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UBC Theses and Dissertations

A new method of determining the efficiency of towed plankton samplers Gilfillan, Edward Smith 1967

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A NEW METHOD OF DETERMINING THE EFFICIENCY OF TOWED PLANKTON SAMPLERS  by EDWARD SMITH G I L F I L L A N I I I  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE' OF MASTER OF SCIENCE  i n t h e Department o f ZOOLOGY and INSTITUTE OF OCEANOGRAPHY  We a c c e p t t h i s required  thesis  as c o n f o r m i n g  to the  standard  THE UNIVERSITY OF B R I T I S H COLUMBIA May, 1967  In  presenting  for that  this  an a d v a n c e d the  study. thesis  thesis  degree  Library  at  in p a r t i a l the  s h a l l make  I further  University  it  agree that  fulfilment of  freely  of  available  scholarly  p u r p o s e s may be g r a n t e d  Department  o r by h i s  representatives.  w i t h o u t my w r i t t e n  this  thesis  for  permission.  Department 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, C a n a d a  for  Columbia  It  requirements  Columbia,  I  reference  and  permission for extensive  for  or p u b l i c a t i o n of  British  the  copying of  this  by t h e Head o f my  is understood that  financial  agree  gain  shall  n o t be  copying allowed  i  ABSTRACT  In  recent  years  accuracy  with  which  describe  the size  interest  collections  are that  of sampling  especially  model  when  i s proposed  zooplanktonic  organisms  of  the radius  o f t h e mouth  it  i s towed,  order detect field  against the  model  biological in  to describe  arising may  the processes a sampler  of the sampler,  from be  the organisms  by  which  i n terms  the speed  at  which  can a t t a i n  a t which" t h e o r g a n i s m s  of percentage  escapement.  samplers  are required.  or avoid  speed  the  zooplanktonic  zooplankton  a curve  a good  recommendations  of  i s capable  of towing.  gives  plankton  The m o d e l  to provide  speed  by  concerning  errors  p r e c i s e data  and t h e d i s t a n c e  the sampler. data  devices  escape  the e f f e c t i v e  to escape,  with  indications  the  A  made  composition  The  important,  increased  and s p e c i e s  communities. avoidance  has  The r e s u l t s  of being catch  presented  can  fitted  to  plotted  indicate  representation of the processes Implications of the results  r e s p e c t i n g the design  in  of plankton  that  of  are  embodied  samplers.  i i  TABLE OF CONTENTS Page 1  Introduction Concepts  and S u r v e y o f L i t e r a t u r e  5  The Model  19  M a t e r i a l s and Methods  25  Field  Procedure  The P l a n k t o n Laboratory  26  Samplers  29  Methods  Mathematical  32  Procedure  Results  37 .  38  Discussion  .59  One-metre C o n i c a l S a m p l e r  69  70-cm N.I.O. S a m p l e r  69  Catcher  . . . . .  Experimental One S q u a r e Plankton Use  Samplers  M e t r e P.O.G. S a m p l e r s  Sampler  and U t i l i t y  General  Design o f t h e Model  Conclusions  .71 . .72  . . . . . . .  .74  . . . . < , . . . .  .75 77 79  REFERENCES  80  APPENDIX I  84  iii  L I S T OF TABLES  Table  Subject  Page  1.  Flow Meter Counts ( p e r h a u l )  10  2.  R e s u l t s o f F i e l d T r i a l s : A u g u s t , 1965 One-metre C o n i c a l S a m p l e r . . . . .  53  R e s u l t s o f F i e l d T r i a l s : J a n u a r y , 1966 M o d i f i e d One-metre C o n i c a l S a m p l e r . . . . . . .  54-  Results of F i e l d T r i a l s : 70-cm N.I'.O. S a m p l e r  55  3. 4. 5. 6. 7. 8. 9.  A u g u s t , 1965  R e s u l t s o f F i e l d T r i a l s : J a n u a r y , 1966 M o d i f i e d 70-cm.N.1.0. S a m p l e r Results of F i e l d Catcher P.O.G. U n p u b l i s h e d A u g u s t , .1965-  Trials:  .  56  A u g u s t , 1965 57  Results  Obtained i n 58  Comparison of P o p u l a t i o n Estimates i n Numbe'rs/m3 o f Water F i l t e r e d  63  R e s u l t s o f F i f t e e n S u c c e s s i v e Counts o f t h e Number o f E u p h a u s i i d s L y i n g w i t h i n l / 2 0 t h of t h e Area of t h e Bottom o f a D i s h C o n t a i n i n g 1343 E u p h a u s i i d s  86  iv LIST OF FIGURES Figure  Subject  Page  1.  The k i n e m a t i c b a s i s o f B a r k e l e y ' s ( 1 9 6 4 ) m o d e l f o r a s s e s s i n g t h e e f f i c i e n c y o f towed plankton samplers f a c i n g p. 5  2.  Mean f l o w m e t e r  counts p l o t t e d against  speed o f h a u l i n g • 3. 4.  The k i n e m a t i c The l o c a t i o n 1965  .  9  b a s i s o f t h e model of the f i e l d  trials  22 of August,  and J a n u a r y , 1966  27  5a. The o n e - m e t r e  c o n i c a l sampler  33  5b. The o n e - m e t r e  c o n i c a l sampler m o d i f i e d  by  the attachment of a weight t o i t s b r i d l e s  . . . .  6a. The 70-cm N.I.O. s a m p l e r 6b. The 70-cm N.I.O. s a m p l e r m o d i f i e d  34 by t h e  removal of the canvas c o l l a r 7a. The C a t c h e r 7b. The f i l t e r  lib.  34 35  used  i n t h e Catcher  8a. P e r c e n t a g e c a t c h p l o t t e d a g a i n s t s p e e d o f h a u l i n g f o r t h e one-metre c o n i c a l sampler 8b. G o o d n e s s - o f - f i t d i a g r a m f o r t h e r e s u l t s o b t a i n e d w i t h t h e one-metre c o n i c a l sampler 9a. P e r c e n t a g e c a t c h p l o t t e d a g a i n s t s p e e d o f h a u l i n g f o r t h e m o d i f i e d one-metre c o n i c a l sampler ... 9b. G o o d n e s s - o f - f i t d i a g r a m f o r t h e r e s u l t s o b t a i n e d w i t h t h e m o d i f i e d one-metre c o n i c a l sampler . . . 10. P e r c e n t a g e c a t c h p l o t t e d a g a i n s t speed o f h a u l i n g f o r t h e 70-cm N.I.O. s a m p l e r 11a.  33  35 42 43 44 45 46  P e r c e n t a g e c a t c h p l o t t e d a g a i n s t speed of h a u l i n g f o r t h e m o d i f i e d 70-cm N.I.O. s a m p l e r . . . . . .  47  G o o d n e s s - o f - f i t diagram f o r the r e s u l t s obtained w i t h t h e m o d i f i e d 70-cm N.I.O. s a m p l e r  48  V  LIST OF FIGURES Figure 12a. 12b. 13a. 13b.  (continued)  Subject Percentage catch p l o t t e d for the Catcher  against  Page speed o f h a u l i n g 49  G o o d n e s s - o f - f i t diagram f o r the r e s u l t s with the Catcher . Percentage catch p l o t t e d against f o r t h e P.O.G. s a m p l e r s  obtained 50  speed o f h a u l i n g  Goodne.ss-of-fit diagram f o r the r e s u l t s obtained w i t h t h e P.O.G. s a m p l e r s . . . . . . .  51 52  Vi  ACKNOWLEDGMENTS I am  indebted  committee f o r t h e i r to extend Dr.  B.  my  Mck.  t o a l l o f t h e members o f my g u i d a n c e and  encouragement.  most s i n c e r e t h a n k s t o my  research I would  like  research'advisor,  B a r y f o r h i s p a t i e n c e , e n c o u r a g e m e n t and  criti-  cism. I would a l s o l i k e  t o t h a n k Dr.  Dr.  I . E.  E f f o r d , ' D r . P.  Dr.  G.-L.  P i c k a r d , a l l of'whom r e a d  script,  H.  for their helpful R.  J . LeBrasseur  Leblond,  C.,  d a t a , f o r w h i c h many t h a n k s a r e  due.  C.N.A.V. W h i t e t h r o a t c h e e r f u l and  to thank the and  Dehene1,  Dr.  P.  A.  Larkin,  criticized  and  the  of the  provided  manu-  Pacific  unpublished  o f f i c e r s , a n d men-  of  C.N.A.V. S t . A n t h o n y f o r  generous a s s i s t a n c e i n the  and  criticism.  McAllister  O c e a n o g r a p h i c G r o u p , N a n a i m o , B.  I would l i k e  A.  and  suggestions  and-C. D.  P.  gathering  their of  the  data . To  my  the r e s e a r c h easier,  w i f e , K a t h e r i n e , whose e n c o u r a g e m e n t and  p r e p a r a t i o n of the  I o f f e r "my most s i n c e r e No  expression  Heilman, without  during  thesis'made the  t a s k much  thanks.  o f t h a n k s can  suffice•for  Mrs.  E.  A.  whom none o f t h i s w o u l d have been p o s s i b l e .  INTRODUCTION: The  goal of the p l a n k t o l o g i s t  structural  and f u n c t i o n a l a s p e c t s  B e c a u s e he i s u n a b l e largely for  t o observe  i s to understand the  o f t h e p l a n k t o n i c community.  this  community d i r e c t l y  committed t o g a t h e r i n g h i s data'at  information regarding the size  of d e v i c e s .  Although  a d i s t a n c e , and  and s p e c i e s c o m p o s i t i o n o f  t h e p l a n k t o n i c c o m m u n i t y , has t o r e l y a variety  on s a m p l e s c o l l e c t e d by  pumps, t r a p s , and even  s e i n e s have been and a r e b e i n g u s e d t o o b t a i n such almost present  a l l are c o l l e c t e d study  r a n g i n g from length  designed  a b o u t one m i l l i m e t r e  samples,  to' catch  In the  zooplankton  to several centimetres i n  are discussed. e x c e p t i o n p l a n k t o n samplers  p a s s i n g a l a r g e volume o f w a t e r This s u r f a c e , which expected  i s usually  of sampler  supported  through  i n the form  the f i l t e r i n g  by a r i n g  (Wiborg,  o p e r a t e by  a filtering  surface.  of a c o n i c a l n e t ,  t o r e t a i n much o f t h e p a r t i c u l a t e  l a r g e r t h a n t h e mesh a p e r t u r e type  purse  w i t h towed p l a n k t o n s a m p l e r s .  s e v e r a l samplers  Almost without  is  he i s  matter  1948).  which i s  In t h e s i m p l e s t  s u r f a c e i s a t r u n c a t e d cone  a t t h e mouth and t e r m i n a t i n g i n a c o l l e c t i n g  bucket  t o w a r d s t h e apex o f t h e c o n e .  nearly  a l l p l a n k t o n s a m p l e r s , b u t has a number o f d i s a d v a n t a g e s .  Chief of these  i s the lack  uncontaminated  samples from  o f any p r o v i s i o n a particular  c o l u m n , and a g e n e r a l c l u m s i n e s s sampler  at a time.  This design  i s basic to  forobtaining  stratum  of the water  when u s i n g more t h a n one  However, t h e b a s i c p r i n c i p l e s  of i t s  o p e r a t i o n a r e common t o a l l towed p l a n k t o n  samplers.  Two s o r t s o f i n f o r m a t i o n s h o u l d be o b t a i n e d when u s i n g a plankton  sampler.  These'are, f i r s t l y , ' a  r e p r e s e n t a t i v e sample  o f t h e community o r p o p u l a t i o n o f a s p e c i e s o r g r o u p o f s p e c i e s of zooplankton  present;  and, s e c o n d l y ,  information leading to  a d e t e r m i n a t i o n o f t h e volume o f w a t e r f i l t e r e d . s a m p l e r may f a i l t o p r o v i d e reasons the be  either  and, i f the inadequacy  interpretation  internally  f o r a v a r i e t y of  i s not r e c o g n i s e d , e r r o r s i n  o f t h e d a t a may r e s u l t .  d i v i d e d i n t o two b r o a d Firstly,  of these  A plankton  These e r r o r s c a n  categories.  there are those  to the sampler,  sources  including  of e r r o r  those  originating  arising  from  i n a c c u r a t e d e t e r m i n a t i o n o f t h e volume o f w a t e r w h i c h has passed  through  the f i l t e r .  These e r r o r s c a n be l a r g e l y  come by t h e u s e o f a f l o w m e t e r w h i c h h a s ' b e e n calibrated.  Losses  mals t h r o u g h  t h e meshes o f t h e f i l t e r  selecting  a filter  of catch r e s u l t i n g  which w i l l  retain  over-  carefully  from e x t r u s i o n of a n i c a n be m i n i m i s e d  by  a l l specimens of the  s p e c i e s t o be s t u d i e d . In  t h e second c a t e g o r y  externally  to the sampler,  estimation of the s i z e  are sources  including  of e r r o r  originating  t h o s e ' a r i s i n g i nthe  of a zooplankton  p o p u l a t i o n because  o f t h e non-homogeneous d i s t r i b u t i o n  of i t s c o n s t i t u e n t s  (Barnes,  1951; C a s s i e , 1958,  1959).  1949; Barnes a n d ' M a r s h a l l ,  A t t e m p t s t o c o m p e n s a t e f o r t h e non-homogeneous  distribution the design  of zooplankton  of the sampling  c a n be made,' i f n e c e s s a r y , i n program.  This category  also  3 includes errors  i n the e s t i m a t e s of the s i z e  p o p u l a t i o n s w h i c h may of  arise  not e a s i l y  data which  species  d e t e c t e d , and  i n the f i e l d  Hansen and A n d e r s o n  B r a s s e u r and  errors  non-quantitative requiring  arise  b y Sheard  exact  each  ( 1 9 4 1 ) , Aron  ( 1962 ) , Regan ( 1963 ),  McAllister-(1966)  from the r e a c t i o n s  and  Le  indicate-not- only that  prob-  of z o o p l a n k t o n i c organisms  presence of t h e - s a m p l e r , but a l s o t h a t - t h e problems  compounded b e c a u s e  the- e f f e c t s  to are  o f the- r e a c t i o n s v a r y a c c o r d i n g  t h e v a r y i n g powers' o f ' p e r c e p t i o n a n d \ l o c o m o t i o n p o s s e s s e d  by each s p e c i e s .  In t h i s ' c o n n e c t i o n  ( 1 9 6 5 ) have p o s t u l a t e d periphery of  These  i n a community'.  ( 1962 ),  to  they lead to  avoidance  c o n c e r n i n g t h e ' s i z e of the p o p u l a t i o n of  Data from s t u d i e s  lems  animals.  can'be t r o u b l e s o m e t o any p r o g r a m  information  the  f r o m t h e d e t e c t i o n and  t h e s a m p l i n g ' d e v i e e by i n d i v i d u a l  are  of z o o p l a n k t o n i c  Flemminger  t h e e x i s t e n c e o f a zone  and  around  o f t h e mouth o f t h e s a m p l e r f r o m w h i c h - t h e  z o o p l a n k t o n t h e y s t u d i e d were a b l e to- e s c a p e .  ( 1 9 6 4 ) has  Clutter the species  Barkeley  analysed t h e - k i n e m a t i c s of t h e ' r e a c t i o n  of  i n d i v i d u a l a n i m a l s • t o " t h e p r e s e n c e o f the-.sampler . In Barkeley s 1  the  the p r e s e n t study a m a t h e m a t i c a l model, analysis  of the r e a c t i o n of i n d i v i d u a l  based  on  animals to  p r e s e n c e of a p l a n k t o n - s a m p l e r , i s p r o p o s e d . T h i s model  treats speed  the p e r i p h e r a l  zone  of escape  as a f u n c t i o n  of h a u l i n g a n d " c a n - b e - f i t t e d to f i e l d  C o u r t e s y R. Le B r a s s e u r , P a c i f i c N a n a i m o , B r i t i s h C o l u m b i a , Canada.  of the  data to provide a  Oceanographic  Group,  4  plot  of percentage c a t c h  of t h i s features  study  indicate  against  speed of h a u l i n g .  The  t h a t the model a c c o u n t s f o r the -  of l o s s  i n catch  resulting  avoidance of the  plankton  s a m p l e r by  from'the d e t e c t i o n individual  results major and  organisms.  r  Figure 1. The kinematic basis of B a r k e l e y ' s model for assessing the efficiency of a towed plankton sampler. U= the speed of towing, R= the radius of the sampler, X = the distance at which organisms can detect the sampler, r = the i n i t i a l offset of the organism, u= the m i n i m a l escape velocity of the o rg a n i s m, p= the o r i g i n a l position of the o r g a n i s m, e= the angle at which the organism swims with respect to the axis of the sampler. Q  Q  5  CONCEPTS AND SURVEY OF LITERATURE: For t h e purpose o f t h i s is  d e f i n e d as t h e a v o i d a n c e  by  zooplankton  o f an a p p r o a c h i n g  by means o f t h e i r  sequence o f b i o l o g i c a l size  study b i o l o g i c a l  possessed  the p r o p o r t i o n s of animals  Barkeley's  of b i o l o g i c a l  species of  c a u g h t may n o t be t h e  s p e c i e s i n t h e community. of a sampler,  i s d e f i n e d as t h e d i f f e r e n t i a l  more s p e c i e s o r s i z e r a n g e s  biological  Another' e f f e c t  by d i f f e r e n t  This c o n t r i b u t e s to the s e l e c t i v i t y  If  The c o n -  o f t h e v a r y i n g powers o f p e r -  same as t h e p r o p o r t i o n s o f t h o s e  selectivity  where  c a p t u r e o f one o r  of zooplankton.  (1964) a n a l y s i s  of the kinematics of  e s c a p e m e n t i s c o r r e c t ( F i g . 1) i t i s t o be  t h a t t h e number o f s p e c i m e n s o f a s p e c i e s c a p t u r e d volume o f w a t e r increased.  will  o p p o r t u n i t y t o evade t h e  will  have l e s s  time  greatest capture  i n which  sampler  t o move b e f o r e  because  the sampler  T h i s i n c r e a s e i n c a t c h c a n be e x p e c t e d  f o r those  animals  at the o r i g i n a l  f a c t o r s may a f f e c t present;^ mostly collecting  per unit  As t h e s p e e d o f h a u l i n g i s i n c r e a s e d t h e z o o p l a n k t o n  have l e s s  them.  expected  i n c r e a s e i f t h e speed o f h a u l i n g i s  will  takes  sampler  escapement i s u n d e r e s t i m a t i o n o f t h e  e s c a p e m e n t i s t h a t , as a r e s u l t  zooplankton,  plankton  own e x e r t i o n s .  of zooplanktonic populations.  c e p t i o n and m o b i l i t y  escapement  which  are best  speed of h a u l i n g .  technique.  originate  over-  t o be  able t o escape However, o t h e r  t h e e s t i m a t e s o f t h e numbers o f e a c h  these  they  i n errors arising  species  i n the  6 The is  t o p a s s a l a r g e volume o f w a t e r t h r o u g h t h e f i l t e r i n g  face the  u s u a l method o f o p e r a t i o n o f a p l a n k t o n s a m p l e r  (net).  