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Seasonal movements and foraging behaviour of resident killer whales (Orcinus orca) in relation to the… Nichol, Linda M. 1990

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SEASONAL MOVEMENTS AND FORAGING BEHAVIOUR OF RESIDENT KILLER WHALES fOrcinus orca) IN RELATION TO THE INSHORE DISTRIBUTION OF SALMON (Oncorhynchus spp.) IN BRITISH COLUMBIA By Linda M. N i c h o l B.Sc.  ( Z o o l . ) / U n i v e r s i t y o f B r i t i s h Columbia, 1985  A T h e s i s submitted i n p a r t i a l f u l f i l m e n t o f the requirements f o r t h e degree o f Master o f Science In The F a c u l t y o f Graduate S t u d i e s (Department o f Animal Science) We accept t h i s t h e s i s as conforming to t h e r e q u i r e d standard  University of B r i t i s h  Columbia  J u l y 1990 (§) Linda M. N i c h o l 1990  In  presenting  degree freely  at  this  the  available  copying  of  department publication  of  in  partial  fulfilment  University  of  British  Columbia,  for  this or  thesis  reference  thesis by  this  for  his  and  scholarly  or  thesis  study.  her  for  of  Animal  financial  Science  The University of British C o l u m b i a Vancouver, Canada  Date  DE-6 (2/88)  September 14,  1990  I  I further  purposes  gain  the  shall  requirements  agree  that  agree  may  representatives.  permission.  Department  of  be  It not  that  the  Library  by  understood be  an  advanced  shall  permission for  granted  is  for  allowed  the  make  extensive  head  that  without  it  of  copying my  my or  written  ABSTRACT  S i g h t i n g s and a c o u s t i c r e c o r d i n g s from 1984 t o 1989 o f n o r t h e r n r e s i d e n t k i l l e r whales  fOrcinus orca) from Johnstone  S t r a i t o f f n o r t h e a s t e r n Vancouver I s l a n d and from K i n g I s l a n d on the  c e n t r a l B r i t i s h Columbia coast were a n a l y s e d t o examine the  h y p o t h e s i s t h a t n o r t h e r n r e s i d e n t whales move s e a s o n a l l y i n t h e i r range t o areas where salmon are a v a i l a b l e . K i l l e r whales were most abundant  i n Johnstone S t r a i t between J u l y and October and  i n f r e q u e n t d u r i n g the remainder of the year. The i n c r e a s e i n whale abundance d u r i n g summer c o i n c i d e d w i t h t h e m i g r a t i o n of salmon  (Oncorhynchus spp.) from o f f s h o r e i n t o Johnstone  Strait.  The o c c u r r e n c e near King I s l a n d i n s p r i n g 1989 o f the same r e s i d e n t whales t h a t are seen i n Johnstone S t r a i t d u r i n g summer, c o i n c i d e d w i t h runs o f sockeye and chinook salmon. During J u l y , August and September o f 1984 through  1988,  k i l l e r whale s i g h t i n g s were recorded v i r t u a l l y d a i l y i n the Johnstone S t r a i t . O b s e r v a t i o n s of k i l l e r whales i n Johnstone S t r a i t d u r i n g the summer of 1988  showed t h a t whales foraged along  shore and i n areas of s t r o n g c u r r e n t where salmon o c c u r i n h i g h d e n s i t i e s . Of the 16 k i l l e r whale pods i n the n o r t h e r n r e s i d e n t community, however, l e s s than h a l f were p r e s e n t more than 15% o f summer days  (1984 t o 1988). R e g r e s s i o n r e s u l t s between numbers of  whale days per week from each pod and numbers of salmon per week showed t h a t the occurrence pods t h a t were p r e s e n t on more than 15% o f  summer days i n Johnstone S t r a i t was p o s i t i v e l y and  iii s i g n i f i c a n t l y a s s o c i a t e d w i t h the abundance o f sockeye  and p i n k  salmon ( s i x pods). In a d d i t i o n t o these, t h e occurrence o f one pod t h a t spent l e s s than 15% o f summer days i n t h e S t r a i t was p o s i t i v e l y and s i g n i f i c a n t l y a s s o c i a t e d w i t h chum salmon. Together  these r e s u l t s support the h y p o t h e s i s t h a t  n o r t h e r n r e s i d e n t k i l l e r whales s e l e c t t h e i r h a b i t a t s e a s o n a l l y t o feed on a v a i l a b l e salmon. The r e s u l t s a l s o l e a d t o t h e h y p o t h e s i s t h a t w i t h i n the northern r e s i d e n t community each pod has a seasonal home ranges.  iv TABLE OP CONTENTS ABSTRACT LIST OF TABLES  i i V  LIST OF FIGURES.  vi  ACKNOWLEDGEMENTS  v i i  INTRODUCTION METHODS 1) Study Animals 2) Study Areas 3) S i g h t i n g Records 4) A c o u s t i c Records 5) Salmon Abundance E s t i m a t e s 6) E s t i m a t i n g t h e Abundance o f K i l l e r Whales i n Johnstone S t r a i t throughout t h e Year 7) R e g r e s s i o n Analyses 8) B e h a v i o u r a l Sampling  1 7 7 7 9 14 16 17 19 20  RESULTS 23 1) Occurrence o f K i l l e r Whales i n Johnstone S t r a i t Throughout t h e Year.. 23 2) Salmon Abundance and K i l l e r Whale Occurrence i n Johnstone S t r a i t 25 3) Salmon Abundance and K i l l e r Whale Occurrence Near King I s l a n d 29 4) Pod Usage of Johnstone S t r a i t During Summer 29 5) R e g r e s s i o n R e s u l t s Between t h e Occurrence o f K i l l e r Whales and t h e Abundance o f Salmon i n Johnstone S t r a i t 33 6) Behaviour o f K i l l e r Whales 38 DISCUSSION 40 1) Occurrence of K i l l e r Whales and Salmon I n Johnstone S t r a i t and Near King I s l a n d 40 2) The R e l a t i o n s h i p Between t h e Ocurrence o f K i l l e r Whales and Salmon i n Johnstone S t r a i t During Summer 40 3) F o r a g i n g Behaviour o f R e s i d e n t K i l l e r Whales..42 4) Pod Home Ranges 46 CONCLUSION  52  LITERATURE CITED  53  V  LIST OP TABLES Table I. Table I I .  Weeks o f c o n s e c u t i v e d a i l y observer e f f o r t i n Johnstone S t r a i t used i n a n a l y s i s  13  Months from which a c o u s t i c r e c o r d i n g s were a n a l y s e d and from which p r e v i o u s l y analysed data were used 15  T a b l e I I I . Pods p r e s e n t i n Johnstone S t r a i t d u r i n g seasons of the y e a r 1985 t o 1989  different  i n Johnstone  27  T a b l e IV.  Numbers of salmon ( i n thousands) J u l y t o October, 1984 t o 1988  Strait, 30  T a b l e V.  M u l t i p l e r e g r e s s i o n r e s u l t s , between weekly numbers of whale days, from each n o r t h e r n r e s i d e n t pod, and weekly numbers of salmon i n Johnstone S t r a i t d u r i n g J u l y , August and September, 1984 t o 1988 36  vi  LIST OF FIGURES F i g u r e 1. Map o f B r i t i s h Columbia c o a s t l i n e showing ranges o f t h e northern and southern r e s i d e n t k i l l e r whale communities, major salmon migratory r o u t e s and t h e two study areas  8  F i g u r e 2. Map o f Johnstone S t r a i t study area  10  F i g u r e 3. Map o f King I s l a n d study area  11  F i g u r e 4. A comparison o f t h e number o f whales p r e s e n t i n Johnstone S t r a i t on 27 days d u r i n g J u l y , August and September o f 1980, 1981, 1982 and 1983, estimated by v i s u a l o b s e r v a t i o n and by a c o u s t i c m o n i t o r i n g 24 F i g u r e 5. Mean number o f whale days p e r month estimated s i g h t i n g s and a c o u s t i c data i  from 26  F i g u r e 6. Mean number o f salmon ( i n thousands) and whale days per week i n Johnstone S t r a i t d u r i n g J u l y , August, September and October (1984 t o 1988)  28  F i g u r e 7. Frequency o f occurrence o f a l l o r p a r t o f each n o r t h e r n r e s i d e n t pod seen i n t h e King I s l a n d study area d u r i n g May and June 1989  31  F i g u r e 8. Number o f whale days each week i n t h e King I s l a n d study area d u r i n g May and June 1989  32  F i g u r e 9. Frequency o f occurrence o f a l l o r p a r t o f each n o r t h e r n r e s i d e n t pod i n Johnstone S t r a i t d u r i n g J u l y , August and September, 1984 t o 1988  34  F i g u r e 10.Mean number o f whale days p e r week d u r i n g J u l y , August and September, 1984 t o 1988 35 F i g u r e 1 1 . C o r r e l a t i o n between t h e percent time spent i n Johnstone S t r a i t by pods d u r i n g J u l y , August and September and the s t r e n g t h o f t h e r e l a t i o n s h i p w i t h salmon  37  vii ACKNOWLEDGEMENTS I would l i k e t o thank Dr. David Shackleton, my s u p e r v i s o r for  h i s support and encouragement. I would a l s o l i k e t o thank Dr.  Kim Cheng f o r a c t i n g as my  s u p e r v i s o r w h i l e Dr. S h a c k l e t o n was  on  s a b b a t i c a l . The members of my committee, Drs. A. Harestad, J . Ford and L. Gass a l s o p r o v i d e d a s s i s t a n c e through v a l u a b l e c r i t i c i s m and d i s c u s s i o n . To Dr. M. Bigg, a s p e c i a l thanks f o r t a k i n g an i n t e r e s t i n my  study and h e l p i n g me Dr. D.  Symonds  each  a t v a r i o u s p o i n t s a l o n g the  Bain, Dr. M.  gave  me  the  Bigg, J . Jacobsen,  use  of  their  killer  way.  P. Spong and whale  sighting  r e c o r d s . Dr. J . Ford, P. Spong and H. Symonds a l s o allowed me use t h e i r a c o u s t i c r e c o r d i n g s and C. Guinet allowed me a c o u s t i c d a t a . L. Hop-Wo, S. Hutchings, W. the Canadian  H.  to  t o use h i s  Luedke and P. S t a r r o f  Department of F i s h e r i e s and Oceans p r o v i d e d data  on  salmon abundance. Q. field  i n 1988.  Muelder ten Kate In 1989,  and  J. Ripley assisted  me  i n the  Dr. D. Bain, B. K r i e t e and myself combined  f o r c e s t o c a r r y out a k i l l e r whale survey near King I s l a n d . I thank them both f o r i n c l u d i n g me  i n t h i s v e n t u r e . I would a l s o l i k e t o  thank Jim and Ann Borrowman and B i l l and Donna MacKay o f Telegraph Cove f o r g i v i n g support i n so many ways d u r i n g both f i e l d  seasons.  F i n a n c i a l support was p r o v i d e d through a G.R.E.A.T. award from the B r i t i s h Columbia  Science C o u n c i l i n c o o p e r a t i o n w i t h the  Vancouver P u b l i c Aquarium and by the Ann V a l l e e E c o l o g i c a l  Fund.  West Coast Whale Research and Education Foundation, generously gave me use of a Boston Whaler and outboard engine i n  1988.  