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1-ig . .3. Diurnal cycle!> of crahcater scab on ::!!! January 1971\. King Haakon VII Sea: number of seals on ice floe~ (- -).

seals seen s11imming ( ), air tempcrawre (· ) and sea temperature(·- -).

Ackno\\ ledgemcnts

I thank Professor J. D. Skinner, Director of the Mammal Research Institute, for nominating me to undertake this

~urvey, and the Department of Transport for providing facilities and logistical support. The co-operation from Captain

E.

Funk and the officers and crew of the RSA was outstanding. Thanks arc also due to Or H. Bergh of the Bernard Price Institute. University of the Witwatersrand, for the navigational data. and to Mr J. Hope for his assistance during the seal survey.

References

Bonner. W.N. & Laws, R.M. Seals and sealing. In Antarctic Research. edited by Sir R. Priestly. R.J. Adie & G. de Q Robin.

London. Buuerworth~. pp. 163-190. 1964.

Condy. P.R. The Ross seal Ommmop/wca rossi (Gray 1850), with notes from the results of surveys conducted in the King Haakon Vll Sea, Jan/Feb 1974-1976. In Proce(•dinf{s of a S,J·mposium o11

Endangered Wildlife in Sowflem Ali-ira. Johannesburg, En- dangered Wildlife Trust, pp. 88-104. 1976.

Eklund, C' R. & Al\1ood, E.L. A population study of Antarctic seals. J. Mammal., 43, 229-238, 1962.

l:klund, C.R. Population Studies of Antarctic seals and birds. In Binlogie Antarctique. edited by R. Carrick. M. lloldgate and J. Prevost. Paris, Hermann, pp. 415-419. 1964. Cited by Orits- land. 1970a.

Erickson. A.W .. SinifT. D.B .• Cline. D.R. & Hofmar1, R.J. Dis- tributional ecology of Antarctic seals. In Sympo.l'ium on Ant- arctic Ice and Water Mas.1es. edited by Sir G. Deacon. Cam- bridge. SCAR. pp. 55-76. 1971.

Haii-Manin. A.J. Observations on population density and species composition of seals in the King Haakon VII Sea. Antarctica.

S. Ajr. J. Antarcr. Re.1., ~. 34-39, 1974.

Hall-Martin, A.J. Report on the initiation of a research project on ecology. physiology and ethology of Antarctic seals. Unpub- lished manuscript. 1\lammal Research Institute. Unilersity of Pretoria. 1974.

Kcnyon. K.W. Antarctic seal observation•. February 1967. Un- published rcnorts, U.S. Fish and Wildlife Service. Sandpoint Naval Station. Seattlc. Washington. 1967. Cited by Siniff.

Cline and Erickson. 1970.

King. J.E. Sea/.1 vf' the 11 or/d. London. British Mu,eum (Natural History). 1964.

lHws. R.M. 1 he seals of the Falkland Islands and Dependencies,

01')'.\', 2. 87-97. 1953.

Lm1s. R.M. Comparative biology of Antarctic scab. In Bioloxie lluarctitfut. edited bJ R. Carrick. J\1. Holdgate & J. Prcvost.

Paris. Hermann. pp. 445-454. 1964.

Mansf1eld. A.W. The breeding behaviour and reprodu~.:tive cycle of the Wcddcll seal (Lepton,rdwtes Wl'ddellf Lesson). Sl'i. Rep.

Falt..land /lland1 Depem/enl'it•\ Sun·e1·. 18, 1-41. 1958.

MariOI\, B.J. Mating behaviour in the leopard seal, Hydrurga leptonyx (Mammalia: Phocidae). in captivity. Austral. J. Zoo/., 15, 1-5. 1967.

Nel, J.A.J. On the behaviour of the crabeatcr seal Lobodon carcino- plwgus (Hombron & Jacquinot). 7oologica africana, 2, 91-93, 1966.

ritsland, T. Biology and population dynamics of Antarctic seals.

In AntarNic Ecology, vol. I, edited by M.W. Holdgate. London

& New York, Academic Press, pp. 361-366, 1970a.

o/Jritsland, T. Sealing and seal research in the South-West Atlantic pack ice. Sept-Oct 1964. In Anwrctic Ecology, vol. I. edited by M.W. Holdgate. London & New York. Academic Press, pp.

367-376, 1970b.

Prevost, J. Observations complimentaires sur les pinnipedcs de I'Archipcl de Pointe Geologic. Mammalia. 28, 351-358, 1964.

Ray. C. The ecology of antarctic seals. Amarct. J. United States, I, 143-144, 1966. Cited by Oritsland, 1970a.

Ray, C. Population ecology and Antarctic seals. In AntarNic Ecology, vol. I, edited by M.W. Holdgate. London & New York, Academic Press. pp. 398-414. 1970.

Siniff, D. B., Clinc. D.R. & Erickson. A.W. Population densities of seals in the Weddell Sea. Antarctica, in 1968. In Amarctic Ecology, Vol. J. edited by M.W. Holdgate. London & New York, Academic Press, pp. 378-394, 1970.

Stirling, I. Distribution and abundance of the Weddell seal in the Western Ross Sea. Antarctica. N.Z. J. marine j'reshwmer Res., 3, 191-200. 1969a.

