nomura (1958) have demon-  s t r a t e d that the d i u r n a l m i g r a t i o n s e x h i b i t e d by hake, s a r dines, h e r r i n g , and p i l c h a r d s are r e l a t e d t o underwater intensity.  S t u d i e s i n the freshwater environment have a l s o  shown t h a t i n some cases l i g h t Bryon and Howell and Wisley  light  i n t e n s i t y may  be  important.  (1946), Carlander and C l e a r y (1949),  Hasler  (1958) observed t h a t v e r t i c a l d i s t r i b u t i o n of the  f i s h e s under o b s e r v a t i o n was  r e l a t e d t o the i n t e n s i t y of  i l l u m i n a t i o n at v a r i o u s depths.  However, Dendy (1945) ob-  s e r v e d t h a t the v e r t i c a l d i s t r i b u t i o n of game f i s h i n a r e s e v o i r showed no r e l a t i o n t o l i g h t  intensity.  some i n s t a n c e s , a species' r e a c t i o n t o l i g h t vary from year t o year.  Also, i n  intensity  Lorz (1962) found t h a t i n  kokanee were not present i n areas where the l i g h t  may  1961 intensity  77 *.  was above a c e r t a i n value, but i n 1959 t h e i r presence was noted through a l l ranges of l i g h t  intensity.  S t u d i e s have shown that under n a t u r a l c o n d i t i o n s p e l a g i c f i s h e s of both the marine and f r e s h water may keep w i t h i n a given range of l i g h t v e r t i c a l migrations.  habitats  i n t e n s i t y by making  In most i n s t a n c e s these d i u r n a l migra-  t i o n s have i n v o l v e d t h e movement of f i s h from deep t o s h a l low water w i t h the f a l l i n g l i g h t  i n t e n s i t y associated with  evening, and the r e t u r n t o deeper water w i t h t h e i n c r e a s e i n i l l u m i n a t i o n at dawn.  Reverse m i g r a t i o n s are a l s o known.  However, t h e r e are no i n s t a n c e s i n the l i t e r a t u r e that i n v o l v e the sudden r e v e r s a l of d i u r n a l movement p a t t e r n such as i s e x h i b i t e d by Cymatogaster. r e v e r s a l i s unknown.  The cause of t h i s  sudden  The environmental f a c t o r s such as water  temperature and i l l u m i n a t i o n , as w e l l as f e e d i n g h a b i t s and food p r e f e r e n c e s , remain r e l a t i v e l y s i m i l a r over the p e r i o d of change, perhaps i n d i c a t i n g t h a t the b a s i s of the r e v e r s a l i s p h y s i o l o g i c a l r a t h e r than environmental. There seems t o be l i t t l e m i g r a t i o n s observed f o r both mature are governed by changes i n l i g h t  doubt that the d i u r n a l and y e a r l i n g  intensity.  Cymatogaster  In June, very  few f i s h are found i n s h a l l o w water a f t e r sunset, but t h e r e i s a great i n c r e a s e i n numbers a f t e r the l i g h t i n c r e a s e s at s u n r i s e .  A f t e r the r e v e r s a l ,  intensity  i n J u l y and  August, Cymatogaster become much more abundant  i n shallow  water a f t e r sunset, and move back i n t o deeper water w i t h the  78 dawn. sity,  As f u r t h e r evidence of the importance of l i g h t  inten-  i n J u l y the i n c r e a s e d i l l u m i n a t i o n a s s o c i a t e d w i t h  moonrise caused y e a r l i n g f i s h t o move i n t o deeper water. e f f e c t of l i g h t  i s a l s o very evident i n the data o b t a i n e d  from the study of d i u r n a l f e e d i n g h a b i t s .  Regardless of the  p e r i o d of sampling, the i n i t i a t i o n of f e e d i n g was a s s o c i a t e d with an i n c r e a s e of l i g h t of darkness.  The  invariably  intensity after a period  A l s o , w i t h r a r e e x c e p t i o n s , no f e e d i n g o c c u r r e d  d u r i n g the hours of darkness. In the freshwater environment, that temperature may  p l a y an important r o l e i n governing the  s p a t i a l d i s t r i b u t i o n of f i s h e s 1941,  Dendy, 1945,  i t has been suggested  (Fry, 1937,  and Ferguson,  1958).  H i l e and  Juday,  However, Lorz (1962)  found that the v e r t i c a l d i s t r i b u t i o n of kokanee c o u l d not have been c o n t r o l l e d d i r e c t l y by temperature.  