若狭湾沖合におけるズワイガニ漁獲物の脱皮齢組成

Abstract

In spite of the shortening of the fishing season and restrictions on the use of fishing grounds, the resources of snow crabs Chionoecetes opilio have been declining in the western region of the Sea of Japan. If such a low level of crab stock persists, more effective improvements will be needed in the snow crab fishery. The present paper deals with analyses of catch data of the crabs by Danish seines, and gives some suggestions for the improvement of the crab fishery. The results obtained are as follows: male crabs can be caught as fishing targets from the 12th molting stage (93.4mm in carapace width; legal size is 90mm or larger) in the crab fisheries resources off Wakasa Bay. On the other hand, female crabs embracing fertilized eggs can be caught as fishing targets from the adult stage, a year and a half after the 11th molting stage. Therefore, both male and female crabs are caught at the same age. More than half of the male crabs caught are those in the 12th molting stage and soft crabs. Similarly, on the basis of identical patterns found in the fluctuation in annual catches of male and female crabs, more than half of these newly adult female crabs are assumed to be fished.Judging from an analysis of the catch data and biological information, it is necessary to use soft crabs effectively and to conserve the adult female crabs newly caught as fishing targets by the Danish seine fishery.