Is lamprey a fish?
When is a fish not a fish? When it’s a pride, lampern, nine-eyed eel, juneba, stone grig, or – as it’s more often known – lamprey. For this bizarre and primitive creature, whose fossil record goes back 450 million years, is not really a fish. If you need some convincing, the fact that it doesn’t have many fishy prerequisites, such as paired fins, gills, scales, bones or even jaws, should do it.
What does a lamprey look like?
A lamprey’s vermiform, or worm-like, body is topped with a head that recalls the prehensile lip of an elephant’s trunk. If you ever see one ‘sucking’ onto a jam jar or tank, you’ll marvel at a mouth as alien as anything from a Hollywood special-effects studio. A flexible, rubbery disc bristling with circles of teeth is used – depending on species – to hold onto riverbed rocks or carry out parasitic shenanigans. Most lampreys are fish parasites that attach to their host’s body to rasp away a disc of skin and flesh.
Are there any in the UK?
There are three species in the UK. Sea and river lampreys are ‘anadromous’: they spend some of their life-cycle in marine environments before swimming into fresh water to spawn. Both species are limited in distribution by a requirement for clean rivers with an uninterrupted flow.
By contrast, the smallest of the trio, the brook lamprey, is quite well distributed, and because it spends its entire life history in fresh water it can, to an extent, survive in clean stretches of river above disturbance, pollution and obstacles such as dams.
As a creature, a brook lamprey is as cryptic as they come, being pencil-thick with dour coloration, and under 18cm long. Add to this the fact it spends most of its life buried in the riverbed, venturing out after dark, and you may think seeing one is near-impossible.
How do brook lampreys mate?
All this holds true for 10 months of the year – until spring, when brook lampreys go out with a bang. April and May are peak months for observing them. Introverted animals for most of their life-cycle, they now make up for lost time. When the water temperature hits a magic 10–11°C it triggers an orgy, where dozens (sometimes hundreds) of them materialise as if from the very water itself.
The lampreys gather in stony shallows, often by riffles. It can be difficult to follow the action as the lively lampreys resemble writhing spoonfuls of passionate spaghetti. But by thrashing the riverbed with their tails and lugging larger stones out of the way with their sucker-like mouths, they create a depression, akin to a salmon’s spawning ‘redd’.
Here they tie a knot, the male circling the female’s body with his, as he tries to fertilise the thousand-plus tiny eggs she produces before they sink into the gravel and sand. Shortly after this frenetic final fling, the adults die, their reserves used up.
As if this isn’t weird enough, these lampreys haven’t eaten since they metamorphosed from their filter-feeding larval form at the end of summer. The oddball, eyeless larvae suck microscopic plants, animals and bacteria from the water, and are seldom seen, buried for over six years in silt. Called ammocoetes, they rarely leave the safety of the sediments.
Main image © Peter David Scott/ The Art Agency