In N i c o l a  Lake, r e g a r d l e s s of thermal s t r u c t u r e , kokanee undertook  diel  v e r t i c a l movements. The marine environment undertaken,  where the present study  was  i n the S t r a i t of G e o r g i a and the southern i n l e t s  which enter i n t o i t ,  i s c h a r a c t e r i z e d by s t a b l e thermal s t r a -  t i f i c a t i o n of the s u r f a c e l a y e r due t o summer h e a t i n g .  Sur-  f a c e temperatures u s u a l l y range from 10° t o 18° C. d u r i n g the warmer seasons; the deeper  l a y e r s below the t h e r m o c l i n e  range from 5° t o 8.5° C. throughout the year.  During winter  months, when s t r a t i f i c a t i o n breaks down, temperatures f o r the e n t i r e water mass u s u a l l y range from 5° t o 8.5° C.  (Pickard,  79  1961) . There are i n d i c a t i o n s that t h e r e may be a r e l a t i o n s h i p between t h e s e a s o n a l m i g r a t i o n s and depth p r e f e r e n c e s of Cymatogaster  and changes in. water temperature.  when t h e s u r f a c e water temperatures appear  are r i s i n g  i n the study area, and i n f a l l ,  t u r e s are f a l l i n g , the f i s h movements of Cymatogaster,  the f i s h  when water  leave the area.  In s p r i n g ,  tempera-  The d i u r n a l  however, do not seem t o be d i r e c -  tly  r e l a t e d t o temperature.  the  t h e r m o c l i n e d u r i n g a l l p e r i o d s of the day and night  d u r i n g the study p e r i o d .  first  The f i s h moved f r e e l y through  A l s o , t h e r e was very l i t t l e  differ-  ence between the s u r f a c e and deeper water temperatures of June and J u l y when the r e v e r s a l of the d i u r n a l movement pattern occurred. Perhaps temperature may p l a y some r o l e i n t h e v e r t i c a l d i s t r i b u t i o n of Cymatogaster it  i s l i k e l y that temperature  other environmental f a c t o r s . temperature, of  fish  on a s e a s o n a l b a s i s , but  i s a c t i n g i n combination w i t h Ferguson  (1958) s t a t e s "...  i f a c t i n g alone, can determine t h e d i s t r i b u t i o n  i n l a b o r a t o r y apparatus.  F a c t o r s such as l i g h t ,  c o n d i t i o n e d response r e l a t e d t o f e e d i n g r o u t i n e s , and s o c i a l behaviour can i n t e r f e r e with e x p r e s s i o n of the response t o temperature." S e v e r a l authors have found that f e e d i n g h a b i t s and food p r e f e r e n c e s may have an e f f e c t on the v e r t i c a l b u t i o n s of some f i s h e s .  F r y (1937) found that C i s c o  distriremained  80 , i n t h e e p i l i m n i o n i n t h e summer f o r some t i m e t o f e e d u p o n emerging m a y f l i e s , even i f temperature favorable. through  c o n d i t i o n s became u n -  M a r t i n (1952) showed t h a t l a k e t r o u t came up  t h e t h e r m o c l i n e t o f e e d on p e r c h c o n c e n t r a t e d  warmer w a t e r .  Lorz  (1962) f o u n d  t i o n o f k o k a n e e i n some y e a r s  that the v e r t i c a l  i n the  distribu-  a p p e a r e d t o be r e l a t e d t o d i e t  i n t h e e a r l y s p r i n g a n d summer. The little  study  i n d i c a t e s that there i s probably  r e l a t i o n s h i p b e t w e e n t h e s e a s o n a l and d i u r n a l  preferences and  present  a n d f e e d i n g h a b i t s o f C y m a t o g a s t e r and s e a s o n a l  d i u r n a l movements a n d d e p t h  items, such  food  preferences.  Principal  food  a s ' M y t i l u s , a l g a e , and b a r n a c l e s , a r e f o u n d  both  i n t h e u p p e r s u b - t i d a l and i n t e r - t i d a l e n v i r o n m e n t s ,  and a r e  available t o the f i s h regardless of the l e v e l of the t i d e or the temperature  of t h e water.  ton are a l s o found togaster .  