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Smith JN, Double M, Kelly N, Charlton C and Bannister J (2022) Relative abundance of the ‘western’ population of southern right whales from an aerial survey off southern Australia: Final Report on 2021 survey. Report to the National Environmental Science Program. Murdoch University.
Aerial surveys of southern right whales (Eubalaena australis) are undertaken off the southern Australian coast to monitor the recovery of this Endangered species following 19th and 20th Century commercial whaling. The annual surveys are supported by the Marine and Coastal Hub and this report presents the results of the 2021 survey.
The trend in abundance for the ‘western’ southern right whale population is determined using the maximum whale counts for each leg of the survey flights. A total of 643 southern right whales were sighted across the survey area (270 cow-calf pairs and 103 unaccompanied whales). The subsequent population estimate for the Australian ‘south-western’ population is 2,549 whales. This represents the majority of the Australian population, given the very low numbers in the ‘south-eastern’ subpopulation.
Since 2007 the range in population estimates has been more pronounced as the inter-annual variation in whale counts increases. Anomalous years of pronounced low whale numbers are becoming more frequent, with more dynamic cyclical patterns in whale numbers. However, the non-annual breeding cycle of southern right whales makes it difficult to determine whether the anomalous years represent some form of a cycle that females are conforming to as the population recovers or whether changes to their environment are having an effect on their breeding cycle. It is important to collect long-term data on the annual variability in whale numbers related to the non-annual female breeding cycle and identify possible impacts on this by short-term climate dynamics, longer-term climate change and/or anthropogenic threats.