豊前海の小型定置網における袋網位置別投棄魚種組成

Abstract

This paper describes the number of fish and crab caught and discarded in individual bag-nets set at different positions in a small set-net. Most of the fish tended to be caught in the bag-nets at one or both ends in four fish species: S. Zunasi, K. punctatus, C. affinis and L. japonicus, whilst the two crabs C. japonica and P. trituberculatus were caught mainly in the bag-nets around the central part of the fence net. The differences between bag-nets in number of each species caught are discussed in terms of gear design and in particular the design of the fence net and the swimming behavior of these spe-cies. The Mesh size of bag-nets in the small set-net fishery in the Buzen Sea is small to catch small-size shrimp. This leads to by-catch of juveniles of the target fish, in particular L. japonicus, one of the most important species. Assuming that small shrimp are likely to be caught in the bag-nets around the central part of the fence net as previously described in some papers, the result of this paper sug-gests the possibility that larger mesh size in both end bag-nets may allow juvenile L. japonicus to escape through the mesh of these bag-nets without reducing the catch of small shrimps.