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V ariations in G ray W hale F eeding Behaviour in the Presence of W hale-W atching Vessels in Q a y o q u o t Sound, 1993 - 1995
by Joanna Bass
B.Sc., U niversity of Portsm outh, 1984 M.Sc., U niversity of A kron, 1987
A D issertation S u b m itted in Partial F u lfillm en t of the R equirem ents for the D egree of
DOCTOR OF PHILOSOPHY in the D e p artm en t of G eo g rap h y W e accep t this dissertation as c o n fo rm in g
to the req u ired sta n d a rd
Dr. D. A. DuffuC S ;u p e ^ iso rjD e p a rtm e rtt ^ G eography)
Dr. P. D e a r d e ^ DepwrrWtental ^ le m b e r (D epartm ent o f G eo g rap h y )
Dr. Cl P. K e lle r,^ e p a rtm e n ta i M e m b e r^ ^ P ^ a ftm e n t of G eo g rap h y )
Dr. C. W. Havvryshyn, ô u ts id e M em ber (D epartm ent of Biology)
D r . ^ L . Sum ich, External E xam iner (D epartm ent of Biology, G rossm ont College)
© Joanna Bass, 2000 U n iv ersity of Victoria
All rig h ts reserved. This d isse rtatio n m ay not be re p ro d u c e d in w hole o r in p a rt w ith o u t perm ission of the au th o r.
S upervisor: Dr. D avid A. D uffus
ABSTRACT
The grow ing in d u stry of w hale-w atching is a llo w in g increasing n u m b e rs of p eo p le access to w hales in th eir n atu ral en v iro n m en t, a n d constitutes a n o n c o n su m p tiv e use of the w h ales co m pared to w haling. A t th e sam e tim e,
q u estio n s are often raised a b o u t the h id d en effects o f w hale-w atching o n the w hales. A p o p u latio n of g ray w hales {Eschrichtiiis robushis) w h ich sp e n d s th e su m m e r feeding in C lay o q u o t S ound, on the W est C o ast o f V ancouver Island, is reg u la rly o bserved by w h ale-w atch ers from the n earb y to u rist centre o f Tofino. C o n cern a m o n g w hale-w atching business o p erato rs a n d to u rists a b o u t the possible effects of w h ale-w atch in g o n the feeding w h ales w as h eightened in th e y ears p reced in g this stu d y by a n a p p a re n t n o rth w a rd m o v em en t of the w hales, tak in g th em farther from the Tofino, the p o in t of d e p a rtu re for w h ale-w atch in g tours. This stu d y attem p ts to explain this a p p a re n t tre n d by fin d in g o u t w h e th e r the w hales' short-term b eh av io u r is affected by the p resence of w h ale-w atch in g vessels, a n d by exam ining th eir sh o rt an d long-term b e h av io u r in the w id e r co n tex t o f som e of the features of th eir environm ent.
W hales w ere o b serv ed from a small research vessel fo r three feeding seasons, in five locations w ith in the area kno w n as C lay o q u o t Sound. The w h ales' ventilations w ere rec o rd ed continuously a n d th eir location a n d the
num ber of whale-watching vessels present was recorded at regular intervals. The whales' benthic prey was sam pled in all three seasons and their planktonic prey in 1995. A series of variables were calculated from the ventilation data and compared to the num ber of vessels.
The whales' dive behaviour was correlated much more strongly with feeding location than with vessel number. Even with these two factors taken into account, much of the variation in their behaviour remains unaccounted-for. Because of this, although the behavioural change in the presence of vessels is statistically signihcant, there is reason to doubt whether it is biologically significant. The effects of feeding location are probably a composite of the effects of depth, prey type and other factors which are difficult to measure. Of the two main components, prey type appears to have a greater effect than depth on gray whale behaviour.
Interaction exists between the effects of site and those of whale-watch vessels, m eaning that the effects of vessels are different at different sites. The general pattern is that the effects of vessel presence are more pronounced in shallow sites than in deep, although there are some exceptions to this trend.
Gray whale prey shows considerable variation in location, density and
composition from year to year. The long-term patterns of gray whale habitat use more closely resemble a prey-selection-driven pattern than a pattern of avoidance of whale- watch vessels.
T he relatively sm all influence of vessel n u m b e rs on gray w h ale feeding behaviour suggests th a t th e c u rre n t g u id elin es in place for w h ale-w atch in g vessels are effective in lim itin g distu rb an ce o f th e w hales. The variab le n a tu re of their prey su p p ly su g g ests th a t gray w hales u se all the sites in Q a y o q u o t S ou n d , an d th at the av ailab ility o f a d iverse selection o f p rey is necessary for th eir
success in the tertiary fee d in g g rounds.
E x am in er^
Dr. D. A. D ^ffu s,/S iip erv |so y ( ^ p a r t m e n t of G eo g rap h y )
îij^ - ^ p a r tm e n ta l M em ber (D e p artm en t of G eography)
Dr. C P. Keller, D e p artm en tal M em ber (D e p a rtm e n t of G eographv)
Dr. C. W. H aw ry sh y n , Oilréside M em ber (D e p a rtm e n t o f Biology)
TABLE OF CONTENTS
Table of C o n ten ts ...v
List of Tables ..viii
List of F igures ....ix
A ckn o w led g em en ts ...xii
C h a p te r 1: In tro d u ctio n ...1
1.1 B ackground...1
1.2 R esearch D esign... ...6
1.2.1 Vessel N um bers a n d D iving Behaviour... ...7
1.2.2 E nvironm ental Factors A ffecting Fine-scale S patio-tem poral V ariations in G ray W hale B ehaviour...8
1.2.3 L ong-term Spatial an d T em poral Shifts in G ray W hale A ctivity . ...11
1.3 S u m m ary ...1 4 C h a p te r 2: L iteratu re Survey ...18
2.1 G ray W hale D istribution, Life H isto ry an d Feeding Ecology ...18
2.2 Biology of C om m on Prey Species ...1 9 2.3 W h ale-H u m an Interactions ... 26
2.4 T heoretical A pproaches to F oraging Behaviour ... 31
2.5 A pplication of Foraging Theory to G ray W hale Behaviour ... 38
C h a p te r 3: V essel N u m b ers and D iving B ehaviour ... 41
3.1 Vessel N u m b ers and D iving B ehaviour: Data Collection ....41
3.2 Vessel N u m b ers and D iving Behaviour: D ata Analysis ... 44
3.3 Vessel N u m b ers and D iving B ehaviour: Results ... 46
3.3.1 Dive Param eters a n d Vessel N um bers ... 47
3.3.1.1 V ariation o f Dive V ariables w ith Vessel Presence/A bsence ....47
3.3.1.2 Variation of D ive P aram eters w ith N u m b e r o f Vessels (grouped) ....49
3.3.1.3 Variation o f Dive Vciriables w ith N u m b er o f Vessels ...4 9 3.3.2 The Effect of Feeding Site o n Dive Param eters ....50
3.3.3 Interaction Between Vessel Factors and Site Factors ... 51
3.4 Vessel N u m b ers and D iving Behaviour: Discussion of R esults ... 53
3.4.1.1 V ariation of Dive V ariables w ith Vessel
P re se n c e / A bsence ....54
3.4.1.2 V ariation of Dive P a ram e te rs w ith N u m b e r o f V essels
(g ro u p ed ) ....55
3.4.1.3 V ariation of Dive V ariables w ith N u m b er o f V essels ...56 3.4.2 The Effect of Feeding Site o n D ive Param eters ... 57 3.4.3 Interaction b etw een Vessel F actors a n d Site Factors ....57 C h a p te r 4: Fine-Scale P attern s of W hale A ctivity a n d E nvironm ental F actors ....60
4.1 Fine-Scale P attern s: D ata C ollection ... 60
4.1.1 B ehavioural V ariation b e tw ee n F eed in g Sites ... 61
4.1.2 Prey D istrib u tio n ... 61
4.1.2.1 Benthic Prey ... 61
4.1.2.2 Planktonic Prey ... 65
4.2 Fine-Scale P atterns: D ata A nalysis .. .67
4.2.1 B ehavioural V ariation b e tw ee n F eed in g Sites .. .67
4.2.2 P re y D istribution ... 68
4.2.2.1 Benthic Prey ... 68
4.2.2.2 Planktonic P rey ....68
4.2.3 Evidence of Possible Search B eh av io u r ... 69
4.3 Fine-scale P atterns: R esults ... 69
4.3.1 B ehavioural V ariation b e tw ee n F eed in g Sites ... 70
4.3.2 Prey D istrib u tio n ....74
4.3.2.1 B enthic Prey . ..74
4.3.2.2 Planktonic Prey ....83
4.3.3 Evidence o f Possible Search B eh av io u r ....85 4.3.4 Fine-scale Patterns: S u m m ary o f R esults ....93 4.4 Fine-scale P atterns: D iscussion of R esults ... 94 4.4.1 B ehavioural V ariation b e tw ee n F eed in g Sites ... 95
4.4.1.1 D ive P aram eters ... 96
4.4.1.1.1 Sinuosity R atio ... 97
4.4.1.1.2 Feeding D ive D u ra tio n ...97 4.4.1.1.3 Surface In terv al D u ratio n ... 99
