1National Research Institute of Fisheries Engineering, Hasaki, Ibaraki 314-0421, 2Department of Marine Science and Technology, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan
The spatial distribution of squid jigging boats and the shortest distance between boats were observed by a radar, at major fishing grounds of the Japan Sea in the summer season in order to investigate the actual condition of fishing boat group operation. The Area occupied by squid jigging boats and shortest distance between boats showed the minimum value in the Tsugaru Channel sea area and the maximum value in the Northern Sado offshorearea. Optimum distance and light source output for jigging operation were then estimated for each fishing ground. Furthermore, the proportion of fishing light interference was obtained by cumulative frequency distribution of the shortest distance between boats and calculation of fishing lamp luminous range. As a result, the Tsugaru channel sea area, Yamatotai, Kanazawa offshore, Okushiri channel sea area and Northern Sado offshore areas showed 100% and 99%, 62%, 40% and 34% of the probabilities of light interference by other boats in group operation respectively, when 180kW, the upper limit of light source output for small squid jigging boats, was employed.