Study on selectivity of mesh size of cod-end of trawl in the East China Sea region

A field investigation was conducted from 1 April to 30 October 2001 in the East China Sea. The investigation adopted double bottom trawl, the net biggest mesh size is 4 m, the net stretched circumference of opening mouth is 400 m, and the net all length is 156.4m.The experimental methods adopted covered cod-end. This study analyzed the optimized mesh size of cod-end of trawl in the East China Sea region based on the experiment for the selectivity of cod-end mesh size of trawl used mainly for fishing T. haumela and P.ployactis. The results are as follows.1. Escape rate of 45 mm mesh size of cod-end on P. ployactis and T. haumela is lower and by-catch of the commercial juveniles of the same year is large number of the catch. 2. For 54 mm mesh size of cod-end, 50% selected body length of P. ployactis is less than the dominant body length group and the 50% selected body length of T. haumela enteredits dominant body length range. 3. For 65 mm mesh size of cod-end, the selected body length is basically consistent with the dominant body length. It is considered that the optimum mesh size of cod-end of trawl in the East China Sea region should be larger than 60 mm based on the comprehensive analysis.