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An evaluation of the current minimum legal size limit for the Dungeness crab (Cancer magister Dana) fishery… Smith, Barry Douglas 1988

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AN EVALUATION OF THE CURRENT MINIMUM LEGAL SIZE LIMIT FOR THE DUNGENESS CRAB (Cancer magister DANA) FISHERY NEAR TOFINO, BRITISH COLUMBIA By BARRY DOUGLAS SMITH B . S c , The U n i v e r s i t y of New Brunswick, 1974 M . S c , The U n i v e r s i t y of B r i t i s h C o l u m b i a , 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department  of  Zoology)  We accept t h i s t h e s i s as to the  required  conforming  standard  THE UNIVERSITY OF BRITISH COLUMBIA November (c)  Barry Douglas  1988 Smith,  1988  In  presenting  this  degree at the  thesis in  partial  fulfilment  of  the  requirements  for  an advanced  University of British Columbia, I agree that the Library shall make it  freely available for reference and study. I further agree that permission for extensive copying of  this  department  or  publication  thesis for by  his  or  scholarly purposes may be granted by the her  It  is  understood  that  my  copying  or  of this thesis for financial gain shall not be allowed without my written  permission.  Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3  DE-6(3/81)  representatives.  head of  ABSTRACT The  Dungeness  crab  B r i t i s h C o l u m b i a has of  165  mm  yield-  lack  of  regulated  spine-to-spine  carapace  and  movement was  Dungeness  crab  1987.  followed  as  length  fishery  near  the  exploitation  Male  nearly  all  within  the  movement,  from  fishery  s u c h as  and  by  a  on  these of  1985  the until  females  was  subsequently  increments-at-size ,  size-at-maturity, commercial  limit  growth,  study  and were  moult  notch-tosize  April  in  limit  precluded  year  males  entered  the  size  fishing  fishery  Size  frequency  legal-sized  (>154  mm  the  155.0+11.2  rate  surviving  to  of  mating  success  males  in  mm  instar  this  (M=2.8-4.5),  have a  low  size.  Legal-sized  mortality  rate  (F=5.1-6.9).  the  commercial  catch  analysis  (*50%  instar hence  during  notch-to-notch  legal  of  mm the  been  two  B.C.  on  size  Information  intensive  settlement.  mortality  component  has  pre-recruit  periods,  fishery  and  rates.  Sublegal-sized  fishing  154  E v a l u a t i o n of  Tofino,  entered  C .magi s t e r  after  (CW,  behavior.  information  intermoult  mortality,  an  of  males  width  analyses  mating  cohort  trap  population variables  in  yielding  of  pairs,  and  Dana)  by a minimum l e g a l  century.  obtained  A  exploited,  year  this  eggs-per-recruit  variables  March  early  i n f o r m a t i o n on b a s i c  mortality,  magi s t e r  been  n o t c h CW) s i n c e by  (Cancer  is  of a  high  their revealed  CW)  have  composed  of  natural  (<10%)  high  Consequently, males  are  instar).  annual  a  that  males  this  probability  males  fourth  of  annual  a  small  in  larger  instars.  Page  i i  Despite female the  females  catch  most  lightly  curves  males  fewer  of  large  four  fished  larger  may be  possibility  male,  markedly  improved  However,  eggs-per-recruit  50% d e c l i n e  limit  production  To  facilitate  changes  in  in  interactions that  trap,  by  of  based  processes, different  times,  crabs  sizes  may  that  not  impact  of  were  population the  consequently  legal  might size  that  the  possible  for  result to  be  limit.  the a  heavily  in  up  an  unfished  to  a  c u r r e n t minimum  on  population  entry  egg  estimated  the  Parameter  (1)  daily  of  agonistic  attempting  estimates  crabs  emphasized  by  describing  and  and t h o s e  and e x i t  biased  models  time,  a trap  which  samples  for  over  estimated.  the  escaping  trap  parameters  within  on e x p e r i m e n t s (2)  limit  effectiveness  simulating  and  while  reconsidered.  soak  between  most  suggested  and  production relative  does  the  fished  modeled  suggests  presumption  males  for  landings  which  size  steepest  populations.  minimum  males,  of  moulting  moulting,  the  slope  for  curves  suggests  calibration  bait  obtained traps  egg  after  catch  fished  current  for  s h o u l d be  differences  enter  the  The h i s t o r i c a l  size  the  analysis, large  was  a heavily  and  lowering  in population  population. legal  by  removing  population  in  analysis  negative  shallowest  mate  Thus,  in heavily  the  fisheries  and  and  mating  Yield-per-recruit  fished  regional  region  absent.  females,  landed,  Females  reduced  consequences of  being  region.  accompanied by a larger  from  heavily fished  not  into the  probabilities  of  to  were  and  out  above  two  crabs  of  Page  iii  traps.  Table of  Contents  Abstract  i i  List  of  Tables  vi  List  of  Figures  ix  Acknowledgments  xv  1 INTRODUCTION  1  2 DESCRIPTION OF STUDY AREAS  6  3 F I E L D METHODS  13  3.1  MORPHOMETRICS  13  3.2  BEAM TRAWL SAMPLING  15  3 .3  TRAP SAMPLING  16  3.4  FEMALE S I Z E - A T - M A T U R I T Y  16  3 .5 MATING PAIRS  17  3.6  TRAP DISTRIBUTION  17  3.7  TRAP PERFORMANCE EXPERIMENTS  18  3.7.1  TRAP TYPES  3.7.2  CATCH RATES OF TRAPS  3.7.3  ESCAPE OF CRABS FROM TRAPS  21  3.7.4  SOAK TIME EXPERIMENT  22  3.7.5  B A I T - E F F E C T I V E N E S S EXPERIMENT  23  3.8  20 IN GRIDS  -  21  MARK-RECOVERY PROGRAM  24  4 RESULTS  27  4.1  SPECIES COLLECTED  27  4.2  MORPHOMETRICS  27  4.3  FEMALE S I Z E - A T - M A T U R I T Y  28  4.4  MATING PAIRS  30  4.5  MOULT INCREMENTS  32 Page  iv  4 .6  GROWTH  36  4.7  TRAP PERFORMANCE EXPERIMENTS  43  4.7.1  CATCH RATES OF TRAPS  IN GRIDS  43  4.7.2  ESCAPE OF CRABS FROM TRAPS  44  4.7.3  SOAK TIME AND BAIT EFFECTS  50  4.8  TRAP DISTRIBUTION  68  4.9  COMMERCIAL EXPLOITATION OF MALES  70  4.10  MALE MATING A C T I V I T Y  78  4.11  SPATIAL  84  4.12  TAG RETENTION AND TAG INDUCED MORTALITY  95  4.13  FISHING AND NATURAL MORTALITY OF MALES  96  4.14  FISHING  AND TEMPORAL DISTRIBUTIONS  INTENSITY  AND FEMALE CATCH CURVES  IN SELECTED FISHERIES 5 Y I E L D - AND EGGS - PER-RECRUIT  .107 MODEL  Ill  5.1  DEVELOPMENT  Ill  5.2  RESULTS  117  6 DISCUSSION  123  6.1  TRAP PERFORMANCE EXPERIMENTS  123  6.2  SPATIAL AND TEMPORAL DISTRIBUTIONS  128  6.3  GROWTH AND MORTALITY  131  6.4  Y I E L D - AND EGGS-PER-RECRUIT  137  6.5  SUMMARY  148  7 LITERATURE CITED  153  Page  v  L i s t of T a b l e s Table  4.5.1. L i n e a r r e g r e s s i o n models f o r male C . m a g i s t e r moult i n c r e m e n t s - a t - s i z e f o r f o u r d a t a s e t s c o l l e c t e d from B r i t i s h C o l u m b i a ( B . C . ) and C a l i f o r n i a ( C a l . ) . 33  Table  4.5.2. Linear regression models for female C . magi s t e r moult i n c r e m e n t s - a t - s i z e f o r t h r e e d a t a s e t s c o l l e c t e d from B r i t i s h C o l u m b i a ( B . C . ) and C a l i f o r n i a ( C a l . ) . 33  Table  4.6.1. Mean and s t a n d a r d d e v i a t i o n s ( S D , s d ) f o r c a r a p a c e w i d t h s d e f i n i n g i n s t a r s o f male C . m a g i s t e r >80 mm CW. 40  Table  4.6.2. Mean and s t a n d a r d d e v i a t i o n s ( S D , s d ) f o r c a r a p a c e w i d t h s d e f i n i n g i n s t a r s o f f e m a l e C . m a g i s t e r >80 mm CW. 40  Table  4.6.3. The r e l a t i v e p r o p o r t i o n s of male C . magi s t e r >80 mm CW w i t h i n c o n s e c u t i v e instars for a time series o f beam trawl samples. The v a l u e f o r e a c h d a t e i n c l u d e s a l l males c a p t u r e d w i t h i n two weeks o f t h a t d a t e . The d o m i n a n t i n s t a r i s h i g h l i g h t e d by an a s t e r i s k . 41  Table  4.6.4. The relative proportions of female C . magister >80 mm CW w i t h i n c o n s e c u t i v e i n s t a r s f o r a t i m e s e r i e s of beam t r a w l s a m p l e s . The v a l u e f o r e a c h d a t e includes a l l females captured within two weeks of that date. The dominant i n s t a r i s h i g h l i g h t e d by an a s t e r i s k . 42  Table  4.7.1.1. Comparison of the mean number of C . magister c a u g h t p e r t r a p f o r 16 p e r i m e t e r v e r s u s n i n e i n t e r i o r t r a p s i n two 5 b y 5 g r i d s , and b e t w e e n a l l t r a p s i n e a c h g r i d . 43  Table  4.7.2.1. The r e l a t i v e r e t e n t i o n o f c r a b s <155 mm CW, f o r T r a p s C - D , and c r a b s <145 mm CW, f o r T r a p B , r e l a t i v e to Trap A . The r e l a t i v e retention for a t r a p type is the number o f c r a b s c a u g h t b y t h a t t r a p t y p e d i v i d e d by t h e number c a u g h t by T r a p A a f t e r e q u i v a l e n t one day soaks . F o r T r a p A n = 536 for c r a b s <155 mm CW, and n = 322 for crabs <145 mm CW. 47  Table  4.7.2.2. The probabilities of r e t a i n e d b y T r a p s A - D f o r 24 h .  male  C . magi s t e r  being 47  Page  vi  Table  4.7.3.1. Comparison of different models explaining d e n s i t i e s and s i z e f r e q u e n c y d i s t r i b u t i o n s o f C . m a g i s t e r i n s e t s of t r a p s w h i c h e x p e r i e n c e d d i f f e r e n t soak t i m e s and b a i t ages d u r i n g e q u i v a l e n t experiments i n 1985 and 1986. The o b j e c t i v e f u n c t i o n ( A ) i s t h e s e p a r a t i o n s t a t i s t i c of Schnute and F o u r n i e r ( 1 9 8 0 ) . P i s the number of p a r a m e t e r s in the model. AIC ( s e e t e x t ) measures model performance, the lower the v a l u e t h e more s u i t a b l e t h e m o d e l . 57  Table  4.10.1. The p e r c e n t of male C . magi s t e r , tagged when soft-shelled, w h i c h were h a r d - s h e l l e d when r e c o v e r e d . The r e s u l t s a r e r e p o r t e d f o r 30 day i n t e r v a l s o f t i m e - a t - l a r g e . The c a r a p a c e w i d t h s o f r e c o v e r e d males were a p p r o x i m a t e l y normally distributed ( 1 5 3 . 4 ± 6 . 0 mm) and ranged from 135-173 mm. 80  Table  4.11.1. Abundance o f female C . magi s t e r >145 mm c o m m e r c i a l t r a p s i n May a n d J u n e o f 1985 and 1986 .  CW  in 88  Table  4.11.2. D e n s i t i e s o f two t o t h r e e C . m a g i s t e r f r o m beam t r a w l s a m p l e s  year near  o l d ( * 7 5 - 1 4 5 mm CW) Indian I s l a n d . 88  Table  4.11.3. Summary of tag recoveries, by location, of sublegaland l e g a l - s i z e d male C . magister between April 1985 and August 1986. The number of trap hauls was d e t e r m i n e d by interviewing fishermen. Only records from f i s h e r m e n whose e f f o r t was known a r e r e p o r t e d . E x c e p t where n o t e d , r e c o v e r i e s were from w i t h i n t h e s t u d y a r e a as d e f i n e d i n F i g . 2.1 (page 9 ) . .89  Table  4.11.4. Summary o f t a g r e c o v e r i e s , by l o c a t i o n , of female C . magi s t e r between A p r i l 1985 and A u g u s t 1986. The number of trap hauls was d e t e r m i n e d by interviewing fishermen. Only r e c o r d s from f i s h e r m e n whose e f f o r t was known are reported. A l l r e c o v e r i e s were from w i t h i n t h e s t u d y a r e a as d e f i n e d i n F i g . 2.1 (page 9 ) . 90  Table  4.13.1. Statistics of the linear relationship in Fig. 4.13.1 from which the annual instantaneous rate of disappearance of sublegal-sized (145-155 mm CW) male C . magi s t e r was e s t i m a t e d . The r e l a t i o n s h i p h a s t h e form Y = a+b-X; where Y is the l o g a r i t h m of the number of r e c o v e r i e s w i t h i n c o n s e c u t i v e one month i n t e r v a l s , a n d X i s the t i m e - a t - l a r g e i n d a y s . 97  Page  vii  Table  4.13.2. Statistics of the q u a d r a t i c r e l a t i o n s h i p i n F i g . 4 . 1 3 . 1 w h i c h s u g g e s t s t h e m o r t a l i t y r a t e may i n c r e a s e as t h e time-at - large for sublegal-sized ( 1 4 5 - 1 5 5 mm CW) male C . magi s t e r increases. The relationship has the form Y = a + b - X + c - X ; where Y i s the l o g a r i t h m of t h e number of r e c o v e r i e s w i t h i n c o n s e c u t i v e one month i n t e r v a l s , and X i s the t i m e - a t - l a r g e i n d a y s . 97 2  Table  4.13.3. Statistics of the linear relationship in Fig. 4.13.2 from which the annual instantaneous rate of disappearance (Z) of legal-sized male C . magi s t e r was estimated. The r e l a t i o n s h i p has t h e form Y = a + b - X ; where Y is the logarithm of the number of recoveries within c o n s e c u t i v e 15 day i n t e r v a l s , and X i s the t i m e - a t - l a r g e i n days . 98  Table  4.13.4. Statistics of the linear relationship in Fig. 4.13.4 estimating the mean time-at - large for recovered tagged sublegal-sized male C . magi s t e r . The relationship has t h e form Y = a + b - X ; where Y i s the t i m e t o r e c o v e r y ( i n d a y s ) , and X i s the p r e - m o u l t carapace w i d t h . 99  Table  4.13.5. Summary o f s u r v i v o r s h i p to legal size of C. magister which were tagged when sublegal size, recovered when legal size, for 5 mm intervals 125-155 mm CW.  male and from 102  Table  4.14.1. C o m p a r i s o n s among d i f f e r e n t measures of fishing e f f o r t , and f i s h i n g i m p a c t , on male* C . m a g i s t e r populations i n f o u r r e g i o n a l f i s h e r i e s d e f i n e d by S t a t i s t i c a l A r e a ( S A ) . The statistical areas do not differ markedly in area. Annual s t a t i s t i c s i n c l u d e the m e t r i c tonnes landed ( t ) and t h e number of days f i s h i n g ( D F ) . 109  Table  5.1.1. The mean a n d s t a n d a r d d e v i a t i o n (mm) o f n o r m a l l y d i s t r i b u t e d male a n d f e m a l e C . m a g i s t e r i n s t a r s f o r t h e age and t i m e o f y e a r when t h e y a r e n e a r l y f u l l y f o r m e d . Males become s e x u a l l y a c t i v e i n t h e 155.0 mm i n s t a r . 112  Page  viii  L i s t of F i g u r e s Figure 2.1. Map of the main s t u d y a r e a near Tofino, British Columbia. The s t i p p l e d a r e a s a r e i n t e r t i d a l m u d f l a t s . The dashed l i n e s d e l i m i t t h e main s t u d y a r e a . Selected sites a r e r e f e r e n c e d by c a p i t a l l e t t e r s . The a r r o w i n d i c a t e s the main channel out to sea. Insert I locates the Dixon Entrance fishery (a). Insert II locates the main study a r e a , the Holberg I n l e t fishery (a), and t h e F r a s e r delta fishery (b). 9 Figure 2.2. landed  Time s e r i e s of the annual tonnage i n t h e S t a t i s t i c a l A r e a 1, 24 and 29  of C . magi s t e r fisheries. 10  Figure 2.3. Time s e r i e s o f t h e a n n u a l number of days C . magi s t e r i n t h e S t a t i s t i c a l A r e a 1, 24 and 29  f i s h i n g for fisheries. 11  Figure 2.4. Time s e r i e s of t h e a n n u a l number o f v e s s e l s w h i c h r e p o r t e d l a n d i n g s o f C . m a g i s t e r from t h e S t a t i s t i c a l A r e a 24 f i s h e r y n e a r T o f i n o , B . C . 12 Figure 3.7.1. Layout of trap g r i d s designed to emphasize the effects of different soak times (A), changes in bait e f f e c t i v e n e s s ( B ) , and t r a p s e l e c t i v i t y ( C ) , on t h e d e n s i t y and s i z e f r e q u e n c y d i s t r i b u t i o n o f C . magi s t e r . F o r ( A ) and ( B ) soak t i m e ( i n d a y s ) i s e n c i r c l e d , f o r ( C ) t r a p t y p e is encircled. 19 Figure 4.3.1. function  The p e r c e n t o f f e m a l e of carapace w i d t h .  C . magister  i n s e m i n a t e d as  a  29 Figure 4.4.1. C a r a p a c e w i d t h s o f C . magi s t e r m a t i n g p a i r s . The lines (Eqns. 4.4.1 and 2) d e f i n e the apparent l i m i t s in carapace widths r e q u i r e d for a mating embrace. Circles r e p r e s e n t d a t a from B u t l e r ( u n p u b . d a t a ) , s q u a r e s r e p r e s e n t d a t a from t h i s s t u d y . 31 Figure 4.5.1. Male C . magi s t e r m o u l t i n c r e m e n t s as a f u n c t i o n of pre-moult carapace w i d t h . The p l o t u s e s d a t a from B r i t i s h Columbia and California. Data from this study are r e p r e s e n t e d by s q u a r e s . 34  Page  ix  Figure 4.5.2. Female C . magi s t e r moult i n c r e m e n t s as a f u n c t i o n of pre-moult carapace width. The p l o t uses data from B r i t i s h C o l u m b i a and C a l i f o r n i a . D a t a from t h i s study are r e p r e s e n t e d by s q u a r e s . 35 Figure 4.6.1. Size frequency distributions for all f e m a l e C . magi s t e r c o l l e c t e d i n beam t r a w l s a m p l e s 1985 u n t i l September 1 9 8 6 .  male and from June 37  Figure 4 . 7 . 2 . 1 . A f o r 24 h ,  The p e r c e n t of male C . magi s t e r r e t a i n e d by as a f u n c t i o n of c a r a p a c e w i d t h .  Trap 48  Figure 4.7.2.2. Size frequency distributions of C . magister c a u g h t i n T r a p s A - D . Female c a r a p a c e w i d t h s a r e expressed as male-equivalent carapace widths for the same body lengths. 49 Figure 4 . 7 . 3 . 1 . Comparison of size frequency d i s t r i b u t i o n s of C . magi s t e r i n t r a p s s o a k e d 24 h i n t h e soak t i m e ( S T , 20 t r a p s ) and b a i t e f f e c t i v e n e s s ( B E , 16 t r a p s ) e x p e r i m e n t s i n 1985 a n d 1986. Female carapace w i d t h s are expressed as m a l e - e q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same b o d y l e n g t h s . 61 Figure 4.7.3.2. S i z e f r e q u e n c y d i s t r i b u t i o n s of C . m a g i s t e r f o r s e t s of 20 t y p e A traps with different soak times from equivalent experiments in 1985 and 1986. Solid circles p r o f i l e p r e d i c t e d s i z e f r e q u e n c y d i s t r i b u t i o n s u s i n g Model '4' (Table 4 . 7 . 3 . 1 ) . Female c a r a p a c e w i d t h s a r e expressed as male-equivalent carapace widths for the same body lengths. 62 Figure 4.7.3.3. The r e l a t i v e rate at w h i c h C . magi s t e r enter T r a p A , as a f u n c t i o n of t h e r a t i o between t h e w e i g h t of crabs i n a t r a p , and the weight of the c r a b a t t e m p t i n g to enter the t r a p . T h i s p l o t uses the best parameter e s t i m a t e s f o r E q n . 4 . 7 . 3 . 3 f r o m Model ' 4 ' ( T a b l e 4 . 7 . 3 . 1 ) . 63 Figure 4.7.3.4. The r e l a t i v e e n t r y r a t e of C . magi s t e r i n t o T r a p A as a f u n c t i o n of bait age. This plot uses the best p a r a m e t e r e s t i m a t e s f o r E q n . 4 . 7 . 3 . 5 from Model '4' (Table 4.7.3.1). 64  Page  x  Figure 4.7.3.5. Response s u r f a c e o f t h e p r e d i c t e d changes i n t h e s i z e f r e q u e n c y d i s t r i b u t i o n o f C . magi s t e r w i t h i n 20 t y p e A t r a p s , as a f u n c t i o n of t i m e . These r e s u l t s use t h e best p a r a m e t e r e s t i m a t e s f o r Eqns . 4 . 7 . 3 . 3 and 5 from Model '4' (Table 4 . 7 . 3 . 1 ) . Female c a r a p a c e w i d t h s are expressed as m a l e - e q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same body l e n g t h s . 65 Figure 4.7.3.6. Response s u r f a c e o f t h e p r e d i c t e d s i z e f r e q u e n c y d i s t r i b u t i o n s of C . magi s t e r w i t h i n 10 s e t s of 16 t y p e A traps . E a c h s e t u s e d b a i t r a n g i n g i n age from z e r o t o e i g h t days, s o a k e d f o r one d a y . The b a i t was removed f o r the n i n t h d a y . The v e r t i c a l l i n e s show the o b s e r v e d d a t a f o r a p a r t i c u l a r c o m b i n a t i o n of b a i t age and c a r a p a c e w i d t h , f o r differences greater than one. These r e s u l t s use t h e best p a r a m e t e r e s t i m a t e s f o r E q n s . 4 . 7 . 3 . 3 and 5 from Model '4' (Table 4 . 7 . 3 . 1 ) . Female c a r a p a c e w i d t h s are expressed as male - e q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same body l e n g t h s . 66 Figure 4 . 7 . 3 . 7 . The p e r c e n t of soft-shelled legal-sized male C . magi s t e r i n T r a p A , as a f u n c t i o n of soak t i m e . These results were obtained from the soak time experiment p e r f o r m e d near I n d i a n I s l a n d ( H ; F i g . 2 . 1 , page 9) i n 1986. Above t h e S.D. bars is the number of legal-sized males c a u g h t i n 20 t r a p s . 67 Figure 4.8.1. ( A ) Time s e r i e s c o m p a r i s o n o f t h e number o f t r a p buoys c o u n t e d i n Lemmens I n l e t , and t h e number of traps e s t i m a t e d by i n t e r v i e w i n g f i s h e r m e n . ( B ) Time s e r i e s o f t h e number of t r a p s e s t i m a t e d by i n t e r v i e w i n g f i s h e r m e n . The ' E l s e w h e r e ' c a t e g o r y i n c l u d e s t r a p s f i s h e d o u t s i d e the study a r e a i n S t a t i s t i c a l A r e a 24 by f i s h e r m e n who a l s o f i s h i n the study a r e a . The c a p i t a l l e t t e r s i n p a r e n t h e s e s identify t h e s e a r e a s i n F i g . 2.1 ( p a g e 9 ) . 69 Figure 4.9.1. D i a g r a m e x p l a i n i n g how t h e d e g r e e of male C . magi s t e r in the 155.0111.2 estimated. The proportion exploited d e t e r m i n e d by s i z e f r e q u e n c y a n a l y s i s .  of exploitation mm i n s t a r was (A-s-[A + B ] ) was 73  Figure 4.9.2. The percent of legal-sized male C . magister removed from t h e 1 5 5 . 0 mm i n s t a r by f i s h i n g , as d e t e r m i n e d by s i z e f r e q u e n c y a n a l y s i s o f t r a p s a m p l e s . The e n c i r c l e d d a t a p o i n t s a r e f o r upper Lemmens I n l e t . The r e m a i n d e r a r e f o r t h e r e s t of t h e s t u d y a r e a . 74  Page  xi  Figure 4.9.3. L i n e a r r e g r e s s i o n of v i r t u a l e n t r y r a t e s of male C . magi s t e r 145-155 mm CW i n t o t r a p s over t i m e . D a t a from upper Lemmens I n l e t , a poor c r a b h a b i t a t , a r e n o t i n c l u d e d in t h i s p l o t . 75 Figure 4.9.4. Time series of commercial catch rates legal-sized male C. magister. The capital letters p a r e n t h e s e s i d e n t i f y t h e s e a r e a s i n F i g . 2.1 (page 9 ) .  of in 76  Figure 4.9.5. Virtual entry rates C . magi s t e r i n t o t r a p s o v e r t i m e . I n l e t , a p o o r c r a b h a b i t a t , a r e not  of legal-sized male D a t a from u p p e r Lemmens included in t h i s p l o t . 77  F i g u r e 4 . 1 0 . 1 . The p e r c e n t o f male C . magi s t e r w i t h m a t i n g marks ( B u t l e r 1960) as a f u n c t i o n o f c a r a p a c e w i d t h . The minimum l e g a l s i z e l i m i t i s « 1 5 4 mm CW. 81 Figure 4.10.2. Time series of the percent of hard-shelled l e g a l - s i z e d (>154 mm CW) m a l e , l e g a l - s i z e d male w i t h m a t i n g marks ( B u t l e r 1 9 6 0 ) , and s u b l e g a l - s i z e d ( 1 4 0 - 1 5 4 mm CW) male C . magi s t e r with mating marks. E x c e p t where noted, all sample s i z e s a r e >100 c r a b s . 82 Figure 4.10.3. Time s e r i e s i n d i c a t i n g t h a t t h e r e l a t i v e l e v e l o f m a t i n g a c t i v i t y by l e g a l - s i z e d male C . magi s t e r i n 1986 was »29% o f t h e l e v e l i n 1985. The s u b l e g a l : l e g a l m a t i n g r a t i o is o b t a i n e d by d i v i d i n g t h e p e r c e n t of legal-sized males w i t h m a t i n g marks by t h e p e r c e n t of sublegal-sized males with mating marks. The r a t i o f o r May 1986 was e x c l u d e d from the c o m p a r i s o n for r e a s o n s g i v e n i n the t e x t . 83 Figure 4.11.1. Time series of densities for one year old ( « 4 0 - 7 5 mm CW) male and f e m a l e C . magi s t e r i n t h e entrance t o Lemmens I n l e t ( A ) , and on t h e s h a l l o w s a n d b o t t o m o f an exposed shore ( B ) . Time s e r i e s o f d e n s i t i e s o f two t o t h r e e y e a r o l d ( « = 7 5 - 1 4 5 mm CW) male a n d f e m a l e C . m a g i s t e r i n t h e main channel out to sea (C). The capital letters in p a r e n t h e s e s i d e n t i f y t h e s e a r e a s i n F i g . 2.1 (page 9 ) . 91 Figure 4.11.2. Time s e r i e s o f d e n s i t i e s f o r two t o t h r e e year o l d ( * 7 5 - 1 4 5 mm CW) male a n d f e m a l e C . m a g i s t e r i n Lemmens Inlet. The c a p i t a l letters in parentheses identify these a r e a s i n F i g . 2.1 ( p a g e 9 ) . 92  Page  xii  Figure 4.11.3. Time series comparison of two indices of abundance f o r f e m a l e C . magi s t e r ( >145 mm CW) i n t h e studyarea, b u t e x c l u d i n g Lemmens I n l e t , Browning P a s s a g e , and near I n d i a n I s l a n d , where female d e n s i t i e s were generally low ( T a b l e 4 . 1 1 . 1 ) . ' V i r t u a l e n t r y r a t e s ' were e s t i m a t e d as in Section 4.9. 93 Figure 4.11.4. F r e q u e n c y d i s t r i b u t i o n s of r a t e s f o r male and f e m a l e C . m a g i s t e r . a f t e r a mean of » 1 5 0 d a y s - a t - l a r g e .  mean d a i l y movement C r a b s were r e c o v e r e d 94  Figure 4.13.1. L i n e a r and q u a d r a t i c r e g r e s s i o n s of recoveries o v e r t i m e f o r t a g g e d male C . magi s t e r r e l e a s e d a n d r e c o v e r e d as sublegal-sized crabs 145-155 mm CW. Most tagging was done from M a y - J u l y 1 9 8 5 . The open c i r c l e s were n o t i n c l u d e d i n t h e r e g r e s s i o n a n a l y s e s b e c a u s e f i s h e r m e n were n o t w e l l p r e p a r e d for the m a r k - r e c o v e r y program at t h i s t i m e . 103 Figure 4.13.2. L i n e a r r e g r e s s i o n o f r e c o v e r i e s over t i m e f o r tagged male C . magi s t e r released and recovered l e g a l - s i z e d c r a b s , m o s t l y i n s p r i n g 1986.  341 as 104  Figure 4.13.3. ( A ) F r e q u e n c y d i s t r i b u t i o n of r e l e a s e dates of s u b l e g a l - s i z e d male C . m a g i s t e r . (B) Frequency d i s t r i b u t i o n of recovery dates for those crabs released in (A) and r e c o v e r e d as l e g a l - s i z e d c r a b s . 105 Figure 4.13.4. Linear regression of time-at - large for male C. magister. tagged and r e l e a s e d when s u b l e g a l size and r e c o v e r e d when l e g a l s i z e , on p r e - m o u l t c a r a p a c e w i d t h . 106 Figure 4.14.1. Comparison of catch curves (Ricker f e m a l e s from f o u r r e g i o n a l C . magi s t e r f i s h e r i e s S t a t i s t i c a l Area i n B r i t i s h Columbia.  1975) for d e f i n e d by 110  Figure 5.2.1. R e l a t i v e egg p r o d u c t i o n by C . m a g i s t e r p o p u l a t i o n s as a function of the F:M mating r a t i o , and f o r three e s t i m a t e s of M. T h e s e r e s u l t s a r e not n o t i c e a b l y sensitive t o t h e a n n u a l r a t e o f d e c r e a s e i n egg p r o d u c t i o n by f e m a l e s who f a i l t o mate and m o u l t i n p r e v i o u s y e a r s . 120 Figure 5.2.2, Yield-per-recruit mortality (F). The r e s u l t s  (YPR) f o r increasing are r e p o r t e d r e l a t i v e to  fishing F=<». 121  Page  xiii  Figure 5.2.3. Y i e l d - p e r - r e c r u i t i s r e p o r t e d r e l a t i v e t o 1.0 at 165 mm CW ( S - S ) . E g g s - p e r - r e c r u i t are r e p o r t e d r e l a t i v e to an u n f i s h e d p o p u l a t i o n . The b r e a d t h of t h e relationships indicate the range when the annual decrease in egg production by females that did not mate and moult in previous years is varied from 0.0-1.0 times the egg p r o d u c t i o n of the p r e v i o u s y e a r . Both n o t c h - t o - n o t c h (N-N) and s p i n e - t o - spine ( S - S ) carapace widths, and t h e current C a n a d i a n ( C ) and A m e r i c a n ( A ) l e g a l s i z e s , a r e n o t e d . 122  Page  xiv  ACKNOWLEDGMENTS This support  study of  Oceans,  Dr.  Pacific  extend  pursuit  of  Zoology, during  The  study,  skill  greatest which  work.  In  Barton, White  vessels  from  John F r a s e r , from  encounters  their  time  to  tagged c r a b s .  My r e s e a r c h of  encouragement  at  effective  Messrs.  and  is  for  for  the  and  Pacific enjoyable  Wolfgang C a r o l s f e l d , and  above  the  for  their  all,  student  safe  participation  successful  Messrs.  sample  time.  crabs  and  Department  staff  field  and  their  Messrs.  which  they  Messrs.  on  not but  Mike D a n i e l s ,  of  Ken B a r r ,  board  Danny B a r r ,  caught,  the  J a m i e Sloman  catch  Leigh Hilbert  of  completion  Danny B a r r ,  B a r r y Grumbach,  B a r r y Grumbach  for  skills.  essential  me -to;  I  and  uncertainty  the  Antan P h i l l i p s  particular,  legal-sized of  thank  appreciation  invited  opportunity  provided  technical  efficient,  John F r a s e r ,  and  B r i t i s h Columbia.  of  productive,  especially  was  Fisheries  opportunities.  Columbia,  the  a  of  and  them.  of  ensured  supervision  minimum  C . C . Lindsey  British  assuring  this  with  missed  Dwight H e r i t a g e ,  for  fishermen,  tags  Dr.  I a d m i r e and envy My  Peter  I  Nanaimo,  providing  few  and wisdom  program.  assistants  for  and I t h a n k  Station  Department  proceeded  of  initiative,  Station,  and  by  University  Wayne H a r l i n g ,  Joe  work  ends,  the  Jamieson,  him  headed  Biological  work.  to  the  dead  this  from  Biological  that  committee,  this  G l e n S,  my t h a n k s  ensuring  field  benefited  only  and their  Ken B a r r , retained  recorded Alex  all  Erickson,  Page  xv  John F r a s e r ,  B a r r y Grumbach,  Ralph T i e l m a n  and  measurements could  of  measure them  Seafood  Supply  tags  tagged  for  thank  later.  