Effect of hybridization on reproductive performance of Oreochromis karongae,Oreochromis shiranus and Oreochromis mossambicus

The study assessed the effect of hybridization on reproductive performance of Oreochromis karongae, Oreochromis shiranus and Oreochromis mossambicus for a period of 120 days. Number of eggs per batch, number of females spawned, relative fecundity, egg size, hatching period, hatchability and hatchling survival were assessed. The results revealed higher number of eggs per batch and relative fecundity in the crosses where O. shiranus and O. mossambicus were females than female O. karongae. The results also revealed that egg size, hatching period, hatchability and hatchling survival were species specific. Significant differences were noted for number of eggs and larvae produced by the three species (p < .05). Interspecific and pure crosses for the same female species did not differ significantly for the number of eggs per batch, relative fecundity, egg size, hatching period, hatchability and hatchling survival. However, number of female spawned was found to be higher in the interspecific crosses of female O. karongae than in pure cross of O. karongae. Findings from this study suggest that hybridization can be used to improve reproductive performance of O. karongae as the females spawned increased, and it is a value addition in aquaculture management of indigenous species.     

Effect of lipid levels on reproductive performance of Oreochromis karongae

A study was conducted at Bunda Fish Farm to evaluate the effects of dietary lipid levels on reproductive performance of Oreochromis karongae. Fish were reared in 12 hapas for 86 days, with four experimental diets containing 8.28%, 10.17%, 12.09% and 14.05% levels of lipid, replicated three times. At the end of the experiment, O. karongae fed 10.17% and 12.09% lipid had the highest absolute fecundity (237.5 ± 6.50 and 271.3 ± 26.19, respectively) as compared with fish fed on 8.28% and 14.05% lipid levels (90.3 ± 46.3 and 143.7 ± 30.8 respectively). Higher number of spawns (5) were observed in fish fed on diets containing crude lipid of 10.17%. We can assume also that diets of 10.17% lipid are not costly as those of 12.09% or 14.05% lipid. It was found that the size of eggs depended on the number of eggs spawned by the female fish, as the number of eggs increased, the weight of eggs and mean egg diameter decreased. There were no significant differences (P > 0.05) among treatments in terms of relative fecundity. Based on these findings, it is recommended that diets containing crude lipid of 10% should be fed to broodstock for optimum reproductive performance of O. karongae.