throughout  Since the primary  f i s h throughout  Both  l a r g e and s m a l l  t h e d e p t h s f r e q u e n t e d by Cymafood items  are available t o the  t h e d e p t h s f r e q u e n t e d b y t h e s p e c i e s , and t h e  stomach c o n t e n t s o f f i s h t a k e n from d i f f e r e n t contained similar preferences and  zooplank-  d e p t h s have  f o o d i t e m s , i t seems u n l i k e l y t h a t  and f e e d i n g h a b i t s h a v e much e f f e c t  d i u r n a l depth  d i s t r i b u t i o n s of Cymatogaster.  food  on s e a s o n a l  81 C o r r e l a t i o n of Age and Growth, Movement, and Stomach Content A n a l y s i s Data  A f t e r f o r m a t i o n of the annulus i n e a r l y  spring  (around m i d - A p r i l ) Cymatogaster probably s t a r t s t o feed at a higher i n t e n s i t y as the water temperature begins t o r i s e . The i n c r e a s e i n r a t e of f e e d i n g may  be due t o s e v e r a l f a c t o r s .  Rise i n water temperatures probably causes an i n c r e a s e i n metabolic r a t e s and a l s o apparently causes f i s h t o become more a c t i v e may  (Brown, 1957).  An i n c r e a s e i n water temperature  cause p l a n k t o n blooms (Hardy, 1956) thus i n c r e a s i n g the  a v a i l a b i l i t y of food organisms.  Also, as the f i s h s t a r t t o  move i n t o s h a l l o w e r water they w i l l come i n t o  increasingly  g r e a t e r c o n c e n t r a t i o n s of some of t h e i r most important food items, algae, b a r n a c l e s and mussels.  An i n c r e a s e i n meta-  b o l i c r a t e s , coupled w i t h the a v a i l a b i l i t y  of more food,  should cause an i n c r e a s e i n the growth r a t e .  T h i s expected  i n c r e a s e i n instantaneous d a i l y growth r a t e i n the s p r i n g and e a r l y summer months i s shown by F i g u r e  15.  In e a r l y June, w i t h warming of the s u r f a c e waters, Cymatogaster  s t a r t e d t o move i n t o the study area at Keates  I s l a n d from the south-west.  The f i r s t  f i s h t o appear were  y e a r l i n g s , f o l l o w e d by adult males and then by adult females. The r e l a t i v e numbers of both sexes of adult and y e a r l i n g Cymatogaster  remained at a f a i r l y constant l e v e l from mid-  June u n t i l j u s t p r i o r t o the spawning p e r i o d . the  During June  y e a r l i n g and adult f i s h e x h i b i t e d a p a t t e r n of d i u r n a l  82  movement, w h i c h i n v o l v e d m i g r a t i o n o f f i s h  from  over t h e  b e a c h and k e l p b e d s i n t o d e e p e r w a t e r w i t h t h e d e c r e a s e i n light to  intensity  a s s o c i a t e d with sunset,  and t h e n  the return  s h a l l o w water w i t h s u n r i s e . In  available  early  J u q e , when t h e f i r s t  f o r examination,  s p e c i m e n s became  t h e stomachs o f b o t h  y e a r l i n g C y m a t o g a s t e r were r a r e l y more t h a n all  fish  had b e e n e a t i n g t o some e x t e n t .  were f e e d i n g p r e d o m i n a n t l y fish  tended  feeding  Just was a g r e a t over  During adult  f u l l , but  The y e a r l i n g s  and a l g a e .  while  The f i s h  adult  started  a t s u n r i s e , t h e m a l e s c e a s i n g t o f e e d by e a r l y  noon w h i l e t h e f e m a l e s  fish  half  on s m a l l z o o p l a n k t o n  t o f e e d on m u s s e l s  a d u l t and  prior  continued u n t i l  t o spawning,  evening.  a t t h e end o f J u n e ,  i n c r e a s e i n t h e number o f b o t h  t h e b e a c h and i n t h e v i c i n i t y  t h e p e r i o d of a c t u a l spawning, fish  after-  there  a d u l t and y e a r l i n g  of the kelp  i n early  moved i n t o v e r y s h a l l o w w a t e r o v e r  beds.  July, the t h e beach  w h i l e t h e y e a r l i n g s moved b a c k i n t o d e e p e r w a t e r o f f t h e reef  faces.  deeper  s p a w n i n g t h e a d u l t s a l s o moved  movement  mid-July  a complete r e v e r s a l  p a t t e r n e x h i b i t e d by C y m a t o g a s t e r  T h e r e were r e l a t i v e l y  area during the daylight was an o n s h o r e movement ling  into  water. By  red.  