Kolkata, Feb 6 (IANS): The research on the captive breeding of Bengal's favourite fish hilsa in saline tank water continues to hit roadblocks as the young fries are not surviving, said an official from the state's fisheries department.

"The research is going on from late 2013 in Barrackpore and Kakdwip. However, the fries (young fishes) are not surviving to maturity," Saptarshi Biswas, a scientist at the state government's directorate of fisheries told IANS.

According to Biswas, it will take another seven to eight years for the research to yield fruitful results.

"So far the fries are dying before reaching maturity and it may take another seven to eight years for the research team to succeed," he said.

The Central Institute of Freshwater Aquaculture, aided by the central government, has been researching on developing the exotic fish under "controlled environment".

The need for captive breeding of the fish, considered a delicacy in Bengali cuisine rose on account of the rapid decline of the fish's numbers recently and the imports from Bangladesh dwindling.

Also, captive breeding of the fish would ensure normalcy of prices in the market and it's availability throughout the year. Retail prices of hilsa in the city vary between Rs.600 to Rs. 1,500 a kg depending on the size of the fish. Also, the fish is seasonally available during the monsoons.

The state government had initiated a variety of measures to breed the fish in captivity as well as protect the natural habitats of the fish. It also offered huge subsidies to fishermen to restrain them from catching the exotic fish during the breeding season.

The Institute of Aquaculture in Kakdwip is presently experimenting with changing the salinity content and the diet for the fries to help them reach maturity - the age when it can be harvested.