Benthic macrofauna community composition, abundance and distribution in the Tanzanian and Ugandan inshore and offshore waters of Lake Victoria

Benthic macroinvertebrate community composition was investigated in 2008 at 55 stations at various depths in the nearshore and offshore waters of Lake Victoria, in relation to dissolved oxygen, pH, temperature, chlorophyll a and conductivity. Macroinvertebrate abundance was higher in the shallow nearshore waters than in the deep offshore waters. The communities of the shallow, intermediate and deep environments were composed mainly of molluscs, worms and insects. Gastropods (52.68%) and bivalves (40.18%) constituted the major part of the benthic community. Bellamya unicolor, Melanoides tuberculata and Coelatura spp. were the most abundant molluscs. Various macroinvertebrates showed depth preferences, with gastropods having a strong preference for shallow waters and bivalves a weak preference for deep waters. The present findings contrast with those of most studies done before 1984, but agree with many done after that period. The presence of macrophytes and abundant detritus, a food resource for macroinvertebrates, account for their high abundance in shallow waters.