Abstract

The fish Sarotherodon galilaeus was collected in Opa reservoir, Obafemi Awolowo University, Helfe, Nigeria. Sampling began in January, 1992 and extended until March, 1994. The fishing methods empJoyed for collecting the 853 specimens were gillnetting and castnetting. Sex ratio was approximately J: l (maJe: female). Length at maturity was 12.5 cm (males) and 11.7 cm (fe males). The fecundity was 1 048 ± 785 (604- 2 173, n = 117) with an egg diameter of 2.49± 1.81 (1.0 - 4.5, n = 117) mm. The gonado-somatic index was 033 ± 0.21 (0.09 - 1.34, n = 275) (males) and 1.88 ± 1.01 (0.33 - 6.19, n = 282) (femates). The species breeds year-round (mature specimens occurred in samples collected throughout the 27-month study period). Thisfish is a biparental mouth booder
Keywords: reproductive biology, sarotherodon galilaeus, fecundity, gonado-somatic index, biparental