Composition and seasonal variations in abundance of Copepod (Crustacea) populations from the northern part of Lake Tanganyika

Abstract

Copepod has an important ecological role as a main food of several fishes on which commercial fisheries are based in Lake Tanganyika. However, very little multi-annual monitoring programs have been conducted for this group of crustacean zooplankton. This study was conducted in the northern part of Lake Tanganyika by weekly sampling at both pelagic and littoral sites over three consecutive years (2012–2014). The analyzed samples showed that Lake Tanganyika copepod was essentially composed of three suborders including Calanoida (30% by number) with a single endemic species, Cyclopoida (69%) with four dominant species and Harpacticoida (1%). These taxa showed variations in their abundance respectively at pelagic and littoral sampling sites. The average densities of copepods did slightly vary during the sampling period in both areas although higher peaks were observed in 2013. For the post-nauplii stage, Tropocyclops tenellus predominated while the nauplii of T. simplex predominated at both sampling sites. Seasonal fluctuations of copepod densities showed higher peaks in September/October and April/May, respectively, for the three most common species. T. simplex and M. aequatorialis ovigerous females showed higher peaks in the rainy season in 2013. These results can benefit pelagic fisheries research and lake environmental management efforts as the copepod abundance seems to be closely correlated to that of sardines in Lake Tanganyika.