MEMOIRS

OF THE

~ QUEENSLAND MUSEUM

BRISBANE VOLUME 30 1 JULY, 1991 PART 2

Preface

Papers contained in this number of the Memoirs of the Queensland Museum were among those presented at the Humpback Whale Conference hosted by the Queensland Museum in September 1990. Delegates from Australia, Colombia, Japan, New Zealand, South Africa and the United States of America honoured Drs R.G. Chittleborough and W.H. Dawbin, the pioneers of Australasian Humpback Whale research during the last, and probably final, period of exploita- tion of the species in the 1950s and early 1960s. Research initiatives in the post-whaling period have reflected increasing concern not only for Humpback Whales but also for the ecosystem in which they live,

It was particularly appropriate that the official ceremony to acknowledge the display of life size models of Humpback Whales over the front entrance to the Museum was held during the conference and conference delegates were in attendance (see photograph over page).

With the increasing numbers of Humback Whales appearing off the Australian coast, greater understanding ,through the sorts of research reported herein, will be necessary to develop harmony between whales and humans. The growing tourist interest in Humpback Whale activities in Hervey Bay must be accommodated but the interests of the whales must also be considered especially in view of the past decimation of the species wrought by commercial whalers.

The Humpback Whale Conference was most notable for the many different aspects considered by the speakers (photo-id, anatomy, strandings, songs, management, modelling, to name but a few) and this diversity is reflected in the volume that follows despite its containing only a percentage of papers delivered at the conference. The Queensland Museum is proud to have been associated with this meeting of the Humpback fraternity, both as host and as publisher of the proceedings.

Peter A. Jell and Robert A. Paterson Brisbane 10 May 1991.

MEMOIRS

OF THE

(QUEENSLAND MUSEUM

BRISBANE

National Library of Australia card number ISSN 0079-8835

NOTE Papers published in this volume and in all previous volumes of the Afemoirs of the Queensland Museum maybe teproduced for scientific research, individual study or other educational purposes. Properly acknowledged quotations may be made but queries regarding the republication of any papers should be addressed to the Editor in Chief. Copies of the journal can be purchased from the Queensland Museum Shop.

A Guide to Authors is displayed at the Queensland Museum web site

A Queensland Government Project Typeset at the Queensland Museum

POTENTIAL IMPACTS OF CLIMATIC CHANGE ON THE SOUTHERN OCEAN

ECOSYSTEM R.G. CHITTLEBOROUGH

Chittleborough, R.G. 1991 07 Q1: Potential impacts of climatic change on the Southern ocean ecosystem, Mehoirs of the Queensland Museum 30(2):245-247. Brisbane. ISSN 0079-8835.

Global climate change has the potential to disrupt the delicately poised thermal balance in surface waters of the Southern Ocean around Antarctica, threatening this highly productive ecosystem with severe and permanent collapse, Pivotal in this process is a diminution of the important (bul little studied) CO2 sink in the Southern Ocean, resulting in a series of feedback loops accelerating global warming and intensifying impacts upon the Southern Ocean ecosystem.

As well as outlining the processes involved and stressing the urgent need for further research, this paper underlines our wider social responsibilities to press for fresh policies essential Lo arrest the global changes before irreversible harm is done to the Antarctic environment and ecosystems, with {heir global consequences to our life support system.

R.G. Chitleborough, 24 Wau Sc, Swanbourne, Western Australia 6010; 4 January 1991.

The Convention for Conservation of Antarctic Marine Living Resources, (CCAMLR), while “RECOGNISING the importance of safeguard- ing the environment and protecting the integrity af the ecosystem of the seas surrounding An- tarctica’: places its main emphasis on the im- pacts which harvesting may have, not only upon target species but also upon ecalogical relation- ships. Article UI of the Convention also commits us to the conservation principle of “prevention of changes or minimisation of the risk of changes in the marine ecosystem which are not potential- ly reversible over two or three decades...”

However, even if there was no exploitation of living (or mineral) resources in the Antarctic, the environment and ecosystems there are now threatened by accelerating climatic changes being triggered globally by mankind.

Not surprisingly, the main focus of attention presently being given to global climatic change is how the changes will impact on ourselves. We have begun to consider how quickly we may have to adapt in terms of water supply, agricul- ture, forestry, transport. coastal developments, ele, Far less attention is being given to potential impacts upon natural ecosystems, particularly the more remote Antarctic ecosystem.