1  INTRODUCTION  Food i n f l u e n c e s p a t t e r n s o f movement, home range s i z e s , s o c i a l s t r u c t u r e and t e r r i t o r i a l i t y  i n many animals. Seasonal  movements a r e common among mammals because food  availability  fluctuates seasonally i n v i r t u a l l y a l l habitats  ( S i n c l a i r 1983).  The s i z e o f areas over which i n d i v i d u a l s o r groups range depends on food a v a i l a b i l i t y and d i s t r i b u t i o n  (Macdonald 1983). Group  s i z e s o f p r e d a t o r s and t h e e v o l u t i o n of c o o p e r a t i v e h u n t i n g a r e r e l a t e d t o prey type and hunting t a c t i c s  (Kruuk 1975; Packer and  Ruttan 1988). The o c c u r r e n c e o f t e r r i t o r i a l i t y depends on t h e abundance and d i s t r i b u t i o n o f a resource  ( i n t h i s case food) and  whether i t can be e c o n o m i c a l l y defended (Brown 1966). T h i s t h e s i s d e s c r i b e s how salmon abundance  (Oncorhynchus spp.)  i n f l u e n c e s the movements and d i s t r i b u t i o n o f r e s i d e n t  k i l l e r whales  (Orcinus orca) i n B r i t i s h Columbia. K i l l e r whales  occur throughout most oceans i n both p e l a g i c and c o a s t a l h a b i t a t s (Dahlheim 1981; Leatherwood and Reeves 1983). The most d e t a i l e d s t u d i e s , however, have been conducted i n c o a s t a l B r i t i s h Columbia and n o r t h e r n Washington s t a t e  (Balcomb e t a l .  1982; Bigg 1982;  Ford and F i s h e r 1982). These s t u d i e s show t h a t k i l l e r whales i n the P a c i f i c Northwest a r e h i g h l y s o c i a l and l i v e i n c o h e s i v e groups c a l l e d  "pods" (Bigg e t <al. 1987) . These pods form t h r e e  s o c i a l l y i s o l a t e d communities with d i f f e r e n t ranges (Bigg e t a l . 1987). The  "northern r e s i d e n t community" ranges from mid  Vancouver I s l a n d  n o r t h t o t h e Alaskan b o r d e r . The "southern  r e s i d e n t community"  ranges from mid Vancouver I s l a n d south i n t o  Puget Sound and t h e S t r a i t o f Juan de Fuca. The range o f t h e " t r a n s i e n t community"  o v e r l a p s both r e s i d e n t ranges.  Transients  and r e s i d e n t s do not mix but a c t i v e l y a v o i d each o t h e r  (Bigg  1982). World-wide, k i l l e r whales e a t a v a r i e t y o f f i s h , cephalopods, al.  p i n n i p e d s and other cetaceans  (Hoyt 1984; Lowry e t  1987; R i c e 1968). W i t h i n p o p u l a t i o n s , however, k i l l e r whales  may feed p r e f e r e n t i a l l y on s p e c i f i c prey types and move s e a s o n a l l y t o areas where these prey a r e abundant  (Heimlich-Boran  1986) . E a r l y observers o f k i l l e r whales i n Puget Sound and o f f n o r t h e r n Vancouver I s l a n d suggested  t h a t k i l l e r whales f e d on  salmon (Rice 1968; Spong e t a l . 1970). L a t e r s t u d i e s (Bigg e t a l . 1987)  suggested  t h a t k i l l e r whales i n t h e n o r t h e r n and southern  r e s i d e n t communities, feed on salmon and o t h e r f i s h because o b s e r v a t i o n s showed k i l l e r whales o c c u r r e d p r e d i c t a b l y each summer i n s p e c i f i c areas w i t h i n t h e i r ranges where salmon a r e abundant d u r i n g summer. These s p e c i f i c areas a r e Johnstone S t r a i t , o f f n o r t h e a s t e r n Vancouver I s l a n d v i s i t e d by n o r t h e r n r e s i d e n t whales, and Haro S t r a i t , south o f Georgia  Strait,  v i s i t e d by southern r e s i d e n t whales. Both areas a r e a l o n g t h e salmon m i g r a t i o n r o u t e s around Vancouver I s l a n d used by salmon r e t u r n i n g t o r i v e r s i n southern B r i t i s h Columbia 1987;  Gould e t a l . 1988; Gould and Stefansson  (Groot and Quinn  1985).  T r a n s i e n t k i l l e r whales, on t h e o t h e r hand, feed p r i m a r i l y on marine mammals, and Bigg e t a l . (1987) observed  that  the seasonal movements o f these whales were much l e s s p r e d i c t a b l e  3 than those observed  i n r e s i d e n t whales.  Observations  from o t h e r p a r t s of the world  suggest  s i m i l a r seasonal s h i f t s i n k i l l e r whale d i s t r i b u t i o n s i n r e l a t i o n to fur  prey. In the I n d i a n Ocean, k i l l e r whales appear a t seal  (Arctocephalus spp.)  and southern elephant  southern  seal  (Mirounga leonina) r o o k e r i e s d u r i n g the b r e e d i n g season (Condy e t al.  1978;  V o i s i n 1972). O f f the coast of Norway and  around  I c e l a n d , k i l l e r whales are s i g h t e d most commonly i n s h o r e d u r i n g the h e r r i n g season al.  (Jonsgard and Lyshoel 1970;  Sigurjonsson et  1988). S i m i l a r l y i n B r i t i s h and I r i s h waters,  s i g h t i n g s of  k i l l e r whales i n s h o r e c o i n c i d e with the i n s h o r e m i g r a t i o n of herring  (Clupea spp.)  and salmon (Salmo spp.)  and w i t h  the  b r e e d i n g c o n c e n t r a t i o n s of grey s e a l s (Halichoerus grypus) 1988).  (Evans  O f f the e a s t c o a s t of Canada, k i l l e r whales appear t o  move n o r t h i n s p r i n g f o l l o w i n g the m i g r a t i o n of r o r q u a l s (Balaenopteridae spp.)  (Sergeant and F i s h e r 1957).  L i t t l e has been done t o q u a n t i t a t i v e l y r e l a t e the movements of k i l l e r whales t o those of t h e i r prey. T h i s has been l a r g e l y due t o l a c k of data. Recent h i s t o r i c a l i n f o r m a t i o n , however, i s a v a i l a b l e on the movements of r e s i d e n t k i l l e r whales and of salmon i n the c o a s t a l waters of B r i t i s h Columbia  and  Washington S t a t e . These data p r o v i d e a unique o p p o r t u n i t y t o q u a n t i t a t i v e l y r e l a t e movement p a t t e r n s t o prey abundance i n a k i l l e r whale p o p u l a t i o n . S i g h t i n g r e c o r d s spanning many years p r o v i d e data on the seasonal occurrence and d i s t r i b u t i o n of each r e s i d e n t k i l l e r whale pod. These data are a v a i l a b l e from many  4 r e s e a r c h e r s and are maintained i n a c e n t r a l database a t the P a c i f i c B i o l o g i c a l S t a t i o n i n Nanaimo, B r i t i s h Columbia  (M. Bigg  p e r s . comm.). Information on the abundance and m i g r a t i o n c h a r a c t e r i s t i c s of salmon are a v a i l a b l e from the  Canadian  Department of F i s h e r i e s and Oceans (L. Hop-Wo p e r s . comm.; W. Luedke p e r s . comm.) and from the l i t e r a t u r e 1967;  Cooke and Groot,  Shepard  i n p r e s s ; Gould e t a l . 1988).  Heimlich-Boran of  (Aro and  (1986) has made a q u a n t i t a t i v e a n a l y s i s  the seasonal occurrence of southern r e s i d e n t k i l l e r whales  over a t h r e e year p e r i o d i n Haro S t r a i t and a d j a c e n t waterways. His  r e s u l t s show t h a t the occurrence of southern r e s i d e n t whales  c o r r e l a t e s p o s i t i v e l y w i t h the abundance of salmon i n the area. Guinet  (1990a) has shown a p o s i t i v e c o r r e l a t i o n between the  occurrence of n o r t h e r n r e s i d e n t k i l l e r whales and the abundance of  salmon i n Johnstone  S t r a i t d u r i n g one summer season.  A q u a n t i t a t i v e i n depth study s i m i l a r t o H e i m l i c h Boran's (1986) has not been made of the n o r t h e r n r e s i d e n t whales. In my  killer  study I examined the seasonal movements of each of  the n o r t h e r n r e s i d e n t k i l l e r whale pods i n two areas of t h e i r range, Johnstone The purpose was  S t r a i t and King I s l a n d over a s i x year p e r i o d . t o examine the h y p o t h e s i s t h a t k i l l e r whales feed  on salmon and move s e a s o n a l l y throughout  t h e i r home ranges t o  areas where salmon are abundant. I c o n s i d e r e d t h r e e p r e d i c t i o n s of  t h i s hypothesis.  1) I f k i l l e r whales f o l l o w m i g r a t i n g salmon, then  5 they w i l l be seen more f r e q u e n t l y i n Johnstone  Strait  d u r i n g summer months when salmon are abundant than d u r i n g any other time of the year. F u r t h e r , t h e i r occurrence i n the S t r a i t w i l l be p o s i t i v e l y r e l a t e d t o numbers of salmon. To examine t h i s p r e d i c t i o n , I used s i g h t i n g s and o t h e r a v a i l a b l e data t o estimate the abundance of k i l l e r whales on a monthly b a s i s throughout  the year. I then r e g r e s s e d the number of  whales present a g a i n s t the number of salmon, on a weekly b a s i s d u r i n g the salmon  season.  2) The occurrence of k i l l e r whales w i l l be  positively  r e l a t e d t o the occurrence of salmon i n o t h e r p a r t s of the n o r t h e r n community range, p a r t i c u l a r l y when salmon are not abundant i n Johnstone  S t r a i t . To examine t h i s  p r e d i c t i o n , I compared the occurrence of n o r t h e r n r e s i d e n t whales w i t h estimates of salmon numbers d u r i n g s p r i n g near King I s l a n d .  3) F o r a g i n g a c t i v i t y of k i l l e r whales i n Johnstone Strait will  i n d i c a t e t h a t they are f e e d i n g p r i m a r i l y  salmon. To examine t h i s p r e d i c t i o n , I observed  on  killer  whale behaviour and recorded where f o r a g i n g o c c u r r e d i n Johnstone  S t r a i t and compared t h i s t o the areas  by commercial salmon  fishermen.  fished  6 Drawing on the r e s u l t s of these p r e d i c t i o n s I then develop the h y p o t h e s i s t h a t w i t h i n the n o r t h e r n r e s i d e n t community,  pods have t h e i r own seasonal home ranges.  7  METHODS 1) Study Animals In  t h e n o r t h e r n r e s i d e n t community t h e r e a r e  approximately 172 k i l l e r whales i n 16 "pods" (Bigg e t a l . Pod: the  1987).  a group o f i n d i v i d u a l s which t r a v e l t o g e t h e r t h e m a j o r i t y o f time (Bigg e t a l .  1990a). Pod membership i s s t a b l e over time.  Pods range i n s i z e from t h r e e t o 23 i n d i v i d u a l s . When pods do s p l i t t e m p o r a r i l y , they do so i n t o groups c a l l e d  "subpods".  