Watch out for blood sucker of the rivers

A surfeit of lampreys once killed a King and in modern times they have had a mixed press. Some lurid headline writers call them vampire fish.

A lamprey takes it meals in an unusual manner. It will fasten on to another fish by suction and, with its serrated tongue, drill through its prey to suck out its blood and body fluids. They can also climb out of the water. A unique opportunity to see this happening may bring out naturalists, as well as the merely curious, to a small East Yorkshire nature reserve in the coming weeks.

Lamprey are not actually fish at all. They are part of the Petromyzonidae family, a small but important group known as Agnatha, the most primitive of all living vertebrates.

These eel-like creatures can climb vertically. But in Yorkshire the task is less demanding. A water ramp has been installed as a trial at a concrete tidal barrage near Barmby on the Marsh. The bottom of the stainless steel ramp is submerged in the River Ouse. The plan is that the lampreys will emerge from the water, attach the powerful suckers in their mouths to the metal and then, using their tails, suck-and-shuffle their way to the top.

Most lamprey are anadromous, meaning they spawn in freshwater but complete part of their life cycle at sea. Their climbing ability comes in handy when they become stuck on their migratory journey. Ramps to assist their passage have been put in place at hydro-electric dams and other structures in the United States. This idea has now been borrowed and used in this country for the first time.

At the top of the Barmby ramp, the lamprey enter a collection chamber containing a basket. This is removed and the lamprey within are released in to the River Derwent on the other side of the barrage, enabling them to continue their journey to their spawning grounds upstream.

Dave Bamford, a fisheries technical specialist for the Environment Agency, explains that this is a pilot project. The information it provides will enable further research to be carried out. "We know that thousands of river and sea lampreys travel from the Ouse into the Derwent at various times of the year," he says. "Since the tidal barrage was built in 1975, they've had to find a way under the barrage gates.

"But we have absolutely no idea how many will make use of the new ramp. If it proves to be successful, these ramps could be used at other sites across the county."

The migratory season for sea lampreys starts any day now. So Dave and his colleagues should get an indication of whether the ramp is doing its job pretty soon. Once through the tidal barrage, sea lampreys look to spawn in gravelly areas in the Derwent. Some of the largest spawning sites are at Stamford Bridge and Boroughbridge.

"They start their migration as soon as the water starts to warm up a little in spring," adds Dave. "Although we are checking the collection chamber on a daily basis now, the water is a little cool for the time of year, so the migration may not really get under way until April or even May this year.

"Some of the larger sea lampreys are thicker than an adults' arm and can give people quite a shock when they see them for the first time. They look so alien to anything else that you would see in the river and are actually quite unpleasant-looking creatures."

The smaller river lampreys won't begin their migration upstream until late September at the earliest. There's also the brook lamprey, a freshwater species, which is the most common sort in this country.

Migratory lampreys only began to return to the Humber and the Ouse in the 1990s when the estuary became cleaner. Prior to that, they'd been largely absent from our rivers for around 50 years.

Dave says: "Lampreys survived the years when pollution was at its worst because of the fact that they will spawn anywhere and don't have to return to a specific site in the way that salmon do. They date back to pre-historic times and are really hardy creatures.

"Research from the US has shown that they can even make their way up vertical ramps, providing there is some water flowing over it. At the Bonnville Dam in Oregon, lamprey travel more than 50 metres over a series of ramps and resting areas."

Sea lampreys became a serious pest in the American Great Lakes. The river lamprey is found only in western Europe and the UK population is important for its conservation.

The Romans enjoyed eating them and today they are on the menu in Portugal and Germany and coastal parts of France. Here, Gloucester was the centre of an important lamprey fishery from the days of King John and, each Christmas until the 1830s, the city presented a Royal Lamprey Pie to the reigning sovereign. They sent one to the Queen for her Silver Jubilee in 1977.

King Henry I died from eating lampreys at Rouen in Normandy in 1135. This may have been toxic poisoning from inadequate cooking.

Unsuspecting visitors to the attractive nature reserve at Barmby on the Marsh could well be in for a surprise when the first lamprey finds its way up the new ramp.