The research was conducted to study the effect of stocking density on growth a nd production of endangered Feather back Notopterus chitala fry in earthen ponds for a period of 75 days from 1 August to 15 September 2014. The average pond size was 0.002 ha with water depth 1 m. The fishes were stocked in the hatchery complex of University of Rajshahi with three treatments group each having three replicates. The average initial fish weight and length was 6.00±0.5g and 3.19±0.34 cm, respectively. Three stocking densities were maintained at 14820 fishes ha-1 (T1), 13585 fishes ha-1 (T2) and 12350 fishes ha-1(T3). Fishes were fed same diet with 27.5% protein in three different treatments consisting fish meal (25%), rice bran (20%), wheat bran (20%), maize bran (13%), mustard oil cake (25%) and vitamin premix (2%) at the rate of 8% body weight. The mean value of weight gain (g) was the highest (20.33±0.00) in T3 and lowest (15.32±0.009) in T1. Specific growth rate (SGR) was also the highest (1.64±0.001) in T3 and lowest (1.41±0.008) in T3. Significant difference was found for the mean values of weight gain and SGR. The survival rate of N. chitala was 82.33±1.20, 87.67±1.45, 94.50±1.50 in T1, T2, T3, respectively. The highest survival rate (94.50) was found in T3. The highest production (300.78±1.62 kg ha-1) was found in T3 followed by T2 and T1. Despite of this, consistently higher CBR (cost benefit ratio) was found in treatment T3 (1.8) than in treatments T2 (1.46) and T1 (1.2).

Keywords: Stocking density, endangered, Notopterus chitala, survival rate, production

Fish cage culture allows intensive production in waterbodies without conventional preparation for aquaculture.Considering the importance and prospects of cage culture in Bangladesh, the present experiment was undertaken to study the effect of stocking density on growth performances and production potential of tilapia (Oreochromisniloticus) under cage culture conditions and to develop a suitable method of tilapia cage culture in inland open water body like Old Brahmaputra River. Three stocking densities (100, 150 and 200 fish m-3) of 2.78 g mean initial individual body weight of fingerlings in three different treatments (T-100, T-150 and T-200) each with three replicates were used. The fishes were supplied with high protein (30%) commercial feed at 10% of body weight twice daily. Water quality parameters namely transparency, temperature, pH, dissolved oxygen, phosphate were found within the suitable limit for fish culture.The result of the present study showed that the fish in the treatment T-150 resulted the best individual weight gain (90.72g), average daily gains (0.67 g), percent weight gains (3263%), specific growth rates (1.13%day-1) and the net production rates (13608gm-3135 days-1)followed by treatments T-100 and T-200, respectively.The net yield and growth performances showed a significant difference with increasing stocking density (P<0.01). The most effective stocking density was150 fish m−3 cage for Nile tilapia considering growth performances and production potential. Therefore, it can be concluded the growth performance of Nile tilapia is density dependent.

Keywords: Cage culture, stocking density,growth performance, production, Oreochromisniloticus