Mowi funds three-year genetic study after Gorsten escape.
The River Lochy Association and Mowi Scotland have agreed a long-term scientific monitoring programme to assess potential impacts from the escape of farmed salmon from Mowi’s Gorsten site in Upper Loch Linnhe in October.
The study, which will be funded by Mowi and carried out in collaboration with the Institute for Biodiversity and Freshwater Conservation at UHI Inverness, will focus on the salmonid population within the Lochy and Leven catchments and wider Upper Linnhe system.
The move follows an incident on 5 October 2025, when an estimated 75,000 Atlantic salmon, with an average weight of 860 grams, escaped from Mowi’s Gorsten farm during Storm Amy. The fish were described as sexually immature and of RAS (recirculating aquaculture system) origin, with a “very low level of survival in the wild expected,” according to the company.
In the immediate aftermath of the escape, Mowi and the River Lochy Association coordinated a rod-based recapture effort rather than the use of nets, due to high river levels and the proximity to the salmon and trout spawning season. More than 100 anglers were deployed across local and more distant rivers, with all captures reported via the Fisheries Management Scotland escape reporting app.
As of publication, 440 escaped fish had been reported as recaptured, all immature fish weighing between 0.5 and 2.5 kilograms, with the majority taken in the lower reaches of the Rivers Lochy and Leven.
Under the new agreement, the parties have defined a three-year monitoring plan intended to detect any genetic signal from the escape in the wild salmon population.
In 2026 and 2027, scale samples will be collected from the majority of rod-caught returning adult salmon in both the Lochy and Leven. These samples will be genetically screened against the Gorsten farm stock “to ascertain the level (if any) of farmed fish from this escape in the returning adult fish from the ocean.”
Also in 2026, fisheries biologists will carry out timed electro-fishing surveys across all major salmon catchments in the Upper Linnhe region, sampling fry for genetic analysis. This work, using 58 established fry monitoring sites, will form a baseline “pre-incident” survey. Between 20 and 30 fry will be sampled at each site using non-lethal caudal fin clips taken from anaesthetised fish.
The fry sampling will be repeated in 2027 and 2028, with those years used “to detect the genetic impact (if any) in the wild population from this escape event.”
“Obviously an escape of farmed salmon into the wild is something that nobody wants to see,” said Jon Gibb, manager of the River Lochy Association and director of the Lochaber District Salmon Fishery Board.
“But I am confident that between Mowi and the River Lochy Association, the local wild fishery management body, that we have designed a comprehensive three-year genetic monitoring plan that will definitively identify whether there will be any impact whatsoever from this unfortunate incident on the local wild salmon population.”
Stephen MacIntyre, head of environment at Mowi Scotland, said: “While we are disappointed this incident occurred, we acknowledge our responsibility to monitor and assess the potential for any adverse impacts on local wild salmon populations. Using this scientific approach, the monitoring study will determine whether there is evidence of any changes in the genetic composition of wild salmon arising from the escape incident. We look forward to supporting the delivery of the study with the River Lochy Association over the next three years.”