4.4.1.1.4 Dive Cycle D u ra tio n .100
4.4.1.1.5 N u m b er o f V en tilatio n s .101
4.4.1.1.6 V entilation R ate .101
4.4.1.2 C haracteristics of In d iv id u a l Feeding Sites .104
4.4.1.2.1 A hous Bay .104
4.4.1.2.2 C ow Bay .105
4.4.1.2.3 Rafael P o in t .105
4.4.1.2.4 Siw ash P o in t .106
4.4.2.1 Benthic Prey .109
4 4.2.2 Planktonic Prey ..112
4.4.3 E v id en ce o f Possible Search B ehaviour .114 4.4.4 S u m m ary : Fine-scale D ecision-m aking by F o rag in g G ra y
W hales .115
C h a p te r 5: L ong-term Spatial Patterns o f W hale A ctivity in C la y o q u o t S o u n d .1 1 8 5.1 L ong-term S patial P atterns of W hale A ctivity: Data C ollection .119 5.2 L ong-term S patial P atterns o f W hale A ctivity - D ata A nalysis .119 5.3 L ong-term S p atial P atterns of W hale A ctivity - R esults ..123 5.4 L ong-term S patial Patterns of W hale A ctivity: D iscussion of R esults
.131 5.4.1 F actors Influencing Seasonal Site Selection .131 5.4.2 T h e Effect o f D epth o n W ith in -seaso n Spatial A ctivity .1 3 2 5.4.3 T he D ynam ics of L ong-term S patial Shifts .133
C h a p te r 6: C o n clu sio n s .135
L iteratu re C ited .144
A p p en d ix 1: H o u rs o f research effort for each site a n d y ear of th e s tu d y . .154
A ppendix 2: A vailability of D ata .154
LIST OF TABLES
Table 1: D escriptive Statistics for Gray W hale V entilation Data in Q a y o q u o t
Sound, 1993 -1 9 9 5 ' ...48
Table 2: Percentage difference betw een m eans fo r g ray w hale v en tilatio n p attern s in the presence o f d ifferen t num bers of vessels, 1993 -1995 ...48 Table 3: F-ratios for 2-w ay ANOVA c o m p arin g correlations b etw een w h ale
behaviour, site a n d vessel p resen ce/ab sen ce, 1993 -1 9 9 5 ...51 Table 4: F-ratios for 2-w ay AN OVA c o m p arin g correlations b etw een w h a le
behaviour, site a n d vessel num ber, 1993 - 1995 ...51 Table 5: t-values a n d D ifferences Between M eans o f Vessel Presence-absence
C lasses for th e F o u r G ray W hale F oraging Sites in C layoquot S ound;
Pooled D ata fo r 1993 th ro u g h 1995 ...52
Table 6: D escriptive statistics (Means, w ith s ta n d a rd deviations in p aren th eses) for gray w hale d iv e variables at 4 feeding sites in C lay o q u o t S o u n d , 1993 -
1995. ...70
Table 7: M ean N u m b e rs a n d Biomass of Benthic Invertebrates S am pled a t a G ray W hale F eeding Site, A hous Bay, C lay o q u o t S ou n d , 1995 ...74 Table 8: M ean N u m b e rs a n d Biomass of Benthic In v erteb rates R e-sam pled a t a
G ray W hale F eed in g Site (Ahous Bay, Q a y o q u o t Sound) d u rin g th e
S u m m er of 1995 ...75
Table 9: M ean N u m b e rs a n d Biomass of Benthic Invertebrates S am pled a t a G ray W hale F eeding Site, C o w Bay, C lay o q u o t S ound; 1993 -1 9 9 5 ...79 Table 10: M ean N u m b e rs a n d Biomass o f P lanktonic Invertebrates S am p led a t
the G ray W hale F eed in g Sites Rafael Point, Siw ash Point, C o w Bay, A hous Bay a n d H e sq u ia h t d u rin g the S um m er o f 1995 ...84 Table 11: Locations, d a te s, a n d contents of dense p o rcellanid patches
e n co u n tered d u rin g p lan k to n sam p lin g in Q a y o q u o t Sound, B.C., July
a n d A u g u st 1995 ...86
Table 12: A verage D ensity a n d Biomass of B enthic O rg an ism s Sam p led in C ow
LIST OF FIGURES
Figure 1: L ocation M ap o f C layoquot S ou n d , S h o w in g the 5 m ajor G ra y W hale
F oraging A reas ...42
Figure 2: Typical D ive p attern of a Feeding G ray W hale ...45 Figure 3: Frequency o f O bservations of D ifferent N um bers of W hale-w atch
Vessels, C lay o q u o t Sound 1993 -1 9 9 5 ...50
Figure 4: Benthic Sam p lin g Sites in C ow Bay, C lay o q u o t S ound D u rin g th e
S u m m er Seasons o f 1993 -1 9 9 5 ...63
Figure 5: Benthic S am p lin g Sites in A hous Bay, C lay o q u o t Sound, D u rin g July
1995 ...64
Figure 6: L ocation o f P lankton Tows n ear Rafael Point, C layoquot S o u n d , from
June to S eptem ber, 1995 ...66
Figure 7: D u ratio n o f G ray W hale Dive Cycle a t Fo u r Sites in C lay o q u o t S o u n d ,
1993 -1 9 9 5 ...71
Figure 8: D u ratio n o f G ray W hale Feeding D ive a t Four Sites in C lay o q u o t
Sound, 1993 - 1995 ...71
Figure 9; G ray W h ale V entilation Rates a t Five Sites in C layoquot S o u n d , 1993 -
1995 ...72
Figure 10: G ray W hale V entilations per D ive Cycle a t Four Sites in C lay o q u o t
Sound, 1993 - 1995 ...73
Figure 11: G ray W hale Dive Time Percentage a t Five Sites in C lay o q u o t S ou n d ,
1993 -1 9 9 5 ...73
Figure 12: Total N u m b e r of Benthic O rg an ism s p e r Square M eter S am p led a t 17 Sites in A h o u s Bay, C layoquot Sound, D u rin g July 1995 ...76 Figure 13: Total B iom ass o f Benthic O rg an ism s p er Square M eter S am p led a t 17
Bay, C la y o q u o t Sound D u rin g Ju ly 1 ^ 5 ...78 F igure 15: T o tal N u m b ers of Benthic O rg a n ism s per Square M e ter S am p led in
C o w Bay, C layoquot Sound, D u rin g the Sum m er Seasons o f 1993 -1 9 9 5 ...80 F igure 16: T o tal Biomass of Benthic O rg a n ism s p e r S quare M eter S am p led in
C o w Bay, C layoquot S ound, D u rin g the Sum m er S easons o f 1993 -1 9 9 5 ...81 Figure 17: N u m b e rs of Benthic A m p h ip o d s p e r Square M eter S a m p le d in C ow
Bay, C la y o q u o t Sound, D u rin g th e S u m m er Seasons o f 1993 -1 9 9 5 ...82 Figure 18: T o tal N u m b ers of O rg a n ism s O b ta in e d in Each P la n k to n T o w D u rin g
the S u m m e r of 1995 in C la y o q u o t S o u n d , A rranged in A sce n d in g O rd e r ...85 Figure 19: L ocations, Dates an d N u m b e rs o f In d iv id u als in L arge P lan k to n
S am p les C ollected a t Rafael P o in t, C lay o q u o t Sound, D u rin g th e S u m m er
o f 1995 ...87
F igure 20: L ocations, Dates a n d B iom ass o f L arge Plankton S am p les C ollected a t Rafael Point, C layoquot S o u n d , D u rin g the Sum m er of 1995 ...88 F igure 21: S ingle W hale Activity P lo t fo r July 11,1993 in C o w B ay, C lay o q u o t
S o u n d ...89
Figure 22: S ingle W hale Activity P lo t fo r A u g u st 14,1993 in C o w Bay, C lay o q u o t
S o u n d ...90
F igure 23: S ingle W hale Activity P lo t fo r A u g u st 7,1995 a t S iw ash Point,
C la y o q u o t S o u n d ...91
Figure 24: S ingle W hale Activity P lot for A u g u st 12,1995 in C o w Bay, C lay o q u o t
S o u n d ...92
Figure 25: S ingle W hale Activity P lo t for A u g u st 3,1993 in C o w Bay, C lay o q u o t
S o u n d .120
Figure 26: S ingle W hale A ctivity P lo t fo r A u g u st 6,1994 a t R afael Point,
C la y o q u o t S ound ,.121
F igure 27: S ingle W hale A ctivity Plot fo r A u g u s t 31,1995 in C o w Bay, C lay o q u o t
Figure 28: W hale Activity C enters (H arm onic M ean M easure o f A ctivity) for E ach D ay o f M onitoring D u rin g the Sum m er of 1993 in C o w Bay,
C la y o q u o t Sound ..124
Figure 29: W hale Activity C enters (H arm onic M ean M easure o f A ctivity) for E ach D ay o f M onitoring D u rin g the Sum m er of 1995 in C o w Bay,
C la y o q u o t Sound .125
Figure 30: W hale Activity C enters (H arm onic M ean M easure o f A ctivity) for E ach D ay o f M onitoring D u rin g the Sum m er of 1993 a n d th e S u m m er of
1995 in A housBay, C lay o q u o t S o u n d ..126
Figure 31: W hale Activity C enters (H arm o n ic M ean M easure o f A ctivity) for E ach D ay o f M onitoring D u rin g the Sum m er of 1994 off S o u th w e st Flores
Islan d , C lay o q u o t S ound ..127
Figure 32: Spatial Use of C lay o q u o t S o u n d by G ray W hales D u rin g July a n d
A u g u s t 1993 .128
Figure 33: Spatial Use of C lay o q u o t S o u n d by G ray W hales D u rin g July a n d
A u g u st 1994 .129
Figure 34: Spatial Use of C lay o q u o t S o u n d by G ray W hales D u rin g July a n d
A u g u st 1995 .130
Figure 35: T heoretical R epresentation o f Possible Effects of D istu rb an ce o n G ray
A cknow ledgem ents
The success of this research project is th e resu lt of a great d eal of h a rd w o rk an d su p p o rt from a large num ber of people, each of w hom w as a n in v alu ab le
m em ber of th e research team.
