Author(s): Mt. Shamima Yasmin, M Shadiqur Rahman, KM Abdul Halim, M Alam Khan, Farida Yeasmin, KM Hasanuzzaman, SK Dabnath, M Mamunur Rahman and M Rafiqur Rahman

Abstract: The research work was conducted in six nursery ponds of 0.01 ha each with 4 days old mahseer, Tor putitora spawn at three different stocking densities viz., 1.50, 1.75 and 2.00 million spawn/ha each having two replicates. Fries were fed same diet of MEGA fish feeds in three different treatments containing 40.57% crude protein (pre-nursery feed) for the first 14 days and 35.52% crude protein (nursery feed) for the second 14 days. The feeding rate was 20 kg/ million spawn/ day for the first 2 weeks and 24 kg/ million spawn/ day for the second 2 weeks. The physico-chemical characteristics of pond water were measured weekly. The mean values of some water quality parameters such as temperature (°C) were 22.50±0.35 (T1), 22.69±0.39 (T2), 22.81±0.37 (T3); transparency (cm) 28.38±2.00 (T1), 41.88±2.45 (T2), 52.25±1.93 (T3); dissolved oxygen (mg/l) 4.90±0.21 (T1), 4.42±0.15 (T2), 3.72±0.07 (T3); pH 7.34±0.22 (T1), 7.21±0.23 (T27.53±0.21 (T3) and alkalinity (mg/l) 92.38±3.06 (T1), 112.13±6.48 (T2), 117.38±5.75 (T3) from 28 days, respectively. The ranges of water quality parameters were suitable for fry and fingerling rearing. The highest weight gain was recorded in T1 (1.79±0.03) and the lowest in T3 (1.46±0.04). The mean value of final weight (g) was 1.81±0.02, 1.71±0.02 and 1.52±0.03 in T1, T2 and T3, respectively. Significantly lower specific growth rate was found in T3 (7.23±0.04) than T1 (7.54±0.02) and T2 (7.45±0.02). Fingerlings in T3 produced significantly higher food conversion ratio (0.61±0.10) than T1 (0.44±0.07) and T2 (0.48±0.04). The survival rate of mahseer was 63.05±0.59% (T1), 60.38±0.51% (T2) and 55.19±0.70% (T3), respectively. Significantly higher number of fingerlings was produced in T3 (1103700±10608) than T1 (945675±9320) and T2 (1056650±10314), respectively. But the simple cost benefit analysis showed that higher net benefits were obtained in T2 (TK. 13, 09,968) where the ponds stocked with 1.75 million spawn/ha. Hence, it seems that, among the three tested stocking densities, 1.75 million spawn/ha is the most efficient stocking density for primary nursing of mahseer spawn.

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