Subpod: sub u n i t s o f pods which a l s o have s t a b l e membership. Members o f subpods almost always t r a v e l t o g e t h e r time) (Bigg e t a l .  (> 95% o f t h e  1990a). There a r e one t o t h r e e subpods p e r  pod. The b a s i c s o c i a l u n i t w i t h i n subpods, and hence w i t h i n pods, i s t h e " m a t r i l i n e a l group". M a t r i l i n e a l Group: A mother and her o f f s p r i n g i n c l u d i n g a d u l t males but not a d u l t daughters which have t h e i r own o f f s p r i n g . Daughters w i t h o f f s p r i n g form t h e i r own m a t r i l i n e a l groups w i t h i n the  pod. I n d i v i d u a l s always t r a v e l with members o f t h e i r  m a t r i l i n e a l group  (Bigg e t a l .  1990a).  2) Study Areas Northern r e s i d e n t k i l l e r whales were s t u d i e d i n two coastal  areas, 1) Johnstone S t r a i t , o f f n o r t h e a s t e r n Vancouver  I s l a n d and 2) King I s l a n d , on the mainland approximately 180 km n o r t h o f Johnstone S t r a i t a)  ( F i g . 1).  Johnstone S t r a i t : The study area i s approximately 50 km from  8  130  125  0  130  125  F i g u r e 1. Map o f B r i t i s h Columbia c o a s t l i n e showing ranges o f the n o r t h e r n ( / / / / / ) and southern resident k i l l e r whale communities ( a f t e r Bigg e t a l . 1987), major salmon m i g r a t i o n r o u t e s (^^**^^ ) and t h e two study areas (Boxes).  9 e a s t t o west and the S t r a i t i s 3.5  t o 4.5  km wide ( F i g . 2 ) .  b) King I s l a n d : The study area encompasses Burke, Dean and Labouchere Channels  a l l of which e n c i r c l e King I s l a n d  i n c l u d e s North B e n t i c k Arm  and  t o the mouth of the B e l l a Cbola R i v e r .  T h i s i s a c i r c u i t of approximately 200 km and each channel i s approximately 3.5  t o 4.5  km wide ( F i g . 3).  3) S i g h t i n g Records A s i g h t i n g r e c o r d i s a r e p o r t of a s i g h t i n g of a subpod t o g e t h e r w i t h the date, l o c a t i o n and the i d e n t i t y of the subpod. Bigg  (1982) showed t h a t k i l l e r whales can be  individually  i d e n t i f i e d by the unique shape of t h e i r d o r s a l f i n s and  saddle  patches, and by s c a r s or n i c k s i n these two a r e a s . A l l r e s e a r c h e r s use t h i s method t o i d e n t i f y and r e p o r t the i n d i v i d u a l s or subpods they see. I compiled s i g h t i n g s of k i l l e r whales from r e c o r d s c o l l e c t e d over an 18-year p e r i o d (1972 Johnstone  t o 1989)  mostly i n  S t r a i t but a l s o from other p a r t s of the n o r t h e r n  community range. The m a j o r i t y of these s i g h t i n g s are s t o r e d i n a database  a t the P a c i f i c B i o l o g i c a l S t a t i o n i n Nanaimo. A d d i t i o n a l  s i g h t i n g s were c o l l e c t e d by myself and o t h e r o b s e r v e r s . Combined t h e r e are over 4000 s i g h t i n g r e c o r d s . F u r t h e r r e f e r e n c e s t o t h i s d a t a s e t w i l l be made as " k i l l e r whale s i g h t i n g database" a) Johnstone  Strait  From the KWSD I s e l e c t e d d a i l y r e c o r d s from y e a r s , 1984  (KWSD).  t o 1988,  five  t o compare w i t h salmon abundance. I chose  10  F i g u r e 2.  Map  o f Johnstone S t r a i t study a r e a (  11  12 these y e a r s because t h e r e was d a i l y observer e f f o r t  over  c o n s e c u t i v e weeks d u r i n g t h e summer months o f J u l y , August and September when salmon a r e abundant. During each summer, one t o two  r e s e a r c h boats, two whale-watching boats and o b s e r v e r s a t a  cliff  s t a t i o n overlooking the S t r a i t  ( i n radio contact with the  boats) a l l monitored t h e study area. Not o n l y were s i g h t i n g s o f subpods r e p o r t e d , but days without whales were a l s o r e p o r t e d . In total,  I s e l e c t e d 61 weeks o f c o n s i s t e n t d a i l y r e c o r d s (Table I ) . In a d d i t i o n t o d a i l y summer s i g h t i n g r e c o r d s from  Johnstone  Strait,  I s e l e c t e d r e c o r d s from t h e KWSD f o r t h e non-  summer months between January  1985 and February 1989. I combined  these r e c o r d s w i t h the summer s i g h t i n g s and w i t h a c o u s t i c data (see below) t o d e s c r i b e t h e annual p a t t e r n o f k i l l e r whale occurrence i n Johnstone  S t r a i t . Non-summer s i g h t i n g r e c o r d s were  c o l l e c t e d i n c i d e n t a l l y and they p r o v i d e d no i n d i c a t i o n o f observer e f f o r t because days without observers and days when whales were not seen were not recorded, b) King I s l a n d S i g h t i n g s o f k i l l e r whales near King I s l a n d were c o l l e c t e d by myself and two other r e s e a r c h e r s (D. Bain and B. K r i e t e ) between A p r i l 28 and June 12 1989. In a d d i t i o n t o r e c o r d i n g t h e i d e n t i t y o f subpods seen, we r e c o r d e d days without whales and days without observer e f f o r t . Over t h e 46 days o f t h i s survey, 10 days were l o s t t o bad weather, engine d i f f i c u l t i e s and supply runs.  13  T a b l e I : Weeks o f c o n s e c u t i v e d a i l y observer e f f o r t i n Johnstone S t r a i t used i n a n a l y s i s . Year  F i r s t week  L a s t Week  1984  July 1st week  Sept. 2nd week  11  1985  June 4th week  Sept. 4th week  14  1986  June 4th week  Sept. 4th week  14  1987  July 3rd week  Aug. 4th week  7  1988  June 4th week  Oct. 1st week  15  Total  T o t a l Weeks  61  14 4) A c o u s t i c Records S i g h t i n g r e c o r d s p r o v i d e one source of data t o monitor k i l l e r whale presence  and movements. Another source are a c o u s t i c  r e c o r d i n g s of the v o c a l i z a t i o n s produced Fisher  (1982) determined  by the whales. Ford and  t h a t each r e s i d e n t k i l l e r whale pod  produces a r e p e r t o i r e of e i g h t t o 15 d i s c r e t e c a l l s . Some pods share c a l l s but each has a unique d i a l e c t . Pods can be  identified  by s p e c t r a l a n a l y s i s of taped r e c o r d i n g s of t h e i r underwater sounds and comparing these with i d e n t i f i e d p o d - s p e c i f i c c a l l s . I analysed a c o u s t i c r e c o r d i n g s made d u r i n g non-summer months a t Orca Lab  (a permanent a c o u s t i c m o n i t o r i n g s t a t i o n  on  Hanson Island) and a t Telegraph Cove (on Vancouver I s l a n d ) .  As  w i t h i n c i d e n t a l s i g h t i n g s , m o n i t o r i n g e f f o r t was  not always  known. Orca Lab monitors t h r e e t o f o u r hydrophone i n s t a l l a t i o n s l o c a t e d i n Blackney  Pass and Johnstone  Strait  (Spong and Symonds  1990). At Telegraph Cove, the hydrophone i s l o c a t e d a t the entrance t o the cove and monitors Johnstone  S t r a i t and Weynton  Pass ( J . Ford p e r s . comm.). The r e c o r d i n g s I analysed r e p r e s e n t e d 52 days from summer months from 1986  t o 1989.  In a d d i t i o n I used  c o l l e c t e d and analysed by Guinet  (1986) and J . Ford  from 1985  and  1986  respectively  data (unpublished)  (Table I I ) .  Recordings were analysed u s i n g a Kay DSP  spectrum  a n a l y s e r , model 5500. P o d - s p e c i f i c c a l l s were i d e n t i f i e d comparing the screen d i s p l a y of a c a l l parameters documented by Ford  non-  s t r u c t u r e w i t h the  by call  (1987) and by a u r a l comparison w i t h  15  T a b l e I I : Months from which a c o u s t i c r e c o r d i n g s were analysed and from which p r e v i o u s l y analysed data were used. Year  Months  Monitorincr l o c a t i o n  1985* 1985**  January, A p r i l October November December  T.C. O.L.  1986**  January, February, March, A p r i l , May June  O.L.  1986  March, June  O.L., T.C.  1987  September, October, November, December  O.L.  1988  October, November, December  O.L.  1989  January,  O.L.  October  February  * a c o u s t i c data p r e v i o u s l y analysed ( J . Ford unpubl. d a t a ) . Used with p e r m i s s i o n , (Ford p e r s . comm.) ** a c o u s t i c data p r e v i o u s l y analysed (Guinet 1986). Used with p e r m i s s i o n (Guinet p e r s . comm.) T.C. = Telegraph Cove on Vancouver I s l a n d O.L. = Orca Lab on Hanson I s l a n d  16 p r e v i o u s l y r e c o r d e d and i d e n t i f i e d  examples.  5) Salmon Abundance E s t i m a t e s a) Johnstone  Strait  The Canadian Department o f F i s h e r i e s and Oceans i n Nanaimo (L. Hop-Wo p e r s . comm.; W. Luedke p e r s . comm.) p r o v i d e d e s t i m a t e s o f t h e number o f sockeye  (0. n e r k a ) , p i n k (0.  crorbuscha) and chum (0. keta) salmon p a s s i n g through Johnstone S t r a i t on a weekly b a s i s d u r i n g J u l y , August, September and October from 1984 t o 1988. Each estimate f o r each salmon  species  i n each y e a r i s c a l c u l a t e d from t h r e e p i e c e s o f i n f o r m a t i o n : i ) The t o t a l s i z e o f t h e run t h a t passed through Johnstone S t r a i t . T h i s i s c a l c u l a t e d as t h e c a t c h p l u s t h e escapement. The escapement i s salmon which escape t h e f i s h e r y and a r r i v e a t the mouth o f t h e i r spawning ii)  river.  The m i g r a t i o n p a t t e r n , o r t h e p e r c e n t o f t h e t o t a l  run t h a t passed through t h e S t r a i t d u r i n g each week o f t h e m i g r a t i o n . T h i s i s estimated from average h i s t o r i c a l escapement curves and t h e run r e c o n s t r u c t i o n method (See H i l b o r n and S t a r r 1988) . iii)  The date o f the peak o f the m i g r a t i o n through  Johnstone S t r a i t .  T h i s i s estimated from t e s t f i s h i n g  results.  