Stirling, I. Ecology of the Weddcll seal in McMurdo Sound, Antarctica. Ecology. 50, 573-586, 1969b.

Stirling, I. Population dynamics of the Weddell seal (Leptonychotes weddel/i) in McMurdo Sound, Antarctica. 1966-1968. Ant- arctic Rest•arch Series of the American Geophysical Union. 18, 141-161, 1971.

Stirling. I. Regulation of numbers of an apparently isolated population of Weddell seals (Lepmnychotes weddel!i). J.

Mammal., 53, 107-115, 1972.

Stirling. I. Movements of Weddell seals in McMurdo Sound.

Antarctica. Austral. J. Loo/., 22, 39-43. 1974.

Stirling. I. & Greenwood, D.J. Observations on a stabilising popu- lation of Wcddell Seals. Austral. J. Zoo!., 20, 23-25, 1972.

Stirling. I. & Kooyman. G.L. The crabeater seal (Lohodon carcino- phagw) in McMurdo Sound. Amarctica. and the origin of mummified ~eals. J. Mammal., 52, 175-180. J 971.

Wilson. V.J. The second seal survey in the King Haakon VU Sea, Antarctica January1February 1975. S. Afr. J. AwarN. Res., (in press).

Wilson. V . .l. Results of the second seal survey carried out in the King Haakon VII Sea. Antarctica. Unpublished manuscript.

Mammal Research lru.titute, Uni1ersit) of Pretoria. 1975.

enkovich, B.A. Sea mammals as observed by the round-the-world expedition of the Academy of Sciences of the USSR in 1957/58.

Norsk 1/1'(1/j(mgsf/id, 51, 198-210. 1962. Cited by •Zlritsland, I970a.

S. Afr. J. Antarct. Res., Vol. 6 1976 9

Design and application of a coded format for recording observations of cetaceans at sea

P.G.H. Fr ost Percy Fitzpatrick Institute, Universi ty of Cape Town, Private B ag, Rondebosc h, 7700.

P.B. Best Sea Fisheri es Branch, Depa rtment of Industries, Private Bag, Sea Poi nt, 8060.

A 11umericalformat for recordi11g details of the mai11 ide11ti/ying fea/llres of cetaceans see11 at sea is give11. Each idemifying character is divided imo a munher of character stares which are coded munerica!ly. This coded format is intended primarily for recording details of cetacean sigltti11gs hy observers who are not experienced in cetacea11 idelltification, inc/udill!f those sightillf{S for which a positive identification is impossible. This should mi11imise rhe risl. of i11correcr idemifications and loss of potemia!ly useful data i11corporated in such sighrings, as well as facilitate the subseque11t retrieval of such data .for use In broad analyses of the tre11ds in ceracean disrributiOII a11d abundance. The format is designed here for the sourhem Indian Ocean and is applied to a series of 34 obser1•ations made in rhar area during March and April 1976. The most frequently recorded species was the sperm whale Physeter catodon, which was distributed between 25° and 40° S. New distributional data are reported for rhe common pilot whale Globicephala melaena and Wilson's hourglass dolphin Lagenorhynchus cruciger. A possihle record of the specTacled porpoise Phocoena dioptrica is noted.

·, Syferformaat vir die aanteke11ing van beso11derhede oor die

hooj~idemifisere11de kenmerke 1•an Cetacea wat ter see gesien word. word aangehied. Elke identifiserende karakrertrek word in 'n aamal ke11merk roesttmde wat 1111111erie.r gekodeer word onderverdee/. Hierdie gekodeerde formaat is primer bedoel vir die aanteke11ing ''all hesonderhede oor waamemings van Cetacea deur waarnemers war 11ie ondervinding l'llll hut identifisering het nie, insluite11de dam·die waamemi11gs waarby ·" positiewe identifikasie omnoontlik is. Dil behoort die risiko van verkeerde identifikasies e11 die verlies va11 pote11sieel 11uttige data wat sulke waamemings inhou, tot die mi11imum te beperk, e11 ook die herwinning daama van sulke gegell'ens vir die ont/eding 1'011 brei! tendense in die verspreiding en ralrykheid van Cetacea re vergemak/ik. Die lwidige formaat is vir die suidelike lndlese Oseaa11 ontwerp e11 word op ·n reeks va11 34 waamemings wat in dam·die gebied gedureude Maarr e11 April 1976 gedoe11 is.

roegepas. Die potvis Physeter catodon was die spesies wat die meesre gesien is en het tusse11 25

°

en 40

°

S voorgekom. Nuwe gegewens oor die verspreidinlf van die gewo11e loorll'lvalvis Globicephala melaena en Wilson se uurglasdol[yn Lageno- rhynchus cruciger word geboekstaal ·, Moontlike rekord 1•an die briltomyn Phocoena <lioptrica word rermeld.

