Acoustic estimation of effective gathering range of shipboard fishing light for squid jigging

The effective range of fishing light for the Japanese common squid jigging was investigated using acoustic methods in the Japan Sea on August 21- 24, 2011. The research vessel collected acoustic signals of a sonar and a quantitative echosounder from squid around the jigging boat equipped with metal halide lamps. Digital images of sonar echogram were composed to make maps which can be used to measure locations, sizes, and relative echo intensity of squid school. Behavior of individual squid was observed by an acoustic tag. The receiver was prepared on each vessel. The tag was attached on a fin of squid onboard the research vessel. Total 22 tagged squids were released from the research vessel in three nights and the distance between the vessels at release time ranged from 0.25 to 1.1 nmi. Total 7 squids were received at the jigging boat after 1 - 3 hours from their release. The distance between vessels at release time ranged 0.25 to 0.7 nmi. The squids which were released within 0.5 or 0.6 nmi were received at the jigging boat in every night. From these results, the effective gathering range of the fishing light was estimated to be at least 0.5 nmi.