On the selective action of the cod end meshes of a shrimp trawl

Selectivity studies using cod end and cover to determine the optimum cod end mesh size for commercial size groups of shrimps was carried out at Cochin during 1963-64 fishing season. The normality of the result was checked by trouser cod end method. Although the present investigation was mainly aimed to find out suitable cod end mesh size for commercial varieties of shrimps, five commonly occurring species of fishes were also taken. The 50% escape level, co-efficient of selectivity and selection factor for all the species were worked out. From the findings, the authors stress the necessity of increasing the cod end mesh size from the present condition (25.4 to 31.70 mm) to 41.65 mm fabricated mesh size to avoid depletion of the natural population.