Sighting analysis and photo-identification of humpback whales off Western Australia, 1989

12 Pages·1991·3.6 MB·English

by  C L K Burton

,
SIGHTING ANALYSIS AND PHOTO-IDENTIFICATION
OF HUMPBACK WHALES.
OFF WESTERN AUSTRALIA, 1989
CHRISTOPHER L.K. BURTON
Burton. C.L.K. 1991 07 01; Sighting analysis and photo-identification of humpback
whales,offWestern Australia, 1989. MemoirsoftheQueenslandMuseum50(2): 259-270.
Brisbane. ISSN 0079-8835.
During 1989,4-92humpbackwhalesMegapteranovaeangUaeoitheSouthernHemisphere
Group IV stock were observed off the Western Australian coast, and 118 of these were
photographically identified using tail fluke and lateral body pigmentation patterns. Most
observations were made during whale-watching cruises conducted off Perth, with the
highest sighting rates (whales/sighting hour) being recorded in September and October-
Sightingsofmother-call"pairsincreasedinNovember.Toimproveefficiencyofidentifica-
tion, animalswere classified into4 Types accordingto the proportionsofwhite and black
pigmenton the lateral body and the ventral side ofthe tail flukes. Thedegreeofcoverage
ofyellowcolourationon the tail flukes,presumably causedby the diatomCocconeis,was
classified using the same proportional method. Humpback Whale, Megaptera
novaeangUae, pigmentation, photu-tdentiftcation, sighting.Western Australia.
Christopher L.K. Burton, cl- W.A. Marine Research Laboratories, P.O. Box 20, North
Beach, WesternAustralia6020; 20December 1990
Humpbackwhales(MegapteranovaeangUae) where much research has been conducted into
V
which migrate along the Western Australian identification and monitoring of the Area
coast,comprisethe SouthernHemisphereGroup population (Bryden & Slade, 1987; Bryden,
IVstock thatwasseverely depleted by commer- Corkeron & Slade, 19S8; Kaufman, Smultea &
cial whaling from an estimated 12.000-17,000 Forestell, 1987; Paterson &. Paterson, 1989).
animals to c. 800 by 1962 (Chittleborough, In Hawaii, observations from consecutive
1965). Recentaerial surveys show thatthestock yearsofcommercial whale watchinghavebeen
has been increasing, havingat leastdoubled be- used to investigate changes in humpback pods
tween 1963 and 1982, and having continued to and calf encounters (Salden,1988). In Perth,
increasesince then (Bannister, this memoir). On whalewatchingtoursbyUnderwaterWorldfrom
that basis the stock may now be more than 2000 Hillary'sBoatHarbourprovidedavaluable plat-
animals. form for research on humpback whales. This
Tail fluke photography is a valid means for paperpresentsin twoparts, resultsfrom anal
humpback whale identification (Katona, 1979; of photographs obtained during 1989 and from
Giockncr & Venus, 1983; Baker et al., 1986; data collected during the whale watching
Stone, Katona & Tucker, 1987). Photographing cruises.
the lateral body pigmentation patterns in addi-
tiontoflukesincreasesthenumberofindividual- PART 1 - PHOTO-IDENTIFICATION
&
ly identified whales (Kaufman, Smultea
Forestell, 1987). Methods
Photographicidentificationofindividualswill During July and August 1989, humpback
assist in analysis ofmigration patterns, distribu- whales were photographed in Shark Bay from a
tion and stock identity of this population of 5.3m runabout, andoffNorth West Cape from a
humpback whales. Whale watching tours pro- professional fishing boat. From September to
vide an opportunity to photograph many in- November 1989,photographswere takenduring
dividuals and collect abundance and pod whale watchingandfroma5.4m runabout. Loc-
composition dataoverashorttime span within a ations ofall sampling areas are shown in Fig 1
specific area. A 35mm SLR camera with a 35-200mrn
Watching humpback whales has become a zoom lens was used for all photographs. The
viable industry on the east coast of Australia, largertouroperators' vessels operatorscameno
260 MEMOIRS OFTHE QUEENSLAND MUSEUM
1 -; 125E
^
-'' !/•
t ARCHIPELAGO
ays
1. RtH-ft£51 CAPE WESTERN
:-if'
_.,,a--•\ B» 1 AUSTRALIA
-22s :7-ii106 \ PERTH -~
•^
k.
