Fish behavior around a trap-net with the leader-net lit by a low-power underwater lamp

摘要

A 55 W underwater discharge lamp was set in front of the leader-net of a trap-net in Hirado Island, Nagasaki. The light was left on for 4 hours during the nighttime. We observed fish schools around the trap-net by using a scanning sonar. Fish schools were frequently observed around the lamp when lit and tended to move to the entrance of the trap-net when the lamp was turned off. We also released tagged jack mackerels before, during and after illumination from three locations in front of the leader-net to assess the effect of illumination on the catch performance of the trap-net. The recapture rate of the jack mackerels during illumination was higher than that during other time periods. Thus, the underwater illumination helps by making fish remain around the trap-net and consequently improving the catch performance of trap-net fishing.