Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

By E. Thorstad, C. Todd, I. Uglem, P. Bjørn, P. Gargan, K. Vollset, E. Halttunen, S. Kålås, M. Berg, B. Finstad. 2015

160 citations recorded by the source corpus.

Salmon farming increases the abundance of salmon lice, which are ectoparasites of salmonids in the sea. Here we review the current knowledge on the effects of salmon lice on wild sea trout. Salmon lice feed on host mucus, skin and muscle, and infestation may induce osmoreg- ulatory dysfunction, physiological stress, anaemia, reduced feeding and growth, increased sus- ceptibility to secondary infections, reduced disease resistance and ultimately mortality of individ- ual sea trout. Wild sea trout in farm-free areas generally show low lice levels. In farm-intensive areas, lice levels on wild sea trout are typically higher, and more variable than in farm-free areas. Lice on wild sea trout are found at elevated levels particularly within 30 km of the nearest farms but can also extend to further ranges. Salmon lice in intensively farmed areas have negatively impacted wild sea trout populations by reducing growth and increasing marine mortality. Quan- tification of these impacts remains a challenge, although population-level effects have been quan- tified in Atlantic salmon by comparing the survival of chemically protected fish with control groups, which are relevant also for sea trout. Mortality attributable to salmon lice can lead to an average of 12�29% fewer salmon spawners. Reduced growth and increased mortality will reduce the benefits of marine migration for sea trout, and may also result in selection against anadromy in areas with high lice levels. Salmon lice-induced effects on sea trout populations may also extend to altered genetic composition and reduced diversity, and possibly to the local loss of sea trout, and establishment of exclusively freshwater resident populations.

Subfields: Ecology, Nature and Landscape Conservation, Parasitology

View Paper: https://www.semanticscholar.org/paper/aed801d087192d8f5f5a5dc581ebf8997c4d71e9

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In Ecology

1. P. Bjørn
2. B. Finstad
3. M. Berg
4. E. Thorstad
5. M. Krkošek
6. I. Uglem
7. C. Todd
8. O. Diserud

In Nature and Landscape Conservation

1. B. Finstad
2. M. Krkošek
3. C. Todd
4. Kevin D. Friedland
5. E. Thorstad
6. O. Diserud
7. C. Jørgensen

In Parasitology

1. P. Bjørn
2. B. Finstad
3. M. Berg
4. M. Krkošek
5. K. Boxaspen

Citations in the corpus

• The major threats to Atlantic salmon in Norway (2017, unknown): “Since the late 1980s, salmon lice epizootics have been reported in wild salmonids in Norway, Scotland, Ireland, and Canada (Heuch et al., 2003, 2005; Revie et al., 2009; Finstad et al., 2011; Thorstad et al., 2015).”
• Disentangling the role of sea lice on the marine survival of Atlantic salmon (2018, background): “Sea lice-induced fish mortality tends to occur within 10–20 days of exposure to copepodids in the laboratory, by which time the sea lice have developed to the preadult and adult mobile stages (Finstad et al., 2011a,b; Thorstad et al., 2015).”
• Marine life of the sea trout (2016, background): “farming, with resultant salmon lice Lepeophtheirus salmonis Krøyer infestation on local wild sea trout stocks (Tully and Whelan 1993; Gargan et al. 2003; 2006a, b; Butler and Walker 2006; Skaala et al. 2014b; Thorstad et al. 2015).”