Different stocking densities and species combinations effects the growth and production in carp polyculture

A comparative experiment was undertaken to assess the effectiveness of different carp species i.e., Rohu (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus cirrhosus), and Silver Carp (Hypophthalmicthys molitrix) with variable stocking densities. Three treatments each with three replicates were maintained and the stocking densities of carps were 40, 80, and 120 fish/decimal in T1, T2, and T3, respectively. The stocking ratio of Rohu, Catla, Mrigal, and Silver Carp was 2:1:2:1. The experimental diet included rice bran (25%), wheat bran (25%), fish meal (25%), and mustard oil cake (25%), with a total protein content of 28%. This dietary supplement was administered twice daily. The fish were supplemented with 5% of their body weight for the first month, 4.5% for the next three months, and 2% for the final two months. The water quality parameters i.e., pH, temperature, dissolved oxygen and transparency were measured every 14 days interval. In T1, Silver Carp obtained the highest weight (188.86±17.86g) followed by Mrigal (106.78±14.23g), Catla (74.0±3.80g), and Rohu (67.72±6.03g). In T1, Silver Carp also attained the highest length at 26.33±0.63 cm, followed by Catla at 14.40±2.10 cm, Mrigal at 14.09±0.89 cm, and Rohu at 14.07±0.59 cm, respectively. Nevertheless, both weight gain and length gain were lowest for all species in T3. The highest SGR% was found in T1 for Silver Carp (3.22±0.06), whereas the lowest SGR% was found in T3 for Catla (1.69±0.06). In addition, T2 yielded the highest production (3090.91±119.57 kg/ha), followed by T3 (2949.80±137.67 kg/ha) and T1 (2946.21± 129.00 kg/ha). The experimental findings suggest that, the stocking density of 80 fingerlings/decimal (T2) yielded the highest production in carp polyculture.