Development of fingerling production techniques in nursery ponds for the critically endangered reba carp, Cirrhinus ariza (Hamilton, 1807)

Özet

Growth, survival and production performances of Cirrhinus ariza fingerlings were evaluated for 8 weeks in nine earthen nursery ponds having an area of 0.012 ha each with an average depth of 1.0 m. Three stocking densities of hatchlings each with two replications were tested in treatments. Four-day-old hatchling stocked at 0.8 million ha-1 was defined as treatment-1 (T1), 1.0 million $ha^{-1 }$ as treatment-2 ($T _2$) and 1.2 million $ha^{-1 }$ as treatment-3 ($T _3$), respectively. Hatchlings in all the experimental ponds were supplemented with wheat flour for the first 7 days, finely ground mustard oilcake for the next 7 days and a mixture of rice bran and mustard oilcake (1:1) for days 15 to 56. Feeding was done at the rate of 15 kg/million hatchling $day^{-1 }$ for the first two weeks, 20 kg for the second two weeks, 25 kg for the third two weeks and 30 kg for the fourth two weeks. The physico-chemical and biological parameters of pond water were within the suitable range for fish culture. Growth in terms of final weight, final length, weight gain, length gain and specific growth rate, and survival of fingerlings was significantly higher in $T _1$ where stocking density were 0.8 million hatchling $ha^{-1 }$ than those obtained from $T _2$ (1.0 million $ha^{-1 }$) and $T _3$ (1.2 million $ha^{-1 }$), respectively. Feed conversion rate was the lowest in $T _1$ followed by T2 and the highest in $T _3$ (P<0.05). Gross and net productions of fingerling were higher in T1 than T2 and $T _3$, respectively (P<0.05). Higher number of fingerlings was produced in $T _3$ than those in $T _2$ and $T _1$ (P<0.05). Even then, consistently higher net benefits were obtained from $T _1$ than those from $T _3$ and T2. Among the treatments evaluated, 0.8 million hatchling $ha^{-1 }$ ($T _1$) was the best stocking density considering the highest growth, survival, production and net benefits of the fingerlings of C. ariza in nursery ponds.