Aspects of the reproductive biology of Oreochromis macrochir (Boulenger) and Oreochromis niloticus (L.) (Cichlidae) in Lake Chivero, Zimbabwe

Abstract

Oreochromis niloticus and O. macrochir are alien species introduced into Lake Chivero, Zimbabwe with the former becoming the more successful of the two.  Their reproductive biology was investigated to determine if it could account for this difference.  Both species bred primarily during summer (August to April) although some male O. niloticus with active gonads were found throughout the year.  Males of O. macrochir tended to show some breeding activity over a longer period than females but were inactive during winter.  The length at maturity of males was similar in both species but females of O. niloticus matured at a smaller size (19.8cm) than females of O. machrochir (22.3cm).  The mean relative fecundity of O. niloticus was significantly higher than that of O. macrochir.  This might be one of the few factors that might account for its relative success in the lake.

Keywords : Breeding, Fecundity, Competition, Seasonality, Maturity.