THIRUVANANTHAPURAM: In a major initiative that can help preserve marine wealth and ensure its sustainability, Central Institute of Fisheries Technology (CIFT) and World Wide Fund for Nature (WWF) have conducted studies which proved that using square-mesh cod end in bottom trawls is beneficial not only for fishers but also for ecology. A recent study by the team in Sakthikulangara fishing harbour, Kollam, proved that replacing traditional diamond mesh cod-end with square mesh codend reduced the juvenile fish and bycatch, that is, fish or other marine species which get caught unintentionally, thereby putting forth a sustainable method of fishing.
The field trials conducted by the organisations involved a comparison of hauls caught by identical bottom trawls which were fitted with square mesh cod-end and diamond mesh codend. The study was done using a 25 mm square mesh cod-end which is used for fishing shrimp varieties. Currently, two types of square mesh cod-end are allowed -- 35 mm for fishes and 25 mm for shrimps. “Only the cod-end portion of the trawl net was changed and it is a one-time investment. The bycatch and juvenile fish catch from trawlnets are less when we use square mesh fitted trawlers.
The uniform-sized shrimp catch will also increase the price for shrimp when compared to shrimps caught using diamond mesh cod-end,” said Madhu V R, principal secretary, CIFT, who designed the study. The study involved two trawlers, with the same dimensions and engine power with only change in the cod-end portion of the trawl net. “The catch from the trawler fitted with square cod-end gave a uniform and good haul. It avoids juvenile fish and other debris. Further, there was a better catch and fishers save a lot of time which is otherwise spent on removing the debris and juvenile fish.
While using the square mesh cod-end, the juvenile fishes can escape and a thirty per cent survival rate has been observed for juvenile fishes, “ he said. All Kerala Fishing Boat Owners’ Association, Marine Stewardship Council and fisheries department too were associated with the study. “It was crucial that we could impress upon the fishers how beneficial the square mesh cod is for them. Bycatch reduction is a major component. It’s a sustainable method of fishing and protects biodiversity,” said Vinod Malayilethu, team leader, Marine Conservation Programme, WWF India.
As the cod end mesh size is changed from diamond to square, juvenile fishes are able to escape. “The principle here is that in a diamond mesh, as the net drags through, the mesh diameter stretches and becomes smaller. Even if you stretch a square mesh, the diameter remains the same. So the juvenile fishes which get caught accidentally can easily move out of the square mesh,” says marine biologist Vinod.