The date o f t h e peak c a t c h e s t i m a t e s t h e date o f t h e peak o f t h e migration. Chinook  (0. tschawytscha) and coho (0. k i s u t c h )  salmon  a l s o occur i n Johnstone S t r a i t d u r i n g summer months but they a r e much l e s s abundant  than sockeye, pink, and chum and are n o t  17 c o n s i d e r e d commercially  important  i n the area. Consequently the  Canadian Department of F i s h e r i e s and Oceans has no estimate t h e i r numbers or m i g r a t i o n t i m i n g I was b)  of  (P. S t a r r p e r s . comm.), and  unable t o i n c l u d e these salmon i n my  so  analyses,  King I s l a n d The  B e l l a Coola  Canadian Department of F i s h e r i e s and Oceans i n  (S. Hutchings per. comm.) p r o v i d e d c a t c h  and  escapement data on sockeye, pink, chinook and chum, as w e l l as estimates of the p e r i o d s of peak abundance f o r each s p e c i e s i n the area. From the c a t c h and escapement data I estimated  the  t o t a l number of each salmon s p e c i e s i n the study area d u r i n g s p r i n g . U n l i k e Johnstone S t r a i t , t h e r e are no estimates of weekly abundance.  6) E s t i m a t i n g the Abundance of K i l l e r Whales i n Johnstone S t r a i t Throughout The  Year  The d a i l y s i g h t i n g r e c o r d s from summer months and a c o u s t i c data and year r e p r e s e n t e d 1989.  the  i n c i d e n t a l s i g h t i n g s c o v e r i n g the r e s t of the 3 6 months between January 1985  and  February  These data were used t o c a l c u l a t e the average number of  whales p r e s e n t d u r i n g each month of the annual c y c l e , a)  A c o u s t i c Versus V i s u a l Estimates  of Whale Abundance  Estimates of whale abundance d u r i n g non-summer months were d e r i v e d mainly  from a c o u s t i c r e c o r d i n g s whereas summer  estimates were d e r i v e d from s i g h t i n g s . I t was  important,  t h e r e f o r e , t o compare estimates of whale abundance d e r i v e d by  the  18 two methods when c o l l e c t e d s i m u l t a n e o u s l y , t o determine c o u l d be used throughout  i f they  i n t e r c h a n g e a b l y t o estimate whale abundance  the year. I compared the pods i d e n t i f i e d a c o u s t i c a l l y w i t h those  i d e n t i f i e d v i s u a l l y u s i n g a c o u s t i c data a l r e a d y a n a l y s e d  (J.  Ford  unpubl. data) and the corresponding s i g h t i n g s (KWSD) from a t o t a l of  27 days i n J u l y and August of 1980  t o 1983.  The a c o u s t i c  r e c o r d i n g s were made from a boat and were c o l l e c t e d s i m u l t a n e o u s l y w i t h the s i g h t i n g r e c o r d s . A comparison of the pods d e t e c t e d a c o u s t i c a l l y with those d e t e c t e d v i s u a l l y ,  tests  the l i k e l i h o o d t h a t k i l l e r whales v o c a l i z e when p r e s e n t .  The  number of whales estimated by each method, assuming t h a t a l l members of a pod were present, was  then compared i n a simple  r e g r e s s i o n u s i n g a n a l y s i s of v a r i a n c e t o t e s t the s i g n i f i c a n c e of the r e l a t i o n s h i p  (Wilkinson 1988:  475;  Zar 1984:  268).  I used  the  student t - t e s t t o t e s t whether the s l o p e of the r e g r e s s i o n differed b)  from 1.0  (Zar 1984:  271).  E s t i m a t i n g Numbers of Whales V i s u a l data show t h a t pods sometimes s p l i t  which may  i n t o subpods  t r a v e l s e p a r a t e l y f o r up t o a month (Bigg e t a l .  1990a). K i l l e r whale v o c a l i z a t i o n s a l l o w i d e n t i f i c a t i o n of pods but not which of t h e i r subpods are a c t u a l l y p r e s e n t . Gl  and G12  Furthermore,  pods are not y e t d i s t i n g u i s h a b l e a c o u s t i c a l l y . To account  f o r t h i s l i m i t a t i o n of a c o u s t i c data, I  assumed f o r the purposes  of t h i s a n a l y s i s t h a t when a pod  was  i d e n t i f i e d a c o u s t i c a l l y a l l members of the pod were p r e s e n t . In  19 the case of G l and G12  pods, when "G"  c a l l s were i d e n t i f i e d I  assumed both pods were p r e s e n t . For comparative  purposes  in this  a n a l y s i s o n l y , I converted summer s i g h t i n g of subpods t o pods when a t l e a s t one subpod of a pod was on one day,  present. M u l t i p l e s i g h t i n g s  of subpods b e l o n g i n g t o one pod were counted  one s i g h t i n g . The pod present was  as o n l y  then converted t o the t o t a l  number of whales i n t h a t pod because pod s i z e s v a r y g r e a t l y i n the n o r t h e r n r e s i d e n t community. I then c o n s i d e r e d each whale from the pod p r e s e n t on one day as one  11  whale day"  and summed  the number of whale days f o r each month. Each month of the year was  r e p r e s e n t e d by a t l e a s t 2 years of data  of May  f o r which t h e r e was  (with the e x c e p t i o n  o n l y 1 years d a t a ) . I c a l c u l a t e d the  mean number of whale days each month i n the annual c y c l e by a v e r a g i n g r e p l i c a t e months between January  1985  and  February  1989.  7) Regression a)  Johnstone  Analyses Strait  I used o n l y the 61 weeks of d a i l y k i l l e r whale s i g h t i n g r e c o r d s from the summers of 1984  t o 1988  (Table 1). I computed a  r e g r e s s i o n s t a t i s t i c between numbers of whales p r e s e n t  and  numbers of salmon present f o r each of the 16 n o r t h e r n r e s i d e n t pods. I converted each s i g h t i n g of a subpod d i r e c t l y t o the number of whales i n t h a t subpod. T h i s can be done w i t h the assumption  t h a t a l l members of the subpod are p r e s e n t because  members of subpods t r a v e l t o g e t h e r g r e a t e r than 95% of the time  20 (Bigg e t a l . 1990a). Each whale p r e s e n t on one day  represented  one  "whale day".  I then summed the number of whale days each week  for  each of the 16 n o r t h e r n r e s i d e n t pods. Then t r e a t i n g each pod  s e p a r a t e l y , I r e g r e s s e d the number of whale days per week a g a i n s t weekly numbers of each salmon s p e c i e s (sockeye, p i n k and chum) i n a m u l t i p l e r e g r e s s i o n a n a l y s i s . A n a l y s i s of v a r i a n c e was  used t o  t e s t the s i g n i f i c a n c e of each m u l t i p l e r e g r e s s i o n (Wilkinson 1988:  480;  Zar 1984:  335). I present both the c o e f f i c i e n t of  multiple determination correlation coefficient  (R ) and the corresponding m u l t i p l e 2  (R) f o r comparative  purposes  with other  studies, b)  King I s l a n d The co-occurrence  area was  examined q u a l i t a t i v e l y because weekly e s t i m a t e s of  salmon numbers were not  8) B e h a v i o u r a l a)  of k i l l e r whales and salmon i n t h i s  available.  Sampling  Observations Between J u l y 7 and September 1, 1988,  whales i n Johnstone  A subpod was 100 m.  killer  S t r a i t and recorded where they foraged and  the amount of time they spent i n d i f f e r e n t  of  I observed  l o c a t e d and observed  activities. a t a minimum d i s t a n c e  I i n c r e a s e d o b s e r v a t i o n d i s t a n c e s t o a t l e a s t 300  when the whales entered the Robson B i g h t E c o l o g i c a l Reserve because they are v e r y s e n s i t i v e t o d i s t u r b a n c e when rubbing (Briggs 1987). Observation s e s s i o n s ranged  from 3 t o 8 h.  m  21 S e s s i o n s were terminated a f t e r a maximum of 8 h t o a v o i d observer f a t i g u e , w h i l e s h o r t e r s e s s i o n s were terminated by weather and sea c o n d i t i o n s , time of day or movement of the whales out of the study a r e a . The behaviour of each i n d i v i d u a l i n the group observed and recorded a t 15 min scan i n t e r v a l s  was  (Altmann  1974).  The d i r e c t i o n of t r a v e l of the whales and t h e i r p o s i t i o n  relative  t o landmarks and d i s t a n c e from shore were a l s o r e c o r d e d on a d e t a i l e d map I  of the study area. c l a s s i f i e d the behaviour of the whales i n t o one  of  f i v e main b e h a v i o u r a l c a t e g o r i e s , f o r a g i n g , t r a v e l l i n g , socializing,  r e s t i n g and rubbing. These behaviours have been  d e f i n e d by r e c o g n i z a b l e s u r f a c e behaviours, s u r f a c i n g and the degree of group synchrony Jacobsen  1986;  in respiration  (Ford  intervals 1988;  Osborne 1986) .  F o r a g i n g : Whales i n the group are spread out o f t e n as much as s e v e r a l hundred metres along the shore or w i t h i n a few hundred metres of shore. I n d i v i d u a l s swim i n the same g e n e r a l d i r e c t i o n p a r a l l e l t o shore but s u r f a c e asynchronously. B r i e f bouts of e r r a t i c swimming i n d i c a t e p u r s u i t of prey. T r a v e l l i n g : Whales i n the group swim a b r e a s t of each o t h e r and surface  synchronously.  R e s t i n g : As i n t r a v e l l i n g , whales swim a b r e a s t and  individuals  s u r f a c e synchronously. T h e i r h o r i z o n t a l progress i s v e r y  slow,  however, and s u r f a c i n g s are f r e q u e n t l y f o l l o w e d by b r i e f p e r i o d s of s u r f a c e f l o a t i n g d u r i n g which members of the group f l o a t with  t h e i r blowholes Socializing:  exposed.  I n d i v i d u a l s make p h y s i c a l c o n t a c t w h i l e c h a s i n g ,  breaching and r o l l i n g over each o t h e r . Other s u r f a c e behaviours observed i n c l u d e f l u k e s l a p s , p e c t o r a l s l a p s , breaches, p e n i s d i s p l a y s and spyhops. Rubbing:  I n d i v i d u a l s i n the group rub t h e i r bodies on t h e smooth  pebble s u b s t r a t e a t s p e c i f i c beaches i n the Robson B i g h t Ecological  Reserve,  b) A c t i v i t y Budget During each 15 min i n t e r v a l the behaviour o f t h e group was taken as the behaviour e x h i b i t e d by the m a j o r i t y (> 50%) o f the i n d i v i d u a l s i n t h e group  (Ford 1988). In a l l sample s e s s i o n s  t h i s c r i t e r i a was met, which r e f l e c t s the f a c t t h a t whales w i t h i n a subpod t y p i c a l l y engage i n the same behaviour a t t h e same time. To determine the percent o f time whales spent engaged i n each behaviour I c a l c u l a t e d the t o t a l time spent i n each behaviour over a l l s e s s i o n s and d i v i d e d t h i s by t h e t o t a l minutes o f o b s e r v a t i o n over a l l s e s s i o n s .  