Document Type: Original Article
Department of Aquaculture, Fisheries and Marine Environment, Food Resources and Marine Sciences Division, Kuwait Institute for Scientific Research, P.O.Box 1638, 22017 Salmiyah, Kuwait
In all-male culture of the non-improved tilapia strains based on manual sexing, females are discarded because their growth is slower than that of males which results in a wastage of effort and undue expenses in growing the females to sexable size. This study was, therefore, conducted to compare the yield and growth performance of monosex culture of the Genetically Improved Farmed Tilapia (GIFT) and non-improved strains (NS) of the Nile tilapia, Oreochromis niloticus. Males and females having mean weights of 120.4 and 96.5 g were stocked separately in 0.43 m3 tanks at 100 fish/m3 and fed commercial pellets (35% protein) for 158 days. Results showed that GIFT males had significantly higher mean weight (628.4 g), daily growth rate (3.19 g fish/day), specific growth rate (1.03%/day), gross yield (59.3 kg/m3) and better feed conversion ratio (1.4) than the other treatments, whereas the non-improved females had the lowest growth parameters, survival, gross yield and the poorest feed conversion ratio. Results also indicated that non-improved males and GIFT females had similar growth rates (2.16 and 1.92 g/fish/day, respectively). These results indicate that routine size-grading and manual sexing of the GIFT strain between production phases would result in populations of a single sex majority and uniform size. Intensive culture of GIFT populations would greatly eliminate the unwanted recruitment and the need to discard the females as is the case with the slow-growing non-improved females, and thus increase production rate and profitability.