After  fish.  few f i s h  hours,  of the d i u r n a l i n J u n e had o c c u r -  present  over  the study  but, with darkness,  there  o f l a r g e numbers o f a d u l t and y e a r -  83  The  feeding  in early July, while  activity the  of  adult  tion,  of  the  adult  f i s h was  inal cavity.  was  that  of the  intake  J u l y i s not  m a t u r e f e m a l e was  o f f o o d by  known a t  By  a g a i n and  the  for  both yearlings  initiated  em-  abdomrate  and  a t dawn and the  adult  assumed t h a t  f i s h had  a t an  adults,  and,  as  Why  there  Since the  c h e c k , and  formation  of  amount o f f o o d  to  year-  D u r i n g August of  darkness. majority  yearling fisb,  s i n c e the  July  i n the  was  It  of  was  fish  as w e l l  as  yearlings actively study area,  a s p a w n i n g c h e c k was  eaten.  The  i n July, feeding  ceased before t o t a l  t o some p h y s i o l o g i c a l s t r e s s a s s o c i a t e d t o the  reduction  s i m i l a r to that  e n t i r e time t h e y are  the  reduced.  begun a c t i v e l y  intensive rate.  month o f A u g u s t t h a t t h e  a d u l t s , formed the the  and  present.  formed a spawning check.  fed during  t o a much g r e a t e r  o f d i u r n a l movement was  also during  noticeably  t h e i r r a t e of growth i n c r e a s e d .  pattern  of  reproduc-  r i p e and  f e m a l e s t h a n by m a l e s .  e a r l y August the  the  not  with  rate  growth r a t e of y e a r l i n g s from June  l i n g s continued to feed  the  of the  a l a r g e volume of the  p r o b a b l y due  a decrease i n the  feeding  and  females,  average instantaneous monthly growth  phenomenon was  i n the  lowering  probably associated  f e m a l e t o o k up  The  increased  mature males remained r e l a t i v e l y c o n s t a n t i n June  July, while This  This  t e s t e s of t h e male were l a r g e  bryos w i t h i n the  of the  yearling fish  f i s h , p a r t i c u l a r l y the  almost e n t i r e l y stopped e a t i n g . feeding  the  it  was  related  with reproduction  and  84  Cymatogaster  continued t o feed  end o f September when f o o d of  hour  d i u r n a l sample  dicated that  deeper water.  the f i s h  September t h e g r e a t  check. the  There  remained  feeding  A l t h o u g h t h e r e was no 36  when t h e f i s h  the  coming  winter.  as g r e a t  a n n u l u s t o t h e one t h a t The average  and p r o b a b l y  as t h e a v e r a g e  will  be f o r m e d i n  following  a n n u l u s , t h a n d u r i n g t h e f o u r month  c h e c k and period  between t h e f o r m a t i o n o f an a n n u l u s and t h e f o l l o w i n g ing  check.  growth  during the eight  month p e r i o d between t h e f o r m a t i o n o f a s p a w n i n g the  i t was  annulus t o t h e  i n s t a n t a n e o u s monthly  r a t e was a l s o d e m o n s t r a t e d t o be much l e s s  spawning  move o u t o f  growth  t h e average d i s t a n c e from t h e l a s t  from t h a t  a  I n t h e s t u d y o f age and g r o w t h  l e a d i n g edge o f t h e s c a l e was a l m o s t distance  By t h e e n d  had f o r m e d  c o l d e r water,  datai n -  d u r i n g t h e day,  and A u g u s t .  majority of f i s h  deeper,  almost cease.  noted that  as J u l y  time  down and t h e f i s h  i n deeper water  are i n d i c a t i o n s that  study area i n t o  At t h i s  taken then, t h e seasonal n e t t i n g  f o l l o w i n g t h e same p a t t e r n of  i n t a k e was r e d u c e d .  y e a r t h e s u r f a c e w a t e r was c o o l i n g  s t a r t e d t o move i n t o  a c t i v e l y u n t i l the  spawn-  85  SUMMARY  1.  Regression  l i n e s p l o t t e d f o r the body length - s c a l e  r e l a t i o n s h i p show t h a t Cymatogaster e x h i b i t s a r e l a t i v e l y constant  r e l a t i o n s h i p between s c a l e growth and  increment  of body l e n g t h throughout i t s l i f e h i s t o r y . 2.  