One  source of e r r o r  i s i n the d e t e r m i n a t i o n of  volume o f w a t e r w h i c h has been f i l t e r e d .  T h i s volume  be d e t e r m i n e d e i t h e r w i t h a f l o w m e t e r w h i c h ' h a s in the to  the sampler  i n which  filtered  been  o f t h e tow.  i s t o be d e t e r m i n e d by a s s u m p t i o n  of the water p r e s e n t e d  and,  i t is essential  i n most  However, t h e d i s t a n c e t h a t t h e s a m p l e r has  accounted f o r . relative  Even i n a v e r t i c a l  In  of c u r r e n t s  haul,  is  fil-  moved  i s not always easy t o ' d e t e r m i n e .  z o n t a l o r o b l i q u e h a u l s unknown e f f e c t s  to  instances,  what p r o p o r t i o n o f t h e w a t e r p r e s e n t e d t o t h e s a m p l e r  through the water  that  I f t h e volume o f w a t e r  know what t h e l e n g t h o f t h e tow was  tered.  can  calibrated  i t i s t o be u s e d , o r by a s s u m i n g  s a m p l e r f i l t e r s some c o n s t a n t f r a c t i o n i t over the l e n g t h  sur-  hori-  s h o u l d be  s h o u l d t h e s h i p move  t o t h e w i r e , t h e d i s t a n c e t h a t t h e s a m p l e r moves  through the water  i s d i f f i c u l t to determine.  Another cause  of e r r o r s , i n the d e t e r m i n a t i o n of the  volume o f w a t e r w h i c h has p a s s e d t h r o u g h t h e s a m p l e r , i s c l o g g i n g o f t h e meshes o f t h e f i l t e r , When s a m p l i n g i s c a r r i e d be a s e r i o u s p r o b l e m . filtered  per u n i t  severity  of c l o g g i n g  o f t e n by p h y t o p l a n k t o n .  out i n p r o d u c t i v e w a t e r s c l o g g i n g  When c l o g g i n g  d i s t a n c e may  occurs the amount of water  open a r e a o f t h e f i l t e r  of  t h e s a m p l e r , e.g. by g r e a t l y  s a m p l e r , o r by i n c r e a s i n g  -  be g r e a t l y  can be r e d u c e d by  of  in relation  reduced.  increasing  The t h e amount  t o t h e a r e a o f t h e mouth  increasing  the s i z e  can  the l e n g t h of the  o f t h e meshes o f t h e  7 filter.  (Smith, pers . Because  comm.).  i t i s i m p o r t a n t t o d e t e r m i n e t h e volume o f w a t e r  w h i c h has been f i l t e r e d • m a n y p l a n k t o n s a m p l e r s employ meters.  A f l o w meter  consists  flow  o f an i m p e l l e r , g e a r e d t o a  c o u n t e r , w h i c h r e c o r d s t h e number o f r e v o l u t i o n s made by t h e impeller. because  The use o f a f l o w meter  i n t r o d u c e s many  i t a c t u a l l y m e a s u r e s t h e l e n g t h o f a column  w h i c h has p a s s e d t h r o u g h t h e s a m p l e r ; n o t v o l u m e . it  i s necessary to c a l i b r a t e  of  revolutions  t h e f l o w meter  can be c o n v e r t e d t o volume  The c a l i b r a t i o n  of water Therefore,  b e f o r e t h e number filtered.  i s made by t o w i n g t h e s a m p l e r o v e r a  known d i s t a n c e b o t h w i t h ' a n d w i t h o u t t h e • f i l t e r The r e s u l t s  problems  f r o m tows made w i t h o u t t h e f i l t e r :  i n place.  give the c a l i -  b r a t i o n w i t h r e s p e c t t o d i s t a n c e moved t h r o u g h t h e w a t e r . Comparison  of the r e s u l t s  g i v e n w i t h and w i t h o u t t h e f i l t e r  g i v e s an e s t i m a t e o f t h e p e r c e n t a g e o f t h e w a t e r p r e s e n t e d to  t h e s a m p l e r w h i c h ' i s ' a c c e p t e d by i t .  What' i s a c t u a l l y  m e a s u r e d by t h e d i f f e r e n c e ' b e t w e e n t h e ' r e a d i n g s o b t a i n e d w i t h and w i t h o u t t h e f i l t e r  i s the reduction  in"the velocity  of flow  t h r o u g h t h e s a m p l e r • c a u s e d by t h e p r e s e n c e o f t h e f i l t e r , o r the at the  length  of the water•column  which'passed•through  the p o s i t i o n of the flow meter. Clarke-Bumpus  the sampler  In s m a l l samplers  like  S a m p l e r ' ( C l a r k e and Bumpus, 1950) i n w h i c h t h e  i m p e l l e r o c c u p i e s most o f t h e d i a m e t e r o f t h e s a m p l e r , a good e s t i m a t e o f t h e amount o f w a t e r w h i c h h a s " p a s s e d  through the  Dr. P. S m i t h , U. S. B u r e a u La J o l l a , C a l i f .  Fisheries,  of Commercial  8 s a m p l e r may  be  obtained.  N.I.O. 70-cm s a m p l e r metre c o n i c a l  In l a r g e r  ( C u r r i e and  sampler the  made t h a t t h e  same as  s a m p l e r and  f l o w through the  i t i s at the  position  t h e mouth o f t h e  sampler.  shown t h a t t h e w i r e , and 5a)  create  1957)  the  sampler  flow-meter.  the  r e s u l t s , the  meters to give Errors  comm.).  of l a m i n a r  wake may  flow  i n estimates  of the  been f i l t e r e d  trials  undertaken i n the  against  trials  wake p a s s i n g not  of the  sampler,  centre  of  the  Because the i n order  to  flow  give flow-  estimates  of  could obscure  unit  the the  of b i o l o g i c a l escapement. In F i g . 2 flow-meter r e a d i n g s  field  shackle  number o f o r g a n i s m s p e r  volume o f w a t e r w h i c h has  plotted  of  inaccurate results .  from i n a c c u r a t e  field  centre  c a u s e c e n t r a l l y mounted  volume o f w a t e r r e s u l t i n g  effects  the  s t u d i e s have  terminal  to the b r i d l e s  (Bary, pers.  small  Further,  been mounted i n t h e  especially  m e t e r must be, i n a r e g i o n accurate  only a  one-  a s s u m p t i o n must  a t u r b u l e n t wake w h i c h p a s s e s i n t o t h e  mouth o f t h e  or the  Recent e x p e r i m e n t a l  which i s attached  the  sampler' i s everywhere  of the  f l o w - m e t e r s have t r a d i t i o n a l l y  (Fig.  Foxton,  f l o w meter o c c u p i e s  p o r t i o n o f t h e mouth o f t h e be  s a m p l e r s s u c h as  the  speed of h a u l i n g  were c a r r i e d into  appreciated,  the and  course  out  centre  the  recorded  during  of t h i s study (see  effect  Table 1). of the  of the mouth-of the  the are When t h e  turbulent sampler  t h e r e f o r e a l l d a t a were o b t a i n e d  Dr. B.. Mck. B a r y , I n s t i t u t e o f O c e a n o g r a p h y , U n i v e r s i t y o f B. C. , V a n c o u v e r , Canada .  was  with  Figure  2 ( f a c i n g ) Mean f l o w m e t e r c o u n t s p l o t t e d a g a i n s t speed o f hauling. The r e s u l t s f o r t h e 1-m c o n i c a l s a m p l e r , t h e 70-cm N.I.O. s a m p l e r , and t h e C a t c h e r were o b t a i n e d d u r i n g t h e f i e l d t r i a l s of August, 1965; t h o s e f o r t h e two e x p e r i m e n t a l s a m p l e r s were o b t a i n e d d u r i n g t h e f i e l d t r i a l s o f J a n u a r y , 1966.  X  0  l-m  CONICAL SAMPLER  70-cm N.I.O. SAMPLER  8  A  CATCHER  +  MODIFIED  l-m CONICAL SAMPLER  O  MODIFIED  70-cm N.I.O. SAMPLER  j  i  i  i  20  40  60  80 SPEED  I 100  l  120  I  140  OF HAULING  I  160 cm/sec  1  180  1 200  1—  220  10 T a b l e 1.  Flow Meter Counts  (per haul)  August,1965 Speeds 25 cm/sec 100 cm/sec One-metre c o n i c a l , s a m p l e r  '  18 .0 17.0 18,0 18.0 17,5 18,0 18,5 17,0  - ' 16,5 14,5 17.0 18.5 17,5 17,5 .17,0 16.5  200 cm/sec 16.5 16.5 15,0 16.0 17,0 16.0 17,0 1.6 ,5  70-cm N.I.O. s a m p l e r 6. 9. 9. 9, 8. 9. 7. 8. Catcher  5 5 5 0 0 5 5 5  7. 5 8„5 .7 , 5 8.0 8,5 7 ..5 9,0 8.0  7 .0 7„0 765 6.5 7.5 8,0 6.0 7„0  9,5 8„5 9.0 8 o 5, 9.0 9.0 9„0 8, 0  9.0 10 . 0 9,5 9,5 7.0 9,0 10 , 0 9 ,0  (50 cm/sec) 6.0 8.0 8.0 9o0 8o0 8,5 7„0 8.0 January- 1966  M o d i f i e d one-metre c o n i c a l  sampler 19,0 14„0 23 . 5  Modified  24,0 26.5 25 . 0  17,0 30,0 1:5 . 0  70-cm N.I.O, s a m p l e r 15.0 15.5 15.0  ' 14.0 14,0 14.0  14,5 14.5 14.0  11 centrally  mounted f l o w m e t e r s .  The (Fig.  7a)  impeller  piece.  The  t h e N.I.O. 70-cm s a m p l e r  conical  s a m p l e r was  1957).  Only  large  about  impeller  d e v i a t i o n was  sampler cal  15 cm  deviations  80 cm  i s most p r o b a b l e t h a t  not o n l y  this  used  i n the  i n the t u r b u l e n t  and  m o d i f i e d by a d d i n g a  cylindri-  o f t h e mouth o f t h e s a m p l e r .  d e v i a t i o n was the flow  It  c a u s e d by t h e wake  meter. large  s a m p l e r s were  z o n e , b u t a l s o were u n a b l e t o m o n i t o r of the flow through the sampler, the that  per h a u l p r o b a b l y  not o c c u r . t h e p r e s e n t s t u d y t h e volume o f w a t e r f i l t e r e d  calculated  by a s s u m i n g  that  the samplers f i l t e r e d  100%  w a t e r p r e s e n t e d t o them o v e r t h e c o u r s e o f t h e tow. is believed  n o t t o have o c c u r r e d .  s a m p l e r s were h a u l e d v e r t i c a l l y protected  location  special  was  of the  Clogging  In t h e f i e l d t r i a l s  the  o v e r a known d i s t a n c e .  In  i n w h i c h t h e y were c a r r i e d  n e v e r s t r a y e d more t h a n a few the  by  conical  f r o m them have been u s e d o n l y as an a s s u r a n c e  In  the  Foxton,  In the p r e s e n t study a  l a r g e c h a n g e s i n t h e volume o f w a t e r f i l t e r e d did  one-metre  i n diameter (Currie  t h e f l o w - m e t e r s i n t h e two  more t h a n a s m a l l p o r t i o n results  of the flowmeter  i n f l o w s u c h as t h o s e c a u s e d  in front  from the weight a f f e c t i n g Because  dia-  o b t a i n e d u s i n g t h e one m e t r e  ( F i g . 5b) when i t was  lead weight  the whole  ( F i g . 6a) and  c l o g g i n g , c a n be d e t e c t e d r e a d i l y . large  i n the C a t c h e r  ( B a r y et_ a_l_. , 1958 ) o c c u p i e s n e a r l y  meter of the t a i l in  o f t h e f l o w m e t e r used  degrees  c i r c u m s t a n c e s of t h i s  out t h e w i r e  from the v e r t i c a l .  s t u d y t h e method o f  In  assuming  12 a volume f i l t e r e d  a p p e a r s t o be  probable  s a m p l e r s d i d not  t h a t the  presented being  t o them, but  evaluated  t h e w a t e r be  al.  filtered.  ( 1 9 5 8 ) and  Heron (196 5) and  i s not  100%  important  That a c o n s t a n t  of the  G i l f i l l a n and  Catcher  can  arise  quantitatively. filter  This  situation  decreasing  -  the  which the  necessary  species which are size  filter  can  be  w i l l not  avoided  t o be  w i l l clog.  when s a m p l i n g  studied.  A f u r t h e r source  of v a r i a t i o n  sea  These p a t c h e s may (Cushing,  1954)  (Barnes, be  and  may  a l s o be  o n l y a few  the  effects  a  individuals  rate  non-  M a r s h a l l , 1951).  the  19 58 , 19 59 ).  metres i n t h i c k n e s s  of the patchy  choosing  from the  of s e v e r a l  These  (Bary,  s u b s t r u c t u r e and  extent  order  Hauls s e v e r a l hundred metres long w i l l tend out  sampled  However,  in lateral  have a s u b s t r u c t u r e on ('Cassie,.  be  ' p a t c h i n e s s ' , of a  194-9; B a r n e s and  several kilometers  metres i n a l l dimensions  filtered,  a compromise i s o f t e n  results  -  i n the  been  waters.  homogeneous d i s p e r s i o n o f i n d i v i d u a l s , o r species  and  present  i n c r e a s e s the  Therefore  in productive  by  to r e t a i n  o f t h e mesh a p e r t u r e  filter  Bary  o r g a n i s m s s m a l l enough  w i t h a s m a l l enough mesh a p e r t u r e  of a l l those  at  Firstly,  t h e meshes o f t h e  over  Pease ( i n p r e p . ) .  u n i t v o l u m e , when a known volume o f w a t e r has  pass through  by  of  Tranter  o f t h e number o f s p e c i m e n s  sources.  model  volume i s f i l t e r e d  per  to  water  proportion  C l a r k e - B u m p u s S a m p l e r by  i n estimates  f r o m two  It is  because the  been d e m o n s t r a t e d f o r t h e  f o r the  by  !  Errors  filter  r e q u i r e s o n l y t h a t some c o n s t a n t  a r a n g e o f s p e e d s has et  this  t h e most u s e f u l one.  patches  1966). to  provide  average a  13 better yield  sample of the p o p u l a t i o n p r e s e n t .  V e r t i c a l hauls  t h e most r e l i a b l e sample when t h e a g g r e g a t i o n s  plankton  are p r i m a r i l y  in horizontal  p r e c a u t i o n w h i c h s h o u l d be effects  of p a t c h i n e s s  r a t h e r than Few  r e l i a b l e data i n the  investigations  sources  of e r r o r  difficult 1939).  literature.  the  of water  position.  b i o l o g i c a l escapement  I n many o f t h e with  m e a s u r e s were t a k e n obscure  zoo-  further  to reduce  same g e o g r a p h i c a l  concerning  w h i c h can  A  t h e same p a r c e l  of the problems connected  inadequate  escapement'.  to attempt  is- to f o l l o w  t o sample at the  are a v a i l a b l e  sampling,  taken  layers.  of  will  the  reported  plankton  to reduce those  effects  other  of b i o l o g i c a l  A c c o r d i n g l y i n t e r p r e t a t i o n - of the r e s u l t s i s  at best  ( e . g . H e n s e n , 1895;  A b r i e f review  K u n n e , 1933;  Gibbons,  of the p e r t i n e n t l i t e r a t u r e i s g i v e n  b elow. W i n s o r and  Clarke  t h e s i z e o f c o p e p o d and conical such the  sampler having  as t h i s one form:  g i v e n by (i.e.  are  (1940) concluded chaetognath  12.5-cm c o n i c a l a conical  q u e s t i o n because the  referrred  sampler). field  the a r e a  errors  may  cm  to i n the t e x t  Such e s t i m a t e s  trials  not  ( G e o r g e s B a n k ) i s one  have been i n t r o d u c e d by  a  ( a l l samplers  s a m p l e r ) were c o m p a r a b l e t o  a g e o g r a p h i c a l l o c a t i o n r a t h e r than but  o f 12.5  s a m p l e r w i t h a mouth o p e n i n g  a 75-cm c o n i c a l  of  p o p u l a t i o n s g i v e n by  a mouth o p e n i n g  subsequently  that estimates  o f 75  those cm  a r e open t o  o n l y were c a r r i e d  in a single  in  parcel  out of  at water,  o f s t r o n g c i r c u l a t i o n . Thus patchiness.  14 Sheard H a r d y , 1929)  ( 1 9 4 1 ) towed a 70-cm D i s c o v e r y at speeds r a n g i n g  1 t o 3 m/sec. of the  catch  As  the  attributed tion  the  of the  from 2 to 6 knots  (Kemp  At  6 kt f i s h  F i s h " w e r e not  increase- i n catch  samples c o l l e c t e d  to decreased b i o l o g i c a l  up- t o 7,5  caught at 2 k t .  and  the  cm  Sheard  speeds of  compositowing  escapement,  A r o n ( 1 9 6 2 ) c o m p a r e s ' t h e c a t c h i n g power o f an Kidd midwater t r a w l having Clarke-Bumpus sampler  size in  changes i n the  at the h i g h e r  and  (kt) i . e .  speed of towing"was i n c r e a s e d , the  a l s o increased".  l e n g t h were c a u g h t .  sampler  a 3 f t (,9m)  ( C l a r k e and  mouth o p e n i n g w i t h r e s p e c t  Isaacs-  mouth o p e n i n g and  a  Bumpus, 19 50 ) w i t h a 12.5  cm  :  to euphausiids.  He  states that, in  thousands of samples c o l l e c t e d  w i t h Clarke-Bumpus Samplers  the  were v e r y r a r e , w h i l e n e a r l y a l l  North  Pacific,  samples c o l l e c t e d same a r e a  euphausiids  with-the-Isaacs-Kidd  were d o m i n a t e d by  midwater t r a w l from  a 50-cm c o n i c a l ' s a m p l e r and  ( J e n k i n s , 1901) bottle.  the'catch  Efficiencies  zooplankton was  with  taken  present. as  s a m p l e r was  100%. 65%;  On  by  a 38-cm Hensen  obtained'with  catch  catch  this  of the  b a s i s the  t h a t of the  collected  sampler  a 8-litre  were c a l c u l a t e d w i t h r e s p e c t The  the  euphausiids.  Hansen and• A n d e r s on' ( 1962 ) compared t h e by  from  8-litre  to  water  efficiency  water total  bottle  of the  50-cm c o n i c a l s a m p l e r o n l y  Regan ( 1 9 6 3 ) i n v e s t i g a t e d t h e  suitability  of  Hensen 18%.  the  Clarke-Bumpus Sampler as-ah instrument- f o r - c o l l e c t i n g euphausiids. catches  Regan's d a t a  at higher  show a t e n d e n c y t o w a r d  speeds of t o w i n g .  The  increase  increased i n catch  at  15 the  higher  increased data by  s p e e d s becomes g r e a t e r age  and  size  and  a l s o show t h a t t h e  day  t h a n by  important  night.  i n the  i s greatest  average i n c r e a s e This  Tranter  t o compare t h e  the  Indian  show any  was  greater be  euphausiids.  ( 1965:) c o n d u c t e d a s e r i e s o f  abilities  ( i . e . the  "catching  Ocean S t a n d a r d S a m p l e r 1916)  d i f f e r e n c e w h i c h c o u l d be  (Tranter,  ( C u r r i e , 1962), to c o l l e c t  comparison between r e p l i c a t e  trials  power")  Clarke-Bumpus Sampler  T r o p i c a l Juday Sampler ( J u d a y ,  Statistical  i n catch  of  Regan's  s u g g e s t s t h a t v i s i o n may  of the A u s t r a l i a n v e r s i o n of the 1966), the  h i s t o r y stages  for adults.  d e t e c t i o n o f s a m p l e r s by  B a r n e s and in order  for l i f e  organisms.  samples f a i l e d  a s c r i b e d to  and  to  biological  escapement. Fleminger  and  C l u t t e r (1965) conducted a study  to f u r n i s h i n f o r m a t i o n about b i o l o g i c a l ' escapement. s a m p l e d two  captive zooplankton  samplers of s i m i l a r 1:2:4. built  design, having  runway a t c o n s t a n t d e n s i t y and  speed.  