File type: PDF
Smith JN, Double M, Evans K and Kelly N (2023) Relative abundance of the ‘western’ population of southern right whales (Eubalaena australis) from an aerial survey off southern Australia: Final Report on 2022 survey. Report to the National Environmental Science Program. Murdoch University (Lead organisation).
Aerial surveys of Southern Right Whales were undertaken off the southern Australian coast to monitor the recovery of this Endangered species following 19th and 20th Century whaling. A total 526 whales were sighted: 247 cow-calf pairs, 31 unaccompanied adults and 1 yearling. The ‘western’ population in Australian waters is increasing in size (~5.3% per year based on female/calf pairs and a population estimate of 2675 whales) based on the long-term population trend data. This represents the majority of the Australian population.
There is also evidence of a potential slowing down in the rate of increase of cow/calf pairs in the past 13 years (7.5% in 2009 compared with 5.3% in 2022) and highly fluctuating annual variation in abundance and associated fluctuations in cohort structure. The inter-annual variation in sightings of cow/calf pairs relates to their typically three-year breeding cycle, which can be affected by environmental factors on their foraging grounds. The 2022 surveys recorded the lowest number of unaccompanied animals (males and females without a calf) since 1993, with a particularly notable decline in sightings of unaccompanied animals over the past five years. It is unclear what factors account for the decline.