The Research Of Stow Net Minimum Mesh Size In Zhoushan City

In accordance with the Zhoushan stow net catch survey data analyzed stow net catch species composition and diversity of features in September-October 2014, this survey network stow catched a total of 30 species, including 18 species of fishes, seven kinds of shrimps, five kinds crabs, among them, Trichiurus haumela, Pseudosciaena polyactis Bleeker,Pampus argenteus and crustaceans accounted for 47.83%、24.78%、 2.42%、19.44% of total output, respectively, other fish varieties, accounting for 5.53%, 4409 samples were randomly selected, fishes accounted for 91.12% of the total mass, shrimps accounted for1.37%, crabs accounted for 7.52%. After calculation and analysis, the diversity index of species surveyed is high, the sea had more abundant species, but from the Trichiurus haumela and Pseudosciaena polyactis Bleeker proportion of juveniles, the stow net fishing for Trichiurus haumela and Pseudosciaena polyactis Bleeker juveniles Zhoushan resources are still more seriously damaged, survey stow net codend mesh size of 40 mm net, in the widespread use of stow, is clearly unreasonable at Zhoushan city.On the basis of test statistical data,catch of species identification of the test results,about set nets in November 2014 including a total of 27 kinds of fishing catches, fishes accounted for 74%, Trichiurus haumela and Pseudosciaena polyactis Bleeker accounted for36.57% and 17.44 %, which are the test nets two main catches. Analysising the Trichiurus haumela and Pseudosciaena polyactis Bleeker in the codend mesh size of 51 mm and 56 mm when set nets and net anal length(body length) distribution. The results showed that the two mesh size for Trichiurus haumela good selectivity, 56 mm mesh size better choice, two mesh size of Pseudosciaena polyactis Bleeker less selective, 56 mm mesh size choose better.Logistic curve model based on selectivity, combined with maximum likelihood estimation method parameter estimates obtained under different mesh size codend selectivity curve of Trichiurus haumela and Pseudosciaena polyactis Bleeker, analyzes stow net selectivity different mesh size net bag. The results showed that codend mesh size is 51 mm, while 56 mm,Trichiurus haumela and Pseudosciaena polyactis Bleeker selection range 3.026,4.361,50%respectively 2.166,2.690 and select body length 18.378 cm respectively, 20.641 cm and9.540 cm, 13.079 cm, select coefficients were 0.368,0.375 and 0.191,0.238 SF. By codend mesh size m in length and 50% choose L0.5 linear fit was:50% chose Trichiurus haumela length linear relationship between L0.5 codend mesh size m corresponding to:L0.5= 0.452 m – 4.256Pseudosciaena polyactis Bleeker codend mesh size m corresponding to 50% of body length to select a linear relationship between the type L0.5:L0.5 = 0.707 m – 25.85L0.5 positively correlated with Trichiurus haumela and Pseudosciaena polyactis Bleeker codend mesh size m into, through the analysis, if L0.5 as stow net catchable size,considering the two juvenile fish conservation under the premise of combining and fishery production, draw better than 56 mm mesh size 51 mm mesh effect.Finally discussing Zhoushan stow net minimum mesh size, and proposed to strengthen the stow net fisheries management, fishing gear, uniform implementation of reforms and the implementation of the stow net fishing subsidies policy recommendations.