Introduction

With the possible exception of some of the larger whales, there are few comprehensive data on the distribution and abundance of most cetaceans at sea. Much of the present knowledge for large whales has been derived from records of whale catches (for example, Townsend, 1935) or catch per unit effort (Omura, 1973). from observations from scouting vessels attached to whaling expeditions (Masaki. 1976). or during whale marking cruises (Gambell. Best & Rice, 1975). How- ever, in most cases the search pattern is unknown or has not been systematic, but has tended to be concentrated on estab- lished whaling grounds. These observations need to be

extended to other areas in order to obtain an overall picture of cetacean distribution and abundance. Furthermore. these data have been gathered largely by observers experienced in large whale identification. With the severe reduction in commercial whaling activity over the last decade, the oppor- tunities for and scope of such observations have become increasing!)' limited. If research effort on whale distribution and abundance is to be maintained. it is obvious that other platforms (including relatively naive observers) will have to become involved.

Organised whale-sighting schemes, whereby observers on board naval and merchant ships made observations, have been run in the past by the Nationallnstitute for Oceanography in Britain and the Netherlands Whale Research Group T.N.O.

(Brown, 1957; 1958; Slijper, Van Utrecht & Naaktgeboren, 1964). Both these schemes, however, encouraged observers to identify cetaceans seen using identification keys or figures provided. Only in some instances "'ere the resulting obser- vations accompanied by supporting evidence for the identification in the form of descriptions, sketches or photo- graphs. Both sets of workers classified all large whales seen as either sperm, humpback. rorquals or large whales. Although this approach undoubtedly has its merits, its disadvantages are:

• the uncertainty regarding the validity of identifications unaccompanied by supporting evidence. and

• the loss of a considerable amount of potentially useful data from sightings of unidentified animals (for example.

rorquals, or large whales).

The drawbacks and dangers attached to the use of such a scheme by inexperienced observers are well discussed by Schevill (1968).

The smaller cetaceans present even greater difficulties in identification due to their small size, rapid movements and (sometimes) their unwillingness to approach ships. Guides for their identification have been produced (notably Leatherwood.

Evans & Rice, 1972), but these also encourage observers to attempt to identify animals by use of a key without providing for retention of the basic criteria seen and used in identifi- cation (although sketches are recommended in some cases).

This approach ha~ the same drawbacks as mentioned above for the sighting schemes for large whales, though the prob- lems are greater here because of the increased likelihood of misidentification and, in parlicular, the greater frequency of incomplete sightings. In fact, because identification of these animals to specific or generic level is frequently not possible on the details observed, such observations are usually C'\-

cluded from analyses. Much potentially vah.mble information may be lost in this way. The problem therefore is to devise some method of recording concisely those details that can facilitate preliminary identification, at least to a ta .... onomi c group, thereby minimising the loss of any potentially usefu I information.

Incomplete sightings often incorporate some diagnostic features which can serve to narrow down the range of possible

10 S. Afr. T. Antarkt. Nav .. Deel 6, 1976

species. Therefore any method of recording Information should ensure that the most useful identifying features arc looked for preferentially and are recorded in a standard and systematic manner. without resorting to a dichotomous or other key.

character seen will therefore be recorded as a set of four numerals. the first two of which designate the character and the latter two the particular character state. A full sighting would consist of a series of these enumerated sets.

We ha'e tried to make the choice of altcrnati\e character states as comprehensive as practical. but for certain character:.

the choice of detailed alternatives is so large that it is impractical to include them. Hence we opted for the inclusion of those characters which are of greatest use in aiding the identification of' a particular group of species. For example, we have divided colour patterns into broad categories of pattern type. rather than attempted to describe separately all the distinct but subtle variations that e"\ist. While the latter would certainly facilitate positive identification of many species, it is not our intention to construct an identification 1-ey (which might well lead to misleading identifications). but rather to ensure that the greatest amount of useful infor- mation is recorded for each sighting.

The purpose of this paper is to present the details of such a system, and to demonstrate its applicability to a series of hitherto unpublished observations made by one of us (who was inexperienced in cetacean identification) in the south- western Indian Ocean during March and April 1976.

Method

We have compiled a list of the most obvious and frequently seen characters for those cetaceans previously recorded from the southern Indian Ocean. Most of these characters are key features in the identification of species. Each character is coded numerically to facilitate recording the observation in

a

concise manner. The characters arc: Each sighting should be accompanied by standard details such as date and time of observation, exact position (latitude and longitude), number seen, estimated site of the animals, and adult to juvenile ratios if possible. In addition the minimal environmental data required arc sea surface tempera- ture. sea state (or wind speed), cloud cover and visibility. Any associated organisms, such as flocks of scabirds or other cctaccan species. should be recorded. Sketches or photo- graphs of animals seen can provide valuable supplementary evidence of identity, and should be included whenever possible.

