Abstract:
The current study evaluated growth performance, survival rate, feed conversion ratio, heterosis, heritability, responses to selection and breeding values of four populations of Sarotherodon melanotheron from Fosu Lagoon, Brimsu, Baifikrom and Weija reservoirs in 4 × 4 diallel crosses aimed at producing a hybrid with high growth, reproductive and survival traits to enhance aquaculture production. Triplicates of a single-pair mating design for the diallel crosses yielded 3,840 fingerlings. These were tagged and stocked communally in both freshwater (cages) and brackish water (tanks) for 120 days using a randomized complete block design. Different doses (0, 30, 60, 90 and 120 mg/kg) of 17α-methyltestosterone were fed to black-chinned tilapia fry for 28 days to determine the effective dose for all-male sex reversal. The results indicated that five hybrids (Baifikrom × Fosu (RF), Fosu × Weija (FW), Brimsu × Weija (BW), Baifikrom × Brimsu (RB) and Brimsu × Baifikrom (BR)) were significantly (P ˂ 0.05) heavier in harvest body weight compared to their parental stocks and other hybrids. Overall mean heterosis estimates indicated that seven (7) out of the twelve hybrids exhibited positive heterosis ranging from 0.17 ± 1.95 to 22.17 ± 5.52 %. Moderate to high heritability ranging from 0.29 ± 0.05 to 0.63 ± 0.21 were observed for the hybrids. The pooled genetic performance of the hybrids suggested the need to develop two separate lines for fresh and brackish water culture. However, the hybrid of Weija × Brimsu (WB) was most suitable for culture in both fresh and brackish water. The 17α-methyltestosterone test indicated that S. melanotheron fry fed 90 mg/kg feed for 28 days, had the highest sex ratio of 84.13 % males. For effective sex reversal in S. melanotheron, the hormone dosage should not exceed 90 mg/kg.