and f o r  helping with  to  use  for  retained other  Vancouver,  p u r c h a s e d by h i s  B.C.  providing this  to  unpublished data  he  Jamie  precise  crabs  returned  M r . Andre T u r p i n B.C.  collected  Sloman,  post-moult  legal-sized  fishermen  so  tags  I or  of  Tri-Star  and  returned  employer.  Department storage  work  grateful  Rae-Arthur,  provided  later.  M r . Doug S w i f t ,  am v e r y  or  Many  collection  Tofino,  I  crabs,  Limited,  from c r a b s  I  Leigh H i l b e r t  them  retained  Dave  of  space  i n other  Fisheries for  research  Oceans,  equipment  ways.  Mr. Terry H. Butler collected  and  for  permitting  i n Dixon E n t r a n c e d u r i n g  me the  1950's .  During from are  the their  Station,  this  study  I was  s u p p o r t e d by  C a n a d i a n Department property Nanaimo,  and  are  of  Fisheries  maintained  at  a graduate and the  Oceans. Pacific  scholarship All  data  Biological  B r i t i s h Columbia.  Page  xvi  1  INTRODUCTION The  Dungeness  commercially coast  of  than tip In  of  from A l a s k a  North  171  tenth  British  in)  males  and  are  rarely  to  central  In  carapace  the  females  retained  can  value the  1950's,  Additionally,  of  p e r c e i v e d problems to  an  «40% annual  fishermen  to  With the decline  to for  be  Section  1  has  exception  about  regional  landings  fisheries  is  tip  to  legally.  165 mm CW.  practice legal  policy,  of  Columbia little  females  size, and  (2)  (3)  the  ($5.15  Columbia  the  (Jamieson  valuable  million  only  landed  fisheries  and 1985,  have  east  British  i n the  core  1985). had  due  the  few  in part group  of  1986).  and as  1985,  or p a t t e r n s  no  since  1% o f  (Jamieson  intervention,  (Jamieson  in  most  represents  fishermen,  along  the  research attention  a precipitous,  trends  in  reaclv  one  in B r i t i s h  of  1970  from  retained  limit  but  few  is  been  attention  of  be  size  C . magister  turnover  no o u t s t a n d i n g  major  can  requiring scientific  lobby for  Islands  (CW), m e a s u r e d  C o l u m b i a C . magi s t e r  in C. magister  Charlotte  greater  only  males.  British  products  British  males  waters  spines,  fishery  in  there  sea  Pacific  conservation  p a r t l y because  landed value  the  retained,  poor  crab  yet  along  is  fisheries  i n 1986)  California  (1)  f a m i l i a r only with  invertebrate  fished  because  market  Dungeness  is  width  be  believe  The  Dana)  minimum l e g a l  fishermen is  it  magi s t e r  American  anterolateral  Columbia,  Both  (Cancer  America.  mm ( 6 . 7 5  the  crab  yet  coast 1986),  unexplained, of  there  landing  Columbia.  the  In  Queen appear  statistics contrast,  Page  1  C.  magi s t e r  landings  from C a l i f o r n i a ,  shown  coherent  cyclical  fluctuations  years  since  least  early  abundance  at  (Botsford  nonexistent  in  statistics  do not  Because high  value  American  crab  Several  due  cannibalism  of  Demory  is  of  9-10  apparently r e f l e c t i n g  male  not  a  periodicity  known  whether  fisheries,  or  predictable  1985,  fisheries  an  adults  cycles  the  cyclic  Warner  have  have  1985,  attracted  are  landing  been  and  egg-predator on  worm  juveniles  density-dependence  in  early  scientific  as  causes  reduced  (Wickhara  of  were female  1979),  and Wickham  history  and  1986),  recruitment  (1)  (Botsford life  Methot  proposed  included:  pattern  much  involving density-dependent  evaluated, to  with  abundance.  mechanisms  those  first  It  apparently  Dungeness  the  (3)  their  have  1950's,  Columbia  reflect  1985,  fecundity  and  British  of  cycles.  among  1986a).  (Barry  attention. these  the  O r e g o n , and W a s h i n g t o n  (2)  1978),  ( M c K e l v e y et  al.  1980 ) .  A predator-prey hypothesis, has et  been al.  1982,  1983 ) .  et  may have in  a l . 1986,  Section  1985),  Recent  possibly  1  as  an  also  research been  on  seems  is  of  crab  the  on  the  predator,  cycles  (Botsford  larvae  unlikely  focusing  as  to  the  (Botsford have  density-dependent  et  caused  hypothesis  c a u s e d by a c y c l i c a l p a t t e r n  conjunction with Botsford  fishermen  explanation  Salmon p r e d a t i o n  Thomas  cycles. cycles  rejected  with  that  in wind  processes  al . the the  stress, (Johnson  1986b).  Page  2  There the  have  minimum  estimates 1986).  legal  of  A  been  no  yield-  size  limit  of  as  explain  cyclic  pattern  parameters  are  the  logistic  exposed  to  a  evaluate  the  since  at  from  this  this  (1985)  on  early  size  study female  eggs-per-recruit the  current  a high  Gotshall  1965,  Tofino,  C.  because  magi s t e r .  Section  1  size  this  was  proposed  to  estimates  of  acquire  experiments  was  to  and  because  of  sampling  on  of  but  size egg  chosen  as  the  accessibility been  a  and  for  et  al .  yield-  and  for  crab  that  yield  1949,  this  well-bounded  traditional  Columbia  assumption  a high  site  CW  information  fecundity) the  in  documentation  With  (Cleaver  main  limit  from H a n k i n  provides  production  no  1985).  evaluate  limit  size  is  information  to  and  population  in B r i t i s h  there  and  vital  mm s p i n e - t o - s p i n e  in place  (Jamieson by  legal  165  the  movement  C . magi s t e r  survivorship,  B . C . was  T o f i n o has  moulting,  of  been  analyzed  estimate  minimum  limit  chosen  1986).  its  to  century,  Methot  of  models  difficult  closed  CW) has  growth,  level  the  (Methot  mortality  Accurate  study  (supplemented  were  of  and  of  reliable  available  landings.  current  minimum l e g a l  ensuring  study  was  most  because  been  growth  performing  relatively  mm n o t c h - t o - n o t c h  how  of  not  mortality,  The c u r r e n t  least  on  in  often  this  (»154  of  C. magister  analyses  coast.  growth,  for  magi s t e r .  of  of  of  reproduction  C.  limitation  purpose  statistics  order  a  problems  an u n b o u n d e d ,  The  for  information  acknowledged  the  eggs-per-recruit  g r o w t h and m o r t a l i t y have  lack  population  or  while  Poole  two  fishery  fishing  and  year for  region  Page  3  for  most  of  this  supplemented old  cohort  months  of  as  fishery.  the  it  By  information  males  the  on  entry  mark-recovery trap of  catches  Trap dynamics  (Caddy 1 9 7 9 ) .  by  interactions. retention  Section  1  and  into  on d a t a  by  of  were  and time,  To r e d u c e for  changes  fishing  size exit  and  trawl  samples,  instars  was  vessels.  of  a  sampling  by  interactions  entry  Experiments  were  also  different  biased  changes  experiments  the  from  The p r o p o r t i o n  data  crabs,  describing  of  by  estimated  effectiveness  model  growth,  gathered  determined  was  followed.  movement,  bait  A general  trawl  beam  in  for  beam  of  size  samples.  agonistic  models  the  included  frequency  such b i a s ,  18  entered  from  was  fishery  for  which  to  rates  year  distributions  analysis,  fishery  the  followed  obtained  the  regions  A two  males,  mortality,  from t r a p  provide  Tofino. was  larger  fishing  Catch  probabilities  types.  were  to  coastal  frequency  frequency  taken  entry over  case  size  on b o a r d c o m m e r c i a l  parameters  modified  and  instars  males  males  near  increments-at-size ,  natural of  the  females  smaller  generally  effectiveness  trap  of  analysis  of  estimate  moult  other  C . magi s t e r  in  size  program.  legal-sized  frequency  and  applying on  Information  and  temporal  in  collected  female  matured,  transition  and  and  Spatial,  samples.  Sampling  information  male  sublegal-sized  the  century.  dynamic  of  the  in  bait  among  crabs  were p e r f o r m e d  to  and e x i t  as  and  performed  sizes  by  crabs  rates  agonistic  to  measure  by  different  interactions  between  Page  4  crabs  and  experiments  traps  constructed  from  the  results  of  to help s t a n d a r d i z e data obtained from d i f f e r e n t  types and a f t e r  Section 1  was  different  soak  these trap  times.  Page 5  2 DESCRIPTION OF STUDY AREAS Most  field  S a m p l i n g was in F i g . water  l i m i t e d to  2 . 1 , and  and  Statistical  weight  of  C . magi s t e r  1986,  respectively.  this  study  exploited  area  only  areas  to  the  study  substrate  at  or  may  near  detected  the  fishery  in  (stippled  this  area,  settled  this  Fig. and  Canadian  most  shallow sand  Lemmens  18° C i n  surface  the be  2.1) w h i c h  due  provide crabs  the  of  larval of  the high  inland  to  more  a  was  and  exposed  Annual  surface  but  summer  upper  Lemmens  settlement productive  extensive quality  (Armstrong  of  crab  (a=5-15 m d e p t h )  waters  to  1985 and  switched  in  in  total  fishery  *6-12° C ,  tradition  within  the  in  The  the  fishery  waters  Inlet .  A l t h o u g h no  first-year  in  fishing.  from  lines  Department  the  Columbia  salmon  from  are  13 and 20% o f  fishermen  of  may  of  habitat.  ranges  study,  the  some  varies  Island.  region  by  occurs  are  dashed  sites  for  crab  area  head  reach  Indian  during  poor  although  temperature  temperatures  newly  to  by the  These  British  fishing  a summer o f  of  mud  seawater  Inlet  due  The  in  No c r a b  after  mixed.  24 a c c o u n t e d  B r i t i s h Columbia.  B r o w n i n g P a s s a g e and  support  landed  year-round,  The w a t e r s well  Area  Inlet,  defined  and  Tofino,  enclosed  Island.  2 4 , as  Oceans,  SA 2 4 .  fishing  those waters  Indian  (SA)  Area  Fisheries  p e r f o r m e d near  i n c l u d e d Lemmens  surrounding  Statistical of  work was  crab  mudflats  habitat  and  was  for  Gunderson  1985).  Section  2  Page 6  Information in  this  in  shoal  study.  Insert in  north  'a')  1985  Island  (SA 29) and  2.2  in  1985  Vancouver  for  Holberg  fishery  exceeded  Time effort for  the  or  would  SA 29  indicate  statistics trends  Section  in  2  a  over the  1986.  trend  trends  linear time.  'b')  and  1986,  trends  Inlet seldom (in  see  and  in  landing  in  the  or  Similarly, effort  respectively.  the  statistics  In  the  5 t,  and  landing  and  to  test  analysis  (an  Noakes  1986)  1987)  statistics effort  were for  in no the  using  found  no  for  the  statistics  A significant  decrease  there  effort,  fishery  McLeod  fishery.  for  1971).  l a n d i n g and  delta)  of  fishery  accounted  intervention  (Hipel the  <1%  for  exceeded  Inlet  intervention,  Vancouver  fishery.  Holberg  series  of  i n c a t c h and  on  the  fishery  delta  II,  performed  increase  l a n d i n g and  1985  end  2.1,  landings  Inlet  Fraser  o n l y once  were  Time  Fraser  in  landings  but  or  Insert  (Fig.  reported  accounted  The  included  concentrated  Islands  northern and  is  is  Holberg  Holberg  fishing  all  fishery, (the  and  the  algorithm  (a=.05)  (Tofino)  the  for  the 'a')  annual  time.  McLeod-Hipel  SA 24 for  over linear  significant  but  days  The  2.1,  (SA 1 )  and 16% of  14  historical  analyses  statistics  ARMA(1,0)  all  200  series  trends  fisheries  Charlotte  II,  landings  and 3 d e s c r i b e  Inlet  for  (Fig.  reported  respectively,  effort  Queen  near  Insert  landings  23% o f  Figures  the  fishery  2.1,  near  regional  respectively.  small  (Fig.  reported  of  1986,  a  other  and a c c o u n t e d  and is  three  The D i x o n E n t r a n c e f i s h e r y  water  I,  (SA 27)  30  from  the  trend landing  significant SA 1  (Dixon  Page  7  Entrance) process  fishery.  with  and 9 y e a r s , The  since a  in  high  fewer (as  the  of  linear recent  of  experienced  2.4,  the  vessels the  which  study  and  of  area, of  as  2  traps  fishermen Two of  reporting years.  1986  fishing  are  activities. the  265  t  at  ARMA(9,0) lags  (p<.05  1965) has  is  of  Also,  fished  the  more  As  Thirty known  to  due  to are  study).  established  traps.  landings  from  evident  in  from  SA 24  (30)  of  have  Fig.  vessels  l a n d e d from SA 24  in  has  the  59  fished  in  landing s t a t i s t i c s 30  an  fisherman  this  *800  for  there  per  during  landings  These  1  misleading  decreased  reported  respectively.  in  only  SA 24  fished  vessels  recent  an  1985).  d e t e r m i n e d by matching  a p p r o x i m a t e l y 80% o f  Section  1986,  crabs  in  by  negative.  in  effort  a n d one  59  fishermen  landed  of  traps  in  of  traps.  and  dramatically  my knowledge for  1985  number  increased  (27)  effort  fewer  interviews  «=200-300  lag being  (Jamieson  and  50-150  terms  beginning  fishermen  fished  fished  during  in  quality  fishermen  Twenty-seven SA 24  the  from  described  9 year  increase  years  fishermen  the  intervention  turnover  fishermen  the  be  autocorrelation  term for  determined  Most  could  significant  extent  ARMA(0,1)  Both  with  accounted 1986.  Page  8  Figure 2.1. Map of the main study area near T o f i n o , B r i t i s h Columbia. The stippled areas are intertidal mudflats. The dashed l i n e s d e l i m i t the main study a r e a . S e l e c t e d s i t e s are r e f e r e n c e d by c a p i t a l letters. The arrow i n d i c a t e s the main channel out to s e a . Insert I l o c a t e s the Dixon Entrance f i s h e r y (a). Insert II l o c a t e s the main study a r e a , the Holberg I n l e t f i s h e r y ( a ) , and the F r a s e r d e l t a f i s h e r y ( b ) .  Figure  2.1  Page 9  1950  I 9 6 0  1970  1 9 8 0  1 9 9 0  YEAR  Figure C. magister fisheries.  Figure  2.2  2.2. Time landed in  series of the the Statistical  annual Area 1,  tonnage 24 and  Page  of 29  10  1950  I 9 6 0  1970  1 9 8 0  1 9 9 0  YEAR  Figure fishing for f i s h e r ies .  Figure  2.3  2.3. Time C. magister  series of the annual number of days i n the Statistical A r e a 1, 24 and 29  Page  11  6 0 - i  4 0  H  2 0  H  0 1965  1970  1975  1980  1985  1990  YEAR  Figure 2.4. Time s e r i e s o f t h e w h i c h r e p o r t e d l a n d i n g s o f C . magi s t e r 24 f i s h e r y n e a r T o f i n o , B . C .  Figure  2.4  a n n u a l number o f vessels from t h e S t a t i s t i c a l A r e a  Page  12  3 FIELD  METHODS  In for  order  to evaluate the current  C. magi s t e r ,  followed  over  a cohort  time  rates,  spatial,  were  research  by  capabilities, interactions  sizes  determined  vessels,  standardized  these  and  and  and  between  processes.  males  sampling  in  bait  limit was  and were  success, e x p l o i t a t i o n distributions,  females  on board  in  mating  commercial  trap  f o r the e f f e c t s  samples  of t r a p  and were  retention  effectiveness,  and  on experiments  which  c r a b s , based  Moult  the f i s h e r y  and  The  size  and females  frequency  trawling.  correcting  changes  of  from  fishing  size  legal  males  entered  Commercial  temporal  size-at-maturity, embraces  of p r e - r e c r u i t  as the males  subsequently e x p l o i t e d .  minimum  agonistic analyzed  i n c r e m e n t s - a t - s i z e , l e n g t h of i n t e r m o u l t  p e r i o d s , m o r t a l i t y , movement, and r e c r u i t m e n t t o the f i s h e r y were o b t a i n e d from a mark-recovery 3.1  MORPHOMETRICS  The (CW)  program.  standard measure  measured  anterolateral  between spines  of C . magi s t e r  the notches  just  (notch-to-notch).  size  i s carapace  anterior Except  width  t o the t e n t h where  noted,  carapace width r e f e r s to the n o t c h - t o - n o t c h measurement t r u n c a t e d to  the  required  nearest  millimeter.  relationships  Trap  t o convert  standardization  notch-to-notch carapace  to body l e n g t h f o r both males and females. determine  Section 3  experiments width  A l l crabs measured to  these r e l a t i o n s h i p s were obtained near  Tofino.  Page 13  Because the  tips  some  earlier  work  of  the  tenth  relationship  was  established  width  to  the  range  of  spine  carapace  width  by  least  one  anterolateral  equivalent  male  and  w i d t h was  fishermen CW).  Both  c r a b of  sex  carapace  Some length, to  order width  to  were  from  carapace for  C . magi s t e r  of  legal  size  was  this  length  for  establish body  can  be  100-190 and  a  legally  154 mm  particular  taken  determined  measured of  3.1  the  and  females  were  a r e l a t i o n s h i p between for  taken  from  required  notch-to-notch  from  the  joint  carapace  widths  Twenty-five  for  males the  a  measure  males each  and  abdominal  of  the  range.  body  carapace  width  established.  females,  six  from  respectively.  rostrum to  (25)  of  notch-to-notch  1 mm i n t e r v a l  and f e m a l e s ,  tip  also  by  notch-to-notch  converting notch-to-notch  males  length  were  study  at  respectively.  male  in  full  Spine-to-  obtained  152-156 mm CW ( n o t c h - t o - n o t c h ) .  120-175 mm CW, f o r  Section  the  notch-to-notch  measurements  a  relationships  and  extension  for  observed.  n o t c h - t o - n o t c h and s p i n e - t o - spine  analyses  measurements  was  from  a  carapace  m e a s u r e d w i t h i n e a c h 1 mm i n t e r v a l w i t h i n t h i s  so  body  being  of  crabs  c r a b s were  measurement  165 mm CW ( s p i n e - t o - s p i n e ,  width  100  which  between  spine-to-spine  widths  and f e m a l e s ,  width  ( s p i n e - t o - s p i n e ),  i n e a c h 1 mm i n t e r v a l  p r o b a b i l i t y of  distribution for  at  is  The  carapace  regression.  size  convert  determined  100-170 mm CW, f o r m a l e s  The  to  carapace  spines  notch-to-notch  female  each  measured  the  In  carapace pairs  of  120-185  and  Body  most  length  posterior  segments.  Page  14  3.2  BEAM TRAWL SAMPLING  Spatial,  temporal  sublegal-sized primarily  et  al .  distance  beginning  tows  end  towed  were  of  beam  During throughout abundant,  and  crabs  results  the  width  exoskeleton  3.2  by  by  estimating  the  the  spatial  by  Most  dividing  beam  trawl .  should  be  distribution  where  crabs  were  intervals  from  tow d e p t h , of  trawling  bottom  specific  were  hardness, 1960),  A c r a b was  thumb and i n d e x  the  densities  sites  (Butler  legs  m.  type,  trawls  and  4.11.  shell  claws  measured. its  assessed  Details  sex,  2.3  abundance.  The d a t e ,  beam  is  by  at  estimated  approximately monthly  in Section  described  photographs.  swept  selected  recorded.  of  area  obtained  width  then  efficient,  tows  1986.  male  were  as  mostly  landmarks  aerial  absolute  In  at  captured  was  of  area. made  the  100%  «60  F o r C . magi s t e r ,  a p p l i e d by t h e  Section  not  1985  are given  on  by  swept  min,  of  were  was  ranging  5-10  densities  indices  were  marks  of  by  resolution  Crab  September  crabs  mating  carapace  tow  are  design  effective  determined a  study  swept  species.  if  the  until  All  of  summer  The  distributions  C . magi s t e r  The t r a w l  caught  trawls  frequency  female  high  tows were  area  their  of  from  i n t e r p r e t e d o n l y as  mid-1985  was  200-500 m.  number  Because  and  ( 1985 ).  towed  and  distance  the  male  by beam t r a w l i n g .  Gunderson The  and s i z e  could  identified  and were  considered  resist  the  to  presence  noted;  and  hard-shelled  moderate  pressure  finger.  Page  15  3.3  TRAP SAMPLING  Size from  frequency  commercial  traps  commercial  fishing  from  1985  of  April  four  were  assess  the  from  fishing traps  the  were  given  Commercial  fishery The  duration  of  of  was  date,  type,  October  and b a i t  open All  times  These  traps  helped  were  absent  to  commercial  crabs  captured  in  and  data lacked  often  and a s s e s s e d as  sampling  C . magi s t e r between  sampled  total  trap  study.  invitation  which  Research  was  of  intervals  the  traps,  which  catch  in  Section  3.2.  locations  are  4.9.  Entrance  in  this  species  the  in  unpub. of  1984  number o f type,  catches 1983  December  fishery  (G.S. Jamieson,  sampled  to  fishery  the  vessels.  period. crabs  C . magi s t e r  monthly  I accepted  'research'  smaller  female  sampling  board their  time  The  fisheries  Dixon  1984  of  identified  in Section  same  and  by  1986.  on  traps.  details  regional  the  male  approximately  fishing  abundance  for  Specific  sample  by  commercial  at  September  to  over  of  determined  vessels  complemented ports,  were  until  fishermen  escape  The  distributions  were  was  and  traps  sampled  1986.  The  1984,  in  in  and  October  (P.A. Breen,  hauled,  location,  Inlet  July of  The F r a s e r d e l t a  1985  other  Holberg  and M a r c h  sampled  data). and  were  1986.  1983  and  fishery  was  unpub. soak  data).  time,  trap  recorded.  3.4 FEMALE SIZE-AT-MATURITY From collected  S e c t i on  June in  3.3  1985 traps  until or  September  trawls  near  1986 Tofino  females were  >80 mm CW  dissected  Page  to  16  determine mating, least  i f a pair was  of sperm  present  10 females  dissected.  packs,  in their  i n each  p l a c e d by a  spermathecae  5 mm  interval  male  (Butler  from  during  1960).  80-160 mm  CW  At were  In March and J u l y 1986 «=50 large females c o l l e c t e d i n  Holberg I n l e t  (SA 27) were a l s o  dissected.  3.5 MATING PAIRS When mating p a i r s trawls,  carapace  of C. magi s t e r were c o l l e c t e d  widths  of  were  measured.  r e c o g n i z e d as a male c l a s p i n g  a smaller  Mating p a i r s  are e a s i l y  female  her abdomen  with  Neilsen  1966).  monitored  When  against  the mating  carapace widths  pair was  1960,  was  Snow and  retained  complete  and  to obtain  from the female.  TRAP DISTRIBUTION  The  number  determined  by  of  crab  traps  interviewing  generally  fish  Passage, near To reported  study.  fished  With  i n the study  at approximately  September 1986.  sites  area  ( e . g . Lemmens  was  monthly  Because fishermen Inlet,  Browning  Indian I s l a n d ) t r a p d i s t r i b u t i o n was a l s o a s s e s s e d .  verify  buoys  specific  fished  fishermen  i n t e r v a l s from June 1985 u n t i l  trap  individuals  h i s (Butler  convenient,  i n an e n c l o s u r e u n t i l  pre- and post-moult 3.6  both  i n t r a p s or  i n f o r m a t i o n from  fishermen, the number  i n Lemmens I n l e t  was compared with the number of  counted  there  each  few e x c e p t i o n s each  month trap  of traps  f o r the d u r a t i o n buoy  indicated  of the  one  trap.  Traps were counted d u r i n g calm weather from a moving b o a t .  S e c t i o n 3.4  Page 17  3.7 TRAP PERFORMANCE EXPERIMENTS Several size  processes  frequency  distribution  were p e r f o r m e d t o of  measure  3.  Performing  these  Lemmens  Inlet  assured  excellent  experimental  and  trap  These  locations  being The  these  more  water  per  trap  bait.  Section  of  Indian  working  sex  traps.  processes  ratio  and  Experiments  for  with different  the  the  soak  purpose times.  upper  page  9)  execution  maintaining  and  commercially,  in  2.1,  easy  and  measurement  bays  Fig.  and  setting  fished  two  (A,H;  conditions  crab  were  within  Island  e.g.  hauling,  data the  of grid  recording.  Indian  Island  productive. depth  at  these  were  set  between a d j a c e n t geoduck  Geoduck was  3.6  number,  within  following  experiments  near  experiments  a distance  the  crabs  samples  activities,  patterns,  site  to  The e s c a p e o f c r a b s f r o m t r a p s as a f u n c t i o n of c a r a p a c e w i d t h . The r e d u c t i o n i n t h e e n t r y r a t e o f c r a b s i n t o t r a p s due t o a g o n i s t i c i n t e r a c t i o n s among c r a b s . The r e d u c t i o n i n t h e e n t r y r a t e o f c r a b s i n t o t r a p s due t o c h a n g e s i n b a i t e f f e c t i v e n e s s .  2.  two  of  the  s t a n d a r d i z i n g commercial  1.  in  contribute  clam the  locations in  traps  (Panope  choice  of  grid of  «=7-12  patterns =*75 m.  abrupta most  was  m.  Traps  used  (Fig.  3.7.1)  with  A p p r o x i m a t e l y 0.5  (Randall))  commercial  was  used  kg for  fishermen.  Page  18  GRID LAYOUT FOR TRAPPING  A) SOAK T I M E EXPERIMENT  EXPERIMENTS  ©©®©@© ® ©@® ® ® ® ®©@® ®  ©@® ©o© ®®©@©© ®@®®®©  B) BAIT A G E EXPERIMENT  C) SELECTIVITY EXPERIMENT  ®©o© ©oo© ©©©© o©o© ©®©®©@ © ©©®® © ©©© ©® ® ®® ®® ® © ©@®®@® © ©©©© ©  Figure 3.7.1. Layout of t r a p g r i d s d e s i g n e d to emphasize the effects of different soak times (A), changes in bait e f f e c t i v e n e s s ( B ) , a n d t r a p s e l e c t i v i t y ( C ) , on t h e d e n s i t y and s i z e f r e q u e n c y d i s t r i b u t i o n o f C . magi s t e r . For ( A ) and (B) soak t i m e ( i n d a y s ) i s e n c i r c l e d , f o r ( C ) t r a p t y p e i s e n c i r c l e d .  Figure  3.7.1  Page  19  3.7.1 The or  basic  TYPES commercial  rubber-wrapped  Trap of  height a  trap  is  trap  opposed  iron  give  21-25  a  steel  an  wire  mesh  placed  plastic  in  a  crab  a  stretched  bait  rubber  trap  their  the  of  a  ports  are  were  all  grid  crabs.  Section  A is  3.7.1  in  replaced  (1976a)  of  ports.  a  a  to  from  the  enter  the  of  the  1 mm  trap  stainless  perforated  and  crabs  shut  traps  by of  (1978,  the  Escape ports the  25 cm  center  and M i l l e r  to  bottom  configuration.  normally held  perpendicular  entrance  5 0 0 mL  removed a  hook  this  by  on  a  general  1979).  number  are  Bait  and  inside  located high tunnels.  in  Paired  d i a m e t r i c a l l y opposed.  not  B and  No e s c a p e p o r t s ( r e s e a r c h traps) 1 1 0 2 . 5 + 0 . 5 mm e s c a p e p o r t 1 1 0 9 . 2 + 1 . 5 mm e s c a p e p o r t 2 1 0 9 . 2 ± 1 . 5 mm e s c a p e p o r t s  legal  experiments  Traps  is  trap  the  cm.  diametrically  slope  by  steel  90-105  on  Two  20°  d i s t i n g u i s h e d by  Trap A Trap B Trap C Trap D Trap  a  4 cm d i a m o n d the  from  recessed  enclosed  Photographs  escape  trap  7 by  l i d  strap.  15-25 k g .  ascend  are  stainless  placed  opening toward the  jar  trap  types  to  of  seen, i n H i g h  of  escape  center  fold-over  diameter side  a  bars  tunnels  Traps  forming  The  c a n be  Four  exit.  the  jar.  opening  design  easy  of  with  in diameter  weight  cm e n t r a n c e  require  circular  ranging  weight  Two o n e - w a y t r i g g e r s  prohibit  is  Two i r o n  it  b y 10  trap  frames  25 c m .  perimeter  trap.  is  TRAP  to  D are  for  commercial  achieve legal  for  higher  fishing  but  was  retention  of  commercial  fishing  used  in  smaller and  were  Page  20  used not  locally used  the  locally,  (Section Traps  by  3.7.3)  fishermen  T r a p C was to  whose  catch  included  provide  an  I  sampled.  Although  in a s e l e c t i v i t y  intermediate  experiment  escapement  between  B and D .  3 . 7 . 2 CATCH RATES OF TRAPS IN GRIDS The format  following  assume  units.  By  fishing  that  all  the  interior  traps  1985  5 by 5 g r i d s  two  traps  comparing in  a  upper  Lemmens I n l e t  traps  in  both  a s s e s s e d as  experiments  this  were  in Section  2.1,  sampling  equivalent  sampling  the was  each  page 9 ) .  trap  perimeter tested.  of  the  After  For each  and t h e  a grid  of  assumption in  use  are  rates  hauled.  3.2,  grid  arranged  (A; F i g . were  a  catch  grid,  grids  in  which  and  In  two  July  bays  in  a 24 h soak  trap,  all  location  crabs  all were  i n the  grid  was  A  24 h  was  recorded.  3 . 7 . 3 ESCAPE OF CRABS FROM TRAPS The  percent  estimated them  in  soak. with  a  tagging  trap,  After  each  previously  period. Crabs  by  The with  presumed t o  Section  of  then  represent  3.7.1  Trap  in  apparently  healthy  counting  the  remaining after  tagged  that  escaping  several  trap haul  tagging tags  C . magi s t e r  untagged  crabs,  c r a b s were  monitored  procedure were  number  is  retained  independent  for  by  a  tagged a  described  crabs,  a  and,  successive in  trap  observations  placing  for  Section for the  24 h along 24 h 3.8.  24 h  were  next  24 h  Page  21  period.  For example,  consecutive different  days  is  o b s e r v i n g a tagged  Island  experiment  loaded to  and  1986  changing  b i a s e s that or  and  in  changed  and  assessed as 3.7.4 A  This  from June-August of  up to  tagged  10  locations,  consistently  1985  consecutive  crabs,  of  Traps  days. without  helped newly  used.  B-D r e l a t i v e  reduce captured  Thus, the  these  commercial  to  Trap  A were  f i s h i n g nine traps of Traps A-D i n a (Fig.  3.7.1c).  36 t r a p s were hauled a f t e r replaced.  in Section  All  crabs  Each day,  a 24 h soak,  in  each  trap  for  the  bait  type  were  3.2.  SOAK TIME EXPERIMENT grid  and s i z e  A traps  (Fig.  3.7.1a)  frequency  hauled  after  was  used  distributions  soak  times  of  of 1,  T h i s g r i d was arranged i n upper Lemmens Inlet  Section  m depth.  only f r e s h b a i t ,  i n a 6 by 6 g r i d  traps  6 by 6  densities Trap  all  =7-10  near  study a r e a .  determined by s i m u l t a n e o u s l y pattern  if  were  at  t r a p ) and  or i n p a i r s  should be g e n e r a l l y a p p l i c a b l e to  selectivities  seven days,  9),  different  'reusing'  site  f i s h e r y throughout the  regular  page  hauled for  may have r e s u l t e d  escapement r a t e s  The  2.1,  experiment  single  (*5-10 per  i n upper Lemmens I n l e t ,  being  bait  a  five  densities  performed i n t e r m i t t e n t l y  this the  typical  Fig.  with traps  Performing  crabs,  (A, H;  was  to having observed  24 h .  