日本海西南海域およびその周辺海域における近年のムシガレイの漁獲と資源の動向

概要

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During the period of 1969 to 1985, annual catch of roundnose flounder increased gradually with some fluctuations till 1978 and then began to decrease in a medium pair trawl fishery of the south-western Japan Sea and its adjacent wasers. This paper examined a recent trend of this stock, using lenght compositions and catch by market size categories in the fishery from 1980 to 1985. The estimated age compositions gave 1.2-1.3 year-1 as estimates of total mortality coefficient in the period of 1980 to 1985. The age compositions also revealed that a recruitment index exponentially decreased at an annual rate of 18% with year at least in the period of 1979 to 1984. Moreover, the exploitation rate for the 1-year-old flounder of 1982 and 1983 year classes decreased to be about one-half of that of 1978-1981 year classes, which were relatively large. Consequently, a decrease of the stock is considered to be caused mainly by a high fishing pressure exerted on the stock, especially on young age classes, in the late 1970's when other important target species continued to decline.
日本水産學會の論文