E. M. Kembenya1, 2*, R. N. Ondiba1, 2 and M. B. Angima2
1Kenya Marine and Fisheries Research Institute,
P.O Box 136, 40111, Pap Onditi, Kenya
2Kisii University P.O Box 402, 40200, Kisii, Kenya: +54720592917
*Corresponding Author: email@example.com
Growth performance of mixed sex and male monosex O. niloticus was done in cages at LwandaDisi beach, Lake Victoria, Kenya. Male monosex fingerlings were sex reversed by feeding newly hatched larvae on feed laced with 17-α-methyl testosterone hormone (MT) for 28 days. Mixed sex fingerlings were collected from nursery ponds and fed MT hormone free starter mash before stocking. A total of 6 cages (2x2x2m) were randomly stocked with 1000 monosex fingerlings (mean weight 9.5±0.01g) and mixed sex fingerlings (mean weight 8.6±0.04g). The fish in cages were fed starter mash 40% Crude Protein (CP) at 10% of body weight for first two months. In the second month till the end of the experiment the fish were fed 30% CP 3% of the body weight. Measurement of fish length weight and selected water quality variables was done once a month for a period of six months. Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), Relative Condition Factor (Kn) and survival rate (%) was calculated at the end of the experiment. The male monosex O. niloticus attained a high final length and weight, SGR, FCR than the mixed sex O. niloticus (p < 0.05). Survival rates were similar in both male monosex and mixed sex O. niloticus (p > 0.05). There were no significant differences in mean water quality parameters between male monosex and mixed sex in cages (p > 0.05). Though the mixed sex O. niloticus did not reproduce in cages they performed poorly as compared to male monosex. This is attributed to the fact that Nile tilapia exhibit a sexually dimorphic growth pattern in which males grow faster and bigger than females. This study recommends all male O. niloticus for cage culture.
Keywords: Cages, Nile tilapia, mixed sex, monosex