The salmon louse, Lepeophtheirus salmonis, is a species of copepod in the genus Lepeophtheirus. It is a sea louse, a parasite living on salmon. It lives off the mucus, skin and blood of the fish.^[1]

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.^[2]

Life cycle

The life cycle consists of 10 stages,^[3] 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.^[4] 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 to VII 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 VIII to X), 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.

See also

• Aquaculture of salmon
• Atlantic salmon
• Fish diseases and parasites
• Pacific salmon
• Salmon

References

Further reading

• Sea Lice and Salmon: Elevating the dialogue on the farmed-wild salmon story Watershed Watch Salmon Society, 2004.