Shark nets along South African coast threaten rare dolphins

07.10.2016 10:06
Kategorie: News

Negative effect on biodiversity

Along the coast of KwaZulu-Natal in South Africa, many dolphins die in gillnets set up to protect swimmers and surfers from shark attacks. In a scientific study, scientists warn of the possible extinction of the rare Indian Ocean humpback dolphin (Sousa plumbea) in the waters of KwaZulu-Natal. The Society for Dolphin Conservation (GRD) is committed to reducing shark nets as soon as possible.

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Negative effect on biodiversity
To protect people from shark attacks, about 400 metres off the coast of popular beaches, gillnets that are about 200 metres long and six metres high have been installed. However, it is not just sharks that perish in such nets; numerous other marine animals – totally harmless to people – like stingrays, sea turtles, smaller sharks and dolphins also perish because of them.

Richards Bay: death trap for dolphins
The 320-kilometre coastline of KwaZulu-Natal (with their 37 beaches) are protected by 23.4 kilometres of nets. However, 60 percent of the Indian Ocean humpback dolphins die in Richard Bay, which has gillnets spanning 1.1 kilometres. Marine biologist Shanan Atkins from the Endangered Wildlife Trust in Johannesburg highlights a long-term study that shows that the dolphins travel along the coast of Richards Bay frequently. This leads to the constant threat of dying in a gillnet, which causes a continuous weakening of the population, according to Atkins.

The last of its kind in South Africa
It is estimated that there are less than 1,000 Indian Ocean humpback dolphins left along the coast of South Africa. In KwaZulu-Natal, the number is probably about 200 individuals. The dolphin species is actually the most endangered marine mammal in South Africa.

Preventing shark attacks without killing sharks
To minimise shark attacks, the GRD advocates the use of alternative, non-lethal measures to deter sharks. These include “electric fences” anchored on the seabed to discourage the electro sensitive sharks or the use of “shark-spotters” (people who keep a lookout and warn others of approaching sharks). These measures have proven to be effective at the beaches of Cape Town. “While people are being protected from shark attacks, dolphins, sharks and other marine animals would not have to pay the price with their lives,” said GRD biologist Ulrich Karlowski.

Roland Mauz from the dive centre African Dive Adventures, who operates at Margate and Shelley Beach in KwaZulu-Natal, describes the situation there: “Ever since the nets were installed in the 1970s, almost all the coastal sharks have become extinct. Only very rarely is a shark caught in the nets, because they are simply no longer around. The damage is already done, and things cannot be worse.