A rare and protected fish has been caught in the River Don for the first time in recent history as water quality in South Yorkshire’s rivers continues to improve.

Two sea lamprey were caught during an Environment Agency fish survey on the River Don at Crimpsall, Doncaster.

Lampreys are an ancient group of eel-like jawless fish that have lived on earth largely unchanged for 300 million years – appearing about 70 million years before the first dinosaur.

The young live in rivers before migrating to the sea - adult sea lamprey then return to the rivers to spawn.

According to the Environment Agency, the fish are a good indication of the high quality of the river water. Breeding populations occur in North Yorkshire and scientists are currently trying to track down their spawning grounds.

Environment Agency monitoring officers were using an electric fishing technique when they came across the sea lamprey. They pass an electric current through the water to temporarily stun the fish so they can be counted, measured and then released unharmed.

In modern times, sea lamprey numbers have declined across Europe. Weirs and dams have prevented adult fish from swimming upstream to their spawning grounds. The Environment Agency and its partners, including the Don Catchment Rivers Trust, are now working on a ‘fish highway’ for the river, where fish passes and weir removals provide free access for all species of fish between the sea and the upper river.