Morphology of the gonads in the reproductive cycle of Synodontis schall (Pisces: Mochokidae) in Asa Lake Ilorin, Nigeria

Abstract

The gonads of specimens of Synodontis schall (N = 813) in Asa lake were observed for morphological changes for 24 months. The female population (54.6%) was more than the male (45.4%) and all the gonad stages were observed in both sexes. The juveniles constituted (12.7%) of the total population. Gonad and body weight relationship in female (0.54) was positively correlated. Similarly the gonad and body length relationship in male (0.77) and female (0.68) were positively correlated. The months of July and August were the peak spawning periods during which the littoral zone became flooded due to the rains. The male and female S. schall in the lake were ready for spawning about the same time hence there was the tendency for a high percentage of the male population pairing with the female for fertilization. Fecundity was high (7,910 to 64, 450 eggs) and the mean eggs diameter at the spawning stage was 1.03 mm. There is need for enhanced monitoring actives in order to enforce fishing rules and regulation around the water body to protect gravid specimen from being over exploited. The advantages of higher female population were discussed.


JOURNAL OF AQUATIC SCIENCES Volume 16, Number 2, October 2001, pp. 105-110




KEY WORDS:

Synodontis schall, gonads, fecundity, spawning