GROWTH PERFORMANCE AND ESTIMATE HETEROSIS OF JUVENILE OF NILE TILAPIA Oreochromis niloticus, BLUE TILAPIA Oreochromis aureus AND THEIR HYBRID REARED IN THE FRESHWATER POND  

Hybridization or cross-mating between strains or species is one of several ways to improve the genetic quality of fish. The hybrid between nile tilapia O. niloticus and blue tilapia O. aureus is expected to has better performances than their parents. This experiment aimed to observe the growth performance and estimate the value of heterosis of the hybridization between nile tilapia and blue tilapia. The research was carried out for 5 months at the Research Institute for Fish Breeding at Sukamandi, West Java (Indonesia). There were two strains or species of tilapia involved in this experiment, i.e. Nirwana strain of nile tilapia and blue tilapia. Inter and intra species of spawning were conducted communally in a freshwater pond sized of 25 m². Tilapia broodstock were stocked to spawning pond with male to female ratio of 10:30. After 7-10 days of stocking, eggs were collected from broodstock and incubated in hatching funnel in the hatchery. The hatched larvae were then reared in the subsequent nursery hapas sized of 2x2 m for 60 days or after fingerlings reached the average individual weight of 2.16 g.

At the growing-up stage, fingerling were reared in the 3x5 m² net which was installed in the earthen pond sized of 200 m². The stocking density applied at this stage was15 fish/m². Fish were grown for 150 days. The results showed that pure Nirwana strain population revealed the highest growth  performances with individual weight of 111.74 g, specific growth rate (SGR) of

2.51% body-weight/day and feed conversion ratio (FCR) of 1.37. The crossing between female Nirwana strains and male blue tilapia showed the moderate growth performances with individual weight of 102.59 g, SGR of 2.78% body-weight/day and FCR of 1.09. The hybrids between female Nirwana and male blue tilapia  revealed a positive value of heterosis on the weight and length characters, i.e. 0.84% ​​and 2.13%, respectively. It was mean that the hybrids to have traists superior to those of either parent.