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Text: Ian Michler. Photos: Johan Huisamen. Article from the June 2012 issue of Africa Geographic Magazine.
Fishermen have been pointing fingers at seals for decades, accusing them of ‘stealing’ the fish their livelihoods are based on. But is there any truth in the claims? Ian Michler reports on a South African study that suggests not.
Over the past two centuries, seals across all oceans have suffered heavily at the hands of commercial sealers and the pro-culling lobbies that perceive pinnipeds to be a threat to large-scale fishing industries. Canada has the worst record: its government sanctioned a total allowable catch of 330 000 seals in 2010 alone. In the southern hemisphere the only country that still allows culling is Namibia, where in 2010 85 000 South African fur seals were killed, of which 90 per cent were pups clubbed to death.
Despite evidence to the contrary, the fishing industry continues to lay the blame for collapsing fish stocks on seals rather than on its own unsustainable practices. But there is a body of research that refutes this long-held misconception, and a new addition to it is a study by Johan Huisamen, the ecological coordinator for CapeNature (www.cape nature.co.za) on South Africa’s Garden Route. Huisamen recently completed a 10-year survey of the South African fur seals that have made their home on the Robberg Peninsula, a familiar landmark near Plettenberg Bay. His findings show that after an absence of almost a century, a colony of seals is re-establishing itself on this rocky finger of land. What’s more, the research included a comprehensive diet analysis that suggests the mammals have not been a major competitor to the local fishing industry.
South African fur seals are the only resident pinniped found along the continent’s southern coastline, with 40 breeding colonies associated with the colder waters of the Benguela Current off the western shore and only two occurring in the warmer Agulhas Current east of Africa’s southernmost tip.
Early records suggest that Robberg – ‘seal mountain’ according to the Dutch settlers who named the peninsula – hosted a colony of more than 3 000 seals until the 1830s. By 1890 it had been wiped out by Dutch, French, American and British hunters who were active along the entire Cape coastline, harvesting the animals for their skins, meat and blubber. It is thought that another eight such colonies east of Cape Agulhas were hunted to extinction.
It was only in the early 1990s that seals began to return to Robberg and were regularly sighted. By 1996-97 the first pups were seen, prompting closer observation by the local scientific and conservation community. Huisamen initiated a research project in 2000 and since then he has monitored the size and dietary habitats of the colony. His work is contributing to an MSc in Nature Conservation through the Nelson Mandela Metropolitan University.
It has been shown that the local populations of (hake and chokka) collapsed as a result of overfishing rather than because of any inpact from the seals.
‘Numbers increased significantly, from fewer than 30 animals in 2002 to more than 3 000 in 2010,’ says Huisamen. ‘There were large variations in the counts to begin with, but these stabilised towards the end of the study period, which indicates an increasing proportion of resident seals in the colony,’ he adds. However, the colony does not yet produce more than 100 pups per season – the defining characteristic – and is thus not considered to have reached breeding colony status yet.
According to Huisamen, his project was initiated in response to mounting pressure from the local fishing industry to ‘do something about the seals’. The growth in the colony coincided with a steady decline in the local fish stocks, giving the fishing community its chance to rehash old misconceptions. Members of the hake and chokka (squid) fishing fraternity even called for the introduction of a culling programme, although it has since been shown that the local populations of these species collapsed as a result of overfishing and other unsustainable practices rather than because of any impact from the seals.
The researcher reports, ‘Little evidence of direct competition between seals and local line-fisheries in Plettenberg Bay was found, in terms of prey species or quantities consumed. The three most important fish species in the diet of Robberg seals are pelagic: anchovy, sardine and horse mackerel. They make up more than 66 per cent of the seals’ diet. Of these, only sardines are harvested by the purse-seine fishermen along the Cape coast.’
Huisamen’s study was published in the African Journal of Marine Science 2011 33 (3).
For more information, contact Johan Huisamen at jhuisamen@cape nature.co.za
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