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Diseases of Aquatic Organisms

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DAO 113:187-194 (2015)  -  DOI:

Evaluation of emamectin benzoate and substance EX against salmon lice in sea-ranched Atlantic salmon smolts

Ove Tommy Skilbrei1,*, Per Gunnar Espedal2, Frank Nilsen2, Enrique Perez Garcia1, Kevin A. Glover1,2

1Institute of Marine Research, PO Box 1870 Nordnes, Bergen 5817, Norway
2Department of Biology, Sea Lice Research Centre, University of Bergen, PO Box 7803, Bergen 5020, Norway
*Corresponding author:

ABSTRACT: Experimental releases of Atlantic salmon smolts treated with emamectin benzoate (EB) against salmon lice have previously been used to estimate the significance of salmon lice on the survival of migrating smolts. In recent years, the salmon louse has developed reduced sensitivity to EB, which may influence the results of such release experiments. We therefore tested the use of 2 anti-lice drugs: EB was administered to salmon smolts in high doses by intra-peritoneal injection and the prophylactic substance EX (SubEX) was administered by bathing. A third, untreated control group was also established. Salmon were challenged with copepodids of 2 strains of salmon lice (1 EB-sensitive strain and 1 with reduced EB-sensitivity) in mixed-group experimental tanks. At 31 d post-challenge, the numbers of pre-adult lice on treated fish were around 20% compared with the control fish, with minor or no differences between the 2 treatments and lice strains. Both treatments therefore appeared to give the smolts a high degree of protection against infestation of copepodids of salmon lice. However, significantly lower growth of the EB-treatment group indicates that bathing the fish in SubEX is less stressful for smolts than intra-peritoneal injection of EB.

KEY WORDS: Aquaculture · Atlantic salmon · Salmo salar · Sea lice · Lepeophtheirus salmonis · Emamectin benzoate · Substance EX

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Cite this article as: Skilbrei OT, Espedal PG, Nilsen F, Garcia EP, Glover KA (2015) Evaluation of emamectin benzoate and substance EX against salmon lice in sea-ranched Atlantic salmon smolts. Dis Aquat Org 113:187-194.

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