light  c o m p a r i s o n s i n v o l v i n g two relatively  fewer animals  populations  not  with  of the  this  catches  t r e n d was  light  three c o n i c a l  a  levels  were e v a l u a t e d . smaller  larger.  accentuated.  In the The  light  In a l l  denser  ratios  of  the  l a r g e r s a m p l e r f o r c o p e p o d s were  intensity.  intensities;  of  caught  The  same r a t i o s  for  o f m y s i d s , w h i c h p o s s e s s compound e y e s , were  at higher  ratio  specially  e f f e c t s o f two  samplers the  s m a l l e r to the  a f f e c t e d by  The  intensity  than the  They  mouth a r e a s i n t h e  These s a m p l e r s were towed i n a t a n k on  population  catch  populations  designed  the  disparity  between  the increased  catches  16 f o r s a m p l e r s o f v a r y i n g - s i z e was the  dark.  tence  From t h e s e  results  the  animals  broader i n the  light  s a m p l e r by enlarged  f o r those  animals  In-the  upon t o t r e a t t h e  width  speed' o f  area  (1966)  o f t h e mouth o f t h e  results  increased  estimates  of p o p u l a t i o n  for others.  s p e e d was  The  increased  as  concept i s  euphausiid size day  population of the  catch  were a f f e c t e d b y t h e intensity.  demonstrated; the  The  population Only the  c o l o u r of the authors  increasestimates also  concluded  effectsiof biological  increased  Dark-coloured of the  size  samplers.  catches  of by  that these  of  the  Estimates  were l a r g e r by  s a m p l e r and  Unpublished manuscript, courtesy O c e a n o g r a p h i c g r o u p , Nanaimo, B. C.,  the  a s c r i b e d to  t h a n - l i g h t coloured  f o r a l l samplers.  showing t h a t  d e n s i t y f o r some s p e c i e s ,  l a r g e r estimates  euphausiid  escape  light  speed of h a u l i n g  most p r o n o u n c e d f o r e u p h a u s i i d s .  s a m p l e r s gave c o n s i d e r a b l y  the  zooplanktonic  sampler increased  I n c r e a s i n g the  the  was  s t u d i e d the e f f e c t s  Catches o f - a wide range of  density.  light  this  s a m p l e r , - t h e s p e e d o f h a u l i n g , and  the  sampler  o f a - p e r i p h e r a l zone o f  of p o p u l a t i o n  t h a n by  study  size  of the  exis-  zone  which detected  present  McAllister  They i n t e r p r e t e d t h e i r  of the  that this  and  species.  not  the  Le B r a s s e u r  on  but  postulated  than i n  towing.  intensity  i n g the  light  of the-mouth of the  e s c a p e and  v i s u a l means,-  a f u n c t i o n of the  of the  could  i n the  authors  o f a zone a r o u n d t h e • p e r i p h e r y  from which the  as  greater  night  euphausiids changes i n results  e s c a p e m e n t , and  o f R. Le B r a s s e u r , Canada.  that  Pacific  17 for euphausiids b i o l o g i c a l Recent established  e s c a p e m e n t was m e d i a t e d  investigations  visually.  ( S m i t h , p e r s . comm.)  t h a t one-metre c o n i c a l  have  s a m p l e r s , which a r e a c c e p t i n g  95% o f t h e w a t e r p r e s e n t e d t o them, a r e p r e c e d e d by a c c e l e r a t i o n fronts  e x t e n d i n g ' u p t o one and o n e - h a l f " m e t r e s i n f r o n t  mouth o f t h e s a m p l e r .  of the  L a b o r a t o r y s t u d i e s have shown ( S m i t h ,  p e r s . comm.) t h a t • o f • c o p e p o d s t e s t e d , s t a g e V G a l a n u s h e l g o l a n d i c u s a r e c a p a b l e o f speeds  i n e x c e s s o f 67 cm/sec  f o r d i s t a n c e s up t o 7 cm, and L a b i d o c e r a t r i s p i n o s a acutifrons  o f speeds  t a n c e s up t o 15 cm.  and L_.  o f 70 and 80 cm/sec r e s p e c t i v e l y The l a r g e  copepod  Euchirella  for dis-  galatea  can swim a t a r a t e o f 100 cm/sec f o r up t o one and o n e - h a l f metres.  The s t i m u l u s w h i c h e v o k e d  injection  t h e s e r e s p o n s e s was t h e  o f 0.1 ml. o f s e a w a t e r a t a v e l o c i t y  o f 7.5 cm/sec  i n t o t h e s e a w a t e r medium 5 cm d i s t a n t " f r o m t h e a n i m a l . has a l s o  said  sampler would produced  that the acceleration  with b i o l o g i c a l  into  A h l s t r o m , 1954;  of, b i o l o g i c a l  of l a r v a l escapement  fish (Silliman,  B r i d g e r , 1957 ; C o l t o n , 1958 ; A r o n , 1 9 6 2 ;  Dr. P. S m i t h , B u r e a u Calif.  concerned  dealing with the errors  the estimates of the size  p o p u l a t i o n s by t h e e f f e c t s 1943;  s u r v e y e d above,  escapement o f z o o p l a n k t o n i c s p e c i e s , t h e r e  a l a r g e body o f l i t e r a t u r e  introduced  fronts  small j e t of water.  In a d d i t i o n t o t h e l i t e r a t u r e  exists  fronts preceding a plankton  p r o b a b l y ' b e ' g r e a t e r than the a c c e l e r a t i o n  by t h i s r e l a t i v e l y  Smith  o f Commercial  Fisheries,  La J o l l a ,  18 Isaacs,  1965 ; and P e a r c y , 1965 ).  In a l l of these r e p o r t s the  authors conclude that b i o l o g i c a l lem  i n obtaining  larval  escapement i s a s e r i o u s  a representative  sample from p o p u l a t i o n s  escapement i s s t r o n g . reported  of b i o l o g i c a l  However, none o f t h e I n v e s t i g a t i o n s  i n the l i t e r a t u r e  gives  any p r o p e r i n d i c a t i o n o f t h e  magnitude of the e r r o r s i n t r o d u c e d  by b i o l o g i c a l  escapement,  t h a n t h e s u s p i c i o n t h a t t h e s e e r r o r s may be l a r g e . It  the  of  fish. Thus, t h e e v i d e n c e f o r t h e e x i s t e n c e  other  prob-  i s c l e a r , therefore, that the p l a n k t o l o g i s t i s i n  difficult  p o s i t i o n o f knowing t h a t data  derived  from  c o l l e c t i o n s may be i n e r r o r , b u t o f n o t k n o w i n g how l a r g e e r r o r s may be. made w i t h  The p o s s i b i l i t y  these  e x i s t s , a l s o , that c o l l e c t i o n s  d i f f e r e n t s a m p l e r s may n o t be s u b j e c t  t o t h e same  errors. These s e v e r a l c o n s i d e r a t i o n s , n a m e l y t h e e f f e c t s o f biological  e s c a p e m e n t o f t h e s i z e and s p e c i e s  composition  of a  s a m p l e , have l e d t o t h e d e v e l o p m e n t o f a m a t h e m a t i c a l m o d e l which d e s c r i b e s  biological'escapement  m o d e l c a n be f i t t e d the  field  sampler. is  to give  t o data  derived  an e s t i m a t e  Evidence i s presented  sampler provided  f r o m c o l l e c t i o n s made i n  of the catching  power o f a p l a n k t  w h i c h i n d i c a t e s t h a t t h e model  c a p a b l e o f g i v i n g a good e s t i m a t e  plankton  i n such terms t h a t t h e  of the catching  power o f a  that c e r t a i n assumptions are v a l i d .  19  THE  MODEL: Barkeley  (Fig.  1) w h i c h w i l l  must a t t a i n specified the  ( 1 9 6 4 ) has p r o p o s e d  a m a t h e m a t i c a l model  y i e l d t h e minimum s p e e d  to c o m p l e t e l y escape  conditions.  t h a t an a n i m a l  from a p l a n k t o n sampler  These c o n d i t i o n s  i n c l u d e the r a d i u s  mouth o f t h e s a m p l e r , t h e s p e e d a t w h i c h  moving,  the  -  mine and  The  d e t e c t i o n d i s t a n c e would  i s unknown f o r any  B a r k e l e y ' s model,  biological  incapable  be d i f f i c u l t  to deter-  z o o p l a n k t o n i c organism.  In a d d i -  although i t a n a l y z e s the problem  escapement i n g e n e r a l t e r m s , namely the  where a l l t h e o r g a n i s m s  escape  of d e a l i n g w i t h  situation  the s i t u a t i o n  where a f r a c t i o n  I n sum,  h i s model  b u t i t c a n n o t be f i t t e d  from c o l l e c t i o n s  made i n t h e f i e l d ,  sampler, to give  i n f o r m a t i o n about  w i t h any  to data  sort  the performance  of a  indicates  t h o s e s t e p s w h i c h must be t a k e n t o m i n i m i s e t h e e f f e c t s escapement,  of  from the s a m p l e r , i t i s  zooplanktonic population escapes.  biological  of  the sampler i s  and t h e d i s t a n c e a t w h i c h t h e a n i m a l s c a n d e t e c t  sampler.  tion,  under  of derived  of p l a n k t o n of the  sampler. The  model w h i c h  same f o u r q u a n t i t i e s the  follows  i s f o r m u l a t e d i n terms  c o n s i d e r e d by B a r k e l e y ' s m o d e l .  f o l l o w i n g model can b e " f i t t e d  to f i e l d  of the However,  d a t a t o p r o v i d e an  estimate of the a b i l i t y  o f a p l a n k t o n s a m p l e r t o c a p t u r e any  zooplanktonic  I n t h i s model t h e p l a n k t o m  species.  r e g a r d e d as f i l t e r i n g  sampler i s  some c o n s t a n t p r o p o r t i o n o f t h e  p r e s e n t e d to i t over the range  of speeds  water  f o r w h i c h t h e model  20  is  to apply.  Implicit  in this  assumption t h a t the'model  assumption  i s the further  i s to apply only  i n the absence of  c l o g g i n g o f t h e meshes' o f t h e f i l t e r . The k i n e m a t i c b a s i s ' o f t h e m o d e l i s shown' i n F i g . 3. The The r a d i u s ' o f ' t h e ' m o u t h o f t h e s a m p l e r i s r o f t o w i n g i s S^,  Q  .  The  speed  The' d i s t a n c e a t w h i c h t h e a n i m a l s , i_.e_.  t h e ' p o p u l a t i o n o f • any spe'c ieis o r l i f e  hi story  s t a g e - o f any  s p e c i e s , c a n d e t e c t t h e p r e s e n c e o f t h e s a m p l e r by any means and r e s p o n d t o i t i s shown as t h e p l a n e , x , p e r p e n d i c u l a r t o the l o n g i t u d i n a l a x i s ' of the sampler.  The d i s t a n c e t o t h e  p l a n e , x , f r o m " t h e mouth o f t h e s a m p l e r i s - assumed t o r e m a i n c o n s t a n t as the" s p e e d  of towing i n c r e a s e s . - This' i s reasonable  i n view of the' f a c t t h a t ' t h e sampler f i l t e r s of water per u n i t • d i s t a n c e - over the range Possibly  a - more r e a l i s t i c  o f speeds t o be"used.  curve.  p l a n k t o n s a m p l e r s ' c a r r i e d ' o u t a t t h e SCOR -  in  The b a s i s o f t h i s  i s the r e s u l t • o f a wind t u n n e l study of f l o w  symposium o n • Z o o p l a n k t o n  amount  representation' of the surface of  r e s p o n s e , x, i s ' shown by t h e d a s h e d curve  t h e same  Sampling  1965 ( B a r y , p e r s . comm.),  through  ICES-UNESCO  Methods h e l d ' i n A u s t r a l i a  The s t u d y " s h o w e d ' t h a t t h e  p r e s s u r e g r a d i e n t s ' p r e c e d i n g t h e mouth o f ' t h e " s a m p l e r  approxi-  mate t o t h i s ' f o r m . - The" r e p r e s e n t a t i o n o f t h e s u r f a c e o f r e s p o n s e shown'by t h e " b r o k e n c u r v e ' i s t o a p p l y o n l y when t h e a n i m a l s d e t e c t t h e s a m p l e r , by means o f t h e a c c e l e r a t i o n preceding  it,  fronts  • •  T r e a t m e n t • of- t h e " s u r f a c e o f ' r e s p o n s e - as' a ' p l a n e i s n o t an i m p o r t a n t d e p a r t u r e f r o m r e a l i t y  because t h e r e w i l l  be .seme  21 p l a n e , x, i n w h i c h reacted.  i tw i l l  appear  t h a t a l l t h e a n i m a l s have  T h i s i s t r u e b e c a u s e t h e model d e a l s w i t h t h e r e a c t i o n s  o f a. p o p u l a t i o n • o f a n i m a l s p r e s e n t e d t o t h e s a m p l e r , and n o t with  t h e r e a c t i o n s . o f a n y one a n i m a l .  animals'  speed  F o r t h e same r e a s o n t h e  o f e s c a p e , S^, does n o t r e p r e s e n t t h e h i g h e s t  s p e e d t h a t any i n d i v i d u a l  a n i m a l can a t t a i n .  Instead  r e p r e s e n t s t h e mean- o f a l l t h e components o f a l l t h e a n i m a l s ' speeds p e r p e n d i c u l a r t o t h e l o n g i t u d i n a l The  w i d t h o f t h e zone a r o u n d  axis  the periphery  of the sampler.  o f t h e mouth o f t h e  sampler from which a n i m a l s can escape  i s p"*", t h e r a d i u s o f t h e  a r e a from which a n i m a l s cannot  i s r"*" .  I f i t is•assumed  t h a t ' a t any one t i m e t h e i n d i v i d u a l s  of a s p e c i e s a r e randomly -  escape  distributed  sampler, a l t h o u g h not n e c e s s a r i l y  a e r o s s t h e mouth o f t h e  throughout the water  column, then the p r o p o r t i o n of animals caught as t h e r a t i o escape  c a n be e x p r e s s e d  o f t h e a r e a o f t h e zone f r o m w h i c h a n i m a l s  t o t h e a r e a o f t h e mouth o f t h e ' s a m p l e r .  multiplied  by 100 c a n be r e f e r r e d  This  t o as p e r c e n t a g e  cannot  ratio  catch  (p b e l o w ) . The is  w i d t h o f t h e zone f r o m w h i c h a n i m a l s c a n e s c a p e  t h e p r o d u c t of' t h e ' s p e e d  t h a t the, a n i m a l s c a n a t t a i n  pendicular to the l o n g i t u d i n a l axis  o f the" s a m p l e r , S^, and  t h e t i m e t h a t t h e a n i m a l s have i n w h i c h s a m p l e r o v e r t a k e s them, x / S ^ . the speed  of towing.  per-  t o move b e f o r e t h e  This width i s a function of  The a r e a f r o m w h i c h t h e a n i m a l s  cannot  e s c a p e , A , c a n be e x p r e s s e d as fT t i m e s t h e s q u a r e o f t h e d i f f e r e n c e b e t w e e n t h e r a d i u s o f t h e mouth o f t h e s a m p l e r and  Figure  3 (facing)  The  k i n e m a t i c b a s i s of the  model.  s  0  —  speed  s  e  —  mean  r  Q  —  radius  —  mean  x  of  towing  speed of  of  escape  net  distance  at  which  net  can  be  detected broken  line of  r  p  1  —  —  curve  —  more  realistic  representation  x  radius  of  zone  impossible  ( r  peripheral  zone  overtake)  0  from  which  escape  is  - p ) of  escape  (before  net  can  23  the width  o f t h e zone f r o m  which  animals  A ^ r r c r - x s / s ) 1 o e o  1 —  2  ..Equation 1_ when d i v i d e d by t h e t o t a l sampler,  A^, and m u l t i p l i e d  expressed  percentage  a r e a o f t h e mouth o f t h e  by 100 y i e l d s  equation  (  - x s /s ) e  r  //Tr  2  o  : Equation  2 c a n be r e a r r a n g e d p = (1 -  i s the working If  is  S  q  S /R S ) e o o  X  samples taken at d i f f e r e n t  e q u a l t o P/B.  that  S  o  from  e  3  —  catch.  S  i n equation  becomes: 4  2  actually  The f a c t o r ,  i s the only v a r i a b l e .  which  —  c a t c h when two o r more  caught  i t i s true that there exists  J  (zB)  2  e q u a t i o n , 3_, i t  a q u a n t i t y , Q, f o r X S / r  I f t h e number o f a n i m a l s  is  1 0 0  speeds a r e a v a i l a b l e .  p = (1 - Q )  B then  x  x 100  in this  p o s s i b l e to solve f o r percentage  by  2  equation f o r percentage  3 the basic equation  }  to y i e l d :  i s the only v a r i a b l e  Substituting  2  o  r  which  2_ w h i c h  c a t c h , P.  = ( rr  P  can escape.  1 / 2  i s represented  some f a c t o r ,  z, c a n be o b t a i n e d I f this  = 1 - Q = P  i s true,  z, w h i c h  provided then: 5_  i t follows that: 1 - (zB)  1 / 2  = Q  6  24 B e a r i n g i n mind s i n c e Q = xS / r S , t h e n : ° e o o S  = x  w h i c h i s an then the  e  identity.  of the  i s the o n l y v a r i a b l e  be  and  q  1/2  B are a v a i l a b l e  - S .(zB. ) 01 ol 1  and  when  the r e s u l t i n g  6_  two  equation  e x p a n d e d and  percentage  o f P have been c a l c u l a t e d ,  2  - 2(X  (i_ _' < e  g  back i n t o  s e  e  eqn,  equation  only absolute  a s s u m p t i o n s made i n t h e internal  10  3_, f r o m w h i c h a p l o t  of  of  f o r m u l a t i o n of the model i s of the  in  some s y s t e m a t i c manner.  be  constant.  valid,  z can  be  the  internal.  propor-  I f t h e a s s u m p t i o n s made i n t h e  o f t h e model a r e not  are  data i s  c h e c k on t h e v a l i d i t y  the values  10  generated.  t h e model t o f i e l d  c h e c k i s g i v e n by  c o n s t a n t , z.  3_ can  10)  from e q u a t i o n  c a t c h a g a i n s t speed of h a u l i n g i s  The  equation  S / R S ) + l - p = o e o o  of X S which are c a l c u l a t e d  recursive.  P is calculated  9_  T h i s method-of f i t t i n g  tionality  been o b t a i n e d  —  zB  solved for X S  (X S /R S ) e o o  substituted  8  1 / 2  0  9_.  When v a l u e s  values  = S _ - S (zB.) o2 o2 2  1 / 2  Once z has  P =  lation  from e q u a t i o n  ) i s also constant  n  s o l v e d f o r z.  from e q u a t i o n  This  Therefore,  i n e q u a t i o n 1_  form: S  The  If  S (1 - ( z B ) o  o r more v a l u e s o f S  be  7 —  o  t h e q u a n t i t y QS^ i s c o n s t a n t . expression  can  /r  S  0  expected  formu-  to  I f the assumptions are v a l i d  vary z  will  25  MATERIALS AND METHODS: The  field  trials  were d e s i g n e d t o y i e l d  undertaken i n the course of t h i s two s o r t s o f i n f o r m a t i o n .  