Notes on the occurrence and biology of Xenoclarias Greenwood (Siluriformes: Clariidae) in Lake Victoria,East Africa

Summary

Xenoclarias inhabits the deeper (>50 m) waters of Lake Victoria. Specimens captured in a bottom trawl ranged in size from 10–22 cm TL (mode, 15–18 cm) and females grew to a larger size than males. Length-weight relationships between sexes were different only in the Kenya waters and resulted in significantly different KTL. Based on gonadal stages, Xenoclarias matured between 14–16 cm (age 1). Fecundity of 6 specimens (Stage VI) ranged from 744–1357 (mean 1009) and egg size from 1·45 to 1·98 mm (mean 1·79 mm).

Based on gravid and spawning females, Xenoclarias spawned prior to the rainy season (January–March) in Kenya and Uganda waters. During periods of increased reproductive activity females were consistently more numerous in samples (2:1) than males. Local meteorological and hydrological conditions may explain the apparently different spawning season in Tanzania waters of the Lake. This genus of small fish is not affected by the artisinal gillnet fishery but may be by the expansion of a bottom trawl fishery in Lake Victoria.