Abundance and distribution of inshore fish in fished and protected areas in Lake Kariba, Zimbabwe

Abstract

Abundance and size distribution of inshore fish populations was assessed by fishing with standard Lundgren survey gill-nets in areas open to fishing and reserved areas that are protected from fishing activities. The direct gradient analysis technique - Detrended Canonical Correspondence Analysis - revealed that fish abundance and their composition in Lake Kariba are strongly structured by lake morphometry. The comparison between fished and reserve areas showed that there was a significant reduction in mean length of commercially fished species in the fished areas and the size distribution curves were skewed, lacking small and large length classes. There was a higher abundance of non-commercial species in the fished areas. It was also revealed that the mochokid Synodontis zambezensis Peters 1852, was the most abundant species and was present at all depths sampled in all the stations. There were indications that non-commercial species were important in terms of abundance in the fished areas. These included S. zambezenzis, Schilbe intermedius (Ruppell, 1832) and other smaller species. This was attributed to them being selected against in the gill-nets.