Pelagic fish resources are important for both the fishery and for the predators

By admin on Jul 14 in African Penguin Decline.

The pelagic fishery in South Africa is a purse-seine fishery based predominantly on anchovy, sardine and redeye herring with these species contributing typically more than 95% of the catch. These surface schooling fish species are small, fast growing but short lived. They are therefore vulnerable to rapid changes in environmentally driven recruitment and exhibit large natural fluctuations in abundance. Pelagic fish resources are important for both the fishery and for the predators that depend on them for survival. One of these top predators is the African penguin which depends mainly on energy-rich sardine Sardinops sagax and anchovy Engraulis encrasicolus for food, although other small pelagic fishes and squid are also eaten. Both the abundance and quality of prey are important in influencing their population dynamics. Unlike flying seabirds, African penguins must swim to find food, which limits their foraging range particularly while breeding. Furthermore, they require insulation against low oceanic temperatures and, to achieve this, replace their full plumage annually by moulting when they remain ashore for about three weeks without feeding. Therefore, they are especially susceptible to food scarcity during breeding and before and after moulting, activities which take place at colonies year-round. It is unlikely that fishing has reduced food availability such that it is limiting the penguin population because; (a) the proportion of pelagic fish biomass harvested in South Africa is low compared to small pelagic fisheries elsewhere in the world, and (b) the stock biomass is at 60 – 80% of its potential unfished level. These findings are based in part on credible biannual hydroacoustic surveys carried out by the research vessel the Africana by DFFE. The conservative and sound management of the small pelagic resource is due to adherence to science, backed up by a management procedure approach which is in line with modern scientific advice, further bolstered by regular international peer reviews of the science underlying the management.

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