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Salmon louse

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Title: Salmon louse  
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Subject: Salmon, Nanophyetus salmincola, Plankton, Brevetoxin, Fish diseases and parasites
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Salmon louse

Salmon louse
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Maxillopoda
Subclass: Copepoda
Order: Siphonostomatoida
Family: Caligidae
Genus: Lepeophtheirus
Species: L. salmonis
Binomial name
Lepeophtheirus salmonis
(Krøyer, 1837) [1]
Synonyms [1]
  • Caligus pacificus Gissler, 1883
  • Caligus salmonis Krøyer, 1837
  • Caligus stroemii Baird, 1847
  • Caligus vespa Milne-Edwards, 1840
  • Lepeophtheirus pacificus (Gissler, 1883)
  • Lepeophtheirus stroemii (Baird, 1847)
  • Lepeophtheirus uenoi Yamaguti, 1939

The salmon louse, Lepeophtheirus salmonis, is a species of copepod in the genus Lepeophtheirus. It is a sea louse, a parasite living on salmon. They are also known as "sea lice". It lives off the mucus, skin and blood of the fish.[2] They are natural marine parasites of fish, such as adult salmon.[3] They are similar to plankton and ride on the waves.[4] When they encounter a marine fish they adhere themselves to the skin, fins, the gills of the fish, and feeding off the mucous or skin.[5] Sea lice only affects fish and not harmful towards humans.[6]

Life Cycle

There has been some research on the problems caused by this species in aquaculture, but little is known about the salmon louse's life in nature. It has been shown, however, that salmon louse infections in fish farming facilities can cause epizootics in wild fish.[7]

The life cycle consists of 8 stages,[8][9] with ecdysis in between. The first two stages are free swimming nauplius I and II, where it has a length between 0.54 and 0.85 mm.[10] The third stage is the copepodit stage, in which the length is ca. 0.7 mm, and the salmon louse attaches itself to the fish. Stages IV and V are the chalimus stages. The salmon louse eats from the fish, and grows to a length of 5 mm for the males, 10 mm for the females. Each generation takes about six weeks at a temperature of 10–12 °C (50–54 °F). In the pre-adult and adult stages (stage VI to IIX), the sea louse is now mobile, and it becomes possible to differentiate males and females.


The thorax is broad and shield shaped. The abdomen is narrower, and in the females, filled with eggs. The females also have two long egg strings attached to the abdomen. The salmon louse uses its feet to move around on the host or to swim from one host to another.

Effects on salmon farms

This parasite is one of the major threats to salmon farmers. Salmons are stocked year around with hundreds to thousands of them contained in small areas of net-cages.[11] Salmon farms are an unusual, but ideal environment for the sea lice to breed.[12] The infestations of sea lice in salmon farms increases the number of lice in the rest of the surrounding water dramatically.[13] Sea lice also affects juvenile while salmons from the rivers migrating to the ocean and on the way they pass by the fish farms, the sea lice attaches onto them as well. [14] These young salmon are smaller than a size of a key and not fully developed yet. When the sea lice attaches on the young salmon it can kill them. [15]


In small numbers, Sea Lice cause little damage to a fish although if populations increase on a fish, this can lead to death. The parasites can cause physical damage to the fish's fins, skin erosion, constant bleeding, and open wounds creating pathways for other pathogens. [16] The sea lice may also act as a vector for diseases between wild and farmed salmon. [17] These copepod vectors has caused infectious salmon anemia (ISA) along the Alantic coast.[18] [19] An outbreak of ISA occurred in Chile during 2007 where it spread quickly from one farm to another, destroying the salmon farms. [20]

See also


  1. ^ a b Geoff Boxshall (2013). T. C. Walter & G. Boxshall, ed. (Krøyer, 1837)"Lepeophtheirus salmonis". World of Copepods database.  
  2. ^ Christiane Eichner, Petter Frost, Bjarte Dysvik, Inge Jonassen, Bjørn Kristiansen & Frank Nilsen (2008). ) transcriptomes during post molting maturation and egg production, revealed using EST-sequencing and microarray analysis"Lepeophtheirus salmonis"Salmon louse (.  
  3. ^ "Sea Lice." Marine Institute. Marine Institute, n. d. Web. 10 Dec. 2013. .
  4. ^ "Sea Lice." Marine Institute. Marine Institute, n. d. Web. 10 Dec. 2013. .
  5. ^ "Sea Lice." Marine Institute. Marine Institute, n. d. Web. 10 Dec. 2013. .
  6. ^ "Sea Lice." Marine Institute. Marine Institute, n. d. Web. 10 Dec. 2013. .
  7. ^ Martin Krkošek, Jennifer S. Ford, Alexandra Morton, Subhash Lele, Ransom A. Myers & Mark A. Lewis (2007). "Declining wild salmon populations in relation to parasites from farm salmon" ( 
  8. ^ Lars A. Hamre, Christiane Eichner, Christopher Marlowe A. Caipang, Sussie T. Dalvin, James E. Bron, Frank Nilsen, Geoff Boxshall & Rasmus Skern-Mauritzen (2013). (Copepoda: Caligidae) life cycle has only two chalimus stages"Lepeophtheirus salmonis"The salmon louse .  
  9. ^ "Lakselus: generell biologi" (in Norwegian).  
  10. ^ "Lepeophtheirus salmonis".  
  11. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  12. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  13. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  14. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  15. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  16. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  17. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .
  18. ^ Dannevig, B.H. and K.E. Thorud, Other viral diseases and agents of coldwater fish: infectious salmon anemia, pancreas disease and viral erythrocytinecrosis, in Fish Diseases and Disorders, Volume 3, Viral, Bacterial and Infections, P.T.K. Woo and D.W. Bruno, Eds. 1999, CAB International: Wallingford and New York p. 149-175.
  19. ^ APHIS Veterinary Services, Infectious Salmon Anemia Tech Note. 2002, US Department of Agriculture.
  20. ^ "Sea Lice." Farmed and Dangerous. N.p., n. d. Web. 10 Dec. 2013. .

External links

  • Ecological Genetics of Parasitic Sea Lice University of St Andrews Marine Ecology Research Group
  • Fish farms drive wild salmon populations toward extinction Biology News Net —
  • The Link Between Farmed Salmon, Sea Lice and Wild SalmonWild Salmon in Trouble: Watershed Watch Salmon Society. Animated short video based on peer-reviewed scientific research, with subject background article Watching out for Wild Salmon.
  • The scientific case for changing salmon farmingAquacultural Revolution: Watershed Watch Salmon Society. Short video documentary by filmmakers Damien Gillis and Stan Proboszcz. Prominent scientists and First Nation representatives speak their minds about the salmon farming industry and the effects of sea lice infestations on wild salmon populations.
  • Sea Lice Coastal Alliance for Aquaculture Reform. An overview of farmed- to wild-salmon interactive effects.
  • Salmon Farming Problems Coastal Alliance for Aquaculture Reform. An overview of environmental impacts of salmon farming.
  • Sea Lice and Salmon: Elevating the dialogue on the farmed-wild salmon story Watershed Watch Salmon Society, 2004.
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