A PREHISTORIC fish, that was around 200 million years before dinosaurs, has been seen in the River Avon for the first time since the 1800s.

Lampreys, the fish said to have been responsible for the death of King Henry I, are staging a resurgence.

The snake-like creatures, with a circular disc of razor sharp teeth instead of jaws, were long regarded as a royal delicacy and virtually wiped out in English rivers as a result of pollution and the construction of weirs that prevented them reaching their spawning grounds upstream.

The Environment Agency said improving water quality and efforts to reduce such obstacles meant lampreys that had been confined to estuaries were now returning to some rivers in the country.

Fished for hundreds of years in the UK, the lampreys are particularly renowned as a luxury food.

King Henry I was said to have died after gorging on a surfeit of lampreys while King John is supposed to have fined the City of Gloucester the equivalent of £250,000 for failing to deliver his Christmas lamprey pie.

Lampreys are now slowly returning to their old habitats, thanks to the lowest levels of pollution for more than 100 years and the Environment Agency’s work to remove some river structures like weirs.

Environment Agency fisheries expert Simon Toms said: “For the last 200 hundred years, some rivers have not been capable of supporting lamprey species as a result of water quality, poor habitat and man-made barriers.

“Now that water quality has improved and some of these barriers have been removed we are seeing lampreys return to the upper reaches of rivers such as the Ouse, Trent, and Derwent, where they were absent as recently as 30 years ago.

“These are fascinating fish, living fossils, that have a special place in the history and traditions of this country, and we hope that with a helping hand from us they will be able to thrive in England’s rivers once again.”

As well as being a fascinating ancient species, lampreys are ecologically important in helping to process nutrients in rivers as well as a food source for fish and birds, such as herons and Sawbill ducks.