Dave Duffus, m y academ ic supervisor, w as fully com m itted, co n sisten tly su p p o rtiv e, inspiring, an d never a t a loss for constructive co m m en ts, relev an t references, sea stories o r rock lyrics. Little d id I realize w h en I b eg an this pro g ram h o w lucky I w as to have lan d e d w ith in his sphere o f influence. M any thanks to m y com m ittee m em bers, Phil Dearden, P eter Keller, C raig H aw ryshyn, a n d T ed Miller, for y o u r h elp a n d patience d u rin g th e d issertatio n process.
Erin G arn ith ers, T revor Davis, C hris M alcolm an d Steve W ischniow ski helped w ith e n o rm o u s a m o u n ts of d ata collection - C hris som ehow m a n a g in g to fit it in aro u n d his o w n research! Steve w as k in d en o u g h to allow th e u se o f h is b o at for d ata collection. Erin deserves a special m en tio n for heroic sto rm d a m a g e rep air u n d er extrem e w eath er conditions.
Cam W ilson, in a d d itio n to being a g o o d -w eath er m agnet, w a s a safe, careful an d cheerful dive p a rtn e r for the u n d e rw ater phase of the benthic d a ta collection. M any thanks to all those w ho helped to set u p an d break d o w n th e research cam ps, especially D arren McKellar w h o h elp ed on num erous occasions. This project w as fu n d ed by grants from th e C enter for Field R esearch
(EarthW atch) a n d the ORES F oundation of Sw itzerland. T heir s u p p o rt is greatly appreciated. T hanks also to the m any v o lu n teers who joined th is project from EarthW atch a n d ORES. They w o rk ed h a rd despite seasickness, b ad w e ath e r and to u g h living conditions, an d this research co u ld not have been accom plished w ith o u t their help.
The w h ale-w atch in g com m unity of Tofino w as consistently su p p o rtiv e of o u r w ork in C lay o q u o t Sound, and I w o u ld like to thank them , b o th for th eir
practical h elp a n d for their interest in th e research. In p articu lar, W ilfred Atleo, Earl Thom as, Rod Palm a n d John Forde w ere generous w ith b o th in fo rm atio n an d cam araderie. S haron Palm 's th o u g h tfu ln ess was m uch a p p re c ia te d d u rin g o u r years a t th e o u td o o r field cam p.
Susan Jones a n d M ike Rothe p ro v id ed friendship, advice, c o m p u te r tim e a n d cups of tea in large quantities, a n d I learn ed a lot from th em b oth.
Fellow m em b ers of the U niversity of V ictoria p ro g ram w h o s u p p lie d m uch- n eed ed frie n d sh ip a n d m oral su p p o rt include Jason D u n h a m , Lisa K adonaga (thanks fo r all th e chocolate a n d cookies!), Laurie Jackson, S a n d ra Peacock, Pam Stacey, H e a th e r Patterson, Ellen H ines, C hristina T om bach a n d S o n y a Meier. These last th re e w ere also sources o f logistical su p p o rt, fro m A cco m m o d atio n to Zip files.
The p eo p le o f th e A h o u sah t Band w elco m ed u s into th eir c o m m u n ity a n d our research p ro g ra m h as benefitted im m ensely from its asso ciatio n w ith th e village an d p eo p le of A h o u sah t. In p articu lar, this association w o u ld n o t h a v e
h a p p e n e d w ith o u t th e practical s u p p o rt of C hief Earl M a q u in n a G eo rg e an d his wife Josephine. Pam Frank of the A h o u sa h t Holistic C en tre w a s in v alu ab le as co o rd in a to r o f th e A h o u sah t y o u th w orkers. S haw n F ran k a n d C aro lin e Joseph, w ho w ere o u r y o u th w o rk ers in 1995, d eserv e a big th a n k -y o u fo r all th eir h ard w ork, b o th o n th e w a te r an d in the laboratory.
Finally, 1 w o u ld like to thank m y p aren ts, N o ra and John Bass, w h o p ro v id ed trem en d o u s s u p p o rt a n d en co u rag em en t th ro u g h o u t the c o u rse of th e stu d y , a n d m y h u sb a n d D ave Pierce, w hose e n e rg y a n d en th u siasm fo r th e p ro ject never flagged, a n d w h o w as never seasick, e v e n in the w o rst w e a th e r.
1.1 B ack g ro u n d
The re c e n t success of w h ale-w atch in g is p a rt of a la rg e r tre n d w h ic h show s w ildlife b eco m in g increasingly im p o rta n t in the to u rist in d u s try (B.C. M in. of T ourism , 1991; H o y t, 1992; H oyt, 1995). T he p o p u larity o f cetacean s in w estern co u n tries is a re c e n t p h en o m en o n (D uffus, 1996). A m o n g th e m o re im p o rta n t resu lts of p u b lic sy m p ath y for these a n im als is the b an o n w h a lin g w h ich exists in m an y c o u n trie s (A ron, 1988) a n d th e b irth a n d d ram atic g ro w th of th e new in d u stry o f w h ale-w atch in g (H oyt, 1992; 1995). In a s tu d y c o n d u c te d in 1986-87, recreatio n al w h ale-w atch ers sh o w ed a h ig h level of e d u ca tio n a b o u t a n d concern for w h ales (D uffus, 1988). O ne co n cern freq u en tly v oiced by th e w h ale-w atch in g public is th a t th e com m ercial w h ale-w atch in g vessels, a n d th e re fo re th ey
them selves as passengers, are d is tu rb in g o r h arrassin g th e w h a le s in som e w ay. Several s tu d ie s s u p p o rt the claim th a t th e w hales are sen sitiv e to b o a t noise (Finley & D avis, 1984, D ahlheim , 1987, B ursk, 1988, M yrberg, 1990) b u t m u ch of the ev id en ce is anecdotal a n d illu strates th e u n certain ty in h e re n t in a tte m p tin g to m easu re th e reactio n s of w hales to ex tern al stim uli. C o rk e ro n (1994) stu d ie d the occurrence o f d ifferen t "b eh av io u ral u n its" in the presence a n d absence o f w hale- w atch in g v essels in Q ueensland, A u stralia, a n d found th a t w h a le -w a tc h in g did affect the w h a le s' behaviour, b u t w as u n a b le to in terp ret th e fin d in g s in term s of possible lo n g -te rm effects on the w hales.
W ith th e g ro w th of w ildlife-based to u rism , the m a n a g e m e n t o f w ildlife is becom ing m o re com plicated (D uffus & D eard en , 1990). In c o m p a riso n to the m ore tra d itio n a l "consum ptive" u se o f w ild life (for exam ple, h u n tin g a n d fishing) the re q u ire m e n ts o f the p atro n s are q u a litativ e (an experience) ra th e r th a n
m ore su b tle th a n sim ple p o p u latio n d ep letio n , a n d th erefo re its m an a g em en t req u ires m o re th a n a population co u n t. The w ildlife m ay be affected in w ays th at are n o t im m ediately obvious, p e rh a p s th ro u g h d am ag e to the s u rro u n d in g habitat, a n d su ch effects m ay also d im in ish the attractiveness o f the reso u rce to tourists.
G iv e n these concerns an d th e ra p id g ro w th of the w h ale-w atch in g in d u stry (H o y t, 1995), w ith co rre sp o n d in g increases in the n u m b e r o f boats in p ro x im ity to th e w hales, it has becom e necessary to d ev elo p reg u la tio n s o r g u id elin es to m an ag e boats w hich a re involved w ith w atch in g w hales.
R egulation co v ers the entire ran g e fro m "Codes o f conduct" a n d g u id elin es to firm legal restrictions. H ow ever, m o st ru les are of a so m e w h a t a rb itra ry n atu re. To be u sefu l, reg u latio n s should be b ased o n the biology a n d b e h av io u r o f the species th e y a re designed to p ro tect (D uffus & D earden, 1992). D etailed stu d ies of th e effects of w hale w atching o n all aspects of the m arin e e n v iro n m e n t a n d especially th e w h ales (and o th er w ildlife) th a t are the focus o f a tte n tio n a re rare, b u t are of g re a t v alu e in fo rm u latin g a p p ro p ria te g uidelines. H o y t (1995)
stresses th e im p o rtan ce of careful research to m onitor the effects of h u m a n
activties o n w hales. A code of c o n d u c t based o n scientific research is m o re likely to be fo llo w ed by w hale-w atch o p erato rs, accepted by the public a n d su p p o rte d by local a u th o ritie s (Duffus & D eard en , 1992) th an a n a rb itra ry code. In
a d d itio n , resea rch th a t provides in fo rm atio n concerning the resu lts o f h u m a n activities w ith in the natural e n v iro n m en t could form a useful p a rt o f a larg er overall s tu d y in a n area of in terest su c h as C lay o q u o t S ound. U n fo rtu n ately , each w h a le-w a tc h in g destination h as d ifferen t characteristics, a n d in m o st locations th e ty p e of detailed in fo rm atio n necessary to fo rm u la te m eaningful g u id elin es is n o t currently available (D uffus & Baird, 1995; D uffus & D earden, 1992).
