Abstract
Southern right whales (Eubalaena australis) migrate between Austral-winter calving and socialising grounds to offshore mid- to high latitude Austral-summer feeding grounds. In Australasia, winter calving grounds used by southern right whales extend from Western Australia across southern Australia to the New Zealand sub-Antarctic Islands. During the Austral-summer these whales are thought to migrate away from coastal waters to feed, but the location of these feeding grounds is only inferred from historical whaling data. We present new information on the satellite derived offshore migratory movements of six southern right whales from Australasian wintering grounds. Two whales were tagged at the Auckland Islands, New Zealand, and the remaining four at Australian wintering grounds, one at Pirates Bay, Tasmania, and three at Head of Bight, South Australia. The six whales were tracked for an average of 78.5 days (range: 29 to 150) with average individual distance of 38 km per day (range: 20 to 61 km). The length of individually derived tracks ranged from 645–6,381 km. Three likely foraging grounds were identified: south-west Western Australia, the Subtropical Front, and Antarctic waters, with the Subtropical Front appearing to be a feeding ground for both New Zealand and Australian southern right whales. In contrast, the individual tagged in Tasmania, from a sub-population that is not showing evidence of post-whaling recovery, displayed a distinct movement pattern to much higher latitude waters, potentially reflecting a different foraging strategy. Variable population growth rates between wintering grounds in Australasia could reflect fidelity to different quality feeding grounds. Unlike some species of baleen whale populations that show movement along migratory corridors, the new satellite tracking data presented here indicate variability in the migratory pathways taken by southern right whales from Australia and New Zealand, as well as differences in potential Austral summer foraging grounds.
Highlights
Baleen whales undertake annual migrations between productive feeding grounds and sheltered calving grounds [1,2,3]
No transmissions were received from a fourth tag until 39 days after deployment at which point the whale was south of the Western Australia and, the tag transmitted for 22 days, there was insufficient data to interpolate a track suitable to be included in analyses
Latitudes associated with the Subtropical Front (STF) (39 ̊–42 ̊S) appear to be a feeding ground for both New Zealand and Australian southern right whales
Summary
Baleen whales undertake annual migrations between productive feeding grounds and sheltered calving grounds [1,2,3]. In Australia, the post-whaling recovery rate of southern right whales is markedly higher in the southwest (i.e., West Australia and western parts of South Australia) than in the southeast (i.e., eastern parts of South Australia, Tasmania, Victoria and New South Wales). This difference, as well as evidence of genetic substructure, has led to southern right whales in Australia being considered as two sub-populations or management units—southwest (SWA) and the southeast (SEA) Australia with the boundary between the two sub-populations at approximately 140 ̊E [18]
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