A project to dismantle and take away a weir has helped fish to breed more successfully, environmental groups have said.
The project, on the River Ecclesbourne, near Duffield in Derbyshire, saw the weir - built in the 1970s - removed.
Experts said it had blocked salmon from swimming upstream where they lay their eggs in shallow water.
The work was completed in October, but experts suggested there was already evidence it had been successful.
The weir removal is one of 16 barriers taken apart in the last year in work funded by a government grant and, in part, by the rod licence.
Dr Tim Jacklin, conservation officer at the Wild Trout Trust, said: "We were delighted in early January when somebody brought to our attention that they'd found a salmon upstream.
"It was a fish that had died. It had been probably killed by an otter but it was an adult salmon that was probably around 10-12lbs [4-5kg] in weight when it was fully intact.
"And it looked like that had completed its spawning so that's great news that the fish pass had worked so quickly."
He added the project was "a really good story for nature conservation and nature recovery".
"There's not a lot of good news stories about biodiversity and nature at the moment but this is something that's on our doorstep in the Midlands: an iconic fish like the salmon being restored to its rightful position in the rivers of the Trent catchment.
"The more of that habitat we can open up, the more sustainable and resilient that population becomes.
"It's not just about the fish.
"Those salmon are bringing nutrients from the sea back up into the systems and their young fish are providing food for all sorts of other organisms like otters, kingfishers and herons."
Simon Ward, fisheries technical specialist at the Environment Agency, said: "All of a sudden, people are really engaged with the river, which is brilliant."
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