RESULTS  I begin with a comparison  of a c o u s t i c and  visual  e s t i m a t e s of whale abundance. I then p r e s e n t the p a t t e r n of k i l l e r whale occurrence i n Johnstone S t r a i t throughout the year and i n more d e t a i l the temporal p a t t e r n d u r i n g summer months of both whales and salmon. I then p r e s e n t the temporal p a t t e r n of k i l l e r whale and salmon numbers i n the King I s l a n d study a r e a . From c o n s i d e r i n g a l l whale s i g h t i n g s combined, I next c o n s i d e r whale s i g h t i n g s from each pod. I examine how  much time each  i n the n o r t h e r n r e s i d e n t community spends i n Johnstone  pod  Strait  d u r i n g summer. I then p r e s e n t the r e g r e s s i o n r e s u l t s between the occurrence of whales from each pod and numbers of salmon i n the Strait. Finally,  I d e s c r i b e the behaviour of whales i n both the  Johnstone S t r a i t and King I s l a n d study areas.  1) Occurrence of K i l l e r Whales i n Johnstone S t r a i t Throughout  the  Year A comparison  of a c o u s t i c and v i s u a l e s t i m a t e s of whale  abundance ( F i g . 4) shows t h a t , with s i m i l a r l e v e l s o f e f f o r t the assumption  t h a t a l l members of a pod are p r e s e n t , the  and  two  methods p r o v i d e s i m i l a r estimates of whale numbers ( r =0.78 2  P<0.001, n=27). The a c o u s t i c method, however, under-estimated s l i g h t l y the number of whales,  because  not a l l pods i d e n t i f i e d  v i s u a l l y v o c a l i z e d d u r i n g some r e c o r d i n g s e s s i o n s or they were out of range of the r e c o r d i n g equipment. T h i s i s r e f l e c t e d i n the s l o p e of the r e g r e s s i o n equation which i s s i g n i f i c a n t l y l e s s than  24  100  -i  80 -  "5 CO CD O *-—» CO Z3  o o  60 -  40 -  < 20  0 0  20  40  60  80  100  Visual estimate  F i g u r e 4. A comparison o f the number o f whales i n Johnstone S t r a i t on 27 days d u r i n g J u l y , August and September o f 1980, 81, 82 and 83 estimated by v i s u a l o b s e r v a t i o n and by a c o u s t i c m o n i t o r i n g . r =0.78, P<0.001, n=27 days, s l o p e < l , P<0.05, Y=3.95+0.78X. 2  25 1.0  (slope = 0.78, t - t e s t : P < 0.05, Y = 3.95 + 0.78X).  Nonetheless,  I have combined s i g h t i n g s and a c o u s t i c data  January 1985 t o February  1989.  from  These data show t h a t k i l l e r whales  are most abundant i n Johnstone S t r a i t d u r i n g summer ( J u l y t o October) and a r e l e a s t abundant between December and June ( F i g . 5).  Furthermore, k i l l e r whales a r e not only l e s s frequent i n  Johnstone S t r a i t o u t s i d e o f summer, but o n l y a few pods seem t o v i s i t t h e area  (Table I I I ) .  2) Salmon Abundance and K i l l e r Whale Occurrence i n Johnstone Strait The t i m i n g o f salmon m i g r a t i o n s , e s p e c i a l l y o f p i n k and sockeye, through Johnstone S t r a i t d u r i n g J u l y , August and September c o i n c i d e s w e l l with t h e occurrence (Fig.  o f k i l l e r whales  6 ) . During these months sockeye and p i n k salmon peak i n  abundance between l a t e J u l y and mid August, chum salmon peak i n abundance i n e a r l y October w h i l e k i l l e r whales s i g h t i n g s peak between l a t e J u l y and e a r l y September. T o t a l numbers each summer of  these t h r e e salmon s p e c i e s have v a r i e d from f o u r t o 15 m i l l i o n  (1984  t o 1988)  (salmon estimates p r o v i d e d by t h e Canadian  Department o f F i s h e r i e s and Oceans, L. Hop-Wo p e r s . comm.; W. Luedke p e r s . comm). Interannual v a r i a t i o n i n salmon numbers r e s u l t s because d i f f e r e n t stocks o f each s p e c i e s r e t u r n i n d i f f e r e n t years and stock s i z e s vary. In a s i m i l a r manner, t h e number o f salmon d u r i n g t h e peak o f the m i g r a t i o n v a r i e d . Numbers of  sockeye d u r i n g weeks o f peak abundance ranged from 150,000 t o  26  n= 1500  3  2 2 2 1  3  4  4  4  4  4  3  months  -i  GO >  "a J32 ctf  1000 -  CD  E c c co  500  CD  0  I  M  A  MY  JU  JL  AU  T  T  T  S  0  N  D  Months F i g u r e 5. Mean number of whale days per month e s t i m a t e d from s i g h t i n g s and a c o u s t i c d a t a . Bars r e p r e s e n t means. V e r t i c a l l i n e s r e p r e s e n t standard e r r o r o f the mean, n = number of r e p l i c a t e months (1985 -1989).  27  Table I I I : Pods p r e s e n t i n Johnstone S t r a i t d u r i n g d i f f e r e n t seasons o f the year (1985 - 1989). Pods i d e n t i f i e d from both v i s u a l and a c o u s t i c r e c o r d s . J u l y - October Al A4 A5 BI CI Dl G1/G12* HI 11 12 111 118 131 Rl Wl  November - June Al A4 A5 CI G1/G12 111 131  * G1/G12 = G l and/or G12 because these pods a r e not y e t d i s t i n g u i s h a b l e a c o u s t i c a l l y .  28  F i g u r e 6. Mean number of salmon and whale days per week i n Johnstone S t r a i t d u r i n g J u l y , August, September and October. • numbers of sockeye i n thousands. numbers of p i n k i n thousands, x numbers chum i n t h o u s a n d s . © numbers of k i l l e r whales, n = 5 summers (1984 - 1988).  29 1.4  million  per week between 1984 and 1988. During weeks o f peak  abundance, numbers o f pink ranged from 250,000 t o 2 m i l l i o n per week and numbers o f chum salmon ranged from 280,000 t o 700,000 per  week (Table I V ) .  3)  Salmon Abundance  and K i l l e r Whale Occurrence Near King I s l a n d  Between l a t e - A p r i l nor  and mid-June, n e i t h e r k i l l e r  whales  salmon are abundant i n Johnstone S t r a i t . Near King I s l a n d ,  however, k i l l e r whales from nine n o r t h e r n r e s i d e n t pods, A l , A4, A5, CI, D l , G12,  I I , 12 and R l , which a l l v i s i t Johnstone S t r a i t  d u r i n g the summer, were observed f o r 3 6 days between A p r i l 28 and June 12 1989  ( F i g . 7 ) . At the same time, t h e r e were salmon i n the  King I s l a n d area and the predominant runs were o f sockeye and chinook ( F i g . 8 ) . Chinook salmon were present i n these channels d u r i n g e a r l y A p r i l with the m a j o r i t y r e t u r n i n g t o t h e B e l l a  Coola  R i v e r system. The number of r e t u r n i n g chinook i s estimated t o have been about 3 0,000, with peak numbers i n the channels by midJune (S. Hutchings p e r s . comm.). Sockeye salmon, m i g r a t i n g t o the Bella  Coola R i v e r a t the head of North B e n t i c k Arm and t o the  Kimsquit R i v e r a t the head of Dean Channel appeared i n Burke and Dean Channels i n mid-May, and peaked i n abundance by e a r l y J u l y (S. Hutchings p e r s . comm). The t o t a l number o f r e t u r n i n g sockeye was about 38,000 salmon.  4) Pod Usage o f Johnstone S t r a i t During Summer Although i n g e n e r a l , k i l l e r whales are most abundant i n  Table IV: Numbers o f salmon ( i n thousands) i n Johnstone S t r a i t J u l y t o October, 1984 t o 1988 from the Canadian Department o f F i s h e r i e s and Oceans e s t i m a t e s (L. Hop-Wo pers.comm; W. Luedke pers.comm.). T o t a l numbers o f each s p e c i e s and the peak weekly number o f each species.  Year  TOTAL Sockeye  JULY t o OCTOBER Pink Chum  84  1796  820  1838  636  241  285  85  4398  7739  3667  1387  2045  570  86  3492  1756  738  1119  566  696  87  2379  2804  1924  659  779  298  88  546  2624  3195  155  818  895  Sockeye  PEAK WEEK Pink  Chum  31  100 -i  00  80 -  cd "a  c o  =cd S >  60  CD"  00  o  40 c CD  O i_  CD  Q_  20 -  0  T  1  A5  12  C1  D1  r?  T  R1  A1  A4  G1  IT  Pods  F i g u r e 7.  Frequency of r e s i d e n t pod May and June are arranged  occurrence o f a l l o r p a r t o f each n o r t h e r n seen i n the King I s l a n d study area d u r i n g 1989. n = 36 days o f o b s e r v a t i o n s . Pods from most frequent t o l e a s t f r e q u e n t .  32  n •  6  6  4  6  6  days  150  CO  & 100  TJ  CD  E  50 -  0 May  June Weeks  chinook sockeye  v/////;/////;/~x  F i g u r e 8. Number o f whale days each week i n t h e King I s l a n d study area d u r i n g May and June 1989. n = number o f o b s e r v a t i o n days each week. H o r i z o n t a l b a r s = weeks when chinook and sockeye were p r e s e n t . Arrow = week of peak chinook abundance.  Johnstone  S t r a i t d u r i n g J u l y , August and September ( F i g . 5), o n l y  whales from A l and A5 pods were p r e s e n t i n Johnstone more than 50% of the days d u r i n g these months (1984  Strait  on  t o 1988).  Most o t h e r pods spent c o n s i d e r a b l y l e s s time i n the S t r a i t ( F i g . 9).  Consequently,  peak weekly numbers of whale days d u r i n g summer  r e p r e s e n t s o n l y about 25% of the n o r t h e r n r e s i d e n t p o p u l a t i o n . I f the e n t i r e n o r t h e r n r e s i d e n t community were p r e s e n t t h e r e should have been about 1204  whale days per week (172 whales * 7 days),  whereas the peak number of whale days was  413  or an average  of  277 whale days per week ( F i g . 10).  5) R e g r e s s i o n R e s u l t s Between the Occurrence the Abundance of Salmon i n Johnstone  of K i l l e r Whales and  Strait  When c o n s i d e r e d i n d i v i d u a l l y ,  s i g h t i n g s o f seven of the  16 pods i n the n o r t h e r n r e s i d e n t community were p o s i t i v e l y  and  s i g n i f i c a n t l y a s s o c i a t e d w i t h estimates of one or more! s p e c i e s of salmon. The occurrence of t h r e e of these pods, A l , A5,j and associated positively occurrence of A4, sockeye  with sockeye  CI,  and p i n k salmon, w h i l e the  Dl and HI a s s o c i a t e d p o s i t i v e l y  and G l pod a s s o c i a t e d p o s i t i v e l y  with only  w i t h o n l y chum salmon  (Table V ) . The more time pods spent i n Johnstone  S t r a i t during  J u l y , August and September (data from F i g . 9), the s t r o n g e r the r e g r e s s i o n ( F i g . 11, r =0.83, p<0.001, n=16)  was  w i t h salmon  numbers (data from Table V ) . Of the s i x pods whose occurrence were p o s i t i v e l y  r e l a t e d t o sockeye  and p i n k salmon, a l l were  p r e s e n t on more than 15 % of summer days i n Johnstone  Strait.  