t a s k was t o a s s e s s t h e a b i l i t y describe  The p r i m a r y  o f t h e m a t h e m a t i c a l model t o  the processes of b i o l o g i c a l  escapement.  The s e c o n d -  a r y t a s k was t o d e t e r m i n e , by means o f t h e m o d e l , of the e r r o r s introduced composition  attributable  into  to biological  estimates of population  i n samples  study  t h e magnitude  escapement which a r e size  and s p e c i e s  c o l l e c t e d by v a r i o u s p l a n k t o n s a m p l i n g  devices. E v e r y e f f o r t was made i n t h e d e s i g n o f t h e f i e l d to ensure that the only v a r i a b l e each  t h e volume o f w a t e r and  f a c t o r was t h e s p e e d a t w h i c h  s a m p l e r was t o be h a u l e d t h r o u g h t h e w a t e r .  e s s e n t i a l t h a t t h e speed  I t was  o f h a u l i n g be a c c u r a t e l y known, t h a t  filtered  d i d n o t change f r o m h a u l t o h a u l ,  t h a t t h e same community o f z o o p l a n k t o n was s a m p l e d  haul.  trials  by each  These r e q u i r e m e n t s a r e b e s t met by v e r t i c a l h a u l i n g o f  the sampler location.  i n a p a r t i c u l a r body o f w a t e r a t one p o s i t i o n o r The d i s t a n c e  t h a t t h e s a m p l e r moves t h r o u g h t h e w a t e r  as w e l l as t h e t i m e t a k e n c a n be a c c u r a t e l y m e a s u r e d . i n t r o d u c e d by t h e f a i l u r e community w i t h  t o sample  each h a u l b e c a u s e  t o form l a y e r l i k e  or l e n s l i k e  t h e same z o o p l a n k t o n i c  of the tendency  possible  t o sample  of zooplankton  a g g r e g a t i o n s ( B a r y , 1 9 6 6 ) and t o  p e r f o r m d i e l m i g r a t i o n s a r e r e d u c e d by v e r t i c a l However s u c h p r e c a u t i o n s w i l l  Errors  be o f no a v a i l  hauling.  i fi t i s not  f r o m t h e same p a r c e l o f w a t e r  i n the course  26 of  field  the  o p e r a t i o n s and  t o keep t h e w i r e f r o m s t r a y i n g  from  vertical. An  isolated  ideal basin  location  for field  i n a protected  trials  location  and t h e r e f o r e movements• o f p l a n k t o n i c minimal.  I n B. C.  knowledge,  be a d e e p ,  i n which water  movements,  organisms , would  be  c o a s t a l w a t e r s an a r e a w h i c h , on p r e s e n t  i s most l i k e l y  that portion  would  to f u l f i l  of J e r v i s • I n l e t ,  the above requirements i s -  B r i t i s h ' Columbia, Canada,  lying  o ' o ' b e t w e e n 49 45 N. l a t i t u d e and 49 50 N.' l a t i t u d e and b e t w e e n o ' o • 124 00 W. l o n g i t u d e ' a n d 124 06 W, l o n g i t u d e ( F i g . 4 ) . I n this  a r e a i s a deep b a s i n w i t h a maximum d e p t h o f 732 m  Field  Procedure: During the t r i a l s  the  same p a r c e l  station If the  each morning  t h e s h i p was  e v e r y e f f o r t was - made t o sample  of water'each  day.  The  s h i p was  and a l l o w e d t o d r i f t  brought  station position  i t " w a s moved b a c k . o n I t was  s h i p more t h a n two  seldom  from on  with'the tide.  b l o w n b y w i n d more than'. one - q u a r t e r m i l e  were t a k e n e v e r y h o u r . the  (400fm).  station.  from  Positions  n e c e s s a r y t o move  o r t h r e e t i m e s e a c h day.-  However, s t r o n g  w i n d s were e x p e r i e n c e d o n l y once d u r i n g t h e c o u r s e o f t h e , f i e l d trials  a n d , f o r t h e most p a r t , t h e w e a t h e r • w a s c a l m .  conditions  the s h i p was'allowed t o d r i f t  currents,  Movement back  and  p o s i t i o n r e s u l t e d , to a t o t a l It  i s believed  organisms  forth  with•the  tidal  a c r o s s the- d e s i g n a t e d s t a t i o n  d i s t a n c e : o f ' about  one-half mile.  that by this'procedure'the c o l l e c t i o n s  were l i k e l y  :  In these  of  t o have been f r o m t h e same p a r c e l  of  Figure  4 ( f a c i n g ) The l o c a t i o n o f t h e f i e l d t r i a l s o f A u g u s t , 1965 and J a n u a r y , 1966. S i t e of s a m p l i n g i s i n d i c a t e d by an X.  27  28 w a t e r d u r i n g any one d a y . the  tidal  that  I t c o u l d o n l y be a s s u m e d ,  c u r r e n t s were d e m o n s t r a b l y weak d u r i n g any one d a y ,  f r o m day t o day i n - t h e - c o u r s e o f t h e f i e l d  w a t e r body d i d n o t change a p p r e c i a b l y . of  the r e s u l t s The  sampler. at  suggest that t h i s  design-of the f i e l d  same f o r e a c h  -  speed.  0.30 m/sec(0.50• m/sec f o r Eight replicate  I t was p o s s i b l e - t o c o m p l e t e  series with a n y one sampler  h a u l s were  only  one h a l f  i n one day% T h e r e f o r e each  -  i s a c o m p o s i t e o f tows made on two days . • The o r d e r i n r  which t h e speeds avoid  analysis  The s a m p l e r - was h a u l e d v e r t i c a l l y - f r o m 4-00 o r 500 m,  made a t each  series  The- s u b s e q u e n t  trials•was•the  one o f t h r e e speeds , n a m e l y ,  each  t r i a l s the  a s s u m p t i o n was r e a s o n a b l e .  C a t c h e r ) , 1.0 m/sec, o r 2 . 0 m / s e c .  of  because  o f h a u l i n g - o c c u r r e d was-randomized  systematic errors.-  descended sheave  The d e p t h t o - w h i c h t h e s a m p l e r  was d e t e r m i n e d b y p a y i n g o u t t h e w i r e o v e r a m e t e r i n g  and c h e c k i n g - t h a t t h e m e t e r -  s a m p l e r had b e e n r e t r i e v e d .  r e t u r n e d to- z e r o when t h e  The t o t a l  h a u l was r e c o r d e d w i t h a s t o p w a t c h . assigned  e a c h day t o  time r e q u i r e d  f o r each  Any h a u l - f o r w h i c h t h e  s p e e d was• n o t r e a c h e d w i t h i n the-. f i r s t • 5 0 m, o r w h i c h  s t o p p e d b e f o r e r e a c h i n g - t h e . s u r f a c e , was r e p e a t e d . When t h e s a m p l e r r e a c h e d t h e s u r f a c e was  c a r e f u l l y washed d o w n ' u s i n g  from a hose.  its-fiIter(net)  a h i g h - p r e s s u r e j e t of seawater  The s a m p l e " w a s ' p r e s e r v e d - i n 5%, n e u t r a l i z e d  forma-  lin.  The n u m b e r - o f r e v o l u t i o n s made by t h e - i m p e l l e r o f t h e f l o w  meter  was r e c o r d e d . The  August,  first  1965.  Then the -  set of f i e l d  A second  process trials  was'repeated. was c a r r i e d  out i n  s e r i e s was u n d e r t a k e n i n J a n u a r y , 1 9 6 6 ,  29 In  w h i c h t h e same p r o c e d u r e s were f o l l o w e d  three r e p l i c a t e The  h a u l s were made a t each  except that  only  speed.  P l a n k t o n Samplers: F i v e p l a n k t o n s a m p l e r s were u s e d d u r i n g t h e f i e l d  These were s e l e c t e d  as b e i n g r e p r e s e n t a t i v e o f ' t h r e e w i d e l y -  used c l a s s e s o f p l a n k t o n " s a m p l e r s , namely,"the the  conical  cylindrical high-speed The sampler  s a m p l e r m o d i f i e d by t h e a d d i t i o n portion"anterior  filter  consists  The  in front  J a n u a r y , 1966,  cm  c o n i c a l sampler used cm,  and  trials  this  of a c y l i n d r i c a l  the  in front  o f t h e mouth The  (Fig.  ring supporting  in this  The  conical  mm  square.  15 cm  cm  i n length.  During the  m o d i f i e d by  a t t h e apex o f t h e  the  I n a l l tows fitted  of a l a r g e c l a s s  and  Foxton,  30  bridles, with  i n the  aperture. (Currie  a  extend-  i n d i a m e t e r and  s a m p l e r a f l o w m e t e r was  70-cm N.I.O. s a m p l e r  6a) i s t y p i c a l  the  s t u d y has  i s 305  s a m p l e r was  lead weight  suspended  filter  o f t h e mouth - o f t h e s a m p l e r .  one-metre c o n i c a l  centre  conical  i s towed by t h r e e b r i d l e s  o f t h e mouth.  i n l e n g t h , w h i c h was  80 cm  d e s i g n of  of a c i r c u l a r  The mesh a p e r t u r e " a p p r o x i m a t e s t o 0.7  addition  encased  which t e r m i n a t e s i n a bucket i n which  mouth d i a m e t e r o f 100 80 cm  sampler,  o f an i m p e r v i o u s and t h e  s i m p l e s t of these" i s the o r i g i n a l  sample c o l l e c t s .  ing  to the f i l t e r ,  conical  sampler.  ( F i g . 5a) w h i c h  a conical  trials.  1957)  of p l a n k t o n samplers.  30 These s a m p l e r s a r e a l l b a s i c a l l y  the simple c o n i c a l  sampler  m o d i f i e d by t h e a d d i t i o n o f an i m p e r v i o u s , c y l i n d r i c a l ahead o f t h e f i l t e r . this  cylindrical  Nansen s a m p l e r samplers 1958)  portion,  They can be c l o s e d by . . " s t r a n g l i n g "  portion.  (Nansen,  This design o r i g i n a t e d with  1915).  (Kemp and H a r d y ,  I t was  m o d i f i e d i n the  1 9 2 9 ) , i n the Norpac  sampler  and a g a i n i n t h e I n d i a n Ocean S t a n d a r d s a m p l e r  the discovery (Marumo,  (Currie,  19 63- ) . The  N.I.O. s a m p l e r u s e d  d i a m e t e r o f 70 cm..  A canvas  i n the f i e l d  cylinder  122  cm  . a t t a c h e d t o a s h e e t m e t a l drum 3 0 . 5 c m i n precedes  and  i s a t t a c h e d to the f i l t e r .  anterior  cylindrical  conical portion ing  bucket.  150  portion cm  100  cm  trials  has a mouth  i n length i s  length which, i n turn, The  filter  i n length  has  an  f o l l o w e d by a  i n l e n g t h , which t e r m i n a t e s i n a  I n . t h e p r e s e n t ' s t u d y a f l o w m e t e r was  w i t h i n t h e mouth o f t h e c a n v a s  collects  mounted  cylinder.  The  a p e r t u r e of the  meshes a p p r o x i m a t e s " t o 200 m i c r a s q u a r e .  The  filter  sampler, u s e d  i n the f i e l d  1966,  this  trials  cylinder sampler  trials  s a m p l e r was  ( F i g . 6b).  The  in i t s original  new  During the January, canvas  o b t a i n e d with the standard  f o r m i n J a n u a r y , 1966, 1965,  and'are  not  were t h e same reported.  Catc'her ( B a r y e t a l . , 19 58 ) i s t y p i c a l  of a  c l a s s , the encased, high-speed p l a n k t o n samplers.  samplers of t h i s G u l f 111 the  new.  used w i t h o u t the  results  as t h o s e o b t a i n e d i n A u g u s t , The  was  i n the  Other  type i n c l u d e the Gulf 1 ( A r n o l d , 1959), the  ( G h e r i n g e r , 19520, t h e G u l f V ( A r n o l d , .1959),  J e t Net  fairly  ( C l a r k e , 1964).  The  and  Hardy P l a n k t o n R e c o r d e r  31 ( H a r d y , 1 9 3 6 ) i s towed a t h i g h s p e e d s , b u t i s i n a l l o t h e r respects d i s s i m i l a r  t o the above-mentioned  s a m p l e r s . Remarks  made b e l o w  p r o b a b l y do n o t a p p l y t o t h e Hardy P l a n k t o n  Recorder.  In the c o n s t r u c t i o n  outer, r i g i d usually  casing encloses the f i l t e r i n g  conical.  A consistent  t h a t t h e mouth o p e n i n g A result water  of t h i s  after  o f a l l o f t h e s e s a m p l e r s an  i s less  feature  s u r f a c e , which i s  f e a t u r e of these samplers i s i n diameter than the c a s i n g .  i s t o reduce  t h e speed  i t has e n t e r e d t h e mouth a n d , as a  of flow of the consequence,  l e s s e n s t h e damage done t o t h e z o o p l a n k t o n when t h e y c o n t a c t the  filter.  encased  Because  samplers  of the reduced  u s u a l l y have a l a r g e r t o t a l  aperture than c o n v e n t i o n a l c o n i c a l all,  of the encased  the  rear part  the  filter.  samplers  d i a m e t e r o f t h e mouth,  samplers  samplers.  the c o n s t r u c t i o n  s a m p l e r s . However, t h e p r i m a r y r a i s o n i s that  at  the sampler  which  organisms will  collected munity  chance  i s believed  through  of the high-speed i n uncased  d'etre of the high-speed  i t has l o n g been t h o u g h t  t h a t , i f t h e speed  i s towed i s i n c r e a s e d , z o o p l a n k t o n i c  of a wider range  have l e s s  but not  i t has p a s s e d  i s much more r o b u s t t h a n i s u s u a l l y  samplers  Most,  are p r o v i d e d w i t h f l o w meters i n  f o r metering the flow a f t e r Finally,  a r e a o f mesh  of sizes  to avoid  and swimming  the sampler.  ability  Thus t h e s a m p l e  t o be more r e p r e s e n t a t i v e  o f t h e com-  of zooplankton present. The  C a t c h e r ( F i g . 7a) c o n s i s t s  of a c y l i n d r i c a l  fibre-  g l a s s h o u s i n g 215 cm (84 i n . ) i n l e n g t h and 30 cm (12 i n . ) i n diameter.  T h i s h o u s i n g c a n be d i s a s s e m b l e d i n t o two main  32 parts. (Fig.  The  forward portion,  7b).  The  stabilizing The  fins  or  after portion  'body', c o n t a i n s t h e  c o n t a i n s the f l o w meter  attached at-right  angles' t o i t s  d i a m e t e r o f t h e mouth o p e n i n g i s 22.5  model o f t h e C a t c h e r u s e d  in this  cm  study- d i f f e r s  outer surface. The  from  that  i s rotated  that the t a i l  22.5  cm  (9 i n . ) ,  Laboratory  Methods:  In sorted  the l a b o r a t o r y the organisms  into  organisms  f o u r ' g r o u p s . Each  of s i m i l a r  o f c o p e p o d s o f t h e genus C a l a n u s .  most n u m e r o u s ; o v e r - 9 0 % o f t h e s p e c i m e n s C_. p l u m c h r u s  w i t h - a few s p e c i m e n s  These s p e c i m e n s g r o u p was var.  range  composed o f s p e c i m e n s  The  -  first  group  T h i s group  composed- o f s p e c i m e n s  This species  large  was  of conthe  were s t a g e V  in-length.  o f the copepod  The  i n length.  The  second  Eucalanus  b u n g i i most o f w h i c h were s t a g e I I I o r s t a g e IV  most o f w h i c h - w e r e  of  o f a d u l t C a l a n u s spp , .  f r o m 4 t o 5 mm  p o d i t e s r a n g i n g f r o m 3 t o 5 mm was  consists  They a r e r e p r e s e n t a t i v e  medium- t o l a r g e - s i z e d - z o o p l a n k t o n .  sisted  were  s i z e w h i c h were p r e s e n t i n numbers  enough f o r an a c c u r a t e ' a n a l y s i s . the  reduced  i n the samples  of these groups  to  of the  sampler i s of e q u a l d i a m e t e r t o the body, r a t h e r than to  bears  opening-closing  mechanism i s i n t h e f o r m o f a m e t a l d i s c w h i c h c l o s e the'mouth" o p e n i n g , and  and  (9 i n . ) .  d e s c r i b e d by B a r y e_t a _ l . ( 1958 ) i n t h a t t h e  open and  filter  third  o f t h e copepod' E u c h a e t a  a d u l t , r a n g i n g from' 5 to- 6 mm  bungii  copegroup  japonica, in length.  i s much more r o b u s t , t h a n C.. p l u m c h r u s  or  33  z~  •  F i g u r e 5a. The 1-metre c o n i c a l sampler rigged as it was used during the f i e l d t r i a l s of August, 1965.  F i g u r e 5b. The 1-metre conical s a m p l e r m o d i f i e d by the attachment of a weight to its b r i d l e s . The sampler was used as illustrated in the field t r i a l s of January, 1966.  34  —  F i g u r e 6a. The 7 0 - c m N . I . O . p l e r as it was u s e d i n the f i e l d t r i a l s of A u g u s t , 1965.  sam-  F i g u r e 6b. The 7 0 - c m N . I . O . s a m p l e r m o d i f i e d by the r e m o v a l of the canvas c y l i n d e r . The s a m p l e r was u s e d as i l l u s t r a t e d i n the f i e l d t r i a l s of J a n u a r y , 1966.  F i g u r e 7a.  The  Catcher  as i t w a s  r i g g e d d u r i n g the t r i a l s of August,  1965  F i g u r e 7b. Catcher  The  f i l t e r u s e d i n the  36 E.. b u n g i i .  The l a s t  group  i n c l u d e d a d o l e s c e n t and a d u l t  specimens o f the Euphausacea. Euphaus i a p a c i f i c a , r a n g i n g Every contained  Most  s p e c i m e n s were  f r o m 10 t o 20 mm i n l e n g t h .  s p e c i m e n o f E u c h a e t a j a p o n i c a and e v e r y  n e c e s s a r y t o sub-sample'and The  is  euphausiid  i n t h e ' sample"was' c o u n t e d , b u t t h e numbers o f  C a l a n u s s p p . and E u c a l a n u s " b u n g i i were v e r y l a r g e  Baskakov  adult  e s t i m a t e the' t o t a l s  s u b s a m p l i n g t e c h n i q u e was t h a t  (1951) ( s e e Appendix 1 ) .  and i t was  f o r these.  o f B r o d s k i i and  In t h i s  method t h e sample  spread e v e n l y over t h e bottom o f a l a r g e g l a s s d i s h  total  number o f s p e c i m e n s  total  a r e a o f t h e bottom- o f t h e d i s h  of t h e bottom o f the d i s h of specimens  lying  lying  o v e r a known f r a c t i o n i s counted.  i s varied•in  i n this-area  i s a b o u t 100.  o n e - h a l f o f t h e number o f s p e c i m e n s  bisected  at the boundaries of the area.  the t o t a l  of the f r a c t i o n  number o f s p e c i m e n s  In p r a c t i c e  the specimens  The f r a c t i o n  To t h i s  count  i n any way  T h i s sum i s m u l t i p l i e d  of the t o t a l  contained  of the  o r d e r t h a t t h e number  i s added  by t h e r e c i p r o c a l  and t h e  area to estimate  i n the dish.  i n at least  three  different  a r e a s were c o u n t e d f r o m e a c h s a m p l e . The mean c o u n t was u s e d to c a l c u l a t e  the t o t a l  number o f s p e c i m e n s .  