FIG, I. Humpback whale observations and
photographs, 1989. (observaiions/photo-ids).
closertothewhalesthan50m. Interferencetothe
pods was minimised, and often good
photographs were obtained w*ben whales them-
selves became the curious observers.
Data collected included details of pod struc-
ture, behaviour, time and photographs. Adults
were presumed to be female only if in close
association with a calf. Differentiation between
adults and subadultswas not made. The number
ofwhalesobserveddailywasrecorded,asnotall
whales^could be photographed. Copies of the
photographsweresenttotheWesternAustralian
Museum and to the Pacific Whale Foundation
for use in compiling catalogues.
Classification of the lateral colouration of TYPE 4
individualsfollows thatdescribed by Kaufmann
et al. (1987) (Fig. 2) using the proportion of
white pigmentation on the lateral body, with FIG. 2. Lateral body pigmentationtypesdisplayedby
Type 1 having the greatest and Type 4 the least Australian Humpback Whales. Illustrations by Lili
(lFatiegr.a3l).boWdhyalwehsewnhsiucrhfadciidngnottoparcecsuernatteslufyfcilcaisesn-t dHaatgieonn..TcoYuPrtEes1y,oWfhGi.leKacuoflomraant,ioPnacriefaicchWeshaalbeovFeoutnh-e
horizontal mid-line of the body, generally extending
ify were classified as undetermined. anterior to dorsal fin. TYPE 2, White coloration ex-
Colouration of the ventral sides of the tail tending to body midline or above, with coloration
flukeswasalsoassessed, usingasimilarpropor- generallyobservednearthecaudal peduncle.TYPE3,
tional method to the lateral colouration, with An obvious bul less distinct whitish-grey coloration
Type 1 mostly white and Type 4 mostly black. patch along the dorsal surfaceofthe caudal peduncle
The flukes were divided by a straight line from posterior to the dorsal fin. TYPE 4, Lack ofobvious
whitepigmentationpatterns.
HUMPBACK WHALE SURVEY, W.A., 1989 261
Type 2
Type 4
FIG. 3. Identified Humpback Whales from W.A.,showing4 lateral pigmentalion lypes.
Type Type 2
1
Type 3 Type 4
FIG. 4.Tail fluke pigmentalion lypesofhumpbacksoffWA.
262 MEMOIRS OFTHE QUEENSLAND MUSEUM
WA
FIG. 5. Identified humpback whales from showing4 tail fluke pigmentation types.
Type 2Y
Type 3Y
....,..'
•
-
FIG. 6. Photographsofidentified whales offWA, showing3 ofthe 4 tail flukediatom colouration categories
(yellow).
HUMPBACKWHALE SURVEY, W.A., 1989 263
4*
*NPS>
D
FIG. 7. Tail flukepigmentation and diatom colouration photographsofaresighted humpb; SharkBay,
12 July, 1989. B, Perth, 27 and 30 September, 1989.
264 MEMOIRS OFTHE QUEENSLAND MUSEUM
the fluke tip to the centre of the median strip LATERALPIGMENTATION
cb2aeattnewgdeoeTrniyspeeeadc3ahsafnhliaukmveailntsgoa(<sF5siig0s.t%4i)nb.ldAaectkTeyrppmieignm2iennfgtlauTtkyiepoiens TCaytpeego1r(ymostlywhite No.of1w4hales % o2f8t%ypes
and a Type 3 fluke having >50% black (Fig.5). Type2(<50%black) 9 18%
Many identified animals had some yellow Type 3 (>50% black) 7 14%
colouration on the underside of the flukes, Type4(mostlyblack) 20 40%
presumably due toafilm ofthe Antarcticdiatom Undetermined 16
Cocconeis ceticola. The typically yellowish Total 66
colour of this species on the skin of whales in
warmer waters ofthe Southern Hemisphere has TABLE3.Classificationofwhalesondegreeoflateral
been taken to indicate movement of the whale pigmentation. Undetermined whales were identified
fromcolderwaters(Bannister, 1977).Thedegree by body marks, scarsordorsal fin characteristics.