C la y o q u o t Sound, o n the W est C o ast o f British C olum bia, C an ad a, is a tertiary fee d in g g ro u n d of the gray w hale, Esclirichtius robustus, w h o se prim ary an d se co n d a ry feed in g g ro u n d s are th e Arctic w a ters o f th e Bering a n d C hukchi Seas (Kim & O liver, 1989). G ray w h ales breed in the lag o o n s of Baja C alifornia Sur, M exico, a n d m igrate 8CXX) kilom etres each sp rin g to reach th eir feed in g g ro u n d s. D u rin g the m igration, the w h ales rem ain close to the coast, a n d m any of th em sto p a t tertiary feeding g ro u n d s in British C o lu m b ia, W ashington, O reg o n a n d N o rth e rn C alifornia (N erini & O liver, 1983, O liv er et al. 1984,
G uerrero, 1989), w h ere som e rem ain fo r the en tire su m m er, tak in g a d v a n ta g e of local food sources. V ancouver Island a n d P u g et S o u n d , h o w ev er, a re th e only tertiary feed in g g ro u n d s w here infaunal feeding has b een d o c u m e n te d (Reeves & M itchell, 1988). It has been su g g ested (W eitkam p et al, 1993) th a t these tertiary feeding g ro u n d s a re increasing in im portance as the g ra y w h ale's p o p u latio n recovers fro m w haling-era levels. W hales a re reg u la rly seen d u rin g the su m m er m o n th s off th e W est C oast of V ancouver Island (D arling, 1978; H atler & D arling, 1974; M u riso n et al, 1984). There is e v id en ce th a t g ray w h ales w h ich d o n o t forage in th e p rim ary and secondary feed in g g ro u n d s re tu rn y e ar a fter y ear to the sam e place. It is not k n o w n w h e th e r the w hales th a t fre q u e n t these tertiary feeding g ro u n d s rep resen t a specific u n it of the p o p u latio n , such as n o n -b reed in g w hales, o r w h e th e r they began to forage in areas so u th o f the Bering Sea as a resu lt of o p p o rtu n istic feeding alo n g th e m ig ratio n ro u te o r by follow ing the exam ple o f o th e r w hales.
C lay o q u o t S ound is p articu larly in terestin g a m o n g tertia ry feed in g g ro u n d s d u e to its accessibility to w hale-w atchers. It p ro v id e s a u n iq u e o p p o rtu n ity to stu d y the foraging w hales' reaction to h u m a n d istu rb an ce,
p articu larly w hale-w atching. The m ajority of g ray w h a le w atch in g takes place in the b ree d in g lagoons or along the m ig ratio n routes, a n d C lay o q u o t S o u n d is one of th e few a re a s w h ere foraging w h ales can reliably be o bserved.
4 T he w h a le-w a tc h in g vessels w h ich o p e ra te in C lay o q u o t S o u n d exem plify the p ro b lem s asso ciated w ith a b u rg eo n in g w h ale-w atch in g in d u s try in a n area w h ich h as n o official protection (D uffus & D earden, 1992). T h e m a in attrac tio n is th e sm all p o p u la tio n of gray w hales w h ich feed in the area d u r in g th e su m m er, b u t the a re a is also k n o w n for its o u tsta n d in g n atu ral b e au ty a n d s p o rt fishing. P rim ary lo catio n s a t w h ich g ray w hales feed , a n d are subject to w h ale-w atch in g , include C o w Bay a n d Rafael Point, o n Flores Island, an d A h o u s Bay, o n V argas Islan d (G u errero , 1989, G am er, 1994, D uffus et al., in press). Since 1984, w h e n the first w h a le -w a tc h in g vessel began o p e ra tin g fro m the v illage o f T ofino, th e
w h a le-w a tc h in g in d u stry has increased in size every year. A t th e p re s e n t tim e th ere a re m o re th an 20 vessels offering w h ale-w atch in g trips. M any o f th e o p e ra to rs o f com m ercial w hale-w atch in g vessels show co n ce rn for th e w hales. These o p e ra to rs a tte m p t to self-regulate th ro u g h p eer p re ssu re , b u t th e re are few official a v e n u e s fo r co m p lain t o r enforcem ent. In ad d itio n , s u c h ag re em e n ts are easily je o p a rd iz e d by the refusal of o n e o r tw o op erato rs ("free rid e rs" as
d escrib ed b y O stro m , 1990) to participate.
To p u t re g u la tio n o n a so u n d fo o tin g req u ires a d e e p e r u n d e rs ta n d in g of g ray w h ales' b eh av io u ral ecology th a n h a s p rev io u sly been e m p lo y e d .
U n fo rtu n ate ly , g ray w h ale beh av io u r is difficult to m easure o r an aly ze a n d m ost p rev io u s re se a rc h h a s been descriptive o r an ecd o tal in n a tu re (D arling, 1978, Gill & H all, 1983, O liv er et al, 1983, M oore & L jungblad, 1984, a n d M allonee, 1991). G ray w h ales ex h ib it a n arro w er ran g e o f b eh av io u r d u rin g th e feed in g seaso n th a n th a t fre q u e n tly observed o n th e m ig ra tio n o r a t the c a lv in g lagoons. The m o st rea d ily q u an tifiab le aspects of g ray w h a le behaviour a re th e d iv e variables (dive d u ra tio n a n d surface interval d u ra tio n ) a n d the w h ale's p a th o f m ovem ent. T he w h a les' fo ra g in g b eh av io u r can be se e n as a set of m easu reab le variables w h ich m ay b e influenced by several v ariab les in the fo rag in g a re a , in clu d in g vessel activ ity , d e p th , a n d prey d iv ersity a n d distribution. T h e p u rp o se of this
research project is to u n d e rta k e a q u an titativ e analysis o f g ray w h a le behaviour, in co rp o ratin g aspects of fee d in g ecology, so th at these p a ra m eters can be used as tools w ith w h ich to detect a n y changes w hich m ay occur in th e w h ales'
b eh av io u r in th e presence o f vessels.
T hree ad d itio n al issu es a re ad d ressed in the stu d y . C h a p te r 4 ad d resses the d istrib u tio n o f the w h ales' p re y item s a n d its effect o n th e w h ales' use of space, a n d co m p ares the d iffe re n t feeding locations an d fo rag in g tactics as they relate to the w h ales' en erg y g a in a n d expenditure. C h a p te r 5 exam ines the changes in the w hales' sp a tia l d istrib u tio n across different sp atial a n d tem poral scales. U ltim ately it m ay b e possible to gain inform ation re g a rd in g th e
im portance of vessel traffic, relativ e to o th er factors such as p re y d istrib u tio n , in affecting the w hales' spatial b eh av io u r. It can be arg u e d th a t fo rag in g a n d diving, aspects of b e h av io u r w h ic h are closely linked to energetics, are the activities for w h ich changes in th e factors described above w ill h a v e th e greatest significance.
The s tu d y is d iv id e d in to th ree sections, each of w h ich an aly zes foraging b eh av io u r in a different context, co rresp o n d in g to the issues d escrib ed above. The first section (C hapter 3) co m p ares the m easureable b eh av io u ral p aram eters of the w hales in the presence of v ario u s n u m b ers of vessels. The second
(C hapter 4) exam ines som e o th e r possible causes of v ariatio n in th e w h ales' d iv in g a n d fo rag in g b eh av io u r, p articu larly the w hales' m o v em en ts w ith in the stu d y area as c o m p ared to th e d ifferen t types a n d densities of p re y available to them . The influence of p rey ty p e a n d density o n the g ray w h ale's m o v em en ts is a key p a rt of th e overall p ic tu re o f its behavioural ecology. This section also in terp rets d iv e p aram eters in lig h t o f the connection b etw een o x y g en
co n su m p tio n a n d energy e x p en d itu re , exam ines evidence of possible search b ehaviour, a n d discusses fine-scale decision-m aking by g ray w hales. The th ird
6 p a rt of the s tu d y (C hapter 5) is concerned w ith coarser spatial a n d tim e-scale shifts. C hanges in foraging location are exam ined on a m ed iu m (w ith in seasons) an d coarse (betw een seasons) scale. The dynam ics of long-term sp atial shifts are discussed.
These th ree sections allow fo r the form ation of a co m p reh en siv e p ictu re of g ray w hale fo rag in g ecology, a n d p ro v id e a background ag ain st w h ich the
effects of vessel num bers can be assessed. U ltim ately it is h o p e d th a t the results obtained w ill co n trib u te to the co n stru ctio n of m eaningful g u id elin es fo r th e w hale-w atching industry.
