Variations in fecundity and egg size of female Nile tilapia, Oreochromis niloticus, from man-made lakes of Cote d'Ivoire

Fecundity and oocyte size of Oreochromis niloticus females were studied ove r a period of two annual cycles in six small agropastoral and three large h ydroelectric reservoirs of Cote d'Ivoire. Important differences in fecundit y and oocyte size were observed among populations and within the same popul ation between successive years. An inverse correlation was found between si ze and number of oocytes produced by females. This inverse relationship occ urred for a constant spawn weight during the first year of study, but not d uring the second year. Monthly mean residuals of regressions between fecund ity and female body weight have shown a seasonal variation in fecundity. Th e peak of fecundity corresponded with the maximum resource availability and the flooding eminence, which may have a great impact on parents and offspr ing fitness.