Mitigation of seabird mortality on factory trawlers: trials of three devices to reduce warp cable strikes

Experimental trials were conducted onboard a stern trawler to identify the relative efficacy of three emerging mitigation measures (tori lines, warp scarer and Brady baffler) designed to reduce seabird mortality caused by warp cable strikes. The use of mitigation measures was clearly shown to substantially reduce seabird mortalities from collisions between seabirds and warp cables. Based on an established significant relationship between contact rate and seabird mortality, when using contact rate as an index of mortality there was a clear performance hierarchy of the three measures. Tori lines and the warp scarer were significantly more effective at reducing contacts than the Brady Baffler, whilst tori lines represent a smaller, but still significant, improvement on the warp scarer. While further testing would be required under local environmental and operational conditions, our findings are likely to have application for many trawl fisheries around the world.