単位漁獲努力当り漁獲量の分布型が指数型分布に近似する漁業種類の漁獲機構について
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概要
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The type of distribution curve of catch per unit effort of the fishing in which gear is not moved by operation is very like exponential distribution. For this reason the author assumed the mechanism of such fishing as follows: (1) A fish forms schools in the water and the distribution of the amount of fish constituting unit school is exponential distribution, which is represented by the formula (1), (2) The number of schools to be caught by unit effort conforms to Poissons distribution, and it is represented by the formula (2), (3) When n schools are taken at random from φ(x) as defined in (1), the distribution of amount of fish constituting n schools is given by the formula (3). Under these assumptions, the theoretical distribution of catch per unit effort is determined by the formula (4), and its mean and variance are given by the formulae (5) and (6) respectively. Parameters obtained under these assumption are shown in Tables 1, 2 and 3, and theoretical distribution curves with these parameters are compared with the actual distributions in Figs. 1-5. In this comparison, the theoretical distributions are well fit for actual one sexcept the case where the actual distribution is like logarithmic normal or heavy exponential one. Providing that the assumptions mentioned above is reasonable, it can be estimated that in case of Sardine gill net the averages of amount of fish constituting unit school range from 120 “kan” (450kg) to 170 “kan” (670kg) and the number of schools taken by unit effort is 0.6 to 1.6.
- 公益社団法人 日本水産学会の論文