Use natural control agents: cleaner wrasse

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Two studies in Ireland found mixed effects of cleaner wrasse on sea lice numbers infesting salmon. One controlled study found corkwing and goldskinny cleaner wrasse were as effective at controlling lice infestation as chemical treatments. One replicated, controlled study found rockcook cleaner wrasse were ineffective at preventing lice outbreaks.

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. Between 1991 and 1992, a controlled study (Deady et al., 1995) at two salmon farms off the west Irish coast found the numbers of lice, Caligus elongates, infesting salmon, Salmo salar, were low in cages containing corkwing and goldsinny cleaner wrasse. Similar levels of lice were found in wrasse stocked cages and those chemically treated with a pesticide. Infestation levels were on average five lice per fish. Cleaner wrasse were as effective as chemical treatment at wrasse: salmon ratios as low as 1:250. The first farm used eleven ‘Polar Circle’ cages (12m depth, 20m diameter). One cage was stocked with 188 cleaner wrasse and 47,000 salmon smolts. All other cages were given chemical treatment for the duration of the study. At the second farm, two groups of eight square ‘Turmec’ cages (10m depth, 10m width) were stocked with 5,000- 8,000 salmon smolts each. Eight cages were stocked with 500-800 cleaner wrasse. The remaining cages were chemically treated for sea lice. On both farms, random samples of 15 salmon were removed from each cage every 1-2 weeks to monitor lice infestation levels.

    Study and other actions tested
  2. In 1992, a replicated, controlled study in Ireland (Tully et al., 1996) found rockcook cleaner wrasse failed to consistently reduce numbers of lice, Caligus elongates, in sea-caged salmon, Salmo salar. When compared to control cages, the wrasse controlled infestation levels, preventing an outbreak on only one of the seven sampling periods. Each of five circular salmon cages (50-70m circumference, 10m depth) was stocked with between 13,000 and 24,000 salmon smolts. Wrasse were added to four cages at wrasse: salmon ratios between 1:37 and 1:49. Wrasse were not added to the control cage.

    Study and other actions tested
Please cite as:

Jones, A.C., Mead, A., Austen, M.C.V.  & Kaiser, M.J. (2013) Aquaculture: Evidence for the effects of interventions to enhance the sustainability of aquaculture using Atlantic salmon (Salmo salar) as a case study. Bangor University


Where has this evidence come from?

List of journals searched by synopsis

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Sustainable Aquaculture

This Action forms part of the Action Synopsis:

Sustainable Aquaculture
Sustainable Aquaculture

Sustainable Aquaculture - Published 2013

Atlantic salmon Aquaculture Synopsis

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