Controlled fishing experiment raises controversy over cause of birds’ decline on Robben Island.
15 October 2014
Robben Island is notorious as the site where Nelson Mandela spent 18 years in prison, but now the island’s 1,200 breeding pairs of African penguins are sparking a scientific controversy. At stake is the survival of an endangered species, as well as how fisheries around the world are managed.
In 2013, there were just 22,000 breeding pairs of African penguins (Spheniscus demersus) worldwide: the population had declined by 65% since 2001. Possible causes include pollution, habitat loss and climate change, but a key suspect is fishing of anchovies and sardines, which are important prey for penguins.
To test this theory, in 2008, the now-defunct South African Department of Environmental Affairs and Tourism began an unusual experiment involving two pairs of islands: Robben and Dassen islands, off South Africa’s west coast; and St Croix and Bird islands, off the country’s south coast. For three years, a zone around one island in each pair was closed to fishing while the other island remained open. Then the situation was reversed. The rare controlled experiment has “important implications for fisheries worldwide in competition with vertebrate predators”, including seabirds, seals and dolphins, says Johann Augustyn, secretary of the South African Deep-Sea Trawling Industry Association in Cape Town.