LONDON -- England's Atlantic salmon population has sunk to a record low, the latest indicator that its marine and freshwater ecosystems are dirty and polluted, Britain's Environment Agency (EA) said on Monday.

The large, silvery fish are found in the northern Atlantic Ocean and rivers that flow into it, but about 90 percent of principal salmon rivers in England are classified as "at risk" or "probably at risk".

That means salmon numbers are below the minimum needed to support sustainable populations - a sign that more needs to be done to improve England's natural environment, the EA said.

It blamed agricultural pollution, sedimentation, chemical runoff from industries, wastewater and roads for degrading salmon habitats, while calling on farmers, landowners and the water, energy and waste industries to do more to protect the species.

The dumping of raw sewage in rivers and seas has sparked anger in Britain against privatised water companies, which are accused of routinely dumping waste in waterways and failing to invest in infrastructure.

"Forty years ago an estimated 1.4 million salmon returned to UK rivers each year. We are now at barely a third of that – a new low and evidence of the wider, growing biodiversity crisis," EA Chair Alan Lovell said.

"We need all those who pollute to clean up their act," Lovell said, noting that new legislation - the Water (Special Measures) Bill - will give the EA more powers to hold polluters to account.