移動網地に對するウグイの行動

REACTION OF UGUI, TRIBOLODON HAKONENSIS, TOWARD THE MOVING NET

The optomotor reaction of fish related to fishing method was studied, aiming the analysis on the fish behavior toward a mobile fishing gear, such as a trawling net in operation. Recently, some attempts also have been made to determine its possible application for fishing purpose. In the present paper, the main point of observation was the reaction of Ugui Tribolodon hakonensis in the presence at a rotating visual screen, which was employed as the visual stimuli to release the chasing behavior due to the optomotor reaction of fish. Four kinds of visual patterns are compared in order to determine the intensity of each visual stimulus. A visual screen made of black tape stripes arranged at a interval of 12.5cm, can release the typical optomotor reaction. Its intensity as a visual stimulus is higher than when the black tape screen is arranged at a interval of 25cm. When expored to the transparent vinyle tape screen, fish school does not show any chasing reaction at all. In the case of the net screen, chasing behaviour of fish school is nearly equal to the black tape screen of 12.5cm interval. While, under the condition of current influence, reaction of fish is rather higher than the black tape screen of 12.5cm interval. In conclusion, fishing net is considered to have enough intensity as visual stimuli capable of triggering the chasing behaviour of fish.