Oocyte Structure, Fecundity and Sex Ratio of Heterobranchus longifilis (Valenciennes 1840) in Idodo River Basin (Nigeria) with comments on the Breeding Biology

Abstract

The reproductive parameters – oocyte structure, fecundity and sex ratio of the catfish, Heterobranchus longifilis, Valenciennes 1840 were investigated between April, 1991 and September, 1992 in Idodo River basin. Oocyte diameter had a bimodal size distribution which is indicative of the possibility of multiple spawning cycles in a year. Spawnable oocytes which constituted more than 90% of gonad weight ranged from 1.15 to 1.85mm in diameter. The number of oocytes in both ovaries ranged from 6001 to 51,216 eggs per female Fecundity was linearly related to total length, standard length, body weight, and ovary weight. The equation Y = - 3751.699 + 28 39.383 X (r = 0.984) for fecundity – ovary weight showed a more predictive relationship. The mean yearly sex ratio of 1:1.24 was not statistically significant (P >0.05).


Journal of Aquatic Sciences Volume 15, April 2000, pp. 59-62



KEY WORDS:

Oocyte structure, fecundity, sex ratio, Heterobranchus longifilis, Idodo River.