PELAGIC LONGLINE BYCATCH MITIGATION. Review of current mitigation for pelagic longline gear A major product of previous SBWG meetings has been a review of information on current mitigation research for pelagic long-line fisheries and the identification of knowledge gaps (AC3 Doc 14 Rev 4, Appendix 4, Table 2; AC4 Doc 14 Rev 4, Annex 5). The advice embodied in the table has been distributed to some of the tuna RFMOs, where it has been well received. At this year‘s meeting the Working Group reviewed and updated the information in this table, following presentation of a number of papers which dealt comprehensively with design of Bird Scaring Lines, and the impact on line sink rates of line shooters, bait life-status, placement and amount of weight in relation to the hook, and bait thaw status (SBWG-3 Doc 5, 7, 8, 11, 12, 13 Rev1 and 31). The results of this review are attached as Annex 3. As before, it is recommended that the Advisory Committee endorse this advice and encourage Parties to use this information to guide the development of policy and practice within the fisheries under their jurisdiction. These papers highlighted a number of issues relevant to mitigation of seabird bycatch in pelagic longline fisheries and provided, for the first time, information on the effectiveness of mitigation measures that have been advocated for many years, without appropriate empirical evidence. This information is summarised below: — Bird Scaring Lines, of either conventional or ‗light‘ design, and used in either single or double configuration, are inadequate for reducing seabird bycatch when used without other mitigation measures. To be effective they must be used with branchline weighting and/or night setting. — Weighting regime and sink rates. Adding weight to lines to expedite gear sink rates is the most effective method of reducing seabird mortality in longline fisheries. The influence of line weighting on seabird mortality is only partially understood. Research on line weighting is still in progress and head-to-head comparisons of the effectiveness of line weighting regimes (and associated sink rates) as seabird deterrent are encouraged, together with further studies on the economics of fishing under prescribed weighting regimes. When considering sink rates to target depths it is necessary to recognise the importance of the ―initial‖ (e.g., 0-2 m) and ―final‖ (e.g., 4-6 m, or thereabouts) sink rates. A fast initial sink rate reduces visual cues in the critical shallow depths and a fast final rate max...
PELAGIC LONGLINE BYCATCH MITIGATION. 15.2.1 The SBWG reviewed recent developments in seabird bycatch mitigation technologies by its members and others. These developments included updates on line weighting trials, an underwater bait setter, hook pods, bird scaring lines and the performance of weighted versus unweighted branchlines deployed in combination with paired bird scaring lines during day and night.
PELAGIC LONGLINE BYCATCH MITIGATION