p l a c e d in a 5 by 5 g r i d Indian  five  c o n s i d e r e d equivalent  crabs a f t e r  Traps were  crab i n a t r a p for  3.7.3  to  determine  C . magi s t e r 2,  5 and  the  within  10  days.  i n August 1985  and  Page 2 2  near  Indian  randomly Twenty the  Island  hauls  appropriate  following  were  times  for  for  each  made on  The e n c i r c l e d numbers  10  traps soak  consecutive  composing time  the  trial  days  indicate  by  grid. hauling  according  to  the  prior  to  the  for  20  day  Two 1 day soak t r a p s h a u l e d e v e r y d a y . Four 2 day soak t r a p s h a u l e d e v e r y s e c o n d d a y . Ten 5 day soak t r a p s h a u l e d e v e r y f i v e d a y s . Twenty 10 day soak t r a p s h a u l e d a f t e r 10 d a y s .  the  5 by 4  grid  described grid  Because  shorter  soak  traps  separate  previously  with  1986.  schedule.  1. 2. 3. 4.  soak.  June  distributed  (20)  A  in  the  shorter soak  20  time  to  day  soak  was  provide trial  time  trials  time.  used  i n b o t h the  1985  and 1986  After  trap  haul  changed.  A l l crabs  were  r e p l a c e d where t h e y were  was  assess  over  each  20  trials,  to  No d i f f e r e n c e s  arranged  were  it  evident  days  replicates  not  any  20  fished  was  simultaneously  repeated  trend so  a  in  the  after  the  catch  earlier  the rate  trial  was  experiments.  crabs  were  assessed  as  released in  and  Section  the  3.2.  was  bait  Traps  were  hauled.  3.7.5 BAIT-EFFECTIVENESS EXPERIMENT Changes crabs were 10  soak  densities  and  w i t h i n Trap A r e s u l t i n g a s s e s s e d over t h e  day  for  in  soak  this  trials  experiment  time  Sect ion  time  grid  3.7.4  in  same  from  frequency  changes  10 d a y t i m e  (Section  (Fig. upper  size  3.7.1b) Lemmens  Inlet  in b a i t  p e r i o d as  3.7.4). was  distributions  The  effectiveness  the  1,  2,  4 by 4 g r i d  arranged near in  August  of  5 and used  t h e "6 b y 6  1985  and  near  Page  23  Indian and  Island  bait  each the  age  of  with  with  two  grids  Both g r i d s  1986.  experiments  the  two  i n June  at  bays were  each  site  At  beginning  traps  frequency  bait.  were  After  hauled,  without  changing  the  removed  and  traps  the  a s s e s s e d as  the  9).  each to  Near  other sample  soak  one  grid  Indian  (H;  in  Island  Fig.  crab  time  2.1).  populations  distributions.  the  experiment for  crabs  bait.  all  eight  On t h e  16  traps  consecutive  released,  replaced  in Section  Inlet  by 2 km, w i t h  page  presumed  24 h ,  the  2.1,  200 m of  were  of  Lemmens  separated  Fig.  within  size  fresh  were  (A;  similar  the  In upper  and  ninth  without  the  day  were  days,  traps  the  bait.  all  16  replaced  bait  All  set  jar  was  crabs  were  3.2.  3.8 MARK-RECOVERY PROGRAM Male a n d female April  1985  females  and  were  determined  traps,  and t a g  Section  3.2.  or  Most  size.  for  fishermen,  Blue,  1986.  a grid  Crabs  location  and  May  sublegal  with  landmarks.  C . magi s t e r were  Co.,  and r e c o v e r y system  tagging  obtained  were Before  numbered, P.O.  inserted gently  suture  with  3.7.5  sublegal  identification  U . S . A . ) were  a  and r e l e a s e d  were  being  number were r e c o r d e d .  Manufacturing  S e c t i on  males  Release  trawling.  individually  line  tagged  tagging  Box  4.1  size,  all  locations by 1.2  from  were  km)  cm  released,  5357,  anchor  the  right  taking  tags  Seattle,  care  date,  (Floy  in  Tag  Washington,  posterior not  and  'research'  C r a b s were a s s e s s e d as  t h r o u g h the gun,  (0.9  between  to  epimeral puncture  Page  24  internal it  organs.  contrasted  The c o l o u r  well  with  thereby  increasing  epimeral  suture  when  the  old  assumption,  the  left  traps. of  male  fishermen  also  measured  were  generally  was  recorded  a me  by  the  recoveries  an  vessel  associate,  at  the  tagged  dock  or and  legal-sized  moult.  tag  To  was  test  this  inserted  fishermen  850 as  though  special  using but  retrieve  tags  males  live  research  calipers.  Three Females  legal-sized or  fishermen  crabs,  number  forms.  retained  other  of  and  l o c a t i o n and t a g  but  males  released generally  retained  information provided T a g s were  permission  in  rate  inserted  on  Most  fishermen. had  retention  were  released,  The e x t e n t  I  the  tags  date,  sublegal-sized  males.  through  tagging  width  fishermen. of  high  Whether a c r a b was  r e t u r n v a r i e d among  or  kept  retained.  legal-sized  tag  were  C. m a g i s t e r ,  double  from  recovered  carapace  males  of  because  line.  obtained  they  tags  by  second  suture  the  tag  a a  Two  r e c o r d e d the  crabs  sublegal-sized  from  were  assure  assessed  the  epimeral  and  ignored  that  fishermen  tagged  was  the  during  C. magi s t e r .  recoveries  Four  to  for  colouration  Placing  discarded  except  posterior  all  is  chosen  natural  assumed  retention  above  Most  is  shell  sublegal-sized described  the  was  visibility.  line  tag  blue  to  set  either  board  a  aside.  wells  until  tags with  given  to  fisherman's  Some  fishermen  I could  measure  them.  The  information obtained  supplemented  by  fished,  and  the  S e c t i on  3.8  my  from  knowledge  frequency  of  with  a  tag  recovery  where which  I  was  sometimes  particular  fishermen  checked  with  them  Page  25  regarding saw most  recoveries. fishermen  increased  the  buying  and  Supply  Limited  at  number  sorting of  From A p r i l least of  3.8  biweekly,  tag  sessions.  August  at  recoveries One  major  i n 1985  other by  times,  attending  buyer,  Vancouver, B . C . recovered  p u r c h a s e d and m a i l e d them t o  Section  until  tags  and 1986 monthly. dock  Tri-Star from  I I  side  Seafood  crabs  they  me.  Page  26  4 RESULTS 4.1 SPECIES COLLECTED Three C.  productus  the  crab,  although  magi s t e r  spp.  Randall,  graceful  methods, C.  Cancer  was  were the  collected  red  accounted  rock  for  i n the  traps  crab,  <5% of  in c e r t a i n areas  considered  in  and  the  and  following  trawls.  C . gr ac i 1 i s  total  t h e y were  beam  catch  Dana,  by  these  more a b u n d a n t .  Only  analyses.  4.2 MORPHOMETRICS Notch-to-notch spine-to-spine C.  magi s t e r ,  (SAS  carapace  carapace  width  respectively,  Institute  Inc.  width  1985)  by  (CW, mm)  (S,  the  valid  mm)  for  following  for  all  is  determined male  linear  observed  and  from female  relationships  carapace  widths.  Males: CW = 0 . 9 3 7 - S ;  p<.0001,  r >99.9%,  n=509  (4.2.1)  p<.0001,  r >99.9%,  n=478  (4.2.2)  2  Females: CW = 0 . 9 5 0 - S ; The p r o b a b i l i t y of notch-to-notch,  a male,  exceeding  CW ( s p i n e - t o - s p i n e ) was >165  the  Section 4  from 152-156 mm  whose  c a r a p a c e w i d t h was  minimum l e g a l  determined  mm CW ( s p i n e - t o - s p i n e )  interval  2  for  25  from  the  crabs  size  limit  measured of  165 mm  p r o p o r t i o n of within  each  males  1 mm CW  (notch-to-notch).  Page  27  The  probability  of  n o t c h - t o - n o t c h carapace  a  width  male  being  legal  lies  within  a 1 mm  size  when i t s  i n t e r v a l between  153-155 mm CW i s l i s t e d b e l o w . Male n o t c h - 1 o - n o t c h c a r a p a c e w i d t h (mm)  P r o b a b i l i t y of being legal size  <153 153- 154 154- 155 >155 The  following  carapace  width  120-185  and  respectively.  0 .00 0.40 0 .72 1 . 00  linear  (CW,  mm)  and body  120-175 mm Some  these ranges w i l l  relationships  CW,  length  f o r male  extrapolation  between  notch-to-notch  ( L , mm)  are v a l i d for  and  of these  female  C. m a g i s t e r ,  relationships  beyond  not introduce s i g n i f i c a n t e r r o r .  Ma1e s: L = 4.95+0.677-CW;  p<.0001, r = 9 8 . 4 % , n=390  (4.2.4)  p < . 0 0 0 1 , r = 9 5 . 5 % , n=330  (4.2.5)  2  Females: L = 1.94+0.718-CW;  FEMALE SIZE-AT-MATURITY  4.3  In t h i s dissected or the  2  study a l l females  o f 180 mm  t h e time Holberg  abundant,  a l l of  contained a pair  Section  4.2  CW h a d b e e n m a t e d r e g a r d l e s s  of year Inlet  >115 mm CW up t o t h e l a r g e s t  when  they  fishery, *50  large  o f sperm  were where  collected large  ( 150-180 mm  CW)  size  of the l o c a t i o n ( F i g . 4.3.1).  females females  were  In most  dissected  packs.  Page 28  100 -1  X  o  UJ  h-  80 H 60  CO  I  o  40  r-  «  CM  CM  II  O cr  20 n = 50-  UJ  0_  I  0  c  S.EJ_  o OJ  O CM  CM ro  c  c  c  II  II  II  4.3.1  CVJ II  c  O O A c  c  T 82.5 92.5 102.5 112.5 122.5 CARAPACE WIDTH ( ± 2 . 5 m m )  F i g u r e 4.3.1. The p e r c e n t o f f e m a l e as a f u n c t i o n o f c a r a p a c e w i d t h .  Figure  o  O CM n  C. m a g i s t e r  inseminated  Page 29  4.4  MATING PAIRS  Twenty-one between by  April  1985  97 m a t i n g p a i r s  Entrance of  (21)  during  male  the  versus  mating and  1950's.  data,  female  for  a m a t i n g embrace t o  1960).  (1961)  study  4.4.1 of  this  represents  These  the  represent  lines  Size (Fig.  for  combinations Males are  females  are  were  presents  widths  occur.  mating  4.4.1  were  supplemented  preferences,  page not  i n Dixon  a scatter  mating limits  plot  pairs.  of  As  male (MCW)  apparently  necessary  considered  functionally  considered  mature  frequency d i s t r i b u t i o n s 4.6.1,  measured  (unpub. d a t a )  carapace  130 ram CW a n d  70 mm CW ( B u t l e r and  C . magi s t e r  1986.  Figure  (FCW) c a r a p a c e w i d t h  near  of  m e a s u r e d by T . H . B u t l e r  and  mature  September  female  s u g g e s t e d by t h e s e  pairs  37)  from  suggest  restricted  near Butler  that  Fig.  availability  females.  Upper  line: FCW = 165 .0 • {1  Lower  4.3  (4.4.1)  1ine : FCW =  Section  .0-exp[-0.04•(MCW-105.0)]}  70.0+exp[0.045-(MCW-130.0)]  (4.4.2)  Page  30  6 0  -\ 130  1  1  1  1  1  1  140  150  160  170  180  190  MALE  WIDTH  1 2 0 0  (mm)  Figure 4 . 4 . 1 . Carapace widths of C . magi s t e r mating p a i r s . The l i n e s (Eqns. 4.4.1 and 2) define the apparent l i m i t s i n carapace widths r e q u i r e d for a mating embrace. C i r c l e s represent data from B u t l e r (unpub. d a t a ) , squares represent data from t h i s study.  Figure  4.4.1  Page 31  4.5 MOULT INCREMENTS Relationships at-size and  for  male  and  post-moult  records  is  between  (76  l i m i t e d pre-moult with  equivalent  Butler  (1987 )  5 mm  CW  analysis.  provide  (1983 )  from  provides  regression  analyses  presented  in  were  7  for  range, other  moult  they  they  Collier  increments-at-size  Tables  for  Institute  Inc.  and  2,  for  within  a  Because  for  Dixon  reanalysed  using  males, for-  1985)  of  supplemented  (1983)  i n c r e m e n t s - a t - s i ze  4.5.1  and  sources.  are  pre-  number  were  published  from  increments-at-size  intervals,  (SAS  The  females), so  increments-  obtained  males,  four  moult  moult  measurements.  From C a l i f o r n i a ,  moult  and  width  summarized  by  regression  for  width  C . magi s t e r  carapace width  data  (1961)  Entrance  female  carapace  small  carapace  and and  Warner Diamond  females.  for  these  males  The  data  are  and  females,  significant  (p<.05)  r e s p e ct i v e l y .  Analysis  of  covariance  differences  between  and  data  female  considered  4.5.1)  4.5.1  and  and  2).  maximum  individual  4.4  However,  to  all  used  differences  data  sets, the  reject  female  Authors  <2 mm, and o n l y a t  S e c t i on  regression  sets.  sufficient  (Eqn.  the  the  indicated  for  the  low e x t r e m e  the of  models  model  the  different this  based  data  not  on a l l  male (Figs.  techniques,  predictions  combined range  male  is  combined  measuring  the of  the  reasons  4.5.2)  different  those  for  two  two  (Eqn.  between  and  models  data  and  for  the  sets,  are  sampled.  Page  32  Table 4 . 5 . 1 . L i n e a r r e g r e s s i o n models f o r male C . magi s t e r moult increments-at-size for four data sets collected from B r i t i s h C o l u m b i a ( B . C . ) and C a l i f o r n i a (Cal.).  n  E  19 . 72+0.059-CW 1 5 . 78 + 0 .078-CW 16 . 50+0.078-CW 21 . 19+0.046-CW  277 72 19 76  < .0001 .0090 .0794 .1751  11.8 9.4 1 .7 2.5  I = 18 . 07 + 0 .069-CW (Eqn. 4 . 5 . 1 )  444  < .0001  11 .3  Model I I I I  = = = =  equat i o n  a  v {% 2  )  Source  Region B.C Cal Cal B.C  . . . .  B u t l e r (1961) C o l l i e r (1983) Warner ( 1 9 8 7 ) T h i s studyAll  I i s t h e m o u l t i n c r e m e n t - a t - s i z e (mm). CW i s t h e p r e - m o u l t c a r a p a c e w i d t h (mm). The s t a n d a r d d e v i a t i o n o f t h e e s t i m a t e f o r i s 1.26, for the s l o p e , 0.009.  the  data  sets  b  intercept  Table 4.5.2. Linear regression models for female C . magi s t e r moult increments-at-size for three data sets c o l l e c t e d from B r i t i s h C o l u m b i a ( B . C . ) and C a l i f o r n i a (Cal.). n  E  I = 28. 63 - 0 .100-CW I = 3 2 . 11 - 0 .13 5- CW I = 27. 77-0.105-CW  44 277 7  .0006 < .0001 .0567  24 .6 43 .5 54 .9  I = 3 2 . 3 5 - 0 .13 6•CW (Eqn. 4.5.2)  328  < .0001  46.0  Model  a  b  equat i o n  a  r (%) 2  Region B.C . Cal . B.C .  I i s t h e m o u l t i n c r e m e n t - a t - s i z e (mm). CW i s t h e p r e - m o u l t c a r a p a c e w i d t h (mm). The s t a n d a r d d e v i a t i o n o f t h e e s t i m a t e f o r i s 1.076, for the s l o p e , 0 . 0 0 8 .  Section  4.5  Source B u t l e r (1961 ) Diamond (1983 ) This study All  the  data  sets  b  intercept  Page  33  Figure 4.5.1. Male C . magi s t e r moult increments as a f u n c t i o n of p r e - m o u l t carapace w i d t h . The p l o t u s e s d a t a from British Columbia and California. Data from this study are r e p r e s e n t e d by s q u a r e s .  Figure  4.5.1  Page  34  30  -i  Figure 4.5.2. Female C . magi s t e r moult increments as a f u n c t i o n of pre-moult carapace w i d t h . The p l o t u s e s d a t a from British Columbia and California. Data from this study are r e p r e s e n t e d by s q u a r e s .  Figure  4.5.2  Page  35  4 . 6 GROWTH Instar were  mean  determined  widths  of  sample  size,  all  sizes from  crabs  data  September  thus  from  crabs  1986  were for  larger shows instars and C.  are  decomposing size,  used  is  and  because  samples  that  trap  Section  between  the  were  samples  4.6  the  To  carapace  increase  frequency from  single  June  the  analyses, 1985  until  distributions  (1 mm  distributions  moulting  distribution  samples  Butler  size  trawls  create  by  and  it  of  is  and  are  summarized  by  the  at  and  size  collected size  strongly  of <80  generally be  by  a  new  Only  instar  increment  in  traps  instar  a  larger not  mm CW were  show  were  not  that  and  used  distributions  see  Since  the  carapace  included.  b i a s e d by d i f f e r e n c e s (e.g.  mean  should  >80  a  a  one  at  times  crabs  that  CW).  with  (1983)  mm CW a r e  by  a  instar  presumed  Collier moult  to  any  described  different  frequency  experienced  instar  within  increments,  distributions. (1961)  one  1 5 5 . 0 + 1 1 . 2 mm  forming  taken  from crabs  can  (e.g.  subsequently  normal  of  C . magi s t e r  4.6.1.  grows  size  for  samples.  the  beam  discontinuously  from c r a b s  trap  of  The  n o n l i n e a r when c r a b s  Data growth  sex.  deviation  grows  because  width  in  trawl  normally d i s t r i b u t e d  these  relationship  caught  variability  combining  confound  analyses  beam  in F i g .  standard magi s t e r  frequency  combined t o  The  natural  deviations  power  magi s t e r  instar.  in  standard  the  each  5 mm CW i n t e r v a l s  Cancer  size  caught  and  CW i n t e r v a l )  and  Section  to  analyze  obtained  i n the  soak  from time  4.7.3).  Page  36  lO-i  8-  MALE n » 3307  41  S  2-  °-  0  >O  z  UJ D O UJ  — LEGAL SIZE ( > 155mm )  LThru  I2-| 10-  FEMALE n - 1649  8-  42-  2.5  52.5 CARAPACE  102.5 WIDTH  152.5  1  202.5  (±2.5mm)  Figure 4 . 6 . 1 . S i z e f r e q u e n c y d i s t r i b u t i o n s f o r a l l male and f e m a l e C . m a g i s t e r c o l l e c t e d i n beam t r a w l s a m p l e s f r o m June 1985 u n t i l September 1 9 8 6 .  Figure  4.6.1  Page  37  The Schnute male  size  frequency analyses  and F o u r n i e r  and  female  Tables  4.5.1  instar  mode was  number  (N) for  (1980),  growth  and  2,  modeled  standard deviation  and  include  33). as  The  a  on t h e  the  methodology  of  equations  for  linear  (Eqns.  4.5.1  and  standard d e v i a t i o n  function  recognized  for  based  increments-at-size  page  modes  were  by  of  the  the  (D)  consecutive  model,  where  2  in  of  an  instar  'd'  is  the  females,  are  N=l.  Males: D  = d• 1 . O e S ^ '  1  )  (4 . 6 . 1  )  Females: D = d-0.864  The  constants  equal  to  of  the  standard  1.069,  slope+1  results of  of  (Sect ion  each  are  0.864,  4.5.1  and  2,  equations and  the  (i.e.  recognized in  (i.e.  defined  by  vary  provided  yield-  for  and presume  instars  they  4.6  there the  the  is  the  facilitated and  mean  size  one  with  that the  most easy  the  moult  suitable simulation  eggs-per-recruit  frequency  equations  the  standard deviation  in  relation  relating  to  equations.  unknown  carapace  the  standard deviation  Section  in  analysis  equation  parameter number  growth  and  particular  assessed,  (4.6.2)  1  model  5).  For  instar  for  ' >  males,  Eqns.  These  those  instar  growth  in  deviations  increment-at-size.  for  ( N  the  parameter  width  model),  for and  the one  standard d e v i a t i o n for  first  to  N=l).  Subsequent  instar  by  Additional  the  parameters  in  the first  unknown instar instars  growth  and  estimate  the  Page  38  proportions-at-age size  frequency  parameter males. size  measuring  are  listed  maximum  size  were  and  a  the  time  2  and  from  Eqns. of  the  ' d ' in Eqns. The  102.9  spring  instar  1986.  throughout  then  summer  1986,  annually.  Section  of  females  4.13).  females mate  into  only  beam  the  and  1986  and  into  into  this  the size  following  4.5.1  estimates and  mm i n s t a r the  119.4  135.5  by  their  the  instar  mm i n s t a r  mm i n s t a r  moult  by  1 5 5 . 0 mm  mm f e m a l e  the  2.  samples  assessed  The 1 0 0 . 7  4)  standard  trawl  into  was  2.  instars  Eqns.  128.0  instar  moulted  moulted  means  the  and  4.6.3  using  the  by  4.6.1  The p a r a m e t e r  the  A  statistic  from T a b l e s 4 . 6 . 1  this of  1985).  evaluate  (Tables  the  legal  SIMPLEX  determined  analyses  taken  to  Tables  samples  moulted  1985  instar  suggesting  Since  4.6  This  the  male and f e m a l e  define  remainder  from June - September  by J a n u a r y 1986.  in  dominated  The m o u l t i n g the  used  respectively.  m a r k - r e c o v e r y program ( S e c t i o n present  to  instar  from J u l y - D e c e m b e r 1985, late  2  a n d 2 were  mm male  legal-sized  separation  instars  defined  frequency  and  instars, 4.6.1  female  beam t r a w l  4.6.1  was  p r o p o r t i o n s of  size  The  additional  of  using  the  ( 1980 ),  are  of  an  obtained  and  relative  series  determined  deviations for  analyses  included  model.  between 152-156 mm b e i n g  function,  Fournier Male  the  ( M i t t e r t r e i n e r and S c h n u t e  objective  and  frequency  within  package  by  exploitation  males  estimates  estimates.  Subsequently,  of  4.2.  estimation  parameter  males  in Section  Schnute  recognized  size-specific  likelihood  of  instar for  The p r o b a b i l i t i e s  nonlinear  were  each  analysis  Parameter  'A'  for  only  moult  in  once  (Butler  Page  39  1960), Few  this  males  1986.  suggests or  Crabs  (Butler either  1961, little  peak  females this  Stevens  are  and  79.3 102.9 128.0 155.0 183.8  b  sd  a  b  b  4.6  in  summer  ( p o s t - s e t t 1ement) there  was  1984.  Proportion  9.2 9.8 10.5 11.2 12.0  0.2 -  5  0.071 0.295 0.445 0.188  c o m b i n e d beam t r a w l  samples  and s t a n d a r d d e v i a t i o n s (SD, sd) for i n s t a r s o f f e m a l e C . magi s t e r >80 mm CW. Proport ion'  SD sd  E s t imate  sd  14.8 12.8 11 .0 9 .5 8.2 7.1  2.6  4. 6  The p r o p o r t i o n of f e m a l e s i n t h e c o n t r i b u t e d by e a c h i n s t a r . D e t e r m i n e d by e x t r a p o l a t i o n .  S e c t i on  survival  summer.  during  suggesting  sd  Mean  79 100 119 135 149 161  1984)  E s t imate  0.3 - .  Table 4.6.2. Mean carapace widths d e f i n i n g  Estimate  old  SD  The p r o p o r t i o n o f males i n t h e c o n t r i b u t e d by e a c h i n s t a r . b D e t e r m i n e d by e x t r a p o l a t i o n .  1 2 3 4 5 6  or  present  during  and s t a n d a r d d e v i a t i o n s (SD, sd) for i n s t a r s o f male C . m a g i s t e r >80 mm CW.  a  Instar  occurs  years  Armstrong  Mean E s t imate  1 2 3 4 5  two  settlement  Table 4.6.1. Mean carapace widths d e f i n i n g  Instar  activity  80-120 mm CW were  size  larval  mating  0 0 0 0 0  c o m b i n e d beam t r a w l  . 001 .386 . 529 . 067 . 016  samples  Page  40  Table 4 . 6 . 3 . The r e l a t i v e p r o p o r t i o n s of male C . magi s t e r >80 mm CW w i t h i n c o n s e c u t i v e i n s t a r s f o r a t i m e s e r i e s of beam trawl samples. The v a l u e for each date includes all males c a p t u r e d w i t h i n two weeks of t h a t d a t e . The d o m i n a n t i n s t a r is h i g h l i g h t e d b y an a s t e r i s k .  Date  Sample  Instar mean c a r a p a c e (mm)  size 79 .3  21 11 14 11 16 4 8 4 5 8 7 4 11 6 9  Jun Jul Aug Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug Sep  S e c t i on  4.6  1985 1985 1985 1985 1985 1985 1986 . 1986 1986 1986 1986 1986 1986 1986 1986  97 255 147 115 290 143 202 245 581 280 318 199. 41 27 32  0 . 42* 0 . 15 0 . 14 0 . 00 0 . 00 0 . 04 0 . 02 0 . 01 0 . 00 0 . 02 0 . 01 0 . 03 0 . 00 0 . 00 0 . 02  102 .9 0 .23 0 .73* 0 .69* 0 .84* 0.64* 0 .48* 0.41 0 .24 0.10 0 .08 0.11 0 .21 0 .21 0.13 0 .05  width  128 .0 0 . 08 0 . 02 0 . 04 0 . 00 0 . 35 0 . 37 0 . 56* 0 . 42* 0 . 73* 0 . 62* 0 . 61* 0 . 71* 0 . 50* 0 . 19 0 . 18  155.0 0.26 0.10 0.13 0.16 0 .01 0.10 0 .00 0.33 0.16 0.27 0.27 0 .06 0.28 0 .68* 0 .75*  Page  41  Table 4 . 6 . 4 . The r e l a t i v e p r o p o r t i o n s o f f e m a l e C . magi s t e r >80 mm CW w i t h i n c o n s e c u t i v e i n s t a r s f o r a t i m e s e r i e s of beam trawl samples. The v a l u e for each date includes all females c a p t u r e d w i t h i n two weeks o f t h a t d a t e . The d o m i n a n t i n s t a r is h i g h l i g h t e d by an a s t e r i s k .  Date  Sample  Instar mean c a r a p a c e (mm)  size 79 .1  21 11 14 11 16 4 8 4 5 8 7 4 11 6 9  Jun Jul Aug Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug Sep  Section  4.6  1985 1985 1985 1985 1985 1985 1986 1986 1986 1986 1986 1986 1986 1986 1986  76 226 167 130 173 119 95 62 56 35 77 38 20 11 177  0 . 24 0 . 00 0 . 00 0 . 00 0 . 01 0 . 14 0 . 00 0 . 05 0 . 01 0 . 05 0 . 00 0 . 08 0 . 05 0 . 00 0 . 00  100 . 7 0 . 53* 0 . 83* 0 . 97* 0 . 66* 0 . 28 0 . 13 0 . 01 0 . 02 0 . 00 0 . 00 0 . 00 0 . 00 0 . 00 0 . 12 0 . 01  119 .4 0 . 14 0 . 14 0 . 00 0 . 32 0 . 71* 0 . 73* 0 . 99* 0 . 90* 0 . 70* 0 . 95* 0 . 69* 0 . 92* 0 . 55* 0 . 77* 0 . 05  width  135 • .5 0 . 09 0 . 00 0 . 02 0 . 01 0 . 00 0 . 00 0 . 00 0 . 03 0 . 30 0 . 00 0 . 31 0 . 00 0 . 40 0 . 11 0 . 53*  149 .4 0 . 00 0 . 02 0 . 01 0 . 00 0 . 00 0 . 00 0 . 00 0.00 0 . 00 0 . 00 0 . 00 0 . 01 0 . 00 0 . 00 0 . 40  Page  42  4.7  TRAP PERFORMANCE EXPERIMENTS 4.7.1  CATCH RATES OF TRAPS IN GRIDS  Analysis caught  in  16  grids  in  catch  rates  between tests  of  variance  perimeter  the  two for  grids (Sokal  bays each  were  in  Lemmens  Inlet,  upper  grid.  distribution  of  the  significantly  (p>.l)  (Table  number from  a  number  different  for  grid.  Therefore,  interior  were  No s i g n i f i c a n t  1981)  (p>.l)  each g r i d ,  number  traps  detected  the  the  interior  Rohlf  of  (1)  and n i n e  and  distribution  compared  normal  of  interior  considered  of  crabs versus  not  within and  two  (2)  5 by 5  the  mean  within  or  Kolmogorov-Smirnov  detect  crabs  that  per  (1)  trap  the  deviated  distribution,  and  per  significantly  trap  was  perimeter  and p e r i m e t e r equivalent  C . magi s t e r  differences  4.7.1.1).  could  of  traps  traps,  sampling  and t h e  (2)  in  the  either  traps  of  units.  Table 4 . 7 . 1 . 1 . C o m p a r i s o n o f the mean number of C . magi s t e r c a u g h t per t r a p f o r 16 p e r i m e t e r v e r s u s n i n e i n t e r i o r t r a p s in two 5 by 5 g r i d s , and b e t w e e n a l l t r a p s i n e a c h g r i d . Per i m e t e r  Inter ior  Grid Grid  1 2  a  a  Mean  SD  Ranqe  Mean  SD  Ranae  5 .7 6 .9  1 .6 2 .4  5-10 3-10  6. 5 6.5  2. 7 3.3  3-14 0-12  > .1 > .1  0-14  > .1  Gr i d 1 Grid 1 vs Grid 2  E  6.2  2 .4  Grid  3-10  6. 6  2  2 .9  The p r o b a b i l i t y t h a t t h e above r e s u l t s a r e o b t a i n e d g i v e n t h e r e i s no d i f f e r e n c e i n c a t c h r a t e f o r p e r i m e t e r a n d i n t e r i o r t r a p s , and b e t w e e n t r a p s i n G r i d 1 a n d G r i d 2.  Section  4.7  Page  43  4.7.2 The  ESCAPE OF CRABS FROM TRAPS percent  of tagged  male C.  A ( ' r e s e a r c h ' t r a p s ) f o r 24 h from CW  135-170 mm were  CW  because  retention  over  retaining  crabs  traps  <135 the  increasing percent  weighted predicted standard  by  the  size mm  were  and  Traps  of  are  they  P  pairs  from  (P,  CW)  differences  in  effective and  in exit  135-170 mm (CW,  CW  mm)  estimated  is  by  d e v i a t i o n s of  (SAS  mm mm,  enter  were  F i g . 4.7.2.1  170-190 20  width  equation  Trap  ranging  and  not  Between  r e g r e s s i o n , i . e . the data  15  easily  (P) w i t h carapace linear  intervals  apparent  entrances.  following  d e v i a t i o n s of  no  within  120-135 and  intervals  because  retention  measured  Crabs  ranges.  CW  mesh  l e a s t - squares and  larger  there  these  through  described  into  retained  i s shown f o r 5 mm  i n F i g . 4.7.2.1.  combined  respectively,  magi s t e r  divided  the  by  Institute  a  the Inc.  1985 ) . P = 2.2432-CW-2.7797 The  p e r c e n t of males of d i f f e r e n t  Traps  B-D  crabs  relative  was  distributions females expressed  (4.7.2.1)  were as  estimated to  Trap  by  caught,  determining  A.  for catches  Figure by  the  u s i n g Eqns.  Section  4.7.2  4.2.4  Traps  A-D.  5  shows  size  Because b o t h for  widths  for  (page  f o r 24 h i n  ability  widths  carapace  and  their  4.7.2.2  carapace  male-equivalent  lengths,  sizes retained  28).  to  retain  frequency males  females the  Since  same  and were body  retention  is  Page 4 4  determined  largely  an  port,  escape  by the  the  ability  critical  of  a  crab to  dimension  in  walk  this  sideways  regard  is  out body  length.  There  were  among T r a p s Trap  A  110  is  and  are  mm)  contention  Traps  that  than  145  crabs mm,  d e t e r m i n e d by (below)  for  relative determined assumed taken of  to  from  be  Eqn. 4.7.2.2  Section  4.7.2  crabs  for  C - D , and  of Trap  B,  103  and body  Traps  Section  B  3.7.1),  155 mm and  supports  traps  are  the  largely  diameter.  than B,  155  the  mm,  and  A,  all (See  an a n a l o g o u s  Traps  the a  The trap  in  Traps  solving  Eqn.  smaller B-D  of  Q for  Traps  one  day  soak  (T = l ) ,  types,  entry  rate  and X^ f o r  (1975)  for  the  is  4.7.2.2  ratio  daily  Ricker  C - D , and  retained  iteratively  after  4.7.2.1. for  for  percent  B-D when  4.7.2.1.  for  respectively,  this  These  than  by  Carapace  of  28).  smaller  of  B,  mm CW.  (see  crabs  retained  Trap  diameters  crabs  of  lengths  page  capabilities  Trap  same  >145  respectively  retention  retention  body  port  Table  for  to  escape  Traps  the  Fig.  for  the  Trap  from  For  4.2.4,  simultaneously  Q  B-D.  Traps  Eqn.  smaller  Xj^ o f  to  to  valid  retention  for  percent  apply  d e t e r m i n e d by e s c a p e p o r t  For  the  ( « 1 0 9 mm),  poorer  mm CW f o r  mm CW, so  (from to  C-D  the  in  155 mm c o r r e s p o n d  close  and  differences  >155  apparently  145  therefore 145  is  to  respectively  lengths (»103  crabs  presumed  of  mm,  apparent  A-D for  presumption widths  no  B-D  (U)  Trap  A  is is is  derivation  problem).  Page  45  Q = <U*Xi ) • [1 . 0 - e x p ( - X i - T ) ]  where:  Q  i s the number o f c r a b s i n a t r a p a f t e r T days U i s the d a i l y e n t r y r a t e of c r a b s into a trap X^ i s the - l n ( d a i l y p r o b a b i l i t y of a c r a b i n carapace i n t e r v a l i being r e t a i n e d by a t r a p )  Relative  retention  determined  by  relative  Trap A.  to  retained percent  in  Trap  for  with  one  more  effectively  perhaps escape  B  It  retention  for  for  Trap  is  A.  port, Trap  easier can  estimates  percent  Table  are  entry  interactions  among c r a b s  of  in  with into  biased  rates,  and  (see  Section  males  Traps <145  0.220  B-D mm CW  times  the  retention  A - D , expressed  retains  smaller  crabs  escape  port,  103  mm  C through  Traps some  perhaps  B-D  the  the  degree also  Trap  as  that  Trap  to  in  is  4.7.2.2  one  for  4.7.2.1)  presents  Traps  Fig.  that  as  4.7.2.2  apparently  entry  crabs  estimated  B,  presume  in  4.7.2  is  noteworthy  differences  Section  the  Table  of  120-170+ mm CW f o r  than  One  Q's,  abundance  24 h  mm e s c a p e  reflecting port.  the  of  For example,  males  probabilities. 