Norway issue status report on salmon lice impact

Summary report highlights impact of salmon lice on wild fish

The Steering Group assessment on the impact salmon lice have on wild fish, has issued a summarised report to the Ministry of Food and Fisheries (NFD). The summary is based on a report from an expert group appointed by the Steering Group.

A new and more comprehensive assessment will be issued in the autumn of 2019, which will form the basis for NFD’s regulation of the production of salmonids (“traffic noise system”).

However, production area 3, Karmøy – Sotra, is still in the category with the highest risk of mortality on wild salmon caused by salmon lice.

Report emphasis on threat to wild stocks

Four areas are in the middle category, while the rest of the 13 production areas are in the lowest risk category.

Changes in some areas since 2017

As in previous years, the assessments are based on salmon. Of the 13 areas, one area was considered to be in the category with the highest risk of salmon lice impact on the vilaks. Four areas are in the middle category, while the rest of the areas are in the lowest risk category.

Area 3 is still in the category with the highest risk of salmon lice impact. In the previous assessment, area 4, Nordhordland – Stadt, was also in this category. This year this area is in the category “moderate risk of salmon lice infested wild fish mortality”. However, there are areas that have gone the opposite way. Both area 2 (Ryfylke) and 7 (Nord-Trøndelag with Bindal) have gone from the low risk to moderate risk compared to the expert group’s assessment for 2017.

The analysis for the expert group is based on several models and datasets with different strengths and weaknesses. If any of the methods point in different directions, it provides the basis for greater uncertainty. It is important for the expert and steering group to highlight uncertainty in every part as far as possible.

A majority of sites are in the low-risk category

A total of eight out of 13 areas are in the low-risk category (<10% mortality) for impact on wild ax:
· Swedish border – Jæren (area 1)
· Nordmøre – Sør-Trøndelag (area 6)
· Helgeland – Bodø (area 8)
· Vestfjorden and Vesterålen (area 9)
· Andøya – Senja (area 10)
· Kvaløya – Flea (area 11)
· Western Finnmark (area 12)
· East Finnmark (area 13)

The areas Ryfylke (area 2), Nordhordland to Stadt (area 4), Stadt to Hustavika (area 5) and North Trønderlag with Bindal (area 7) have moderate risk (10-30% mortality). The area of ​​Karmøy to Sotra (area 3) is at high risk for wild salmon (> 30% mortality).

Uses available knowledge of impact on wild fish

The expert group has used data from NALO (National Monitoring Program for Salmonella). The results were drawn from modeled infection pressures and results from models that calculate infection and mortality on wild salmon smolt.

According to the expert group, the main uncertainties are related to the emigration time and emigration route for the various rivers. This can have a significant effect on how much infectious salmon smolt will be exposed in fjords and along the coast.

More data on wild salmon smolts in several production areas will be important to reduce uncertainties, especially where trapped smolt can be traced back to river.

In addition, there are uncertainties related to the threshold values ​​used to calculate salmon lice infested mortality. Part of the model base is newly developed. Validation and quality assurance in the form of publishing, will be important.

Source: NINA

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