PROCESSES MAINTAINING THE SOUTHERN OCEAN ECOSYSTEM

The main driving force of this system is the

annual pulse of winter sea ice extending northwards from Antarctica to cover same 20 million square kilometres of the Southern Ocean, retreating each summer almost to the mainland coast. This annual pulse drives the vertical circulation of these waters (Fig. 1), cold brine released by the formation of sea ice sinking along the continental shelf, with compensatory upwelling of nutrient rich water farther offshore at the Antarctic Divergence (Sverdrup et al.,1942). Microalgae growing from the base of the sea ice, and phytoplankton blooms each spring and summer within the nutrient rich An- tarctic Surface Water, are the main basis of the high productivity of the Southern Ocean ecosys- tem (Chittleborough, 1984). Estimates of gross annual production of phytoplankton are 6.1-38 billion tonnes. This represents an annual uptake of 1.5-10 billion tonnes of CO:. Part of that COz is released again during metabolic activity of consumers, but a proportion sinks as detrital organic carbon into Antarctic Bottom Water.

Some dissolved CO: from the atmosphere ts also carried down in both the Antarctic Bottom Water and the Antarctic Intermediate Water sinking at the Antarctic Covergence,

While it is widely accepted that the Southern Ocean is a major sink for CO measurements of the sink are not available. Takahashi (1987) es- timated that the Southern Ocean removes 6,67 billion tonnes of COz per year from the atmos- phere or 70% of total uptake flux of all oceans.

t = HC ba! YS UBZANTARCTIC a — _&-

MEMOIRS OF THE QUEENSLAND MUSEUM

Fig, 1, Representation of currents and waler masses of the Antarclic regions (after Sverdrup et al,, 1942).

THERMAL STABILITY

The advent of satellite sensing affords a prac- tical means of assessing long term variations in thermal stability of the Southern Ocean, Jacka (1983) stressed the importance of monitoring the extent of winter sea ice, as this parameter is likely to be one of the earliest indicators of any significant climatic change.

As satellite images of the winter sea ice around Antarctica became available, extensive open waters within the ice (polynyas) were dis- covered. The largest of these, the “Weddell Polynya” (actually situated to the east of the Weddell Sea) measured 1 L00 x 650 km in Sep- tember 1975. The Weddell Polynya appeared in three consecutive winters, 1974-1976, then dis- appeared until 1980 (Comiso and Gordon, 1987), Farther east at c, 45°E, the Cosmonaut Polynya appeared in 1973,1975, 1979,1982 and 1986, While it is not suggested that these polynyas weré caused by the greenhouse effect, they do serve to illustrate the delicate balance in the formation and maintenance of sea ice.

Rather more information is available on the extent and distribution of residual sea ice during

summer, as this is the time of greatest shipping activity in the Southern Ocean. While much of this information is still to be collated, an analysis by Bentley (1984) indicates that the extent of the Antarctic sea ice in summer decreased by 2.5 million square kilometres. between 1973 and 1980, and perhaps by more since the 1930's.

There is. evidence of a recent increase in air temperature over the Southern Ocean. Budd (1980) recorded an increase in mean annual air temperature at subantarctic islands of 0.4° C during 1958-1978 and by 0.6° C at stations on the edge of the Antarctic continent. At Ker- guelen Island, situated on the northern edge of Antarctic Surface Water, the mean annual air temperature has risen during 1964-1982 by 2.1° C (Jacka, Christou & Cook, 1986), the increase being more marked in summer than in winter. Similar rises in mean annual air temperature are recorded for Amsterdam Island and Marion Is- land,

On glaciated subantarctic islands such as Heard Island, glacial retreat has accelerated dramatically in recent decades (Allison and Keage, 1986). Heard Island, located towards the outer margin of Antarctic Surface Water, and its

CLIMATIC CHANGE IN THE SOUTHERN OCEAN ECOSYSTEM

glaciers moving i ell on steep slopes (short residence time of the ice), affords sensitive in- dicators of changes in climate.

While there is a paucity of hard data on variability within the Southern Ocean region, it is evident from the great changes occurring seasonally and in the longer term, that the ther- mal balance of this region ts delicately poised.

POTENTIAL FOR CHANGE

Global climate models used {o predict surface air temperature changes due to increasing atmos- pheric COz, generally indicate greater increases in temperature at higher latitudes, For example, Rind (1984) indicated that a doubling of atmos- pheric CO: would raise mean annual air temperatures over most of Australia by 44°C, while over the Southern Ocean around An- tarctica increases of 6-8°C could be anticipated. Sea surface temperatures in the Southern Ocean can therefore be expected to rise by a greater amount than in lower latitudes,

The most immediute effect of Souther Occan surface isotherms contracting southwards would be to further restrict the distribution of cold lolerant species living within Antarctic Surface Water. For example, most of the slock of Euphausia superba is confined 10 waters less than 2°C (Marr, 1962), while E. crystallorophias is restricted to waters of even lower temperature. The shrinking range of such key food species will compress dependent consumer species into a narrower band around Antarctica. increasing competition between predators, Around some sub-Antaretic islands, vital food resources may then be beyond the foraging range of adult seals and birds during the critical period of rearing the young. Croxal et al. (1987) showed that this already occurs sporadically al South Georgia.

