Changes in demersal cichlid communities as a result of trawling in southern Lake Malaŵi

Abstract

Many of the endemic cichlids of Lake Malawi have low fecundities and restricted distributions within the lake (Fryer and Iles, 1972; Ribbink et al., 1983). Consequently, they may be particularly vulnerable to local overfishing. Many of the fisheries on Lake Malaŵi catch a large number of species with different life history characteristics (Chapter 17). Most species have similar economic values. Thus, populations of more vulnerable species may decline long before fishing becomes uneconomical. The two fishing techniques most likely to pose such a threat are small-meshed beach seines and demersal pair trawls. At present, almost nothing is known of the biological basis of the seine fisheries. However, recent studies on trawling grounds in the south of Lake Malaŵi have shown that fishing has had considerable effects on the populations of many cichlid species.