Escaped salmon outnumber wild fish in some rivers after 2024 breach.
The proportion of escaped farmed salmon in Norwegian rivers rose in parts of the country in 2024, driven largely by a single escape event near the Trondheimsfjord in May, according to new data from the national monitoring programme led by the Institute of Marine Research.
“This was the highest recorded share of escaped salmon in rivers in Trøndelag and Møre og Romsdal since we began monitoring in 2014,” said Kjell Rong Utne, a researcher involved in the programme.
Seventy percent of the escapees detected in rivers around the Trondheimsfjord were linked to that single incident, with the remainder attributed to other sources. Elsewhere in the country, the proportion of escaped salmon in rivers was broadly in line with 2023 levels.
Despite the regional increase, Utne noted that the national average for escaped salmon over the 2020–2024 period remained stable.
The annual monitoring covers 196 selected rivers using methods including snorkel counts and scale sample analysis. In 2024, 136 rivers yielded data of sufficient quality for analysis.
Scale samples submitted by recreational anglers are a key data source. “We rely on anglers to help us gather data, especially in years with low wild salmon returns like 2024,” Utne said. Restrictions on river fishing due to low wild salmon numbers reduced the number of samples collected last year.
Rivers are categorised as having low, medium or high levels of farmed salmon presence. Medium to high levels were observed in rivers from Vestland to Troms, while all rivers surveyed in Rogaland, Finnmark and along the Skagerrak coast recorded low levels.
The monitoring programme is intended to assess the extent of escapee interbreeding risks with wild stocks and guide management responses. “It provides a national overview of where challenges are greatest, and supports efforts by the Directorate of Fisheries to manage impacts from aquaculture,” Utne said.
The report is produced annually by the Institute of Marine Research in cooperation with NINA, NORCE LFI, Rådgivende Biologer, the Veterinary Institute, and additional data providers including Skandinavisk Naturovervåkning and Naturtjenester i Nord.