Condition Factor, Gonadosomatic Index and Sex Ratio of the Family Mormyridae from a Small Lake in Ilorin, Nigeria

Condition factor, gonadosomatic index, sex ratio and length weight relationship of Mormyrus rume, Mormyrus hasselquisti, Gnothonemus cyprinoides, Gnathonemus senegalensis and Petrocephalus bane ansorgei (Mormyridae) from Asa Lake, Ilorin, Nigeria were studied. The results showed that the condition factor range were 0.57-1.12, 0.64-1.22, 0.46-0.98, 0.66-1.18 and 0.86-1.28 in G. senegalensis, G. cyprinoides, M. rume, M.hasselquisti and P. bane ansorgei respectively. The highest gonadosomatic indexes were obtained in G. cyprinoides and M. hasselquisti indicating that about 10% of the body weight of these fishes was used in production of eggs. The sex ratio values for G. senegalensis, G. cyprinoides, M. rume, M. hasselquisti and P. bane ansorgei were 2.5:1, 1.8, 5:1, 2.5:1 and 2.5:1 male to female respectively. There were more males than females in all the species studied. The reproductive strategy of more males than females would help to control overpopulation in the lake.