of diatom coverage on the underside of the tail
flukes was assessed using the proportional FLUKE PIGMENTATION
method describedabove forthewhite/black pig- Category No. ofwhales % oftypes
ymeenltlaotwiaonndpTatytpeern4s,bewiintgh mToysptely1yehlalvoiw.ngTyliptetlse Type 1 (mostlywhite) 50 75.8%
2 and 3 animals have < and >50% yellow Type 2(<50% black) 13 19.7%
colouration, respectively (Fig.6). Tail flukes of Type3 (>50% black) 3 4.5%
animals which were too distant and had uneven Tvpe4(mostlyblack)
lighting, or which were at too low an angle to Undetermined 4
accurately see the black and white or yellow Total 70
colouration, were classified as undetermined.
TABLE4.Classificationondegreeofwhiteandblack
pigmentation on the underside ofthe tail flukes.
RESULTS DIATOMCOLOURATION
Category No. ofwhales %oftypes
LOCATION NO. OFWHALES Type 1 (mostlywhite) 15 36.6%
Type2(<50%yellow) 24 58.5%
observed photo-ID
Type3 (>50% yellow) 2 4.9%
Perth 474 106
Type4(mostlyyellow)
Shark Bav 14 V
Undetermined 29
NorthwestCape 3 2
Total 70
DampierArchipelago 1 1
TOTAL 492 118 TABLE5.Classificationondegreeofyellowcoloura-
TABLE 1. Humpback whales off WA during 1989. tion (diatoms)on the underside oftail flukes.
Observations were made by the authorexcept for the DIATOMCOLOURATION
oanned 6of9f IthDesDwaemrpeimeardAercdhuirpienlgawgho.ale41w7atocbhsienrgvattoiuorsn.s zo TYPES 1 2 3 4 Undet
1 11 20 2 16
Class Lateral body Lateral body Flukeonly Total 2 3 4 6
orfluke only -LIJ. 2o 3 1 2
Adult 13 40 50 103 ou 4
Female 5 1 2 8 Undet 5
Calves 7 7 TOTAL 15 24 2 29
Total 18(15.2%) 48(40.7%) 52(44.1%) 118
TABLE 6. The degree ofdiatom coverage according
TABLE 2. Humpback whales identifed on lateral or to flukecategorisation type.
fluke pigmentation patterns. Calves identified by
lateral observation asnonewereobserved flukingup. One animal, identified in Shark Bay, was
categorisedasType2yellow,andwasstill inthat
. 1
HUMPBACK WHALE SURVEY, W.A, (989 265
category when resight cdoffPerth 77 days Inlet Categorising fluke patterns may helpsimplify
with very little change in diatom distribution on resight analysis, as each ID can be placed in a
its tail nukes (Fig. 7). type category rather than beingchecked against
all other animals.
INITIALSIGHTING RESIGHT1NG
Diatom Coverage
location Date ID Location Date Elapsed
j Na Assessment ofyellow colouration on specific
Shark B. : 12,7.89 4 I'-rl.T 27.9.S9 77 ewrhnalemisgwrhaitciohnmamyaybeerneasbilgehteqduaanftteirtatthievirencorotmh--
Penh }ii y ,-;v 4 parison over time of the change in diatom
Penh ' Q.I 1,84 100 Perth ixi ..v< 7 coverage, Colourphotographs of flukes arc bet-
Penh •;.1 1,89 101 F'erlh 1- i 1..S4 7 ter for assessment of diatom coverage than arc
black and white photographs. Of41 individuals
TABLE 7, Restghtings during 1989. categorised, 95% had <50% diatom coverage
whereas on the east coast there was little
DISCUSSION evidence ofdiatom coverage at all (M.Osmond,
pers. comm). Difference in diatom coverage be-
During the present study which focussed tween Groups IV and V stocks may reflect
predominantly on the southern migration. 41% geographical differences in the Southern Ocean
ofanimals were identified usingonly lateral and feedingareas,butfurthercomparisonsarcne
44% using only fluke pigmentation patterns, sary before making any conclusions.
