Minimal cod-end mesh of a pair trawl in the Yellow Sea

CHEN Ren-jie;LI Xian-sen;FAN Gang-zhou;ZHAO Xian-yong;ZHANG Guo-sheng;College of Marine Science and Environment,Dalian Ocean University;Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Key Laboratory for Fishery Resources and Eco-Environment,Shandong Province,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences;Function Laboratory for Marine Fisheries Science and Food Production Processes,Qingdao National Laboratory for Marine Science and Technology;

pair trawl with double wings and single cod-end;;proportion of juvenile fish;;escape rate;;release effect;;ecological effectiveness;;economic effectiveness;;minimal mesh size

The escape rate of main catches and release of juvenile fish were studied using a pair trawl with double wings and single cod-end by cover-nets with cod-end mesh of 40,54,60,70 and 90 mm in Haizhou Bay in the southern Yellow Sea in August 2017 in order to support the implementation and management of Natural Marine Fishing Gear Catalog and study the selectivity of cod-end mesh of pair trawl with double wings and single cod-end. A balance of ecological effectiveness and economic effectiveness was made with a mathematical modeling method. It was found that the escape rate of fish was increased gradually with the increment in cod-end mesh size,and that the release effect of juvenile fish appeared to be elevated significantly. The mesh size of cod-end was shown to be enlarged to more than 80 mm based on the ecological protection under the present fishery resources in the Yellow Sea. The remarkable release effect was observed at the mesh size of < 56 mm,and the significant loss of economic effectiveness was found at the mesh size of > 56 mm. Therefore it is suggested that the mesh size of 56 mm be of scientific reference to the standard of the minimum cod-end mesh size of pair trawl in the Yellow Sea in order to balance the ecological effectiveness and economic effectiveness.