counts d i d not agree w i t h i n made and t h e r e s u l t s ity  I f these three  1 0 % , t h r e e more c o u n t s were  o f a l l s i x c o u n t s meaned.  In the major-  o f s a m p l e s t h r e e c o u n t s were s u f f i c i e n t . The  be r e t a i n e d  s p e c i m e n s o f E u c a l a n u s b u n g i i were t o o s m a l l t o quantitatively  by t h e o n e - m e t r e  conical  T h e r e f o r e o n l y C a l a n u s s p p . , E u c h a e t a j a p o n i c a , and  sampler.  37 euphausiids  were c o u n t e d  i n the c o l l e c t i o n s  made w i t h  this  sampler. Mathematical  Procedure:  The: d a t a the  field  trials  obtained  f r o m t h e c o l l e c t i o n s made d u r i n g  were s u b j e c t e d  t o one-way a n a l y s i s o f v a r i a n c e  ( S t e e l e and T o r r i e , 1 9 6 0 ) t o d e t e r m i n e w h e t h e r d i f f e r e n c e s noted  between catches•made - a t d i f f e r e n t  considered The  as r e a l .  s p e e d s were t o be  '' "  number o f s p e c i m e n s c o l l e c t e d  i n each tow was c o n -  v e r t e d t o t h e p e r c e n t a g e o f t h e p r e d i c t e d p o p u l a t i o n o f each species which i t represented  by t h e p r o c e d u r e o u t l i n e d i n t h e  s e c t i o n on t h e m o d e l ' ( p p . 15 t o 2 4 ) . for  e a c h o f t h e 24 p a i r s " o f v a l u e s  speed o f h a u l i n g t o y i e l d X S  g  24 v a l u e s  Equation  10 was s o l v e d  o f p e r c e n t a g e c a t c h and of X S . g  A l l values o f  f o r each c o n f i g u r a t i o n o f s a m p l e r and" each" s p e c i e s  me'aned and a f i t t e d  curve  of percentage catch p l o t t e d against  s p e e d o f h a u l i n g was" g e n e r a t e d  from e q u a t i o n  3_.  F i n a l l y , an  e s t i m a t e - o f t h e p o p u l a t i o n of. e a c h s p e c i e s p r e s e n t  i n the  c o l u m n of- w a t e r s a m p l e d b y each s a m p l e r was o b t a i n e d . was cies age  done by m u l t i p l y i n g t h e n u m b e r o f i n d i v i d u a l s -  captured  were  This  of that  spe-  i n each s a m p l e r by t h e • r e c i p r o c a l o f t h e p e r c e n t -  o f t h e t o t a l w h i c h ' t h i s • c a t c h ; was c a l c u l a t e d t o r e p r e s e n t .  A mean e s t i m a t e d from t h e data  population" size  obtained" with  each  f o r each" s p e c i e s was computed sampler.  A p r o g r a m was w r i t t e n i n t h e F o r t r a n - IV l a n g u a g e f o r an I.B.M. 7040 c o m p u t e r w h i c h . p e r f o r m e d - a l l t h e above  calculations.  38  RESULTS: Summaries o f d a t a field in  are presented  d e r i v e d from t h e i n v e s t i g a t i o n s  i n Tables  2 t o 7.  The raw d a t a a r e r e p o r t e d  t e r m s o f mean s p e e d s o f , h a u l i n g ("speed c l a s s e s " ) , and mean  catches  of zooplankton,  class.  The v a l u e s r e p o r t e d f o r t h e f i e l d  1965, for  i n the  trials  trials  a t each The  variance  of August,  of January,  1966 v a l u e s  a r e means o f t h r e e  speed.  d a t a have been s u b j e c t e d t o one-way a n a l y s i s o f  ( S t e e l and T o r r i e ,  as t r e a t m e n t s .  1960) w i t h speed c l a s s e s  The c a l c u l a t e d  mean s q u a r e / e r r o r mean s q u a r e , expected  value  Although  the r e s u l t s  values  o f F, _i.e_.  i s reported together with the  of F f o r s i g n i f i c a n c e  a t t h e 95% l e v e l .  of a n a l y s i s of variance i n d i c a t e  speeds a r e s i g n i f i c a n t  and t h a t i n o t h e r  e n c e s b e t w e e n mean c a t c h e s significant,  at d i f f e r e n t  t h e mean c a t c h  f o r every  considered  treatment  some i n s t a n c e s t h e d i f f e r e n c e s b e t w e e n mean" c a t c h e s  towing  speed  a r e means o f e i g h t h a u l s a t each s p e e d ; t h e v a l u e s  the f i e l d  hauls  by s p e c i e s o r g r o u p , f o r e a c h  sampler,  that i n  at d i f f e r e n t  instances the d i f f e r speeds a r e not  i n c r e a s e s w i t h i n c r e a s e d speed o f  except  t h e 70-cm N.I.O. s a m p l e r i n  both c o n f i g u r a t i o n s . Figure  8a shows t h e r e s u l t s  o b t a i n e d by a p p l y i n g t h e  model t o d a t a f r o m c o l l e c t i o n s made w i t h t h e o n e - m e t r e sampler.  The smooth c u r v e s  of percentage  conical  catch plotted  against  s p e e d o f h a u l i n g were g e n e r a t e d  by s u b s t i t u t i n g s u c c e s s i v e l y  larger values  2_ ( p . 2 3 ) . No p o i n t s  ing  percentage  o f S^ i n e q u a t i o n  c a t c h as c a l c u l a t e d  from f i e l d  represent-  d a t a a p p e a r on  39 this  plot.  The  degree of agreement between v a l u e s  c e n t a g e c a t c h g i v e n by  the f i t t e d curve  s p e e d o f h a u l i n g i s shown i n F i g . 8b. shown by  these p l o t s ' are t h a t the  are best  able to a v o i d the  The  two  The  two  sampler,  and.that  per-  corresponding general  l a r g e r animals  -  o f t h e s a m p l e r i s much' r e d u c e d  f o r the  of  the  (euphausiids) selectivity  at the h i g h e r speeds of h a u l i n g .  c o n s t a n t s , p e c u l i a r t o each s p e c i e s a p p e a r i n  t h e t a b l e of' c o n s t a n t s ' a s s o c i a t e d w i t h F i g . 8b. X S , r e q u i r e d to generate" the  The  constant,.  f i t t e d c u r v e s , i s a measure  g  the a b i l i t y of a s p e c i e s ' t o escape from t h e ' s a m p l e r . of X S  g  a sampler.  proportionality  degree of v a r i a t i o n 95%  confidence percentages confidence  This  constant.  c h e c k on t h e v a l i d i t y  The  i s not. t r u e o f t h e v a l u e s Values  o f t h e model w h i c h t h e y  i n the values  confidence  limits  limits  shown b o t h  are  limits  afford.  upon t h e mean v a l u e  o f z.  as a b s o l u t e v a l u e s I t i s apparent  and  l a r g e r than  the  size  These asthe  w h i l e q u i t e s m a l l , , i n c r e a s e i n s i z e as  the  sampler i n which the  mouth ( F i g . 5 b ) .  the  that  haul  9a shows t h e ' r e s u l t s o b t a i n e d by  d i s t u r b e d by  the  The  decreases.  application  t h e m o d e l t o d a t a f r o m f i e l d c o l l e c t i o n s made w i t h t h e metre c o n i c a l  species  o f z,  o f z i s i n d i c a t e d by  o f t h e mean v a l u e s - o f z.  Figure  8b).  value  of z are given because of  number o f s p e c i m e n s o f a s p e c i e s c a u g h t ' p e r  was  of  i s independent of the s i z e of the p o p u l a t i o n of a  s a m p l e d by  of the  trends  The  products  those-obtained  X S  one-  f l o w of water i n t o the  t h e ' a d d i t i o n o f a body ( w e i g h t ) g  of  preceding  mouth the  f o r . e a c h g r o u p a r e much,  w i t h the unmodified  sampler  These d i f f e r e n c e s i n d i c a t e t h a t ; an o b v i o u s  effect  (Fig.  :  40 results the to  from the  p r e s e n c e o f t h e body p r e c e d i n g  s a m p l e r , i.e_. t h e detect  not  the  is clear  made i n t h e  ( F i g . 9b)  distance  t h a t one  f o r m u l a t i o n of the  manifestations  interval the  sampler at a g r e a t e r  body a l l o w s  the  of  animals  t h a n when i t i s  present. It  Two  presence of the  t h e mouth  of t h i s  points representing  model does n o t  are  a b o u t t h e mean v a l u e field  o r more o f t h e  t h a t not  only  hold  to the  for  i s the  of z l a r g e , but data  assumptions euphausiids.  confidence  t h a t the  fitted  f i t of  curve  is  poor . The (Fig.  6a)  results are  obtained  shown i n F i g . 10.  a s s u m p t i o n s made i n t h e for  this  formed.  sampler.  increasing  filtered the  There i s l i t t l e  per  explanation planktonic  no  through the speed.  The 70-cm N.I.O  o r g a n i s m s can  appear great i n the  catch.  detect  the  unit  valid  per-  i n the  distance  amount o f  amount towed,  water  enough t o a c c o u n t A possible distance  the  for  alternative  at w h i c h  sampler increases  as  zoothe  increases.-  r e s u l t s , shown"in F i g u r e sampler, modified  of the  decrease  decrease i n the  i s t h a t f o r some r e a s o n t h e  ( F i g . 6b).  reversal  occurs  not  c a l c u l a t i o n s have been  sampler, per  This  h a u l w o u l d not  speed of h a u l i n g  doubt t h a t  f o r m u l a t i o n of the model are  Therefore  reduction'which  collar  70-cm N.I.O. sampler-  F l o w m e t e r c o u n t s show a s l i g h t  of water p a s s i n g with  w i t h the  The  by  11a  the  most i m p o r t a n t  were o b t a i n e d  removal of the result  i s the  with canvas  apparent  t r e n d toward decreased c a t c h at h i g h e r  of h a u l i n g t h a t o c c u r r e d  when t h e  collar  was  present  the.  speeds  ( F i g . 10).  41 The  curves  are s i m i l a r  c o n i c a l sampler Figure  12a shows t h e r e s u l t s data  speed o f h a u l i n g  obtained  of percentage catch  There i s c o n s i d e r a b l e  points representing percentage catch ( F i g . 12b). This  points representing the  line  hauls  by a p p l i c a t i o n o f  plotted  I t should against  f o r C a l a n u s s p p . and E u c a l a n u s b u n g i i  superimposed.  data  w i t h t h e one-metre  c o l l e c t e d with, the Catcher.  noted that the curves  are  obtained  (Fig.8a).  the model t o f i e l d be  t o those  bungii  s c a t t e r i n those  c a l c u l a t e d from t h e f i e l d  s c a t t e r has a c o n s i s t e n t p a t t e r n .  the high-  and l o w - s p e e d h a u l s  of perfect f i t , while  made a t i n t e r m e d i a t e  The  l i e above  the points representing the  speeds l i e below t h e l i n e  of p e r f e c t  fit . Figure the  13 shows t h e r e s u l t s  model t o u n p u b l i s h e d  graphic  data  obtained  c o l l e c t e d by t h e P a c i f i c  G r o u p , N a n a i m o , B. C.  The d a t a  two  s i m i l a r plankton  samplers.  was  white;  was d a r k green..  the white ness.  the other  were c o l l e c t e d u s i n g  One o f t h e p l a n k t o n  samplers  C o l l e c t i o n s were made w i t h  reported  herein are f o r adult  They seem t o i n d i c a t e t h a t t h e v i s i b i l i t y  to  Oceano-  s a m p l e r u n d e r c o n d i t i o n s o f b o t h d a y l i g h t and d a r k -  The r e s u l t s  important  by a p p l i c a t i o n o f  f a c t o r i n determining  euphausiids.  o f t h e s a m p l e r i s an  i t s c a t c h i n g power w i t h  respect  euphaus i i d s .  "Data c o u r t e s y R. L e B r a s s e u r , P a c i f i c Oceanographic G r o u p , Nanaimo, B r i t i s h C o l u m b i a , C a n a d a .  42  ~\  r  i  1  1  1  r  X o  < o  «  Co/anus  spp.  X Euchaeta A  20  40  60  80  100  SPEED  OF  120  /aponica  Euphausiids  140  HAULING  160  180  200  220  cm/sec  8a  43  120 HO 100 *  -  90 -  o 80 iO 70 r  Q 60 UJ  < 50  U  3  i-  4 0  < 30 o 20  10 \0  J  I  L  10 20 30 40 50 60 70 80 90 100 110 120 CATCH (%) FROM FITTED CURVE  8b Figure 8a (facing) Percentage catch plotted against speed of hauling for the one-metre conical sampler. Figure 8b (above) Goodness-of-fit diagram for the results obtained with the one-metre conical sampler. K e y is the same as F i g . 8a. Table of Constants Species (group) Calanus spp.  X S 49.66  z  95% confidence l i m i t s  0.00011  + .000000017  (0. 15%)  Euchaeta japonica  188.76  0.011  + .000016  (1.4%)  euphausiids  361.48  0.25  + .000016  (0.66%)  44  45  O H < O  Q LU I< _l O _1 <  o  0  10 20 30 40 50 60 70 80 90 100110 120 CATCH (%) FROM FITTED CURVE  9b  Figure 9a (facing) Percentage catch plotted against speed of hauling for the modified one-metre conical sampler. Figure 9b (above) Goodness-of-fit diagram for the results obtained with the modified one-metre c o n i c a l sampler. K e y is the same as F i g . 8a. Table of Constant s Species (group)  z  X S e  Calanus spp. Euchaeta japonica euphausiids  290.33 511.164 1585. 89  95% confidence l i m i t s  0.000057  +.000000043  (.0.76%)  0.0051  +.000035  (6.9%)  0.0046  + .0018  (38.8%)  °  Calanus  spp.  X Euchaeta A O -h  20  40  60  japonica  Euphausiids £uca/anus  bungii  bungii  Chaetognaths _L  _L  _L  1  140  160  180  200  80  100  120  SPEED  OF  HAULING  cm/sec  220  Figure  10 ( f a c i n g ) R e s u l t s ' o b t a i n e d w i t h t h e N.I.O. 70-cm sampler. Percentage catch i s p l o t t e d against speed o f h a u l i n g . P e r c e n t a g e c a t c h has been c a l c u l a t e d o n t h e has i s o f t h e c a t c h a t 30 cm/sec as 100%. 1  i  47  T  r  i  r  1  1  r  100 90 80 70 60 50 40 30 20  °  Calanus  X  Euchaeto  A O  10 - A  20  40  _L  _L  60  80  100  SPEED  OF  120  spp.  Euphausiids  Eucalanus  140  HAULING  /aponica  hung/7 bungii  160  180  ±  200  220  cm/sec 11 a  48  120  x o I< o o  LU I-  < -J  ZD  O _J <  0  10 2 0 30 40 50 60 70 8 0 90 100 110 120 CATCH (%) FROM FITTED CURVE  Mb Figure 11a (facing) Percentage catch plotted against speed of hauling for the modified 70-cm N.I.O. sampler. Figure l i b (above) Goodness-of-fit diagram for the results obtained with the modified 70-cm N.I.O. sampler. Table of Constants Species (group) Calanus spp. Eucalanus b. bungii Euchaeta japonica euphausiids  XS. e  z  44.34  0.00019  95.79  0.00051  8.7234 461.35  0.017 0.12  95% confidence limits + .00000012 (0. 62%) + .00000069 (0. 13%) + .0000025  (0. 14%)  + .028  (23%)  49  1  r  100 90 80 70 60  i u 50 <  40 30 20  o  Calanus  X  Euchaeta  O  japonica  Euphausiids  A  I0  spp.  Eucalanus  0 20  40  60  80  100  120  SPEED OF HAULING  140  160  bungii  _i_  180  bungii  200  220  cm/sec 12a  50  0  10 20 30 40 50 60 70 80 90 100 110 120 CATCH (%) FROM FITTED CURVE  12b F i g u r e 12a (facing) Percentage catch plotted against speed of hauling for the Catcher. Figure 12b (above) Goodness of fit diagram for the results obtained with the Catcher. K e y i s the same as F i g . 12a. Table of Constants Species (group)  X S  z  95% confidence l i m i t s  Calanus spp.  155.94  0.0014  + .000012  (0.9%)  Eucalanus b . bungii  157.612  0.0054  + .000042  (7.7%)  0. 13  + .00094  (0.68%)  0.98  + .17  (17%)  Euchaeta Japonica Euphausiids  95. 716 358.17  51  100 h 90 80 70 60 x o I<  50 40 30 20  o WHITE  X DARK  10 0  O  20  40  60  80  100  SPEED  OF  120  140  HAULING  WHITE  160  -  daylight  - nig lit  180  200  220  cm/sec 3a  F i g u r e 13a (facing) Percentage catch plotted against speed of hauling for the P . O . G . s a m p l e r s . A l l results are for euphausiids . Figure 13b (above) Goodness-of-fit diagram for the results obtained with the P . O . G . s a m p l e r s . Because only two speed c were used a l l points l i e on the line of perfect f i t . Values of X S for the P . O . G . e White sampler-daylight  samplers 1189.0  "White s a m p l e r - d a r k  831.0  Dark Green sampler-daylight  421.0  Values of z with confidence l i m i t s are not given because only mean catches for each speed class were given.  53  Table Results  of F i e l d  2  Trials:  One-metre C o n i c a l  Speeds o f H a u l i n g Calanus  (cm/sec)  August,  1965  Sampler  29.39  101.50  7841  8258  206 .02  spp  Mean C a t c h : Specimens/haul Calculated  F = 0.5091  Tabled  Euchaeta j aponica  05  F  68  =  8312  2 - 5 7  ( 2  »  2 1  78  d f )  84  Mean C a t c h : Specimens/haul Calculated  F = 0.8096  Tabled  F  n c  = 2.57  (2,21  df)  Euphaus i i d s Mean C a t c h : Specimens/haul Calculated  used  F  22 2.8017  Tabled  Since these are o n e - t a i l e d throughout.  33  37  F _ = 2.57 .uo  F tests,  c  tabled  F ^  (2,21  is  df)  54 Table 3 Results  of F i e l d  Modified  Trials:  January,  1966  One-metre C o n i c a l S a m p l e r  Speeds o f H a u l i n g ( c m / s e c )  37.49  81.48  158.30  15,170  16,058  Calanus spp. Mean C a t c h : Specimens/haul  12,331  Calculated  Tabled  Euchaeta  F = 1.2474  F  = 3.46  (2,6 d f )  japonica  Mean C a t c h : Specimens/haul  104 Tabled  Calculated  131 F  Q 5  = 3.46  177 (2,6 d f )  F = 4.1681  Euphaus i i d s Mean C a t c h : Specimens/haul C a l c u l a t e d F = 30.2068  20 Tabled  52 F  = 3.46  342 (2,6 d f )  55  Table 4 Results  of F i e l d  Trials:  70-cm N.I.O.  Speeds o f H a u l i n g ( c m / s e c )  A u g u s t , 1965  Sampler  30.00  108.0  207.0  6175  4683  3655  Calanus spp. Mean C a t c h : Specimens/haul Calculated  Eucalanus  F = 29.3107  bungii  Tabled  F .  c  = 2.57 ( 2 , 2 1 d f )  bungii  Mean C a t c h : Specimens/haul C a l c u l a t e d F = 15.562  1060 Tabled  834 F  710  = 2.57 ( 2 , 2 1 d f )  Euchaeta j aponica Mean C a t c h : Specimens/haul Calculated  F = 3.881  40 Tabled  38  31  F  n n  = 2.57 ( 2 , 2 1 d f )  F  Q 5  = 2.57 ( 2 , 2 1 d f )  Euphaus i i d s Mean C a t c h : Specimens/haul Calculated  F - 3.58  10 Tabled  56  Table 5 Results  of F i e l d  Modified  Speeds o f H a u l i n g  Calanus  (cm/sec)  Trials:  J a n u a r y , 1966  70-cm N.I.O. S a m p l e r  31.45  92.00  178.53  4715  508 1  5025  spp  Mean C a t c h : Specimens/haul Calculated Eucalanus  F = 0.4770 bungii  Euchaeta  F  = 3.46  Q 5  (2,6 d f )  bungii  Mean C a t c h : Specimens/haul Calculated  Tabled  F = 4.2874  1871  1581 Tabled  = -  T  3  0 5  1835 ( >  4 6  2  6  d f  japonica  Mean C a t c h : Specimens/haul Calculated  F = 0.074  54  56  Tabled  F  Tabled  F  5  =  3  =  4  6  0  5  =  3  ,  4  6  0  57  ( 2  '  6  d  f  )  d  f  Euphaus i i d s Mean C a t c h : Specimens/haul Calculated  )  F = 4.5714  ( 2  '  6  )  57 Table 6 Results of F i e l d  Trials:  A u g u s t , 1965  Catcher Speeds o f H a u l i n g ( c m / s e c )  50.04  120.36  Mean C a t c h : Specimens/haul  391  475  Calculated  Tabled  221.41  Calanus spp.  