Changing methods of bather protection may help humpback dolphins to survive, South Africa
© Endangered Wildlife Trust
To decrease by-catch and increase awareness of humpback dolphins in South Africa
The humpback dolphin, Sousa chinensis, is widely distributed along the rim of the Indian Ocean, near some island coasts and in near-shore water of the western Pacific. It seems to occur in pockets of high density separated by areas of low density along stretches of coast. Living as they often do in close proximity to industrialized, polluted, and heavily populated regions, humpback dolphins are exceptionally vulnerable.
Along the coast of Kwazulu-Natal, South Africa, humpback dolphins die in the shark nets at what is deemed an unsustainable rate. Shark nets are gill nets set to catch and kill sharks in order to reduce the local population of sharks to decrease the probability of shark attacks on humans. The nets are not species-specific and more than 50 species of large marine animals are caught, with the majority being bycatch. One of the bycatch species of particular concern is the humpback dolphin.
This species has been classified as Vulnerable on the South African Red Data List and thus unnecessary losses should be avoided at all costs and their population dynamics must be monitored. Acoustic warning devices (pingers) have been fitted to the shark nets off the coast of South Africa in an attempt to reduce the Humpback Dolphin mortality rates, but continued mortalities indicate that these devices may not be successful.
The Endangered Wildlife Trust (EWT) has been monitoring the populations of Humpback Dolphins along the KwaZulu-Natal (KZN) coastline since 1998 through its Marine and Coastal Conservation Group. The project has comprised ongoing monitoring of the populations of Humpback Dolphins, and other dolphin species found in this region, investigating the mortalities of dolphins in shark nets, and a behavioural ecology study was initiated to better understand the Humpback Dolphin and the causes of capture in the shark nets. However, this project has broadened to include public education since it is clear that most people do not understand how the shark nets work. It has broadened further to include a search for an alternate method of bather protection. This is of great importance because if an alternate, more environmentally friendly method of bather protection can be used, none of these species would have to die.
In a joint partnership, the EWT and the NSB have spent seven years testing are acoustic warning devices, pingers, set to warn dolphins about the presence of the nets. Unfortunately the pingers did not have the desired effect of reducing the mortality rate of dolphins. The NSB has also tested using drumlines instead of nets, which are baited hooks that catch and kill sharks but with a reduced by-catch and thus reduced risk to other species. These have proved somewhat successful and plans are afoot to replace some nets with drumlines in the near future. However the NSB fears resistance from the public.
WAZA Conservation Project 05024 is operated by the Endangered Wildlife Trust's (EWT) Marine and Coastal Conservation Group, supported by Ushaka Marine World, Durban (South Africa), and the Kelley Legge Dolphin Fund. In cooperation with Natal Sharks Board, Richards Bay Coal Terminal, Local Municipalities along the Natal-Kwazulu Coast, and the National Ports Authority.
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© Endangered Wildlife Trust