Body Length Composition and Recruitment Time of Hime Salmon Oncorhynchus nerka in Lake Chuzenji Judged by Experimental Fishing

Abstract

Seasonal changes in the body length composition of hime salmon and its recruitment time as fishing resources in Lake Chuzenji were examined on the basis of results of experimental fishing performed 13 times every odd month from March in 1985 to March in 1987. Throughout the whole examination periods, from January to May, a mode of body length was recognized in 25cm to 26cm mainly, although small number of smaller or larger fishes were caught up. However, the frequency of the appearance of small fishes started to increase in July and the mode was shifted to 18 to 19cm. In November, large-sized fishes with the body length of 28cm or more ascended a stream for spawning and disappeared from the lake or were remained in a small number. It can be assumed that the recruitment into the fishing ground as fishing resources starts mostly in May when fishes grow into certain size with the main group having 18 to 19cm of body length, thus filling the space left after the ascending.