Evaluation of minor carps intercropping in carp polyculture vis-a-vis other grow-out cropping patterns of carp farming

One year grow-out evaluation of four cropping patterns of carps, viz. control: single stock single harvest (SSSH); T-1:intercrop of minor carps and Indian major carps (IMC); T-2:single stock multiple harvests (SSMH); and T-3:multiple stock multiple harvests (MSMH) was conducted in eight earthen ponds (0.09 ha each). Ponds were stocked with three IMCs (catla, rohu and mrigal) at 1:1:1 ratio at 10,000 fingerlings/ha combined density. T-1 was additionally stocked with 10,000 fingerlings/ha of minor carps (Puntius gonionotus, Labeo fimbriatus and Puntius sarana), while T-2 with additional 10,000 fingerlings/ha of the IMC. Periodic removal of partial biomass ensured prevalence of better water quality in treatments (higher water pH, higher dissolved oxygen and reduced inorganic nutrients). It helped to improve fish growth as average harvested weight of rohu and mrigal remained similar in treatments despite the presence of greater inter- and intraspecific competitions in intercrop and SSMH, respectively, and periodic stocking of younger juveniles in MSMH. Catla showed significantly higher growth in MSMH. The biomass yield in intercrop, SSMH and MSMH were 21%, 17% and 24% higher than SSSH, but the respective net incomes were 32.9, 21.3 and 56.5% higher. Partial harvest also helped reducing FCR in the order T-3