The  s c a l e of Cymatogaster may  have up  :  t o three  differ-  ent checks, b i r t h checks or metamorphic a n n u l i , spawning checks, and  annuli.  By observing  the time of  formation  of a check, by s t u d y i n g the p h y s i c a l f e a t u r e s of a check, and by t a k i n g the average d i s t a n c e from the focus of s c a l e t o a check and comparing i t with the tance,  the  average d i s -  the nature of a p a r t i c u l a r check can be  deter-  mined a c c u r a t e l y . 3.  By p l o t t i n g the r e g r e s s i o n l i n e s f o r body l e n g t h a n t e r i o r s c a l e r a d i u s , and measuring the d i s t a n c e  on from  the focus of a s c a l e t o a p a r t i c u l a r p o i n t on the s c a l e , the body l e n g t h of the f i s h at any p r e v i o u s l i f e h i s t o r y may 4.  back-calculated.  In the sample of Cymatogaster s t u d i e d , Lee's phenomenon i s not  5.  e a s i l y be  stage i n i t s  apparent.  V i r t u a l l y a l l y e a r l i n g Cymatogaster males were s e x u a l l y mature i n the s p r i n g of the year. examined contained  No  y e a r l i n g female  embryos but v i r t u a l l y a l l the 2 year  o l d females d i d . 6.  The  highest  l e v e l s of instantaneous  growth r a t e s  occur  86  between t h e f o r m a t i o n o f an a n n u l u s and t h e f o l l o w i n g spawning growth check 7.  check.  r a t e s o c c u r between t h e f o r m a t i o n o f a and t h e f o l l o w i n g  In t h e s p r i n g the f i r s t moving i n t o by a d u l t  8.  The l o w e s t l e v e l o f i n s t a n t a n e o u s  annulus. fish  t o appear  i n the study  s h a l l o w e r w a t e r were y e a r l i n g  males,  then adult  At t h e t i m e o f s p a w n i n g t h e number o f a d u l t  males,  t h e r e was a g r e a t  9.  After  spawning  the adult  followed  increase i n  o v e r t h e s t u d y a r e a and  at t h e same t i m e t h e y e a r l i n g s moved o u t i n t o d u r i n g t h e day.  area  females.  Cymatogaster  water  spawning  fish  deeper  r e t u r n e d t o deeper  water  d u r i n g t h e day. 10.  I n June, b e f o r e spawning, tern  o f d i u r n a l movement  deep t o s h a l l o w w a t e r t o deeper water  Cymatogaster that  exhibited  i n v o l v e d t h e movement  Light  intensity  i n g onshore  at n i g h t .  After  spawning  a p p e a r e d t o be v e r y  s e a s o n a l movement  important i n govern-  are present  effect  habits  on d i u r n a l movement o r  patterns.  Y e a r l i n g Cymatogaster  exhibited  pattern.  s u c h as t e m p e r a t u r e and f e e d i n g  seemed t o have l i t t l e  they  t h e r e was a  and o f f s h o r e movements o f C y m a t o g a s t e r .  Other f a c t o r s  12.  from  d u r i n g t h e day, and f r o m s h a l l o w  c o m p l e t e r e v e r s a l o f t h e d i u r n a l movement 11.  a pat-  actively  feed throughout the time  i n the study area.  Adult  a marked r e d u c t i o n o f f e e d i n g  Cymatogaster  activity  before,  87 during, 13.  By  and  after  spawning.  volume, m u s s e l s  items i n the  and  d i e t of  a l g a e were t h e  most  C y m a t o g a s t e r , but  barnacles  z o o p l a n k t o n were sometimes e a t e n i n l a r g e The  feeding  habits  and  food  important and  quantities.  p r e f e r e n c e s of  adults  and  y e a r l i n g s were v e r y s i m i l a r . 14.  The  rate  tract  of  passage of  food  v a r i e d between a d u l t s  and  the  The  digestive rates  imately  rate  the  through the and  yearling  a l s o v a r i e d w i t h the  same and  of  adults  digestive  and  t h e y d i d not  Cymatogaster,  season of  the  y e a r l i n g s were vary  year. approx-  seasonally.  88 LITERATURE CITED Brown, M. E. 1957. The P h y s i o l o g y of F i s h e s . Volume I Metabolism. Academic Press, New York: 447 pp. Bryan, P. and H. H. Howell. 1946. Depth d i s t r i b u t i o n of f i s h i n Lower Wheeler R e s e r v o i r , Alabama. J . Tenn. Acad. S c i . , 21: 4 - 9 . 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