水槽実験におけるニジマス日周活動と照度の刺網漁獲に及ぼす影響

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This paper describes the modeling of a fish-capturing process on a gillnet by evaluating the diurnal activity of fish and behavior to the net. Diurnal activity was investigated in an outdoor experiment, and fish behavior to the net was studied at different light intensities in an indoor experiment with rainbow trout Oncorhyncus mykiss. The activity of rainbow trout is diurnally periodic, increasing rapidly before sunrise at dawn, and decreasing gradually after sunset at dusk in the outdoor experiment. The activity of rainbow trout is thought to depend not only on lignt intensity but also on the endogenous rhythm of the fish. The activity increased over 101 lx light intensity in the day-time indoor experiment. Fish seldom encounter the net under 102 lx, and the frequency of encounter to the net began to increase at 101 lx and saturated at 10-2 lx. The net encounter rate was thus estimated as a function of time. The encounter rate showed two remarkable peaks at dawn and dusk, which account for the mazume phenomenon of an increase in the catch of gillnets in the twilight.
公益社団法人日本水産学会の論文