CAGE CULTURE OF NILE TILAPIA, Oreochromis niloticus IN ATRAI RIVER OF DINAJPUR: LIMNOLOGICAL ASPECTS AND GROWTH PERFORMANCE

Abstract

In Bangladesh cage culture began in a trial basis at various research institutes and universities in the late 1970’s (DoF, 1991). Now a days, river based cage culture are getting popularity in different places of Bangladesh. However, information related to water quality and production performance of river based tilapia farming is scanty. The experiment was carried out for a period of nine months from February to October 2017 in nine experimental cages situated in Atrai river. Several limnological parameters such as physical (air and water temperature, transparency, water level), chemical (dissolved oxygen, alkalinity and pH) and biological (phytoplankton and zooplankton) were observed from three treatments. Sample was collected fortnightly from each treatment. Collected samples were analyzed in the laboratory of Department of Fisheries Management, Faculty of Fisheries, Hajee Mohammad Danesh Science and Technology University, Dinajpur. ANOVA showed a significant variation (P<0.05) in physico-chemical parameters among the treatments. pH was significantly variable among the treatments. A total of 68 genera of plankton were identified of which 56 genera was phytoplankton and 12 genera was zooplankton. Phytoplankton was dominated by chlorophyceae and zooplankton dominated by rotifera. Stocking density was considered one of the important factors which was affecting the fish growth. Tilapia fry with an average weight of 61.21 ± 21.41 g, 57.74± 18.83g and 56.18 ± 24.95g (mean ± SD) were stocked in 9 floating net cages (6.1 m × 3.04 m × 1.5 m) in T1, T2 and T3. After 270 days of the experiment, growth in terms of weight gain, percent weight gain, average weight gain, specific growth rate of fish, survival rate and production were significantly higher in treatment 1 than those of treatment 2 and treatment 3. Gross and net production were higher 288.26 kg and 257.66 kg in treatment 1. The results concluded that lower stocking density was the best for tilapia culture in cages on the basis of growth which might be technically feasible and economically viable. The findings of the study will be helpful for selecting the optimum suitable stocking density of tilapia fish in river based cage farming. Moreover, the result of the study may be provided some valuable information of the water quality and production performance of tilapia in cage culture.