F = 31.893  Eucalanus b u n g i i  F  .u o c  660  = 2.57  (2,21 d f )  bungii  Mean C a t c h : Specimens/haul  102  Calculated  Tabled -  F = 16.631  127 F  171  = 2.57 .uo n c  (2,21 d f )  Euchaeta j aponica Mean C a t c h : Specimens/haul No F v a l u e  5.25  5.725  7.00  calculated  Euphaus i i d s Mean C a t c h : Specimens/haul No F v a l u e  calculated  .125  .375  ,875  58 Table 7 P.O.G. U n p u b l i s h e d  Speeds o f H a u l i n g White Sampler  Results Obtained  (cm/sec)  100  200  1203  2219  1971  2867  2765  3265  (dark)  Mean C a t c h : Specimens/haul Dark G r e e n S a m p l e r  (daylight)  Mean C a t c h : Specimens/haul  All  1965  (daylight)  Mean C a t c h : Specimens/haul White Sampler  i n August,  results  are f o r catches of  j  Euphausiids.  59  DISCUSSION: If biological determining a plankton  t h e number o f z o o p l a n k t o n i c  factor in  o r g a n i s m s c a u g h t by  s a m p l e r , t h e n t h e number c a u g h t c o u l d be e x p e c t e d  to i n c r e a s e escape.  e s c a p e m e n t i s an i m p o r t a n t  as t h e s p e e d o f t o w i n g  The r e s u l t s  speed o f h a u l i n g  increased.  i s whether these  increased  escapement.  caught d i d i n c r e a s e  The q u e s t i o n catches  result  of primary from  decreased'  Because o f t h e randomized o r d e r i n  and t h e c o n t i n u e d  unlikely  -  tions the  sampling  a t one l o c a t i o n ,  t h a t any " c y c l i c a l phenomena s u c h as d i e l  of t h e o r g a n i s m s o r . t h e  effects  i n association, with  consistently  as t h e  importance  w h i c h t h e haulS.i. were made, t h e d e p t h f r o m w h i c h t h e y taken,  will  show, w i t h one e x c e p t i o n , t h a t t h e  number o f s p e c i m e n s o f any s p e c i e s  biological  i n c r e a s e s because l e s s  increased  tidal  were  i t is migrations  o f t h e ebb and f l o w o f p o p u l a - . c u r r e n t s c o u l d have  catches  at the higher  produced  speeds o f  hauling. Likewise  i tis difficult  in the d i s t r i b u t i o n selectively The  null  increased anlysis the less was  null  of the zooplanktonic  increase the"catch  hypothesis  t o s e e how any i n h o m o g e n e i t y organisms  at the higher  t h a t t h e mean c a t c h  could  speeds o f h a u l i n g .  d i d not increase  with  s p e e d o f h a u l i n g was t e s t e d i n the" s t a t i s t i c a l  o f t h e r e s u l t s . ' The t e s t s were s e t " up so as t o r e j e c t hypothesis  t h a n 5%. rejected  i fthe p r o b a b i l i t y  Of t h e 15 i n s t a n c e s i n 11 i n s t a n c e s  of i t s v a l i d i t y  analyzed the  and a c c e p t e d  - -  i n 5,  :  null  was  hypothesis  However, i n  60 the  five  instances  accepted  where t h e n u l l  t h e mean c a t c h  increased.  hupothesis  increased  as t h e s p e e d o f h a u l i n g  B e c a u s e i t i s i m p r o b a b l e t h a t t h e a c t i o n o f random  c h a n c e w o u l d c a u s e t h e mean c a t c h with  increased  hypothesis  had t o be  to increase consistently  s p e e d o f h a u l i n g , i t may be t h a t t h e n u l l  had t o be a c c e p t e d  because the i n c r e a s e  was s m a l l compared t o t h e v a r i a t i o n  inherent  i n catch  i n the f i e l d  technique. Another r e l e v a n t p o s s i b i l i t y filtered  more w a t e r a t h i g h e r  unlikely  i n view of the r e s u l t s  (1958),  Tranter  i s that the samplers  speeds of h a u l i n g . obtained  and Heron ( 1 9 6 5 ) ,  This i s  by B a r y e t a l .  and G i l f i l l a n  and P e a s e  (in  p r e p ) where s i m i l a r  per  u n i t d i s t a n c e , o v e r a w i d e r r a n g e o f s p e e d s t h a n was u s e d  i n the present  study.  q u a n t i t i e s of. w a t e r were  Nor a r e t h e i n c r e a s e s  i n catch  s p e e d s p r o p o r t i o n a l l y t h e same f o r a l l a n i m a l s , s a m p l e r , as w o u l d be e x p e c t e d  speeds.  catches being  Therefore  at higher  captured  with  at high each  i f t h e i n c r e a s e s were a r e s u l t  o f a l a r g e r volume o f w a t e r p a s s i n g higher  filtered,  through the sampler at the  i t may be assumed t h a t t h e i n c r e a s e d  speeds o f h a u l i n g r e s u l t  f r o m more  organisms  p e r u n i t volume o f w a t e r f i l t e r e d , _i.e_.  a decrease i n b i o l o g i c a l  escapement a t t h e h i g h e r  from  speeds of  hauling. If, catches  as t h e p r e v i o u s  d i s c u s s i o n i n d i c a t e s , the increased  c a n be assumed t o r e s u l t  escapement, the a b i l i t y of b i o l o g i c a l  from d e c r e a s e d  o f t h e model t o d e s c r i b e  e s c a p e m e n t c a n be a s s e s s e d .  biological t h e mechanism  Three s o u r c e s  i n f o r m a t i o n a r e a v a i l a b l e as a c h e c k on t h e v a l i d i t y  of  of the model.  61 The values  most p o w e r f u l  of these  of the p r o p o r t i o n a l i t y  calculated  checks i s found i n the  factor,  z.  A value  f o r each c o m p a r i s o n b e t w e e n two c a t c h e s  same s p e c i e s made 'at d i f f e r e n t  speeds .  the  be c o n s t a n t size  values this is  f o r any g i v e n  these  of z obtained  values  s a m p l e r and s p e c i e s as l o n g as  o f t h e p o p u l a t i o n s a m p l e d does n o t c h a n g e . from t h e data  collected  The  i n the course of  s t u d y , w i t h two e x c e p t i o n s , a r e n e a r l y c o n s t a n t .  shown by t h e r e l a t i v e l y  a r o u n d t h e mean v a l u e s 8b,  of the  I f the assumptions  made i n t h e f o r m u l a t i o n o f t h e model, a r e v a l i d , will  of z i s  s m a l l 95% c o n f i d e n c e  of z (Tables  This  intervals  associated with  Figs.  9b, l i b , 1 2 b ) . T h e r e i s a p e r s i s t e n t t r e n d t o w a r d l a r g e r  confidence  limits  on t h e mean v a l u e s  specimens of a p a r t i c u l a r Because t h i s results  occurs  s p e c i e s - i n t h e sample  i n every  from the f a c t  o f z as t h e number o f  instance i t almost  decreases. certainly  t h a t , i n the f o r m u l a t i o n of the model,  the assumptions a r e s t a t i s t i c a l .  That i s , t h e model  deals  w i t h t h e escape r e a c t i o n s of a l a r g e p o p u l a t i o n of z o o p l a n k t o n i c organisms; i t i s incapable of a s i n g l e decreases  organism.  As t h e number o f s p e c i m e n s o f a s p e c i e s  below a p p r o x i m a t e l y  model t o p r e d i c t t h e i r effect  11  10 t o 50, t h e a b i l i t y  escape r e a c t i o n s i s reduced.  shows most c l e a r l y  the t o t a l  o f d e a l i n g w i t h t h e escape r e a c t i o n s  sampler modified  caught over  Here t h e c o n f i d e n c e  of z f o r e u p h a u s i i d s  This  i n the instance of the Catcher  number o f e u p h a u s i i d s  individuals.  of the  are large.  limits  where  24- tows was o n l y on t h e mean  value  F o r 'the o n e - m e t r e c o n i c a l  by t h e p r e s e n c e o f t h e w e i g h t t h e numbers o f  62 euphausiids  c a u g h t were l a r g e enough f o r s t a t i s t i c a l  acy, but the values one  of z are not constant.  accur-  This implies that  o r more o f t h e a s s u m p t i o n s made i n t h e f o r m u l a t i o n o f t h e  model i s n o t v a l i d  f o r these  organisms,  u n l i k e the r e s u l t s  o b t a i n e d w i t h t h e same s a m p l e r f o r c o p e p o d s ( F i g . 9a) w h i c h conform t o those Estimates  obtained with the unmodified of the size  removing the e f f e c t s  sampler  of the p o p u l a t i o n s , a f t e r  of b i o l o g i c a l  e s c a p e m e n t by means o f t h e  m o d e l , o f t h e same s p e c i e s g i v e n by d i f f e r e n t another that by  c h e c k on t h e v a l i d i t y  of the model.  the s e v e r a l  organisms sizes  i s provided  samplers.  o f t h e same p o p u l a t i o n s o f z o o p l a n k t o n i c  (Table  8).  A comparison of the estimates  Catcher  as c a l c u l a t e d  from data  collected  shows t h a t f o r C a l a n u s s p p . t h e e s t i m a t e s t h a t f o r E_. j a p o n i c a and e u p h a u s i i d s 100%.  However, b e c a u s e t h e l a t t e r  represented  by so few i n d i v i d u a l s  the Catcher,  i t i s probable  the p o p u l a t i o n s i z e The tonic  of the  o f t h e C a l a n u s s p p . , E u c h a e t a j a p o n i c a , and e u p h a u s i i d  p o p u l a t i o n s g i v e n by t h e o n e - m e t r e c o n i c a l  by  This  are  i s p o s s i b l e t o make t h r e e c o m p a r i s o n s o f e s t i m a t e s  of the s i z e s  by  samplers  i t c a n be assumed t h a t t h e same p o p u l a t i o n was s a m p l e d  It  but  ( F i g . 8a).  i n A u g u s t , 1965 differ  by 2 0 % ,  the estimates  differ  two g r o u p s were  i n each sample  collected  that only the estimate of  f o r Calanus spp. i s v a l i d .  a s s u m p t i o n t h a t t h e same p o p u l a t i o n s o f  o r g a n i s m s were s a m p l e d by b o t h  strictly  s a m p l e r and t h e  t r u e , f o r the t r i a l s  samplers  zooplank-  may n o t be  of August, 1965, spread  over a  63  Table  8  Comparison of P o p u l a t i o n Estimates Water  August  i n Numbers/m  3  of  Filtered.  1965 1-Meter  Calanus spp.  C o n i c a l Sampler 5 3 o i+ 8  Catcher 42.58  Euchaeta j aponica  .28  .42  euphausiids  .13  .062  January  1966 Modified  Calanus spp.  1-m  Sampler  55.33  M o d i f i e d 70 cm N.I.O. S a m p l e r 43.61  Euchaeta j a p o n i c a  . 61  . 56  euphaus i i d s  . 68  .5 5  P.O.G. D a t a ( r e s u l t s White Sampler Dark  to  only)  (daylight)  Green S a m p l e r  White Sampler  f o r euphausiids  92.58  (daylight)  99.45  (dark)  S a m p l e r s assumed t o f i l t e r them.  102.68  100% o f w a t e r  presented  64 two  week p e r i o d .  estimates  of the size  reasonable sizes  B u t , because o f t h e c l o s e n e s s  of the  of the Calanus spp. p o p u l a t i o n , i t i s  t o assume t h a t l a r g e c h a n g e s d i d n o t o c c u r  of the populations of other  f r o m A u g u s t , 1965 t r i a l s  species.  i n the  Even i f t h e d a t a  i s q u e s t i o n a b l e , other evidence i s  available  from t h e t r i a l s  of January,  collected  by P.O.G. f o r c o m p a r i s o n .  t h a t t h e r e were any s i g n i f i c a n t  1 9 6 6 , and f r o m t h e d a t a I t i s much l e s s  changes i n t h e s i z e s  likely of the  z o o p l a n k t o n i c p o p u l a t i o n s s a m p l e d d u r i n g t h e two days r e q u i r e d to  complete the January, The  results  1966 t r i a l s .  from t h e J a n u a r y ,  1966 t r i a l s  p a r i s o n t o be drawn b e t w e e n t h e e s t i m a t e s  of the sizes  C a l a n u s spp. , E u c h a e t a j a p o n i c a , and e u p h a u s i i d g i v e n by t h e m o d i f i e d fied  one-metre c o n i c a l  70-cm N.I.O. s a m p l e r .  population estimated samplers within  and g r e e n s a m p l e r s  Here t h e e s t i m a t e s  agreement i s  w i t h i n 20%. o f t h e P.O.G.  by day and by n i g h t i s  of the size  p o p u l a t i o n g i v e n by t h e t h r e e s a m p l e r s design  of the euphausiid  o f t h e same b a s i c  agree w i t h i n 10% a f t e r t h e e f f e c t s  of b i o l o g i c a l  e s c a p e m e n t have been removed by means o f t h e m o d e l . estimates raw  data  standard  of the size  of the  f r o m t h e c o l l e c t i o n s made w i t h t h e two  1 0 % ; and f o r e u p h a u s i i d s  possible.  populations  For Calanus spp., the s i z e  agree w i t h i n 20%; f o r Euchaeta j a p o n i c a  using white  of the  s a m p l e r and t h e m o d i -  A f u r t h e r comparison of the r e s u l t s trials  a l l o w a com-  The  o f e u p h a u s i i d p o p u l a t i o n g i v e n by t h e  c o l l e c t e d a t a s p e e d o f h a u l i n g o f 100 cm/sec ( t h e used) a r e i n t h e r a t i o  1:1.67:2.1.  65 These c o m p a r i s o n s a p p e a r t o i n d i c a t e t h a t t h e r e s u l t s obtained  by a p p l i c a t i o n o f t h e model t o d a t a  different  samplers are comparable.  That i s , i f s a m p l e r A,  which  i s c a l c u l a t e d t o be 25% e f f i c i e n t  given  species  a t s p e e d x, c a t c h e s  with respect  same s p e c i e s  population i n both  a t s p e e d y, c a t c h e s  of that species  instances.  even t h o u g h t h e y  to a  25 s p e c i m e n s , and s a m p l e r  B, w h i c h i s c a l c u l a t e d t o be 50% e f f i c i e n t the  c o l l e c t e d with  with respect to  50 s p e c i m e n s , t h e  was 100 s p e c i m e n s p e r u n i t volume  That i t i s p o s s i b l e t o make s u c h  may be o n l y  estimates,  approximate, i s a great  advantage  when i t i s d e s i r e d t o compare t h e c o l l e c t i o n s made w i t h different  samplers at d i f f e r e n t  A third  source  the processes  the accuracy  of b i o l o g i c a l  i n t h e agreement between t h e v a l u e s  catch  c a l c u l a t e d from t h e f i e l d  taken  from t h e f i t t e d  curve  of percentage catch  used t o g e n e r a t e t h i s t o show o n l y  gross  curve  d a t a , and p e r c e n t a g e  only  escape-  catch  plotted  against  speeds o f h a u l i n g . Because t h e  c a l c u l a t e d f r o m t h e raw d a t a a r e t h e c o m p a r i s o n c a n be e x p e c t e d  a n o m a l i e s ' i n t h e raw d a t a .  because t h e p o i n t s used t o g e n e r a t e t h e curve it  with  of percentage  of percentage catch  speed of h a u l i n g f o r e q u i v a l e n t values  and p l a c e s .  of evidence concerning  w h i c h t h e model d e s c r i b e s ment l i e s  times  This will  i f t h e a s s u m p t i o n s made i n t h e f o r m u l a t i o n  i s so f a l l on of the  model a r e j u s t i f i e d . The  degree o f agreement between p o i n t s  representing  p e r c e n t a g e c a t c h , as c a l c u l a t e d f r o m raw d a t a , and p e r c e n t a g e catch  shown t h e f i t t e d  curves  is illustrated  i n F i g s . 8b  66  to  13b.  F o r t h e most p a r t a g r e e m e n t i s v e r y good.  calculated  f r o m t h e raw  data f o r the Catcher  The  f i t the  points  computed  curve r e a s o n a b l y w e l l , but w i t h a c o n s i s t e n t p a t t e r n i n t h e i r dispersion.  The  p o i n t s r e p r e s e n t i n g t h e c a t c h e s a t 50  and  200  cm/sec a r e h i g h and  100  cm/sec a r e l o w .  those r e p r e s e n t i n g the catches  A possible  explanation for"this  t h a t the hydrodynamic c h a r a c t e r i s t i c s b e t w e e n 100 Catcher  cm/sec and  comm.).  above a b o u t 200  to r e s u l t  from  a venturi  example, i n which  the f i t t e d  per u n i t  effect  d i s t a n c e at  filtered  there i s a gross  filtered  does n o t  obtained for  japonica  No  e x p l a n a t i o n appears  sudden i n c r e a s e .  possible  other than  much l e s s  collections An i n c r e a s e  and  Euchaeta  satisfactory  hydrodynamic  o f t h e w e i g h t , t h e e u p h a u s i i d s were  able to d e t e c t the sampler  which  r e a s o n a b l e , o r t h a t t h e y were much l e s s  res-  assuming t h a t f o r  some r e a s o n , p r o b a b l y a s s o c i a t e d w i t h t h e characteristics  sampler  a p p e a r t o be spp.  such  of  departure  cm/sec.  p o n s i b l e because the catches of Calanus show no  end  Here, a great i n c r e a s e i n the  cm/sec o v e r t h o s e made a t 100  i n t h e amount o f w a t e r  is  towing.  number o f e u p h a u s i i d s c a p t u r e d o c c u r s i n t h e made a t 200  change  at the a f t e r  c u r v e , i s t h a t of the r e s u l t s  by t h e w e i g h t .  be  I t i s b e l i e v e d t h a t the  e u p h a u s i i d s when t o w i n g w i t h t h e o n e - m e t r e c o n i c a l preceded  at  cm/sec (4- k t ) ( B a r y , p e r s .  at the h i g h e r speeds of  Another  may  of"the Catcher  T h i s i n c r e a s e i n t h e amount o f w a t e r  the sampler  from  cm/sec.  a c c e p t s a b o u t 10% more w a t e r  speeds of t o w i n g  thought  200  cm/sec  does n o t  either seem  a b l e t o escape  from  67 the  sampler.  