A SPECIES of fish has returned to the River Tees after an absence of more than 80 years.

The Environment Agency said the discovery of sea lampreys proves the river now has excellent water quality.

Five of the eel-like predators were found in the fish trap at the Tees Barrage, Stockton.

Bob Pailor, environment manager for the Environment Agency, said: "We are delighted at this discovery. The improvements to water quality have clearly made a real difference.

"Lampreys have an unpleasant reputation, feeding on and sucking out the insides of other fish, but they are a vital part of nature's balance between predator and prey.

"The fish also have royal connections, allegedly being responsible for the deaths of King John and King Henry 1, after their overeating of lampreys."

Sea lampreys were abundant in the Tees prior to the 1920s, but were driven out by untreated industrial effluent and domestic sewage discharges into the lower Tees, above the estuary, when all river life was wiped out.

Now they have been found sucking on the steel walls of the barrage, leaving imprints.

The Environment Agency said numbers of other pollution-sensitive species are increasing, with more sea trout salmon and fish-eating seals being recorded over the past decade.

Otters have also reappeared and can occasionally be seen.

The agency said local chemical and steel firms and Northumbrian Water have worked to reduce discharges, and clean and regenerate the river.