GROWTH PERFORMANCE OF RIVER BASED CAGE TILAPIA, OREOCHROMIS NILOTICUS (LINNAEUS, 1758) FARMING UNDER DIFFERENT STOCKING DENSITIES

Abstract

This study was conducted to observed the growth performances of cage culture of tilapia (Oreochromis niloticus) under different stocking densities through length-weight (LW) relationship technique and condition factor (K) of O. niloticus caught from three treatment (T1, T2 and T3) in cage culture from February to October, 2017 in the Atrai river of Dinajpur, Bangladesh. The fish were stocked in truplicate of three treatment cage, with stocking densities of 500,600 and 700 per cage (20ft×10ft) respectively. Fortnightly 15% fish were collected from each cage for measuring the body weight and length. The fishes were ranged from 5.842-33.274 cm, 7.62-33.25 cm and 7.874-32.258 cm in length, while weight ranged 8.1-690 g, 8.3-685 g and 10.7-673 g for Treatment 1, Treatment 2 and Treatment 3 respectively. These results showed that the growth patterns of O. niloticus were described by the formula. Ln BW = 3.0(lnTL) -3.835, lnBW = 2.971(lnTL)-3.76 and ln BW = 2.91(lnTL)-3.723 for Treatment 1, Treatment 2 and Treatment 3 respectively. The value of the regression co-efficient (b) obtained for the length-weight relationships as 3.0(isometric growth), 2.971 (negative allometric) and 2.961 (negative allometric) for Treatment (T1, T2 and T3) cage respectively. In case of O. niloticus there is not significant different observed (P>0.05) between the slope of the three Treatment (T1, T2 and T3). The value coefficient of determination (R2 ) was, 0.931, 0.885 and 0.915 for Treatment 1, Treatment 2 and Treatment 3 respectively. In this study, the mean value of condition factors K was 2.24±0.51, 2.23±0.72 and 2.20±0.64 for Treatment 1, Treatment 2 and Treatment 3 respectively. Condition factors K were greater than 1 in all Treatment indicates that O. niloticus were in good condition and healthy and suitable for cages culture fish. Moreover, growth parameter: asymptotic length Lα were 33.27,33.20 and 32.26 and also founds as growth coefficient k were 0.51, 0.48 and 0.41 for Treatment 1, Treatment 2 and Treatment 3 respectively while the growth performance index, Ø as highest (2.75) in Treatment 1 and followed by Treatment 2 (2.72) and then (2.63) in Treatment 3 respectively. The survival rate specific growth rate production higher in treatment 1 than other treatments. The result showed that lower stocking densities higher growth performance in cage culture system.