抄録
The Japanese mantis shrimp, Oratosquilla oratoria (De Haan), is one of the main target species for small-scale trawlers in Tokyo Bay. In order to take appropriate fisheries management measures, it is required to evaluate precisely the present condition of 0. oratoria stock. In this study, we examined the change in composition of the market size categories of this species using monthly landing data from 1977 to 1989 and evaluated the present fishing intensity to the stock based on the fisheries and biological parameters determined by the authors previously.
Analyses showed that the percentage of large market size categories especially in summer to total landings has declined, but this is due to the increase of total landings containing small individuals because of the increased upper limit of landings by one fishing vessel per day. A decrease of absolute landings of large market size categories was not confirmed. Judging from the stock assessment using both the yield isopleth diagram and results of biological analysis (calculation of the rate of decrease of spawning adults), the present fishing intensity for O. oratoria stock in Tokyo Bay was at around the optimum level.