One of the most far reaching effects of rising sca surface temperatures in the Southern Ocean would be a progressive reduction in the extent of sea ice, both in winter and summer, In an initial modelling of the potential impact upon Southern Ocean sea ice, Parkinson and Bindschadler (1984) concluded that a rise of S°C in air lemperature could result in the winter extent and volume of sea ice to be halved. As the increase in wir temperature at high latitudes is anticipated to continue to rise well beyond that level, the winter extent of sea ice could be reduced even further.

Direct ecological impacts of a reduction in sea ice include loss of substrate for ice ulgae (an

important component of primary production during winter and early spring), and less ice floes suilable for pupping and mating of ice seals (particularly crabeater and leopard seals) at the critical period during late October and carly November each year.

One of the physical effects of a reduction in the extent of sea ice would be a loss of albede and further absorption of solar energy into the surface of the Southern Ocean, accelerating the change in the energy balance.

An even more important feedback loop from a much reduced extent of winter sea ice would be a severe reduction in the pulse driving the vertical circulation of the waters of the Southern Ocean. With Jess sea ice formed, there would be less brine released to sink as Antarctic Bollom Water and hence diminution of the passage of dissolved CQz to be held in the deep ocean sink- With the weakening of the vertical circulation there would also be a decline in compensatory upwelling of nutrient rich water upon which phytoplankton and all higher consumers are to- tally dependent. A failure of phytoplankton blooms would represent a massive reduction im the fixation of COs in Antarctic Surface Water, again feeding back to accelerate global warming.

A severe reduction in primary production within Antarctic Surface Water would have a disastrous impaci on the Southern Ocean ecosys- tem as a whole. including the harvested specics which CCAMLR is allempling to manage and conserve. Furthermore, a diminution of krill stocks through man-induced climate changes would severely retard (or reverse) the recovery of previously depleted populations of blue. fin and humpback whales, negating much of the hard-won ground by the lWC,

Further potential for impact upon the Southern Ocean ecosystem derives from the ultraviolet wavelengths penetrating the ozonc hole now evi- dent in the stratosphere over Antarctica each spring and early summer. Increasing penctration of UY band tnto the sea surface has potential to depress photosynthesis or even to be lethal to the more sensitive species in the phytoplankton. again depressing the productivity of the ecosys~ tem as well as reducing the uptake of aimos- pheric COz Precise field measurements are lacking, but Pittock ct al. (1981) suggested that phytoplankton is surface waters would suffer Sppicctebhe mortality by a reduction of the ozone shield in the range of 16-30%, In October 1985 ozone levels over Antarctica declined by 50% (Ember ¢} a)., 1986), Concencrations of

246 MEMOIRS OF THE QUE

ENSLAND MUSEUM

Excessive

resource consumption

Warmer southern ocean

albedo

Greenhouse gases|

accumulate in troposphere

Warmer carbon troposphere Less phytoplankton

production

Less

Faster rise in atmospheric C02

Less iil less whales Less detrital

upwelling of nutrients

Ozone hole in stratosphere over Antarctica

Less penguins less seals

Eye damage to new-born seals & birds

“UV(B) penetrates surface water

Less Antarctic bottom water

Much reduced ocean sink of CO2

Fig. 2. Potential feedback loops within the Southern Ocean ecosystem resulting from climatic changes.

phytoplankton some tens of metres below the surface may be afforded some protection from UV radiation, but turbulent wind mixing bring- ing these organisms close to the sea surface may well make them more vulnerable.

Of more immediate impact could be the eye damage that the UV band might bring to new- born seals and birds. Particularly vulnerable here would be the pups of crabeater seals, born on ice floes in high latitudes late in October, close to the peak of the ozone hole. Again, direct meas- urements of sensitivity are lacking.

There are many potential feedback loops im- pacting on the Southern Ocean ecosystem from global warming and weakening of the ozone shield (Fig.2). Even if subsequent research finds that one or two of these processes are of relative- ly minor extent, the overall prognosis for the Southern Ocean ecosystem is extremely poor. Furthermore, the collapse of the important Southern Ocean COz sink has global implica- tions, greatly accelerating the rates of climate change that each of us will have to face.

