An influx of fish believed to be farm escapees in the Menai Strait has raised concerns among anglers and environmental groups, with authorities investigating how the fish entered the area.
According to reporting by North Wales Live, anglers began catching increased numbers of fish in the strait around 26 March, particularly between the Menai Suspension Bridge and the Britannia Bridge linking Anglesey with mainland Wales.
The fish are now believed to be rainbow trout, based on photographs submitted by anglers to Natural Resources Wales (NRW).
Initial reports suggested the fish might be salmon. Because it is illegal to retain wild salmon in Wales, several anglers released the fish after catching them.
Local fishing representatives said the fish display characteristics associated with farmed stocks, including scale patterns indicating artificial rearing conditions.
“It is possible these fish have escaped from a local fishery or a fish rearing facility, although at this stage we do not know which one,” said Huw Jones, environment team leader at Natural Resources Wales, in comments reported by North Wales Live.
He added that visible fin irregularities in the images are typical of stocked trout and suggest the fish may not have travelled far from their release point.
Escapes of farmed fish into open waters occur periodically in the UK, often linked to storm damage or infrastructure failures at aquaculture sites. In October 2025, around 75,000 farmed salmon escaped from a damaged cage at a site in Loch Linnhe following Storm Amy.
Authorities say escaped farmed fish can pose risks to wild populations by competing for food and habitat, introducing disease, or affecting the genetic integrity of native fish stocks.
Natural Resources Wales said reports of the fish in the Menai Strait were first logged on 26 March and the situation is being monitored.