Integrated weight longlines with paired streamer lines – best management practice for demersal longline fisheries: preliminary results

Minimizing the time gear is available to seabirds by increasing the sink rate of longlines is one method to effectively reduce seabird catch rates. We fished normal unweighted longlines (UW) and integrated weight longlines (IW-50 g/m) with and without paired streamer lines (PS) in seabird mitigation trials targeting Pacific cod in the Bering Sea, Alaska, USA. Our objective was to evaluate IW as a practical seabird mitigation device using multiple criteria: catch rates of seabirds and fish, seabird behaviour, sink rate of the gear and breaking strength.
All mitigation technologies dramatically decreased seabird bycatch rates while having little to no effect on fish catch rates. Sink rate measurements demonstrated that IW longlines reduce risk to seabirds by minimizing the distance astern that birds have access to sinking baits (~50% reduction). This study and our data from 2000 and 2002, also clearly show that the sink rate varies dramatically by vessel.
Through independent tests, we determined that IW breaking strength is 5% less than UW for new gear and 13% less for gear fished for five months; however, this difference did not manifest itself in the context of commercial fishing as increased line separations.
We conclude that IW longlines deployed with paired streamer lines is the best mitigation practice available for autoline longline systems and make recommendations for modifications to CM 24-02 and CM 25-02.