Length-weight relationship and diet of Gymnarchus niloticus in a tropical man-made lake, Southwestern Nigeria

Abstract

The trunk fish, Gymnarchus niloticus (Family Gymnarchidae) is endemic to Africa. This study reports the length – weight relationship (LWR) and food habit of 108 specimens of G. niloticus in Eleiyele Lake, Ibadan Nigeria were investigated. The LWR of the species showed positive correlation (r > 0.67). The regression exponent (b < 3) for the combined specimens showed negative allometric growth pattern. Variations were recorded in the b value with months and size groups. The mean condition factor (K) was 0.231 ± 0.01. Significant variation occurred in K with size groups and the smallest size group recorded the highest value (0.225 ± 0.01). Diet evaluated with the Index of Relative Importance (IRI) showed that G. niloticus primarily consumed fish (94.9%).