Performance of common carp, Cyprinus carpio L. and Nile tilapia, Oreochromis niloticus (L.) in integrated rice–fish culture in Bangladesh

Abstract Irrigated rice fields have enormous potential for expanding the aquaculture production in rice producing countries. Two field experiments were carried out at the Bangladesh Agricultural University, Mymensingh, to optimize the productivity of integrated rice–fish systems using Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinus carpio L. Both experiments were laid out in a randomized complete block design with three replicates per treatment and regular rice monoculture as control. In the first trial, carp and tilapia were tested in single culture and in mixed culture with supplementary feeding at 2× maintenance level. The highest fish yield was obtained in the carp/tilapia mixed culture (586 ± 125 kg ha − 1 ), followed by tilapia alone (540 ± 65 kg ha − 1 ), and carp alone (257 ± 95 kg ha − 1 ). Carp had significantly lower yield than the other two fish groups ( p − 1 ), followed by feed level I (776 ± 22 kg ha − 1 ), and the non-fed group (515 ± 85 kg ha − 1 ). Yield differences between the treatments were significant at p − 1 ) was obtained from rice–fish plots with regular urea fertilization. Various significant effects of fish on water quality parameters were observed. Fish decreased the dissolved oxygen (DO) and pH value compared to rice only, especially when supplementary feed was provided. Moreover, fish stimulated the growth of phytoplankton and increased chlorophyll-a concentration. In conclusion, carp/tilapia mixed culture with supplementary feeding was found to be optimal for maximizing the output from rice–fish culture.