The  34  100  -i  80 c  CD 00 CD 00  60  CO  c  40 -  CD O i_ CD  Q_  20 -  0  n n n JZL i i i i \ i i i i—i—i—i—i—r A1 A5 C 1 A4 D 1 H 1 131 B 1 R 1 W1 G 1 2 111 118 G 1 2 11 i  T  Pods  F i g u r e 9.  Frequency of occurrence of a l l o r p a r t o f n o r t h e r n r e s i d e n t pod i n Johnstone S t r a i t August and September, 1984 t o 1988. Bars p e r c e n t of a l l o b s e r v a t i o n days from 1984 (n = 403 d a y s ) .  r  each during July, represents t o 1988  35  n =  4 5 5 5 5 5 5  5 5 5 4 4 4  weeks  300 n  0  i July  i  i  i  i  i  i  Aug  i  i  i Sept  Weeks  F i g u r e 10. Mean number o f whale days p e r week d u r i n g J u l y , August and September. Dots r e p r e s e n t means. V e r t i c a l l i n e s r e p r e s e n t standard e r r o r o f t h e mean, n = number of r e p l i c a t e weeks 1984 - 1988.  36  T a b l e V. M u l t i p l e r e g r e s s i o n r e s u l t s between weekly numbers o f whale days from each northern r e s i d e n t pod and weekly numbers o f three s p e c i e s o f salmon, i n Johnstone S t r a i t d u r i n g J u l y , August and September, 1984 t o 1988 (n=61 weeks). R = the c o e f f i c i e n t o f m u l t i p l e d e t e r m i n a t i o n f o r each pod, R = the m u l t i p l e c o r r e l a t i o n c o e f f i c i e n t , n = t h e number o f weeks o f whale s i g h t i n g s and salmon abundance data used i n each r e g r e s s i o n . Salmon = those s p e c i e s which c o n t r i b u t e d s i g n i f i c a n t l y i n each m u l t i p l e regression. 2  POD Al A4 A5 Bl CI Dl Gl G12 HI 11 12 111 118 131 RI Wl  R  2  0.28** 0. 10* 0.37** 0. 04 0.35** 0. 10* 0. 10* 0. 05 0.17* 0.01 0. 03 0. 06 0. 07 0. 04 0.06 0. 04  R 0.53** 0.32* 0.61** 0.19 0. 59** 0.31* 0.32* 0.22 0.41* 0 . 12 0. 18 0.24 0. 27 0.20 0.25 0.20  ** P < 0.001 * P < 0.01 S = Sockeye, P = Pink, C = Chum  n 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61  Salmon S, P S S, P S, P S  c  S  37  0.4 n , A5 C1, 'C  o c 0.3 "E "ca  A1  "5 •o  a? a.  0.2 H1.  c Q 'o  ^CD  0.1 - G1i  A4 D1  #  #  O  o  0.0  - f  0  20  40  60  80  100  Percent presence  F i g u r e 11. C o r r e l a t i o n between the p e r c e n t time spent i n Johnstone S t r a i t by pods d u r i n g J u l y , August and September and the s t r e n g t h of the r e g r e s s i o n w i t h salmon. r=0.83, p<0.001, n=16. P o i n t s r e p r e s e n t i n g pods w i t h s i g n i f i c a n t , p o s i t i v e r e l a t i o n s h i p s with salmon abundance a r e l a b e l l e d w i t h the p o d ' s name (see Table V ) .  38 whales i n these pods r e p r e s e n t 3 5% o f the n o r t h e r n r e s i d e n t community  (approximately 59 whales). F o r whales which spent  less  than 15% o f summer days i n t h e S t r a i t , t h e occurrence o f o n l y G l pod was p o s i t i v e l y r e l a t e d t o salmon abundance and t h i s was w i t h chum salmon. G l pod r e p r e s e n t s an a d d i t i o n a l 13% o f t h e community (approximately 2 3 whales). Combined,  numbers o f whale days from  these seven pods c o n s t i t u t e d t h e m a j o r i t y o f weekly whale days between 1984 and 1988  (X=87.6%, S.E.M.=1.52, n=59). The  occurrence o f t h e remaining nine pods, BI, G12, I I , 12, 111, 118, Rl  and Wl (approximately 9 3 whales o r 52% o f t h e community) d i d  not r e l a t e s i g n i f i c a n t l y t o salmon abundance and a l l spent  less  than 15% o f summer days i n the S t r a i t .  6) Behaviour  of K i l l e r  Whales  a) Johnstone S t r a i t A t o t a l o f 13 3 h o f o b s e r v a t i o n s were made o f two subpods, A12 and A2, o f t h e A l pod d u r i n g 22 d a i l y s e s s i o n s between J u l y 7 and September  1, 1988. Of a l l t h e n o r t h e r n  r e s i d e n t pods, A l pod whales use Johnstone S t r a i t t h e most d u r i n g summer (see F i g . 9) and tend t o s t a y w i t h i n t h e study area f o r extended p e r i o d s making i t p o s s i b l e t o f o l l o w them f o r 4 t o 8 h sessions. K i l l e r whales foraged along the Vancouver I s l a n d shore from Robson B i g h t t o B l i n k h o r n P o i n t , a d i s t a n c e o f about 13 km. The whales a l s o forage along West C r a c r o f t I s l a n d , Hanson I s l a n d and i n t h e s t r o n g c u r r e n t a t t h e j u n c t i o n o f Blackney  Pass and  39 Johnstone S t r a i t . P u r s u i t o f prey by k i l l e r whales was e v i d e n t by t h e i r b r i e f bouts o f e r r a t i c swimming. Other r e s e a r c h e r s and I made 5 d i r e c t o b s e r v a t i o n s o f salmon being pursued  o r captured by k i l l e r  whales i n these s h o r e l i n e areas: on two o c c a s i o n s I observed A l pod whales c a p t u r i n g salmon; J . Jacobsen  (pers. comm.) observed  A5 whales on two o c c a s i o n s and a CI whale on one o c c a s i o n , c o r n e r salmon i n rock c r e v i c e s along the shore. The p r o p o r t i o n o f time spent i n each behaviour  category  was: f o r a g i n g 38%, t r a v e l l i n g 32%, r e s t i n g 15%, s o c i a l i z i n g 12% and rubbing  3%.  b) King I s l a n d Although  d e t a i l e d b e h a v i o u r a l o b s e r v a t i o n s were not  made i n t h i s area, k i l l e r whales swam mainly along s h o r e l i n e s and f r e q u e n t l y moved long d i s t a n c e s . For example, on e i g h t o c c a s i o n s when k i l l e r whales were t r a c k e d f o r s i x t o 10 h, they  travelled  d i s t a n c e s o f 40 t o 85 km. Furthermore, r e s i g h t i n g o f t h e same whales o c c u r r e d i n a l l p a r t s o f the approximately  200 km long  study area around King I s l a n d , p r o v i d i n g f u r t h e r evidence t h a t the whales were t r a v e l l i n g long d i s t a n c e s on a d a i l y b a s i s . T h i s i s i n s t r i k i n g c o n t r a s t t o t h e i r movements i n Johnstone S t r a i t d u r i n g summer, which are very  localized.  40  DISCUSSION  1. Occurrence  o f K i l l e r Whales and Salmon i n Johnstone  S t r a i t and  Near King I s l a n d D e s p i t e t h e v a r y i n g q u a l i t y o f data used t o d e s c r i b e the occurrence o f k i l l e r whales i n Johnstone  Strait  throughout  the year, t h e seasonal d i s t r i b u t i o n o f k i l l e r whales i s c o n s i s t e n t w i t h t h e impressions o f r e s e a r c h e r s and t o u r o p e r a t o r s who have worked i n Johnstone  S t r a i t over t h e p a s t 18 y e a r s (M.  Bigg p e r s . comm.; B. MacKay p e r s . comm.). The annual i n c r e a s e i n whale occurrence i n t h e S t r a i t d u r i n g t h e salmon season  (July t o  October)  killer  supports t h e h y p o t h e s i s t h a t n o r t h e r n r e s i d e n t  whales s e l e c t t h e i r h a b i t a t s e a s o n a l l y i n response t o t h e temporal a v a i l a b i l i t y salmon. The occurrence i n t h e King I s l a n d study area of t h e same n o r t h e r n r e s i d e n t pods t h a t Johnstone of  visit  S t r a i t d u r i n g summer c o i n c i d e d with l o c a l s p r i n g runs  sockeye and chinook salmon, p r o v i d i n g a d d i t i o n a l support f o r  t h i s h y p o t h e s i s . Southern r e s i d e n t k i l l e r whales appear t o behave s i m i l a r l y , u s i n g t h e i r h a b i t a t s e a s o n a l l y i n response t o salmon (Heimlich-Boran 1986). 2. The R e l a t i o n s h i p Between the Occurrence Salmon i n Johnstone  o f K i l l e r Whales and  S t r a i t During Summer  The p o s i t i v e and s i g n i f i c a n t r e l a t i o n s h i p s between t h e occurrence o f k i l l e r whales and o f salmon  illustrates  s t a t i s t i c a l l y t h a t t h e seasonal occurrence o f k i l l e r whales i n  41 Johnstone  S t r a i t i s e x p l a i n e d i n p a r t by t h e seasonal abundance  of salmon. Although s t a t i s t i c a l l y s i g n i f i c a n t , none o f t h e c o e f f i c i e n t s o f m u l t i p l e d e t e r m i n a t i o n , nor t h e c o r r e s p o n d i n g c o r r e l a t i o n c o e f f i c i e n t s a r e v e r y h i g h . However, comparing t h e c o r r e l a t i o n c o e f f i c i e n t s with those r e p o r t e d by Heimlich-Boran (1986) f o r t h e southern r e s i d e n t community, and by Guinet  (1990a)  f o r t h e n o r t h e r n r e s i d e n t community, my r e s u l t s a r e s i m i l a r t o t h e r e ' s . In c o n s i d e r i n g the v a r i a t i o n unaccounted  f o r i n these  r e l a t i o n s h i p s i t i s important t o r e c o g n i z e t h a t k i l l e r whales a r e p r o b a b l y h i g h l y e f f i c i e n t p r e d a t o r s which can use s i g h t and sonar t o l o c a t e prey and then move with speed and a g i l i t y t o capture them. Consequently unimportant  s m a l l changes i n o v e r a l l salmon numbers may be  t o t h e whales.  Salmon estimates may be another source o f v a r i a t i o n which i s unaccounted  f o r i n the r e g r e s s i o n s because t h e estimated  number o f salmon p e r week i s l i k e l y i n a c c u r a t e t o some degree. T h i s e r r o r i s r e l a t e d t o t h e m i g r a t i o n curves used by t h e Department o f F i s h e r i e s and Oceans t o make weekly e s t i m a t e s o f salmon abundance. The m i g r a t i o n curve f o r each salmon s p e c i e s i s an average d e r i v e d from the m i g r a t i o n curves o f a l l s t o c k s o f a s p e c i e s t h a t passes through Johnstone chum salmon and even-year are comprised  S t r a i t . F o r example, both  pink salmon p a s s i n g through t h e S t r a i t  l a r g e l y o f a mixture o f s t o c k s d e s t i n e d f o r  d i f f e r e n t r i v e r s along t h e south c o a s t o f B r i t i s h Columbia (Aro and Shepard  1967; Gould e t a l . 