109  (ratio  comparing  determined  estimates  (4.7.2.2)  by  C,  larger relative  by  small  agonistic  4.7.3).  Page  46  Table 4 . 7 . 2 . 1 . The r e l a t i v e r e t e n t i o n o f c r a b s <155 mm CW, f o r T r a p s C - D , and c r a b s <145 mm CW, f o r T r a p B , r e l a t i v e t o T r a p A. The r e l a t i v e r e t e n t i o n f o r a t r a p t y p e i s t h e number o f c r a b s c a u g h t by t h a t t r a p t y p e d i v i d e d by t h e number c a u g h t by T r a p A after equivalent one d a y s o a k s . F o r T r a p A n = 536 for crabs <155 mm CW, a n d n=322 f o r c r a b s <145 mm CW.  Trap B C D  n  Relative  71 164 87  r e t e n t i on  0.220 0.306 0.162  Table 4 . 7 . 2 . 2 . The p r o b a b i l i t i e s r e t a i n e d b y T r a p s A - D f o r 24 h . Carapace width  0.023 0.020 0.016  of  Section  4.7.2  male  (mm)  C . magi s t e r  being  Trap A  120-125 125-130 130-135 135-140 140-145 145-150 150-155 155-160 160-165 165-170 >170  Standard error  .130 .130 .192 .304 .416 .529 .641 . 753 .866 .978 .992  B .001 .001 < .001 < . 001 < .001 .529 .641 .753 .866 .978 .992 < <  D  C .001 .001 < .001 < .001 .007 .012 .019 .753 .866 .978 .992  < <  .001 .001 .001 < .001 < .001 < .001 < .001 .753 .866 .978 .992 < < <  Page  47  I—n = 126—1  100 - i UJ  80  I  <  ti  tr  !_ UJ O  or  6 0  40  20 -  UJ  0  I  2 S.E.  -  L - n = 69-1 ro  Mi 122.5  sl-  132.5  X  X  X  CO  ii  II  c  c  T  142.5  CARAPACE  152.5 WIDTH  T  162.5  172.5  182.5  ( ± 2 . 5 mm)  F i g u r e 4.7.2.1. The percent of male C. magister r e t a i n e d by Trap A f o r 24 h, as a f u n c t i o n of carapace w i d t h .  F i g u r e 4.7.2.1  Page 48  60 40  n  2 109mm E S C A P E PORTS TRAP TYPE D  20  nn„.  0  60-i in X) O  40 20  o  E C  nDND  0  o 120 \d>  XI  I 109mm E S C A P E PORT TRAP TYPE C  100 80  ClrUr  I I03mm E S C A P E PORT TRAP TYPE B  60  o UJ  o  40 20  u_  •r ^ n r - i n f l  0  UJ  120  NO E S C A P E PORTS TRAP TYPE A „  100 80 60 40 20  rim  0  1  875 .  1125 -  CARAPACE  1375 .  WIDTH  1625 .  ~1—  1875 .  (±2.5mm)  Figure 4.7.2.2. S i z e f r e q u e n c y d i s t r i b u t i o n s of C . magister caught i n Traps A - D . Female c a r a p a c e w i d t h s are e x p r e s s e d as m a l e - e q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same b o d y l e n g t h s .  Figure  4.7.2.2  Page  49  4.7.3  S O A K  Previous  a stable  result  of  1978,  1979,  rate C.  as  magi s t e r  entry Also,  from  became  decreased.  not  being  changed Miller  C.  were  likely  experiments  observations  by M i l l e r  of  (1978)  crabs  within  traps  other  crabs  through a g o n i s t i c  time  of  C . magi s t e r  entry  of  more  different  4.7.3.2 traps  it  time.  early,  small  Section  It  soak  can be  intimidation is  crabs  4.7.3  in  seen  leave by  larger  possible in  traps  were  crabs  of  the  observed  already  that  occupied  and  inhibited  designed  These  ability  of  the  the  2,  how  the  smaller  are  kept which  the time  5,  by  direct  indicated entry  of  the  inhibiting  the  to  retain  size  crabs,  become  to  which  in  the  crabs  In F i g .  entered  presumably more  when  frequency  10 and 20 d a y s .  out  due  emphasize  encounters,  a trap  reduction is  to  trap  different  of  crabs  1,  a  agonistic  times  over  and  more  duration  Bennett,  within  produced  that  entry  encounters.  the  and  was  the  caught  a  Miller it  C . productus b e h a v i o r ,  individuals  sizes, for  and  1974,  as  C. productus  the  traps  i.e.  time  traps  (1978)  competitively  individuals.  m o d i f i e d by d i f f e r e n c e s  distributions  of  experiments  effect  in  with  for  enter  Miller  that  soak  to  soak  experiments  h a u l e d more o f t e n  1979).  saturate,  (Bennett  abundant  Experiments  (Miller  of  more  bait  The  rates  trapping  traps  less  traps  an a d e q u a t e  and e x i t  that  productus  crab  after  showed  the  The  that  crabs  experiment  crabs.  E F F E C T S  noted  of  crabs  crabs  despite  of  1980).  that  B A I T  have  density  a balance  of  A N D  workers  attain  learned  T I M E  the  due  abundant  to over  abundance  predation  by  of  larger  Page  50  crabs,  but  there  is  no  direct  bait-effectiveness  experiments  decrease  i n the  results the  over of  changes  soak  smaller  time  time crabs,  agonistic  to  of  influenced  parameter  true, of  by  to  be  for  developed  Kolmogorov-Smirnov significantly  (a=.01)  between  soaks  24 h  experiment and  magnitude in  1986  of  the  of  4.7.3  i n the  experiments differences  experiments)  patchiness  Section  and 20 t r a p s 1986  (Sokal  16  animal  and  not  for e.g. and  size  soak (Fig. are  is  and  traps  experiments  changes both  would  in time  unexpected  expect  the  these  two  the  Rohlf  to  entry  and  in  each  used  strictly  true  1981)  since  indicated  frequency  distributions  the  effectiveness  bait  experiment,  4.7.3.1).  small  no  Assuming t h i s  traps  not  bait  assuming  simulate of  in  experiments  describing  to  set  assumption  different of  and  experiments.  combined  tests  trapping  one  equations  was  this  as  rates,  Therefore,  processes,  a dynamic model  However,  apparent  particularly  population,  processes.  the  as  The  interactions,  interactions  both  within  not  the  crabs.  retention  separate  for  crabs  were  The  emphasize  attract  dynamic  a single  the  to  this.  data.  two  for  of  4.7.3.6),  same  experiment.  1985  i n the  these  the  to  size-dependent  both  between  bait  other  as  time  of  Fig.  agonistic  estimates  processes  exit  because  over  interaction  be  (see  emphasize  designed  effectiveness  effects  executed  effectiveness were  in b a i t  variability  Although designed  ability  interactions,  considerable  were  evidence  (D=.20  for  Note in  1985  considering  both  the  that  the  and  D=.13  the  natural  distributions.  Page  51  The  dynamic  densities  and  predicted and  the  in  over  bait  crabs  time.  (in  F o r any  the  crabs  of  effectiveness have  no  entry  effect  rate  placed  a vector  of  The g e n e r a l daily  change  general bait  equation  processes 1986  simulated the  in  bait  the  entry  over  the  4.7.3  entry of  the  and soak  any  this  (Eqn.  of  crabs  (1)  no  time,  were  rate  parameters  for  each  soak  time  begin  as  vector  defined day  if  as bait  a  trap  practice  this  because  bait  soon  is  of  between  and c r a b s w i t h i n In  and  represents  is  each  crabs.  bait  as  a  trap  r e f e r r e d to  as  rates'.  exit time  in  the  variants of  crabs  (4)  data of  into  or  from b o t h  and  of  of  and b a i t - e f f e c t i v e n e s s  of  in (3)  these  the  dynamic out  this  alone,  both  the  net  changes  effects  and  the  Versions  effects  agonistic  to  describes  a trap.  alone,  applied These  4.7.3.1)  agonistic  (2)  effectiveness  experiments.  of  entry  behavior  a trap  trap  the  in  parameters  into  a  interactions  below  number  unknown  this  time,  for  changes  of  5 mm CW i n t e r v a l s  enter  Therefore,  presuming  operating,  duration  Section  achieved  equation  effectiveness  changes  and  in  1986)  rate  and  of  crabs  over  entry  water.  'virtual  (in  decrease  be  of  traps,  function  agonistic  vector  would  and a g o n i s t i c  i n the  a  observed  a  the  5 mm CW i n t e r v a l  the  cannot  deterioration is  on  to  and  within  being  describing  rates  which  d i d not  trap  addition  and e i g h t e e n  90-200 mm CW.  predicted  interactions  effectiveness,  1985)  number  any  In  entry  the  distributions  equations  unmodified d a i l y  twenty  in  agonistic  following  changes  compared  frequency  of  rates,  effectiveness the  size  number  exit  in  model  1985 model  traps  for  experiments.  Page  52  As  mentioned  unknown,  above,  but  the  the  instantaneous  carapace  width  retention  probabilities  As  further  intervals  explained  converted  to  lengths,  since  determining  vector  for  where:  rates  Trap  A from 4.7.2,  is  a b i l i t y to  escape  2  (Xj)  Table  female  for  carapace for  - ( X  is  an  particular  from  important a  rates  4.7.2.2  widths  the  = V i • R  entry  determined  carapace  length  dQi/dt  exit are  male-equivalent  a crabs  virtual  (i)  in Section  body  of  the  24 h  (page  47).  widths  the  same  body  are body  dimension  trap.  i  • Q  )  i  (4.7.3.1)  Q i i s the number o f c r a b s i n c a r a p a c e interval i in a trap t i s t i m e the i n t e r v a l i n d a y s V i i s the d a i l y v i r t u a l e n t r y r a t e i n t o a t r a p for a crab i n carapace i n t e r v a l i X i i s the - l n ( d a i l y p r o b a b i l i t y o f a c r a b i n carapace i n t e r v a l i being r e t a i n e d b y a t r a p ) from T a b l e 4 . 7 . 2 . 2 (page 47) Rl t h e r e l a t i v e e f f e c t o f a g o n i s t i c i n t e r a c t i o n s (from Eqn. 4 . 7 . 3 . 3 ) R the r e l a t i v e e f f e c t of changes i n b a i t e f f e c t i v e n e s s (from Eqn. 4 . 7 . 3 . 5 ) 2  If time,  one  and  traps,  there  then  integrated page  14,  as  changes R3/I  or  Section  are  an  vary  t=0  R <1 2  4.7.3  to  bait  from of  yield  decreasing  agonistic  the  interactions  cannot  change  over  among  crabs  near  4.7.3.1  (see  be  virtual (Eqn.  can  Ricker  Alternatively,  (Eqn. 4 . 7 . 3 . 5 ) ,  4.7.3.1  not  Eqn.  Eqn. 4.7.3.2  derivation).  0.0-1.0  Eqn.  Therefore,  2  T to  does  interactions  R =1.0.  effectiveness  then  effectiveness  agonistic  analogous  result  in bait  no and  1  for  a  that  R =1.0 from  variables (Vi)  assumes  1975,  these  two  entry  rate  4.7.3.3)  respectively.  easily  be  and When  integrated,  Page  so  53  the  entry  number  and e x i t  of  crabs  method of  rates in  a  numerical  The within  trap  at  trap  used  results  competition  of  to  reducing  below.  the  that  small  carapace  the  individuals contest.  i.e.  5% the  dry  competitive individuals feature  Atema  interactions  Section  the  the  Runge-Kutta  1977).  (4.7.3.2)  4.7.3  and  to  overall  Cobb  between  1980 ) . crabs  In  within  with  the  M i I n e - E d w a r d s ).  He  (1971)  larger  lobster  its  competitor  won  for  a  The  of that  three-dimensional  a  claw  special trap  *90%  of of  C. productus .  measure  as  with  observations  presumes  such  of  individual  legal-sized  as  the  sizes  a  weight  size,  the  the  away.  is  on  Scrivener  based  assured  competitor's  crabs  crabs  relative  than  used  of  the  backed  Using a  formulated  of  in  For example, larger  rate  amer i canus  nearly  was  ability.  related  by  s i m i l a r behavior  weight  perceive  entry  differences  loser  (1978 ) s u g g e s t  Crab  1971,  even  length  encounters, Miller  predict  effectiveness  was  experiments  determined  contesting  the  Equation 4.7.3.3  (Homarus  a  using  to  and D i P r i m a  virtual  lobster  winning  (Boyce  describe  American  of  time  time  Q i i s the number o f c r a b s i n c a r a p a c e i n t e r v a l i i n a t r a p a f t e r T days V i i s the d a i l y v i r t u a l e n t r y r a t e i n t o a t r a p for a crab i n carapace i n t e r v a l i X i i s the - l n ( d a i l y p r o b a b i l i t y o f a c r a b i n c a r a p a c e i n t e r v a l i b e i n g r e t a i n e d by a t r a p ) from T a b l e 4 . 7 . 2 . 2 ( p a g e 47)  introduced  two  any  over  = ( V i ^ X i )• [1 . 0 - e x p ( - X i - T ) ]  equation a  integrated  integration  Qi  where:  are  and  size  case one  of  a  crab's  competing size,  or  a  (Scrivener agonistic  attempting  Page  to  54  enter the  that  trap,  the  comparative  Although  Eqn.  relative based  weight  competitive  4.7.3.3  numbers  competitive  a b i l i t y were  where:  (w,  relationship  to  and A r m s t r o n g  effectiveness  of  bait  ability with  at  plus to  other  imperfect  one  weight  less  trap  and  as  capable  a of  a proxy  full  of  for  crabs.  representation  two  parameter  measure  of  of  models relative  d e s c r i b i n g the  data.  (4.7.3.3)  f  g)  (1984)  over  attract  males  (Eqn.  and  width  females  is  crabs  to as  at  defined  by  from  Stevens  are  T=0  (4.7.3.4)  describe  follows.  complementary crabs  determined  4.7.3.4).  chosen time  was  (CW, mm) as  = -9.36+2.832•ln(CW)  which a  for  carapace  equation  rate  an  a  = exp[-e•(W*Wi ) ]  %  ln(w)  a base  likely  of  is  R^ i s the r e l a t i v e e n t r y r a t e i n t o a t r a p f o r a c r a b of weight w W i s the t o t a l w e i g h t o f c r a b s i n a t r a p w^ i s the w e i g h t o f a c r a b i n c a r a p a c e i n t e r v a l i attempting to enter a t r a p e i s the i n s t a n t a n e o u s r a t e of d e c r e a s e in t h e e n t r y r a t e o f a c r a b as a f u n c t i o n o f t h e ' w e i g h t e f f e c t ' r a t i o (w>w^ ) f a l l o w s t h e ' w e i g h t e f f e c t ' r a t i o (W-rWj ) t o assume a n o n l i n e a r form  Dry w e i g h t  The  crabs w i t h i n a t r a p ability  and/or  R  its  is  competitiveness,  on  of  changes  in  Equation 4.7.3.5  attracted component and w h i c h  to  traps which  declines  bait assumes  in  the  absence  has  a  maximum  exponentially  time.  Section  4.7.3  Page  55  R  where:  = g [ d .0-g)-exp(-h-T)]  parameter  experiments  estimates  using  the  (Mittertreiner  and S c h n u t e  function,  separation  (1980),  the  was  used to  information twice  the  model  (4.7.3.5)  +  R2 i s t h e r e l a t i v e e n t r y r a t e of c r a b s into a trap T i s t h e age of t h e b a i t ( i n d a y s ) g is the base r e l a t i v e entry r a t e of crabs i n t o a t r a p when t h e r e i s no b a i t h is the d a i l y i n s t a n t a n e o u s r a t e of decrease i n b a i t e f f e c t i v e n e s s  Separate 1986  2  number  of  performance,  SIMPLEX 1985).  (AIC)  model a  obtained  nonlinear  the  'A'  of  the  1985  estimation  Schnute  parameter  (Akaike  value  was  which used  indicating  objective Fournier  The A k a i k e  equals  to  A  judge  a  and  package  and  estimates.  1974),  parameters,  lower  for  A maximum l i k e l i h o o d  statistic  evaluate  criterion  were  plus  overall  more  suitable  model .  Table general  4.7.3.1  model.  lists  In b o t h  1985  both b a i t - e f f e e t i v e n e s s other were  models. clearly  b o t h the  1985  For  density  structure  of  relationships  Section  4.7.3  1986  and a g o n i s t i c  the  1985  and 1986  experiments  equations  size  Eqns. for  the  changes  These  4.7.3.3  four  Model  the  bait  of  outperformed a l l interactions  effectiveness.  considerable of  dynamic p r o c e s s e s  variability crabs  results  approximate  the  includes  a g o n i s t i c - i n t e r a c t ions  satisfactory 5  which  agonistic  distribution  and  variants  '4',  processes,  in  explain  frequency  treatments.  the  experiments  over  and  experimental  and  dominant  bait-effeetiveness the  A a n d AIC f o r  and in  among  the  suggest  the  the  they attempt  For  functional to  simulate.  Page  56  The  structure  estimation Eqns.  of  and  was  and  of  Schnute  inversion.  the  confidence  4.7.3.3  application  of  intervals  5,  and  approximate 1985)  Use  of  was the  p r o h i b i t e d by a  standardization  the  the  by  computer  estimates rates.  method  processing  of The  (Mittertreiner  problems  resampling  precluded  entry  techniques  frustrated  of  parameter  virtual  analytical  bootstrap  lack  for  model  with  matrix  (Efron  1982),  time.  Table 4.7.3.1. Comparison of different models explaining d e n s i t i e s and s i z e f r e q u e n c y d i s t r i b u t i o n s o f C . magi s t e r i n s e t s of t r a p s w h i c h e x p e r i e n c e d d i f f e r e n t soak t i m e s and b a i t ages during equivalent experiments i n 1985 and 1986. The objective f u n c t i o n ( A ) i s the s e p a r a t i o n s t a t i s t i c of S c h n u t e and F o u r n i e r (1980). P i s the number o f p a r a m e t e r s i n the m o d e l . AIC (see t e x t ) measures model p e r f o r m a n c e , the lower the v a l u e the more s u i t a b l e the model.  1985 Model  A  1. C o n s t a n t e n t r y r a t e s 2 . Agon i s t i c - i n t e r a c t i o n s b 3 . Bait-effectiveness 4 . 2 and 3 a b o v e 3  c  d  657 433 601 422  1986  P  AIC  A  20 22 22 24  697 477 645 470  736 549 545 469  P  AIC  18 20 20 22  772 589 585 513  T h i s model e x p e c t s t h e same e n t r y r a t e o v e r t i m e f o r e a c h The number o f c r a b s i n a t r a p i n c r e a s e s 5 mm CW i n t e r v a l . a s y m p t o t i c a l l y ( E q n . 4 . 7 . 3 . 1 w i t h R = 1 . 0 and R = 1 . 0 ) . T h i s model e x p e c t s d i f f e r e n t e n t r y r a t e s a n d s i z e f r e q u e n c y d i s t r i b u t i o n s over t i m e ( E q n s . 4 . 7 . 3 . 1 and 3 , R = 1 . 0 , R < 1 . 0 ) T h i s model e x p e c t s d i f f e r e n t e n t r y r a t e s a n d s i z e f r e q u e n c y d i s t r i b u t i o n s o v e r t i m e ( E q n s . 4 . 7 . 3 . 1 and 5, R = 1 . 0 , R < 1 . 0 ) T h i s model e x p e c t s d i f f e r e n t e n t r y r a t e s and s i z e f r e q u e n c y d i s t r i b u t i o n s over t i m e ( E q n s . 4 . 7 . 3 . 1 , 3 and 5, R < 1 . 0 and R <1 .0 ) . 1  2  2  1  1  2  1  2  Section  4.7.3  Page  57  Differences interactions and  1986. in  equation  may  reflect  distributions  of  the  higher  be  expected  to  for  the  crabs to  the  in  be  to  whereas with  in  the  4.7.3.5,  1986  odour  trail.  In  liquid  content  of  there  was  Section  little  4.7.3  crabs  mm CW.  Thus,  this  model  may a l s o  for  contrast, the  bait  current  in  1985 in  near less the upper  produce  of  mm CW,  the  1986  traps  are  difference  reflect  poor  crabs.  1985  and  1986  experiments  may were  Lemmens  Inlet,  in  8 m deep  water  Indian  Island.  Bait  rapidly bait  (44%)  bait-effeetiveness  upper  performed  dissipated to  between  water  were  currents  the  The  in  the  these  those  <130  4.7.2,  <135  4.7.3.4)  of  captured  so  might  from  2220  for  biases  experiments  different  Section  and  individuals,  were  calm  flushing  1985  experiments  probably diminished  greater  for  1985  estimates  experiments  1985  i985 size  size-dependent  i n the  probabilities  the the  percent  for  deep,  for in  C . magi s t e r  differences.  tidal  for  estimates  in  Fig.  4.7.3.3)  agonistic-  Forty-four  crabs  estimates  12 m  effectiveness of  the  retaining  habitat  of  the  explained  strong  because  of  parameter  (Eqn.  performed  15%  in  the  populations  account  crabs  for  differences  experiments.  crab retention  equation  Fig.  crab  parameter  captured  Different  due  smaller  1986  As  of  cannot  produce  parameter  estimates  of  only  ineffective  the  competitiveness  the  experiments.  in  4.7.3.3  density  obtained  compared  estimates  experiments  relative  1602  parameter  4.7.3.3,  Equation  the  the  (Eqn.  1986  frequency  in  and  near a  Lemmens  Indian more  Inlet,  Island  extensive once  the  or two day  soak  after  a one  an  effective  odour  trail.  Page  58  Further,  the  attracted  to  in the  smaller traps  absence  Figure  of  numbers  trap  as  rates, is  evident rate  the  crabs  function  both  for  any of  crabs  frequency  day soak  time  trials  within placed  in  frequency bait as  4.7.3.6  16 a  4.7.3.6  traps.  in F i g .  several crab  the  as  a  catch  rate  the  of  time.  for  response  numbers  of  the  zero for  the  does  the  bait  to  eight ninth  2,  plots  in  each  ages  (at  days. day  virtual  time = z e r o ,  5,  10  and  and  comparing  20  the The  was  as  the  5 mm CW i n t e r v a l time  bait  observed  obtained  effectiveness  appear  confounding  time  4.7.3.2.  in bait  not  1,  20  entry  over  The at  a  The p r e d i c t e d  surface  crabs  in  traps,  slope,  the  within  experiments.  is  function  of  reduction  i n the  compared i n F i g .  from  of  The  crabs  distributions  4.7.3.4,  are  possible  4.7.3  been  plots  5 mm CW i n t e r v a l  1986  representing  not  response  retention  Section  a high  have  size  with  over  is  no  time,  dramatically in F i g .  effects  of  agonistic  and e s c a p e m e n t .  Residuals of  may  surface  time.  and  The d e c r e a s e  because  interactions  plane  set  trap)  each  smaller  presents  distribution  i n the  shown  trap  1985  causing  response  soak  1985  are  and o b s e r v e d  a  in  thereby  5 mm CW i n t e r v a l  size  predicted  of  the  observed  Figure  in  number of  for  number  a refuge,  presents  of  a n d i n the  entry of  a  present  bait.  4.7.3.5  predicted set  as  crabs  randomly surface  reasons.  It  probabilities  distributed  in  Figs.  may for  (1)  above  4.7.3.2 reflect  and  a n d 6. poor  particular  below  the  There  are  estimates  carapace  of  width  Page  59  intervals,  (2)  reflect  interventions, interactions the  difficult  imperfect  unidentified  suitability evaluate  of  currents  u n d e r s t a n d i n g of processes,  processes.  the  since  tides,  and  In  is  other  agonistic-  (4)  indicate  particular,  a g o n i s t i c - i n t e r a c t ions  little  or  known about  the  the  equation  is  dynamics  of  interactions.  The  size  legal-sized Indian  frequency  males,  Island  experiments.  dynamic  were  Thus,  parameter  the  imperfect,  and  the  soak  Another  of  hard-  Legal-sized  males  are  following  moult  (see  Table  traps,  but  a  p e r i o d they  enter  crabs.  Figure  readily  enter  Section  4.7.3  4.7.3.7 or  survive  upper  the  bait  traps  the  effectiveness  estimates  the  traps.  agonisticequations  is  were  reduce  bias  introduced  soak  times  was  different  soft-shelled  crabs  within  for  4.10.1,  suggests in traps  used  types.  soft-shelled  are  to  this  to  model  samples  for  Inlet  modeling  commercial  both  the  considered  equations  and  of  in  Lemmens  were  including  different and  the  for  abundance  commercial  crabs  times and t r a p  of  and  experiments  model in  of  in  estimates  commercial  result  proportions  1986  parameter  standardizing  by d i f f e r e n t  than  changes  1986  typical  between  general  interactions  more  the  interactions  Although  distributions,  experiments  provide better  when  of  bait-effeetiveness  of  to  influence  indicate  and  presence  theoretical  such  (3)  the  page  vulnerable  the 80),  first  few  months  during  this  in contests with  hard  soft-shelled  and  traps.  crabs  containing hard-shelled  may  not  crabs.  Page  60  20 - i  10  -  0  c  nilOILn  -i  10  CX  0  i  i  i—r  ST 1985 ,-, n = l70  i_ CD  i  1 — I — I I  20  CD O  BE 1985 n = l40  E l  1  I  on I  DflilD  nT — i — i — r  o  "2  LLl ZD  o UJ  cr u_  20  - i  10-  BE 1986 n = 194  o-i—r 20-|  I  o  i  r  i  r  ST 1986  n = 223  io  OIiMiQi  DDII  nrin-. i—i—i—r—i—i—i—i i i n  82.5  102.5  122.5  142.5  162.5  182.5  CARAPACE WIDTH (±2.5mm)  Figure 4.7.3.1. Comparison of s i z e frequency d i s t r i b u t i o n s o f C . magi s t e r i n t r a p s s o a k e d 24 h i n t h e soak t i m e ( S T , 20 t r a p s ) and b a i t e f f e c t i v e n e s s ( B E , 16 t r a p s ) e x p e r i m e n t s i n 1985 and 1986. Female carapace widths are expressed as malee q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same body l e n g t h s .  Figure  4.7.3.1  Page  61  40 30  1985  1986  I D A Y S O A K  I D A Y S O A K  n «  n »  170  223  20  Mia  10 0 40  i  "i  r  2 D A Y S O A K  30  n =  20  «  10  1  i•  194  MB  v  0 40  T — — r  ~  30  n = 119  Q.  1  2 D A Y S O A K  n * 117  i  1  5  D A Y S O A K  20 • UJ  § LU  tr ^  10  o.  40  I  30  10 D A Y S O A K n = 145  20  i  i  r  10 D A Y S O A K n = 205  10 040 30 20  i  .n£8a*_  i  i  r  r  20 D A Y S O A K n = 209  20 D A Y S O A K n = 154  10 • 0 875 .  1125.  1375.  1625.  CARAPACE  187 5.  T  T  875 .  1125 -  WIDTH  1375.  1625.  T  1875 -  (±2.5mm)  Figure 4.7.3.2. S i z e f r e q u e n c y d i s t r i b u t i o n s o f C . magi s t e r for sets of 20 t y p e A traps with different soak times from equivalent experiments i n 1985 a n d 1986. Solid circles profile predicted size f r e q u e n c y d i s t r i b u t i o n s u s i n g Model '4' (Table 4.7.3.1). Female carapace widths are expressed as malee q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same body l e n g t h s .  Figure  4.7.3.2  Page  62  0  5  10 WEIGHT  15  20  25  30  RATIO  Figure 4.7.3.3. The r e l a t i v e rate at which C . magi s t e r e n t e r T r a p A , as a f u n c t i o n o f t h e r a t i o b e t w e e n t h e w e i g h t o f c r a b s i n a t r a p , and the w e i g h t o f t h e c r a b a t t e m p t i n g t o e n t e r the t r a p . T h i s p l o t uses the b e s t parameter e s t i m a t e s for E q n . 4 . 7 . 3 . 3 from Model ' 4 ' ( T a b l e 4 . 7 . 3 . 1 ) .  Figure  4.7.3.3  Page  63  rU UJ U_ U_  1985  LLl  5  0.8  -  °-  6 H  Y  =  0  EXPERIMENTS .  6  6  9  +  e -25-x _l  ( 1 . 0 - 0 . 6 6 9 ) -  00 UJ >  1986  0.4-  Y =0  EXPERIMENTS .  4  9  3  +  ( 1 . 0  -  0  .  4  9  3  • e"0.405-x  )  0.2UJ o r  0.0  n 0  1  2  1  3 BAIT  1  4 AGE  1  5  1  6  7  1  1  8  9  (days)  Figure 4 . 7 . 3 . 4 . The r e l a t i v e entry r a t e of C . magister i n t o Trap A as a f u n c t i o n of b a i t age. This p l o t uses the best parameter e s t i m a t e s f o r Eqn. 4 . 7 . 3 . 5 from Model '4' (Table 4 . 7 . 3 .1 ) .  Figure  4.7.3.4  Page 64  CARAPACE WIDTH (±2.5mm)  Figure 4.7.3.5. Response s u r f a c e o f t h e p r e d i c t e d changes i n t h e s i z e f r e q u e n c y d i s t r i b u t i o n o f C . magi s t e r w i t h i n 20 t y p e A traps, as a f u n c t i o n of time. These results use the best p a r a m e t e r e s t i m a t e s f o r E q n s . 4 . 7 . 3 . 3 and 5 from Model ' 4 ' ( T a b l e 4.7.3.1). Female carapace widths are expressed as malee q u i v a l e n t c a r a p a c e w i d t h s f o r t h e same body l e n g t h s .  Figure  4.7.3.5  Page  65  CARAPACE WIDTH (±2.5mm)  1986  CARAPACE WIDTH (±2.5mm)  Figure 4.7.3.6. Response surface of the predicted size f r e q u e n c y d i s t r i b u t i o n s o f C . magi s t e r w i t h i n 1 0 s e t s o f 1 6 t y p e A traps. E a c h s e t u s e d b a i t r a n g i n g i n age from z e r o t o e i g h t days, s o a k e d f o r one d a y . The b a i t was removed f o r t h e ninth day. The v e r t i c a l l i n e s show t h e o b s e r v e d d a t a f o r a p a r t i c u l a r combination of bait age and c a r a p a c e width, for differences g r e a t e r than one. T h e s e r e s u l t s use t h e b e s t p a r a m e t e r e s t i m a t e s f o r E q n s . 4 . 7 . 3 . 3 a n d 5 from N o d e l '4' (Table 4.7.3.1). Female c a r a p a c e w i d t h s a r e e x p r e s s e d as m a l e - e q u i v a l e n t c a r a p a c e w i d t h s f o r t h e "same b o d y l e n g t h s .  Figure  4.7 . 3 . 6  Page 6 6  22  50  -i S.D.  \~ 40 u_  O  CO  30 -  UJ  20  or UJ  I  39  -z. 10 0 0  \  2d  ~~\  \  60  62  r~  1  5 SOAK  10 TIME  15  20  (days)  Figure 4.7.3.7. The p e r c e n t of s o f t - s h e 11ed legal-sized male C . m a g i s t e r i n T r a p A , as a f u n c t i o n o f soak t i m e . These r e s u l t s were o b t a i n e d from t h e soak t i m e e x p e r i m e n t p e r f o r m e d near I n d i a n I s l a n d ( H ; F i g . 2 . 1 , page 9) i n 1986. Above t h e S . D . b a r s i s t h e number o f l e g a l - s i z e d m a l e s c a u g h t i n 20 t r a p s .  Figure  4.7.3.7  Page 67  4.8  TRAP DISTRIBUTION  Figure of  traps  Figure Inlet  4.8.1b  fished 4.8.1a  as  specific  compares  with  the  documentation  Section  at  determined  interviews suggests  presents  4.7.3  the  time of  (1)  the by  time sites  trap  profiles  throughout  number counting  fishermen.  series  series  the  in  traps  the  t r a p buoys  Fig.  fished  4.8.1b  the  number  main s t u d y  of  The s i m i l a r i t y o f  profiles  for  in  and,  area.  Lemmens (2)  from  the  assessments  are  an  accurate  distributions.  Page  68  1000-1  • TRAP COUNT • INTERVIEWS WITH FISHERMEN  800 600400cn Q<  200  cr  o-h—T  i—i—I—i—i  i—i—r  o  cr LU CD  2000 -j 1600 1200-  • o A • •  i—r—i—r  STUDY SITE (excluding o,a,• ) LEMMENS INLET ( A- D) INDIAN ISLAND (H) BROWNING PASSAGE ELSEWHERE ' l  G  )  !  800 400-  M J J A S O N D l J F M A M J  1985  i I r J A S O N  1986 DATE  Figure 4.8.1. ( A ) Time s e r i e s c o m p a r i s o n o f t h e number o f t r a p buoys c o u n t e d i n Lemmens I n l e t , and t h e number o f traps estimated by interviewing fishermen. (B) Time series of the number of traps estimated by interviewing fishermen. The ' E l s e w h e r e ' c a t e g o r y i n c l u d e s t r a p s f i s h e d o u t s i d e the study area i n S t a t i s t i c a l A r e a 24 by f i s h e r m e n who a l s o f i s h i n t h e study area. The c a p i t a l l e t t e r s i n p a r e n t h e s e s i d e n t i f y t h e s e a r e a s i n F i g . 