Assessment of Carbon Budget under Semi-intensive Rearing of Reba, Cirrhinus reba (Hamilton, 1822) with Varying Stocking Density

A carbon budget was assessed for the rearing of Cirrhinus reba in 9 tanks for 45 days. Each tank was with an equal amount of 20 m2 (5m ×4m ×1m) water area. Three various Stocking densities are designed as @RS1: 1.0, RS2: 2.0 and RS3: 3.0 lakh fry per hectare, where RS referred to Reba stocking. Fish fry was fed with a 30% protein diet, and it was formulated by using various ingredients, viz. soybean meal, mustard oil cake, fish meal, wheat bran, broken wheat, corn flour and vitamin-mineral mixture in appropriate proportion. The tanks were fertilized uniformly by applying lime at 300 kg ha-1 and mustard oil cake at 750 kg ha-1. The recovery of carbon in fish was highest at 27.84% in RS2, followed by RS1 (25.07%) and RS3 (22.99%). At the end of the experiment, discharged water accounted for 43.03- 52.48% OC (organic carbon) of the total inputs. The varying stocking density affected the accumulated organic carbon in the discharged water (P<0.05). The experiment suggests that carbon utilization will be better at the desirable stocking density, @ 2.0 lakh per hectare, for a semi-intensive culture system of reba carp.