2022 Aerial survey data of southern right whales (Eubalaena australis) off southern Australia (NESP MaC 2.7)

Aerial surveys of southern right whales (Eubalaena australis) were undertaken off the southern Australian coast to monitor the recovery of this endangered species following extreme 19th and 20th Century commercial whaling. The aerial survey was undertaken in the coastal waters from Perth (Western Australia) to Ceduna (South Australia) between the 12th and 19th August 2022, to maintain the annual series of surveys and inform the long-term population trend. The survey resulted in a total 526 whales sighted, consisting of 247 cow-calf pairs, 31 unaccompanied adults and 1 yearling. The ‘western’ population of southern right whales 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 from the annual aerial surveys. This represents the majority of the Australian population given the very low numbers in the ‘eastern’ population. The 2022 surveys recorded the lowest number of unaccompanied animals (i.e. males and females without a calf) ever throughout the time-series of the annual aerial surveys since 1993 when survey coverage between Cape Leeuwin and Ceduna first began. Across this time series, there is a particularly notable decline in sightings of unaccompanied animals over the past five years. It is currently unclear what factors account for the decline in these sightings or may influence the variation in numbers of unaccompanied animals on the southern Australian coast. Lower than expected counts in the long-term data may provide evidence of a slowing population growth rate, which can only be assessed by continued annual population surveys to assess population trend data.为监测19、20世纪极端商业捕鲸活动后濒危物种南露脊鲸（Eubalaena australis）的种群恢复情况，研究团队在澳大利亚南部近海水域开展了南露脊鲸航空调查。本次航空调查于2022年8月12日至19日期间，在西澳大利亚州珀斯至南澳大利亚州塞杜纳的近海水域实施，旨在延续年度调查序列，为种群长期趋势研究提供数据支撑。本次调查共目击526头南露脊鲸，其中包含247头母幼对、31头单独活动的成体以及1头亚成体。基于年度航空调查的长期种群趋势数据，澳大利亚海域的南露脊鲸“西部种群”种群规模正以每年约5.3%的速率增长（依据母幼对数据估算，种群总数为2675头）。鉴于东部种群数量极低，西部种群占澳大利亚南露脊鲸种群的绝大多数。2022年调查记录到的单独活动个体（即无幼崽陪伴的雌雄个体）数量，为1993年卢因角至塞杜纳海域首次开展年度航空调查以来的历史最低值。在该时间序列中，过去五年间单独活动个体的目击数量出现了尤为显著的下降。目前尚不清楚何种因素导致了此次目击数量的下降，或是会影响澳大利亚南部近海单独活动个体的数量波动。长期监测数据中低于预期的目击数量，或可为种群增长率放缓提供佐证，而这一结论仅能通过持续开展年度种群调查以获取种群趋势数据来验证。