Norway's Institute of Marine Research launches annual sea lice monitoring drive

Norway’s Institute of Marine Research (IMR) has begun its annual monitoring of sea lice on wild salmonids, including wild salmon, sea trout and sea char, in selected coastal areas.

The work, carried out by IMR in collaboration with two other Norwegian research institutes, Norce and Nina, is led by specially trained personnel who record the prevalence of sea lice and the stages of their life cycle, and the results provide information on how sea lice impacts these wild species.

Sea lice levels are a central factor in Norway’s regulation of aquaculture. In recent years, the Norwegian government’s "traffic light" system has used the amount of lice on migrating young salmon as one measure when assessing fish farming areas.

“The amount of lice in the sea is closely related to the amount of lice on farmed fish in the same area. Where there are a lot of lice, there is also an increased risk of wild salmonids becoming infected,” said Rune Nilsen, head of the National Lice Surveillance (Nalo), in an IMR news release.

This year’s monitoring has started in Rogaland, southern Norway, as in previous years, and will move north as the season progresses, following the migration of salmon smolt from rivers into the sea.

“One of the goals is to investigate whether migrating young salmon (smolt) encounter a lot of lice on their way from the rivers to the sea,” Nilsen explained. “The development of salmon lice is dependent on temperature, so the amount of lice larvae also tends to increase in the spring, at the same time as the smolt migration is taking place.”

Norway’s marine aquaculture sector is divided into 13 production areas, each assigned a colour based on sea lice risk, updated annually, that determines whether farms may expand or must scale back output. The results of the annual IMR survey contribute to the data and models used by the Norwegian authorities in this decision-making process.