An endangered species of fish known as the lamprey has returned to UK rivers for the first time since the 1800’s. ( although a dead lamprey was found in the Thames in 2009.)
What does this mean for wildlife in the UK though? Well it means that it is probably worse to be fish now than it was before. A lamprey is a parasitic fish, it sucks the blood of other fish using its rasping mouth. It is also ancient as it is thought to have been around since 200 million years before the dinosaurs. For this reason it has a lot of admirers in the scientific world. It has no jaw, and no true fins or bones. It’s often called a jawless fish or an eel but really it is just a lamprey, part of the agnathan superclass in phylogenetic terms. Its evolution is something lots of us studied at university and its mouth is like something from a sci-fi film.
Lampreys live in the sea and return to rivers to spawn before they die, much like salmon. Like salmon, they are also a delicacy, particularly amongst royals. It was the lamprey that reportedly caused the death of King Henry the first of England in 1135 due to food poisoning. Lamprey pie has since been served at Queen Elizabeth the II’s coronation and diamond jubilee, although the lamprey was imported.
As far as we know humans are the only predators of adult lampreys. The young lamprey’s are born in rivers and lay in the sediment feeding on detritus for up to 6 years before undergoing a metamorphosis into an adult. In the larval stage they are predated upon by many river fish such as trout or pike, but adults, which grown up to 1 metre long, appear to have no natural predators. They are classed as invasive in the United States and have done significant damage to the fish populations of many US lakes after being accidentally introduced. Despite being endangered they are being removed in the US due to damaging salmon populations.
The reason for their return is thought to be better water quality and less obstruction. The Environment Agency says UK rivers are now cleaner than ever and the removal of weirs has aided lamprey recovery. They have also implemented “lamprey tiles” to help the lampreys move upstream. The lamprey pulls itself up these tiles using its mouth for suction before pulling its body up.
It is unlikely the lamprey will do dramatic damage in the UK as it is a native species and larger fish will control its population at the larval stage.
If you do a lot of fishing in England though you might want to wear gloves just in case, those teeth look sharp!