Use a line shooter to reduce seabird bycatch

Overall effectiveness category Likely to be ineffective or harmful
Number of studies: 2
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How is the evidence assessed?

Effectiveness

0%
Certainty

50%
Harms

40%

Calculating overall effectiveness category

Background information and definitions

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.

Study locations

Key messages

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.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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’.
Study and other actions tested
Referenced paper
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.
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’.
Study and other actions tested
Referenced paper
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.

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bird Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Thaw bait before setting lines to reduce seabird bycatch Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Use larger hooks to reduce seabird bycatch Action Link	No evidence found (no assessment)	0	Synopsis Link
Use a sonic scarer when setting longlines to reduce seabird bycatch Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link