The poly house set up at the Assam Agriculture University in Jorhat. Telegraph picture

Jorhat, Nov. 24: The low breeding and stunted growth of fish owing to adverse environmental factors in the state has prompted the Fisheries Research Centre at the Assam Agriculture University here to set up a poly house to advance their breeding period.

This is the first structure constructed in the country where the climate can be controlled and the water kept warm for advancing the gonadal (reproductive organs) maturation of cultivable carps like rohu and bahu.

Bibha Chetia Borah, head of the centre, said one of the causes for low fish production was the adverse environmental condition during the peak period of fish breeding and growth, which led to import of fingerlings from outside the state.

“Fish being cold-blooded are more dependent on environmental temperature. Generally, warm water fish like rohu and bahu (catla) show a high metabolic rate in higher temperatures. However, the cold and dry climate during the prolonged winter in Assam is not ideal for fish breeding. It only has short periods with optimum ambient temperature required for the growth and other biological processes like gonadal maturation and reproduction in these cultivable fish,” she said.

The poly house has been built at a cost of Rs 50 lakh.

Borah said despite the rapid advancement in fish culture technology and the subsequent increase in production potential in other parts of the country, fish production in Assam has not gained the desired momentum for the climate factor.

The scientist said the maturation cycle in the state starts in October and completes in July, while the breeding season commences in April-May and continues till July-August and peaking during May-June. However, in many other states, the breeding season was quite early in February and hence, by the time the seed producers in Assam start breeding, the fish seed market gets flooded with fry and fingerlings from outside the state, she added.

“The imported fish seed is often of low quality as it gets weakened during transport through long distances, handling stress as well as malnutrition,” Borah said.

“In order to study the feasibility of advancing gonadal maturation and advance the breeding process through increase in environmental temperature, the poly house covered with an ultraviolet stabilised low density polyethylene film was installed over a plastic pond with accessories to enhance and retain the water temperature during winter as well as other parameters,” she said.

Earlier, studies have shown that fish growth was enhanced in plastic covered tanks where the water temperature was higher. “The objective of this study is to see the techno-economic feasibility of the system for advanced breeding in order to ensure the availability of quality fish seeds at the right time of stocking (March-April) for fish farmers in Assam,” she added.