It should be noted that other feedback systems in the Antarctic, not directly relating to the Southern Ocean ecosystem, but having potential

to affect global climate change, are not discussed here. These include acceleration of break-up from the fringes of the Antarctic glacial ice sheet, and a weakening circulation of the Southern Ocean triggering a permanent ENSO phen- omenon. As stressed by Thomas (1984) “we cannot rule out the possibility that a climate change of magnitude predicted for CO2 doubling could radically alter ocean circulation”. In par- ticular, he points out that if the relatively warmer Circumpolar Deep Water is able to reach the major ice shelves without considerable cooling, ice shelves could thin enough for massively en- hanced calving. “Clearly”, he concluded, “we need to learn more about ocean behaviour neat Antarctica.”

CONCLUSION

There can be little doubt that the Southern Ocean ecosystem is threatened with severe and permanent collapse as a result of impending climatic changes. Such a collapse would halt the present recovery of humpback whale popula- tions.

As scientists, we can design fascinating

CLIMATIC CHANGE IN THE SOUTHERN OCEAN ECOSYSTEM

studies of the physical and biological impacts upon the Antarctic environment as global climatic changes progress. But do we not also have a wider responsibility to press for policy changes aimed at arresting the global processes before irreversible harm is done to the Antarctic environment and ecosystems? Alihough it is quite evident that we need far more research in this area, we can hardly afford to regard the Southern Ocean as a giant experimental unit if we are likely to lose control of the experiment.

Our role should be far more than the gathering of information. We would be failing in our social responsibilities if we do not make a clear state- ment on the urgent need for action to circumvent the setting up in the Southern Ocean of irre- versible processes having high potential to cause massive environmental and ecological changes around Antarctica, as well as greatly accelerat- ing changes in climate (and sea level) throughout the world,

Unless we act quickly and decisively, the conservation strategies presently being pursued by Australia within the WC, CCAMLR and the Antarctic Treaty itself, become meaningless ges- (ures. As stated recently by Dr Noel Brown of UNEP, the next decade is our last window of opportunity to make effective changes. Let’s use that time to the full.

LITERATURE CITED

ALLISON, I.F. AND KEAGE, P.L. 1986. Recent changes in the glaciers of Heard Island. Polar Record 23 (144); 255-271.

BENTLEY, C.R. 1984. Some aspects of the cryo- sphere and its role in climatic change. Geophysi- cal Monographs 29: 207-220.

BUDD, W.-F. 1980. The importance of the polar regions for the atmospheric carbon dioxide con- centrations, 115-128. In G.l. Pearman (ed.), ‘Carbon Dioxide and climate,’ (Australian Academy of Science; Canberra),

CHITTLEBOROUGH, R.G. 1984, Nature, extent and management of Antaractic living resources, 135-161. In §. Harris, ed.. ‘Australia’s An- tarctic Policy Options’, Centre for Resource and

Environmental Studies, ANU Mon. 11; 135- 161.

COMISQ, I.C. AND GORDON, A.L. 1987. Recur- ting polynyas over the Cosmonaut Sea and Maud Rise. J. Geophys. Res, 92; 2819-2833,

CROXALL, J.P. et al. 1987. Reproductive perfor- mance of seabirds and seals at South Georgia and Signy Island, South Orkney Islands, 1976-1987: implications for Southem Qcean monitoring studies. SC-CAMLR. Selected Scientific Papers 1987: 445-447,

EMBER, L.R. et al. 1986, Tending global commons. Chemical & Engineering News 64 (47): 14-64.

JACKA, T.H, 1983, A computer data base for An- larclic sea ice extent, ANARE Research Notes 13: 1-54.

JACKA, T.H., CHRISTOQU, L. AND COOK, B.F. 1984. A data bank of mean monthly and annual surface temperatures for Antaretica, the Southern Ocean and South Pacific Ocean, ANARE Research Notes 22: 1-97.

MARR, J.W,S. 1962. The natural history and geog- raphy of the Antarctic krill (Euphausia superba Dana). Discovery Reports 32; 37-463.

PARKINSON, C.L. AND BINDSCHADLER, R.A. 1984, Response of Antarctic sea ice to uniform atmospheric increases, Geophysical Mono- graphs 29; 254-264.

PITTOCK, A.B. et al. 1981. Human impact on the global atmosphere: impacts for Australia, Search 12; 260-272,

RIND, D_ 1984. Global climate in the 21st. Century. Ambio 13: 148-151.

SVERDRUP, H-V_etal. 1942. ‘The oceans’ .(Prentice hall: N.Y).

TAKAHASHI, T, 1987, Assessment of seasonal and geographic variability in CO2 sinks and sources in the ocean, In Reichle, D.E. et al., ‘Environ- mental Sciences Div. Ann. Progr, Rep. for period ending Sept, 30 1986", (Oak Ridge Na- lional Lab.: Tennessee).

