Brackishwater carp culture in potentially waterlogged areas using animal wastes as pond fertilizers

In order to assess the possibilities of utilizing drainage effluents (salinity range 5.0-12.5 parts per thousand), fish culture experiments were carried out. Experiments on polyculture using cow dung (24 000 kg ha(-1) y(-1)) as pond fertilizer were conducted at five different salinity levels (0.3-8.5 parts per thousand). Studies have revealed that carp perform well in salinities up to 7.5 parts per thousand and reasonably high fish production has been obtained. Even though the ponds had a high trophic status, higher salinities (> 7.5 parts per thousand) appear to repress fish growth probably due to low disserved oxygen (DO), high BOD and high NH4-N. Experiments on monoculture of common carp (Cyprinus carpio) conducted at two different salinity levels (0.3-0.9 and 6.0-7.0 parts per thousand) using four different organic fertilizers (cow dung at 24 000 kg and 20 000 kg, poultry at 1500 kg, duck at 6000 kg and sheep/goat at 1500 kg ha(-1) y(-1) have revealed the highest fish growth to be in poultry-treated ponds, followed in decreasing order by duck and sheep/goat wastes. Similar trends in fish production were observed both in fresh- and salt-water ponds. However, fish production was lower in ponds having higher salinities (> 7.5 parts per thousand). Nevertheless, these studies indicated that inland saline waters can be utilized for fish culture. With minor modifications in the existing technology of fish culture in stagnant freshwater fish ponds, animal wastes could be used to fertilize brackishwater fish ponds.