Collaboration with commercial longliners in the Japanese coast for exploring effective design of tori-pole between 2009 and 2016
The document summarized the effort of developing an effective design of tori-line suitable for commercial longline operations along the Japanese coast during 2009 to2016. The longline fishers based in Kesen’numa operating in the North Pacificparticipated with this experiment. Every year, two types of tori-lines were distributed to he commercial fishers for a comparison of certain aspects of tori-line design, including difference in total length of main line, color and types of attachments, overall weight, general structure, and so on. Fishers were requested to record number of seabirds observed during a setting, total number of hooks deployed, and number of seabirds caught by species, for each operation, in addition to whether or not used the tori-line distributed. The experiment indicated the preference of tori-line with less weight for a convenience of operations and no distinct difference in mitigation impacts according to the color of attachments. Although two lines resulted in lower seabird bycatch, they also caused some inconvenience in operation, including increased time of deployment and retrieval, and restriction in operation flexibility such as need to maintain a course ofsetting. The exercise was more for promoting an acceptance and utilization of tori-pole than for purely scientific survey for identifying critical factors influencing the mitigation effectiveness of tori-line. In fact, many of fishers utilize the distributed tori-line throughout the year, even after the experimental period. It is planned to continue this exercise for exploring the most suitable tori-line to the local situation.