Author(s): P. A. Ekokotu and N. F. Olele

Abstract: A population of Clarotes laticeps (family Claroteidae) was investigated in the lower reaches of the River Niger, between Illushin in Edo State and Niger Bridgehead in Asaba, Delta State, Nigeria. The study lasted between, January, 2010 and December, 2012. Fish samples were taken every fortnight from the stretch of the River Niger studied and transported to the laboratory where each fish sample was evaluated for the cycle of maturation of gonads, length size at first sexual maturity, gonadosomatic index and condition factor. Each of these values were recorded against the period of the year the fish samples were collected. The frequency and seasonal distribution of these parameters were noted and used to determine the size at first maturity and spawning. Mean condition factor (k) and gonadosmatic index (G.S.I) obtained were 2.10 and 0.54, respectively, in January, with both reaching peak values in August (K, 2.81; G.S.I, 11.86), but dropped to 2.05 and 0.75, respectively, in October. The female specimens matured earlier at 30.5 cm, standard length, while the male specimens attained sexual maturity at 32 cm, standard length. There were increases in the frequency of mature gonads, condition factor, and gonadosomatic index between July and September. Both parameters began to fall in October, indicating that spawning occurs between July and October. A mean egg diameter of 2.92 mm recorded was considered as relatively large in size. This could support fry survival both in the wild, and in culture trials.

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