Summary of utilization of mitigation techniques to reduce seabird bycatch in Japanese small-sized longline vessels

To discuss effective and suitable seabird bycatch mitigation measures for small sized longline vessels (< 20 tonnage), information of utilization of seabird mitigation techniques voluntarily used in seventeen vessels were collected from a hearing survey. In all vessels fishermen used tori-line (bird-scaring line) and they deployed three types of tori-lines (with streamers, without streamers and direct connection of long streamers on poles). Many fishermen concerned entanglement tori-line materials with main line of longline in the rough sea hence attachment of streamers on tori-lines for small vessels should be carefully considered. In order to attain effective sink rate for branch line, seven vessels (41%) used weighed branch line and five vessels (29%) used fluorocarbon for branch line. In addition, this some vessels tried strategic offal discharge to put seabird assemblage away from line setting area. These information are useful to develop suitable mitigation techniques in small sized longline vessels. Some of measures introduced in that fishery are worth to examine for effectiveness.