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Cod-end mesh size selection for rockfish and flatfish of the US West Coast

机译：美国西海岸石鱼和比目鱼的鳕鱼端网眼尺寸选择

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Size selection characteristics of five cod-ends (114-mm, 127-mm and 140-mm diamond, and 114-mm and 127-mm square meshes) were tested through alternate-haul experiments performed under commercial fishing conditions in 1988-1990, with a 76-mm diamond mesh cod-end as standard. Overall selectivity curves for five flatfish species (arrowtooth flounder, Atheresthes stomias, and Dover, Microstomus pacificus, english, Parophrys vetulus, rex, Glyptocephalus zachirus, and petrale sole, Eopsetta jordanii) and five rockfish species (shortspine thornyhead, Sebastolobus alascanus, Pacific Ocean perch, Sebastes alutus, and widow, S. entomelas, yellowtail, S. flavidus, and canary rockfish, S. pinniger) were estimated using the Share Each Length Catch Total (SELECT) method and four types of selection ogives (logistic, probit, negative extreme value and Gompertz) on weighted pooled length distributions. The negative extreme value curve provided the best fits to more than half of the data, implying asymmetry in the retention of small and very large fish. Lengths of 50% retention increased with increasing mesh sizes for both the diamond and square mesh cod-ends, with rockfish providing on average larger values than flatfish. In general, the 114-mm square mesh cod-end retained more small fish than the other cod-ends. Thus, compared to the currently used 114-mm diamond mesh, it is not a good alternative to reduce discard or retention of immature fish. On the other hand, the 127-mm square and diamond, and 140-mm diamond mesh cod-ends reduced the retention of immature fish for many of the species. Thus, these cod-ends seem acceptable for biologically conservative management regulations.
机译：通过在1988-1990年间在商业捕鱼条件下进行的交替捕捞试验，测试了5个鳕鱼末端（114毫米，127毫米和140毫米钻石，114毫米和127毫米方形网眼）的尺寸选择特性，标配76毫米菱形网眼。五个比目鱼种类（箭齿比目鱼，食孔花和多佛，Microstomus pacificus，英语，Parophrys vetulus，rex，Glyptocephalus zachirus和petrale sole，Eopsetta jordanii）的总体选择性曲线和五个石鱼种类（短脊棘，y鱼，Sebastolobusala鱼）使用共享每长度捕获总数（SELECT）方法和四种选择对象（后勤，概率，加权合并长度分布上的负极值和Gompertz）。负极值曲线提供了与一半以上数据的最佳拟合，这暗示着大小鱼类的保留不对称。菱形和方形网状鳕鱼端的网孔尺寸增加时，保留长度的50％会增加，而石鱼的平均价值要比平鱼大。通常，114毫米见方的鳕鱼尾比其他鳕鱼尾保留了更多的小鱼。因此，与当前使用的114毫米钻石网相比，减少丢弃或保留未成熟鱼的方法不是一个好的选择。另一方面，127毫米见方的钻石和140毫米菱形网眼的鳕鱼端减少了许多物种中未成熟鱼类的滞留率。因此，这些鳕鱼末端看来对于生物学上保守的管理规定是可以接受的。

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