Action Synopsis: Bird Conservation About Actions

Reduce seabird bycatch by releasing offal overboard when setting longlines

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

Two replicated and controlled studies in the South Atlantic and sub-Antarctic Indian Ocean found significant reductions in the number of albatross and petrels attacking baits and being caught when offal was released overboard during line setting.


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

  1. A replicated and controlled study in the South Atlantic in February 1994 (Cherel et al. 1996) found that piping offal overboard whilst setting longlines greatly reduced the number of birds caught on 69 line sets, from 33 birds to three, equivalent to a decrease from 0.49 to 0.01 birds/1000 hooks. Caught birds were white-chinned petrels Procellaria aequinoctialis, and two grey-headed albatross Thalassarche chrysostoma (formerly Diomedea chrysostoma). There was a corresponding significant decrease in the rate of bird attacks on the bait for all species except wandering albatross D. exulans (92% decrease for black-browed albatross T. melanophris (formerly D. melanophris), 96% for grey-headed albatross and 96% for white-chinned petrel). Vessels were fishing for Patagonian toothfish Dissostichus eleginoides around South Georgia and Kerguelen Islands.

    Study and other actions tested
  2. A replicated, controlled study in the sub-Antarctic Indian Ocean in 1994-7 (Weimerskirch et al. 2000) found that significantly fewer white-chinned petrels Procellaria aequinoctialis were caught on longlines when offal was released over the side of the boat as lines were being set (0.46 birds/1,000 hooks caught when offal was released vs. 1.00 birds/1,000 hooks with no release, total of 524 lines studied). There were no significant changes in other species caught, possibly due to smaller sample sizes. The authors caution that significantly more birds followed fishing boats when they released offal (significant increases for six of ten species) and the practice may therefore enforce long-term associations between fishing boats and food. This study is also discussed in ‘Set longlines at night to reduce seabird bycatch’ and ‘Use streamer lines to reduce seabird bycatch on longlines’.

    Study and other actions tested
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

Bird Conservation

This Action forms part of the Action Synopsis:

Bird Conservation
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust