Oral Presentation- Symposium 12th International Mammalogical Congress

Population demographics of southern right whales in South Australia based on 26 years of seasonal observations (#15)

Claire Charlton 1 , Robert McCauley 1 , Rhianne Ward 1 , Chandra Salgado Kent 1 , Robert Brownell 2 , Stephen Burnell 3
  1. Curtin University, Centre for Marine Science and Technology, Bentley, Western Australia, Australia
  2. Southwest Fisheries Science Center, NOAA Fisheries, California, United States of America
  3. Eubalaena Pty. Ltd., Adelaide, South Australia, Australia

Population demographics of southern right whales (SRWs), Eubalaena australis, were assessed using 26 years of count and photo-identification data. Data were collected annually between 1991 and 2016 at Head of Bight in the Great Australian Bight Commonwealth Marine Reserve. SRWs were distributed within a 15x2km area and 10m water depth. SRWs occupied the site between May and October with maximum abundance between late-July and early-August. Up to 28% of calving females were present in mid-June and up to 61% remained in late September. The mean residence period was 65 days (range 1-99) for calving females and 15 days (range 1-51) for unaccompanied adults. Over the study years, 18-81 female and calf pairs were sighted per day, with a maximum of 172 animals counted on 16/08/2016. The estimated mean rate of increase in total SRWs was 5.5% (SD=2.5, 95%CI=0.03) per annum (1991-2016). The corresponding mean rate of increase for females accompanied by a calf was 4.9% (SD=1.9, 95%CI=0.03). The photo-identification database includes 1,186 non-calf individuals that included 459 reproductive females (providing 471 inter-annual calving intervals). The estimated mean calving interval was 3.3 years (SD=0.8, 95%CI=0.01) with high philopatry resulting in cohort structured breeding cycles and variation in annual abundance. The mean age at first parturition was 9.3 years (SD=2.1 95%CI=0.03, N=22). The mean date of calving was 16 July (range 19 June - 27 Aug). These population demographics and life history parameters provide key information for recovery assessments, species conservation planning and global comparative studies with other right whale populations.