01. Body size class 02. Blow shape 03. Blow frequency

04. Blow synchronisation within group 05. Swimming behaviour

06. Reaction to vessel

07. Exposure of tail flukes or flipper (apart from jumps) 08. Dorsal fin position

09. Dorsal fin height 10. Dorsal tin shape (Fig. 3)

11. Colour of dorsal fin and back just behind fin

Application

12. Head shape

13. General body colour 14. General colour pattern 15. Flipper shape and colour

Each of these characters has been divided into a number of character states which are also coded (Appendix I). Each

In order to test the feasibility of this method we have applied the coding system to a series of observations made by one of us (P.G.H.F.) during cruise MOOS of the research ship M.S. Mm·ion Du/resne from 8 March to 26 April 1976. The cruise tracks covered approximately 10 000 nautical mile!>

Dnte Time (b) 10-03-76 1245 12·03-76 1815

13~3-76 0745 0753 1335 1600 1650 1735 14·03-76 0845 1358 1844

~~~3-76 0836 1305 1530 20-0J-76 0817 24·03-76 1130 25-03-76 1750 26·0.1-76 0650 1045 29-03-76 1430 31-03-76 0935 1-04-76 1015 l-04-71\ 1400 1430

183~

1840 5-04-76 07 30 1450 6-04-76 1743 7-04-76 0910 0915 10-04-76 0745 0930 11-04-76 1345

La1.

28 OS'S 28 07'S 27 49'S 27 49'S 21 42·s 21 39·s 27'4J'S 27' 44'S 21· 42·s 28 29·s 29 30'S 30 24·-;

31 25

s

31 5~'S

41 06'S 46 40'S 46 ~I'S

46 4o·s 4(• 4s·s 46 4o·s 45 5'1 s

47 411 s 49 +Is 49 4~ s 49 2<1 s 4'1 29·s J6 45·s 35 16'S 2S WS 25 03 s 25 03'S 26 21"S 2(> 45 s .n 21 s

Table I

Sightings of cetaccuns in ,ourthen Indian Occun March-Aprit 1976. S1.-c tc\t tor furrher detaob Long.

SS 15'E 51 54'E 48 18'E 48< 19'F 46'46'E 46°2l"E 46'27'E 46"27'E 46 26'E 46 1s·e 45 s2·E 45 41 E 45 07'E 44 45·e 52 09'E 40 li'E 37 55'E 38 03'E 38 04•E 38 OO'F 50 28"E 58 09·E 6S 42.E 69 00 E 70 15'E 70 lYE 63 ITF 62 27'F 59 05'E 57 20'E s1

2o·e

54 12 E 54 09 E 53 IO'E

Ts (Cl 27.0 28.0 27.2 27.2 28.0 28.0 2g.o 28.0 26.5 27.0 2U 27.0 27 0 27.0 I J.J 7.4 7.1 7.11 7.11 7.1 76 7.ll

~. 1

~.1

~.4

5.4 I').J 22. I 27.1 :!7.2 27.:!

27 I 27.0

22.~

No. ldentilication code lclcntificmion

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15

3 01 03 04 01 00 00 07 03 02 10 03 00 06 00 00 1'/nwtrr catodrm 6- 03 01 00 00 03 00 00 02 03 02 03 00 10 02 00 tlolphon (unidentified) 4 01 0.1 04 01 00 00 07 00 00 00 00 00 00 00 00 Plr.nrtrr rMOlfon

03 00 00 00 01 00 07 02 00 00 00 00 00 00 00 dnltlhin (unidentified) 0 I 0.1 04 0 I 00 00 07 00 00 00 00 00 00 00 00 Plw<t'lt'r C"illodoro 01 03 04 01 00 00 07 03 02 10 O:J 02 06 00 00 l'ho·wrt•r twrodrm 01 07 04 00 00 00 00 00 00 00 00 00 07 00 00 lnrge whak (unidentilictl) 01 02 00 00 00 00 00 00 (XI 00 00 00 00 00 00 lnrgc "hnlc (unidcntilicd) 01 08 02 00 00 00 00 ()() ()() 00 00 00 00 00 00 horge "hale (unidcntilicd) 03 01 00 00 00 00 03 02 00 00 00 00 10 00 ()() tlolllhin (unidentified) OJ 01 ()() ()() 00 00 07 00 00 00 00 00 06 00 00 dolphin (unidentoficd) 01 03 04 00 00 00 00 00 ()() 00 00 00 00 00 00 Phnc·tc•r rmO<Iun 1 01 02 02 00 00 00 00 00 00 00 00 00 00 00 00 larpe "hale (unidentified) 39 03 01 00 00 0.1 04 00 02 03 02 0.1 06 10 06 00 Srnwlfa cO<•rtilrr><uhu

9 03 0 I 00 ()() 0 I 02 07 02 03 03 0~ 00 09 00 00 I ll~l'llllrhynrlw> "hwm" • I 01 01 00 ()() 00 05 07 OJ 02 04 03 00 05 (l() ()() 'mull rorqual (unodcntilicu 1 7-10 01 00 ()(I ()(I 112 ()4 07 02 04 01 01 ()() 11 00 ()() Ordm11 m·rr.

32-1\0 02 02 04 02 02 0 I 00 02 03 ()~ 05 02 I I 0 I 00 Globir<'J'illla m..ta .. lla .15 02 02 04 02 02 0 I 00 02 03 OH 0~ 02 I I 0 I 00

25 02 02 04 02 02 01 00 02 OJ Ol\ 05 02 11 01 tMI

5 0 I 00 ()(l ()() 02 04 ()() 02 0~ 0 I 0 I 00 08 04 (J(l Orcin m "''""

3 4 OJ 00 00 (1(1 0.\ 02 00 02 0 \ ()() 01 (15 Oli 09 Oil I •N•·norhr11chu< m•ri•t•r OJ Ill 00 Otl 111 02 07 02 0.\ 0'1 Ill 07 08 0.1 Otl Cc•plwl»lnurhu< ff"llllll<'""""

03 01 IKl Otl 01 Ol 00 Ol OJ tW (lJ 00 08 CH I)()

4-5 03 CH 00 lXI 02 04 07 02 U2 05 01 02 05 00 00 1'/wn>l'</11 c/ioptrira·•

I 02 01 00 UO 02 0~ 07 OJ 02 04 01 00 05 00 00 '"'"11 r<>rquul (unidcnioli«l) 01 O.l OJ IXl lJO 04 07 0.1 02 10 OJ 00 06 00 Oil 1'/to•,..,..,. cmmk>11

2 01 01 00 ()0 00 00 07 01 01 OR OJ 00 06 00 00 hnulc no,ed "hale 'J1P· ., 01 02 Ill (J(I 00 00 ()() ()(I ()() 00 00 00 ()() ()(I 00 lurgc \\hale (oonodenoitiedl 01 04 01 ()() ()() ()() 00 OCI tX) ()(I 00 00 00 ()() tKI IJr~c rorqual (unodenrihcdl

l·J 01 Ol ().! 01 00 04 07 ()(l 00 ()() ()() 00 00 ()() (l(l l'hnc·l<'f ratc><I<NI

I 01 OJ 02 ()(I 00 04 07 03 02 10 OJ 00 06 ()(I 00 2 01 03 04 Ill 00 04 07 03 02 10 OJ 00 06 00 ()(l

3 01 01 00 00 00 00 07 03 02 (19 03 00 01\ ()() 00 bc;~l.etl "hak (unidcntilictl)

