Sea lice

Sea lice are the most common parasite on farmed salmon, and the biggest health issue for the industry. For a number of years, oral and bath treatments have been used to combat sea lice. Our monitoring of sea lice shows that their numbers are increasing noticeably, and that in some cases they are developing resistance to the favoured treatment.

Sea lice belong to the copepod family, and are found naturally throughout the northern hemisphere.

Sea lice have affected salmon fishing for a long time, being first mentioned in the 17th century. The zoologist Henrik Nikolai Krøyer described the species and gave it the Latin name Lepeophtheirus salmonis in 1837.

Sea lice are host-specific, and depend on salmonids to complete their life cycle. The saltier the water, the more they thrive, and they fall off the salmon when the fish head up river. When…

Facts about sea lice

Latin name: Lepeophtheirus salmonis
Distribution: occur naturally in Norwegian waters. Their numbers have risen significantly in parallel with the growth of the aquaculture industry.
Biology: sea lice are parasites with ten life stages, three of which are free-swimming, four of which are stationary and three of which are mobile. They attach themselves to salmon in the third life stage.
Size: adult female: 12 mm (approx. 29 mm including egg strings); adult male: 6 mm.
Diet: the skin and blood of salmonids. The lice only start feeding when they have attached themselves to a host fish (stationary and mobile stages).
Reproduction: all year round, but reproduce increasingly quickly as temperatures rise in spring.
Dispersal: free-swimming stages spread on currents in fjords and coastal waters.
Treatment: biological methods (wrasse) or chemicals (medication).

Contact

Karin Boxaspen

55 23 86 46

95066856

Sea lice – an unknowable factor

Sea lice

Facts about sea lice

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