1.2 Research D esign
The p u rp o se of this stu d y is to m easure a n d com pare the b e h av io u r of foraging g ray w hales in the presence a n d absence of w hale-w atching vessels, in response to th e n eed for m ore d e ta ile d stu d ies of the effects of w h ale w atch in g o n m arine m am m als. Gray w hales in the feeding gro u n d s do n o t sh o w d iverse surface b eh av io u rs (Bogoslovskaya, 1986, W ursig et a i, 1986, G u errero , 1989, M allonee, 1991,) so it is n o t possible to d o cu m en t changes in relative rates of certain b eh av io u ral patterns - a com m only u sed indicator of d istu rb an ce
(C orkeron 1994). Physiological m easu rem en ts such as h eart rate (Eisner, 1989) or the blood levels of certain h o rm o n es have been used as a ltern ativ es to
behavioural indicators to identify stress in sm all m arine m am m als. T hese
techniques req u ire the use of invasive m onitoring devices w hich m u st be fitted to the anim al, a n d are n o t suitable for large anim als such as the g ray w hale.
V entilation p attern s, how ever, are quantifiable, accessible, a n d p o ten tially responsive to changes in the w hale s im m ediate environm ent, a n d th erefo re constitute the m ain focus of this stu d y .
In d e cid in g w h a t characteristics of g ray w hale fo rag in g b e h a v io u r to m easure, it is im p o rta n t to co n sid er the constraints placed o n th e ir b e h av io u r by th eir life history. Because th e y h av e only a lim ited tim e in w h ic h to assim ilate sufficient food sto res for th e b reed in g season a n d m igrations, it is reasonable to expect g ray w h ales to a tte m p t to m axim ise th eir n e t en erg y g ain . T he energetics o f d iv in g a n im als involves a trade-off b etw een tim e sp e n t a t th e surface a n d tim e sp e n t a t the b o tto m o r a t fee d in g depth, so th a t the en erg y s p e n t trav ellin g
b etw een th em is m inim ised. It is n o t possible to m easu re g ray w h a le en erg y e x p en d itu re d irectly in the field. Sumich, 1994, sam p led e x p ire d lu n g gas from "frien d ly " g ray w h ale calves in L aguna San Ignacio, b u t this w o u ld be
im practical w ith a d u lt w h ales in th e feeding g ro u n d s. S u b stitu te p aram eters, such as b re a th in g rates a n d d iv e depths, have been u se d to e stim ate the en erg y ex p en d itu re of som e m arin e m am m als (D olphin, 1988).
A n u n d is tu rb e d w h a le 's d iv e characteristics w o u ld be e x p ected to sh o w little v ariatio n o v e r the s h o rt te rm once an "optimal" p a tte rn h a d been
established. A c h an g e in th e w h a le 's dive p a ttern - v en tilatio n rate, d iv e tim e, surface in terv al o r th e relatio n sh ip betw een surface a n d d iv e tim es - co u ld be in te rp reted in term s of ex tern al influence. In ad d itio n , a c h an g e in th e w h a le's tu rn in g b e h av io u r co u ld be sim ilarly interpreted as a spatial influence.
The m ain focus of th is s tu d y is to test the null h y p o th esis th a t g ray w hale surface b eh av io u r is in d e p e n d e n t of vessel num bers. The p rin cip al
m easu rem en ts m a d e in the s tu d y w ere dive variables (feeding d iv e tim e, surface interval tim e, d iv e cycle tim e, n u m b er of ventilations p e r su rfacin g a n d
v en tilatio n rate p e r hour), a n d location a t the en d of each feed in g dive. T he latter enables a n estim ate of "sinuosity " o r path tu rn in g to be m ad e, a n d also m ak es it
8 possible to e stim a te the w ater d e p th in th e location in w h ich th e w h ale w as feeding. T he n u m b e r of vessels p resen t, n o t in clu d in g the resea rch vessel, w as n o ted a t th e e n d o f each feeding dive.
1.2.2 E n v iro n m en ta l Factors A ffecting Fine-scale S p atio -tem p o ral V ariations in G ray W hale B ehaviour
In a d d itio n to observing vessel activ ity a n d the w h a le s' v en tilatio n p attern s, a p re y sa m p lin g p ro g ram w as u n d e rta k e n to a id in in te rp re tin g the v en tilatio n d a ta in term s o f energetics. O v e r the th ree y ears o f th e stu d y , gray w hales w e re o b se rv ed feeding in five d ifferen t areas a n d u n d e r a d iv erse
a sso rtm en t o f e n v iro n m en tal conditions in d e p e n d e n t of vessel n u m b er. In o rd er to place th e w h a le s' d iv in g a n d tu rn in g b eh av io u r in context, a n d to g a in
in fo rm atio n c o n cern in g their search p a tte rn s a n d fo rag in g "choices,"
m easu rem en ts w ere taken to q u an tify factors o th er th a n vessel d istu rb an c e th at w ere ex p ected to affect the w hales' b eh av io u ral p attern s. B ased o n p rev io u s stu d ies (M u riso n et al., 1984, W ursig et al., 1986, D olphin, 1988, G u e rrero , 1989) it w as h y p o th e siz e d th a t variations in fo rag in g d e p th a n d p re y d e n sity w ere likely, singly o r in co m b in atio n , to be co rrelated w ith changes in th e w h a les' beh av io u r patterns. T hese w ere expected to be key factors affecting th e w h a les' foraging strateg y a n d can be seen as an im p o rta n t p a rt of the overall p ictu re o f vessel effects a n d th e w h a les' energy budgets.
T he p ro b lem s in h eren t in the stu d y of cetacean en erg etics, w h ich arise from the resea rch e rs' inability to ob serv e th e ir feed in g b e h a v io u r d irectly an d from the im p o ssib ility of m aking lab o rato ry -ty p e en erg y c o n su m p tio n
m easu rem en ts, can be m itigated so m e w h at by the use of su b s titu te variables as indicators for e n e rg y g ain an d ex p en d itu re. Info rm atio n a b o u t th e so u rces of
energy av ailab le to th e w hales can be o b ta in e d by sam pling th e p re y in areas w h ere th ey feed , p ro v id ed th at so m eth in g of th eir feeding habits is know n.
G ray w h a le s in C layoquot S ound w ere assum ed to be feed in g o n benthic am p h ip o d s, a n d these w ere sam pled in 1993 a n d 1994 in C ow Bay, th e prim ary 1992/1993 fee d in g site, using diver-held cores. In 1993, the p resence of feeding pits (au th o r p ers. obs., 1993) a t the sa m p lin g sites confirm ed th a t benthic feeding w as o ccu rrin g . H ow ever, in 1994, the w h ales d id n o t feed in C o w Bay; instead, a n d u n ex p ected ly , they fed farther w est off Rafael Point, o v er a rocky (au th o r pers. obs., Ju ly 6,1994) substrate. It w as ev en tu ally established, by occasional o p p o rtu n istic sa m p lin g w ith a p lan k to n n e t a n d by feces sa m p lin g w ith a d ip net, th at th e w h a les w ere feeding p rim arily o n sw arm in g Porcellanid larv ae
(C rustacea; A n o m u ra). In response to th is p rey sw itch, a p la n k to n sam p lin g p ro g ram w as in tro d u c ed in 1995 in a d d itio n to continued benthic sa m p lin g w ith diver-held co re s a n d also w ith a b o at-d ep lo y ed core sam pler.
These P orcellanid larvae w ere seen to occur a t a n u m b er o f d e p th s, from right a t the su rface (D. Duffus pers. com m . 1994) to 1 - 2 m off th e seafloor (au th o r pers. obs., July 6,1994); such d iscrep an cy can be expected to in tro d u ce considerable v ariab ility in the w hales' feed in g d ep th . In the case of g ray w hales feeding o n a m p h ip o d s, the dive d e p th is m u ch less variable, since th e p rey only occurs o n the sea floor. H ow ever, a m p h ip o d s can still occur a t a n u m b e r of different w a te r d e p th s, a n d planktonic p rey m ay occur a t an y d e p th o r a t the surface. In a d d itio n , w ith in the local feed in g site, patches of in creased p rey density m ay o c cu r w hich w ould be m o re profitable for the w h ale th a n o th er locations. T his heterogeneity in the food reso u rce should be reflected in the w hale's sp atial p a tte rn s w hich are visible fro m the surface. T here m ay be
energetic trad e o ffs b etw een prey d en sity a n d d e p th or ease of c a p tu re w hich are difficult to q u a n tify . H ow ever, spatial b e h av io u r can provide usefu l clues to the
p rey choices th e w hales are m aking, since by staying at one feed in g site or
m o v in g to a n o th e r, the w hale is selecting a certain com bination o f featu res o f the en v iro n m en t, w h ich include (but are n o t lim ited to) w ater d e p th , p re y ty p e a n d prey density.
Based o n prev io u s studies (G uerrero, 1989, G am er, 1994) a n d o n
theoretical trea tm e n ts of foraging b eh av io u r (Kram er, 1988), c ertain p red ictio n s can be m ad e re g a rd in g the w hales' fo rag in g behaviour u n d e r d ifferen t
co n d itio n s o f p re y availability a n d d e p th . It is im p o rtan t to u n d e rs ta n d these v ariations a n d to in te rp ret gray w hale fo rag in g behaviour in the co n te x t of th eir patchy p re y en v iro n m en t. V entilation rates a n d possibly tu rn in g b e h a v io u r w o u ld be ex p ected to vary betw een p re y ty p es (G uerrero, 1989). All five o f the dive v ariab les c o u ld be expected to v a ry w ith foraging d ep th , a lth o u g h it is difficult to p re d ic t in w h at w ay. Based o n "pre-loading," K ram er (1988) p red icts th a t b o th d iv e tim es a n d surface tim es sh o u ld increase w ith d ive d e p th , b u t th a t surface tim es sh o u ld increase m ore quickly.
