Use shark liver oil to reduce seabird bycatch

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

30%
Certainty

25%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Seabirds may be predated by large fish such as sharks and so may show avoid the smell of them. Dripping shark liver oil whilst setting lines may, therefore, reduce bycatch.

Study locations

Key messages

Two replicated and controlled trials found reductions in the number of seabirds following boats, or diving for baits, when shark liver oil was dripped behind the boats. Other oils had no effect.
A third replicated and controlled trial in found no differences in the number of seabirds following a bait-laying boat with shark liver oil.

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 replicated, controlled experiment off the coast off north-east New Zealand (Pierre & Norden 2005) found that the number of dives made by seabirds in pursuit of pilchard baits behind a longline fishing vessel was dramatically lower (< 5 birds/min) when small quantities of shark liver oil were dripped onto the water behind the vessel than during control trials using vegetable oil (always > 30 birds/min) or sea water (20-40 birds/min). Diving birds were mainly flesh-footed shearwaters Puffinus carneipes, but also Buller\'s shearwaters Puffinus bulleri and white-faced storm petrels Pelagodroma marina.
Study and other actions tested
Referenced paper
Pierre J. & Norden W. (2005) Trials using shark liver oil to deter seabirds from eating bait during long-line fishing, Leigh, New Zealand. Conservation Evidence, 2, 99-100.
One replicated, controlled experiment off Kaikoura, South Island, New Zealand, in 2005 (Norden & Pierre 2007) found no significant differences in the number of seabirds following a bait-laying boat when it was dripping shark liver oil (both commercially available and made by fishermen) behind the boat, compared to control conditions. However, a second trial in April 2006 off Hauraki Gulf, North Island, New Zealand found the number of seabirds following a bait-laying boat decreased significantly faster if fisherman-produced shark liver oil was dripped behind the boat, compared to controls dripping seawater. Other fish oils (anchovy, pollock and commercially available shark liver oil) did not have a significant impact on the number of following birds. However, all oils except for anchovy did significantly reduce the number of dives made by seabirds.
Study and other actions tested
Referenced paper
Norden W.S. & Pierre J.P. (2007) Exploiting sensory ecology to reduce seabird by-catch. Emu, 107, 38-43.

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

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Actions	Effectiveness	Studies	Category
Thaw bait before setting lines to reduce seabird bycatch Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Reduce ‘ghost fishing’ by lost/discarded gear Action Link	No evidence found (no assessment)	0	Synopsis Link
Turn deck lights off during night-time setting of longlines to reduce bycatch Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link