THOMAS, R.H. 1984. Responses of the polar ice sheets to climatic warming. 301-316. In ‘Glaciers, ice sheets and sea level: effects of a C0o-induced climatic change. Report to U.S. Dept. of Energy. DoB/ER/60235-1.

MEMOIRS

OF THE

(QUEENSLAND MUSEUM

BRISBANE

National Library of Australia card number ISSN 0079-8835

NOTE Papers published in this volume and in all previous volumes of the Afemoirs of the Queensland Museum maybe teproduced for scientific research, individual study or other educational purposes. Properly acknowledged quotations may be made but queries regarding the republication of any papers should be addressed to the Editor in Chief. Copies of the journal can be purchased from the Queensland Museum Shop.

A Guide to Authors is displayed at the Queensland Museum web site

A Queensland Government Project Typeset at the Queensland Museum

HUMPBACK WHALE SONGS ALONG THE COAST OF WESTERN AUSTRALIA AND SOME COMPARISON WITH EAST COAST SONGS

WILLIAM H. DAWBIN AND ELIZABETH J_EYRE

Dawbin, W.H. and Eyre, E.J, 1991 07 01; Humpback Whale songs along the coasi of Western Australia and some comparison wilh east coast songs, Memoirs of the Queenslana Museum 30(2): 249-254, Brisbane. ISSN 0079-8835.

Humpback Whale songs have been recorded since 1986 off Western Australia. These songs share nu themes with those recorded off eastern Australia, supporting other evidence that the two breeding stocks are separate despite Some overlap in Antarctic feeding areas.

William H, Dawbin, Australian Museum, 6-8 College Street, Sydney, New South Wales, 2000, Elizabeth]. Eyre, 16/83-85 Alfred Street, Ramsgate Beach, New South Wales 2217;

27 March 1997,

Humpback whales regularly migrate along continental coastlines in the Southern Hemi- sphere (Dawbin, 1966), and produce complex songs (Payne and McVay, 1971) which change over time (Payne et al,, 1983). To date most detailed studies refer to Northern Hemisphere stocks. This report describes the results of studies from the west coast of Australia which began in 1986, together with comparison with data collected from the east coast in 1989

Studies of populations of humpbacks in the Northern Hemisphere have shawn that songs are similar within oceans, but differ significantly where oceans are isolated by a land mass (Payne and Guinee, 1983 ; Winn et al., 1981). The Australian populations of Areas TV and V also exhibit major differences from each other in song length and content.

Evolution of songs can he a gradual or rapid process, with songs changing not only from year to year, but also within the year, as the whales migrate to and from the breeding grounds,

This paper will examine some of the song changes that have occurred amongst the Area IV Feet during 1986-1989, with recent data rom 1990 included. Recordings from the cast coast will be examined briefly for comparison between populations.

METHODS

Equipment used was a Clevite Ordnance Oyster hydrophone (CH-15) with 30 m of cable, a preamplifier and a Sony WMD6 cassette re- corder. Recordings used for analysis were made during the migration period from Dampier (20° 39°S, 116° 45°E) to Rottnest Island (32° 00°S, 115° 30°B), Other recordings have been made

along the west coast from its northern most to southern most extremities (Dawbin and Gill, this memoir). Spectrograms of the songs and shart hand use of descriptive words for each sound were incorporated for song analysis. The spectrograms were traced for the purposes of this report to eliminate background noise and enable clearer definition of song units,

Themes. were numbered by allocating the last theme as that which included sounds which were nearest in character to the “surface ratchet” described by Winn et al. (1971). As songs may differ between singers, comparisons here are made on what are regarded as representative song samples.

Table 1, demonstrating song change, uses methods as described by Helweg et al. (1990). The Western Australian 1956 song is used as a reference, with each theme: occurring after the

surface ratchet labelled successively from A to

E. Themes from following years which cor- respond to any of those in 1986 fall into A to E. but new themes are given subsequent new letters.

RESULTS

The song changed in the first theme from 1986 to 1988 and 1990 (Fig. 1), Between the 1986 and 1987 songs there was substantial change, with little similarity between themes. In 1988 there was substantial change from the 1987 song rep- ertoire. From 1988 onwards, however, the arran- gements of sounds within themes became more similar, with only slight progressive change be- tween units of sound from 1988 to 1990,

The change in song from 1986 to 1987 was not as great as it Was from 1987 (o 1988 (Table 1). The number of themes remained the same over

MEMOIRS OF THE QUEENSLAND MUSEUM

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251

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MEMOIRS OF THE QUEENSLAND MUSEUM

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HUMPBACK WHALE SONGS, WA,

1986 and 1987 and then decreased from 5 to 4 in 1988 (Table 1). The song remained stable during 1988 and 1989, and then in 1990 two themes were incorporated into one, dropping the theme number from 4 to 3.

For further comparison, Fig. 2 shows the last theme from the year 1989, and Fig. 3 the first theme from the same year. Both northern and southern migration songs are represented from Western Australia and these resemble each other, These first and last themes of 1989 resemble the first and last themes of 1988 and 1990 (Fee 1).

TABLE |, Repeated and new themes over five years on the west coast and wcomparison with one year from the east coast of Australia. The 1990 song consists of three themes, but the first theme is actually an incor- poration of the first and second theme from 1958 and 1989.

‘The east and west coast show no similarity in song content. The 1989 Hervey Bay sample has no shared themes with the west from any years {Table 1). There is no similarity between cousts in song elements in the first and last themes during 1989 (Figs 2,3). This contrasts with the sharing of at leastsome themes between Hawaii, Mexico and Bonin Islands (Helweg etal., 1990), Evidence from “Discovery” marks indicates that two animals marked off eastern Australia were killed off Western Australia (Chitleborough, 1965) but acoustic data from the present study

to wa ye}

suggest a high degree of independence between east and west coast breeding stocks,

DISCUSSION

Song change can occur on many levels. Recordings from both coasts of Australia have shown that the content and structure of a song may change between years or within years during the northern and southern migrations. There can also be differences between individual singers and each song rendition of an individual. Change can occur either suddenly or progres- sively, and even within the songs themselves there can be different rates of evolution.

Recordings from east and west show that little or progressive change tends to occur in the last and first theme, and that the majority of change occurs in the ‘body’ of the song. Therefore gradual change is more likely to happen at the end or beginning, with more rapid change taking place in the middle. This rapid change was seen in the middle themes from 1986 and 1987, with the first and last themes evolving at a slower rate. In contrast, a slower change from 1988 to 1990) occurred during the whole song, with some themes not changing at all.

Recordings were made during migration as opposed to on the breeding grounds. This is a difficult environment to record in, as the whales are in transit on active migration, and weather conditions are more frequently unfavourable. This enabled only a small sample of song to be collected each year, and the identification and subsequent resighting of individual singers was virtually impossible.

Our studies have shown, however, that Australian Humpback Whale song differs be- tween the west and east coast and that these songs change over time. The variability in song and the different rates it can occur at have been presented here, but what determines the rate of change remains unknown.

ACKNOWLEDGEMENTS

Thanks go to Chris Burton, Robert Mannell, Hec Goodall and the siaff at The Pet Porpoisc Pool, Ross Isaacs and Peter Gill. This project has received financial support from a Marine Sciences and Technology Research Grant to Dawbin and Cato. Discussions with Dr. Doug Cato have been helpful and much appreciated, The N.S.W, National Parks and Wildlife Service

254

have provided valuable vessel support for sound recording.

LITERATURE CITED

CHITTLEBOROUGH, R.G. 1965. Dynamics of two populations of the Humpback Whale Megaptera novaeangliae (Borowski). Aust. J. Mar. Freshw. Res. 16: 33-128.

DAWBIN, W.H. 1966. The seasonal migratory cycle of Humpback Whales. 145-170. In K.S. Norris (ed.), ‘Whales, dolphins and porpoises’, (Univ. Calif. Press: Berkeley).

DAWBIN, W.H. AND GILL, P.C. this memoir. Humpback Whale survey along the west coast of Australia: a comparison of visual and acoustic observations. Mem. Qd Mus. 30(2): 255-257.

HELWEG, D.A., HERMAN, L.M., YAMAMOTO, S. AND FORRESTALL, P.H. 1990, Com- parison of songs of Humpback Whales (Megap- tera novaeangliae) recorded in Japan, Hawaii and Mexico during the winter of 1989. Sci. ‘Repts. Cetacean Res. 1: 1-20.

PAYNE, K., TYACK, P. AND PAYNE, R. 1983. Progressive changes in the songs of the

MEMOIRS OF THE QUEENSLAND MUSEUM

Humpback Whales (Megaptera novaeangliae): A detailed analysis of two seasons in Hawaii, 9-57. In R. Payne (ed.), ‘Communciation and behaviour of whales’, (Westview Press: Boulder), F

PAYNE, R.S. AND McVAY, S. 1971. Songs of Humpback Whales. Science 173: 585-597.

PAYNE, R. AND GUINEE, L. 1983, Humpback Whale (Megaptera novaeangliae) songs as an indicator of “stocks”, 333-359. In R. Payne (ed.), ‘Communication and behaviour of whales’. (Westview Press: Boulder).

