Action: Use a line shooter to reduce seabird bycatch
- A randomised, replicated and controlled trial from a pelagic fishery in the North Pacific found significantly higher seabird bycatch when a line shooter was used to set longlines.
- A second randomised, replicated and controlled trial (from Norway), found no effect of a line shooter on bycatch rates.
As a longline is deployed it will be put under tension as the movement of the boat stretches the line. This can delay the sinking of the line and baits, increasing the time available for birds to get hooked. A line shooter works by deploying the line faster than the boat is moving, removing tension from it and allowing the line to sink faster.
Supporting evidence from individual studies
A randomised, replicated and controlled study (Melvin et al. 2001) in the North Pacific in August 1999, found that using a line shooter significantly increased the number of birds caught, compared to controls (0.336 birds/1,000 hooks vs. 0.218 birds/1,000 hooks). Treatment had no effect on the number of birds following vessels, or the attack rate on baits. A total of 156 line sets were studied, set for Pacific cod Gadus macrocephalus and walleye pollock Theragra chalcogramma southeast of the Pribilof Islands, USA. This study is also discussed in ‘Weight baits or lines to reduce longline bycatch of seabirds’, ‘Use streamer lines to reduce seabird bycatch on longlines‘, ‘Set longlines at night to reduce seabird bycatch’ and ‘Set lines underwater to reduce seabird bycatch’.
A replicated, randomised and controlled trial on a commercial long-lining vessel off the coast of mid-Norway in August 1999 (Løkkeborg & Robertson 2002), found that by-catch of northern fulmar Fulmarus glacialis was not significantly lower when a line shooter was used during line setting (13 fulmars hooked during 11 sets, 0.22 birds/1,000 hooks), compared with either control sets (32 fulmars in 11 sets, 0.52 birds/1,000 hooks) or with lines set using a streamer line as well (no birds caught on 11 sets with just the streamer line vs. a single bird or 0.02 birds/1,000 hooks on 11 sets with the streamer and shooter). This study is also discussed in ‘Use streamer lines to reduce seabird bycatch on longlines’.
- Melvin E.F., Parrish J.K., Dietrich K.S. & Hamel O.S. (2001) Solutions to seabird bycatch in Alaska's demersal longline fisheries. Washington Sea Grant Program, University of Washington report.
- Løkkeborg S. & Robertson G. (2002) Seabird and longline interactions: effectiveness of a bird-scaring streamer line and line shooter on the incidental capture of northern fulmars Fulmarius glacialis. Biological Conservation, 106, 359-364