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SC/69B/SH/03
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Resource ID
22146
Access
Open
Document Number
SC/69B/SH/03
Full Title
Report of the South African southern right whale aerial surveys 2023
Author
Els Vermeulen, Christopher Wilkinson
Authors Summary
Paper SC/69b/SHxx presents the results of the 2023 aerial surveys to monitor the South African population of southern right whales. With a total of 568 cow-calf pairs counted and photographed, this survey marked a record-breaking number of cows along the South African coast, and demonstrates the continued enormous annaul fluctuation in SRW coastal prevalence in this region. At the same time, the consistent low number of unaccompanied adults reconfirms altered migration patterns of this demographic group. It was confirmed photo-identification data of this survey will be processed in the coming months.
Publisher
IWC
Publication Year
2024
Abstract
Monitoring the recovery of the South African southern right whale (Eubalaena australis) population has been ongoing since 1969 with yearly aerial surveys. These surveys have included a photo-identification element since 1979, providing a continuous dataset spanning 44 years. Over this period, there has been a consistent increase in population size following the cessation of commercial whaling. However, since 2010 there has been a notable decrease in unaccompanied adult sightings, an extension of the typical 3-year reproductive cycle to 4 or 5 years since the same year, and a considerable variation in the number of cow-calf pairs along the South African coastline since 2015.
The 2023 annual photo-identification aerial survey, covering the area between Nature?s Valley to Muizenberg, was flown between 27th September and 3rd October 2023 in a westward direction, with the aim to count all southern right whales and photograph all nursing females as well as individuals with a brindle or grey blaze colouration. A total of 38 hours and 12 minutes were flown in an Airbus AS350 BA helicopter, chartered by Silvercross Helicopters, to complete the survey. Of these, 31 hours and 39 minutes were flown as search effort, and 6 hours and 23 minutes were flown in transit to and from the survey start and endpoints.
The results of the survey revealed a total of 568 cow-calf pairs of southern right whales, totalling 1,136 individuals, marking a historic high in observed cow-calf pairs along the South African coastline. Additionally, 40 unaccompanied adult whales were sighted, indicating a persistent trend of low numbers in this category. Photo-identification analyses of the obtained photographs is still ongoing.
Before the annual helicopter survey, one aerial count survey was conducted, with the sole purpose of counting cow-calf pairs. This survey was flown in an eastward direction on 28 August 2023 using an autogyro. Results of this survey indicated the presence of 556 cow-calf pairs and 24 unaccompanied adults in the coastal area between Hermanus New Harbour and Witsand (covering the main nursery grounds).
The continued enormous fluctuations in the coastal prevalence of cow-calf pairs and the continued low presence of unaccompanied adults reiterate the extreme value of this long-term dataset.