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.

本研究针对南露脊鲸（southern right whale，Eubalaena australis）开展澳大利亚南部近岸航空调查（aerial survey），以监测该濒危物种在19至20世纪遭受大规模商业捕鲸后的种群恢复情况。本次航空调查于2022年8月12日至19日期间开展，覆盖范围为澳大利亚西澳大利亚州珀斯至南澳大利亚州塞杜纳的近岸海域，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。本次调查共记录到526头南露脊鲸，其中包括247头母幼对（cow-calf pairs）、31头单独成年个体以及1头1龄幼鲸（yearling）。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（该增长率基于母幼对数据得出，当前种群估计数量为2675头）。鉴于"东部种群"的数量极低，该西部种群占据了澳大利亚海域南露脊鲸种群的绝大多数。2022年的调查记录到的单独个体（即无幼崽陪伴的雌雄成体）数量，为1993年以来年度航空调查时间序列中的最低值——1993年首次开展了卢因角至塞杜纳海域的调查覆盖工作。在该时间序列中，过去五年间单独个体的目击记录呈现尤为显著的下降趋势。目前尚不明确何种因素导致了此次目击数量的下降，亦或何种因素会影响澳大利亚南部近岸单独个体数量的波动。长期监测数据中低于预期的种群数量记录，或可表明种群增长率正在放缓，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。