2.1 (page 9 ) .  Figure  4.8.1  Page  69  4.9  COMMERCIAL EXPLOITATION OF MALES  I the  define  the  proportion  This  of  proportion  which  measured  instar,  as  influence  degree males  was  the  the  183.8 this  4.9.1,  is  little  there  of  the  128.0  smaller  the  size  distributions this  which  I  exploited  155.0  were  size  because evident  by  measures  the  difference  size  frequency  of  low  in  Fig.  mm a n d t h e  next  in  abundance  reduce  the  influence  confidently  measured,  on  a  subset  continually  define  The  lower  to  males  4.9.1.  remaining  performed  Since  1 5 5 . 0 mm  mm i n s t a r  considerably  less  instar. analysis  the  Fig.  As  155.0  is  mm  as  and  not  by  of  the  moult  into  cohort,  between  the  recruitment  exploitation.  Before  performing  exploitation  of  distributions  were  different model  soak  which  experiments 4.7.3.3 near  mm CW.  in  4.13).  the  abundance  from  unimportant  Nevertheless,  analyses  >145  instar,  proportion and  whose  with  males  frequency  missing  between t h e  when  mm i n s t a r .  frequency  155.0+11.2  size  males  (Section  overlap  even  instars,  a  is  legal-sized  the  using  mm i n s t a r  instar  distinct  of  diagrammatical1y  1 2 8 . 0 + 1 0 . 5 mm i n s t a r ,  relatively  from  p r o p o r t i o n of  to  than  missing  described  of  exploitation  estimated  survivorship  smaller  of  Section  the  4.9  155.0  This  analyzed (Section  Island  mm  instar,  standardized  times.  and 5 ( p a g e s  Indian  the  the  was  55 a n d 56) used.  The  the  minimize  done  soak  4.7.3).  were  to  analyses  using  time  the  parameter  obtained The  size  bias  and  for  unknown  measuring frequency  introduced  results  from  by the  bait-effectiveness estimates the  1986  for  Eqns.  experiments  parameters  are  Page  the  70  'virtual crab  entry  rates '  retention  appropriate to  for  for  each  trap  the  of  estimates yielded soak  traps for  the  sample.  the  most  in  effectiveness and  of  Fournier  sample. were  distribution,  after  the  of  that  the  of  soak  separation  was  used  to  used  traps.  The  crabs  into  The  rates  resembled  was  of  entry  the  (1980),  and e x i t  accepted  those  which  appropriate  the  commercial  time  and  statistic  evaluate  of  interval)  47)  from  commercial  analysis  experiments,  page  crabs entry  virtual  closely  the  the  The v e c t o r  5 ram CW  4.7.2.2,  of  the  frequency  which  As  Schnute  vector  each  (Table  simulated  comprising  size  time,  type  (for  escapement  s t a n d a r d i z a t i o n model set  5 mm CW i n t e r v a l .  probabilities  estimate  the  each  bait  'A'  the  of  parameter  est imates.  Figure C.  4.9.2  magi s t e r  August  taken  1986.  plots by the  at  habitat,  exploitation  60-90%.  exploitation  response  If  to  fishing  the  1985  expect 155.0  than  an  increase  mm i n s t a r  S e c t i on  4.9  for  upper near  in  dates  legal-sized  from A p r i l  rapidly  100%. of  1985  summer  of  Lemmens  harvesting  until  1986  1985  spring  Inlet, This  a  and  in  a  male until  1985  and  poorer  rapid  crab  increase  previously  in  unavailable  1986.  The number  (Fig.  4.8.1b,  of  page  traps 69)  in  success.  and  in  percent  increased  was  abundant  steadily  abundant  In  suggests  mm i n s t a r  increased  fishery  Exploitation  remained  155.0  the  the in  over  1986  155.0  mm  immediately abundance this  of  period.  instars  preceding  were  more  one  would  years,  sublegal-sized Figure  indeed  4.9.3  males shows  in  the  that  the  Page  71  virtual  entry  doubled.  Because  recruitment suggesting 1982  rates of  rate  may have  but  not  shows  legal-sized  males  caught  during  Outside  Lemmens  constant  throughout  Inlet  probably  rates 69)  there  and  short  of  abundance  In  contrast,  observed, in is  is  being  (Fig.  For Island the  in  spring  fishery  adjacent this catch  the  of  the  (Fig.  greater,  this  area  in  soak  day)  in  Lemmens  summer and was  poor  in  winter.  of  The  abundance  since  a  4.9.4)  lower (often  thought  4.8.1b,  the to  increased  page  69)  i.e.  least  year-class  Effort  between  effort, at  in  pattern outside  similar of  which near  from may  response  to  and  that Inlet catch  density  times.near  Indian  recruitment  have  Indian  to  trap  catch rate  result  4.9.5.  Lemmens  lower  page  pattern  in F i g .  a week) soak  high  4.8.1,  abundance a  Lemmens  seasonal  standardized data seasonal  in  exploitation  (Fig.  A similar  of  relatively  observed  relationship  1983  remained  pattern  times.  (Fig.  is  per  a high trap density  soak  by  1986  the  number  success  e x p l a i n e d above,  mudflats.  time  i.e.  and longer  reasons  much in  success  traps  relative  Inlet  disguised  4.8.1)  year.  absence  to  probably  4.13),  (the  fishing  s u g g e s t e d by t h e  p r o b a b l y due  rate  100  s p r i n g and  days)  Lemmens  approximately  (Section  settlement  fishing  per  the  high,  the  was  larval  that  reflects  (1-2  period  been  Inlet  were  mortality  CW  i n . 1981 .  4.9.4  increased  145-155 mm  natural  this  Figure  Inlet  males  high  over  there  and 1 9 8 3 ,  for  settled Island  the  to on  about  increased  rate.  S e c t i on  4.9  Page  72  LEGAL SIZE  CARAPACE  WIDTH (mm)  Figure 4.9.1. Diagram explaining how the degree of e x p l o i t a t i o n o f male C . m a g i s t e r i n t h e 1 5 5 . 0 + 1 1 . 2 mm i n s t a r was estimated. The p r o p o r t i o n e x p l o i t e d (A+[A+B]) was d e t e r m i n e d bysize frequency a n a l y s i s .  Figure  4.9.1  Page  73  100 - i Q UJ  ®S .®.®®®® )  <D®®  (5)  80 -  O  Sc  60  ®  UJ  40 UJ  o  or  20 -  •  ®  TRAP TYPE A  •  ®  TRAP TYPE B  UJ Q_ o  --—i—l—i—I—l—l—I—I—I—I—I—l—l—l—l—I—l—l—f  A M J  J A S O N D ' J F M A M J J A S 19 8 5 1986 DATE  F i g u r e 4.9.2. The p e r c e n t o f l e g a l - s i z e d male C. magi s t e r removed from t h e 1 5 5 . 0 mm i n s t a r b y f i s h i n g , as d e t e r m i n e d by size frequency analysis of trap samples. The e n c i r c l e d data p o i n t s a r e f o r upper Lemmens I n l e t . The r e m a i n d e r a r e f o r t h e r e s t of the study a r e a .  Figure  4.9.2  Page  74  • TRAP TYPE A • TRAP T Y P E B  l—I—I—i—l—l—I—l—l—I—l—l—l—I—I—I—I—I—I  A M J J  A S O N D ' j  1985  DATE  F M A M J  JA S  1986  Figure 4.9.3. Linear r e g r e s s i o n of v i r t u a l entry rates of male C . magi s t e r 145-155 mm CW i n t o t r a p s o v e r t i m e . D a t a from upper Lemmens I n l e t , a poor c r a b h a b i t a t , a r e not i n c l u d e d i n this plot.  Figure 4.9.3  Page 75  2 0 0 - i CO CL D 1 0 0 -  •  STUDY A R E A (excluding A-D.H)  •  INDIAN  ISLAND (H)  O O 0  QJ h<  2 0 0  i—i—i—i—i—i—i—i—r  UPPER LEMMENS INLET (A)  - i  or x  o  T—i—i—i—i—i—i—i—I  MIDDLE 8 LOWER L E M M E N S  INLET  1 0 0 -  i<  o  i—i—i—r  A M J  J  A S O N D l J  1985  F M A M J  J A S  1986 DATE  F i g u r e 4.9.4. Time s e r i e s of commercial catch r a t e s of l e g a l - s i z e d male C. magi s t e r . The c a p i t a l l e t t e r s i n parentheses i d e n t i f y these areas i n F i g . 2.1 (page 9 ) .  F i g u r e 4.9.4  Page 76  I  • TRAP TYPE A to  Q. D  250  O O 200  • TRAP  TYPE B  A TRAP  TYPE D  H  UJ h<  150 H  or >rr  100  A  • A  UJ  A A A  50  _i <  Z>  •  A  0  i-  1  I  I  I  A M J J  >  I  I  I  1  1  1  1  A S O N D ' j 1 9 8 5  1  1  1  1  F M A M J 1  9  8  1  1 1  1 J  A  S  6  DATE  Figure C. m a g i s t e r a poor crab  Figure  4.9.5  4.9.5. Virtual entry rates of legal-sized i n t o t r a p s over t i m e . D a t a from upper Lemmens h a b i t a t , a r e not i n c l u d e d i n t h i s p l o t .  male Inlet,  Page  77  4.10 MALE MATING ACTIVITY Figure marks  4.10.1  (Butler  ranging  occur  a  approach  mating  and  size,  periods  marks  is  less samples  a  measure  instar, of  mating  activity  approximates  larger  instars  predominately this  instar  Since  on  is  Figure sublegal-  are  in  mating  occurrence  marks on  using  4.10  occur  legal-  was on  155.0 most  the  males.  McLeod-Hipel  collected  after  males  with  males  in  eventually width  mate.  intervals  Since mating  a  of  the  males  in  marks  are  suggesting  that  activity.  mating  1985  1986.  mm CW,  the  To  compare  the  a time  percent by  intervention (Hipel  August  of  <140  males,  males  activity  until  males  d i v i d i n g the  algorithm  of  of  140-154 mm CW.  An  CW  They  males.  the  relative  sublegal-sized  male  legal-sized  73).  and s u b l e g a l - s i z e d by  a  males  mm i n s t a r ,  on  by  distribution  page  mating  intervals  as  carapace  from J u l y  males  mm  will  4.13),  mating  mating.  percent  normal  4.9.1,  in  number  that for  5 mm  males  the  infreguently  obtained  legal-sized the  males  includes  of  ratios  for  compares  marks  category  mating  the  for  of  caused  *120  the  the  (Section  responsible  mating a c t i v i t y  Section  males  and l e g a l - s i z e d  sublegal  1986),  rare  4.10.2  mating  Fig.  for  are  include  d i s t r i b u t i o n of  (see  marks  above  interval  size  males  involvement  width  legal  occurrence  frequently  i n an  1 5 5 . 0 + 1 1 . 2 mm i n s t a r  of  Mating  time  not  of  carapace  below  of  claws  frequency  the  of  percent  indicate  then  because  particular The  female  legal  different  the  increasing  that  the  120-190 mm CW.  with  Note  1960 ) on  from  embracing  profiles  series  occurrence  their model  and McLeod  percent (Noakes 1987),  Page  78  revealed  no  comparing a  significant  1985  student's  that  the  T-test  lower  effort  (Fig.  page  74)  caught  (from  Section  days,  near  mate  which  were  are  is  and  from  crabs,  they  in  possibly  of  observed  Section  4.10  marks  1986.  exploitation opportunity for  for  study  and 1986.  Most  an  shallow  water  from  nearby  the for  of  condition,  estimated  They local small  do  the  of  near  the  deeper, not  to  rates  so  s h a l l o w water (first-year)  Fig.  four  <10%  sheltered, the  to  crabs  The to  4.10.3)  included  when  h a r d - s h e 11ed,  Fig.  These briefly  2.1,  habitat and  Similar  (Section  for  mate.  (Fig.  moulting  population.  of  enough  years,  (F;  they  4.10.2.  males  were  90  4.10.2  moulted r e c e n t l y .  coast  most  series  high  not  crabs  (Fig.  survive  time  be  in  M = 3.48-4.48  on  Fig.  was  least  more  males  harden before  the  can  these  reflect  and  i n Kay 1986  open  ratio.  means  males  legal-sized  at  1985  rate  occurred  of  h a d not  age  conclude  legal-sized  evident  area,  to  corroborates  mating a c t i v i t y  the  shell  shell  Covariation  that  Therefore,  used  legal-sized  is  when  ar.d e x p l o i t a t i o n  generally  hardness  of  by  analysis  and  the  wintered.  activity was  their  with  appeared 9),  1985  This  mating  was  69)  series  4.10.3).  With F = 5.11-6.90  their  4.10.1).  time  A high exploitation  for  typical  comparing  higher.  in  1981)  page  needed  The h i g h r a t i o not  4.8.1b,  time  males  (Fig.  mating a c t i v i t y  s o f t - s h e 11ed.  that  i n the  *29% ( p < . 0 0 1 ) o f  of  markedly reduce  is  was  6-12%  marks  implication  1986  Rohlf  only  (Table  legal-sized  and  4.13),  the  shows  mating  (Sokal  suggests  males  can  mating r a t i o s  for  when  4.9.2,  and 1986  mean r a t i o  This 1986,  autocorrelations  page where  mating movement  4.11).  Page  79  Table 4.10.1. The p e r c e n t o f male C . magi s t e r , t a g g e d when s o f t - s h e 11ed, which were hard-shelled when recovered. The r e s u l t s a r e r e p o r t e d f o r 30 day i n t e r v a l s o f t i m e - a t - l a r g e . The carapace widths of r e c o v e r e d males were a p p r o x i m a t e l y n o r m a l l y d i s t r i b u t e d ( 1 5 3 . 4 + 6 . 0 mm) and r a n g e d from 135-173 mm.  Time-at - large  (d )  1-30 31-60 . 61-90 >90 a  1 S . E . of  Section  the  4.10  Sample 31 20 23 56  size  Percent  hard-she l i e d  32.3+ 8.4 60.0±11.0 91 .3+ 5.9 100.0  a  estimate.  Page  80  CO  cr <  5 0 -.  4 0  -  3 0  -  S.E  o  X t  2 0  CD  II  h-  in  10  UJ  o rr  UJ  o_  O  ii  c  —  CO  CO  ro  n c  n c  0 122.5  132.5  142.5  CARAPACE  152.5  162.5  WIDTH  172.5 182.5  (± 2.5mm )  Figure 4.10.1. The percent of male C. magister w i t h mating marks ( B u t l e r 1960) as a f u n c t i o n of carapace w i d t h . The minimum l e g a l s i z e l i m i t i s ==154 mm CW.  Figure  4.10.1  Page 81  100  -i  80 60 UJ  (J  rr UJ  40  Hard shell  D_  Legal-sized males.with mating marks  20  Sublegal-sized males with mating marks 33  1  A  1—I M J  1—I J A  1 S  I985  O  1—I N  1 D  I  1 J  1 F  DAT E  I M  1 I A M  1 J  I  1 1—I J A S  1986  Figure 4.10.2. Time s e r i e s of the percent of hard-shelled l e g a l - s i z e d ( > 1 5 4 mm CW) m a l e , l e g a l - s i z e d m a l e w i t h m a t i n g m a r k s (Butler 1960), and sublegal-sized ( 1 4 0 - 1 5 4 mm CW) male C. magi s t e r w i t h m a t i n g m a r k s . E x c e p t where noted, a l l sample s i z e s a r e >100 c r a b s .  Figure  4.10.2  Page  82  0.5-1  0.4I<  rr  1985 MEAN=  0.3-  0.2 -  0.1 -  1986 MEAN =. 0 9 6  0.0--—i—|—i—i—i—\—i—i—r A M J J A S O N D l j  F M A M J J  A S  1986  1985 DATE  Figure 4.10.3. Time series i n d i c a t i n g that the relative l e v e l o f m a t i n g a c t i v i t y by l e g a l - s i z e d male C . magi s t e r i n 1986 was =*29% of t h e l e v e l i n 1985. The s u b l e g a l : 1 e g a l m a t i n g r a t i o i s o b t a i n e d by d i v i d i n g t h e p e r c e n t of l e g a l - s i z e d males w i t h m a t i n g marks by t h e p e r c e n t o f s u b l e g a l - s i z e d males w i t h m a t i n g marks. The r a t i o f o r May 1986 was e x c l u d e d from t h e c o m p a r i s o n for reasons g i v e n i n the t e x t .  Figure  4.10.3  Page  83  4 . 1 1 SPATIAL AND TEMPORAL DISTRIBUTIONS Beam  trawl  surveys  C. magi ster except 46 beam trawl old  in  i n the  samples,  1985  selected  one  year  (*75-145 mm CW) crabs  1984)  were  found at  differences, and  were  and d i f f e r e n c e s  females.  Note  reported d e n s i t i e s  that  1986  collected  locations  few  small  c o n s i d e r e d below.  In  o l d ( « 4 0 - 7 5 mm CW) and two year  (Butler  densities  Where higher d e n s i t i e s  and  1961,  Stevens  generally  found,  less  and  than  there were  Armstrong  10  ind-ha" . 1  important  seasonal  i n the r e l a t i v e p r o p o r t i o n s of  beam t r a w l s  are  not  males  100% e f f i c i e n t ,  so  are o n l y an index of abundance.  A peak i n abundance of male and female one year o l d crabs on the  shallow  1985  (Fig.  result the  sand bottom of 4.11.1b).  of movement  1984  declined  into  quickly,  but  and  some  (Fig.  through 1986 suggesting The Inlet  the  initially  low  (Fig.  4.11.2a).  This  upper Lemmens I n l e t  highest  (Fig.  winter,  male  Section  4.11  density  4.11.2b). densities  suspected  outer  moved  i n summer to  to  the  be  page 9)  coast.  4.11.1a).  in  of  summer  cohort was  the of  Abundance entrance  of  S i m i l a r movement  is described in Section  densities  were  occurred  (E; F i g . 2.1,  on the  may have  by December 1985  upper Lemmens I n l e t  females  is  shallower water  l a r g e r crabs i n t o shallow water In  shore  occurrence  y e a r - c l a s s which s e t t l e d  Lemmens I n l e t of  Their  an exposed  two year 1985  4.10.  o l d males  and  declined  abundant  elsewhere  i s poor crab h a b i t a t .  of males was observed i n middle Lemmens During  autumn  steadily  1985  increased  and to  the  subsequent  >1200 i n d - h a " * .  Page 84  Toward  the  mouth  declined  (Fig.  year  males  the  old  number  movement have  The rapidly  after  males  middle  (page  study  legal  were  69)  was  the  at  4.11.2c).  during  autumn  Lemmens  movement. where  the  Sect i o n  generally  two  the  to  could  because  three  increase be  of  in  due  during winter.  to  They may  poor  next  of the  the  Inlet  that  i n an  25-35%  the  habitat  year  declined  after  to  Lemmens  out  to  of  the  was  effort,  after  moult,  page  to  105).  observed  in  June  the  in  date,  but  increased  (Fig.  4.11;2d)  Female d e n s i t y  abundance  spring  years to  in  Inlet  Inlet  decline  female  three  F i g . 4.13.3,  this  1986, Figure  during  continued  Lemmens  in  fishery.  Inlet  females  128.0 mm  size  fishing  about  narrow c h a n n e l .  continued  main c h a n n e l  of  the  and  (see  old  end  entrance  of  decreased  i n the  legal  Lemmens  1986),  two  in  were  intense  fishery  months  lower  increase  in  6-9  the  Lemmens I n l e t  and m o u l t e d t o  spring  Density in  The  4.11  low,  Most males  caught  enter  0 . 5 - 1 . 0 km s e a w a r d o f up  of  Inlet  i n middle  concentrated  density  channel  41)  suggests  (in  for  males  soon  settlement  narrow  Lemmens  s h a l l o w water  page  to  A high  consistently  s p r i n g 1986.  4.6.3,  area  size  (Fig.  of  M a l e s began  larval  densities  densities  i n m i d d l e Lemmens I n l e t  late  which they  1986.  in  high density  (Table  4.8.1b the  were  male  inlet.  during  instar  Because  from e x p o s e d  up t h e  Inlet  elsewhere  concentrated  further  Lemmens  4.11.2c,d).  of  away  of  suggesting in  further seaward  September  s t u d y a r e a meets t h e  1985  open  1986 coast  Page  85  (Fig.  4.11.1c)  females 149.4  were  Despite of  appears mated  in  was  all  females  that  4.3.1,  page  a  relative  assessed  after  a  by  trap  4.11.3)  of  abundances  of of  the  beam  trawls  >145  mm CW m a i n l y  Females et  al .  weak  in  the  this 1985 ) ,  1981  so  of  in  135.5  because  and  have  may have  Section  resulted  a  as  4.11  from  the  percent were  females  in  at  instar  for  width,  were  the it were  smaller females  of  obtained  149.4  The  from  4.11.1  instars  four  mortality  catch  rates  in  more  was  samples a  larval  near  reports  the  high in  on. f e m a l e s  five  years  rate  (M>2.0,  1986  may  Indian Island  main  collected  old.  Hankin  indicate  (page  male and female  settlement  observed  where  i n t e r p r e t e d from F i g . 4 . 9 . 3 of  in  actively  i n the  were  and  area  abundant  highest  4.11.1)  mm i n s t a r s  study  most  1986  Table  high  the  forage  and  (Table  1986.  lower  i n beam t r a w l  and  4.11.2c)  next  data  they  1985  The r e l a t i v e l y h i g h d e n s i t i e s collected  135.5  channel  (Fig.  the  eggs.  area  representing  year-class,  the  the  the  Females  spring  study  the  to the  larger  incubating  September  size  in 1985  of  carapace  perhaps  females  out  summer  sampling.  of  in  These  location.  abundance  winter  abundance channel  near t h i s  females  documents  of  females.  42).  Most  which  of  mainly  moulted  29).  function  (Fig.  of  during  as  were  page  density  4.3.1,  spring  and  Inlet  collected The  old  Fig.  inseminated crabs  high  Lemmens  (Fig.  years  s e a w a r d movement  (Table 4 . 6 . 4 ,  the  that  females  suggests  three  instars  mm  mouth  also  a  75).  C. magi s t e r  (Table  4.11.2)  on n e a r b y m u d f l a t s  in  Page  86  1983.  In  density  contrast  decreased  Females  may  Passage,  Tables male  female  suggestion  of  recoveries  from  only  Only  two  main  male,  study  and  movement female  previously recovered  on  no  local of  explained  they  than  by  4.11  41  and  The o n l y number  of  Lemmens  probably also  results  of  page  Island  Inlet.  outside  traps 69),  the  fished  suggesting  Similarly,  is  and  Lemmens  from  area.  males,  male  upper  upper  4.8.1b,  male  restricted, 20  of  as  21  females,  indicate  limited  tagged.  Males and  females  and  20 m p e r  random d i s p e r s i o n  whose  gross  also moved day,  model  moved by males  following  large  were  moved  population  the  in  distances  30  tagged.  this  study  recoveries  were  number  Indian of  and  of  water  Browning  Most  habitat  being  the  were  mean d i s t a n c e s a  area.  poor  (Fig.  35  mean  d e s c r i b e d by the  Section  with  Island  is  large  from  near  Indian  releases  1986.  deep to  recoveries  a  fishermen  4.11.4).  less  female,  crabs  of  the  effort  but  male  to  access  they  However,  despite  two-dimensional  h i s t o g r a m of  are  and  where  (Fig.  average,  simple  fishing  surmised, near  in  1985  respectively.  where  Island  easy  tag  movement  inlet.  movement  Histograms movement  of  area  ' e l s e w h e r e ' by little  summarize  tagged  from  habitat,  the  magi s t e r .  Indian  density  prevent  o c c u r r e d near  down the  near  coast  them t o  4  C.  males,  2.8%  female  may  directional  of  lower  and  female  Inlet,  open  Island  4.11.3  and  to  confining  recoveries  Inlet,  an  Indian  thereby  Lemmens  relative  prefer  surrounding  of  to  log-normal  distance),  respectively. estimated  (Fig.  movement  (net  4.11.4) rates  that could  (in  A the be  m-d" ) 1  distribution.  Page  87  G = 280-exp(l.1-v) where:  G  (4.11 .1 )  i s a p o i n t on t h e d i s t r i b u t i o n o f d a i l y movement r a t e s ( m - d " ) i s a random n o r m a l d e v i a t e w i t h a mean of 0 and a s t a n d a r d d e v i a t i o n of 1 1  v  Approximately the  above  o f males  distribution  10 km f r o m t h e i r environment, habitat  22%  o f movement  point of release  assuming  whose movement rates after  no m o r t a l i t y .  one y e a r  travel  the percent  l e a v i n g the  lower.  >145 mm CW i n  Female abundance (n • 1 0 0 • t r a p " • s o a k d a y " ) 1  '.  than  i n a n unbounded  T a b l e 4.11.1. A b u n d a n c e o f f e m a l e C . magi s t e r c o m m e r c i a l t r a p s i n May a n d J u n e o f 1985 a n d 1 9 8 6 . A r e a Sampled  more  B e c a u s e o f g e o g r a p h i c a l and  b o u n d a r i e s , and h i g h m o r t a l i t y ,  s t u d y a r e a i s l i k e l y much  would  i s d e s c r i b e d by  'J  Upper Lemmens I n l e t ( A ; F i g . 2.1) Lemmens I n l e t (B-D; F i g . 2.1) B r o w n i n g P a s s a g e ( G ; F i g . 2.1) Near I n d i a n l i s ! a n d ( H ; F i g . 2.1) M a i n c h a n n e l ( F ; F i g . 2.1)  1  1985  1986  7 15 22 10 429  13 8 4 36 138  Table 4.11.2-. D e n s i t i e s of two to three («=75-145 mm CW) C . "irnag i s t e r f r o m beam t r a w l s a m p l e s I s land . ,;  year old near I n d i a n  :  Date  ">.  Dens i t y •  20 J u n 198!5 1-7 O c t 1985 8 May 1986  S e c t i o n 4.11  Male 155 96 70  ( n • ha"  1  )  Female 117 172 99  Page 88  Table 4.11.3. Summary of t a g r e c o v e r i e s , by l o c a t i o n , of s u b l e g a l - and l e g a l - s i z e d male C . m a g i s t e r between A p r i l 1985 and A u g u s t 1986. The number o f t r a p h a u l s was d e t e r m i n e d by interviewing fishermen. Only records from f i s h e r m e n whose e f f o r t was known a r e reported. E x c e p t where n o t e d , r e c o v e r i e s were from w i t h i n t h e s t u d y a r e a as d e f i n e d i n F i g . 2.1 (page 9 ) .  L o c a t i o n where c r a b s were tagged  Number o f r e c o v e r i e s (Mean d a y s - a t - l a r g e ) Trap hauls n  Number Tagged Where tagged  Upper Lemmens I n l e t (A; F i g . 2 . 1 ) M i d d l e Lemmens I n l e t (B; F i g . 2 . 1 ) Lower Lemmens I n l e t ( C D ; F i g . 2.1) Browning P a s s a g e ( G ; F i g . 2.1 ) Near I n d i a n I s l a n d (H; F i g . 2.1 ) Rest of s t u d y a r e a (Fig. 2.1) Elsewherek Total a  b c d  2234  ( 2 .8 )  1686  8655 (11 .0)  1653  16165  ( 20 .5 )  595  1053  ( 1 .3 )  85  9606 (12 ,.2 )  166  25294 (32 ,.1 )  215  15729 ( 20 ,.0) 78736  0 4400  Up Inlet  Down Inlet  116 189 (157) (93 ) 132 68 263 (116 ) (132 ) ( 1 7 0 ) 17 86 (118 ) (143 ) 7 14 (173 ) (125 ) 35 (154 ) 63 2 (151 ) (166 ) -  -  -  Toward Open Ocean  9  Toward Toward Browning Indian Passage Is l a n d T o t a l  -  -  306  -  -  463  34 (156 ) 4 ( 219 )  7 (102)  -  144  -  6 (124 ) 2 (135)  l ( 545 ) c  d  -  -  -  These a r e a s a r e e x p r e s s e d r e l a t i v e t o the a r e a where t h e c r a b s were t a g g e d . A dash i n d i c a t e s an i n v a l i d c a t e g o r y f o r a s s e s s i n g t a g r e c o v e r i e s i n t h i s m a n n e r , not z e r o recover i e s . O u t s i d e t h e s t u d y a r e a but s t i l l i n SA 24. Recovered o u t s i d e the study a r e a . One male r e c o v e r e d o u t s i d e t h e s t u d y a r e a a f t e r 370 d a y s a t l a r g e .  Section  4.11  0  25  -  41  -  67  -  1046 (-) (0)  Page  89  Table 4.11.4. Summary o f t a g r e c o v e r i e s , by l o c a t i o n , o f f e m a l e C . magi s t e r between A p r i l 1985 and A u g u s t 1986. The number of t r a p h a u l s was d e t e r m i n e d by i n t e r v i e w i n g f i s h e r m e n . Only r e c o r d s from f i s h e r m e n whose e f f o r t was known a r e r e p o r t e d . A l l r e c o v e r i e s were from w i t h i n t h e s t u d y a r e a as d e f i n e d i n F i g . 2.1 (page 9 ) .  L o c a t i o n where c r a b s were tagged  Upper Lemmens I n l e t (A; F i g . 2 . 1 ) M i d d l e Lemmens I n l e t (B; F i g . 2.1) Lower Lemmens I n l e t (C,D; F i g . 2.1) Browning P a s s a g e (G; F i g . 2 . 1 ) Near I n d i a n I s l a n d (H; F i g . 2 . 1 ) Rest of s t u d y a r e a (Fig. 2.1) Elsewhere* Total 5  a  b  Number o f r e c o v e r i e s (Mean d a y s - a t - l a r g e ) Trap hauls n (X)  Number Tagged Where tagged  ( 2 .8 )  495  8655 (11 .0 )  540  16165  (20 . 5 )  334  1053  (1 .3 )  12  9606 (12 .2 )  147  25294 (32 .1 )  635  15729 (20 .0 ) 78736  0 2163  2234  6 (125 ) 13 (97) 6 (96 ) 0 20 (283 ) 41 ( 230 )  -  Up Inlet  Down Inlet  -  11 (112 ) 4 14 ( 56 ) (179 ) 2 (91 ) 1 (68 )  1 (40 )  -  Toward Open Ocean  3  Toward Toward Br owning I n d i a n Passage Island Total  -  -  -  17  -  -  -  31  -  12  4 (197) 0  -  -  -  -  -  -  0  4.11  1  1 ( 518 ) 1 (57)  -  21  -  43  -  -  125  These a r e a s a r e e x p r e s s e d r e l a t i v e t o the a r e a where t h e c r a b s were t a g g e d . A dash i n d i c a t e s an i n v a l i d c a t e g o r y f o r a s s e s s i n g t a g r e c o v e r i e s i n t h i s m a n n e r , not z e r o recover i es. O u t s i d e t h e s t u d y a r e a but s t i l l i n SA 24.  Section  0  -  (-) (0)  Page  90  (45-75mm CW) 300 - i ~  0 300 0  >h-  ENTRANCE TO LEMMENS INLET  A  i  1—r -j  T — i — i  i—r  l  SHALLOW SAND BOTTOM  B  i—i—i  l—r  i  r  T  i  (D)  i  i  r  (E  i  r  co  -z. U J  (75-l45mm CW)  Q  m 600 < rr o  MAIN CHANNEL (F) > MALE • FEMALE  300 0  c _i M  J  l l J A  I—f S O N  1985  D I J F M A M J DATE  1986  J  I  A S  I  F i g u r e 4.11.1. Time s e r i e s o f d e n s i t i e s f o r one y e a r o l d (»40-75 mm CW) male and f e m a l e C. magi s t e r i n t h e e n t r a n c e t o Lemmens I n l e t ( A ) , and on t h e s h a l l o w sand b o t t o m o f an e x p o s e d s h o r e ( B ) . Time s e r i e s o f d e n s i t i e s o f two t o t h r e e y e a r o l d (»75-145 mm CW) male and f e m a l e C. magi s t e r i n t h e main c h a n n e l out t o s e a ( C ) . The capital l e t t e r s i n parentheses identify t h e s e a r e a s i n F i g . 2.1 (page 9 ) .  Figure  4.11.1  Page  91  UPPER  300  L E M M E N S INLET  i—i—i—i—i—r 1500-1  MIDDLE  ^  LEMMENS  (A)  i  INLET  f  i  i  i  i r  (B)  1200-  ~  900-  600'  • MALE • FEMALE (75-145mm CW)  300-  B  CO  T  1  1—I  1—I  1 LOWER  1  1  1 1 LEMMENS  1—I 1 I INLET ( C )  i—i—i—i—i—i—i—|—i—i—i 6OO-1  ENTRANCE  TO L E M M E N S  INLET  I  i—i—m  I  I  I—I  (D)  300  DATE  F i g u r e 4.11.2. Time s e r i e s of d e n s i t i e s f o r two to three year o l d (=75-145 mm CW) male and female C. magi s t e r i n Lemmens Inlet. The c a p i t a l l e t t e r s i n parentheses i d e n t i f y these areas i n F i g . 2.1  (page 9 ) .  F i g u r e 4.11.2  Page 9 2  1985  1986 DATE  Figure 4.11.3. Time s e r i e s c o m p a r i s o n of two indices of abundance f o r f e m a l e C . magi s t e r (>145 mm CW) i n t h e s t u d y a r e a , b u t e x c l u d i n g Lemmens I n l e t , Browning Passage, and n e a r I n d i a n I s l a n d , where f e m a l e d e n s i t i e s were g e n e r a l l y low ( T a b l e 4 . 1 1 . 1 ) . ' V i r t u a l e n t r y r a t e s ' were e s t i m a t e d as i n S e c t i o n 4 . 9 .  Figure  4.11.3  Page  93  40MALE  30-  n = 1245  20-  c o  10-  Don  0 >(J  z  LU Z> O w  rr Li_  50  n r-i r-i  n  FEMALE  40-  n = 130  30H 20 I  O  o  H  on" i " "  i"  25  11  55  'T^^T^  DISTANCE  85  115  MOVED  1  n 1  l  —\—  145  175  ( ^ m - d "  1  205  )  Figure 4.11.4. Frequency distributions of mean movement rates f o r male and f e m a l e C. m a g i s t e r . C r a b s r e c o v e r e d a f t e r a mean o f » 1 5 0 d a y s - a t - l a r g e .  Figure  4.11.4  daily were  Page 94  4.12  TAG RETENTION AND TAG INDUCED MORTALITY  Tag  retention  tagged  was  estimated  sublegal-sized  retention those  was  males  analyzed  The  number  retained  both  retention  of  or  rate  recovered 59  t a g was  of 96.8%.  Tag  moulted,  and  recovered. that  and  4,  d i d not  moult  respectively,  and  for a  respectively. 63 6 3 - 2 = 126 ( 5 9 - 2 ) + 4 = 122 (122+ 126 ) • 1 0 0 = 9 6 . 8  Number o f d o u b l e t a g g e d c r a b s E x p e c t e d number o f t a g s : O b s e r v e d number o f t a g s : Percent retention:  recovered:  The number o f m a l e s r e c o v e r e d through  1986.  