Catch retention and exclusion characteristics of 40 mm square mesh codend in trawls operated in Bay of Bengal

Abstract

Selectivity of trawl net is very poor, due to which, large quantity of fish are discarded. The discards often consist of juveniles of commercially important species, which may impact on the production of many of the commercial species. Diamond mesh codends are extensively being used in the Indian trawl industry. The shape of the mesh affects the selectivity of cod the codend. The mesh lumen of diamond mesh closes up under tension during towing operation and prevents escapement of fish. In the square mesh codends, the mesh remains open facilitating escapement of juveniles and small fishes. Knowledge on selectivity of codend mesh size for the commercially important species, in a given fishing area, is of great significance in determining the judicious exploitation of fish stocks. This study was undertaken to assess the fish retention and exclusion characteristics of trawls attached with 40 mm square mesh codend operated in Bay of Bengal. Square mesh codends of 40 mm were fabricated with 1.0 mm diameter polyethylene (PE) netting. Experiments were carried out onboard fishing research vessel CIFTECH-I (15.5 m LOA; 122 hp engine) in commercial fishing grounds off Visakhapatnam coast (17°40’-17° 42 lat.; 83°21’-83°30 long.), between 40 and 50 m depth. A 26 m multi-seam demersal trawl fitted with experimental square mesh codend was used and overall performance of the codend during the experimental tows was evaluated. Among the fishes caught, 81.4% was retained in the trawl codend while 18.2% was excluded. When the overall catch was considered, 17.8% excluded while 82.2% was retained. Characteristics of the species retained and escaped from 40 mm square mesh codend are detailed in the paper