THOMPSON, T.J., WINN, H.E. AND PERKINS, P.J. 1979. Mysticete Sounds, 403-431. In H.E. Winn and B. Olla (eds), ‘Behaviour of marine mam- mals, vol. 3: Cetaceans. (Plenum Press: New York).

WINN, H.E., THOMPSON, T.J., CUMMINGS, W.C., HAIN, J.. HUDNALL, J.. HAYS, H. AND STEINER, W.W. 1981. Song of the Humpback Whale - population comparisons. Behavioural Ecology and Sociobiology 8: 41- 46,

MEMOIRS

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BRISBANE

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HUMPBACK WHALE SURVEY ALONG THE WEST COAST OF AUSTRALIA: A COMPARISON OF VISUAL AND ACOUSTIC OBSERVATIONS

WILLIAM H. DAWBIN AND PETER C GILL

Dawbin, W.H. and Gill, PC. 1991:07:01; Humpback whale survey along the wes! coast of Australia: a comparison of visual and acoustic observations. Memoirs of the Queensland Museum 30(2): 255-257. Brisbane. ISSN 0079 8835.

The results of asurvey of humpback whales, using visual and acoustic delection techniques, along the Western Australian coast during the winter and spring of 1989 are reparted-

William H. Dawbin, Australian Museum, 6-8 College Sireet, Sydney, N.S.W, 2000; Peter C. Gill, Oceanic Research Foundation, PO Box 247, Windsor, New South Wales 2756; 10)

January, 199),

The migratory cycle of humpback whales (Dawbin,1966), and the population charac- teristics of Area [TV humpbacks (Chittle- borough, 1965) and their increase in abundance in Area IV since exploitation ceased in 1962 (Bannister,1990) are well known. Less well studied is distribution of Area IV animals off Western Australia, when they congregate in Warm inshore waters to breed. This study was conducted from a 20m schooner, the R/V ~Thistlethwayte”, while on a circumnavigation of Australia during the austral winter and spring of 1989, The voyage allowed a survey of inshore waters along the Western Australian coast during the humpback breeding season,

Acoustic and visual detection of whales has been used to determine migration routes, Folkow. and Blix (1990) detected several species during a sound survey of the mid-Atlantic, while Clapham and Mattila (1990) detected humpback song at sca in the western Atlantic, distant {rom land, Studies of humpback song on breeding grounds elsewhere are well known and too numerous to list here, but humpback sounds are known to be indicators of stock identity (Payne and Guince, 1983), and songs from Western Australia have been shown to differ from those on the east coast (Dawbin and Eyre, this mem- oir), WHD and Chris Burton have recorded humpback sounds in various latitudes off the Western Australian coast, as far south as Cape Leeuwin (34° 20'S). It was therefore decided to use acoustic and visual observations to monitor humpbacks during the southward passage.

The vessel left Darwin in mid July 1989, and sound samples were taken at intervals of no more \han four hours, navigation and weather permit- ting, while at sea. The vessel stayed as clase ta {he coast as was navigationally prudent. On July

24, humpbacks were first encountered visually and acoustically at 15° 17'S, 123° 52'E. This was considerably further north than the generally accepted limits of Area TV breeding grounds (Harrison and Bryden, 1988), though fisherfolk familiar with these walers laler reported thal humpbacks are commonly seen in the area (P.Canney, pers.comm.), We regarded our timing as favourable, because the majorily of whales are still moving north al this time.

Sound was monitored over 33 days al more than 100 stations, with 92 stations between the first and last recordings; stations spanned 15° of latitude and 1600 nautical miles. Generally the weather was calmer north of Broome, with fre- quent short spells of bad weather to the south.

Sightings and sound recordings were made as faras 30° 24’S, with animals being detected three limes as often by sound as by sight, A total of 40 humpbacks were sighted on 21 occasions, and a conservalive total af 127 heard on 64 occasions. Conservative, because when more than one animal was singing faintly, it was often difficult to distinguish how many were singing. In these cases, the minimum definite number was recorded, Animals were heard singing af all times of the day and night. Humpback sounds typically consisted of a “chorus” of several animals singing the same song, apparently inde- pendently of cach other. Occasionally “social” (non-song) sounds were heard, often during ab- served vigorous displays of social behaviour, as described by Silber re). Only at 23 (25%) slalions were no Whales detected at all. In 13 of these, detection may have been hampered by surface waves (sound), or by darkness or whitecaps (sight).

