The survival of wild Atlantic salmon at sea has fallen to critically low levels, with fewer than three in every 100 fish now returning to British rivers to spawn, according to new research from the Game & Wildlife Conservation Trust (GWCT).
Drawing on more than 20 years of monitoring data from the River Frome in Dorset, the study found the marine environment has become the greatest threat to the species’ survival.
“We believe declining marine survival is driven by warming seas affecting feeding opportunities for salmon at sea,” said Dylan Roberts, GWCT Head of Fisheries
“We’re also very concerned about the potential high risk of young salmon being accidentally caught in commercial factory fishing nets.
“We know from our research that the largest, fittest smolts are three times more likely to return as adults. So, if you get the habitat right, this can help improve the very low marine survival we have been witnessing in recent years.”
Since 2005, researchers have tagged around 10,000 juvenile salmon each year at the Trust’s East Stoke monitoring station, tracking their migration to sea and eventual return as spawning adults.
On average just 3% of salmon now survive their time at sea and return to freshwater after one winter, while only 1.5% return after two winters. In some years, survival has fallen even further, with returns dropping to just 0.4% and 0.7% respectively. By comparison, overwinter survival in rivers during the fish’s early life is around 80% higher, underlining the growing importance of conditions at sea.
Researchers also reported a sharp decline in the number of juvenile salmon available for tagging, with catches falling from 10,000 in 2023 to just 3,226 in 2025.
The findings support calls from the Missing Salmon Alliance for stronger protection of marine migration routes, action to reduce bycatch and greater investment in research into climate-driven changes in the ocean.
“What we really need is a concerted national effort to save this much-loved species before it’s too late,” said Roberts.