The selection o f feeding sites by th e w hales m ay be the re su lt o f the interaction o f m an y factors including d e p th , p rey type, a n d p rey d en sity . W hales c o u ld be expected to select th e p rey type w ith the g rea test d en sity ; how ever, G u e rrero (1989) im plies th a t ex p lo itin g free-sw im m ing p re y m ay req u ire m o re en erg y th an benthic feeding, w hich leads to the p re d ic tio n th a t w hales s h o u ld select benthic o ver p lan k to n ic p rey if benthic p rey w a s available.
W ithin p rey types, w hales can be expected to feed a t the site w ith the g reatest d e n sity of p rey anim als a n d w ith in th a t site, to co n cen trate th eir
foraging a ctiv ity in the "patches" of g rea test p re y density (G uerrero, 1989). Since it req u ires less en erg y to exploit p rey in sh allo w w ater th an in d e e p , w h ales are expected to p referen tially feed in sh allo w w ater, m oving to d e e p e r w a te r later
(G am er, 1994). O n a fine (daily) tem p o ral scale, this w o u ld m ea n sta rtin g th eir search b eh av io u r in sh a llo w w ater a n d m o v in g to deep er w a te r later. It is assu m ed (G am er, 1994) th a t low p a th sin u o sity co rresp o n d s w ith search
b eh av io u r a n d h ig h sin u o sity (increased tu rn in g ) w ith feed in g itself. F o rag in g w hales w o u ld be ex p ected to leave areas o f h ig h prey c o n cen tratio n as th ey becom e d e p le te d (C h a m o v , 1976), b u t p red ic tin g w hen this w ill o c cu r is difficult w ith o u t a c o m p re h en siv e know ledge of th e p rey d istrib u tio n in th e s u rro u n d in g area, a n d of o th e r co n fo u n d in g factors su c h as the relative attrac tiv e n ess of d ifferen t species o f p rey .
1.2.3 L ong-term Spatial a n d T em poral Shifts in G ray W hale A ctivity
A t the b eg iim in g o f this stu d y , o n e o f th e serious concerns facin g the stak eh o ld ers in the w h ale-w atch in g c o m m u n ity of Tofino w as th e a p p a re n t g rad u al n o rth w a rd tre n d in w hale activ ity centers. The co n cem a m o n g w h ale- w atch o p e ra to rs w a s th a t their w h ale-w atch in g activities w ere d riv in g the w hales farth e r fro m Tofino, a n d th a t if th is w as th e case, th en th e ir w h ale- w atch in g in d u stry w as fu n d am en tally un su stain ab le.
A n o th er ex p la n atio n for the w h ales' behaviour, how ever, c o u ld be th a t they are d e p le tin g th e ir food su p p ly in o n e of the feeding sites w ith in the C lay o q u o t S o u n d a re a a n d m oving o n to o th e r sites. In th a t case, th e w h a les' n o rth w a rd m o v em en t co u ld probably be co n sid ered coincidental; th e g ro w th of the w h ale-w atch in g in d u stry coincided w ith the exhaustion of th e so u th e rn m o st site in the area, a n d th e w hales' rem oval to m o re n o rth e m sites w h e re the food su p p ly w as richer.
C h an g es in th e w hales' spatial p a tte rn s c an be expected to o c c u r fro m season to season. If p re y is d ep leted u n d e r feed in g p ressure, th e w h ales' feed in g
12 b eh av io u r sh o u ld fo cu s o n a different location each season, o r e v en fro m one p a rt of a season to th e next. This change in focus can be m easu red u sin g the harm onic m ean m e a su re of activity (Dixon & C h a p m a n , 1980). P rey d e n sity in areas subject to in ten siv e w h ale feeding can b e expected (O liver & S lattery, 1985) to show som e d e p le tio n w h e n com pared to o th e r feeding areas w h ic h hav e n o t been used recently b y th e w hales. A reas of m ax im u m w hale activ ity a re
expected to be c o rre lated w ith areas of m ax im u m p rey density. In th is stu d y , p rey density w as m a p p e d to test the stren g th o f th is correlation.
If w hales re tu rn to th e sam e feeding g ro u n d s y ear after year, a n d
dep letio n of in d iv id u a l sites is indeed occurring, th en a longer-term stu d y m ig h t be expected to rev eal a p a tte rn of rotation b etw een feeding sites as th ey recover. D uring the course o f th is relatively sh o rt (three-year) study, a n a tte m p t w as m ad e to test w h e th e r su ch dep letio n an d ro ta tio n w as occurring, b o th by lo oking a t the prey d istrib u tio n fro m y ear to year a n d b y co m p arin g short, m e d iu m a n d long-term analysis o f th e w hales' d istrib u tio n p attern s. It is h o p e d th a t the inform ation from th is stu d y can be used in conjunction w ith earlier (G am er, 1994) an d later (D u n h am , 1999; Tombach, in p rep aratio n ; M eier, in p rep aratio n ) w o rk to buUd a co m p reh en siv e picture of coarse-scale gray w h ale m o v em en ts w ith in C layoquot S o u n d . T he availability o f a relatively sm all, accessible p o p u latio n (sensu K rebs, 1978) of gray w hales p ro v id es an o p p o rtu n ity ' to gain insights into g ray w h ales' spatial distrib u tio n a n d h ab itat use, som e o f w hich m ay be applicable to g ra y w h ales in the p rim a ry a n d secondary fee d in g g ro u n d s.
As discussed ab o v e, g ray w hales are ex p ected to feed in the a re a s w hich p ro v id e th em w ith th e m ax im u m energy retu rn . Since there is ev id en ce th a t it takes m ore th an o n e seaso n for an a m p h ip o d p o p u la tio n to reco v er fro m extensive g ray w h ale feed in g (O liver & Slattery, 1985), seasonal ro ta tio n of feeding locations is a p ro b ab le long-term o u tco m e of the w hales' search p a ttern s
an d foraging decisions. The fine-scale picture o n ly tells a p a rt o f the sto ry o f gray w hale fo rag in g patterns. It is necessary to exam ine both w h ale a n d p rey distribution p a tte rn s o n a coarser (w ithin a n d b etw een entire feed in g seasons) tem poral scale in o rd e r to place the long-term m ovem ents of the w h ales in the w ider context of th eir o w n spatial m ovem ents a n d the life histories of th e ir prey.
The tem p o ral asp ect o f prey d istrib u tio n is closely tied to th e ab ility of prey to recolonize areas in w hich gray w hales h av e been feeding. F eed in g pits are generally re p o p u la te d follow ing w hale p re d a tio n (N erini & O liver, 1983, W eitkam p et a i, 1992, O liver & Slattery, 1985), a n d w hales sh o u ld resu m e use of depleted areas once the populations have reached fo rm er levels. M easu rem en t of w hale activity a n d p rey density over several y ears can be in te rp re te d in the context of p red a to r-p re y dynam ics a n d sh o u ld enable a long-term tem p o ral dim ension to be a d d e d to the overall picture o f th e w hale's b eh av io u r a n d feeding energetics. P rio r to starting this project, there ap p eared to be so m e tendency to sh o w a shift in feeding location o n a pproxim ately an a n n u a l scale (G am er, 1994), a n d the utilization of alternative form s of prey in each location m ay also form a p a tte rn w hich will becom e a p p a re n t over the long term .
Therefore both betw een-season and w ithin-season scales are im p o rtan t. O p tim al foraging theory d o es n o t specifically ad d ress m ed iu m - o r long-term b eh av io u r patterns, being m o re concerned w ith im m ediate decisions. H o w ev er, a n
extrapolation of op tim ality theory's predictions reg a rd in g search b e h a v io u r a n d consideration of the d o cu m en ted effects gray w h ales have o n th eir feed in g
substrate lead to the pred ictio n that it w o u ld be energetically so u n d for w h ales to find one region w hich is m o st productive for a n y o n e feeding season, a n d exploit th at exclusively.
A ccordingly, it w o u ld be expected th a t all w hales w ithin th e s tu d y area feed at the sam e p rey site in an y given season, th a t the feeding site selected by
14 the m ajority o f in d iv id u a ls will differ fro m th a t selected in th e p rev io u s y e a r o r years, a n d th a t th e re is a recovery p erio d a fte r w h ich w hales re tu rn to a
p rev io u sly a b a n d o n e d site. It is also reaso n ab le to expect th at if w h ales select benthic o v er p lan k to n ic prey o n a daily tim e-scale, the sam e will be tru e o n a seasonal scale, a n d also th a t they will sh o w a g ra d u a l seasonal shift fro m sh allo w to d e ep w a te r a s th e shallow sites becom e ex h au sted .
