競争関係にある2種資源の最も速やかな回復方策

抄録

The stocks of economically valuable fish species are easily depleted, because they are selectively harvested. Although the importance of their recovery is obvious from both conservational and economical viewpoints, it is usually difficult because their intrinsic growth rates are low. Com-petition with species with a larger intrinsic growth rate may further increase the difficulty. In this paper, the fastest way to attain a predetermined target stock level by controlling the harvest is obtained for a two-species competition system. The result indicates that, in order to attain the target rapidly, the stock with the larger intrinsic growth rate should first be harvested intensively and the relative abundance of it should be reduced below that at the target. A suboptimal but practical procedure, which is more acceptable than the optimal one when considering the conserva-tional point of view, is also proposed, and its performance is compared with that of a more con-servational procedure.