落網の網型模型に対する魚群行動の水そう実験

Abstract

In order to compare the performance of trap nets, water tank experiments of fish behavior to the model nets constructed by PVC plate were conducted, using bitterling Rhodeus ocellatus ocellatus as an experimental fish and a video behavior analyzer system for observing and analysing the fish behavior. Six different types of trap nets as the model net were examined; two mouth trap net with two bags, two mouth trap net with a left bag, two mouth trap net with a right bag, single mouth trap net with two bags, single mouth trap net with a left bag and single mouth trap net with a right bag. For the fish school comming from the left hand side of the leader net, the rate of right turn behavior just after entering the net was extremely high; 89% for the two mouth trap nets and 76% for the single mouth trap nets. The rate of remaining, which was employed as an index of the catching performance, showed the maximum in the right bag net and the minimum in the left bag net for both the two mouth trap nets and the single mouth trap net. The results seem to support an empirical rule that the bag net should be set to the same side as the leader net in the single mouth trap net.