1.3 S u m m ary
This s tu d y is d esig n ed to exam ine th e d iv in g beh av io u r of g ray w h a le s in relatio n to th e p resen ce o f w hale-w atching vessels a n d in the w id e r co n te x t o f their h e te ro g en e o u s sp atial environm ent. R elev an t literature is rev ie w ed in C h a p te r 2, w ith em p h asis on gray w hale fee d in g ecology, w hale-vessel
interactions a n d fo rag in g theory. C h a p te r 3 describes the p ro ced u res fo llo w ed a n d the d a ta co llected to answ er several specific research questions, w h ile
C h a p te r 4 re c o rd s th e results obtained. C h a p te r 5 presents a p rim ary a n aly sis of the results, a n d d iscu sses each variable w ith reference to the h y p o th eses o u tlin e d in C h a p te r 1. C h a p te r 6 sum m arizes the c o n clu sio n s of the stu d y a n d d iscu sses the m a n a g e m e n t im plications of the fin d in g s, a n d suggestions for fu rth e r
research.
C h a p te rs 3 th ro u g h 5 rep resen t th ree se p a ra te sections of the stu d y :
C h a p te r 3: V essel A ctivity and D iving B eh av io u r. G ray w hale d iv in g b e h a v io u r is sam p led a n d c o m p a re d to the n u m b er o f vessels present. The m e a su re m e n t of dive variables a d d re sse s the stated p u rp o se o f th e study; a q u a n titativ e an aly sis of g ray w h ale b e h a v io u r in o rd er to d etect b eh av io u ral changes w h ich m ay o ccu r in the p resence o f vessels. The dive d a ta is u se d to test the follow ing p a ir of hypotheses:
N u ll H ypothesis: G ra y w h ale ven tilatio n b e h a v io u r is in d ep e n d en t o f vessel n u m b ers
A lternative H y p o th esis: G ray w hale v e n tila tio n b eh av io u r is affected b y vessel n u m b ers
C h ap ter 4: Influence of Prey Tvpe, Prey D en sity a n d o th er E n v iro n m en tal Factors o n Fine-scale S p atio -tem p o ral V ariations in G rav W hale Behaviour. W hale
b eh av io u r is c o m p a re d to feeding site, a n d p re y is su rv ey ed a t each fee d in g site to d e term in e th e ty p e a n d density of th e p re y bein g utilized by th e w h a les feeding a t th e v a rio u s sites o v er the th ree y e a rs of th e study. The w h a le s' p rey selection stra te g y a n d th e influence of p re y ty p e a n d density o n th eir sp a tia l a n d tem p o ral b e h a v io u r is analyzed.
T he collection of p re y d a ta a n d o th er ecological inform ation h elp s to p ro v id e context for th e w h ales' sp atial m ovem ents, in accordance w ith th e s tu d y 's p u rp o se - a q u a n tita tiv e analysis of g ray w h a le b eh av io u r w hich in co rp o ra te s aspects o f th e ir fee d in g ecology. It is im p o rta n t to assess the relativ e ro les of feeding ecology a n d vessel activity in th e in te rp re ta tio n of the d iv e b e h a v io u r m easu red in C h a p te r 3. The follow ing se t o f h y p o th eses are a d d re sse d b y the d a ta rep o rte d in C h a p te r 4:
N u ll H ypothesis: P rey ty p e a n d d en sity a n d w a te r d e p th do n o t in flu en ce g ray w h ale b e h a v io u r
A lternative H y p o th eses:
1. V ariation in g ra y w h ale v entilation ra te a n d tu rn in g b eh av io u r is c o rre la te d w ith p re y ty p e
2. Feeding d iv e tim e a n d surface interval tim e increase w ith increasing d e p th , w ith surface in terv al tim e accounting fo r a n increasing p ercen tag e o f th e w h a le 's tim e
3. W hales select th e p rey ty p e w ith the g rea test d en sity if m ore th a n o n e ty p e is p resen t
4. W hales select benthic o v e r planktonic p re y if bo th are present 5. W hales select th e feeding site w ith the g rea test den sity of prey
6. W ithin sites, w h ales select the patch w ith th e g reatest density of p re y 7. W hales leave p atch es w h e n they becom e d e p le te d
8. W hales search in sh allo w areas first, m o v in g to d eep er w a ter later o n .
C h ap ter 5: L ong-term Spatial a n d T em poral Shifts in G rav W hale B eh av io u r. Location d a ta a n d p re y d a ta collected o v er the th ree years of the s tu d y - su p p lem en ted by re p o rts from local vessel traffic - are a nalyzed for lo n g -te rm patterns. Seasonal m o v em en ts of foraging g ray w h ales are described in a n ecological context.
In o rd er to fulfil th e p u rp o se of the stu d y - th e u se o f gray w hale b e h a v io u r a s a tool w ith w hich to d e te ct biological changes in th e presence of vessels - it is im p o rtan t to u n d e rs ta n d the scale a t w h ich th e g ray w hales' b eh av io u ral processes are o p eratin g . The data p resen ted in C h a p te r 5 exam ine th e issue of scale, a n d a d d re ss th e follow ing pairs of hypotheses:
1. N ull H ypothesis: G ray w hales' feeding activity is random ly d istrib u te d a m o n g possible feed in g sites in C layoquot S o u n d
A lternative H ypothesis: W hales focus o n o n e location p er season, a n d th is location ch an g es fro m one season to th e n ex t
2. N ull H ypothesis: G ray w h ale spatial activity w ith in seasons is in d e p e n d e n t of foraging d e p th
A lternative H ypothesis: W hales show a w ith in -seaso n sh ift from sh allo w w a te r to d eep er w ater
3. N ull H ypothesis: T he selection of a seasonal fo rag in g site by g ray w h a les is in d ep en d en t o f th e sites selected in p rev io u s seasons
A lternative H ypothesis: R otation of feeding sites occurs betw een seasons, correlated w ith p re y d ep letio n
A lternative H ypothesis: W hales follow a d irectional tre n d in th eir feed in g site selection b etw een seasons
In C h ap ter 6, th e conclusions of the stu d y a re su m m arized a n d
recom m endations a re m ad e reg ard in g the w hale w atch in g in d u stry a n d fu tu re research in the area o f gray w hale ecology an d m an ag em en t.
C h a p te r 2: U TER A TU R E SURVEY
This c h a p te r rev ie w s existing in form ation a b o u t the gray w hale, w ith em p h asis o n its fee d in g b eh av io u r and prey, its p o p u latio n an d d istrib u tio n , a n d its interactions w ith h u m an s. Relevant aspects o f th e w hale-w atching in d u stry a re also d iscussed. T he last p a rt of the ch ap ter co v ers foraging th eo ry , o n w h ich this stu d y is based, a n d issues concerning its a p p lic a tio n to m arine m am m al behaviour.
2.1 G ray W hale D istrib u tio n , Life H istory a n d F eed in g Ecology
The g ray w h ale, Eschrichtius rohustus, is th e o n ly species in th e fam ily E schrichtidae (R eeves & M itchell, 1988), its d istin ctiv e skull stru c tu re a n d o th e r characteristics s e ttin g it a p a rt from o ther m ysticete w h ales (Bames & M cLeod, 1984). G ray w h ales a re also u nique in b eing p rim a rily benthic feeders. T hey h av e an im p o rta n t ro le in the recycling of n u trie n ts fro m the ocean floor to th e surface a n d th e so rtin g o f ocean floor sed im en ts (Johnson & N elson, 1984, N elso n et al., 1987), d u e to th e ir ten dency to ascend for v e n tilatio n w ith b o tto m se d im e n t still stream in g fro m th e ir m ouths. Two p o p u la tio n s of g ray w hales exist. T he C alifornian (or E astern Pacific) p o p u latio n ran g es fro m Baja C alifornia to th e C hukchi a n d B eaufort Seas, a n d the K orean (or W estern Pacific) p o p u la tio n m igrates b etw een th e K orea Strait an d the Sea o f O k h o tsk (Reeves & M itchell, 1988). T hese stocks a re th o u g h t to be g eographically separate, a lth o u g h it is sp ecu lated th a t th ere m a y be som e "m igratory bleeding" from the easte rn sto ck in to the w estern , w h ic h m ay no w nu m b er only o n e o r tw o h u n d re d in d iv id u als. T here is ev id en ce th a t th ere w as once a th ird p o p u la tio n of gray w hales in th e A tlantic, b u t th is sto ck is n o w extinct, an d in fo rm atio n concerning its size a n d ran g e is n o t av ailab le (R eeves & Mitchell 1988). T he g ra y w hales of C lay o q u o t S o u n d belo n g to th e m o re n u m ero u s E astern Pacific population.
E astern Pacific G ray w hales m ate in the so u th e rn m o st p a rt o f th e ir range, the b ree d in g lagoons o f Baja California, Mexico. T heir m ating takes place in early w in ter, u su ally a ro u n d December, an d th e fem ales give b irth 13 - 14 m o n th s later (Rice et al., 1981). In the spring, th e w h ales begin to m ove
n o rth w a rd to w a rd th e ir su m m er feeding g ro u n d , the p reg n a n t fem ales leav in g first, in m id -F eb ru ary , follow ed by o th er a d u lt w h ales, an d finally by fem ales w ith n ew b o rn calves. O rig in ally it w as th o u g h t th a t all calves w ere b o m in the w arm w aters of th e b re e d in g lagoons, a n d n e e d e d to build blubber reserv es before trav ellin g to th e c o ld e r n o rth em w aters, b u t th ere is n o w ev id en ce th a t som e a re b o m as far n o rth as W ashington State (Jones & Sw artz, 1984).