S. Afr. J. Antarct. Res .. Vol. 6 1976

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llJU"'f FI>\\AUI) ( W.U/U 1" ·- ... ~h.UU;t t:l .• :~

1'1 \!\ll:-1 lh !\'H ~IPS

'U"E ^{4.(t •.} 60'E ltYf.

Fig. I. Cruise track and local noon positions of M.S.

Marion Dufre.\111! during March and April 1976. Solid and dotted lines represent the distance sailed during daylight and

at night respectively.

( 18 500 km) in the southern Indian Ocean, from Reunion to the subantarctic islands of Marion and Prince Edward, and the Crozet and Kerguelen archipelagos. Approximately 4 500 nautical miles were covered during daylight hours. The cruise tracks and local noon positions are given in Frost, Grindley & Wooldridge (in prep.) and an outline of the cruise track is shown in Fig. I.

A total of 252 hours (representing 3 150 nautical miles) of detailed observations was recorded in all weathers during the 45 days at sea. Less intensive watches were kept at other times, either by P.G.H.F. or by the officer-on-watch. A 180° horizontal field of view. usually lateral to the ship"s course, was scanned regularly during each watch. While the primary objective was to record the distribution and abundance of scabirds, a careful watch was kept for any cetaceans. Full details were recorded whenever a sighting was made. How- ever, in most cases it was not possible to alter course to get better views or to clarify doubtful points. Consequently there was a high proportion of incomplete observations.

Thirty-four sightings of a minimum of 205 cetaceans were made during the cruise. Details of these sightings are given in Table I, together with all the descriptive features seen and coded in the proposed format. Details on environmental conditions at the time of the observations can be obtained from P.G.H.F. The most frequently sighted species was the sperm whale, Physl'/er cawdon, which was recorded through- out the area between 25 and 40•s. At least 19 animals were observed in a total of 9 sightings over a track of 1 386 nautical miles between 20° and 40°S and 40° to 65c'E, which cor- responds to an average of about 8 sperm whales per I 000 nautical miles. Densities varied from area to area. so we have calculated the estimated number of sperm whales per I 000 nautical miles for each 5° square (Fig. 2).

The area in which most sperm whales were seen was also surveyed by Gambell er al. (1975) during the period 24 November 1973-J February 1974. 01l that cruise sperm

11

whales were also the most commonly encountered cetacean.

The number of sperm whales seen (57,2 per I 000 n. miles) was many times greater than in 1976 (8.0 per I 000 n. miles). but the number

of

sightings of this species was more comparable.

4,9 per I 000 n. miles in 1973174 and 3.8 per I 000 n. miles in 1976. This suggests either that the schools encountered in 1976 were much smaller on average than in 1973/74, or that there were some differences in interpretation of school sizes from observations. A major difference between the two cruises was that in 1973/74 the vessel attempted to close with each group of whales sighted in order to mark individuals, whereas the Marion Dulresne seldom altered course when cetaceans were seen. The experience of one of us (P.B.B.) has been that an initial contact with sperm whales may only be made as a sighting of one or two individuals but that if time is spent pursuing the animals the total school site will frequently be found to be considerably larger. 11 seems reasonable to assume, therefore, that the school si7cs noted during the Marion Dufi·esne cruise were underestimated.

The greatest densities of sperm whales seen in 1976 oc- curred south of the Malagasy Republic (Fig. 2). The greatest densities of sperm whales recorded by Gambell "' al. ( 1975) were also concentrated on and south of the Madagascar Ridge. During the present cruise a concentration of whales was located in the vicinity of a sea mount 130 nautical miles south of the Malagasy Republic. Sperm whales feed largely on cephalopods, so that it is possible such a distribution pattern reflects a concentration over the feeding grounds on mid-ocean sea mounts or ridges where food could be either more abundant or more available.

The next two most frequently observed cetaceans on the 1976 cruise were 'large whales' and small whales or dolphins, there being 10 sightings of each (excluding killer whales). A similar situation occurred in 1973/74, where the most fre- quently seen cetaceans apart from sperm whales were dol- phins (37 sightings) and large whales (34 sightings). The relative proportions of sperm, large whale, and dolphin sightings were almost identical on the two cruises. Far fewer dolphin or large whale species were identified in 1976. as a result of the inexperience of the observer and the failure of the Marion Duji·esne to close with most cetaceans when seen.

