Relative abundance of the ‘western’ population of southern right whales (Eubalaena australis) from an aerial survey off southern Australia: 2022 survey
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 over the past 13 years (7.5% in 2009 compared to 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.