Little is k n o w n a b o u t h o w gray w hales n av ig ate d u rin g th eir m ig ratio n . Som e O d o n to cetes a re th o u g h t to navigate by m ean s o f sonar (Lockyer & Brow n, 1981) a n d by reference to earth 's geom agnetic field (Klinowska, 1988).
M ysticetes are n o t th o u g h t to use these m eth o d s o f navigation. Pike (1962) su g g ested th a t g ray w h a les m ay navigate visually, b u t M ass a n d S u p in (1990) p ro v id e evidence th a t th e ir visual acuity is relatively low , m aking v isual n av ig atio n seem unlikely.
T he w h ales a rriv e a t the prim ary feeding g ro u n d s in the Bering a n d C hukchi Seas a b o u t tw o m o n th s later, a n d rem a in th ere until O ctober (Rice et al, 1984). G ray w h ales g ain , o n average, 16 - 30% of th eir b o d y w eig h t in th e five m onths th ey sp e n d a t th e feeding grounds. This is eq u iv alen t to c o n su m in g 400 - 1200 kilo g ram s of food p e r d a y (Nerini, 1984).
2.2 Biology o f C o m m o n Prey Species
U nlike o th e r b aleen w hales, gray w hales a re k n o w n to feed
20 plankton, h av in g shorter, c o arser baleen th an th e o th e r m ysticetes (baleen
w hales), b u t instances of planktonic feeding have b een frequently d o c u m e n te d (Pike, 1962, W ellington & A nderson, 1977, N erini, 1984; Duffus, 1996). T heir d iet has been kno w n to include benthic polychaete w o rm s, g h o st shrim p (Callianassa), sq u id spaw n, h errin g sp aw n , sm all bait fish, d e ca p o d larvae, m ysids a n d
e u p h au sid s (N erini, 1984, W eitkam p et a i, 1992). T he g ray w hale's ability to feed o n planktonic p rey in a d d itio n to benthos gives it a d ietary flexibility u n iq u e am o n g cetaceans. Kim a n d O liver (1988) suggest th at, since gray w hales are m ostly found in coastal env iro n m en ts, this characteristic flexibility m ay h av e arisen as a resu lt of ch an g in g prey availability as sea levels fluctuated o v er the last 30,000 years. T heir ability to feed opportunistically m ay be partly
responsible for the g ray w hales' relatively fast reco v ery from w haling-era p o p u latio n levels (N erini, 1984).
In o rd er to be able to evaluate the gray w h a le s' d iv in g b ehaviour in th e context of its foraging ecology, it is useful to u n d e rs ta n d th e ecological
circum stances in w hich the beh av io u r occurs (D uffus, 1996). These include th e life histories of the v arious p rey anim als available to the w hale, both in g en eral a n d in the Q a y o q u o t S o u n d area specifically. The p rim a ry food source of g ray w hales in the B ering a n d C hukchi Seas appears to be sm all tubicolous
crustaceans {Ampelisca spp.) w hich are p art of the o rd e r A m phipoda (Frost & L ow ry, 1981). The O rd e r A m p h ip o d a is extrem ely w id e sp rea d an d diverse. A m phipods are w ell rep resen ted in freshw ater a n d m arin e habitats a n d th e re are even a sm all n u m b er o f terrestrial species. The O rd e r contains form s as d iv erse as the skeleton sh rim p s (Suborder: C aprellidae) a n d th e so-called "whale lice" (Family: C yam idae). The infaunal tubicolous a m p h ip o d s w hich d o m in ate th e benthic com m unity of the w hales' feeding g ro u n d s belong to the Fam ily A m peliscidae, S u b o rd er G am m aridea; a lth o u g h th e c o rophioid g ro u p also contains tubicolous form s, these a p p ea r to have d e v elo p ed separately from th e
am peliscid tu b e-d w ellers (B arnard & K aram an, 1991). The am p eliscid s a re th e o n ly tube-dw ellers o f th e p rim arily benthic G a m m a rid Suborder. A d u lt
am peliscids c o n stru ct tu b es o f m aterial k n o w n a s "silk" w hich is secreted by g lan d s situ ated o n th e ir p e reio p o d s (thoracic ap p en d ag es). The tu b e-d w e llin g a m p h ip o d s of th e w a te rs a ro u n d V ancouver Islan d are prim arily Ampelisca
agassizi; th eir tu b es a re b u rie d 10 -1 5 cm d e ep in th e san d bottom , w ith a lm o st no p a rt of the tu b e sh o w in g w h e n u n d istu rb ed (O liver et at., 1983), so th a t a fee d in g w h ale w o u ld have to m ak e a n an excavation 15cm d eep in the se d im e n t to
c a p tu re all of the cru stacean s. It is possible to o b serv e these "feed in g p its " in areas w h ere w hales h av e b een feeding (N elson et al., 1987, O liver & S lattery , 1985, W eitkam p et al., 1992). These benthic a m p h ip o d s' p artially -b u ried tu b es form "mats" o n the o cean floor. The m ats are o fte n extrem ely d en se in so m e areas - u p to 24,000 in d iv id u a ls per m^ in the E astern Bering Sea (Stoker, 1981). A m peliscids are cap ab le sw im m ers a n d craw lers, b u t sp en d m ost of th e ir tim e in th eir b u rro w s, since th ey feed u p sid e d o w n in th e tube u sin g their a n te n n a e , w h ich have m an y lo n g h a irs o r setae, as filters w h ile creating a w a ter c u rre n t in th e tu b e (B arnard & K aram an , 1991). This b e h a v io u r pro v id es a relativ ely static p rey o n w hich the w h ales c an "graze," rath e r th a n a m obile p rey w h ich m u s t be p u rsu e d .
G ray w hales feed by sucking o r scooping th e bottom sed im en ts in to th eir m o u th s, a n d th en ejecting th e w ater an d se d im e n t particles. The in v e rte b ra te s w h ich a re taken in w ith th e sedim ents are re ta in e d beh in d the w h ale's b a le e n a n d th e n sw allow ed. This m e th o d of feeding leaves larg e (average 1.6m. lo n g ) o val d ep ressio n s in the seaflo o r w h ich g rad u ally d e g ra d e w ith tim e a n d are
recolonized by a m p h ip o d s (N erini & O liver, 1983, N erini, 1984, O liv er & S lattery , 1985, Klaus, 1990).
22 The b en th ic a m p h ip o d c o m m u n ity in the w aters off th e w e st co ast of V ancouver Islan d h as b een d escrib ed as ecologically an alo g o u s to th e extrem ely p ro d u ctiv e b en th ic a m p h ip o d c o m m u n ity in the Bering Sea, th e w h a les' prim ary an d seco n d ary fee d in g g ro u n d s (O liver et al., 1983). Both are d e tritu s-b a se d trophic sy stem s, d o m in a te d by relativ ely low -diversity assem b lag es o f infaunal benthic filter-feeders. T he Bering Sea flo o r is p o p u lated by assem b lag es
consisting o f "pioneer "-type species o f th e g enus Ampelisca (N erin i 1984). Stoker (1981) d escrib es the assem blages as tem p o rally stable, b u t co m p lex in the
d istrib u tio n a n d sp atial a rra n g e m e n t o f species, w hich seem s c o n tra ry to N erini's (1984) a sse ssm e n t th a t th ey are "n ea rly " m onospecific. In his 5 -y ear s tu d y in w hich 176 s a m p lin g statio n s w ere q u a n titatv ely surveyed. S to k er (1981) fo und 472 species, in c lu d in g 76 am p h ip o d species. H e also fo u n d th e d istrib u tio n of in d iv id u als to b e extrem ely patchy, c a u sin g h im to classify so m e o f his
q u an titativ e re su lts as "m arginally acceptable. " For exam ple, th e d e n sity of o rganism s in th e e a ste rn Bering Sea ra n g e s from 400 p e r m^ to 24,000 p e r m-. M ean benthic b io m ass is calculated as 4 8 2 g / m^, w ith a m p h ip o d s a cco u n tin g for 161g/m 2. H ig h sm ith a n d C oyle (1990) calculated the m ean n u m b e r of
a m p h ip o d s in th e C h irik o v Basin (n o rth e m B ering Sea) as 4 ,6 0 6 /m^, a g a in w ith a high s ta n d a rd d ev ia tio n , an d c o m m en ted o n the extrem ely h ig h caloric content of the C h irik o v a m p h ip o d co m m u n ity c o m p a red to exam ples fro m th e E nglish C hannel a n d C hile. G u errero (1989) re p o rte d a m axim um in fau n al bio m ass for A hous Bay, Q a y o q u o t Sound, of 1 6 0 g / m^ - considerably less th a n th a t fo u n d in the m ain fe e d in g g ro u n d s. M ore recen t sam p lin g p ro g ram s re p o rt so m e w h at low er values: 3 8 g / m^ (C ow Bay) a n d 2 1 g / m^ (A hous Bay) in 1996, 9 7 g /m ^ (Cow Bay) a n d 7 4 g / m^ (A h o u s Bay) in 1997 (D unham , 1999). C a rru th e rs (2000)
converts D u n h a m s w e t w eights to d ry w eig h ts for co m p ariso n to h e r o w n data, w hich sh o w m u c h lo w er biom ass - less th a n 75% of D u n h am s v a lu e s, for a com bined n u m b e r rep resen tin g b o th A h o u s Bay a n d C ow Bay.