spring that  double  The mean a n d m e d i a n t i m e s - a t - l a r g e f o r  m a l e s w e r e 83 a n d 69 d a y s ,  these  in  f o r males  before being  males  one  released  separately  t h a t d i d not moult,  r e c o v e r i e s of 850  from  a m o u l t was 64 a n d 1 ,  that retained both  respectively,  o r one t a g  for a retention  rate  o f 99 . 2%. 65 65-2 = 130 ( 6 4 - 2 ) + l = 129 (129+ 130 ) • 1 0 0 = 9 9 . 2  Number o f d o u b l e t a g g e d c r a b s E x p e c t e d number o f t a g s : O b s e r v e d number o f t a g s : Percent retention:  was  Because  the t a g r e t e n t i o n  assumed  t o be  negligible  recovered:  rate  i s apparently high, t a g loss  i n mortality  estimates  (Section  4.13).  Informal held  observations  i n tanks  months  the P a c i f i c  d i d not i n d i c a t e  h a v i n g been  Section  at  4.12  of  tagged  and  Biological  a higher  mortality  untagged  C. m a g i s t e r  Station  f o r several  rate  due t o a  crab  tagged.  Page 95  4.13 FISHING AND NATURAL MORTALITY OF MALES The  mark - r e c o v e r y p r o g r a m p r o v i d e d e s t i m a t e s  natural of  mortality  female  tagged  natural  and  recoveries size  for  mortality  males  ( 1 4 5 - 1 5 5 mm  four  in  sublegal-sized of  in  four  fishing  (No e s t i m a t e s  an  insufficient  logarithms  of  the  was  number  of  plotted  for  who  their  were  recorded  traps,  fishermen  consecutive  results  was  then  sublegal  one  obtained  all  month  from  the  occurrences  of  released  consistent  made  number  and r e c o v e r e d when  These  and  were  released  myself,  males  all  are  4.13.1.  and  because  The  tagged,  CW)  Fig.  fishermen  effort  C . magi s t e r .  recovered).  of  intervals  male  of  them.  over  The  the  study  of  these  per i o d . The males  annual  is  Institute (=3.48, from  the  negative  Inc.  1985)  95%  the  C.I.  study  mortality  combination  of  mortality)  and  size.  slope  The  quadratic suggests as  the  Section  of  that  the  disappearance linear  (Table  (Gulland  365  1983).  Since  movement  to  small  (the  annual  instantaneous  of  Fig. these  a p p l i e d to rate  of  rate  4.13.1 males the  can remain  data  of be in  and  mainly  of  induced the  measures  the  of  moulting considered this  these  days  to  rate  in F i g . 4.13.1  disappearance  tag  contributors  this  instantaneous  rate  loss  crabs ,  the  (SAS  times  tag  be  relationship  4.13.1)  4.11),  seem  t i m e w i t h i n an i n s t a r  4.13  of  tagged M  the  of  (Section  4.12)  M while  curve  slope  2.90-4.06)  area  of  rate  in F i g . 4.13.1  is  (Section  disappearance  estimate  instantaneous  same  into a  legal  maximum  instar.  (Table males  natural  A  4.13.2) increases  increases.  Page  96  Table 4 . 1 3 . 1 . S t a t i s t i c s of the l i n e a r r e l a t i o n s h i p i n F i g . 4 . 1 3 . 1 from w h i c h the a n n u a l i n s t a n t a n e o u s r a t e of d i s a p p e a r a n c e of s u b l e g a l - s i z e d ( 145-155 mm CW) male C . mag i s t e r was e s t i m a t e d . The r e l a t i o n s h i p has the form Y = a + b - X ; where Y i s t h e l o g a r i t h m of the number of recoveries within consecutive one month i n t e r v a l s , and X i s the t i m e - a t - l a r g e i n d a y s .  Parameter  E s t imate  a b  5.99 -9.54E-3  Standard error 0.25 0.81E-3  Table 4 . 1 3 . 2 . Statistics of the q u a d r a t i c r e l a t i o n s h i p i n F i g . 4 . 1 3 . 1 w h i c h s u g g e s t s t h e m o r t a l i t y r a t e may i n c r e a s e as t h e t i m e - a t - l a r g e f o r s u b l e g a l - s i z e d ( 1 4 5 - 1 5 5 mm CW) male C . magi s t e r increases. The r e l a t i o n s h i p has t h e form Y = a + b - X + c - X ; where Y i s t h e l o g a r i t h m o f the number o f r e c o v e r i e s w i t h i n consecutive one month i n t e r v a l s , and X i s t h e t i m e - a t - l a r g e i n d a y s . 2  Parameter  E s t imate  a b c a  Not  when  4.13.2  tagged  intervals,  and  for  total  annual  males  (Z)  Fig.  4.92 3 .65E-5 -1.67E-5  significantly  Figure  4.13.2  7.23-11.23)  from  plots  recovery  the  released  a total  the  Sect i o n  4.13  of  the  of  (n=341),  rate  times p.  110,  annual  182  for  53.4%  of  slope  4.13.3)  ( G u l l a n d 1983,  estimate  b=0.0.  r e c o v e r y of  negative  (Table  minimum  0.40 316 . 0 E - 5 .. 0.54E-5  a  different  instantaneous  is  Standard error  males,  consecutive  from a l l  disappearance  of 365  the  legal  linear  days  15  day  fishermen.  The  of  instantaneous  legal-sized  relationship  (=9.23,  Eqn. 4.33).  size  95%  C.I.  in is  A p r o v i s i o n a l and rate  of  fishing  Page  97  mortality  (F)  instantaneous for  all  is rate  other of  tagged  tag  or  tag  recovered  of  or  4.29  accounts  Again,  crabs  from  the  of  (1)  I d i d not  Therefore,  for  since  the  natural  these  tags  is  area  an  of  and  from t h e  significant  this  were  annual  recoveries  no  over  tags  mortality,  o b t a i n the  lack  there  study  induced m o r t a l i t y ,  because  missed by,  (=9.23-0.534).  reasons.  movement loss  4.95  time,  probably (2)  they  or not  were  fishermen.  Table 4 . 1 3 . 3 . S t a t i s t i c s of the l i n e a r r e l a t i o n s h i p i n F i g . 4 . 1 3 . 2 from w h i c h t h e a n n u a l i n s t a n t a n e o u s r a t e o f d i s a p p e a r a n c e (Z) of legal-sized male C . magi s t e r was estimated. The r e l a t i o n s h i p has the form Y = a + b - X ; where Y i s t h e l o g a r i t h m of t h e number o f r e c o v e r i e s w i t h i n c o n s e c u t i v e 15 d a y i n t e r v a l s , and X i s the t i m e - a t - l a r g e i n d a y s .  Parameter  E s t imate  a b  4.23 -2.53E-2  From legal  size  legal  size  of  when was  of  obtained  a  legal-sized  time  legal  of size.  Figure decreases  Section  the is  Moulting  4.13.3  with  4.13  moulting  size,  shows with  to  37-50  From t h e  Since  this,  it  occurs a l l  moulting  into  revised  year,  Fig.  males  percent  of  estimate recovery  4.13.3b  covers  resembles 125-155 mm  but mostly  survivorship  smaller  and  closely  sublegal-sized  that  of  tagged,  a 50% e x p e c t a t i o n  days.  than  a  profile  4.13.3).  time  of  0.27 0.28E-2  seasonal  (Fig.  p e r i o d much g r e a t e r  seasonality into  male  a  error  125-155 mm CW when  males,  recovered,  F ( 5 . 1 1 - 6 . 9 0 ) below,  for a  recoveries  Standard  to  the  of  crabs  the CW  i n summer. next  instar  140-155 mm  Page  98  CW a t t a i n i n g to  be  a  crabs.  of  result Most  nearly large  legal  all (Fig.  of  moulting  was  4.13.4,  at  shows  trend  size.  The  after  provides  of  this  moulting  only  monitored  observed  less  since days  relationship were  a minimum e s t i m a t e  because tagged, the  the  larger and  days  instantaneous 3.48  (Fig.  these  it  is  length  of  rate  crabs  were 4.13.4  increasing  be  precisely  not  therefore  at  4.13.1,  Figure  cannot  not  days,  period with  period  of  seems  400  large.  intermoult  intermoult  for  than  <3% of at  This  400-600  The a n n u a l  400  longer  crabs  for  after  this  after  the  time  145-155 mm CW of  suggests  toward a  from  intermoult  were  males  size  length  determined long  for  this  125-140 mm CW.  Table 4 . 1 3 . 4 ) .  also  present  those  insufficient crabs  4.13.1)  a  than  tagged  disappearance  Table  size  known  Fig.  the  how  4.13.4  intermoult  per i o d .  Table 4 . 1 3 . 4 . S t a t i s t i c s of the l i n e a r r e l a t i o n s h i p i n F i g . 4.13.4 estimating the mean t i m e - a t - l a r g e for recovered tagged s u b l e g a l - s i z e d male C . magi s t e r . The r e l a t i o n s h i p has t h e form Y = a + b - X ; where Y i s t h e t i m e t o r e c o v e r y ( i n d a y s ) , and X i s the p r e - m o u l t carapace w i d t h .  The legal  Parameter  E s t imate  a b  -628.4 6.22  percent  size  .is  legal-sized 4.13.5).  Section  of  sublegal-sized  estimated  males  that  C a l c u l a t i o n of  4.13  from were  Standard 113.0 0.81  males  expected  the  number  tagged  when  mortality  error  from  of  to  recovered  sublegal  these  survive  data  size is  to  tagged (Table somewhat  Page  99  hindered  by  an  legal-sized  males  proportion males  uncertain  as  tagged  represents  caught  which 155.0 the  are  composed  mm i n s t a r , negative  of  proportion  0.534  I will  of  the  recovered  of  refer  341  (Fig.  compliance.  of  tagged to  this  legal-sized  4.13.2),  This  this  estimate  can  below.  145-150 and 150-155 mm CW from T a b l e of  males  M can be  log  the  observed.  were  estimate  explained  From c a t e g o r i e s  I  of  Since  released  minimum  be r e v i s e d as  that  compliance. and  a  estimate  the  close  to  legal  size  p r o v i s i o n a l l y estimated proportion  recovered,  4.13.5,  within  at  4.48  adjusted  the (i.e.  for  the  adjustment  for  document  the  time-at - large).  M = - l n ( 5 3 * 2 2 4 6 )•( 365-305 ) A  revised  compliance  (C),  estimate  of  M,  incorporating  recovery and  Fig. of  i n the  males 155.0  an  is: M = 4.48 + l n ( C )  From  ( 4.13.1 )  4.13.2  and  tagged,  Table  released  (4.13.2)  4.13.3,  which  a n d r e c o v e r e d when  legal  size,  mm i n s t a r : Z F  = 9 .23 + 1 .02 = ( 0 .534*C ) -Z M = Z-F  ( 4 .13 .3 ) (4.13.4) (4.13.5)  there f o r e , M = Z - ( 0 . 5 3 4 - C ) -Z  Section  4.13  (4.13.6)  Page  100  If an  one  assumes t h a t  M and C a r e  of  obtained  estimate  C can  simultaneously confidence estimate  limits  of  range  of  of  M for  range  of  for  M for  of as  Fig.  the  4.13.3,  The  size  estimate  the  applies for  during,  size.  If  assumption  true. may be  Sect ion  fishery,  of  from  this  that  the on the  fishing  of  cannot,  0.869.  lower  As was  The  of  the  compliance  reports  size-dependent  4.33.  4.33 - 4 . 4 8 .  estimates  125-155 mm a s s u m i n g  M=4.33-4.48  only  is  corresponding  consideration  4.13.5  6  95%  and M at  is  the  and  the  obviously  0.869,  accept  Table  compliance  obtained  this  Thus,  I  4.13.2  no  but  0.869-1.00  analyses,  Within  Z<9.59  In  both  Eqns. M.  at  5.11-6.90.  suggest  for  the  more  apparent  mortality,  in  larger  survivorship.  to  from  for of  males  is  a  data  of  (F)  Since  sublegal higher  the  size,  the  moult  then  M should  similar  4.13.3 may  be  and 5 i s  latter best  rate to  for legal  the  not  is the  the  mortality  be  CW  essentially  explanation  in Tables  mortality  for  following,  correct  estimates  145-155 mm  4.13.1.  still  soft-shelled  the  crabs  M=3.48,  Fig.  discrepancy  or w h i l e  a n a l y s e s based  from  maximum e s t i m a t e  range,  explanation males  lower  estimate  than  of  for  estimated  plausible.  results  crabs h a v i n g the  same  is  5 mm CW i n t e r v a l s estimate  of  because C must,  C is  this  conservative  higher  F  same  solving  estimate  C ranging  0.869  by  Z (7.23-11.23),  obtainable  monitoring  estimate  single  For Z=11.23,  equivalent close  a  of  M is  exceed 1.0. The  for  be  the  above for  the  strictly  underestimated  and M  overestimated.  4.13  Page  101  No e x p e r i m e n t s disappearance size  of  were a t t e m p t e d  sublega1 - s i z e d  and d i s a p p e a r a n c e  between  pre-  and  4.13.5,  so  the  further  resolved.  However, sublegal  moulting,  greater  the  frequency  fishery,  including  c o u l d not  detect  mark - r e c o v e r y  an 183.8  results  in  the can  males moult,  Fig.  conclude  trap  that is  this  mm t o  is  legal  and in  (2)  Table  M cannot the  be  more  the to  mortality.  males  for  Inlet  183.8  each  fishery,  consistent  section  the  the  attributable  Holberg  This  in  of  sampled  fished  mm i n s t a r .  4.13.1,  estimates  (1)  to  mortality  or p o s t - m o u l t ,  on  lightly  155.0  in  between  moulting  in F i g . 4.13.1  presented  low s u r v i v o r s h i p from the  to  post-moult  one  analysis the  due  mortality  discrepancies  of  Size  to  distinguish  males  immediately  disappearance the  due  to  which  with  the  indicate  mm i n s t a r .  Table 4 . 1 3 . 5 . Summary o f s u r v i v o r s h i p t o l e g a l s i z e o f male C . magi s t e r w h i c h were t a g g e d when s u b l e g a l s i z e , a n d r e c o v e r e d when l e g a l s i z e , f o r 5 mm i n t e r v a l s from 125-155 mm CW. Pre-moult carapace width Number tagged (mm) 125-130 130-135 135-140 140-145 145-150 150-155 a  b  168 310 366 499 1027 1219  Recover ie s n <* ) 20 50 52 35 28 25  11 .9 16.1 14 .2 7.0 2 .7 2.1  Per c e n t surviving to l e g a l s i ze a  32 .1 24.0 19 . 2 9.5 3 .7 2.8  Mean days I n s t a n t a n e o u s at annual mortality large 1 3  165 196 227 258 289 320  2 .87 2.96 2.91 3 .56 4.37 4.27  C a l c u l a t e d by m u l t i p l y i n g t h e p e r c e n t r e c o v e r e d i n e a c h 5 mm CW i n t e r v a l b y 1.15 t o compensate f o r the more c o n s e r v a t i v e e s t i m a t e o f o n l y 86.9% o f t a g g e d l e g a l - s i z e d c r a b s l a n d e d being observed. The p e r c e n t r e c o v e r e d i n i n t e r v a l s 125-130 a n d 130-135 mm CW was f u r t h e r m u l t i p l i e d by 2 . 0 a n d 1 . 1 , r e s p e c t i v e l y , b e c a u s e o n l y 50% and 90% of c r a b s t h i s s i z e a r e expected to a t t a i n l e g a l s i z e w i t h t h e i r next m o u l t . From r e g r e s s i o n p a r a m e t e r s o f F i g . 4 . 1 3 . 4 (Y = - 628 . 4+ 6 . 22•X ).  Section  4.13  Page  102  Figure 4.13.1. Linear and quadratic regressions of recoveries over time f o r t a g g e d male C . magi s t e r r e l e a s e d and r e c o v e r e d as s u b l e g a l - s i z e d c r a b s 145-155 mm CW. Most tagging was done from M a y - J u l y 1985. The open c i r c l e s were not i n c l u d e d in the regression analyses because fishermen were not well p r e p a r e d f o r the m a r k - r e c o v e r y program at t h i s t i m e .  Figure  4.13.1  Page  103  Figure 4.13.2. L i n e a r r e g r e s s i o n of r e c o v e r i e s over time for 341 tagged male C . magi s t e r released and recovered as l e g a l - s i z e d c r a b s , m o s t l y i n s p r i n g 1986.  Figure  4.13.2  Page  104  50 - i R E L E A S E S  n (125- 140mm) = 8 4 4  40-  a>  CL  (76.5%)  20  IxJ ZD O UJ  cr u_  •  125 - 140 mm  •  140 - 155 mm  10' 0" T T ^ T T I i T i S T i T  o z  MALES  (23.5%)  n (140-155mm) =2745  30c a> o  OF S U B L E G A L - S I Z E D  50-  RECOVERIES  40-  OF L E G A L - S I Z E D  MALES  n ( 1 2 5 - 1 4 0 m m ) = 127  (58.8%)  n (I40-I55mm)  30-  i—i—i—rn—r  = 89  (41.2%)  2010' 0  I  i  I  I  T  AMJJASONDJJ 1985  F M A M J J A S 0 N 1986  DjJ F  1987  DATE  of of as  Figure 4.13.3. (A) Frequency d i s t r i b u t i o n of r e l e a s e dates s u b l e g a l - s i z e d male C . magi s t e r . (B) Frequency d i s t r i b u t i o n r e c o v e r y dates for those crabs r e l e a s e d i n (A) and r e c o v e r e d legal-sized crabs.  Figure  4.13.3  Page  105  _  600  n = 216  -i  CO  •5  p <.000l  500 H  r2 = 2 1 . 4 %  • • •  UJ 4 0 0 (3  or ^ 300-1 < I  200 H  S  100 -I  UJ  0  •  I  • • • • • •  #  •  • ••• •  T 125  T  130  PRE-MOULT  135 135  ~I—  140 140  CARAPACE  •  9  ~1  145  150  WIDTH  155  (mm)  Figure 4.13.4. L i n e a r r e g r e s s i o n o f t i m e - a t - l a r g e f o r male C . magi s t e r . t a g g e d and r e l e a s e d when s u b l e g a l s i z e a n d r e c o v e r e d when l e g a l s i z e , on p r e - m o u l t c a r a p a c e w i d t h .  Figure  4.13.4  Page  106  4.14  FISHING INTENSITY AND FEMALE CATCH CURVES IN SELECTED FISHERIES  Table  4.14.1  fisheries areas  as  do  defined  not  the  and  number of  indicators virtual  fishing  entry rate  impact.  These  Fraser  delta  Inlet  fishery  Tofino  days  sales  were  in  lightly  Dixon  heavily  C.  p o p u l a t i o n near T o f i n o  1975) a  for  lower  females  females  commercial  The  catch  samples  these  fisheries  years  was  the  caught  s u r v i v o r s h i p to  populations.  possibly  not  from  were  being  samples  were  Section  4.9.  Section  4 .14  has  curve ' the  sampled.  age-class.  two  that  the  Prior  to  (Fig.  i n the each  1985  fishing.  (Ricker  4.14.1)  suggest  the  fished  combines  when  from  each  of  consecutive  influence  of  catch  curves  the entry  larger  the  curves  years  plotting  to  near  fishing  fishery  reduce  The  Holberg  more h e a v i l y  obtain virtual  females  the  heavy  catch  consecutive  (1975) to  4.9.  since  experienced  the  fishing  fisheries,  C o m b i n i n g samples  s t a n d a r d i z e d to  S u r v i v o r s h i p of  for  while  and  intermediate  fisheries  instars  relative  of  Section  other  shows  fished,  by t h e s e  s u g g e s t e d by R i c k e r dominant  study  larger  Two  experience  except  Despite  this  in  males  fishing,  are  indicators  as  of  exploitation  exploited,  exploited.  intensity, magi s t e r  are  determined  Entrance  that  males  statistical  vessels  fisheries of  regional  quantity  number of  The d e g r e e  four  These  The  regional  legal-sized  f i s h e r y appears  and  the  these  in  Area.  area.  fished,  in  impacts  is  in  effort.  of  intensity  Statistical  markedly  number of  of  fishing  by  differ  landed, the  compares  rates  instars  as  a  in  in  the  Page  107  heavily  fished  the  lightly  for  the  fished  other  It  is  intensely females  exploited  size.  also  seen  fishery.  in traps  encountered including within  or  the  handling lower.  were  If  fishery  well  this  survivorship  there of  is  suggesting  of  no  females  catch  from  the  for  curves  study.  in  traps  crabs  in  unseen  were  seldom  crabs  were  mortality  occurs  w o u l d be  male-only  an  parts,  then  to  in  body  low,  traps,  from  handling  connected  evidence  intense  results  crabs  is  traps  abundance  When s u c h  by  the  frequency  in  pattern  in  legal-sized  size  decrease  dead  little  direct  in  that  females  results  or  represented  induced m o r t a l i t y outside Thus,  the  large  because  injured  during  density  than  t r a p p i n g and e x c e s s i v e  mortality  high  of  unlikely this  Mortally  carapace,  traps.  artificially  to  lower  while  discontinuous  seems  trawls  they  absence  delta  a  much  intermediate.  the  show  is  fishery,  harvested  i n c r e a s e d m o r t a l i t y due intensive  are  Fraser  not It  Inlet  that  been  do  fishery  Holberg  unlikely  having  legal  delta  two r e g i o n s  distributions at  Fraser  despite  the  trapping  and  expected  suggest  that  fisheries  is  to  be  lower due  to  t r a p p i n g and h a n d l i n g .  Since male,  females  moult  many  of  whom  population,  it  is  instars  in  elaborates for  males on  mate  in  have  been  removed  conceivable  heavily  legal-sized  may  and  this  fished for  that  the  females  populations  mating  partners.  possibility,  and  its  company in  a  may not because The  a  larger  heavily  fished  achieve  larger  of  of  a  following  potential  lack  of  section  consequences  p o p u l a t i o n egg p r o d u c t i o n .  Section  4.14  Page  108  Table 4 . 1 4 . 1 . C o m p a r i s o n s among d i f f e r e n t measures o f f i s h i n g e f f o r t , and f i s h i n g i m p a c t , on male C . magi s t e r p o p u l a t i o n s i n f o u r r e g i o n a l f i s h e r i e s d e f i n e d b y S t a t i s t i c a l A r e a ( S A ) . The s t a t i s t i c a l a r e a s do not d i f f e r m a r k e d l y i n a r e a . Annual f i s h i n g s t a t i s t i c s i n c l u d e the m e t r i c t o n n e s l a n d e d ( t ) and t h e number of days f i s h i n g ( D F ) . Annual  Region  Degree of exploitation  d H o l b e r g I n l e t (SA 27 ) 45 D i x o n E n t r a n c e (SA 1 ) *75 Near T o f i n o (SA 24 ) 869 F r a s e r d e l t a (SA 29) B r i t i s h Columbia Total 1  7  e  f  3  Virtual entry rate"  Number of vessels  0  Number of sales c  641 84 103 49  10 25 27 119  37 135 434 1307  -  -  -  fishinq 1984  1983 t  statistics  DF  t  1985 DF  t.  DJL  5 116 5 185 3 73 146 457 160 474 136 394 1869 110 1228 152 1391 136 3662 274 2341 341 3636 353 959 12987 1155 15731 1165 16851  a  The p e r c e n t o f the l e g a l - s i z e d males i n the 1 5 5 . 0 mm i n s t a r t a k e n by t h e f i s h e r y near end o f t h e s e a s o n . See S e c t i o n 4.9 f o r an e x p l a n a t i o n o f t h i s e s t i m a t e . The number o f l e g a l - s i z e d male c r a b s t h a t w o u l d e n t e r 100 t r a p s i f t h e e n t r y r a t e was r e d u c e d ( 1 ) by c r a b s w i t h i n t r a p s i n h i b i t i n g the e n t r y of more c r a b s , and ( 2 ) changes bait effectiveness. See S e c t i o n 4.7 f o r a more c o m p l e t e e x p l a n a t i o n . In 1984. In December 1984. Mean of O c t o b e r 1983 and 1984. From F i g u r e 4 . 9 . 2 . <? Mean o f O c t o b e r 1984 and 1985.  the  b  not in  c  d  e  f  Section  4.14  Page  109  TLX  1  • AREA 27  2  142.5  152.5  162.5  CARAPACE  172.5  WIDTH  ( H o l b e r g Inlet)  182.5 192.5  (-2.5mm)  Figure 4.14.1. C o m p a r i s o n o f c a t c h c u r v e s ( R i c k e r 1975) females from four regional C . magi s t e r fisheries defined S t a t i s t i c a l Area in B r i t i s h Columbia.  for by-  Page  110  Figure  4.14.1  5 YIELD5.1  AND EGGS-PER-RECRUIT  DEVELOPMENT  This  section  evaluates  eggs-per-recruit limit  for  information female  obtained  in t h i s  study  catch  of  males,  (page  yield-per-recruit  and  growth.  model  for  distinguished  increments-at-size  this  would and  not  have  on  workers  for been  eggs-per-recruit  et  by  have  when  the  sizes  is  width  using  (1986),  von  the  Bertalanffy  were  not  easily  seemed an a p p r o p r i a t e few  moults  relevant  appropriate.  legal  acknowledging  a  instars  having  the  increments-at-size,  used  g r o w t h model  on  (1985).  minimum  Caddy  moult  based  al.  carapace  by  critical  accounting  different  from  size  i n f o r m a t i o n on  probabilities,  C . magi s t e r  moult  yield-  moult  crustaceans  With  for  based  and a c o n t i n u o u s  simplification.  are  recommended  is  Some  mortality)  from H a n k i n  determined  As  analysis  frequency  discontinuous  55).  for  by  and  legal  estimates  determined  by w e i g h t ,  yield-  minimum  supplemented  and f e c u n d i t y  D r y w e i g h t was  4.7.3.4  growth  and  C . magi s t e r the  and  y i e l d - p e r - r e c r u i t was  limits.  moult  structure growth  mortality  in  altering  (e.g.  Relative  Eqn.  Model  from  variables  growth,  predicted  trade-offs  resulting  males.  population  size  MODEL  to  The  explained  and  this  large  analysis,  determination in  the  of  following  paragraphs.  The male,  model  and  the  instars  defined  Section  5  includes 100.7, by  the  the  102.9,  128.0,  119.4,  135.5,  149.4  size  frequency  155.0 and  analyses  and  161.4 in  mm  183.8 mm female,  Section  Page  4.6.  111  The  smallest  years  after  particular Tables All  male  instars  4.6.3  accounted.  in  years.  and  Male  Eqns.  5.1.1,  4.5.1  and  and f e m a l e s ,  Table  41  each  of  the  are  which  for  modeled  1 mm CW i n t e r v a l s this  Age  Age  Age  3  4  5  S e c t i on  5.1.1.  Winter Spr i n g Summer Autumn Winter Spr i n g Summer Autumn Winter Spr i n g Summer Autumn Winter Spr i n g Summer Autumn  5.1  from 105).  to  account  moult  for  creating  the  a  smallest  d i s t r i b u t i o n by  i n c r ement s - a t - s i ze , page  33)  are  1-4  normal instars  applying for  males  respectively.  Date  2  when  (page  vectors  by  for  time  two  each a g e - c l a s s  four  failed  summer  estimated  The  mean  and  standard  deviation  age and time of y e a r when t h e y a r e n e a r l y f u l l y become s e x u a l l y a c t i ve i n t h e 155 .0 mm i n s t a r •  Age  in  and F i g . 4 . 1 3 . 3  additional  incrementing  and  instars  g r o w t h was  (moult  dominant  5.1.1),  and 4 2 ) ,  age-class  then 2  (Table  an  female  are  timing,  and f e m a l e  females  distribution  Table  dominate  i n male  For  instars  Moult  and 4 ( p a g e s  individuals  in  female  settlement.  individuals  size  and  Male  instars  102 .9+  9.8  Female  183 . 8 ± 1 2 .0  100 .7 + 12 .8 119 .4 + 11 .0  Males  egg p r o d u c i n g females from thi s instar on  135.5+  9.5  149 .4+  assumes f e m a l e s i n 135 . 5 t o 161 .4 mm instars normally moult a n n u a l l y 8.2  H n II  n  formed.  of  instars  128 .0+10.5 155 .0 + 11 .2  (mm)  161 .4+  7.1  assumes males this size do n o t moult a n n u a l l y  Page  112  Annual 5.1.1  to  Annual were  mortality  determine  Hankin  increasing  et  with  an  sizes  small  their  annual  I  mortality  assumed  high  in  mortality  and  mortality M  traps  yield-  estimates for  of  estimates,  in  2.5  and 4 . 0 .  cohorts  are  >125 mm. M=0.7  effectively to  the  1.0,  and  M  larger  misrepresenting  eggs-per-recruit  sizes  are  0.7-2.5,  moult  thus  variability  males  suggests  and  all  for  not  crabs  increases,  of  females.  females  do  Table  estimates at  for  traps  tagged  in  estimates  widths  smaller  Because  constant  (M)  commercial  As t h e  report  instars  males  estimated  carapace  because  abundance.  for  Female  who  the  m a r k - r e c o v e r y methodology  occurrence  estimates,  study.  increasing of  to  mortality  (1985 ),  crabs.  their  relative  are  al .  applied  numbers-at-age  this  underestimate  retain  are  natural  in  A consideration is  the  instantaneous  determined  from  rates  mortality  results  for  Mortality  ages.  rates  Considering  followed  to  the  virtual  extinction.  As  suggested  occurrence  of  considered  sexually  Butler  (1960)  by  m a t i n g marks mature  suggests  m a t i n g marks on males have  difficultly  embrace a  female  Sect i o n  since  size  until  males  this  Fig.  4.4.1  frequency  (Fig.  size  (page  smaller  4.10.1, they  are  f i n d i n g mature  considerable  5.1  the  page  attain  mature  were r a r e . females 31)  distribution  of  81),  the  at  males  155.0  the  are  not  mm i n s t a r .  100-110 mm CW,  Males t h i s a size  s u g g e s t s males  than themselves.  of  that must  but  size  would  they  could  mate  Most males  with  become  Page  113  functionally consistent the  mature  with  their  attaining  becoming  13C mm  functionally  mature  CW.  This  is  upon  attaining  1 5 5 . 0 mm i n s t a r . Since  one  one  summer  number  of  ratio).  males week  male  season  can  mated  Such e s t i m a t e s  in  in  the  a laboratory tank.  required s e a s o n the  In report  days  10  for  eggs-per.-r e c r u i t Since  response  relationship  density,  I  assume  mated by a male  reasonable  to  attempt  maximize  to  number of For sexually  since  expect  the  pair  of  is  the  mature  a male p a r t n e r .  S e c t i o n 5.1  are  is that  their  the  the instar.  1 0 0 . 7 mm Further  two  Over  such  any  female  of  female  a  mating  a  ratios  and  of  female  density.  by  I  functional  females  density  fitness  mating  estimates,  develop  maximum nueber  one  females  that  F:M mating, r a t i o  evolutionary  As r e p o r t e d  to  m o d i f i e d by  at  In a  maximum F : M m a t i n g  no d a t a  the  not  observed.  be  individual  (1966) report  in  between  cannot  of  with  uncertainty for  maximum  possible.  successfully  in  (F:M mating  behavior  large.  are  that  not  females the  required  potentially  results there  of  observations  they  females w i t h which they females  is  natural  and  mate  several  estimate  male  season  a male  with  an  Snow and N e i l s e n  consideration  must  each  elusive  F:M mating r a t i o  5, 10 and 2 0 : 1 .  can be  by  a mating  I observed  mate  1960),  laboratory,  nature, for  period  apparently  (Butler  females  replicated  in  after  that It  males  is  would  maximizing  the  mate. instar moults  is  considered  require  i n F i g . 4.3.1 (page  a  the  female  29),  no  first to  have  sexually  Page 114  mature  females  females P.W.  do  Wild  comm.)  of  Hankin  in  both  this et  is  not  et  probabilities  not  al. for  for  145  least  mm CW.  male  at  31),  so a p o s s i b l e  instars remove  is  instars  a  Columbia  high  for  to  typical  for  in for  a  a  140  for  >145  partner not  males.  reduce  (Fig.  decline near  of  0.0,  require  4.4.1,  moulting to  each y e a r  a  page larger  fisheries (Methot  and  females  to  larger  populations  in  British  a  lack  of  mating  mating  this  legal-sized  their  moulting  larger  Substantiating of  mm CW.  California  males  of  Section  California  females  rates  in  annual  mm CW and  suggests  (pers.  The d a t a  130 mm CW, t o  C . magi s t e r  exploitation  mated.  absence  curves  that  survivorship  females.  the  females.  catch  female  legal-sized  markedly  for  females  mating  also  in  central  legal-sized  4.14)  having  that  and  is  males  the  can  potential  be  (Fig.  page 83 ).  e a c h y e a r was interval  distributed  Section  moulting  report  exploited  The p r o p o r t i o n of  CW  case  lower  larger  that  enough  4.10.3,  The  heavily  conclusion  of  without  female  Females  p o r t i o n of  (Section  moulting  the  explanation  lack  1982). in  the  155 mm CW f o r  a large  Botsford  and  1.0,  indicating  1985 ) and G . S . J a m i e s o n  females  females  from near  female  al .  (1985)  precipitously a  et  packs  sizes  necessarily  ( 1985 ) , is  sperm  larger  Hankin  this  Hankin  without  observed  al .  suggest  found  attain  (cited  but  4.14,  not  have  males,  were  5.1  females  d e t e r m i n e d as within  either  proportionately  in  each  follows. the  A l l males  155.0  among  1 mm CW i n t e r v a l  or  females  183.8  i n the mm  available  moulting  120-121 mm  instars for  were mating  Page  115  within This  the  was  carapace width repeated  results  for  each  mating  ratio  to  each  interval.  interval total  is  number o f  females lower  et  qualitative, production moulted.  and  estimates  for  Female  et  not  was  and  moult  of  this the  females which  the  previous  fecundity  estimated  fail  (i.e.  (E)  using  the  since  to  rate  1 mm CW  a  undergo  season  Their  data  by is are  between  female  egg  the  production  current  of  no d e c r e a s e )  for  1.0.  egg  evaluates  annual  mated  each  relationship  years  model  in  and m o u l t .  a  The  mated d i v i d e d by  winter  d i d mate  define  mated  in  mm CW.  females  a maximum of  that  number  of  to  31).  m u l t i p l i e d by the F : M  females  show  mate  e v a l u a t e d were 1.0  production  of  (page  >121  number of  females  available,  not  the  of  number  (1985 )  do  were t h e n  potential  females which and  p r o d u c t i o n by  mm)  females  in F i g . 4.4.1  1 mm CW i n t e r v a l s  the  potential  Therefore,  extreme  rates  define  did  for  defined  1 mm CW i n t e r v a l  al .  which  than  all  The p r o p o r t i o n  the  Hankin  for  limits  egg  mated  and  production  for  decrease  an a n n u a l and 0.0  in  egg  moult.  The  times  the  egg  year.  as the  a  function  following  of  carapace  relationship  width from  (CW,  Hankin  a l . (1985 ) .  E To with  be  eggs  consistent in  this  larger  than  the  Sect ion  5.1  = -593000+9670•CW with  study 100.7  the  only mm  (5.1.1)  minimum s i z e  of  females  >100  instar  produced  females  mm CW w i t h i n eggs.  observed instars This  Page  is  116  equivalent 4.5.2,  to  page  a mating  a  pre-moult  33),  close  to  carapace  the  width  of  size  of  smallest  78 ram ( f r o m female  Eqn.  observed  in  embrace.  5.2 RESULTS Figure  5.2.1  indicates  that  assures  near  maximum p o p u l a t i o n  results  also  provide  For  example,  for  ( = 6 0 : 1 ) w o u l d be a  high  could  mean  not  would C.  a  be  seem  not  been  low  as  achieved  since  mated.  3:1  is  chelipeds Butler's  F:M  estimates  If is  an  lower  Section  males  (1960)  mating  marks)  of  these  accurate  5.1  mate  for  is  all  one  =10-15:1  with  time  the  At such  involved  male  population  for  observed  mature that  F:M mating are  This  had  ratio  mated.  deep  scars  on  in  this  study  and  that  many  more  Consequently,  M=2.5  seem  the  more  as  Since  and  males.  in  expectancies.  a  surmise  the in than  a maximum plausible  processes.  (as  estimated  in  annual  estimate,  then  the  females.  females  common  would  ratio  ever  M=1.0,  These  F:M mating  unlikely  were  extensive were  =10-15:1  of M.  the  life  M=4.0  ensure  of  estimates  all  for  short  were mated by t h e s e  M=2.87-4.48  during  to  high  60:1  females  with  study,  ratio for  that  sufficient  to  of  of  Alternatively,  (mating  females  because  no mature  evaluating  considering  ratio  indicate  for  males  then  F:M mating  sublegal-sized  three  rate,  ratio  p r o d u c t i o n when M = 2 . 5 .  extremely  r e q u i r e d for  to  magi s t e r ,  an  F:M mating  egg  insight  M=4.0,  mortality  mating,  some  a  time  of  year  Section  when  4.13  mortality males  are  of  this  rates  study) must  be  reproduct i vely  Page 117  Figure 5.2.1. Relative egg production by C. m a g i s t e r p o p u l a t i o n s as a f u n c t i o n of t h e F : M m a t i n g r a t i o , a n d f o r t h r e e e s t i m a t e s of M . T h e s e r e s u l t s a r e not n o t i c e a b l y s e n s i t i v e to t h e a n n u a l r a t e of d e c r e a s e i n egg p r o d u c t i o n b y f e m a l e s who f a i l t o mate and m o u l t i n p r e v i o u s y e a r s .  Figure  5.2.1  Page  120  FISHING  MORTALITY  (F)  Figure 5.2.2. Yield-per-recruit (YPR) for increasing fishing mortality (F). The r e s u l t s are r e p o r t e d r e l a t i v e to F=<».  Figure  5.2.2  Page 121  LEGAL CARAPACE WIDTH (mm)  Figure 5.2.3. Y i e l d - p e r - r e c r u i t i s r e p o r t e d r e l a t i v e t o 1.0 a t 165 ram CW ( S - S ) . E g g s - p e r - r e c r u i t a r e r e p o r t e d r e l a t i v e t o an unfished population. The b r e a d t h o f t h e r e l a t i o n s h i p s indicate t h e r a n g e when t h e a n n u a l d e c r e a s e i n egg p r o d u c t i o n by females t h a t d i d not mate and m o u l t i n p r e v i o u s y e a r s i s v a r i e d from 0 . 0 - 1 . 0 times the egg p r o d u c t i o n o f the previous year. Both notch-to-notch ( N - N ) and s p i n e - t o - s p i n e (S-S) carapace widths, and t h e c u r r e n t C a n a d i a n ( C ) a n d A m e r i c a n ( A ) l e g a l s i z e s , a r e noted.  Figure  5.2.3  Page  122  6 DISCUSSION 6.1  TRAP PERFORMANCE EXPERIMENTS  Caddy  (1979)  using  trap  These  include  trap  to  outlines  sampling  data  changes  the  many as  an  in bait  target  factors index  environmental  species.  In  this  frequency  d i s t r i b u t i o n and r e l a t i v e  magister  impacts  in  on the  Figure abundance  traps  within  to  (page  traps  Thus,  population  abundance  are  common  demonstrates increasing trap and  per  a  is  Even  distributions, trap  sampling  individuals  Section  6  also  equal  times,  among  results and  (1986)  may  if  the be  attempting  for  corresponding density.  rapidly  and  eventually  catch rate  as  soak  per  L.  an  are  trap  per  (1983)  of not  sampling  Bennett trap  Miller  index  times  Decreasing  (1974) day  with  catch for  per  crabs  prawns.  population populations biased. to  female  increases,  catch  by  and  size  time  fisheries.  reported  target  soak  if  pagurus  the  the  male  Such p r o b l e m s w i t h  Cancer  been  as  less  in  the  in  with  of  retention  of  population  that  mean d a i l y  decrease  soak  differ  within,  relative  shows  of  time,  invertebrate  for  behavior  abundance  over  and  resulted  inappropriate  and B o u t i l l i e r  for  of  samples.  for  times  has  lobsters,  the  dramatic  soak  day  vary  65)  and  when  abundance.  accessibility  design  factors  increases  using  s t a n d a r d i z e d among t h e data  such  interpretation  4.7.3.5  stabilizes.  factors,  considered  population  trap  capabilities,  C.  of  be  effectiveness,  species,  study  to  densities, sampled,  Interactions  enter,  traps  can  or then  size the  between strongly  Page  123  influence  the  balanced.  For crabs  agonistic. of  densities  Miller  C . pr oductus  it  an  demonstrated  that  the  (1982)  a  reduced  the  crab S c y l l a  Munro from  ( 1974 )  trap  was  samples.  In  e n t r y and e x i t  Munro's  into  traps  a  of  model  was  trap,  6.1  the  interactions  are  the  that  catch  rate  between  trap.  Miller  t r a p p i n g C . magi s t e r one  set  of  changing often the  traps  the  caught  presence  further  on  and r e e f a  trap  trap this  and  more  bait,  more of  he  crabs.  a crab  captures  fishes  he  of  in the  (2)  from  and  measured the  entry  (1)  and  exit  were  of  rates  information  in  in  traps  from  bait  agonistic  reducing to  these  into  the  behavior.  of  of  the  modified  changes  in  Incorporation  improving soak  a balance  effects  ability  interactions  species  individuals the  information  r e p o r t e d that  These p r o c e s s e s  sizes.  different  improve dynamic  results  study  (3)  to  the  design  C. magister  in  first  paper  time,  simulating  successful  of  processes.  different  which experienced  S e c t i on  in  theme,  among a  magi s t e r  into  fish  over  interactions  C.  his  effectiveness,  effectiveness  rates  of  traps  rates  Following  emptying  concluded that  are  interactions  when  without  traps  that  enter  h a u l e d more  one  number o f  bait  from  serrata Forskal .  eventual  by  t r y i n g to  probability  between A n t i l l e a n f i s h  of  exit  agonistic  set,  traps  and H i l l  portunid  by  interactions  equivalent  and  intraspecific  By h a u l i n g a n d  Williams trap  entry  demonstrated  and t h o s e  agonistic  and C . p r o d u c t u s . than  1979)  limited  crabs w i t h i n a t r a p ,  often  which  seems t h a t  (1978,  was  (1980 ) o b s e r v e d  at  and trap  entry retain factors out  of  samples  times.  Page  124  Although sampling  the  data,  standardization  it  did  interactions  between  the  formulation  correct  interactions Also,  temperature,  traps  for  (Eqn. 4 . 7 . 3 . 3 ,  and  and  the  page  among b a i t s  55)  were  sampled  exclusively.  Females  changes  were used  traps.  is  not  in  an  assumed  important as  but  clam to  the  dynamic  uncertainty.  were the  about  agonistic  tides,  (P.  have  trap  Uncertainty  dynamics  studied,  the  simulating  such  geoduck  were  explain  equation  considerations  seasonal  improved  completely  C . magi s t e r  environmental  Differences  not  model  currents,  not  studied.  fishermen  whose  abrupta)  the  same  almost  dynamics  as  ma1e s .  By also  accepting  assumes  crabs  of  that  If  some  will  be  thus  may  that  immature  aggregated,  different  distributed.  agonistic  smaller  crabs  larger  crabs.  Miller  between i n d i v i d u a l s  Section  6.1  of  entry  crabs  move  to  of  encounter For  the  males  at  trap  opi1io  were  be  observed  C. productus  one  rates  for  0.  rates, and  observed  Fabricus  model  does  competitors  outside  were  randomly  a trap,  agonistic  around the  the  others,  (1975)  outside  weak  in  different  apparently  among c r a b s to  model  density  than  Miller  standardization  expected (1978)  a  example,  Chionoecetes  mature  be  virtual  sizes  interactions  would  of  relative  female  Further,  standardization  their  undersampled.  whereas  the  reflects  likely  and  of  distribution  sizes  less  be  results  the  different  population.  consider  the  not where  against  interactions of  a  trap.  Page  125  Another  consideration  information  on  Thus,  the  when  smaller  is  that  crabs  densities  is  and  lost  with  long  soak  smaller  crabs  will  remain b i a s e d .  the  traps  variable lack  for  in  of  the  are  also  are  not  model,  (see  less  above  estimating  rate  of  63).  Also,  precisely  much  less  traps,  the  and  larger  crabs.  this  study  above  should  inferences  about  times.  this  Section  In  6.1  rates  crabs of  the  the  be  used  smaller study,  no  not  as  this  retention  associated  text)  because  serious  traps  crabs.  a trap  must  e x c e e d the  5 times b e f o r e  for  larger  spend  smaller  (Fig. crabs  much  crabs  samples  were  an  between  samples considered  page  higher  time  and weigh  in  traps  used  when  with when  the  important  model  particularly  from  relative  crabs  not  standardization  cautiously,  are  is  weight  4.7.3.3,  less is  for  This  the  Smaller  interactions  or  concern  larger  modified  the  a  for  is  and  crabs,  crabs  of  crab  mainly  estimated.  dynamic  reasons,  and  an  for  crabs.  least  trap  47  results  because  the  crabs,  within  a  which  of  on page  confidently  dynamics  influencing  the  into  larger  factor  For  crabs  retention  than  so  important  smaller  a t r a p by a t  crabs  the  more  is  times,  rates  of  of  of  virtual  weight  distributions  weight  smaller  entry  62).  The e s t i m a t e d  are  a crab e n t e r i n g  entry  retain  page  the  estimates  for  4.7.3.2,  underestimated  4.7.2.2  increases,  standardized,  considerations  the  the  The  Table  to  be  time  frequency  soak  will  reliable  designed  The  of  shorter  information.  probabilities  because  the  are  soak  (Fig.  size  samples  in  times  as  and  in  making  long  soak  the  soak  Page  126  times  were  longer  to  which a s i z e  of  the  is  4.7.3.5  that  constant  of  the for  to  measure  entry  two  should  C . magi s t e r ports.  relative  selectivities  could  their  They  not  interacting  in b a i t  effectiveness,  For in  this  particular,  Section  6.1  study I  analysis.  that  of  and a g o n i s t i c  considered  define  the  density  the  it  be  nearly  and  times  1986  may  be  of  the  development weeks  size  can  are  1985  if From  and  time,  of  field  selectivities a n d one  the  as  of  i n soak  the  and e x i t  two  without  comparing  difficulty  entry  their  times  which  results  from  combination rates,  of  changes  interactions.  these  selectivity  densities.  escape p o r t s ,  selectivity e.g.  possible  justifiable.  differences  Part  an  In some c i r c u m s t a n c e s  because  of  portion  analysis.  when  soak  difficulties  processes,  I  both  compared the  one w i t h  defining  several  in  several  be  that  5 mm CW i n t e r v a l  reported  control.  functionally  the  samples  considered  changes over  consider  (1985b)  times  how  short  may n o t  traps,  escape  they  also  and computer  s u c h an a n a l y s i s  of  soaks  required  Diamond and H a n k i n sets  day from  model  experimentation  each  be  population  shows  for  only  i n the  not  soak  relative  data  One  standardization  of  and  included  short  in traps  standardized  applied,  should  which  rates  Thus  satisfactory.  cost  65),  and  C . magi s t e r  one  experiments.  model  equal  for  was  s a m p l e d was  using  (page  distribution  Also,  frequency a n a l y s i s  to  purpose  seen  days.  standardization  alternative  Fig.  10  d i s t r i b u t i o n well  This  the  than  as  processes the  separately,  ability  of  and  traps  to  Page  127  retain This  crabs  of  different  definition  other  types  1975),  is  of  more  is  e.g.  that  time,  subsequently  less  in  significantly  influenced  only  nets,  more to  trawls  factors  the  behavior  used  vary  The  of  et  in al .  measurement that  4.7.2.2  time.  (Pope  contents.  Table  of  definition  consistent  trap  by  the  length  of with  retention  (page  47)  are  the  species  and  design.  Others  have  magi s t e r ,  but  measured have  c o m p a r i s o n w i t h the et  a  alter  presented  specified  with  sensitive  probabilities  C.  a  gill  provides  selectivity  trap  for  consistent  fisheries,  and p r e s u m a b l y  and  sizes  al .  ( 1984 )  escapement males. but  Such is  u n d e r s t a n d i n g of  ability  presented of  this  their  useful  for  in  High  the  interactions  retain  to  permit  ( 1 9 7 6 a ) and Muir over  time,  and  evaluating  models  to  results  sublegal-  applicable dynamic  traps  escapement  distinguish  is  of  study.  cumulative  and o n l y  information  less  not  results  present  rates,  the  legal-sized  trap  designed  not  designs,  to  improve  between C . magi s t e r  and  traps .  6.2  SPATIAL AND TEMPORAL DISTRIBUTIONS  Small to  more  male  sheltered  particularly of  small  Inlet.  evident  males This  decreased  Section  C . magi s t e r  6.1  habitat in  gathered  Fig. i n the  concentration  abundance  appeared  is  in  autumn  retreat and  4 . 1 1 . 2 b where protected  dispersed  also  to  due  to  a  winter. large  waters  during  short  of  to  This  was  concentration middle  summer,  moulting  distances  Lemmens  although  legal  size  Page  the and  128  subsequent similar  capture  behavior  reported  that  by  for  the  following  sublegalto  spring. to  winter  spring.  water It  avoid  warmer  the  is  in  to  during  4.11.4,  page  and  94),  suggest  (Butler  1957,  changes  in habitat,  no  studies  C.  magi s t e r . in  (1983) where  the  suggest  Harbor,  to  then  reappeared  movement  of  California  shallower  this  ( 1984 )  Washington,  in northern  water., i n  autumn movement  Returning  to  summer w o u l d  C . magi s t e r  1978b).  which  Except  involve  that  most  released  observed to  channel  mainly  sand  or  a  females  must  be  at  is  shallow,  conceivably  S e c t i on  6.2  into  <30  the  male  English  from  partially  remain  local  movements  seasonal  distances, for  males  Bennett  male  seem  to  and Brown  remained  near  Channel.  coastal  inlets,  to  the  s t u d y a r e a where mix.  other  short  C . pagurus  day  of  apparent  over  a mud/sand mix, the  m per  results  ( 1978b) n o t e d t h a t  move  sand/gravel least  for  migratory  tagged in the  of  populations  prevailing currents.  r a n g e d from mud t o main  w i t h the  movement  directional  d i r e c t i o n of  t h e y were  i n the  male C . magi s t e r  However, G o t s h a l l  report  substrate  for  seem c o n s i s t e n t that  Gotshall  F e m a l e s were  area  Armstrong  year,  winter. during  inferred,  food a v a i l a b i l i t y .  studies,  move  the  or  observed  return  surmise that  A v e r a g e movement r a t e s (Fig.  a  and more p r o d u c t i v e w a t e r  increase  first  (1978b)  and  and  Grays  male C . magi s t e r  winter,  water  in  its  Gotshall  reasonable  rough  of  observed,  Stevens  year-class  and l e g a l - s i z e d  deeper  Others  C . magi s t e r .  1980  disappeared during the  fishermen.  Wild  buried  in  more  the  (1980) sandy  where  the  exposed  b o t t o m was  states substrate  Page  that to  129  extrude that  and  incubate  egg-bearing  eggs.  females  speculated  that  their  in a preferred  eggs  Diamond C.  suggest study less  the  appears that to  locate  suspect  opportunities  Similar  crabs,  S.  serrata,  eggs.  C.  juveniles,  Bennett  paqurus  more  deep  to  (24  S e c t i on  and  short  for  m),  calm  an  release  mature  female  waters  populations. (<20  m per  page  incubating  distances  the  this  day)  were  Thus,  (1983)  water.  where  movements,  Since  may  They  also  of  other  female  in  they  congregated were  rare  portunid they  released  their  after  SCUBA,  crabs.  where  the  hatching  that  female  to  habitat  apparently  Using  they  order  improve mating  demonstrated  C . pagurus  in  s h a l l o w e r water  environment,  inshore waters  incubation.  female  eggs.  it  water.  movement  ocean  and  In  94).  been r e p o r t e d f o r  the  open  to  females  estuarine  Brown  egg  and  to  offshore  4.11.4,  M a l e s and  extensive  egg-bearing  6.2  for  r e t u r n e d to  undergo  suitable  observed  in  females  (Fig.  observed  from  Some f e m a l e s  season.  for  males  return  ( 1984 )  noted  Harbor,  harbour  that  localized  movement b e h a v i o r has  al .  as  argue  by c o n c e n t r a t i n g i n s h a l l o w  et  lived  rates  and m o u l t .  Hyland  Grays  the  movements  suitable  females  mate  in  (1984)  may u n d e r g o some m i g r a t o r y movement  substrate  to  Armstrong  left  (1985a)  constitute  for  females  that  spring  rates  rare  females  limited  movement  and  environment.  Hankin  females  average  were  mature  undergo  that  than  most  and  magi s t e r  Stevens  Howard in  (1982)  relatively  elsewhere,  he  Page 13 0  concluded observed  this female  Washington,  6.3  was  a  C . magi s t e r  from t h e  Entrance  (1979),  similar  Dinnel habitat  al .  ( 1987 )  Puget  Sound,  et in  PISCES I V .  year  fishery  the  he  that  year  attained  into  legal  sublegal-sized  males  legal  to  due  instar  is  Warner's about  study  the  in  are  structure  (i.e.  moult  frequency  model  in  size  frequency  that  Warner's  Section  respect  model  6.2  did  not  mm i n s t a r  155.0  reasons enter  (see  will  expected include  year  after  that  for  recruited  >90%  of  of  their to  the  50% o f  male  their  will  two  28%  during  about  and  the  60% and  CW)." S i n c e  models  for  fourth  <10% ever  the  .of  attain  yield  the  fishery.  from  to  differences  and  define in  i n f o r m a t i o n on  this  in  growth  the  Fournier size  instar moult  and  conclusions With  included  Schnute  tend  between  different  increments-at-size) study  Dixon  fourth year.  frequency  males  in  MacDonald  during  mm i n s t a r  in their  analysis the  study  ( 1 5 3 . 7 mm  size  this  of  mm CW)  remainder  In t h i s  155.0  possible  when  (159  natural mortality,  the  age  size  year.  the  from males  in  analysis concluded  The  size  high  Differences  legal  the  fourth  northern C a l i f o r n i a ,  settlement.  moulted  size  1987)  C . magi s t e r  their  frequency  in  fifth  male  during  (1985,  attained  during their  crabs  size  followed  after  that  size  Warner  year-class  fourth  legal  Using  year-classes each  determined  attained  Pitcher  modes  a  submersible  (1961)  settlement.  the  in  habitat.  GROWTH AND MORTALITY  Butler  this  preferred  size 1980),  frequency  mean  sizes.  increments-  Page  131  at-size, of  and f u r t h e r , h i s  exploitation  distributions.  of  These  interpretations unusually below,  of  high  and  Fig.  lower  for  survivorship four  alone  may  frequency  10)  lead  may  to  different  Nevertheless,  Tofino  in  resulted  T h e r e f o r e , male  mortality  that  Warner  studied,  the  fishery  of  to  effect  frequency  have  population  recruitment  near  the  size  information.  abundance  page  for  1986  (see  in  high  rates  may  increasing  males  older  than  year s .  the  ages a t  Columbia  Grays Harbor where the  sea  moult  first  estuary,  the  may be  are  apparently  to  for  the  male  Queen  grew  more  (1984)  open  it  along is  the  open  in  the  ( >80 mm CW)  Islands  in  elucidating  differences  C . magi s t e r  in  ocean  temperatures  than  large  Charlotte  British  quickly  adjacent  However, no  between  Water  higher  faster.  differences  Armstrong  i n the  lower.  slightly  in  fishery  C . magi s t e r  were  were  result  and  Washington, than  Tofino  California  also  Stevens  temperatures  there  may  r e c r u i t to  year  increments-at - s ize  central  (Table  from  4.5.1,  33 ) .  Butler that  that  near  that  rates  California.  so g r o w t h r a t e s  note  page  growth  w h i c h males  water  inlets  coast,  in  and  demonstrated  to  considerations  mortality.  Differences in  on  2.2,  and  account  males  size  the  d i d not  legal-sized  population  density-dependent be  analysis  females  (1961) are  study  suggests  years  old,  S e c t i on  6.3  thus  and  two  that  Stevens  years females  those  in  old in the  and when  Armstrong they  the  135.5  149.4  and  are  (1984) =100  mm CW.  mm i n s t a r 161.4  mm  determined  are  This three  instars  Page  are  13 2  probably annual by  four  moult.  Hankin  than  et  a n n u a l l y for  moult  little  from  (Table  4.5.2,  Tofino a  50% chance  fishing  success  time  (Fig.  sustaining  throughout Fig. within  of  Lemmens  Inlet,  densities between  Section  and  of  the  was  in  observed  Charlotte  page  a  (i.e.  for  vary  Islands  area,  4.9.4,  legal  Moulting of  the  profile  shows  soak  a  pattern  (Fig.  C . magi s t e r  4.9.4) because times)  of  less  than  37-50  only days. of  page  mimics  the  76)  for  occurs  virtual for  similar  months  4.9.5  rates  to  that  of from in  observed  apparent  the  (page  samples  success  effort  disguised  1 2 8 . 0 mm  6-9  entry  traps  not  the  over  Figure  fishing was  having  pattern  size  pattern  near  seasonal  year. of  males  more  the  standardized data)  apparently longer  into  most  seasonal  seasonal Inlet  (Fig.  105).  male  for  fishery,  m o u l t t i m i n g and c a t c h r a t e s  6.3  frequently  C . magi s t e r  legal-sized  fishery  moulting  study  The  As  Queen  legal-sized  i n Lemmens I n l e t  fishery  Lemmens  on  s u r v i v i n g the  4.13.3,  the  4.9.4.  rate  (F = 5 . 1 1 - 6 . 9 0 ), w i t h  males  and  mm CW, p a r t i c u l a r l y  female  the  an  study,  less  4.14).  for  undergo  in t h i s  occur  t h a n =145  to  they  33).  which presents  legal-sized  that  may  (Section  California  intensity  the  moults  populations  distribution  instar  77),  the  suggested  increments-at-size  of  of  been  larger  page  Because  has  given  females  central  high  it  old,  that  exploitation  is  years  (1985 ) ,  fished  males,  The  five  However, al .  intensively for  and  outside  (lower  trap  relationship  (n•trap"*-d"*).  Page  133  High for at  fishing  C. magister 7.9,  based  fishing  (1982)  tagged  lasts  to  six  (1978a) year.  Jow  0.8-3.2  was  determined  time  (Table  Estimates  of  recovery  sublegal  for to  F  to  F the  catch-perrange  from  M e t h o t and B o t s f o r d for  the  of  period  legal-sized (Table  suggested  recovered  when  legal  instar  size  frequency  lightly  low  s u r v i v o r s h i p to  survive curves  fished  4.13.5  to  the  from  that  page the No  1951  instar  as  (page  110)  of  a  size  S e c t i on  6.3  in  the  mortality  rate  of  M of and  mm male  performed  strongly  reduced  suggests  likelihood The  Hill the  increasing (1975)  to  catch  same phenomenon with  on  mm i n s t a r .  increases.  species.  for  183.8  those  155.0  the  they  released  the  also  observed  increase  males  of  t h a n the  have  when  An e s t i m a t e  including  indicate  crab  103).  were  have  other  page  tagged  Increasing natural m o r t a l i t y rates for  4.13.1,  males  were  females. been  M=3.48  lack  102).  their  of  s u g g e s t e d by the  fishery,  males  1 5 5 . 0 mm  were  detection  larger  that  the  sublegal-sized  Fig.  recovery  Inlet  instars  in F i g . 4.14.1  tagged  and  analyses,  Holberg  next  97  males  size.  shows  of  2.87-4.37  4.13.5,  was  Table  page  in  A maximum e s t i m a t e  disappearance  4.13.1,  the  C . magi s t e r  high.  M r a n g i n g from  size  in  male  be  4.33-4.48  an  during  Using  estimated  measured  estimated  males  months.  Similarly,  from  been  (1965)  legal-sized  about  range  mortality  s u g g e s t e d by t h e  over  of  on t h e  previously  California.  Gotshall  F  have  1977.  instar  of  which  depending  Natural  was  on r e c o v e r y  estimated  rates  northern  data,  1.18-7.00,  until  in  season,  unit-effort  mortality  for size  reports  portunid  crab,  Page  134  S.  serrata ,  become  from  larger,  increases,  these  The in  the  time  between m o u l t s  and  increasing  and  mortality  rate  study  may  to  explain In  cyclical  nature et  al .  based  on  C. magister  1980,  Botsford  male  legal  size  lower  (M=0.15-0.90  here.  If  for  the  mature  males  populations these  along  models  cases,  perhaps  partly  5+  for  immature  the  be  coast  need  to  total  in  the  mean  tonnage  2.2,  page  Section  6.3  adjusted  have  of  males  rates  much  those  obtained  (see  1986 )  =50%  presented  in  this  immature  W a s h i n g t o n , O r e g o n and  be  the  study  males  in  California,  numerically,  and  in  some  conceptually.  due  for  of  Methot  than  for  other  California  and m o r t a l i t y  rates  justified  in  have  explain  (e.g.  males),  obtained  which  to  1986a,  old),  and m o r t a l i t y  the to  high  SA 24  of  i n 1986  history landed  10).  mortality  rates  density-dependent  u n u s u a l l y h i g h abundance landings  years  males  dynamics  in  shell  likelihood  models  proposed  slower  instar  decreased.  for  population  rates  crabs  next  the  is  for  landings  when  can  may  Conceivably are  growth  growth  instar  1984,  As  Coupled with  estimates  models  of  the  requirements,  next  C.. magi s t e r  life.  attain  implications  particular,  of  increases.  energy  growth  have  year  r e q u i r e d to  the  fisheries.  becoming  energy  third  attaining  attempted  been  to  individuals  this  McKelvey  second  and the  deterioration, of  its  of the  However,  C . magi s t e r were  the  265  t.  fishery,  previous size  10  obtained  factors in  and  frequency  is more  years  this  resulting  1986.  This  in  from  Cancer the  (131+26 t ,  analysis  on  an  magi s t e r  third  than  study  highest  double see  the Fig.  males  in  Page  135  other of  British  Columbia  sublegal-sized  instar.  in  ( 1978b),  using  range  from  Gotshall's obtained method,  M  Ricker  of  a  mm i n s t a r  reasonable  in  his  northern  reason  and  estimates  failing  low  the  to  the  183.8 mm  expectation data,  population  his  estimates  of  near  Tofino  in  1986,  as  M  However,  size  assumption  since  estimated  California.  population of  survivorship  were  not  size  (Leslie  low  natural  be  accepted  of  M cannot  confidence.  crab  considerably abundance  densities  lower  and  than  Station,  provide  opportunity  an  mortality,  appears  crab  life  natural Unlike  adult  stages  adult  C . magi s t e r  S e c t i on  6.3  success B.C.,  by  low  the  comm.).  effect  to  be  pre-recruit  (G.S. Jamieson,  pers.  reliable  appear  Pacific  This  of  may  density  extrapolations  to  on  habitats  densities.  of  of  1987  indicated  measure  more  of  C . magi s t e r .  