地理ジャーナルと自然災害
オープンアクセス

概要

Catch Rate, Distribution, Trophic and Reproductive Biology of the African Carp Labeo coubie in the Agbokim Waterfalls, Nigeria

GU Ikpi, A Jenyo-Oni, BO Offem

The catch rate, diet, size, and reproduction of 565 specimen of Labeo coubie were studied over 24 months (January 2005–January 2007) in three reaches [upstream, midstream (waterfalls region) and downstream] along the 6817.7 m length of Agbokim waterfalls during wet and dry seasons. Data were processed using fecundity (F), allometric coefficient (b), Fultons condition factor, and diet breadth. Fecundity values were 10411.0 ± 121, 15102.0 ± 303.5 and 24143.3 ± 662 eggs for fish from upstream, midstream, and downstream, respectively, with overall mean value of 19811.3 ± 223 eggs. The relationships of fecundity with total weight, ovary weight, ovary length, body breadth were positively linear. Mean allometric coefficient (b) of the length–weight relationship of fish in the three reaches were 2.662 ± 0.291 (upstream), 2.592 ± 0.368 (midstream), and 2.622 ± 0.315 (downstream) and all showed significant departure from cubic value (negative allometry). Detritus, phytoplanktons and plant materials were the dominant food items in the diet, contributing 36.8%, 32.1%, and 17.2% of stomach content, respectively. Food Richness of 7 and Gut Repletion Index, 100% were recorded. The low mean diet breadth exhibited by fish from the three sampling sites showed that the species has low trophic flexibility and cannot easily change feeding habit. Mean condition factor varied from 0.442 ± 0.127 upstream to 0.648 ± 0.146 downstream. Downstream therefore provided better spawning conditions for Labeo coubie in the tropical waterfalls ecosystems.