Sea lice complicate salmon farming as treatment imports rise

Imports of medicines used to kill lice on farmed salmon are increasing, as sea lice continue to trouble the aquaculture industry, KVF reports.

Kirstin Eliasen, a researcher and department head at Firum, said salmon lice and sea lice are two different species. Salmon lice are much larger and attach only to salmonid fish, including farmed salmon and trout. Sea lice also attach to farmed salmon and trout, but affect many other fish species as well.

Figures from the Pharmacy Service show that two medicines are especially commonly imported for treating lice on farmed salmon: Slice, which contains emamectin, and Salmosan, which contains azametiphos.

Slice is mixed into feed and used mainly against sea lice, rather than salmon lice. Salmosan is a bath treatment for salmon lice and can also be used against sea lice.

The two types of lice affect farmed salmon differently, Eliasen said. The industry itself largely produces salmon lice, while sea lice often appear to arrive from outside, carried in by a fish stock. Sea lice are often more common in winter, but outbreaks vary greatly from year to year and are difficult to predict.