A blood-sucking beast without jaws or bones and teeth shaped like bottle-openers, the stone-sucker is a fish to stir the imagination and make your skin crawl. Lampreys, as they are more commonly known, are curious creatures that barely classify as fish at all; with cartilage instead of a skeleton, circular gill holes and scale-less skin they are as much like a trout as a cat is like an elephant. I do like to defend the underdogs in nature and personally find the over-saturation of panda/lion/chimp (etc.) conservation propaganda to be greatly irritating. As such, I want to draw attention to these much over-looked creatures that are just as important to our freshwater ecosystems as famous species like salmon – not to mention they suck blood, a bit like Dracula, and I think hallowe’en or something is soon so there is a tie-in there somewhere. Three species of Lamprey can be found in British waters; the small and common Brook Lamprey, the larger and more coastal River Lamprey and the huge, fish-killing and seldom seen Sea Lamprey.

You have a good chance of seeing a Brook Lamprey (Lampetra planeri) in most rivers; however, like all of their kind they are rather sensitive to pollution so clear, fresh streams are the best. Preferring gravel-bottomed streams for breeding, this species is actually completely harmless despite possessing teeth – the adult does not feed at all but does use its sucker-mouth for moving stones when nest-building. Once the adult has laid its eggs on the stream-bed the young larvae (ammocoetes) then spend up to five years buried in the mud feeding; they are blind and toothless and were once thought to be a completely separate species named ‘Prides’.

Lamprey flashing his pearly whites

The large, and definitely blood-sucking, River Lamprey (Lampetra fluviatilis) is very similar to its smaller cousin in appearance but has quite a different life-cycle. The adult Lampern (as it is also known) spends a good few years chewing on the flanks of fish in the sea, not far from the coast, until it feels the yearn to breed and hitches a lift upon a migrating fish such as a trout up a river to its spawning grounds. Female Lamperns may lay up to 20,000 eggs at a time; and in the 18th century they needed every egg because they were a particular delicacy at the time – over a million a year were caught in the Thames alone. This species is perhaps most famous – or rather infamous – for being apparently responsible for the death of king Henry 1st in 1135 after he consumed a ‘surfeit of Lampreys’ – having been especially fond of them grilled.

The rarest species is the Sea Lamprey (Petromyzon marinus), which does spawn in rivers but spends most of its life far out to sea sucking the blood of large fish to the point where it may actually kill its host. This is perhaps not surprising since this species can grow to nearly a metre long and be as thick as a man’s arm – with nasty radiating spikes of teeth in its sucker pad. It is quite vulnerable to pollution and blockages such as weirs on rivers, which impede migration. Because of this it has declined in some of its range and disappeared from some rivers entirely.

Being indicative of clean water in a river, we should (despite their disturbing appearance) be thankful to find these slithy fish making their home in Britain; keep an eye out in likely streams and appreciate their contribution to the diversity of life.