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Studies on mitigation measures and gear optimization for reduction of incidental catch of seabirds and sea turtles in tuna longline fisheries

减少金枪鱼延绳钓渔业误捕海鸟和海龟的缓解措施和渔具优化研究

基本信息

批准号：
14560144
负责人：
HU Fuxiang
金额：
$ 1.34万
依托单位：
Tokyo University of Marine Science and Technology
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 2003
项目状态：
已结题

项目摘要

In order to develop mitigation measures for reduction in incidental catch of seabirds in tuna longline fisheries, the hook sinking speed of branch lines used by Japanese tuna longline vessels was investigated, and an underwater setting device was experimentally manufactured. Also, to avoid sea turtle by-catch, a new method in which all the branch lines are set at almost the same depth with instaling the midwater lifting-up floats to the main line was invented. The results are shown as follows.(1)In the first year, the branch lines used by Japanese tuna longline vessels was investigated, and the composition and the feature of branch lines were clarified. The hook sinking speed in ten types of branch lines was examined. In addition, to improve sinking speed of the hook, two new techniques were tested : material of 10m line close to the hook was altered from nylon monofilament to fluorocarbon ; and weight of 10-60gw was added to the hook. The average sinking speed of the hooks from 0 to 1 … More 0 m in depth varied from 0.161 to 0.228 m/s in the ten types of branch lines. However, no hook in the ten types was not able to sink in depth of over 10m before the fishing vessel at vessel speed of 10 knots for casting was 150 m away from the point of casting line, that is, effective area of bird scaring streamer (Tori-pole). The sinking speed of the hook with fluorocarbon line was 1.6 times larger than that with nylon monofilament, and the hook with additional weight of 45gw sank almost two times faster than conventional one. (2)In this fiscal year, First of all an underwater setting device was manufactured for preventing incidental catch of seabirds. By the sea trial, it was confirmed that the fishhooks were always released into the water depth of 1.3 m. On the other hand, the setting shape of the tuna longline in the sea with flow was clarified through the sea trial and theoretical analysis. (3)To avoid sea turtle by-catch, a new method using the midwater lifting-up floats for tuna longline was invented. From the experimental results, it was possible to set all the hooks at almost the same depth by giving adequate buoyancy to some points in the main line.As mentioned above, in this research, the purpose was achieved and the reduction in incidental catch of seabirds can be expected by using the improved branch line and by using the developed underwater setting device. Moreover, by introducing a new method using the midwater lifting-up floats in operation, it is also possible to avoid sea turtle by-catch. Less

为了制定减少金枪鱼延绳钓渔业中意外捕获海鸟的缓解措施，对日本金枪鱼延绳钓渔船使用的支绳的钩沉速度进行了调查，并实验性地制造了一种水下设置装置。此外，为了避免误捕海龟，还发明了一种新方法，即将所有分支线设置在几乎相同的深度，并在主线上安装中水提升浮子。结果如下所示。(1)第一年对日本金枪鱼延绳钓渔船使用的支线进行了调查，明确了支线的组成和特点。对10种支线的沉钩速度进行了测试。此外，为了提高吊钩的下沉速度，试验了两种新工艺：将靠近吊钩的10m线材料由尼龙单丝改为氟碳；并将10-60gw的重量添加到挂钩上。10种支路的平均下沉速度在0 ~ 1 m之间，下沉深度在0.161 ~ 0.228 m/s之间。然而，在渔船以10节航速进行抛钓时，在距抛钓线点150m处，即吓鸟拖缆（托里杆）有效区域内，10种型号中没有一种鱼钩下沉深度不超过10m的。使用氟碳线的鱼钩下沉速度比使用尼龙单丝的鱼钩快1.6倍，附加重量为45gw的鱼钩下沉速度比普通鱼钩快近2倍。(2)本财政年度，首先制造了一种水下设置装置，以防止意外捕获海鸟。经海试，证实鱼钩始终放至水深1.3 m处。另一方面，通过海试和理论分析，明确了金枪鱼延绳钓在流动海域的设置形状。(3)为避免海龟被误捕，发明了金枪鱼延绳钓中水吊浮子的新方法。从实验结果来看，通过给主线上的一些点提供足够的浮力，可以将所有的钩子设置在几乎相同的深度。如上所述，在本研究中，通过使用改进的分支线和开发的水下设置装置，可以达到减少海鸟偶然捕获的目的。此外，通过引入一种新的方法，即使用中水提升浮子，也可以避免海龟被误捕。少