However, the coded information does allow some distinctions to be made, for example, between those whales with a dis- tinct blow and those without: only one sighting was recorded as having a tall columnar blow. indicating the rarity of large

rorqual~ in the area.

g~;·r WE 15 E iiO I. :l:; 1·. loO F.

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u.mi. "lwrm ... tilj•tl "n'JI

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Fig. 2. Number of nau1ical miles sailed during daylight hours (figure in lo\\er left corners). total number of sperm whales seen (IO\\er righ1 figure), and es1ima1ed densi1y per I 000 nautical miles (figure in centre of squares), calculated

for 5 squares between 20 40 S.

10 S. Afr. T. Antarkt. Nav .. Deel 6, 1976

species. Therefore any method of recording Information should ensure that the most useful identifying features arc looked for preferentially and are recorded in a standard and systematic manner. without resorting to a dichotomous or other key.

character seen will therefore be recorded as a set of four numerals. the first two of which designate the character and the latter two the particular character state. A full sighting would consist of a series of these enumerated sets.

We ha'e tried to make the choice of altcrnati\e character states as comprehensive as practical. but for certain character:.

the choice of detailed alternatives is so large that it is impractical to include them. Hence we opted for the inclusion of those characters which are of greatest use in aiding the identification of' a particular group of species. For example, we have divided colour patterns into broad categories of pattern type. rather than attempted to describe separately all the distinct but subtle variations that e"\ist. While the latter would certainly facilitate positive identification of many species, it is not our intention to construct an identification 1-ey (which might well lead to misleading identifications). but rather to ensure that the greatest amount of useful infor- mation is recorded for each sighting.

The purpose of this paper is to present the details of such a system, and to demonstrate its applicability to a series of hitherto unpublished observations made by one of us (who was inexperienced in cetacean identification) in the south- western Indian Ocean during March and April 1976.

Method

We have compiled a list of the most obvious and frequently seen characters for those cetaceans previously recorded from the southern Indian Ocean. Most of these characters are key features in the identification of species. Each character is coded numerically to facilitate recording the observation in

a

concise manner. The characters arc: Each sighting should be accompanied by standard details such as date and time of observation, exact position (latitude and longitude), number seen, estimated site of the animals, and adult to juvenile ratios if possible. In addition the minimal environmental data required arc sea surface tempera- ture. sea state (or wind speed), cloud cover and visibility. Any associated organisms, such as flocks of scabirds or other cctaccan species. should be recorded. Sketches or photo- graphs of animals seen can provide valuable supplementary evidence of identity, and should be included whenever possible.

01. Body size class 02. Blow shape 03. Blow frequency

04. Blow synchronisation within group 05. Swimming behaviour

06. Reaction to vessel

07. Exposure of tail flukes or flipper (apart from jumps) 08. Dorsal fin position

09. Dorsal fin height 10. Dorsal tin shape (Fig. 3)

11. Colour of dorsal fin and back just behind fin

Application

12. Head shape

13. General body colour 14. General colour pattern 15. Flipper shape and colour

Each of these characters has been divided into a number of character states which are also coded (Appendix I). Each

In order to test the feasibility of this method we have applied the coding system to a series of observations made by one of us (P.G.H.F.) during cruise MOOS of the research ship M.S. Mm·ion Du/resne from 8 March to 26 April 1976. The cruise tracks covered approximately 10 000 nautical mile!>

Dnte Time (b) 10-03-76 1245 12·03-76 1815

13~3-76 0745 0753 1335 1600 1650 1735 14·03-76 0845 1358 1844

