Salmon are back in the Mersey after 200 years away
The River Mersey is the cleanest it has been for a century, according to a new Environment Agency report.
The agency's General Quality Assessment (GQA) found that cleaner water had seen the return of salmon to the river for the first time in 200 years.
There was also evidence that otters were returning to the banks of the river in Greater Manchester.
The Mersey was once the most polluted river in Europe, mainly due to industrial waste and sewage.
The GQA report examined the water quality of all of the rivers in England and Wales.
It confirmed that, while the Mersey was the cleanest it's been since the early 1900s, it was still among the 74% of rivers in England and Wales that fell below a new European environmental standard.
Despite this, Steve Moore, the Environment Agency's Regional Strategy Manager in the North West said that
the return of otters
and salmon was something to be very proud of.
Speaking to the BBC, he said: "I think we should celebrate the fact."
"I don't think anyone would have dreamed that salmon would return to the Mersey and the sort of wildlife that we're seeing today would have returned at such speed.
"But what we want is for them to return to all of our rivers."
According to the report, the improvements to the Mersey were largely down to efforts to tackle a variety of different pollutants.
Said Steve Moore: "A lot of sewage has been put into the river in the past [but also] it's been industry, heavy industry where they've been unregulated and polluting. Over the last ten years, we've dealt with a lot of that.
Fish ladders have been installed to help salmon navigate weirs
"More recently, we've been looking at how we deal with run-off from land," he added.
"What we put on farms, in terms of chemicals and pesticides, runs off into rivers and has an impact on the habitats and species that live around the rivers."
The return of the salmon was not just down to the river being clean though. Steve explained that there had also been extensive efforts to make it more navigable for the fish.
"Historically, industries actually blocked our rivers through weirs and various other means, so what we're trying to do is create some passes for those fishes.
"So we have fish ladders, which give salmon particularly the chance to move up the rivers, where they can then spawn and we then get more salmon in the river."
Cleaning up the Mersey had involved not just the Environment Agency but also water companies and industry.
And, while great strides had been made, Steve admitted that there was still a long way to go to improve all the region's rivers.
"It all costs money," he said. "There isn't a bottomless pit of money, so what we're looking for is to work with others to do what we can to open up the rivers more and more to fish and to people."
"There's an extensive network of rivers across the North West and our challenge is to make them all as good as the Mersey."