compared to25% and 17%ofthe animalsofthe It is unclear how differences in diatom
Area V stock on the east coast (Kaufman ci ul. coverage relate to different fluke colourations.
t
I 9S7V hithermore, a higher number of iden- The extent to which diatom coverage may have
tified animals £58%) was obtained using either been reduced by time spent in warm waters is
Literal or fluke patterns on the east coast com- unknown
pared to 15% on the west coast. This large dif-
ference may icilecl the greater ease of man- Rbstghts
oeuvrability ofsmaller craft and the persisted e Amother-calfpairwassightedtwice in7days
of the researchers in obtaining both lateral and in the same area off Perth, while another in-
fluke photographs ie. a difference in methods. dividual was resighted after4 days. Many mure
19X9 was the first year in which a concerted whalesarc seenoffPerth and south coastal an;is
effortwasmade to identify many animalson the from SeptembertoDecemberthanatothertimes.
westcoast. Certainpopulationclasses,forexample,mother-
calf pairs, may use the large bays and embuv-
Lateral Pigmentation ments off Western Australia (Shark Bay.
The 28% Type 1 and 40% Type 4 of my Geographe Bay, PertfvRot(nest) for 'testing'
observationscompare with 1% Type 1 and 37% areas during theirsouthern migration. Photo-ID
Type 4 in eastern Australia (Kaulman el id. in Hawaii indicates residence times of up to 1
1987). From these initial data, it appears that the weeks (Darling,Gibson & Silbcr, 1983), and in
Group IV stock has a larger proportion of 1ype Hervey Bay, Queensland, times ofmainly I to2
animals. days, and up to 19 davs (Bryden, Corkeron &
I
Slade, 1988).
With the development ofwhale-watching as
Fluke Pigmentation an industryoffthecoastofPerth, informationon
Ihe 70% Type 1 and 95% Types 1+2 of my the distribution, behaviour, identification and
observations compare with 87% of flukes from ecology of whales will be essential, to properly
984,85 animalsoftheGroupVstock being75% understandandmanage theinteractionsbetween
1
white (Kaufman et aL, 1987). In the Northern people and whales.
Hemisphere nearly 62% of animals, including
calves, had mostly black flukes (Glockner and PART2 - SIGHTING ANALYSIS
Venus, 1983); their Types 4 and 5 equate to my
Type 4. Although I identified no mostly black Methods
flukes, at least 2 were photographed by other Whale-watching tours are conducted from
people (G. Pobar, pers comm). September to November during the southern
266 MEMOIRS OFTHE QUEENSLAND MUSEUM
?£R7t>
PERTH
FIG. 9. Numbers ofhumpback whales(adults + cal-
ves)observed ineach grid square during the southern
migration.
Vessel
Two vessels were used for the tours; a 15m
aluminium monohull fishing vessel and a 10m
fibreglasssharkcat. The largervessel had radar,
and was used on most occasions. The vessels
departed from the boat harbour at Hillary's and
headed southwest towards Rottncst Island
around thesouthern most Centaur Reef. At least
2 or 3 observers were continually looking for
whales, and on most occasions the blow was the
FIG. 8. The area ofIndian Ocean between Penh and initial sighting cue.
Rotlnest Island where ihe whale watching lours were
conducted during 1989. DataCollection
Cruise description data gave starting and en-
migration of humpback whales which occurs dingtimesandweatherconditionsduringobser-
between August and December. vation outside the fringing reefs. Locations of
pods were specified by radar or compass bear-
Area ings. A cruise path description was made on a
The Indian Ocean, adjacentto Perth and north grid as it was not possible to continuously plot
of Rottncst Island, was divided into grids of each cruise using more accurate equipment.
approximately 2 x 1.8 nautical miles to define Sighting data consisted of individual whale
sightings distribution (Fig 8). Tours were con- counts,podsizes, reproductivestatus,behaviour
ductedwestoftheshallow limestonereefswhich and photographs. Searching time included that
run parallel to the coast, and north of Rottnest spent with each pod and assumes that searching
Island, generally when wind speedswere below continues while with one pod. Searching time
15-20 knots. with the vessel moving would have been much
HUMPBACKWHALE SURVEY, W.A., 1989 267
pairswere obvious, evenwhen otheradultswere
nearby.
ADULTS RESULTS
CALVES S3
ac/3
o
pzo5 <>Q• UfuiJti oaa. C|Q</3 CU>-</JJJ Ooa. Ua<QJ._
UJ
Sept 6 7 21 65 2 . 3
Oct 21 34 77 265 13 3 11
Nov. 14 iy 25 48 20 5 ]
Jmil Dec 3 3 2 *> j i 1
10 20 30 40 50 Total 44 63 125 380 37 9 16
CRUISE DAYS
TABLE 8. Monthly data collected during whale
FIG. 10. Adults + calves sighted per day during the watchingcruises.
cruises, from September to December (southern
migration), Perth, 1989.
XOS
t/3 t/3
less if time spent with each pod had not been pzS ><a U5J U-<XJj MEAN HR/CRUISE 5U-<J5J
included. c X
PhotographicDocumentation
Effortswere concentrated in obtainingphotos Sept 6 7 67 3.54 3.24
of the ventral side of the tail flukes and lateral Oct 21 34 278 3.28 3.82
viewsofeach whale. Whaleswere inferred tobe Nov 14 19 68 3.20 1.67
female if accompanied by a calf; mother-calf Dec 3 3 4 2.36 0.55
'
1 TABLE9. Summary ofcruisesearchtime, numberof
whalesand dailysighting rate.
An ANOVA was performed on the trans-
formed data (loglO) to test differences between
A
monthsforwhales/cruisehour. significantdif-
ferencewasnoted(F=5.32,df=43,P=.0035),and
tests (Tukey,Scheffe,SNK) between monthly
means indicate that December is different from
the remaining months. Removing December
also resulted in a significant difference for
I ' November (P=.0092) from Sept-Oct.
DISCUSSION
No comparative data on humpback whale
12
MONTH numbers in the near shore waters off Perth are
available;estimatedpopulationsizeismorethan
2000. It may be that a significant proportion of
sFiIgGh.ti1n1g. hHouumr;pbsaouctkhewrhnalmeisgr(aatdiuolnt,s+Pecrathl,veSse)ppteermdbaeirl-y tuhseinpgoptuhleatliaorngemibgaryasteassoruetsthincgloasreeatso.tTheocwoahsatt,
December,1989 (mean ± SD). extent and duration these bays are used remains
268 MEMOIRS OFTHEQUEENSLAND MUSEUM
N-381
i 6 7 B 9 10 15 20
ADULTPODSIZE
FIG- 13. Frequency ofpod sizesobserved duringthe
southernmigration, Perth, 1989.
FIG.12. Pods ofhumpback whalesobserved perday
during thecruises; southern migration, Perth, 1989.
to be determined. Tbe photo-id work in 1989
N«37
indicates residence times of4-7 days offPerth.
The distribution of whales over the gridded
areasuggeststhatthey limittheirapproachtothe
coast to depths greater than 20m. Concentration
of sightings in the southern region ofthe study
A
area reflects cruise paths. series of aerial sur-
vey flights over the area would provide a more
accurateestimationoftheirdistribution and give
some indication of the proportion of whaies
which pass at a greater distance from the coast
andare not seenbythecruisevessels. Theeffect
of the warm, southward flowing Leeuwin cur-
rent along the Western Australian coast on the
spatial distributionofthese animalsmay have to
be considered. The number of adults decrease ^
from October. Since the cruises did not com- £3
mence until late September the initial rise in
numbers was missed, and may follow a normal
disribution curve, similar to that observed in ADULTPODSIZE
Queensland from shore (Bryden et at., 1987).
The numberofcalves increased in November,
as previously noted (Chittleborough, 1965). FIG. 14. Frequencyofcalveswith differentadultpod
This earlier work by Chittleborough also indi- sizes observed during the southern migration. Perth,
1989.