r-strategists high  population  prediction  unknown.  to  short-lived,  fluctuating  high  Nanaimo,  history  typical  growing,  fishing  facilitating  with different  The  in  declining  Biological  a  155.0  mortality  1975)  For t h i s  Male  the  is  indicated  catch-per-unit -effort  independently, see  also  from t h e  0.88-2.50  estimates  mortality. with  males  Variation  Gotshall to  fisheries  Associated  rate  for  invertebrate  occupy d i f f e r e n t occur  with  species  on  1977):  these  mortality. are  whose  (Caddy 1986), sand,  understood,  so  fast  maturity,  C . magi s t e r  habitats  together  1976,  early  density-independent  mortality many  currently  (Stearns  fecundity,  sizes.  high  as  traits Causes  and is of  presently  juvenile juvenile  and and  density-dependent  Page  136  mortality  may  be  c a n n i b a l i s m of being  important  adults  investigated  California  history  as  loss  showed of v i g o r  Disease C.  important (High  with  obvious  as  the  time  not  believed  predator  1976b,  occasionally  explanation  in  growth,  of  the  cycles  they  the  Hartwick  to  an  but  in  crab  dofleini  course shell  this  is  abundant  traps  of  study  increased.  a  in  to  possibility. (Wulker),  Octopus  during  and  contributor  dofleini  1978 ).  life  deterioration  predation  is  and causes  of  important  Octopus  al.  possible  w i t h i n an i n s t a r  be  Tofino  et  of  spent  physiology,  are  progression  C . magi s t e r ,  caught  example, is  Over  octopus, of  (1976a) observed 0. escapement  the  mortality.  Pacific  For  ( B o t s f o r d and Wickham 1978)  individuals  m o r t a l i t y near  giant  species.  landings.  an  is  magister  The  possible  C. magister  density-independent crabs  a  associated  of  this  on j u v e n i l e s  C . magi st er  Factors  for  this  an  vicinity  dofle ini  were  study.  High  this  p r e d a t i o n on C . magi s t e r  during  trap  experiments.  6.4 YIELD- AND EGGS-PER-RECRUIT Males  under  this  instar)  size  at  a  is  relative  have  a to  6.3  low  to  potential the  size  date.  (similar  ( s p i n e - t o - spine )  S e c t i on  a  future  M=2.5-4.0 there  legal  in  the  probability Figure  the  5.2.3  in  current  minimum  if  males  mm i n s t a r  (<10%) (page  estimates  increase  all  155.0  of  in  shows  >140  size  limit  legal  that  Section  yield-per-recruit legal  50% of  attaining  122)  obtained  (about  of of  for 4.13)  2-3  fold  165 mm CW  mm CW ( s p i n e - t o - s p i n e )  are  Page  137  exploited.  Further  increased the  yield,  but  carapace widths  For  many  reductions presume  accuracy  the  risk  recruitment-overfishing  population  egg  compensated declining stock of  animals  For  and r e c r u i t m e n t has  compensatory  (1986)  stock  such  and  by  poor  fisheries  are  managed  lobster  The  historical minimum egg  protect  has  size  legal  fisheries,  e.g.  between  is  rare  may  not  may be  which  limits  of  exist  invertebrate protect  have  eastern  regulatory  portion  for  As J a m i e s o n  relationships  the  where  been  Canadian measures  population  egg  1986).  seriously  that  limits  (Cleaver  or  many  size  in  documentation  Caddy 1 9 8 6 ) .  recruitment-overfishing  been  consistently  relationships  may  the  resulting  In f a c t ,  by  reducing  relationship  limitations  sufficient  presumption  legal  6 .4  size  fishery,  of  never  found.  of  i.e.  thereby  a  measured.  improved  can be  Consequently,  by  some  a  that  below  because  1973),  i n many c a s e s  ( J a m i e s o n and Caddy  production  Section  in  level  be  fishery  suggest  results  confidently  cannot  a  also  model  responses,  Minimum  possibility  populations  the  relationships  and  ( H . amer i canus )  production  a  recruitment  data.  females.  measures  apparently  limit  (Cushing  been  reliable  disguised  successful  in  (Hancock 1973,  crab s p e c i e s ,  reproductive  in  C . magi s t e r not  in general  notes,  certain  taken  density-dependent  abundance.  invertebrates  for  of  p r o d u c t i o n below  by  size  yield-per-recruit  reducing of  the  f o r w h i c h m o r t a l i t y was  species size  in  the  for 1949,  considered  current  males Poole  C . magi s t e r  because  Canadian  preserve and  for  and  adequate  Gotshall  of  the  American  population  1965,  Methot  Page  138  1986).  Since  females  of  all  relatively not  few  attain  observed  common,  affect  British  females  it  has  been  population  Columbia  sizes  egg  legal  above  size, the  taking  production. show  egg  bearing  size-at-maturity  assumed t h a t  fisheries  and  In  no  are  o n l y males  support  strong  did  of  this,  evidence  of  recruitment-overfishing.  that the  In a p p a r e n t  agreement  all  females  mature  field  catch  contained  curves  in  likelihoods heavily moult is  of  fished  when  typical  al.  sizes  for  females mate  4.14.1  suggest  all  large the  female  presence  Section  6.4  Snow  (page  31),  and  females  in  mating  than  =140  i n the  mm CW may  more h e a v i l y  of  females  a m a t i n g embrace  mature  noteworthy,  to  4.4.1  Such a phenomenon in  1960,  females  however,  of  a  contained  that  C . paqurus pair  is  and  not  fished  of  to  sperm  females  with  have  an  in  female  the  more  may  only  embrace.  It  larger  and  a  1966,  plots  embraces,  the  Elner relative  suggests  that  opportunity  to  populations.  moulting  only  consistent a pair  of  when  accompanied  the  observation  with  sperm p a c k s . (1980)  inhibited  It  suggested  u n d e r g o an a n n u a l moult packs  noted  decreasing  in  Neilsen  which  the  imply  a mating  mate  Brown a n d B e n n e t t  failed  However,  instars  in  study  mm CW) d i s s e c t e d  mature  male  crabs  this  which  larger that  larger  cancrid  110),  Figure  larger  by a male  (page  regions,  (Butler  =115  sperm p a c k s .  attaining  female  males  and m o u l t  that  of  assumption,  than  females  male  1985). of  a pair  Fig.  this  (greater  a c c o m p a n i e d by a  hard-shelled et  with  is that  because  moulting.  Page  One  139  can  not  interpret  females enough  may to  So may  even  reduced from  from  all  in  unfished  et  an  smaller  (Eqn.  5.1.1  1985),  moult. male  155.0  soft-shelled  of  of  mating  many males  females page  and  heavily  egg  moulting  of  males  (2)  fished  production  of  large  population  may  This  producing of  from  a decrease  result  eggs  study,  fecundity  be  females  fewer  this  reduced  still  would  d i s t r i b u t i o n of  116  Both r e s u l t  the  will  that  is  the  is  of  (Fig. never  just  legal  to  each in  to  than  which year  is a  potential  legal-sized  size a  smaller  distribution  4.10.1, mated  page  before  Therefore,  in  an  heavily  exploited  virtually  all  is  by  sublegal-sized  of  81), being  (at  the  in  mode  hard-shelled instar). the it  taken  the  In  percent  is  regional  males  males  perspective,  landing  next  fishery.  mating  many  reproductive  the  frequency  marks have  a  equivalent  mode  size  fishery  From  male  mm i n s t a r )  consideration with  absence  population.  C . magi s t e r  mm CW ( a t  males  a  frequency  on  s o f t - s h e 11ed.  of  the  the  population.  intense  are  size  with  al.  by t h e  128  i n the  to  a  that  females  an  whether  females.  to  landing the  larger  by  relative  fails  landed  inhibited  population  Hankin  In  results  mated,  sizes,  matings  male  though  females  female  been  w i t h the  a shift  smaller  their  been  (1)  larger  have  mate  have  from  likely by  the  fishery, 155.0 mm  instar .  Intense by  males  Section  6.4  fishing  being  results  reduced  in by  the =50%  number  of  relative  potential to  an  matings unfished  Page  140  population. on  how  well  females (page the  The a c t u a l  sublegal-sized  than  120)  male  they  would  indicates  population  on p o p u l a t i o n  egg  The the  an  that  exploitation  >10:1  female of  reduce  unfished  males  includes lost  =10:1  (for  surplus  analysis  in  above  the  In  be  more  Figure  5.2.1  M=2.5),  for  impact is  that which  fishing.  this  study,  processes,  which  suggests  minimum l e g a l  by  up  to  50%  consideration  of  this  as  the  implication  current  reinstated  ratio  mating p o t e n t i a l  recruitment-overfishing  should  depends  mating  F:M mating  The  due t o  eggs-per-recruit  of  fisheries  above  by  population.  potential  reproductive  population.  possibility  the  matings  compensate  production decreases.  eggs-per-recruit and  number o f  unfished  as  mating p o t e n t i a l  male  might  in  i n the  males  increases  an F : M m a t i n g r a t i o can b u f f e r  decrease  in  a  modeled  that  high  size  relative  limit to  conclusion,  heavily  concern  an the  exploited  for  fisheries  manager s .  Full more  confidence  complete  presented  there  are  this in  variables.  which  quantify,  and  the  Section  most  In  F:M  6.4  are  of  reproductive  is  based  on  estimates,  in  in  the  this  analysis ratio,  to  (1)  generally  (2)  mating  eggs-per-recruit  attempts  uncertainties  processes  is  study  these  Like  processes.  the  understanding  in  uncertainty  in  the  of  the and  important  processes  representation are  difficult  numerical  particular  and  population  natural  but  a  The model  estimates,  understanding  important in  best  numerical  conceptual  requires  behavior.  simulate  understood,  model  the  of  of to  natural  uncertainty functional  Page  141  response  of  important  the  F:M  conceptual  frequency  and  mating  ratio  to  uncertainty  its relationship  to  female  concerns  the  density.  female  availability  The  moulting  of  males for  mat i ng. Reproductive  biology  seasonality  of  s p e c i e s but  i n f o r m a t i o n on  F:M  egg  hatching)  mating r a t i o s ,  pattern)  is  crustaceans behavior  i s not  dynamics  of  elusive  described  but  for  many  female  poorly  knowledge  of  regard  to  the  i n f o r m a t i o n to adequately sperm  packs  does,  c o n t r i b u t e to  or  present  study,  the  reproductive  viable  eggs  does  not,  moult  i n the  strategy future.  i s the  explanations  there  is  annually.  crab  of  (Blau  one  that  risk  females  do  not  favourable the  Section  lower  6.4  the  moult  suggestion  and  i f they  have a p a i r  e v o l u t i o n a r y argument. risk,  then  the  more  relative  the  favourable  a  i n terms of  and  producing  (1980) that  of sperm packs If mating  most  producing  Bennett  of  1977), the  produces  for a female,  of Brown and  a pair  Using  f u t u r e p o p u l a t i o n egg p r o d u c t i o n , than not moulting fewer eggs, then  insufficient  (Stearns 1976,  I f mating, moulting  l a r g e r c l u t c h of eggs i s a higher  has  for  population  debate whether a female w i t h  production as a measure of f i t n e s s  better  more  moulting  and the A t l a n t i c snow crab ( E l n e r and B a i l e y 1986). With  egg  (e.g.  reproductive  the recent sharp d e c l i n e s i n l a n d i n g s of the red k i n g 1986)  crab  understood  f o r understanding may  fecundity,  i n nature  activity,  remains  Increased  important  C. magi s t e r ,  been  of mating and  general. only  has  age-at-maturity,  r e p r o d u c t i v e behavior  duration  more in  (e.g.  and  argument  i s the moulting i s that  Page  142  females life  s h o u l d not  history  influences Fig.  is  how  4.14.1,  are  110)  there  deprived  is  of  males  not  without  mating  she  has  little  year.  In  the in  following terms  of  strategy female  in  can  future  moulting u n t i l  and  of  physiological  and  suitable occur.  to  Christy  Section  is  6.4  found,  males  to  1969,  mating  centered  applies  that  the  attract  to  mate  more one  the  competition', mating  competitively  a  should natural  and  fit  moult  female,  that  delays of  shift  this  in  the  sizes.  behavior between  requires mating  males  and  is  she  behavior  of  search  and  is  a is  Once  subsequent  which  The  that  when 1987).  a  males  mating.  in general  Christy  ritual  females unfished  high  control  brachyuran crabs  (Hartnoll  an  the  the  smaller  that  to  g r o w t h and  The c o n s e q u e n c e  interactions  pheromone  'female  (1987)  means  a  moult  mate For  found.  factors  for  important  and t h e r e f o r e  the  reproductive  the  argument  is  in  p o p u l a t i o n w o u l d be  physiological  secretes  preparing  this  the  natural  So,  surviving  production,  fished  curves,  c i r c u m s t a n c e when  considering of  is  have  and f e m a l e  mated,  frequency d i s t r i b u t i o n to  females,  female  male  circumstance,  mate  C . magi s t e r catch  can  mating.  be  since,  this  female  which  species.  for to  for  This  no n a t u r a l  chance  a suitable  Understanding knowledge  the  expect  egg  a heavily  size  of  suitable  a  mortality,  interpreted.  be  population moult  female  (e.g.  u n d e r s t a n d i n g of  seems t o  U n c e r t a i n t y about  explanation  information  management  current  mating.  correct  biological  for  W i t h our  without  the  page  implications  mortality,  moult  a  mating  the  Cancer  label spp.,  aggressively  Page  143  defend  their  after,  the  release  of  (Christy for  female actual  release  prior  to  a  physiology moulting  information not  Also, C.  packs.  to  the  pagurus  females study,  yet  moult  for  that  mature  do  Brown  packs  few this  in  but  be  not  absence  packs  a  there  do  with  C . magi s t e r  males  in  Bennett  not  moult  the  females,  all  that  endocrinology  why  with  and  males  are  have  laboratory  not  of  population  packs  does  of  the  reproductive  (1980)  larger  in  no p r o o f  suitable  sperm  cancrid  urine  females  if  and  attain  that  species.  explained  moult  of  occur  the  for  the  may a l s o  is  the  of  crabs  their  if  perhaps  portunid  evidence  different to  and  evidence  understand  females  with  all  indirect  needs  of  sperm  for  pheromone  is  suggestion  with  strong  and determine  the  sperm  is  suggested  we  mature  before,  any b r a c h y u r a n c r a b  females  in  days  ( C h r i s t y 1987),  It  suggests  available,  observed  (1966)  reproduction  sperm  few  males  some  C . magi s t e r .  and  a  attract  is  exists  critical of  to  water-borne  moulting  is  without  There  There  a m a t i n g pheromone  It  mating.  and Edwards  C . pagurus .  days  for  a pheromone  1987),  females  partners  been tanks.  that  female  explain  instars. sizes,  how  In had  this sperm  packs .  An 1978,  'experimental  Hilborn  deliberately males,  and  improve Some  our  and W a l t e r s altered  6.4  1981),  by v a r y i n g  p r o h i b i t i n g , the understanding  questions  Section  management'  regarding  approach where  the  landing of  the  (Walters  F:M mating  minimum l e g a l of  females,  C . magi s t e r  reproductive  and  size would  reproduction  behavior  can  be  Hilborn ratio  limit also  is for help  dynamics. addressed  Page  144  only  by  experimentation  example,  experiments  population  structure  relatively  low  mating  the  large  and  scale  for  resulting  scale  and t h e  this  test  minimum  relationship  males  to  opportunities,  Without  at  possible  from  legal  be  limit,  observed  absence  of  between larger  one  the  degree  above  laboratory.  be  certain  that  exploitation  (Section  a  eliminating  a  of  For female  males  in  cannot  females  in  thereby  performed  experimentation  1986).  changes  harvesting  size  cannot  (Walters  4.14)  is  of  'cause  effect.  An  ideal  fishery  with  ensure  that  affected study  near  an  near  would  exogenous  larval  by  Jamieson  location  and  recruitment  Tofino  are  the  Washington,  coast  of  to  the  to  have  Oregon,  that  hatched  hatched  would  of  these  suggest  have been  site  exploited  location  population  meets  press)  intensely  Such a  apparently  unlikely  l i k e l y to  supply.  The  (in  They a r e more  small,  treatments.  (SA 24)  Phillips  a  larval  experimental Tofino  be  the  be  present since  larvae  settling  local  females.  from f e m a l e s or  not  criteria  from  California  would  from a l o n g  northern  British  Columbi a .  The b a s i s above  a  current from a  minimum minimum  a  s u c h an e x p e r i m e n t legal legal  C . magi s t e r  minimum  increase such  of  size  size  experiment  6.4  limit limit  population. limit  yield-per-recruit  an  Section  legal  size  were  would  by  considerably of  165  Figure  of  140 a  involve  removing lower  than  5.2.3  of  implemented  the  mm CW ( s p i n e - t o - s p i n e ) (page  122)  suggests  mm CW ( s p i n e - t o - s p i n e  factor  males  three in  (at  SA 2 4 ,  )  might  M=4.0).  If  increased  Page  145  yieId-per-recruit The  high  single  might  annual  If  males  mm CW ( s p i n e - t o - s p i n e  and  moult, in  then  with  very  few  page  31).  distributions attaining =120  the  in  legal time  landing  There  tonnes  limit  on  recognized  Section  essentially  statistics  to  from  to  a in  6.4  the  high  yield 140  shift  an  in  should one  may  a  reflect  rate  this  limit  of  female  with  base  Tofino  also  (See  size  Fig.  frequency  few  increment  data  mate  should  mated  distributions  near  size  o p p o r t u n i t y to  occur  moult  quality  resulting  mm CW near  intervention from  females  greater for  over has  than  assessing  time, been  pre-  sets  cases.  For  while  only  a  simulated (oc=.05)  F o r the  be  since sampled  example,  the  means,  years. for in  tonnes  remaining  11  cases  on  the fold  the  mean  variance should  be  Intervention  years  increase  using  three  over  maintaining  data  minimum  1986) a  post-1986  few  the  detected  (Noakes  and p o s t - i n t e r v e n t i o n in  of  lowering  T o f i n o might  statistics  1954-1986,  from  analysis  SA 24.  landing  significant 39  a  than  legal  mm CW b e i n g  frequency  detected 50  minimum females  >120  sizes  a  in  SA 24  statistically  year  of  statistics.  1985.  step  landed  analysis  landing  Tofino,  exploitation  fishery  statistics  proportional  one  is  size  since  in  high  females  crab  series  increase  a  ) denies  much l a r g e r  increase  size  a  above  smaller  female  extensively  a  to  Dungeness  An  near  landing  Consequently,  sizes  mm CW.  trends  future  abundance.  140  4.4.1,  in  rate  suggests  exploiting  result  evident  exploitation  year-class,  population  be  post-1986  landed a  after  significant  Page  146  increase  was  dramatic  increases  have  had  to  over  landings  is  detected  series  systems,  prior  lowered.  are  obvious  an  With  year  all  difficult. fishermen  to  be  et  al.  for  that  if  the  suited  the to  tell  knowledge  because  them of  a  and  in  the  in  be  very  of  successful, they  the  perturbations  to  requirements.  cannot  concerns  about  crabs  not  size  to  limits  in  could  to  be  convince  only  be  benefit  the  being  region  experiment.  will  is  protect  SA 24  the  in  limit  Columbia  difficult  it  reader of  than  management  increase  The  size  perhaps  would  power  British  other  less  difficulties  larger  is  type  that  1987.  closures  of  area  is  in  minimum l e g a l  regions  would  significant  political  exceptional  this  experiment  Landings  detecting  fisheries  Tofino to  detect.  regarding data  enforcement  it  Obviously,  ( 1 9 7 8 ) who t e s t e d  where  (with  less.  detected  analyses  fisheries  difficult  Then  perhaps from  more  this  relationship  new  between  and r e c r u i t m e n t .  Marketing buyers size.  shucked 140  1987  regional  Initially  biologically  crab  1987  managerial  males),  contemporaneous  since  for  in  experiment  round  soft-shelled  stock  to  t  Lettenmaier  or  longer  and who p r o v i d e g u i d e l i n e s  implementing  later,  to  years  take  433  intervention  There  open  five  would  exceeded  r e f e r r e d to  time  in  for  smaller seem  This  is  their  to  be  Section  6.4  changes  more  anticipated  interested  p a r t i c u l a r l y true meat.  mm CW ( s p i n e - t o - s p i n e  requesting  is  in  However, ) to  be  for  in  landed  buyers  allowing  to  of  males  landed could r e s u l t  regulations  governing  the  be  a  problem  volume crabs as in  size  than to  be  small  as  fishermen of  escape  Page  147  ports.  Currently  escape  port  each  with  an  From Table 4 . 7 . 2 . 2 which  are  require  it  commercially  for  crabs  <145  interventions  by  have  diameter  47)  near  least  not  one  less  seen that  circular  than  100 mm.  Traps  B and D, retention  Tofino,  have  poor  Issues  such  as  this  tend  to  lessen  mm CW.  of t h i s  at  of  can be  fishery  l i k e l i h o o d of experiments 6.5  must  inside  (page  fished  capabilities  trap  managers s c a l e being  which the  implemented.  SUMMARY  In  conclusion,  the  main  findings  C. magi ster p o p u l a t i o n dynamics near T o f i n o , 1. summer  Males i n the two  years  f o l l o w i n g 1.5  settlement,  to a t t a i n the  i n s t a r with l e g a l - s i z e d  males.  frequency  commercial  correct instar  analysis  for  on  differences  began  to  form  in  The s i z e  (Butler  1960)  during  suggested that 155.0  near t h i s  Section  summer  moulted  twice  during  155.0+11.2 mm i n s t a r ,  trap time,  the  samples  the  the the  first  showed  spring,  standardized that  three  form throughout the  two  most  the  to  155.0 mm  years  after  remainder of  the  males  are  not  sexually  active  years  m a t u r i t y i n the 100.7+12.8 mm i n s t a r after  s i z e and produce eggs the  6.4  B . C . are:  mm i n s t a r .  2. Females reach sexual the  of  frequency d i s t r i b u t i o n of males w i t h mating marks  before a t t a i n i n g the  during  study  A mark-recovery program, and s i z e  soak  s e t t l e m e n t , and continued to year.  this  102.9+9.8 mm i n s t a r , which dominated i n  after  years  of  settlement.  They f i r s t  f o l l o w i n g winter w h i l e  mate in  the  Page  148  119.4+11.0 mm instar,  instar.  the  bulk  They appear  of  the  moulting  months when m a t i n g a c t i v i t y 3.  There  appear  to for  California  Queen  to  ascertained  if  differences 4.  the  instantaneous  occurring  small  male  and  after  during  differences female  Charlotte  C.  Islands.  differences  suggest that  of  males the  spends w i t h i n  of  mortality  rate  for  or  annually  the  this  summer  high.  only  mortality  natural  2.87-4.48  moult  are  in  the  moult  magi s t e r  from  It  could  biological  or  not  be  due  to  i n measurement.  Natural  (Female  during  these  is  be  increments-at-size  to  males was  natural mainly  not  instar  shortly  in  the may  a  moult  (M)  and  was  mm  as  that  higher  than  high. annual  estimated  the  the  be  The  instar.  increase  is  to  estimated).  155.0  increases,  after  estimated  mortality  mortality rate  an  was  at  The  time  data a  male  mortality  rate  the  intermoult  mortality. 5. judged  Movement, as not  to  a v e r a g e , <30  be  m per  deeper water d u r i n g then  return  to  d e t e r m i n e d by  extensive. day. the  Most  T h e r e was winter,  shallower  mark - r e c o v e r y  water  males  coast , perhaps  preferred  S e c t i on  to  females  on  e v i d e n c e t h a t males r e t r e a t  to  perhaps to avoid the  incubate  was  moved,  following  f e m a l e s were o b s e r v e d t o move f r o m t h e exposed  and  methodology,  and  coastal  rough water, spring.  and  Maturing  i n l e t s to the  release  their  eggs  more in  a  environment.  6.5  Page  149  6. greater  The  fishery  than  the  near  minimum  1 5 5 . 0 + 1 1 . 2 ram i n s t a r . enter  the  There  remains  fishery  age-class natural  which  1985 a  percentage four  about its  fishery  (Warner  of  154  year the  the  in  1987)  males  may  be  instantaneous  rate  of  Due  less  155.0  mm  instar  of  this  to  high  than  10%  instar  year.  when  of  during However,  suggests  caught  the  settlement.  year.  that  males  this  proportion  following  1985,  of  mm CW i n  after  fourth  the  mainly  males  determined  attained  legal-sized  the  fourth  during  the  limit  of  their  that  enter  The a n n u a l  legal-sized  from  size  50%  study  composed  a  greater  older  than  years .  7.  was  this  California of  is  uncertainty  males  s u r v i v e d to in  About  recruits  mortality,  study  legal  during  some  sublegal-sized  Tofino  males,  estimated fishing  samples  as  at of  5.11-6.90. <1%.  standardized  confirmed  a  determined  very  Size to  degree  males.  mortality  sublegal-sized  statistics year-class  8.  from  Size  samples  soak  times  Section  by  6.5  SA 24  may  an  analysis  for  on  differences  of  exploitation  consideration males  mark-recovery  of  i n the  reflect  the  155.0  annual  program, survival  commercial in  soak  trap times  (=60-100%) high  of  natural  mm i n s t a r ,  population  of  landing  abundance  and  strength.  trap  caused  In  a  indicates  frequency  legal-sized of  This  correct  high  from  f i s h i n g m o r t a l i t y (F)  frequency changes for  (1)  and abundance  with  otherwise the  i n f o r m a t i o n from  increasing replicate  dynamics  of  soak  trap  entry  time. samples  and  exit  commercial  Differences produce over  in  biases  time,  Page  (2)  150  changes  in  bait  effectiveness  i n t e r a c t i o n s between enter  that  trap.  over  crabs w i t h i n Several  time,  a trap  The r e s u l t s  used  sampling  to  improve  the t r a p  e f f e c t s of d i f f e r e n t 9.  legal  size  above t h e s i z e  in  about  lower near  a  size  size three  limit  Tofino,  increased  limit  limit  minimum l e g a l  were  performed  of these  data  by  which  e x p e r i m e n t s were  correcting  f o r the  analysis  indicated  o f 165 mm  CW  optimizing yield.  limit  t o 140 mm  fold  increase  CW  that  the  current  (spine-to - spine ) i s well For example,  lowering the  ( s p i n e - t o - s p i n e ) may  in yield-per-recruit .  t h e h y p o t h e s i z e d improvement  landings  may  be  statistically  landings  i s large  fishery  enough  d e t e c t e d by t i m e  i n less than f i v e  n e a r T o f i n o i s a r g u e s t o be an e x c e l l e n t  result If this  i s t e s t e d e x p e r i m e n t a l l y i n the r e g i o n a l  a n a l y s i s of annual  an  agonistic  soak t i m e s .  Yield-per-recruit  minimum  (3)  and c r a b s a t t e m p t i n g t o  experiments  measured these p r o c e s s e s .  and  years.  The  that series  fishery  location to perform  such  experiment. 10.  mating male  D a t a on t h e c a r a p a c e w i d t h s o f m a l e s pairs  required  suggested  permitted a by  females  a  female larger  f i n d i n g a male p a r t n e r greater rare. growth  females  stagnation  at  in a than  estimate  mating  =140 CW  legal  moult  size  would  when  instars  limit  mating,  smaller  of  the size  embrace.  i n heavily exploited  t h a n t h e minimum Since  quantitative  and females forming  The  have  fisheries o f 154 mm this  than  would  results  difficulty since CW  might  of  males  would result  otherwise  be in be  a t t a i ned.  Section  6.5  Page 151  11. in  A l l females  this  study  spermathecae relative that  contained by  a  sizes  no  male.  fished  population.  Large  larger  males  region  of  and  sperm  not  females  were  most  abundant  in  in  from  fishing  the  suggest with  intensely  four  regional  in  most  a  an  supported  abundant the  their of  strongly  available  heavy  in  h a v i n g mated  samples  to  dissected  consideration  without  trap  were placed  results  be  light  packs  In  such  instars  may  least  mm CW t h a t  mating.  Commercial  Large  =115  pairs,  experienced  interpretation. fished  pair  mating  larger  than  during  attain  which  a  male  of  females  fisheries  greater  the  this  lightly  heavily  fished  region.  12. fishery  Eggs-per-recruit population  relative  to  shift  female  to  in  growth  mating,  an  size  (2)  smaller  each  no  strong  evidence  C.  magi s t e r  C.  magister  important  Section  of  of  6.5  This  males  fails  to  mate  but  I  reconsider and  American  if  production life  of  populations  history  by  for  (3)  British  reduced There  managers  size  of that  limits  egg  production.  are  maintained  compensatory  is  Columbia  presumption  legal  a  suitable  moult.  minimum  (1)  due  and  that  50%  sizes  and  in  to  from  eggs,  historical  population  or  size  intense  up  smaller  a  recommend the  an  by  results  of  fewer  to  in  reduced  recruitment-overfishing  distinguish  in early  of  producing  protection  egg  be  that  distributions  lack  female  Canadian  to  protection mortality  a  fisheries  adequate  a  females  fisheries,  current  provide  from  year  may  population.  frequency  stagnation  indicated  production  unfished  fecundity  the  egg  analysis  It by  is the  density-dependent  stages.  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