GROWTH PERFORMANCE, FECUNDITY AND SEXUAL GROWTH DIMORPHISM OF Oreochromis esculentusAND Oreochromis niloticusUNDER CAGE CULTURE IN KISII COUNTY, KENYA

Abstract

Oreochromis esculentus, a fish species relished by peoplearound the Lake Victoria region is no longer abundant due to competitive exclusion by introduced fishes and fishing pressure. There is a need for its culture for production and determination of its growth performance in captivity. Little information is available on the growth ofO. esculentusin captivity. This study aimed to evaluate growth performance, sexual growth dimorphism and fecundity of two species, the threatenedO. esculentusand the traditionally culturedOreochromis niloticusfor recruitment of the former in aquaculture. Growth trials were undertaken at the Fish Multiplication Centre in Kisii County. Three treatments ofO. esculentus(from Gesebei dam), O. niloticus(from County Fish Multiplication and Training Centre –CFMTC) andO. niloticus(from Kitaru dam) were replicatedfour times in cage culture. Each cage was stocked with 30 fingerlings, cultured for eight months and fed twice daily. Fish samples were collected biweekly for weight and length measurements. Eggs/ fry were retrieved from brooding females and relative fecundity was evaluated. Data was analyzed using the analysis of covariance. For asymptotic weight,O. niloticus(CFMTC) weighing 329.7±5.48 g outperformedO. esculentus(Gesebei) 317.7±5.48 g andO. niloticus(Kitaru) 258.8±5.48 g (p <0.05). The O. esculentushad the highest asymptotic length of 30.5±0.29 cm, followed byO. niloticus(CFMTC) 28.5±0.29 cm and 26.5±0.29 cm forO. niloticus(Kitaru) (p <0.05). There was no significant difference in growth performance between the males and the females ofO. esculentusin terms of asymptotic length and weight. For relative fecundity, there was no significant difference with slopes for fecundity means at 95% confidence intervals, withO. esculentus(Gesebei) at -0.07543,O. niloticus(CFMTC) andO. niloticus(Kitaru dam) at -0.06036 and -0.12034, respectively. The study showedO. esculentusis suitable for aquaculture due to its performance in length and can be a conservation strategy.