Impacts of salmon lice emanating from salmon farms on wild Atlantic salmon and sea trout
MetadataVis full innførsel
- NINA Rapport/NINA Report 
Thorstad, E.B. & Finstad, B. 2018. Impacts of salmon lice emanating from salmon farms on wild Atlantic salmon and sea trout. NINA Report 1449: 1-22. Results from scientific studies on the impacts of salmon lice on Atlantic salmon and sea trout are summarized here. Considerable evidence exists that that there is a link between farm-intensive areas and the spread of salmon lice to wild Atlantic salmon and sea trout. Several studies have shown that the effects of salmon lice from fish farms on wild salmon and sea trout populations can be severe; ultimately reducing the number of adult fish due to salmon lice induced mortality, resulting in reduced stocks and reduced opportunities for fisheries. Depending on the population size, elevated salmon lice levels can also result in too few spawners to reach conservation limits. Salmon lice are external parasites on salmon and trout at sea. They feed on fish’s mucus, skin and muscle. Mortality due to salmon lice primarily occurs in young fish after they enter the sea from fresh water (11 mobile lice per fish is lethal level for a 15 g wild salmon), but severely infested sea trout can also die from salmon lice later in life. Mortality occurs because salmon lice can cause severely damaged fins and skin lesions, and thereby physiological stress, problems with salt regulation, increased susceptibility to other infections and reduced disease resistance in individual fish. Salmon lice can also cause reduced swimming performance, feeding and growth and altered behaviour of the fish. Salmon farming increases the spread and abundance of salmon lice in marine habitats, and thereby the risk of infection and mortality among wild salmon and sea trout in areas with fish farms. These facts are both verified by field monitoring of salmon lice on wild fish and by the fact that salmon lice on wild fish in farm-intensive areas have lice with the same resistance to chem-icals as used in farms. Wild fish in farm-free areas generally show low lice levels. In farm-inten-sive areas, lice levels on wild fish are typically higher, but variable. With the expansion of fish farming, marked salmon lice outbreaks on salmonids have been reported from Canada, Ireland, Norway and Scotland. Studies indicate an annual loss of 50 000 adult wild Atlantic salmon to Norwegian rivers because of salmon lice, which corresponds to an overall loss of 10% of the wild salmon because of salmon lice on a national level (i.e., including both farm-free and farm-intensive areas, based on data from the years 2010-2014). Salmon lice from fish farms are identified as one of the two largest threats to wild salmon in Norway. Population-level effects of salmon lice in Ireland and Norway have been quantified in large-scale studies in nature by comparing the survival of individually tagged fish chemically protected against salmon lice with untreated control fish. These studies show that lice-induced mortality in farm-intensive areas can lead to an average of 12-29% fewer adult salmon. To exemplify this loss, a 20% reduction due to salmon lice in a river where 4000 Atlantic salmon spawn each year equals a loss of 800 spawners, which means that 3200 salmon spawners will return to the river in a given year instead of 4000. Mortality of sea trout is likely to be higher than in Atlantic salmon, because unlike the ocean-migrating Atlantic salmon, they usually remain in coastal waters, where fish farms are situated. There are a large number of scientific studies on the impacts of salmon lice on Atlantic salmon and sea trout, ranging from laboratory and field investigations of the effects of salmon lice on individual fish, to analyses of impacts on wild populations. There is year-to-year and local varia-tion in the population effects of salmon lice, and abilities to estimate effects in different areas depend on sufficient resolution of the monitoring of wild fish and salmon lice levels.
UtgiverNorsk institutt for naturforskning (NINA)
Opphavsrett© Norwegian Institute for Nature Research The publication may be freely cited where the source is acknowledged
Viser innførsler beslektet ved tittel, forfatter og emneord.
Utilization of protein, fat and glycogen in cod (Gadus morhua) during starvation ; Broodstock nutrition in cod (Gadus morhua) - effect of dietary fatty acids ; Tissue vitamin B₆ concentrations and aspartate aminotransferase (AspT) activity in atlantic salmon (Salmo salar) fed graded dietary levels of vitamin B₆ ; Effects of dietary iron supplementation on tissue iron concentrations and haematology in atlantic salmon (Salmar salar) ; Health aspects of dietary lipid sources and vitamin E in atlantic salmon (Salmo salar). I. Erythrocyte total lipid fatty acid composition, haematology and humoral immune response ; Health aspects of dietary lipid sources and vitamin E in atlantic salmon (Salmo salar). II. Spleen and erythrocyte phospholipid fatty acid compoisition, nonspecific immunity and disease resistance Hemre, Gro-Ingunn; Karlsen, Ørjan; Lehmann, Gunnar; Holm, Jens Christian; Lie, Øyvind; Mangor-Jensen, Anders; Albrektsen, Sissel; Waagbø, Rune; Sandnes, Kjartan; Bjørnevik, Marit; Maage, Amund; Nilsen, Espen Raa; Jørgensen, Jorun; Engstad, Rolf; Glette, Johan (Fiskeridirektoratets skrifter, Serie ernæring;Vol. 6, No. 1, Working paper, 1993)
Growth and physiological properties in white trunk muscle of two anadromous populations of arctic charr (Salvelinus alpius) ; A note on the molecular distribution of the stomack protein in Atlantic salmon (Salmo salar) fed diets of either intact or pepsin predigested cod muscle protein ; Carotenpod accumulation in Atlantic salmon fed diets with maize gluten, pea or rapeseed ; The influence of dietary lipid sources and vitamin E on iron status in postsmolt atlantic salmon (Salmo salar) ; The contribution of supplementary sea water to the mineral balance of atlantic salmon alevins ; Haematological values and chemical composition of halibut (Hippoglossus hippoglossus L.) fed six different diets ; Fatty acid composition of glycerophospholipids and neutral lipids in six different tissues of halibut (Hippoglossus Hippoglossus) fed capelin at constant temperature ; Biological availability to rats of selenium from cod (Gadus Morhua) and selenomethionine relative to sodium selenite Von Der Decken, Alexandra; Espe, Marit; Lied, Einar; Hatlen, Bjarne; Storebakken, Trond; No, Hong Kyoon; Krogdahl, Åshild; Waagbø, Rune; Maage, Amund; Torrissen, Ole J.; Shearer, Karl D.; Hemre, Gro-Ingunn; Bjørnson, Bjørn; Lie, Øyvind; Knudsen, Eva Rosendal; Lorentzen, Mette; Julshamn, Kåre (Fiskeridirektoratets skrifter, Serie ernæring;Vol. 5, No. 2, Working paper, 1992)
The stability and biological availability of different forms of vitamin C in feed to Atlantic salmon (Salmo salar) ; Growth and chemical composition of Atlantic salmon (Salmo salar) given a fish meal diet or a corresponding free amino acid diet ; A comparison of tissue levels of four essential trace elements in wild and farmed Atlantic salmon (Salmo salar) ; Digestibility determination in atlantic halibut (Hippoglossus hippoglossus) ; A note on the amino acid distribution in fish silage layers Waagbø, Rune; Øines, Sigurd; Sandnes, Kjartan; Espe, Marit; Njaa, Leif Rein; Maage, Amund; Julshamn, Kåre; Ulgenes, Yngve; Berge, Gerd Marit; Krogdahl, Åshild; Strømsnes, Øystein; Grønseth, Frank Arne; Myhre, Pål; Austreng, Erland; Haaland, Herborg (Fiskeridirektoratets skrifter, Serie ernæring;Vol. 4, No. 2, Working paper, 1991)