Carbon and nitrogen distribution in some carp polyculture ponds of Andhra Pradesh, India

The excessive and indiscriminate uses of carbon (C) and nitrogen (N) through feed, fertilizers and manures in aquaculture ponds could play a vital role in the emission of greenhouse gases such as carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). Therefore, it is important to know about the distributions of N and C in the aquaculture ponds so that management strategies could be made for the minimum emissions and loss of these two nutrients in the fish ponds. The present investigation was thus undertaken for studying C and N balances in seven Indian major carp's polyculture ponds in Andhra Pradesh, India. The study revealed that overall, 8 % of carbon inputs from different sources was recovered in harvested fish, 61 % accumulated in the sediment and 0.5 % was discharged at harvested time during 165 days of culture period. About 16 % of nitrogen inputs from different sources was retained in harvested fish, 70 % accumulated in the sediment and 2 % was discharged at harvest time during 165 days of culture period. The results also showed that to produce 1 kg of fresh fish, 0.880.21 kg feed C and 0.080.01 kg feed N were fed, while to gain 1 kg C and 1 kg N in fish biomass, 6.561.60 kg feed C and 2.470.84 kg feed N was fed. Thus, in the present study about 6.5 times more C and about 2.5 times more N were used in the feed as fish feeding during the culture period.