The benthic macrofauna community of Kenyan waters of Lake Victoria

Abstract

The benthic macroinvertebrates in the Kenya waters of Lake Victoria (ca. 1400 km2) were surveyed during four 10 day sampling periods in February, April, August and November 1984. Fourty three taxonomic groups were recorded. Oligochaetes, molluscs and dipteran larvae were the most abundant and widely distributed groups. The dominant oligochaetes were Branchiura sowerbyii Beddard and the swamp worm Alma emini Michaelsen, which were abundant in all silty and soft mud areas in both littoral and open water zones. Melanoides tuberculata Muller, Bellamya unicolor Olivier and Caelatura spp. were the most abundant molluscs. Different patterns were observed between near-littoral stations (<8 m deep) and deep water stations (8–40 m deep). After 10 years (1994), the macroinvertebrates of Lake Victoria were examined again. No evidence was found of seasonal changes in the composition or benthos density, although local changes occurred in some species which were attributed to swarming behaviour or larval settlement patterns. The spatial distribution of the fauna may be influenced primarily by oxygen availability and industrial effluent discharged from paper mill and agro-based industries in the catchment of the lake. There has been a shift in abundance, from an Oligochaeta and Insecta dominated community in 1984, to the present community dominated by Mollusca and Oligochaeta. The ecological role of the benthic community and its recent changes to fisheries production in the lake is discussed.