~~~3-76 0836 1305 1530 20-0J-76 0817 24·03-76 1130 25-03-76 1750 26·0.1-76 0650 1045 29-03-76 1430 31-03-76 0935 1-04-76 1015 l-04-71\ 1400 1430

183~

1840 5-04-76 07 30 1450 6-04-76 1743 7-04-76 0910 0915 10-04-76 0745 0930 11-04-76 1345

La1.

28 OS'S 28 07'S 27 49'S 27 49'S 21 42·s 21 39·s 27'4J'S 27' 44'S 21· 42·s 28 29·s 29 30'S 30 24·-;

31 25

s

31 5~'S

41 06'S 46 40'S 46 ~I'S

46 4o·s 4(• 4s·s 46 4o·s 45 5'1 s

47 411 s 49 +Is 49 4~ s 49 2<1 s 4'1 29·s J6 45·s 35 16'S 2S WS 25 03 s 25 03'S 26 21"S 2(> 45 s .n 21 s

Table I

Sightings of cetaccuns in ,ourthen Indian Occun March-Aprit 1976. S1.-c tc\t tor furrher detaob Long.

SS 15'E 51 54'E 48 18'E 48< 19'F 46'46'E 46°2l"E 46'27'E 46"27'E 46 26'E 46 1s·e 45 s2·E 45 41 E 45 07'E 44 45·e 52 09'E 40 li'E 37 55'E 38 03'E 38 04•E 38 OO'F 50 28"E 58 09·E 6S 42.E 69 00 E 70 15'E 70 lYE 63 ITF 62 27'F 59 05'E 57 20'E s1

2o·e

54 12 E 54 09 E 53 IO'E

Ts (Cl 27.0 28.0 27.2 27.2 28.0 28.0 2g.o 28.0 26.5 27.0 2U 27.0 27 0 27.0 I J.J 7.4 7.1 7.11 7.11 7.1 76 7.ll

~. 1

~.1

~.4

5.4 I').J 22. I 27.1 :!7.2 27.:!

27 I 27.0

22.~

No. ldentilication code lclcntificmion

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15

3 01 03 04 01 00 00 07 03 02 10 03 00 06 00 00 1'/nwtrr catodrm 6- 03 01 00 00 03 00 00 02 03 02 03 00 10 02 00 tlolphon (unidentified) 4 01 0.1 04 01 00 00 07 00 00 00 00 00 00 00 00 Plr.nrtrr rMOlfon

03 00 00 00 01 00 07 02 00 00 00 00 00 00 00 dnltlhin (unidentified) 0 I 0.1 04 0 I 00 00 07 00 00 00 00 00 00 00 00 Plw<t'lt'r C"illodoro 01 03 04 01 00 00 07 03 02 10 O:J 02 06 00 00 l'ho·wrt•r twrodrm 01 07 04 00 00 00 00 00 00 00 00 00 07 00 00 lnrge whak (unidentilictl) 01 02 00 00 00 00 00 00 (XI 00 00 00 00 00 00 lnrgc "hnlc (unidcntilicd) 01 08 02 00 00 00 00 ()() ()() 00 00 00 00 00 00 horge "hale (unidcntilicd) 03 01 00 00 00 00 03 02 00 00 00 00 10 00 ()() tlolllhin (unidentified) OJ 01 ()() ()() 00 00 07 00 00 00 00 00 06 00 00 dolphin (unidentoficd) 01 03 04 00 00 00 00 00 ()() 00 00 00 00 00 00 Phnc·tc•r rmO<Iun 1 01 02 02 00 00 00 00 00 00 00 00 00 00 00 00 larpe "hale (unidentified) 39 03 01 00 00 0.1 04 00 02 03 02 0.1 06 10 06 00 Srnwlfa cO<•rtilrr><uhu

9 03 0 I 00 ()() 0 I 02 07 02 03 03 0~ 00 09 00 00 I ll~l'llllrhynrlw> "hwm" • I 01 01 00 ()() 00 05 07 OJ 02 04 03 00 05 (l() ()() 'mull rorqual (unodcntilicu 1 7-10 01 00 ()(I ()(I 112 ()4 07 02 04 01 01 ()() 11 00 ()() Ordm11 m·rr.

32-1\0 02 02 04 02 02 0 I 00 02 03 ()~ 05 02 I I 0 I 00 Globir<'J'illla m..ta .. lla .15 02 02 04 02 02 0 I 00 02 03 OH 0~ 02 I I 0 I 00

25 02 02 04 02 02 01 00 02 OJ Ol\ 05 02 11 01 tMI

5 0 I 00 ()(l ()() 02 04 ()() 02 0~ 0 I 0 I 00 08 04 (J(l Orcin m "''""

3 4 OJ 00 00 (1(1 0.\ 02 00 02 0 \ ()() 01 (15 Oli 09 Oil I •N•·norhr11chu< m•ri•t•r OJ Ill 00 Otl 111 02 07 02 0.\ 0'1 Ill 07 08 0.1 Otl Cc•plwl»lnurhu< ff"llllll<'""""

03 01 IKl Otl 01 Ol 00 Ol OJ tW (lJ 00 08 CH I)()

4-5 03 CH 00 lXI 02 04 07 02 U2 05 01 02 05 00 00 1'/wn>l'</11 c/ioptrira·•

I 02 01 00 UO 02 0~ 07 OJ 02 04 01 00 05 00 00 '"'"11 r<>rquul (unidcnioli«l) 01 O.l OJ IXl lJO 04 07 0.1 02 10 OJ 00 06 00 Oil 1'/to•,..,..,. cmmk>11

2 01 01 00 ()0 00 00 07 01 01 OR OJ 00 06 00 00 hnulc no,ed "hale 'J1P· ., 01 02 Ill (J(I 00 00 ()() ()(I ()() 00 00 00 ()() ()(I 00 lurgc \\hale (oonodenoitiedl 01 04 01 ()() ()() ()() 00 OCI tX) ()(I 00 00 00 ()() tKI IJr~c rorqual (unodenrihcdl

l·J 01 Ol ().! 01 00 04 07 ()(l 00 ()() ()() 00 00 ()() (l(l l'hnc·l<'f ratc><I<NI

I 01 OJ 02 ()(I 00 04 07 03 02 10 OJ 00 06 ()(I 00 2 01 03 04 Ill 00 04 07 03 02 10 OJ 00 06 00 ()(l

3 01 01 00 00 00 00 07 03 02 (19 03 00 01\ ()() 00 bc;~l.etl "hak (unidcntilictl)

S. Afr. J. Antarct. Res .. Vol. 6 1976

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Fig. I. Cruise track and local noon positions of M.S.

