A review of the effectiveness of streamer lines as a seabird by-catch mitigation technique in longline fisheries and CCAMLR streamer line requirements

Based to a large degree on the precedent set by CCAMLR in 1991, the streamer line has become the primary, and most commonly prescribed, seabird mitigation device in world longline fisheries. This paper reviews CCAMLR streamer line requirements (Conservation Measure 25-02 (2002), formerly Conservation Measure 29/XIX) in light of a review of existing literature and available data on the effectiveness of single and paired (or multiple) streamer lines.

Research to determine the optimal streamer line design and configuration is lacking and is identified as a high priority. Future streamer line research should compare the attack or dive rate of multiple southern hemisphere seabird species or foraging guilds as a function of distance astern in response to single and multiple streamer lines deployed according to specific performance and material standards. Improvements to streamer line requirements set out in Conservation Measure 25-02 are discussed and proposed relative to recent Alaskan requirements. Proposed changes include: requiring that the streamer line be deployed over the hookline within 100 m of the stern; increasing the height of the streamer line attachment point to the vessel and/or specifying the aerial extent of the streamer line; requiring that individual branched streamers extend to the water in the absence of wind and swell and be attached throughout the aerial extent of a streamer line; including ultraviolet-protected plastic tubing as a permitted streamer material; relaxing the number and placement of swivels in favour of a performance standard; requiring that streamer line attachment points to the vessels and the towed object be deployed windward of the hookline; and recommending that fishers deploy a minimum of two streamer lines on a voluntary basis according to performance and material standards. Based on the recommendations of this review and the discussions of the ad hoc Working Group on Incidental Mortality Arising from Fishing (WG-IMAF), the CCAMLR streamer line requirements were changed by the Commission in 2003.