The biology of Clarias ebriensis Pellegrin, 1920 (Osteichthyes : Clariidae) in an African rainforest river basin

摘要

The West African catfish, Clarias ebriensis, is commercially important and cultured in floodplain ponds. This paper describes the abundance, condition, reproduction, food and parasites of C. ebriensis in the Anambra river basin, Nigeria. This clariid occurred more abundantly and frequently in forest floodplain ponds than in other habitats. Weight ranged from 4 to 240 g and TL from 54 to 437 mm, males being heavier and longer than females. Mean relative condition was not sex-dependent and showed a definite cycle with the highest value in March/April or June and the lowest in September. Maturity was not sex-dependent. Fecundity ranged from 2.746 x 10(3) to 54.216 x 10(3) oocytes (mean 14.730 x 10(3) +/- 10.799 x 10(3) oocytes). Ovary weight was the best predictor of fecundity and GSI. First communal spawning, along with Clarias agboyiensis, C. buthupogon, C. albopunctatus and C. anguillaris, occurred in the first year of life. Feeding was mainly at night and stomach fullness index was higher in the rainy than dry season. The index of food significance (IFS) showed that fish, and insects were equally important, followed by molluscs and crustaceans. Qualitative food composition and food richness were size- and sex-dependent but not season-dependent. Observed feeding behaviors were foraging, shoveling and surface feeding. Euclinostomum clarias, Procamallanus laevichonchus and a larval spiruroid (f. Physalopteridae) parasitized various organs. C ebriensis is a new host record for these helminth parasites. The presence of high numbers of larval spiruroid in the muscles resulted in consumer resistance.