The study was carried out between September 2011 and August 2013, using 328 Clarias gariepinus in Oba reservoir, Oyo State, Nigeria. Standard methods were used to determine gonado-somatic index (GSI), fecundity values, and enteroparasitic infestation of the fish. Sex ratio was 1.3:1, male to female, and females on an average invested 20.54 % of its body weight in egg production while male GSI was 6.05 ± 0.19 %. Spawning was prominent in rainy season; the fish was highly fecund (31,169 eggs) with relative fecundity of 222 ± 10 eggs per gram weight of fish. Fecundity correlated linearly (positive) with gonad weight, body weight, total length and GSI. Over fishing, led the fish to invest its body weight and growth in egg production, to increase and enhance its chances of survival. Parasites recovered were Procamallanus laevionchus, Paracamallanus cyathopharynx, Anomotaenia sp., Monobothrium sp., Polyonchobothrium clariae, and Neoechinorhynchus rutili. Prevalence and intensity was higher in female than in male and more in dry than rainy season. Parasitic infestation reduces weight growth in the fish; this influenced the values of reproductive indices in which body weight was a numerator or denominator.

Keywords: Clarias gariepinus, enteroparasites, fecundity, gonado-somatic