単位努力当り漁獲量から生残率を計算する方法についての若干の検討〔英文〕

概要

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1) Three aproximate methods for calculating the survival rate or the total mortality coefficient from the data of catch per unit effort were examined critically to compare the accuracy. They are method of mean effort, method of arithmetic mean of catch per unit effort and method of geometric mean of catch per unit effort. In the second and third methods, the total mortality coefficient is correlated with either the fishing effort of the period or the weighted mean effort of three periods, including the periods before and after. 2) If natural mortality and fishing mortality are distributed evenly within the period, the method of mean effort is expected to provide the estimates with least bias and is recommendable for the estimation of natural mortality coefficient and catchability coefficient through regression analysis of the total mortality coefficient on the fishing effort. Bias of the method of arithmetic mean of catch per unit effort is generally large and this method is not preferable. 3) When natural mortality and fishing mortality vary within a period, degree of approximation of the method of mean effort is not generally good. The larger is the natural mortality and the more skew is the distribution of effort the larger would be the bias. A skew distribution of effort would have little effect if the same pattern of the distribution is repreated every period but otherwise the effect would not be negligible.
日本水産學會の論文