1988). In d i f f e r e n t y e a r s , t h e  number o f salmon from each s t o c k of a s p e c i e s can v a r y and thus  42 the composite m i g r a t i o n curve f o r a s p e c i e s w i l l be i n a c c u r a t e i n shape and t h e r e f o r e i n i t s v a l u e o f weekly salmon numbers (W. Luedke p e r s . comm.). Unforunately,  t h e amount o f e r r o r from t h i s  source i s unknown (W. Luedke p e r s . comm.). The s p o r t f i s h i n g c a t c h data used by (1986) t o c o r r e l a t e t h e occurrence  Heimlich-Boran  o f southern r e s i d e n t whales  w i t h salmon abundance a r e a l s o l i k e l y t o have p r o v i d e d i n a c c u r a t e estimates o f weekly salmon numbers, because he d i d not used any measure o f f i s h i n g e f f o r t . S i m i l a r l y , Guinet commercial c a t c h data without  (1990a) used  any measure o f f i s h i n g e f f o r t i n  h i s s i n g l e season c o r r e l a t i o n o f northern r e s i d e n t whales. Nonetheless,  d e s p i t e i n a c c u r a c i e s i n each o f our salmon data  s e t s , my r e s u l t s a r e c o n s i s t e n t with t h e i r s , and combined our r e s u l t s i l l u s t r a t e t h a t a seasonal r e l a t i o n s h i p does e x i s t between r e s i d e n t k i l l e r whales and salmon i n c o a s t a l B r i t i s h Columbia and n o r t h e r n Washington. 3) Foraging Behaviour o f Resident K i l l e r  Whales  The o b s e r v a t i o n s o f k i l l e r whales p u r s u i n g and e a t i n g salmon w h i l e i n t h e Johnstone S t r a i t , which I r e p o r t e d , p r o v i d e s evidence,  i n a d d i t i o n t o the regression r e s u l t s , that the  occurrence o f whales and salmon i n Johnstone S t r a i t r e f l e c t s a predator-prey  r e l a t i o n s h i p . S i m i l a r observations of foraging  whales have been made i n t h e southern r e s i d e n t (Heimlich-Boran behaviour,  community  1986). In a d d i t i o n t o o b s e r v a t i o n s o f f o r a g i n g  t h e r e i s evidence  from f i s h s c a l e s c o l l e c t e d on t h e  water near f o r a g i n g r e s i d e n t k i l l e r whales t o i n d i c a t e t h a t 95%  43 of  d e t e c t e d k i l l s are o f salmon (Bigg e t a l . 1990b). My o b s e r v a t i o n s o f k i l l e r whales i n A l pod showed t h a t  they foraged p r i m a r i l y along s h o r e l i n e s and i n areas o f s t r o n g c u r r e n t . Around King I s l a n d , k i l l e r whales were a l s o observed t o swim mainly along the shore. There are a t l e a s t two p o s s i b l e reasons f o r f o r a g i n g i n s h o r e l i n e areas: 1) Areas where salmon t r a v e l c l o s e t o shore may be important t o k i l l e r whales because they are a b l e t o use t h e shore as a b a r r i e r a g a i n s t which t o t r a p salmon (Jacobsen 1986; Ford 1989). Johnstone Channels,  S t r a i t and Burke, Dean and Labouchere  a l l have steep s i d e s which may make them even b e t t e r  areas f o r t r a p p i n g salmon. Underwater o b s e r v a t i o n s o f k i l l e r whales c o r n e r i n g salmon i n rock c r e v i c e s i n Johnstone  Strait  ( J . Jacobsen p e r s . comm.) support t h i s p o t e n t i a l advantage o f steep s h o r e l i n e s . Southern r e s i d e n t k i l l e r whales forage s i g n i f i c a n t l y more i n areas with high r e l i e f topography  subsurface  and shallow r e e f s along salmon m i g r a t o r y r o u t e s  (Heimlich-Boran 1988). These are areas where salmon c o u l d be e a s i l y herded  into higher d e n s i t i e s  (Heimlich-Boran 1988).  K i l l e r whales o f f A r g e n t i n a and o f f t h e C r o z e t I s l a n d s use s h o r e l i n e s as b a r r i e r s when hunting southern sea l i o n s ( O t a r i a f l a v e s c e n ) and southern elephant s e a l s  (Mirouncra  l e o n i n a ) . These whales i n t e n t i o n a l l y beach themselves t h e i r mammalian prey a t the water's  and capture  edge. Hunting success i s  h i g h e r with t h i s technique than i n open water where p i n n i p e d s are f a s t e r and more a g i l e than on l a n d (Lopez and Lopez 1985; Guinet  1990b). The use o f b a r r i e r s t o herd and capture prey has a l s o been d e s c r i b e d i n s t u d i e s o f b o t t l e n o s e d o l p h i n s ( T u r s i o p s truncatus)  (Wursig 1986; I r v i n e e t a l . 1981).  2) Commercial f i s h i n g a c t i v i t y , c a t c h data and u l t r a - s o n i c t a g g i n g o f salmon a l l suggest t h a t t h e types o f areas where k i l l e r whales forage most i n Johnstone salmon d e n s i t i e s 1986;  (Cooke and Groot,  S t r a i t a r e areas o f h i g h  i n p r e s s ; Gould and Hop-Wo  Quinn and t e H a r t 1987). In Johnstone  Strait,  "hotspots"  r e p o r t e d by fishermen and t e s t f i s h i n g l o c a t i o n s used by t h e Department o f F i s h e r i e s and Oceans a r e along t h e Vancouver I s l a n d shore, along t h e Hanson I s l a n d shore, o f f C r a c r o f t P o i n t and i n Blackney Pass  (Cooke and Groot,  i n p r e s s ; Gould and Hop-Wo 1986).  U l t r a - s o n i c t a g g i n g o f salmon r e v e a l s (Quinn and t e H a r t 1987) t h a t m i g r a t i n g salmon encountering headlands, or  entrances t o bays  i n t e r s e c t i o n s o f channels, become t e m p o r a r i l y d i s o r i e n t e d ,  p o s s i b l y because o f c o n f u s i n g c u r r e n t flows r e s u l t i n g from and wind d e f l e c t i o n i n these areas. Consequently, aggregate themselves  tides  salmon tend t o  i n these p l a c e s f o r a time u n t i l they r e o r i e n t and move on. Around King I s l a n d , k i l l e r whales t r a v e l l e d over much  g r e a t e r d i s t a n c e s than when i n Johnstone  S t r a i t d u r i n g summer.  T h i s d i f f e r e n c e i n d a i l y movement between t h e two areas may be i n response t o d e n s i t i e s and d i s p e r s a l o f salmon. Near King I s l a n d , whales may have needed t o cover more area t o l o c a t e salmon than when i n Johnstone (see  S t r a i t where salmon can number i n t h e m i l l i o n s  Table I V ) . S i m i l a r seasonal changes i n t r a v e l d i s t a n c e s have  been r e p o r t e d f o r o t h e r mammals and have been l i n k e d t o food abundance and d i s t r i b u t i o n  ( A f r i c a n w i l d dogs, Frame e t a l .  1979;  baboons, Devore and H a l l 1965). From l a t e f a l l t o s p r i n g , salmon are fewer i n s h o r e than d u r i n g summer, mainly s m a l l numbers of coho  (Aro and Shepard 1967) and chinook (Aro and Shepard 1967;  Healey 1983) salmon and they are more w i d e l y d i s p e r s e d . I suggest t h a t o u t s i d e of summer months, r e s i d e n t k i l l e r whales r e g u l a r l y cover more area and spend l e s s time i n any one area i n response t o t h i s change i n salmon d e n s i t i e s and d i p s e r a l . So f a r , I have i l l u s t r a t e d t h a t 1) the occurrence of n o r t h e r n r e s i d e n t whales i n both Johnstone S t r a i t and King I s l a n d i s s e a s o n a l , 2) weekly numbers of whales and salmon i n Johnstone S t r a i t d u r i n g summer are p o s i t i v e l y r e l a t e d , and 3) o b s e r v a t i o n s of r e s i d e n t k i l l e r whales i n d i c a t e t h a t they do prey on salmon i n Johnstone S t r a i t . Together, these r e s u l t s support the h y p o t h e s i s t h a t k i l l e r whales use t h e i r h a b i t a t s e a s o n a l l y t o take advantage of v a r y i n g a v a i l a b i l i t y of salmon. My study, however,  also  r e v e a l e d t h a t t h e r e are d i f f e r e n c e s i n the frequency o f occurrence of each northern r e s i d e n t pod i n Johnstone S t r a i t , l e a d i n g t o the h y p o t h e s i s t h a t w i t h i n the n o r t h e r n r e s i d e n t community,  each pod has i t s own unique home range and p a t t e r n of  home range use. I w i l l r e f e r t o pods as the s o c i a l  unit  m a i n t a i n i n g home ranges, because my a n a l y s e s were a t the pod l e v e l r a t h e r than the subpod l e v e l , however, the h y p o t h e s i s I w i l l now develop c o u l d apply e q u a l l y w e l l t o subpods.  46 4) Pod Home Ranges My  study has shown t h a t only p a r t of the  northern  r e s i d e n t community v i s i t s Johnstone S t r a i t f r e q u e n t l y d u r i n g summer and t h a t the occurrence  i n Johnstone S t r a i t of l e s s  than  50% of the whales i n the community i s p o s i t i v e l y a s s o c i a t e d w i t h salmon abundance t h e r e . T h i s r a i s e s the q u e s t i o n as t o , why  do  so  many n o r t h e r n r e s i d e n t k i l l e r whales spend so l i t t l e time i n Johnstone S t r a i t d u r i n g summer when n u m e r i c a l l y t h e r e would seem to  be enough salmon between J u l y and October t o feed the  community? I propose t h a t the reason  f o r the r e l a t i v e l y  low  numbers of whales i n Johnstone S t r a i t d u r i n g summer may be t h a t t h e i r presence  entire  i n part  a f f e c t s the a c t u a l a v a i l a b i l i t y of t h e i r  prey. Though salmon are abundant i n Johnstone S t r a i t , they may  be  wary of f o r a g i n g k i l l e r whales and become harder t o c a t c h once k i l l e r whales have been present f o r a time. C e r t a i n l y , s t a t e t h a t salmon, p a r t i c u l a r l y chinook to for  the presence  salmon, respond s t r o n g l y  of k i l l e r whales and can be d i f f i c u l t  some hours a f t e r whales have passed  fishermen  through  to catch  ( J . Ford  unpubl.). T h i s e f f e c t of p r e d a t o r s on t h e i r prey, known as r e s o u r c e d e p r e s s i o n , can be as important  or more important  than  the abundance of prey i n determining the movements and f o r a g i n g d e c i s i o n s of a p r e d a t o r k i l l e r whale pods may  (Charnov e t a l . 1976).  Consequently,  need to d i s t r i b u t e themselves i n such a  as t o a v o i d e x c e s s i v e o v e r l a p i n any one area i f they are t o forage e f f i c i e n t l y . The v a r i o u s c o r o l l a r i e s home range h y p o t h e s i s f o l l o w .  (bold-type) of  my  way  47 A pod's seasonal  home range c o n s i s t s o f a s e v e r a l  f e e d i n g l o c a t i o n s where salmon are abundant d u r i n g t h e same p e r i o d and a pod t r a v e l s  among these a r e a s .  