A l l o t h e r s a m p l e r s show good a g r e e m e n t b e t w e e n  points calculated  from the f i e l d  d a t a and t h e c u r v e s g e n e r a t e d  by t h e m o d e l . The s m a l l c o n f i d e n c e l i m i t s and  the closeness of the f i t of the p o i n t s c a l c u l a t e d  field of  on t h e mean v a l u e s o f z  data to the f i t t e d  the d e s c r i p t i o n  curve demonstrate  of - b i o l o g i c a l  model f o r any one s a m p l e r .  the consistency  e s c a p e m e n t g i v e n by t h e  The q u e s t i o n o f t h e a b s o l u t e  accuracy of the e s t i m a t e s - o f percentage catch the  comparison of estimates of the s i z e  of  z o o p l a n k t o n i c organisms  is  some e v i d e n c e t h a t  samplers with  result  sampled  zone  a v o i d i n g a zone  F o r any one s p e e d  samplers with affected  openings  of. t u r b u l e n t  vertically  s m a l l e r mouth o p e n i n g s w o u l d  isms a v o i d t h e t u r b u l e n t  the it  more  I f organ-  w o u l d be t o u n d e r -  estimate the s i z e of the population of zooplankton This  those  be r e l a t i v e l y  l a r g e r mouth o p e n i n g s .  area, the r e s u l t  this  whichever  Therefore, the flow i n t o  than samplers w i t h  water  and l e n g t h o f w i r e  o f t u r b u l e n c e w o u l d be t h e same d i a m e t e r  s a m p l e r was b e i n g t o w e d .  There  T h i s u n d e r e s t i m a t i o n may  w h i c h d e v e l o p s when t h e l o n g t o w i n g w i r e i s : d r a w n through the water.  population  samplers.  s m a l l e r mouth  by  of the"population of zooplank-  (Table 7).  from t h e organisms  i s answered  o f t h e same  g i v e n by d i f f e r e n t  tend to underestimate the s i z e t o n i c organisms  from  sampled.  e f f e c t w o u l d become g r e a t e r as t h e a r e a o f t h e mouth o f sampler decreased.  Because  i s not p o s s i b l e t o c a l c u l a t e  t u r b u l e n t boundary  layer.  o f t h e many unknown  factors  the exact dimensions of t h i s  However, rough  calculations  68 (LeBlond, as  p e r s . comm.)  indicate  t h a t i t c o u l d o c c u p y as much  30% o f t h e a r e a o f t h e mouth o f t h e 70-cm N.I.O.  The  area  o f t h e mouth o f t h i s  s a m p l e r i s a p p r o x i m a t e l y one-  h a l f t h a t o f t h e one-metre c o n i c a l discrepancy  i n the estimates  sampler,  of the size  t o n i c p o p u l a t i o n w o u l d be 1 5 % . T h i s of t h e d i s c r e p a n c y of t h e s i z e  so t h e e x p e c t e d  o f t h e same  between t h e e s t i m a t e s  o f t h e same p o p u l a t i o n s o f v a r i o u s  zooplanktonic  two s a m p l e r s .  F u r t h e r a n a l y s i s o f F l e m m i n g e r and C l u t t e r ' s data  (1965)  ( C l u t t e r , p e r s . comm.) i n d i c a t e s t h a t t h e y may have been  a f f e c t e d by a r e g i o n d e v o i d  of zooplankton  towing  i n no way i n v a l i d a t e s  wire.  However, t h i s  ginal conclusions concerning zone f r o m w h i c h z o o p l a n k t o n The be  zooplank-  i s about t h e magnitude  t h a t appears t o e x i s t  s p e c i e s g i v e n by t h e s e  sampler.  four quantities  escapement.  their  ori-  the existence of a peripheral escape.  accounted  the only ones'involved  surrounding the  f o r by t h e model may n o t  i n the processes  However, t h e e v i d e n c e  of b i o l o g i c a l  indicates clearly  t h a t as  l o n g as t h e a s s u m p t i o n s made i n t h e ' f o r m u l a t i o n o f t h e model are  justified,  these  of major importance given plankton  four quantities  i n ' d e t e r m i n i n g t h e c a t c h i n g power o f any  sampler.  Now t h a t t h e r e s u l t s model d a t a  from f i e l d  g i v e n by t h e a p p l i c a t i o n  a l s o among s a m p l e r s ,  obtained  f r o m any one s a m p l e r ,  i t i s possible to discuss the r e s u l t s  obtained with the i n d i v i d u a l Dr. P. L e B l o n d , V a n c o u v e r , B. C.  of the  c o l l e c t i o n s have been shown t o be  consistent not o n l y f o r r e s u l t s but  a p p e a r t o be t h e ones  samplers .  Institute  o f O c e a n o g r a p h y , U.B.C.,  69 One-Metre C o n i c a l S a m p l e r : One trials  features of the r e s u l t s  was t h e " h i g h " e f f i c i e n c y  sampler. of  of the noteworthy  o f " t h e one-metre  from t h e  conical  I t appears"that'the"only"estimate of the e f f i c i e n c y  a c o n i c a l " s a m p l e r i s that"of"Hansen, and"Anderson  These a u t h o r s - e s t i m a t e d " the- e f f i c i e n c y • o f a" 50-cm  (1962).  conical  sampler  by c o m p a r i n g - t h e - c a t c h e s  i t - made - w i t h - s i m u l t a n e o u s  catches  made u s i n g - a n  wat e r b o t t l e .  eight-litre  Thus'their  e s t i m a t e o f 18% e f f i c i e n c y f o r t h e 50-cm c o n i c a l s a m p l e r i s -  w i t h r e s p e c t t o the • t o t a l " zooplankton the s m a l l e s t " organisms.  present, i n c l u s i v e of  ' Therefore,, t h e i r  estimate includes  o r g a n i s m s l o s t ' t h r o u g h - t h e meshes - of" t h e - f i l t e r  as w e l l as  o r g a n i s m s l o s t " a s - a' r e s u l t . o f b i o l o g i c a l - e s c a p e m e n t . B e c a u s e most o f t h e z o o p l a n k t o n  i n t h e a r e a s a m p l e d were v e r y  small,  e_.g_. c o p e p o d n a u p l i i ,- i t : i s - p r o b a b l e - t h a t - Hansen and A n d e r s o n ' s e s t i m a t e - of" t h e - e f f i c i e n c y : o f : the." c o n i c a l w i t h r e s p e c t to t h e t o t a l the water  zooplankton:present,  bottle,"has"no-real relation-to  the c o n i c a l sampler  be r e t a i n e d - c o m p l e t e l y b y the" f i l t e r  in  the present  conical  sampler  collecting  as shown by  the e f f i c i e n c y of  w i t h : r e s p e c t - t o ' z o o p l a n k t o n l a r g e enough  to  study  sampler  s t r o n g l y suggest  u s e d - i n - t h i s study  The r e s u l t s  obtained  t h a t " t h e one-metre  i s very e f f i c i e n t at  zooplankton.  70-cm N.I.O. S a m p l e r : . I n t e r p r e t a t i o n o f the- r e s u l t s the present  study  indicate  of" the- - f i e l d t r i a l s o f  t h a t , over  t h e range o f speeds  70 u s e d , t h e 70-cm N.I.O. s a m p l e r i s n o t as d e s i r a b l e a  plankton  s a m p l e r as t h e o n e - m e t r e c o n i c a l s a m p l e r , p r i m a r i l y b e c a u s e there  is little  increasing slight  of improving  i n flow  i n e x c e s s o f 30 cm/sec i s o b s c u r e .  when c l o g g i n g  probably  increase  i n the magnitude  fronts preceding  of  place.  can' c a u s e a l a r g e  of the a c c e l e r a t i o n pers.  comm.).  cause of the r e d u c t i o n  distance. i n catch  This  may  to  be  at higher  the  speeds  hauling. The  the  takes  e f f e c t i s to enable the zooplankton  the sampler at a g r e a t e r  immediate  a r e a n a l o g o u s t o what  i n flow  extent  of  Whatever the c a u s e ,  t h e mouth o f t h e s a m p l e r ( S m i t h ,  r e s u l t of t h i s  detect  and  by  cause of the  o f t h e meshes o f t h e f i l t e r  In s u c h c o n d i t i o n s , t h e r e d u c t i o n  The  The  t h r o u g h the sampler at speeds  e f f e c t s of the r e d u c t i o n  occurs  i t s performance  the speed at which i t i s h a u l e d .  reduction  hauling the  possibility  more s u c c e s s f u l r e s u l t s o f t h e f i e l d  70-cm N.I.O. s a m p l e r , m o d i f i e d  collar,  indicate that  o r g a n i s m s can d e t e c t  the d i s t a n c e  reduction (Table  4) i s r e a l  technique plotted  i n catch  at which  a t 200  Whether t h e  cm/sec o v e r t h a t a t 100  o r an a r t i f a c t  of f i e l d  or  i s not r e a l .  mind t h a t t h e c a n v a s c o l l a r  speed  small cm/sec  curves of percentage Catch  speed of h a u l i n g  i n catch  canvas  laboratory  f o r the m o d i f i e d  N.I.O. s a m p l e r have been c a l c u l a t e d on"'the b a s i s reduction  with  zooplanktonic  n o t change w i t h  i s not p r e s e n t .  i s n o t c l e a r . The against  by r e m o v a l o f t h e  t h e s a m p l e r may  when t h e c a n v a s c o l l a r  trials  may  70-cm that  this  However i t must be b o r n e i n n o t be t h e e n t i r e c a u s e  of  71 the  reduction  that,any may is  i n catch  i n the standard sampler.  i m p e r v i o u s c o l l a r ' ahead  cause a r e d u c t i o n  o f t h e mouth o f t h e  i n flow through the'sampler.  so,,some e f f e c t r e s u l t i n g  s a m p l e r c o u l d be e x p e c t e d .  the  The  be  sampler If this \  from the presence of the  cm m e t a l c y l i n d e r w h i c h r e m a i n e d  appear  I t may  30.5  i n p l a c e on t h e m o d i f i e d e v i d e n c e a t hand does n o t  c o n c l u s i v e r e g a r d i n g any h y p o t h e s i s .  I n any  event,  70-cm N.I.O. s a m p l e r m o d i f i e d by t h e r e m o v a l o f t h e  cylinder  from i n f r o n t  efficient  o f t h e mouth a p p e a r s  canvas  t o be more  t h a n t h e s t a n d a r d 70-cm N.I.O. s a m p l e r .  Catcher: The for  r e s u l t s based  C a l a n u s s p p . and  a c c u r a t e because  on c o l l e c t i o n s m a d e ' w i t h t h e C a t c h e r  Euc'alanus b u n g i i b u n g i i a r e p r o b a b l y  t h e number o f s p e c i m e n s  were c a u g h t a r e r e l a t i v e l y regarded with  large.  o f each  O t h e r r e s u l t . s must  c a u t i o n ; t o o few s p e c i m e n s *e  of Euchaeta  e u p h a u s i i d s were c o l l e c t e d  its  c a t c h i n g power w i t h r e s p e c t t o t h e s e g r o u p s .  field  trials,  the;Catcher- i s less  than the one-metre c o n i c a l for  t h e C a t c h e r may  of'hauling  able to c o l l e c t  sampler. E x t r a p o l a t i o n  percentage catch p l o t t e d  c a t e s t h a t a t speeds (6kt)  to give a r e l i a b l e  of speeds  g r e a t e r t h a n 300  result  japonica  e s t i m a t e of The  from the t u r b u l e n t  zone  results  used  i n the  zooplankton of the curves indi-  cm/sec  be an e f f i c i e n t - s a m p l i n g d e v i c e .  low c a t c h i n g - p o w e r of the C a t c h e r a t . t h e may  be  a g a i n s t . s p e e d of h a u l i n g  of h a u l i n g  which  __—_—_-______—- _____  and  i n d i c a t e t h a t , f o r the range  species  low s p e e d s  The  of h a u l i n g  c r e a t e d by up t o 400 m o f  72 wire  p r e c e d i n g the  relatively  additionally'because smaller being is  caught.  designed  in  same  time  at  The  were  of  the  (lead  the  to  sampler. weight)  some  might  are  able  detect'the  of  in  sampler's  to the  detect  sampler  organisms  sampler  power  that  can  is to  towed  (6  or  as i t  expected towing.  any  efficient kt  avoid  i s completely  be  without  s h o u l d be  80  cm,  already  At  increase  at  the  more).  one-metre  the  are  (80  cm)  organisms  adding  would  be  at  power  have  to  distance  detect  in' front could  the  alerted  of  decrease  presence body  the  approach-  the  selected  species  at.a  distance  in  little  expected before  i f the'organisms o f ,80  at  i t s mouth,  detect  weight, be  sampler,  mouth,  by• s u s p e n d i n g . a  could  a. d i s t a n c e  expected  to  sampler  the  been  However  of•the  I f any.of  unmodified  catching  able  that  ;  then"by  conical  a we igh.t. p r e c e d i n g t h e  be increased.  sampler  weight- c o u l d  of  assumed  reached'them, the  modified  distance  at which  excess  the  I t was  sampler  have  sampler;  of'horizontal  indicate  organisms  ing  would  the  the  obtain'an indication  distance  organisms  catching  Catcher  presence  the  the  of  in conditions  with  zooplanktonic  to  of  the  "Samplers:  undertaken  which  of  i s towed/ h o r i z o n t a l l y ,  mouth  i t i s usually  trials by  the  the'results  which  opening  Catcher  therefore•the  the  mouth  for zooplanktonic  towed,  power  Experimental  modified  be  the  somewhat  catching  speeds  When  to  increase  the  mouth  i t may"be•easier  unobstructed. to  the  small  cm  the  or  no  because the are  change the  weight not  able  presence•of  i t s catching  power  by  73 increasing  the d i s t a n c e , X ( F i g . 3 ) , at which the organisms  can d e t e c t  t h e p r e s e n c e o f t h e sampler..  X would p.  effect  Such an i n c r e a s e i n  an i n c r e a s e i n t h e p r o d u c t X S  g  (equation  10,  24). The p r o d u c t s X S^ i n c r e a s e d , on t h e a v e r a g e , by a f a c t o r  o f 4.4, w h i c h , b e c a u s e changed, is  i n a l l other  i s attributable  ways t h e s a m p l e r was n o t  to the presence of the weight.  not p o s s i b l e t o e v a l u a t e  this  result  because  o f t h e unknown  d i s t a n c e a t w h i c h t h e o r g a n i s m s were a b l e t o d e t e c t sence that at  o f t h e w e i g h t , b u t i t seems r e a s o n a b l e organisms  are not able t o d e t e c t  a d i s t a n c e much i n e x c e s s o f 80 cm.  Barkeley's  (1964) e s t i m a t e  zooplanktonic  organisms  It  the pre-  t o assume  the sampler  (unmodified)  Thus i t a p p e a r s  that  o f 250 cm f o r t h e d i s t a n c e a t w h i c h  are able  to detect  t h e s a m p l e r may be  excess i v e . The o b j e c t o f t h e t r i a l s  with the modified  s a m p l e r was t o d e t e r m i n e w h e t h e r the  sampler, at higher  speeds  70-cm  the decrease i n flow  N.I.O. through  of h a u l i n g , w i t h the concomitant  d e c r e a s e i n t h e c a t c h i n g power o f t h e s a m p l e r r e s u l t e d increased r e s i s t a n c e to flow through the f i l t e r , it  resulted  the  filter.  f r o m some p r o p e r t y The r e s u l t s  o f the canvas  from  or whether  sleeve  preceding  suggest s t r o n g l y that at l e a s t  some  o f t h e u n d e s i r a b l e p r o p e r t i e s o f t h e 70-cm N.I.O. s a m p l e r a t high  speeds  collar.  can be a t t r i b u t e d  Without the canvas  70-cm N.I.O  t o the presence of the canvas  collar  sampler approaches  the e f f i c i e n c y  of the  t h a t o f the one-metre  s a m p l e r as i s shown by F i g . 1 1 a .  However, a s l i g h t  conical reduction  74 in  catch  cult it  does o c c u r  b e t w e e n 100 and 200 cm/sec.  t o say whether t h i s r e d u c t i o n  i s an a r t i f a c t  of e i t h e r the f i e l d  p l o t s of percentage catch modified no  real  i n catch  against  Itis diffi-  i sreal,  or whether  or l a b technique.  The  speed o f h a u l i n g f o r t h e  70-cm N.I.O. s a m p l e r a r e c a l c u l a t e d on t h e b a s i s reduction  hauling.  i n catch  Therefore  they  amount o f c a u t i o n u n t i l whether t h e r e d u c t i o n  occurs  at the higher  must be r e g a r d e d there  speeds o f  with a c e r t a i n  i ssufficient  i n catch  that  e v i d e n c e t o show  i s , i n fact, real,  o r an a r t i -  fact . O n e - S q u a r e - M e t r e P.O.G. S a m p l e r s : The  results  o f t h e P.O.G. t r i a l s  dark green, m o d i f i e d , conditions  H e n s e n - t y p e s a m p l e r s were towed i n  o f b o t h d a y l i g h t and d a r k n e s s p e r m i t  ment o f t h e e f f e c t  of the v i s i b i l i t y  c a t c h i n g power w i t h r e s p e c t compound e y e s ) . one  square  i n w h i c h w h i t e and  the assess-  o f t h e s a m p l e r on i t s  to euphausiids  (animals  possessing  The s a m p l e r s u s e d had a mouth a r e a  equal t o  metre.  In d a y l i g h t t h e r a t i o  of the product  X S  g  f o r the white  s a m p l e r t o t h a t o f t h e d a r k g r e e n s a m p l e r i s 2.82:1. darkness the r a t i o cate in  These r e s u l t s  appear-  to indi-  t h a t t h e c o l o u r may be c o n t r i b u t i n g t o t h e e f f e c t i v e n e s s ,  t e r m s o f c a t c h i n g p o w e r , even a t n i g h t .  power o f t h e w h i t e low  i s 1.42:1.  In  sampler i n d a y l i g h t should  seems o b v i o u s f r o m t h e r e s u l t s .  butable  That t h e c a t c h i n g  to i t s being  readily  Probably  be r e l a t i v e l y this  is attri-  s e e n , b u t why t h e c o l o u r  should  75 c o n t i n u e t o be e f f e c t i v e  at night  i s not c l e a r .  darkness b i o l u m i n e s c e n c e from organisms s a m p l e r t o be more v i s i b l e it  would  Perhaps i n  cause a w h i t e  than a dark green one.  However,  m i g h t be e x p e c t e d " t h a t most o f t h e b i o l u m i n e s c e n c e w o u l d  be g e n e r a t e d when t h e b i o l u m i n e s c e n t o r g a n i s m s filter,  i n which'case  i t isdifficult  s t r i k e the  t o " see why t h e c o l o u r o f  t h e s a m p l e r s h o u l d make any d i f f e r e n c e . A comparison between t h e p l o t  of percentage catch  against  speed o f h a u l i n g w i t h r e s p e c t t o e u p h a u s i i d s f o r t h e dark g r e e n P.O.G. s a m p l e r , and t h e same p l o t cal  sampler, i n d i c a t e s  f o r t h e one-metre  t h a t t h e P.O.G. s a m p l e r  c a p t u r e e u p h a u s i i d s than t h e one-metre s a m p l e r . a l s o t h a t t h e Hensen-type  configuration  coni-  i s less able to I t indicates  i s p r o b a b l y n o t as  good a d e s i g n f o r p l a n k t o n s a m p l e r s as i s t h e s i m p l e  conical  sampler. P l a n k t o n Sampler Barkeley's  Design: (1964-) c o m p u t a t i o n s s u g g e s t t h a t p l a n k t o n  s a m p l e r s s h o u l d be made much l a r g e r t h a n t h e y a r e a t p r e s e n t if  the c o l l e c t i o n s  larger  a r e t o be r e p r e s e n t a t i v e  zooplanktonic organisms.  