Mortalities of southern right whales (Eubalaena australis) and related anthropogenic factors in South African waters, 1999 ? 2019
Els Vermeulen, Elise Jouve, Peter Best, Geremy Cliff, Matt Dicken, Deon Kotze, Steven McCue, Mike Me?er, Mduduzi Seakamela, Greg Thompson, Chris Wilkinson
In view of observed changes in the southern right whale (Eubalaena australis; SRW) population since 2009 and the increased anthropogenic activities in South Africaâ€™s coastal waters, an update on SRW mortalities and related anthropogenic factors is warranted. Building on the published information of Best et al. 2001a, data were collated on all SRW mortalities as well as non-fatal ship-strikes and entanglements along the South African coast between 1999 and 2019.
A total of 97 SRW mortalities were recorded along the South African coast between 1999 and 2019, of which the majority were classified as calves of the year. Most strandings occurred on the Western Cape coast between the months of July to November, coinciding with the seasonal presence of the species in South African waters. Eleven of these mortalities could be attributed to ship-strikes whereas 3 mortalities related to entanglements.
In total, 14 ship-strikes and 86 entanglements with SRWs, which did not result in a direct mortality or for which the outcome remained unknown, were recorded in South Africa between 1999 and 2019. Ship-strikes occurred mainly around the area of Cape Town harbour. Entanglements occurred mainly in rock-lobster gear and bather-protection nets in the Western Cape and KwaZulu-Natal provinces respectively, although the latter ceased to occur since 2015 likely due to the replaced of nets by drumlines.
In general, the incidence of SRW mortalities and entanglements decreased post-2009, coinciding with the decreased presence of SRWs along the South African coast. Data suggest that entanglements and ship-strikes do not pose a major conservation threat to the South African SRW population. However, the actual impact of such events may be underestimated as many may go undetected. In view of the population growth rate and the increased anthropogenic activities in coastal South Africa related to â€œOperation Phakisaâ€, continued monitoring of these incidences is crucial to ensure accurate knowledge-based management decisions in the future.