OVER-WINTERING GROWTH PERFORMANCE OF MIXED-SEX AND MONO-SEX NILE TILAPIA Oreochromis niloticus IN NORTHEASTERN BANGLADESH

The study was conducted to assess the over-wintering growth performance of mixed-sex and mono-sex male tilapia, Oreochromis niloticus. The experiment was carried out with two treatments each with three replicates for a period of 6 months from October 2012 to March 2013 in the Field Laboratory Complex, Bangladesh Agricultural University. In the first treatment (T 1 ), mixed-sex tilapia was stocked in 3 ponds with a mean initial weight of 4.80±0.18 g. In the second treatment (T 2 ), mono-sex male tilapia was stocked in another 3 ponds with a mean initial weight of 4.81±0.20 g. Fish were fed at the rate of 6% of fish body weight at the beginning of the experiments, then the feeding rates were gradually reduced to 2% for the third month and finally increased to 3% for the rest of the period. Water parameters in terms of temperature, dissolved oxygen, pH, transparency, alkalinity, ammonia and nitrite were within the range of fish farming. After 6 months of culture period, mono-sex male tilapia attained a significantly (P<0.05) higher mean final weight and specific growth rate, compared to that of mixed-sex tilapia. However, there was no significant (P>0.05) difference of food conversion ratio and survival rate (%) values between the treatments. The benefit-cost ratio was calculated as 1.17 and 1.43 for mixed-sex and mono-sex male tilapia, respectively. The results suggested that it is possible to successfully culture tilapia during the winter period in Bangladesh, and the culture of mono-sex tilapia is more profitable due to its higher growth rate. OVER-WINTERING GROWTH PERFORMANCE OF MIXED-SEX AND MONO-SEX NILE TILAPIA Oreochromis niloticus IN NORTHEASTERN BANGLADESH