T h i s i s supported by  my o b s e r v a t i o n t h a t even among pods whose occurrence was p o s i t i v e l y a s s o c i a t e d with salmon abundance i n Johnstone most, s t i l l  spent the m a j o r i t y o f summer elsewhere  s t u d i e s o f primates  (Goodall 1977; Oates 1987),  Strait,  (Fig. 9).  In  i t has been  argued t h a t s y s t e m a t i c u t i l i z a t i o n o f t h e home range l e a d s t o more e f f i c i e n t r e s o u r c e e x p l o i t a t i o n  because  animals know the  abundance and d i s t r i b u t i o n o f food w i t h i n t h e i r range. T h i s may a l s o be t r u e f o r k i l l e r whales. H e i m l i c h - B o r a n s 1  (1986) study o f  southern r e s i d e n t whales p r o v i d e s a d d i t i o n a l support f o r t h i s corollary.  He showed t h a t southern r e s i d e n t whales t r a v e l among  areas, and t h a t t h e i r occurrence i n many areas c o r r e l a t e s w i t h salmon abundance. Pod  home ranges o v e r l a p and many f e e d i n g l o c a t i o n s a r e  used s i m u l t a n e o u s l y by more than one pod. T h i s i s  clearly  supported by t h e o b s e r v a t i o n t h a t d i f f e r e n t pods v i s i t e d Johnstone  S t r a i t a t t h e same time and t h a t a number o f pods were  observed t o g e t h e r near King I s l a n d . Although home ranges o v e r l a p s p a t i a l l y t h e r e may be temporal s e p a r a t i o n i n some c a s e s . F o r example, G l pod spent very l i t t l e  time i n Johnstone S t r a i t d u r i n g  summer and y e t t h e i r occurrence was p o s i t i v e l y a s s o c i a t e d w i t h chum salmon which peak i n f a l l . T h i s suggests partitioning  (Schoener 1974)  temporal  o f t h e salmon r e s o u r c e i n some  areas. S i g h t i n g s and a c o u s t i c data from t h e f a l l  suggest t h a t G l  48 and perhaps G12 pods a r e more common d u r i n g t h e f a l l than  during  the summer. T h i s p a t t e r n has been noted by other r e s e a r c h e r s f o r a number o f years Spong p e r s . comm).  (D. Bain p e r s . comm.; J . Ford p e r s . comm.; P. I t i s a l s o p o s s i b l e t h a t G l pod whales p r e f e r  chum salmon. C e r t a i n l y , d i e t a r y d i f f e r e n c e s among groups of mammals which have s i m i l a r food resources i n t h e i r r e s p e c t i v e home ranges have been r e p o r t e d  (chimpanzees, G o o d a l l  1986).  However, because sockeye, pink and chum salmon each have d i f f e r e n t m i g r a t i o n t i m i n g s through Johnstone S t r a i t ,  it is  d i f f i c u l t t o separate d i f f e r e n c e s i n t i m i n g o f use from prey preference. Seasonal f e e d i n g l o c a t i o n s are v i s i t e d a n n u a l l y by the same pods which have developed p r e f e r e n c e s specific  areas.  T h i s i s supported  f o r f e e d i n g i n these  by t h e o b s e r v a t i o n t h a t each  summer i t i s t h e same pods t h a t a r e frequent v i s i t o r s t o Johnstone S t r a i t . T r a d i t i o n a l use o f c e r t a i n areas c o u l d  develop  because o f t h e advantage o f f e e d i n g i n areas where i n d i v i d u a l s of the pod have a c q u i r e d knowledge over many years about l o c a l salmon d i s t r i b u t i o n . Salmon d i s t r i b u t i o n i s a f f e c t e d by c u r r e n t , subsurface in press; al.  topography, temperature and s a l i n i t y  (Cooke and Groot,  ; Madison e t a l . 1972; Quinn and t e H a r t 1987; Stasko e t  1973). Furthermore, d i f f e r e n t s p e c i e s  (Argue 1964) swim a t  d i f f e r e n t depths and d i f f e r e n t stocks o f t h e same s p e c i e s use d i f f e r e n t m i g r a t i o n routes  (Cooke and Groot  whales a r e l o n g - l i v e d animals  i n press). K i l l e r  and the s t a b l e k i n a s s o c i a t i o n s  w i t h i n pods mean t h a t experience  c o u l d be e a s i l y maintained i n  49 the pod and t r a n s f e r r e d between g e n e r a t i o n s . The  advantage of f a m i l i a r i t y  from p a s t experience  seasonal food a v a i l a b i l i t y are e v i d e n t i n home range use groups of mountain g o r i l l a study  of  by  ( G o r i l l a g o r i l l a b e r i n q e i ) . In  one  (Goodall 1977) , g o r i l l a s a n t i c i p a t e d the seasonal growth of  bamboo and t r a v e l l e d t o s p e c i f i c  areas t o d i g f o r the young  shoots b e f o r e they had emerged from the s o i l . (Fossey and Harcourt  In another  1977), o b s e r v a t i o n s suggested  study  younger  g o r i l l a s l e a r n e d from the experience of o l d e r i n d i v i d u a l s i n the group where t o f i n d food and best  i n p a r t i c u l a r , where t o f i n d  the  food. The  summer home ranges of over h a l f of  the  northern  r e s i d e n t community i n c l u d e f e e d i n g areas d i s t a n t from Johnstone S t r a i t . T h i s i s supported occurrence  1) by the o b s e r v a t i o n t h a t pods whose  i n Johnstone S t r a i t was  not s i g n i f i c a n t l y  associated  w i t h salmon abundance were i n f r e q u e n t v i s i t o r s t o the S t r a i t  and  2) by a small number of i n c i d e n t a l summer s i g h t i n g s of n o r t h e r n resident k i l l e r  whales (KWSD) away from Johnstone S t r a i t , most of  which, have been of pods which spend l e s s than 15% of summer days i n Johnstone S t r a i t . These s i g h t i n g s are mainly areas n o r t h of Vancouver I s l a n d and  from c o a s t a l  from the west c o a s t of  Vancouver I s l a n d . 3) salmon are abundant i n many areas Johnstone S t r a i t between J u l y and October.  besides  In p a r t i c u l a r ,  the  salmon which migrate through Johnstone S t r a i t must f i r s t pass through  Queen C h a r l o t t e S t r a i t . T h i s area, l i k e Johnstone S t r a i t ,  i s an important  commercial f i s h i n g  area  (Cooke and Groot, i n  50 p r e s s ) . R i v e r s and Smith I n l e t s , on the mainland n o r t h of Vancouver I s l a n d , are a l s o important sockeye f i s h i n g areas where peak weekly numbers of sockeye d u r i n g mid J u l y can range 150,000 t o 1,000,000 (1984 t o 1988)  (Aro and Shepard  from  1967;  Goruk  and Thomson 1988). Other important f i s h i n g areas f o r sockeye, p i n k and chum salmon e x i s t throughout many c o a s t a l areas northward  from R i v e r s and Smith I n l e t s t o i n c l u d e the Skeena and  Nass R i v e r s near the B r i t i s h Columbia  - A l a s k a border. Commercial  catches i n these c o a s t a l areas are made between l a t e June and the end of August  (Aro and Shepard  1967). On the west c o a s t of  Vancouver I s l a n d , s m a l l runs of salmon are p r e s e n t from June t o October  (Aro and Shepard  1967;  P a c i f i c Region Salmon  Management Plan 1988 V o l . H). I p r e d i c t t h a t r e s i d e n t whales w i l l  Resource killer  be found t o e x p l o i t salmon i n many of these a r e a s . Resident k i l l e r whales pods not o n l y  co-occur i n  c e r t a i n areas and t h e r e f o r e have o v e r l a p p i n g home ranges, but a l s o show n e i t h e r a g g r e s s i o n nor avoidance when e n c o u n t e r i n g o t h e r r e s i d e n t pods. In a survey of primate s o c i e t i e s , Cheney (1987) concluded t h a t , i n g e n e r a l , the more o v e r l a p t h a t among home ranges, the l e s s l i k e l y and i f they d i d occur, i t was  existed  were a g g r e s s i v e encounters,  over a s p e c i f i c food item. In  another survey, M i t a n i and Rodman (1979) r e p o r t e d t h a t ranges too l a r g e t o be p a t r o l l e d d a i l y were undefended. whales,  In r e s i d e n t  killer  the l a c k of e i t h e r a g g r e s s i o n towards o t h e r pods or  avoidance of pods suggests 1) t h a t home ranges are v e r y l a r g e and 2) prey are not i n s h o r t supply, a t l e a s t not d u r i n g the s p r i n g  51 and summer when I observed them. A t h i r d p o s s i b i l i t y , however, i s t h a t t h e i r r e p r o d u c t i v e behaviour may My  i n f l u e n c e t h e i r movements.  o b s e r v a t i o n s of k i l l e r whales i n Johnstone  t h a t when d i f f e r e n t pods encounter  S t r a i t were  each other, they tended  t r a v e l t o g e t h e r i n t e r m i n g l i n g and engaging  in social  without any s i g n s of a g g r e s s i o n . S o c i a l c o n t a c t may  to  activity be  important  among pods f o r breeding o p p o r t u n i t i e s because i n d i v i d u a l s do not d i s p e r s e from t h e i r pod,  and breeding i s b e l i e v e d t o occur  between r a t h e r than w i t h i n pods (M. Bigg p e r s . comm.). For these reasons,  i t would seem t h a t pods need t o seek out o t h e r pods f o r  mating, i f not f o r other s o c i a l requirements. for  T h i s may  account  some of the o v e r l a p among home ranges of r e s i d e n t k i l l e r  whale pods, and p a r t i c u l a r l y f o r the occurrence of i n f r e q u e n t pods i n Johnstone  S t r a i t d u r i n g summer whose presence was  s i g n i f i c a n t l y r e l a t e d t o salmon abundance. Although  not  virtually  nothing i s known about the mating system of k i l l e r whales, i t i s known t h a t c a l v e s are born throughout i n f a l l and w i n t e r  the year, w i t h b i r t h peaks  (Bigg 1982). T h e r e f o r e , because b r e e d i n g  occurs year round, l o c a t i n g p o t e n t i a l mates would be expected i n f l u e n c e pod movements year round.  to  CONCLUSION Northern  r e s i d e n t k i l l e r whales use t h e i r h a b i t a t  s e a s o n a l l y t o take advantage of s e a s o n a l l y abundant salmon upon which they feed. My r e s u l t s have a l s o l e d me t o h y p o t h e s i z e t h a t each n o r t h e r n r e s i d e n t k i l l e r whale pod has i t s own unique home range. Home ranges o v e r l a p and some f e e d i n g areas may be used s i m u l t a n e o u s l y by a number o f pods or c o n s e c u t i v e l y by pods. Pods t r a v e l among t h e i r p r e f e r r e d areas, t o forage, monitor  prey  resources and perhaps t o l o c a t e mates from other pods.  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