Individual study: The use of cleaner- fish to control sea lice on two Irish salmon (Salmo salar) farms with particular reference to wrasse behaviour in salmon cages
Deady S, Varian S.J.A. & Fives J.M. (1995) The use of cleaner- fish to control sea lice on two Irish salmon (Salmo salar) farms with particular reference to wrasse behaviour in salmon cages. Aquaculture, 131, 73-90
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Use natural control agents: cleaner wrasse
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.