Marion Dufre.\111! during March and April 1976. Solid and dotted lines represent the distance sailed during daylight and

at night respectively.

( 18 500 km) in the southern Indian Ocean, from Reunion to the subantarctic islands of Marion and Prince Edward, and the Crozet and Kerguelen archipelagos. Approximately 4 500 nautical miles were covered during daylight hours. The cruise tracks and local noon positions are given in Frost, Grindley & Wooldridge (in prep.) and an outline of the cruise track is shown in Fig. I.

A total of 252 hours (representing 3 150 nautical miles) of detailed observations was recorded in all weathers during the 45 days at sea. Less intensive watches were kept at other times, either by P.G.H.F. or by the officer-on-watch. A 180° horizontal field of view. usually lateral to the ship"s course, was scanned regularly during each watch. While the primary objective was to record the distribution and abundance of scabirds, a careful watch was kept for any cetaceans. Full details were recorded whenever a sighting was made. How- ever, in most cases it was not possible to alter course to get better views or to clarify doubtful points. Consequently there was a high proportion of incomplete observations.

Thirty-four sightings of a minimum of 205 cetaceans were made during the cruise. Details of these sightings are given in Table I, together with all the descriptive features seen and coded in the proposed format. Details on environmental conditions at the time of the observations can be obtained from P.G.H.F. The most frequently sighted species was the sperm whale, Physl'/er cawdon, which was recorded through- out the area between 25 and 40•s. At least 19 animals were observed in a total of 9 sightings over a track of 1 386 nautical miles between 20° and 40°S and 40° to 65c'E, which cor- responds to an average of about 8 sperm whales per I 000 nautical miles. Densities varied from area to area. so we have calculated the estimated number of sperm whales per I 000 nautical miles for each 5° square (Fig. 2).

The area in which most sperm whales were seen was also surveyed by Gambell er al. (1975) during the period 24 November 1973-J February 1974. 01l that cruise sperm

11

whales were also the most commonly encountered cetacean.

The number of sperm whales seen (57,2 per I 000 n. miles) was many times greater than in 1976 (8.0 per I 000 n. miles). but the number

of

sightings of this species was more comparable.

4,9 per I 000 n. miles in 1973174 and 3.8 per I 000 n. miles in 1976. This suggests either that the schools encountered in 1976 were much smaller on average than in 1973/74, or that there were some differences in interpretation of school sizes from observations. A major difference between the two cruises was that in 1973/74 the vessel attempted to close with each group of whales sighted in order to mark individuals, whereas the Marion Dulresne seldom altered course when cetaceans were seen. The experience of one of us (P.B.B.) has been that an initial contact with sperm whales may only be made as a sighting of one or two individuals but that if time is spent pursuing the animals the total school site will frequently be found to be considerably larger. 11 seems reasonable to assume, therefore, that the school si7cs noted during the Marion Dufi·esne cruise were underestimated.

The greatest densities of sperm whales seen in 1976 oc- curred south of the Malagasy Republic (Fig. 2). The greatest densities of sperm whales recorded by Gambell "' al. ( 1975) were also concentrated on and south of the Madagascar Ridge. During the present cruise a concentration of whales was located in the vicinity of a sea mount 130 nautical miles south of the Malagasy Republic. Sperm whales feed largely on cephalopods, so that it is possible such a distribution pattern reflects a concentration over the feeding grounds on mid-ocean sea mounts or ridges where food could be either more abundant or more available.

The next two most frequently observed cetaceans on the 1976 cruise were 'large whales' and small whales or dolphins, there being 10 sightings of each (excluding killer whales). A similar situation occurred in 1973/74, where the most fre- quently seen cetaceans apart from sperm whales were dol- phins (37 sightings) and large whales (34 sightings). The relative proportions of sperm, large whale, and dolphin sightings were almost identical on the two cruises. Far fewer dolphin or large whale species were identified in 1976. as a result of the inexperience of the observer and the failure of the Marion Duji·esne to close with most cetaceans when seen.

However, the coded information does allow some distinctions to be made, for example, between those whales with a dis- tinct blow and those without: only one sighting was recorded as having a tall columnar blow. indicating the rarity of large

rorqual~ in the area.

g~;·r WE 15 E iiO I. :l:; 1·. loO F.

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Fig. 2. Number of nau1ical miles sailed during daylight hours (figure in lo\\er left corners). total number of sperm whales seen (IO\\er righ1 figure), and es1ima1ed densi1y per I 000 nautical miles (figure in centre of squares), calculated

for 5 squares between 20 40 S.