Abundance of Zooplankters on a Rocky Shore of Lake Tanganyika: A Preliminary Report

Abstract

Abundance of zooplankters was examined by net collection on a rocky shore at the northwestern end of Lake Tanganyika in February 1980 and August 1983. Zooplankters found were Mesocyclops leuckarti, Diaptomus simplex, Ergasiloides sp. (Copepoda), Ostracoda, shrimps, Asplanchna sp. (Rotifera) and Vorticella sp. (Protozoa). Species composition of zooplankton was rather simple and characterized by the dominance of Copepoda, especially nauplii and cyclopoid copepodites. Nauplii smaller than 0.2 mm in body length were more abundant in August than in February, which suggests that the reproductive activity of copepods changes seasonally. The density of zooplankters tended to be lower at the bottom in the daytime, probably because of the predation by fish. The density of copepods changed with the time of day; low at noon and high in the afternoon. Such diel fluctuation in the abundance of copepods may influence the feeding activity of fish.