Dawbin (1956) discussed factors affecting the coastal migration routes of humpbacks. To these

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FIG. 1. Map of Western Australia, showing numbers and locations of humpback whales located during the survey. Animals detected by sound alone are denoted by a plain number; those detected visually are denoted by acircled number. This does not mean that the sightings and soundings are mutually exclusive; sound was often detected during sightings. Not all monitoring stations are shown.

we must add consideration of the possible effects | and which may even have resulted in a localised of large-scale offshore oil and gas development. modification of the humpback migration path. Gas rigs in the vicinity of Barrow Island created Bowhead whales in the Beaufort Sea have shown mechanical underwater noise levels which avoidance behaviours in reponse to oil explora- would certainly hinder cetaceancommunication, _ tion and drilling (Richardson et al.,1985,1986).

ACOUSTIC AND VISUAL HUMPBACK SURVEY, W.A.

The extent of Area IV humpback breeding grounds is still undetermined. Townsend (1935) showed that humpbacks were taken off the northwest coast, west of Broome. In this study, almost all of the animals observed south of Broome were travelling in a northward direction, while animals to the north of Broome were generally static. Two cows with young calves were seen north of Broome, a town previously tegarded as the extreme northern limit of the breeding area: these were the only calves seen during the survey. This indicates a wide latitudinal range in which humpbacks may calve: parturition has been reported as far south as Albany, at 35°S (Chittleborough, 1965). Water temperatures and depth profiles north of Broome are comparable to those of humpback breeding areas in the West Indies (Whitehead and Moore,1982). Animals apparently engaged in courtship were also observed north of Broome.

Visual monitoring would have indicated only 1/3 the whales detected by hydrophone. This is despite the fact that Humpback songs are re- garded as being almost exclusively produced by males. Past catch records indicate that females occur in almost equal abundance off W.A.

Acoustic monitoring has the advantage of being able to operate in darkness or reduced visibility; even in reasonable conditions whales may evade visual detection where they are not expected. In 1986 WHD recorded humpback sounds off Rottnest Island near Perth, when there had been no visual reports for many years. The combined results of this survey, and earlier sur- veys by WHD and Chris Burton show that humpbacks vocalise, and can therefore be monitored acoustically, along the Western Australian coast between 15-34°S.

ACKNOWLEDGEMENTS

Special thanks to the crew of the “Thistleth- wayte’ for their enthusiastic help during the sur- vey. Thanks also to Pam Canney and Ian Lew of F/V “Rachel” in Broome, for their hospitality and valuable information about humpback sight- ings. Financial assistance was providedby a Marine Sciences and Technology Research Grant, and by a grant from the Australian Whale Conservation Society

LITERATURE CITED

BANNISTER,J.L., KIRKWOOD,G.P. AND WAYTE,S.E. 1990. Population increase in

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“Group IV” humpback whales, Western Australia. SC-[WC/42/PSI,

CHITTLEBOROUGH,R.G. 1965. Dynamics of two populations of the humpback whale, Megaptera novaeangliae (Borowski). Aust. J. Mar. Freshw. Res.16: 33-128.

CLAPHAM,P.J. AND MATTILA,D.K. 1990. Humpback whale songs as indicators of migra- tion routes. Marine Mammal Science 6(2): 155— 160.

DAWBIN, W.H. 1956. The migrations of humpback whales which pass the New Zealand coast. Trans. R. Soc. N.Z. 84:147-196.

DAWBIN, W.H. 1966. The seasonal migratory cycle of Humpback Whales. 145-170. In K.S. Norris, (ed.), ‘Whales, dolphins and porpoises’, (Univ. of California Press: Berkeley).

DAWBIN, W.H. AND EYRE, E.J. this memoir. Humpback Whale songs along the coast of Western Australia and some comparison with east coast songs.Mem, Qd Mus.30(2):249-254,

FOLKOW,L.P. AND BLIX,A.S. 1990. Norwegian whale sighting and acoustic surveys in the At- lantic Ocean during the winter of 1989-90. IWCSC/42/06.

HARRISON,R. AND BRYDEN,M.M.(eds) 1988. ‘Whales, dolphins and porpoises’. (Golden Press: Silverwater).

PAYNE,R. AND GUINEE,L.N. 1983. Humpback Whale (Megaptera novaeangliae) songs as an indicator of “stocks”. 333-359. In R.Payne, ed., ‘Communication and Behaviour of Whales’. (Westview Press: Boulder).

RICHARDSON,W.J., FRAKER,M.A., WURSIG,B., AND WELLS,R.S. 1985. Behaviour of bowhead whales, Balaena mysticetus, summer- ing in the Beaufort Sea: reactions to industrial activities. Biol.Conserv.32, 195-230.

RICHARDSON,W.J., WURSIG,B. AND GREENE, C.R. 1986. Reactions of bowhead whales, Balaena mysticetus, to seismic exploration in the Beaufort Sea. J. Acoust. Soc. Am. 79(4), 1117-1128.

SILBER, G.K. 1986. The relationship of social vocalisations to surface behaviour and aggres-