on t h e . a s s u m p t i o n t h a t  o f even t h e  H i s computations a r e based  z o o p l a n k t o n i c organisms  are able to  d e t e c t a s a m p l e r one n e t r e i n d i a m e t e r a t a d i s t a n c e o f 250 cm.  Because  zooplanktonic  the r e s u l t s organisms  of the present study i n d i c a t e  that  are probably not able t o detect the  p r e s e n c e o f a p l a n k t o n s a m p l e r one metre" i n d i a m e t e r a t a d i s t a n c e o f more t h a n 80 cm, B a r k e l e y ' s ' r e c o m m e n d a t i o n s t o be r e - e v a l u a t e d .  A decrease i n t h e d i s t a n c e a t which  need  .  .  7 6;  z o o p l a n k t o n i c organisms are able t o detect the sampler make i t p o s s i b l e t o d e c r e a s e  the size  -  and  y e t keep i t \an The  sizes  effective  of the optimal  r e s u l t s ' of t h i s ' study  show t h a t , f o r t h e range o f  o f 70 t o 10 0 cm a r e p r o b a b l y  representative that they  sampler  tool.  o f o r g a n i s m s "• s t u d i e d , p l a n k t o n - s a m p l e r s  diameters  w i t h mouth  adequate t o c o l l e c t  samples from z o o p l a n k t o n i c communities  are- h a u l e d  somewhat f a s t e r - t h a n  provided  u s u a l , _ i , e . 150  to  200 cm/sec a s ' o p p o s e d • t o t h e " m o r e u s u a l ' 1 0 0  an  e x t e n s i o n of- t h i s  reducing the diameter  should  cm/sec.  By  r e a s o n i n g , t h e p o s s i b l e p e n a l t y p a i d by o f t h e mouth . o p e n i n g . o f  a plankton  s a m p l e r may be r e c o m p e n s e d - b y t h e ' i n c r e a s e i n - t h e number o f organisms c o l l e c t e d ' b y - t o w i n g a t higher-speeds. part  of the reasoning ;  samplers,  underlying the design  but the present-study  T h i s has been  of the high  a p p e a r s t o be t h e f i r s t  attempt t o j u s t i f y t h i s ' reasoning, q u a n t i t a t i v e l y . the  23-cm mouth o f t h e - C a t c h e r  other high Arnold, less  of  10 cm.  and s t i l l  be u s e f u l , b u t most  I , A r n o l d , 1 9 5 2 ; G u l f V, -  o f t h e mouth- o p e n i n g  diameters  may be  be c o m p e n s a t e d f o r by i n c r e a s i n g t h e s p e e d  towing. From t h e above: b r i e f - d i s c u s s i o n - c o n c e r n i n g  sampler design to  Certainly  F u r t h e r work - i s - r e q u i r e d - t o d e t e r m i n e t h e  t o which the-diameter  reduced  appears-to  1959; J e t N e t , C l a r k e , 1964) have-mouth  than  extent  speed-samplers•(Gulf  speed  facilitate  plankton  i t a p p e a r s t h a t : f i r s t l y , - e v e r y e f f o r t be made t h e f l o w o f water' t h r o u g h - t h e s a m p l e r ;  t h e p l a n k t o n 'sampler s h o u l d be made as d i f f i c u l t  secondly,  to detect  as p o s s i b l e , n o t o n l y by means o f c o l o u r i n g , b u t by  77 s t r e a m l i n i n g a n d ' m a k i n g as s m a l l as p o s s i b l e must p r e c e d e cations  the-mouth  fications Use  F i n a l l y , no  which  modifi-  s h o u l d be made i n t h e d e s i g n o f any p l a n k t o n s a m p l e r  without thorough t r i a l s  The  of the sampler.  a l l parts  may  and  to- d e t e r m i n e : w h a t e f f e c t - t h e s e  modi-  have on t h e c a t c h i n g power o f t h e s a m p l e r .  Utility  of the, Model:  Perhaps' t h e g r e a t e s t ' u t i l i t y -  z o o p l a n k t o n e c o l o g i s t who  o f t h e model i s t o t h e  desires-to' obtain"data concerning  t h e s i z e and  s p e c i e s c o m p o s i t i o n o f t h e z o o p l a n k t o n i c com-  munity which  is quantitative.  For the purpose  of t h i s  dis-  c u s s i o n t h e z o o p l a n k t o n i c - c o m m u n i t y i s - d e f i n e d as t h o s e members of the marine size-limits animals prise  community w h i c h a r e p e l a g i c a n i m a l s b e t w e e n t h e  of' 0.5  mm- t o a-' f e w c e n t i m e t r e s i n l e n g t h .  l a r g e r than these s i z e - l i m i t s  Pelagic  a r e c o n s i d e r e d t o com-  the nekton. To s a y t h a t d a t a a r e q u a n t i t a t i v e ' i m p l i e s  that  the  number o f s p e c i e s a n d ' t h e i r r e l a t i v e - abundance' i n t h e a r e t h e same as-' i n t h e : community samp-led o f w a t e r which"'has problems  been' f i l t e r e d  sample  and t h a t t h e volume  i s a c c u r a t e l y known.  i n v o l v e d ' in-• d e t e r m i n i n g the'';volume  of water  The filtered  by t h e p l a n k t o n s a m p l e r have been d i s c u s s e d ' e l s e w h e r e i  -  L i k e w i s e the p o s s i b l e - e r r o r s  • .  i n t r o d u c e d ' i n t o d a t a as a  of the s e l e c t i v i t y of the sampler  ( p . 5) and  a n i m a l s t h r o u g h ' t h e meshes o f t h e f i l t e r discussed  above.  extrusion  (pp.  8  -ll)  result of  ( p . 3) have been  78 Presuming'- t h a t t h e p r e v i o u s a r g u m e n t s and- c a l c u l a t i o n s are v a l i d , is  t h e - v a l u e o f ' t h e model t o t h e z o o p l a n k t o n  ecologist  t h a t once a - s a m p l e r - h a s ' b e e n c a l i b r a t e d ' w i t h ' r e s p e c t t o  t h e s p e c i e s " to-be-' i n v e s t i g a t e d  s e l e c t i v i t y of' t h e s a m p l e r i s :  no. l o n g e r a problem' f o r ' s p e c i e s w h i c h ' t h e ' s a m p l e r c a p t u r e a t all'.''  Thus' t h e ' z o o p l a n k t o n - e c o l o g i s t  s e l e c t a sampling'device- which  will  need o n l y  c a p t u r e a' few s p e c i m e n s  of  a l l . t h e s p e c i e s t c b e s t u d i e d and c a l i b r a t e  to  those  i t with respect  :  species-to obtain-data r e l a t i v e l y free  introduced"by b i o l o g i c a l  i s able to  escapement.-  from e r r o r s  The m o d e l - w i l l a l s o be  u s e f u l when,it  i s ' d e s i r e d ' t o - c o m p a r e ' c a t c h e s made w i t h  erent samplers  at' d i f f e r e n t ' t i m e s .  when one s a m p l e r - c a n n o t ' b e be and  studied. very  used'to  This- i s ' e s p e c i a l l y v a l u a b l sample' a l l  the species to  Such'a' s i t u a t i o n ' m i g h t a r i s e when b o t h  large species'were  diff-  very  small  t o be s t u d i e d . -  However-, • t h e c a l i b r a t i o n  o f the- sampler- r e q u i r e s t h e  g r e a t e s t care- i f " a n y b e n e f i t i s " t o  a c c r u e ' f r o m ' i t s use. I t  must be c e r t a i n t h a t ' t h e s a m e p o p u l a t i o n ' i s  s a m p l e d by each  h a u l , and t h a t the- volume o f w a t e r  d u r i n g each  -  is  a c c u r a t e l y . known, of- t h e same.  filtered  A l s o , - enough .specimens o f  each s p e c i e s m u s t ' b e c a p t u r e d by e a c h - h a u l ' t o e n s u r e ;  in  t h e c a l c u l a t i o n s . ' 'The l o w e r  haul  limit-on  accuracy  t h e number o f s p e c i -  mens c a p t u r e d b y each h a u l i s ' p r o b a b l y from' 10-50. Another testing  important  application  of experimental samplers.  should enable  comparisons  o f t h e model i s i n t h e Here"the  A g a i n ' e v e r y p r e c a u t i o n must be  taken t o ensure' t h a t ' t h e - data c o l l e c t e d t h e model.  use' o f ' t h e m o d e l  t o be made' on' an a b s o l u t e b a s i s  b e t w e e n d i f f e r e n t samplers'.  of  r  fulfil  the requirement  79 GENERAL CONCLUSIONS: 1. ing  Biological  escapement can cause d i f f i c u l t i e s  a representative' sample from -  i n obtain-  zooplanktonic communities,  n o t o n l y i n t h e " form" o f " l o w e s t i m a t e s " o f " . p o p u l a t i o n for  single species, but"as"errors  densities  i n estimates of the species  c o m p o s i t i o n o f t h e community. 2. at  Four quant i t l e s which  the " r a d i u s " of" t h e ; s a m p l e r , t h e s p e e d ;  i t i s towed,"the  e f f e c t i v e " s p e e d which- t h e o r g a n i s m s  c a n a t t a i n ' i n " e s " c a p i n g from" t h e " sampler", and t h e d i s t a n c e a t r  which the organisms'can detect the sampler, are c o n s i d e r e d in  t h e model.'  These a r e p r o b a b l y the• f a c t o r s - o f ' p r i m e  i m p o r t a n c e i n d e s c r i b i n g the' p r o c e s s o f b i o l o g i c a l 3.  The r e s u l t s  g i v e n by t h e a p p l i c a t i o n  d a t a f r o m c o l l e c t i o n s made i n t h e f i e l d for  data- C o l l e c t e d w i t h  collected 4.  with, d i f f e r e n t  For the organisms  meters  to  o f t h e model t o  are not only  samplers. s t u d i e d , s a m p l e r s h a v i n g mouth  dia-  for collecting a  s a m p l e , p r o v i d e d t h a t t h e y a r e towed  200 cm/sec o r more.  consistent  any one s a m p l e r , b u t a l s o f o r d a t a  o f 70 t o 100 cm a r e p r o b a b l y a d e q u a t e  representative  escapement.  a t 150  80 REFERENCES  AHLSTROM, E. H. 19 54. Oceanographic Instrumentation. I l l ; B i o l o g . i c a l I n s t r u m e n t s . Pub I s . N a t n . Res . Counc . , Wash., 309 : 36-46. ARNOLD, E. L. J r . 1952. 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I s a a c s - K i d d midwater t r a w l , f i n a l r e p o r t . S c r i p p s I n s t . O c e a n o g r . R e f . 53-3. O c e a n o g r a p h i c E q u i p m e n t r e p o r t No. 1. J E N K I N S , J . T. 1901. The methods and r e s u l t s o f t h e German p l a n k t o n i n v e s t i g a t i o n s w i t h s p e c i a l r e f e r e n c e to the Hensen n e t s . P r o c . T r a n s . L p o o l . b i o l . Soc . , 15: 2 7 9 - 3 4 1 . JUDAY, C. 1916. L i m n o l o g i c a l A p p a r a t u s . . T r a n s . Wis. S c i . A r t s L e t t . , 18:566- 592.  Acad.  KEMP, S. and A. C. HARDY. 1929.. The D i s c o v e r y i n v e s t i g a t i o n s . O b j e c t s , , e q u i p m e n t ,. and m e t h o d s . I I . The s h i p s , t h e i r e q u i p m e n t and t h e methods u s e d i n r e s e a r c h . D i s c o v e r y Rep . , 1: 151-232 .' '' : ' " KUNNE, C. 1933. W'eitere U n t e r s u c h u n g e n z o m V e r l e i c h d e r F a n g f a h i g k e i t v e r s c h i e d e n e r M o d e l l e von v e r t i k a l f i s c h e n d e n plankton-netzen. Rapp . P_. -y_. Reun . C o n s , perm . i n t . E x p l o r : . • Mer , 8 3:1-35. " " " MARUMO, R. 195.(8 J On t h e n o r p a c s t a n d a r d p l a n k t o n n e t . Oceanogr. Rep. J a p a n Met. Agency , 6( 1 ): 4 5 - 4 7 . NANSEN, F. 1915. C l o s i n g n e t s f o r v e r t i c a l h a u l s and f o r h o r i z o n t a l towing. P u b l . C i r c o n s t . Cons . perm . i n t . E x p l o r . Mer, 67: 1-8. PEARCY , W. G. 1965. Day-night d i f f e r e n c e s i n mid-water catches of micronekton. ( P a p e r g i v e n a t ICES-SCORUNESCO. symposium on Z o o p l a n k t o n S a m p l i n g M e t h o d s . Cronulla, Australia.)  trawl  REGAN, L. 1963. Field- t r i a l s w i t h the Clarke-Bumpus p l a n k t o n sampler. E f f e c t s o f coarse and f i n e meshed n e t s o v e r a r a n g e o f s p e e d s on e u p h a u s i i d c o l l e c t i o n s . Univ. Br. Columb"-. I n s t . O c e a n o g r . Manus c r . Rep . 16 (mimeo) pp. 28. SHEARD , K. 1941. I m p r o v e d methods o f c o l l e c t i n g organisms. Rec. S. A u s t . Mus . , 7: 11-14.  marine  S I L L I MAN, R. P. 1943.. A s t u d y o f v a r i a b i l i t y i n p l a n k t o n tow n e t c a t c h e s o f P a c i f i c p i l c h a r d ( S a r d i n o p s c a e r u l e a ) eggs. J . mar. R e s . , 6 ( 1 ) : 74-83. :  STEEL, R. G. D. and J . H. TORRIE. 1960. P r i n c i p l e s and Procedures of S t a t i s t i c s . M c G r a w - H i l l Book Company I n c . , New Y o r k , r9T>0~ :  TRANTER, D. J . 1966. the A u s t r a l i a n Clarke-Bumpus sampler and c a l i b r a t i o n t a n k . £.S.I_.R.C_. D i v . F i s h . O c e a n o g r . T e c h . Pap. 19.  83 TRANTER, D. J . ' and A, HERON. 1965.. F i l t r a t i o n c h a r a c t e r . i s t i c s o f Clarke-Bumpus samplers. A u s t . J_. M a r . F r e s h w . Res. , 16: 2 81-291. .WINSOR, "C. P. and_G. L. CLARKE. 1940.. . A, s t a t i s t i c a l s t u d y o f v a r i a t i o n i n t h e . c a t c h of. p l a n k t o n n e t s . J . Mar. Res . , 3 ( 1 ) : 1-34. :  WIBORG, K. F. 1 9 4 8 . E x p e r i m e n t s w i t h t h e C l a r k e - B u m p u s p l a n k t o n s a m p l e r and w i t h a p l a n k t o n pump i n t h e L o f o t e n a r e a i n N o r t h e r n Norway. F i s k . D i r . S k r . , 9 ( 2 ) : 1-22.  84  APPENDIX I The  Subsampling Technique: The  s u b s a m p l i n g t e c h n i q u e o f B r o d s k i i and B a s k a k o v  consists  o f c o u n t i n g t h e number o f s p e c i m e n s  group which l i e w i t h i n bottom of a d i s h .  of a species  distri-  i n t h e b o t t o m o f t h e dish'.  b u t i o n w h i c h a p p e a r s even t o t h e eye i s a d e q u a t e .  A  (3-5) times the l e n g t h  be s u b s a m p l e d .  A source of s y s t e m a t i c arises  a r e met  t h e method  can  data.  error  i n the subsampling t e c h n i q u e  from the i n t e r a c t i o n between the a n i m a l s which are t o  be s u b s a m p l e d  and t h e w a l l s  a zone a t t h e j u n c t i o n  of the d i s h .  of the w a l l s  i n which a n i m a l s are not found. a n i m a l s a r e 'evenly '• area of the bottom m a l s a r e evenly •  error  arises  T h e r e t e n d s t o be  and b o t t o m o f t h e  of the d i s h .  dish  Thus t h e a r e a i n w h i c h t h e  distributed is slightly The  s m a l l e r than the  area i n which the a n i -  d i s t r i b u t e d can be t e r m e d t h e e f f e c t i v e  area of the bottom of the d i s h . atic  be  of the specimens which are t o  I f these c r i t e r i a  p r o v i d e a c c u r a t e and p r e c i s e  distri-  A l s o the  d i a m e t e r o f t h e ( c i r c u l a r ) a r e a t o be c o u n t e d s h o u l d several  or  a known f r a c t i o n o f t h e a r e a o f t h e  T h i s method depends upon a n ^ e v e n  b u t i o n of the specimens  (1951)  from e r r o r s  A further  source of system-  i n d e l i m i t i n g t h e a r e a t o be  counted.  T h e r e f o r e i t i s b e s t t o subsample  specimens  to determine the exact f r a c t i o n of the e f f e c t i v e  area of the bottom of the d i s h represents.  This  a known number o f  w h i c h each s u b s a m p l i n g a r e a  i s done by m a k i n g  10-20  c o u n t s and  85 obtaining  t h e mean number o f s p e c i m e n s p e r s u b s a m p l i n g  In p r a c t i c e b e f o r e each  i t i s desirable  count  t o r e d i s t r i b u t e the specimens  of, t h e number w i t h i n  the subsampling  A l s o o n e - h a l f o f t h e number o f a n i m a l s w h i c h boundaries animals  completely within  the boundaries  o f t h e sub-  9 g i v e s a summary o f t h e r e s u l t s o f 15 c o u n t s  with a subsampling  area nominally equal t o l/20th  of t h e b o t t o m o f t h e d i s h . euphausiids.  The d i s h  I f the subsampling  of the area  a r e a had been  precisely  o f t h e a r e a o f t h e b o t t o m o f t h e d i s h , each  mean number o f e u p h a u s i i d s p e r s u b s a m p l i n g indicates  that  the subsampling  made  c o n t a i n e d 1343  a r e a s h o u l d have c o n t a i n e d 67.15 e u p h a u s i i d s .  This  l i e across the  area .  Table  l/20th  area.  o f t h e a r e a s h o u l d be added t o t h e number o f  lying  sampling  area.  subsampling  However, t h e  a r e a was 6 3 . 8 .  area i s a c t u a l l y  l/21st  of t h e e f f e c t i v e a r e a o f t h e bottom o f t h e d i s h . The  goodness of f i t o f t h e p r e d i c t e d  of e u p h a u s i i d s i n t h e d i s h value f o r Chi-Square. of t h e subsampling of t h e d i s h  was d e t e r m i n e d  Calculation  gave a v a l u e o f 4.66.  by c a l c u l a t i n g a  of Chi-Square  area being l/20th  agreement between t h e p r e d i c t e d In t h e d i s h .  and a c t u a l numbers  on t h e b a s i s  o f t h e area o f the bottom  This i n d i c a t e s  and a c t u a l  very  good  number o f s p e c i m e n s  86  Table 9 Results of Fifteen Euphausiids  S u c c e s s i v e C o u n t s o f the' Number  L y i n g W i t h i n , l/.20th o f t h e A r e a  of th  B o t t o m of, a D i s h C o n t a i n i n g 1343 E u p h a u s i i d s  Counted  ,  Counted  Counted  59  68  64  61  68  66  63  62  65  62  65  59  60  66  69  Total  =  Mean  = 63.8  Expected  957  number w i t h i n  Chi-Square Probability  subsampling  area  = 67.15  = 4.66 of a larger  Chi-Square  (14 d f ) = .99  

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