Reproductive strategy of Marcusenius ussheri (pisces, Mormyridae) in the fluvio-lacustrine system of the Bia River (Ivory Coast)

A study of the reproductive biology of Marcusenius ussheri has been carried out during 12 sampling months in the Bia River catchments' area. Fishes have been caught with gill nets. A dam has been built on the stream of the river. This dam has created three different ecological zones. The size at first sexual maturity presents variations along the river (upstream, the lake and downstream). Females are slightly smaller than males. Data of gonadal maturition and gonado-somatic index both indicate that breeding varies according to the hydrological and seasonal conditions. The oocyte diameter at spawning is 1.8mm; relative fecundity reaches 31834 oocytes per kg body weight. The environmental conditions which exist in the lake seem more favorable to M. ussheri reproduction than those in the stream parts.