Journal Article

Open-ocean infestation by salmon lice (<i>Lepeophtheirus salmonis</i>): comparison of wild and escaped farmed Atlantic salmon (<i>Salmo salar</i> L.)

J. A. Jacobsen and E. Gaard

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 54, issue 6, pages 1113-1119
Published in print December 1997 | ISSN: 1054-3139
Published online December 1997 | e-ISSN: 1095-9289 | DOI:
Open-ocean infestation by salmon lice (Lepeophtheirus salmonis): comparison of wild and escaped farmed Atlantic salmon (Salmo salar L.)

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Salmon lice (Lepeophtheirus salmonis) infestation was investigated in 128 salmon (Salmo salar L.) caught on floating long-lines in the Norwegian Sea during November–March 1993–1995. Overall prevalence was 99.2% and abundance 29.5 lice per salmon. Most lice were adults (90%), and 72% of these were ovigerous females. These adult lice were estimated to be at least 3 months old based on prevailing sea-surface temperatures at the sampling site: 7°C in November and 3°C in March. The prevalence and abundance of lice on one sea winter (1 SW) salmon were significantly higher on escaped farmed fish than on wild salmon. However, no difference in abundance was observed between 2SW farmed and wild salmon. The average number of lice per surface area of fish (density) was significantly higher in 2SW wild salmon than in 1SW wild salmon, indicating an accumulation of lice on the salmon in the oceanic phase. No differences in density were observed between 1SW and 2SW farmed salmon. The prevalence of Caligus elongatus was low (5.5%), with an abundance of 0.9 lice per salmon.

Keywords: Atlantic salmon; Caligus elongatus; escaped farmed salmon; Lepeophtheirus salmonis; open-ocean infestation; Salmo salar; sea age; sea lice; wild salmon

Journal Article.  0 words. 

Subjects: Environmental Science ; Marine and Estuarine Biology

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