Development of the Size Selectivity Theory of Angling Gear

研究了鱼身尺寸对鱼身尺寸的影响以及鱼具主要部件特性对鱼身尺寸的影响。发现了这些因素与齿轮尺寸选择性之间的关系，从而建立了齿轮尺寸选择性理论。1)鱼钩在流体阻力作用下进入口腔模型的过程。模型中大鱼钩或大鱼饵的最大入鱼距离大于小鱼饵的最大入鱼距离。但大钩的入口比小钩低。考虑进入比，大钩的最大进入距离总平均值小于小钩。2)对于长型挂钩，当杆触及模型入口上部时，最大进入距离发生变化。对于圆型钩，当柄接触到入口时，最大进入距离没有变化。这个钩钩有一个优点，因为钩点很容易接触到模型的内侧上部。3)根据垂钓实验估算的鱼饵难入系数，表明在给定鱼体大小的条件下，存在一个合适的饵料尺寸。饵料大小与硬入系数有关。因为没有一个简单的关系，比如线性关系，所以很难建立一个数学模型。4)由于在勾起机构的随机模型中引入了进入距离的限制，该模型可以拟合更多的勾起现象。进入距离的限制与口腔、钩和饵的大小或形状之间的关系将在未来进行研究。

In this study, the influence of fish size and the influence of the characteristics of the main components of angling gear were investigated. A relation between those factors and size selectivity was found, so the size selectivity theory of angling gear was developed.1) The entering process of a hook into the model of a mouth cavity occurred by fluid resistance. The maximum entering distance of a big hook or a big bait in the model was longer than a small one. But the ratio of entrance of a big hook was lower than for a small one. Considering the ratio of entrance, the total average of the maximum entering distance of the big hook was shorter than for the small one.2) For the long type hook, the maximum entering distance changed when the shank touched the upper part of the entrance of the model. For the round type hook, it did not appear that the maximum entering distance changed when the shank touched the entrance. And this hook had an advantage for hooking because the hook point easily touched the upper inside of the model.3) It was shown that a suitable bait size existed for a given fish size, according to the hard entering coefficient estimated by angling experiments. Bait size was related to the hard entering coefficient. Because there was not a simple relation, such as liner, it was difficoult to construct a mathematical model.4) As the limit of entering distance was introduced in the stochastic model of the hooking mechanism, this model could be fit on many more cases of angling phenomenon. The relation between the limit of the entering distance and size or shape of a mouth cavity, a hook, and a bait will have to be investigated in the future.