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Evaluation of separation performance on selective fishing device for fisheries resources management.

渔业资源管理选择性捕捞装置分离性能评价。

基本信息

批准号：
14560145
负责人：
TOKAI Tadashi
金额：
$ 2.05万
依托单位：
Tokyo University of Marine Science and Technology (2004)東京水産大学 (2002-2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The size selection curve of fine mesh for Anchovy larvae were estimated by using an extended SELECT model for analyzing size frequency distribution constructed from pockets catches and sampling the cod-end catches, and from covered-net experiments. Higher catch volume were decreasing escape opportunities and selectivity.Capture process of clam by dredge was modeled. First, Master curve equation of size selectivity of dredge bagnet for a clam, equilateral Venus Gomphina melanaegis was estimated by using cover-net fishing experiments with test bagnets of several mesh sizes. The size selectivity of dredge bagnet was a kind of contact selection of bagnet mesh. Second, The effect of various tooth-spacing on the contact selection and the net-mouth available selection of a dredge for the equilateral Venus clam Gomphina melanaegis was evaluated by applying a contact-probability model based on the SELECT method to the data of paired-gear tests with a control dredge of 12mm tooth spacing and fou … More r test dredges of tooth spacing 16,20,24,and 35mm. A master selection curve was estimated to be s(R)=exp(-11.23R+4.799)/[1+exp(-11.23R+4.799)], where Ris Id, the ratio of the shell length 1 to the tooth spacing d. The shell width of 50% retention was slightly smaller than the tooth spacing, which means that size selectivity of teeth was a type of contact selection which was dependent on the tooth spacing. Contact probability δ of the clams coming into contact with the teeth were 0.625,0.467,0.563,0.670,and 0.976 for tooth spacing 12,16,20,24,and 35mm, respectively. This indicates that some clams entered the dredge bagnet without contacting the teeth as the sand clogging the tooth spacing carried them into the bagnet. Available selection curve of the dredge net-mouth with teeth was obtained as δ s(R)+1-δ and examined in terms of the minimum landing size of the Venus clam.A method for assessing species-separation performance of size-selective fishing gear is presented. Species composition in catch by selective fishing gear is often discussed to assess the performance of the selective device. However, the catch number (and weight) depends on body size composition in the population when the fishing gear has size selectivity, and thus species composition varies and is not suitable as gear performance index. In fact some selective devices, e.g.mesh panel, grid, and escape-vent have been reported to be size-selective. When a selective device has retention probabilities of body size 1, r_w(l) and r_u(l) for wanted and unwanted species, respectively, separation efficiency p(l_w, 0l_u) between l_w size wanted and l_u-size unwanted species is defined as r_w(l_w)+[1-0r_u(l_u)]-1. The efficiency is 1 when wanted species is completely retained and unwanted is excluded as expected, and is -1 in the exact opposite of the expectation. The equation implied that the separation efficiency is likely to be high as there is larger difference in body size between the two species. Less

采用扩展的SELECT模型，对由囊网渔获物和网衣渔获物构建的鱼体尺寸频率分布进行分析，估算了鳀鱼幼鱼对细网尺寸的选择曲线。较高的捕获量降低了文蛤的逃逸机会和选择性。首先，通过几种网目尺寸的试验袋网的覆盖网捕捞试验，估算了网对蛤类的尺寸选择性主曲线方程。挖泥船袋式网的粒度选择性是一种网目的接触选择。其次，应用基于SELECT方法的接触概率模型，对12 mm齿距和4 mm齿距的对照耙齿的成对试验数据进行了分析，研究了不同齿距对网纹蛤Gomphina melanaegis的接触选择和网口有效选择的影响。结果表明，齿距对网纹蛤Gomphina melanaegis的接触选择和网口有效选择的影响是显著的。 ...更多信息 r齿距为16、20、24和35 mm的试验挖泥船。主选择曲线估计为s（R）=exp（-11.23R+4.799）/[1+exp（-11.23R+4.799）]，其中R为Id，壳长1与齿间距d的比值。50%固位时的壳宽略小于齿间距，表明牙齿的尺寸选择性是一种依赖于齿间距的接触选择。当齿距为12、16、20、24和35 mm时，蛤与牙齿接触的接触概率δ分别为0.625、0.467、0.563、0.670和0.976。这表明，一些蛤进入疏浚袋式网没有接触牙齿，因为沙子堵塞齿间距进行袋式网。通过分析，得到了带齿网口的有效选择曲线为δ s（R）+1-δ，并以文蛤的最小上岸尺寸为依据进行了检验，提出了一种选择性网具分选性能的评价方法。经常讨论选择性渔具渔获物的物种组成，以评估选择性装置的性能。然而，当渔具具有尺寸选择性时，渔获量（和重量）取决于种群中的身体尺寸组成，因此物种组成变化，不适合作为渔具性能指标。事实上，一些选择性装置，例如网格板、格栅和逃生口，已经被报道为具有尺寸选择性。当选择性装置具有主体尺寸1的保留概率时，r_w（l）和r_u（l）分别用于需要的和不需要的物质，l_w尺寸的需要的和l_u尺寸的不需要的物质之间的分离效率p（l_w，0l_u）被定义为r_w（l_w）+[1-0r_u（l_u）]-1。当期望的物种被完全保留并且不期望的物种被排除时，效率为1，并且与期望正好相反，效率为-1。该方程表明，当两个物种的体型差异较大时，分离效率可能较高。少