| Portunidae crab pot mainly catch Portunus trituberculatu, it is one of the most importmant marine fishing methods and plays the more important role in the marine fisheries of Zhejiang Province.Based on the dynamic monitoring data of Portunidae crab pots in 2001~2010 and the productive test data of the selective Portunidae crab pots in 32o30′~33o N, 124o~124o30′E during Nov. 2009, the ecology and biological characterization of Portunus trituberculatu, the current situation of Portunidae crab pot fisheries of Zhejiang Province, the fishing gear and method was analyzed. Then, in allusion to the current common used Portunidae crab pots (pot diameter 60 cm, height 25 cm, mesh size of clothing net 2a = 32 mm) are causing the serious damages on the juvenile crab resources of Portunus trituberculatu, a selective crab pot with escape gap opened on the framework for juvenile crab was designed. The results showed that the proper height of the escape gap is almost the same as the largest shell height of P. trituberculatu. If the minimum criterion of catchable body weight was 125g, the height of selective escape gap was 33 mm which can be estimated from the relationship between shell height and body weight; The selection curve of the escape gap can be described by piecewise function without 50% selective shell height, which is different from"Logistic selection curve"that usually used to describe the mesh selection curve of trawls, shrimp trawl, stow net and eel pot with 50% selective length. The selective rate in number can be denoted by the average selection rate of shell height groups, by Chi-Square(χ2) test, while its values of productive tests were smaller than 20%, it presents higher release rate; however, it shows almost no effects caused by the size of gap for escaping, on the survival of juvenile crab were observed. At the same time, we suggest the minimum size of catchable criterion could be referenced for the setting up of the fishery regulation.
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