“The cage is made of two circular, high-pressure, high density polyethylene (HDP) pipes of diameter 210 mm. The cage itself is of 17 metres (outer ring) and 15 metres (inner ring) diameter, with the two metres being provided for the staff to walk around and work. The inner tube is again connected to elevated HDP tube ring of 110mm diameter at a height of about 1 metre with 16 T joints and 16 one meter pipes to support the structure,” explained Dr. Rao.

A bird net at the top prevents bird attacks. The net is tied to the inner ring and extended to the elevated tube to prevent the fishes from jumping out of the cage. An outer predator net prevents big fishes from entering the cage. The bottom of the net was kept in a position with suitable dead weights to maintain the cage structure.

The total weight of the cage was 1,500 kg and it was fabricated on the beach and launched manually. About 8,500 ‘Asian sea bass juveniles’, purchased from Mayiladuthurai in Tamil Nadu, are now being reared in the cage. “The cage experiment has excellent scope to increase the production of high-valued marine fish especially in view of conditions today when fishermen are returning with low catch.

According to Dr. Rao, each cage had a capacity to rear about 10 tonnes of fish yield and two cycles were possible in a year. Eventually, the CMFRI will also rear seer fish and pomfret which are in great demand in domestic markets. “The best thing about cage culture is that customers can buy live fish which is highly valued rather than preserved fish,” he said.

... contd.