Visakhapatnam :

At a time when fish stocks are declining globally due to various factors like climatic change and pollution, cage farming of fish on sea, an aquaculture technique, has thrown up an encouraging alternative that yields 10 times the fish catch as compared to fish reared in ponds or wild harvest in the sea.

This technique has also been taken up to great success in Vizag and other coastal districts of AP on an experimental basis by scientists of the Visakhapatnam Regional Centre of the Central Marine Fisheries Research Institute (CMFRI).

In Krishna district (Nagailanka) and Narsapuram (West Godavari), cage farming has been taken up in collaboration with fishermen, while in Vizag the cages in the sea along RK Beach are controlled by the CMFRI. There are six cages in Krishna, 10 in West Godavari and eight in Vizag district of AP. Plans are afoot to double the number of cages in Vizag soon given the good prospects, said CMFRI scientists.

Though open sea cage culture technology is a relatively recent activity in India, it is prevalent in other Asian countries. While lobster, Asian seabass, mullets, Cobia and Pearl Spot have been successfully harvested by CMFRI in various coastal waters in India, at present the Vizag centre of CMFRI is maintaining brood stocks of Orange Spotted Grouper, Indian Pompano, Snappers and Golden Trevally in cages that have all shown good growth and maturation, said scientists.

Under this procedure, fish rearing is done in an enclosed area in a natural aquatic environment where the water continuously flows and debris doesn’t accumulate, which is why there is no pollution or ammonia deposition as in the case of stagnant and low density water ponds. The young ones of fish and other aquatic species are kept, fed and grown to marketable size in these cages, which are of six metre diameter and made of high density polyethylene.

“Cage farming is in an infancy stage now, but the prospects for commercial exploitation are so good that we are planning to double the number of cages soon as well as expand to other neighbouring areas. At the end of the culture period, which ranges from six to eight months, three to five tonnes of fish are produced just from one cage,” said Subhadeep Ghosh, senior scientist and scientist-in-charge at CMFRI.

The biggest advantage of cage farming, according to Prof K Sujatha, chairperson, board of studies, department of marine living resources at AU, is that despite being a fish culture technique there is no need to change the waters as sea water continuously flows through the cages, there is some natural food easily available for the fish to feed on and there’s no need to put up any time or space-consuming infrastructure except the cages.

However, she pointed out that not all areas are suitable for cage farming. “There needs to be optimum depth of at least 10 metres from the shore, the sea should be more or less calm without high waves and currents where the cages are located. The salinity, pH, ammonia, nitrate should be all within permissible limits,” she explained.

source: http://www.timesofindia.indiatimes.com / The Times of India / Home> City> Visakhapatnam / TNN / July 17th, 2014