Continuous monitoring of catch fluctuation of Japanese common squid Todarodes pacificus using load data of squid jigging machine

In order to study the process from gathering to capture of Japanese common squid Todarodes pacificus under a jigging boat, it is necessary to monitor rapid changes of the catch of the squid during jigging operation. For this purpose, we developed a logging system to record the load of the automatic jigging machine and evaluated the usefulness of load data for estimating the number of squid caught per unit effort (CPUE). Thirty-four jigging operations were conducted by R/V Hakusan-maru (167 gross tons) in the Sea of Japan. The squid were caught by using 14 jigging machines and the load data of each machine were logged every second on a laptop computer. Number of squid caught was counted by hand or video images and CPUE was calculated. Average load during hauling of the jig line was closely correlated with the measured CPUE in consideration of body size, and an equation for estimating CPUE from load data was derived. The estimated CPUE were in good agreement with the measured CPUE over a wide time scale from one stroke of the jig line to the overall operation. These results indicate that the logging system is especially useful for high time-resolution monitoring of the catch.