EVALUATION OF OREOCHROMIS-NILOTICUSXO-AUREUS HYBRID PROGENY OF DIFFERENT GEOGRAPHICAL ISOLATES, REARED UNDER VARYING MANAGEMENT REGIMES

Ten Oreochromis niloticus x O. aureus hybrids, progeny of different ge ographic isolates, were evaluated in polyculture with common carp, sil ver carp and grass carp. Traits tested included growth rate, survival, yield and proportion of males. The hybrid combinations 0. niloticus ' Nile' (Egypt) x 0. aureus 'Mehadrin' (Israel), and a niloticus 'Ghana- 74' x a aureus 'Nile' showed similar or better performance compared to the 'Ghana-74' X 'Mehadrin' hybrid developed earlier at Dor. This sug gests that the 'Nile' strains of both a niloticus and a aureus are pot ential candidates for commercial hybridization. The low proportion of males (30%) obtained with a niloticus 'Ghana-88' x a aureus 'Mehadrin' crosses suggests that the later introduction from the Volta River dif fers from the 1974 introduction.