European Brook Lamprey

The European brook lamprey (Lampetra planeri) is a small, non-parasitic jawless fish widely distributed across freshwater streams of Europe, from the British Isles east through central and eastern Europe. It is closely related to the river lamprey (Lampetra fluviatilis) and is considered by many researchers to be a non-migratory, freshwater-resident ecological form of the same evolutionary lineage, though the two are generally treated as distinct species. Unlike its parasitic relative, the European brook lamprey completes its entire life cycle within small streams, never migrating to sea and never feeding once it reaches the adult stage. Its larvae, which strongly resemble those of the river lamprey, spend several years buried in stream sediment before a brief, non-feeding adult phase focused solely on reproduction.

European brook lampreys are small stream-dwelling lampreys distinguished from their parasitic relatives mainly by size and tooth development.

Key field marks:

• Weak, blunt teeth on the oral disc, in contrast to the sharp, well-developed teeth of the parasitic river lamprey
• Small circular sucker mouth relative to body size
• Dark grey-brown to olive back, fading to a pale cream or yellowish belly
• Two closely spaced dorsal fins near the tail
• Seven round external gill openings on each side of the head
• Adults typically 10-15 cm, distinctly smaller than the river lamprey

Because larvae of the European brook lamprey and river lamprey are nearly identical, reliable identification generally requires examining mature, breeding adults for tooth development and body size.

European brook lampreys inhabit small, clean, well-oxygenated streams and headwaters throughout much of Europe, favoring reaches with a mix of gravel riffles for spawning and soft silty or sandy margins suitable for larval burrowing. They are highly sensitive to water quality and are often considered an indicator species for healthy, unpolluted stream ecosystems. Unlike the anadromous river lamprey, they never leave fresh water, spending their entire multi-year life cycle within a single stream system. Larvae remain buried in fine sediment for the majority of their lives, only emerging as short-lived adults to spawn in nearby gravel-bottomed shallows.

European brook lamprey larvae, known as ammocoetes, live burrowed in soft stream sediment for several years, filter-feeding on algae, detritus, and microorganisms. Following metamorphosis, adults enter a brief, non-feeding stage during which their digestive tract regresses, relying entirely on energy reserves built up during the larval period. Adults move short distances to nearby gravel riffles, where they build simple nests by shifting stones with their sucking mouths, then spawn communally in groups, after which all adults die within days to weeks. Because they never feed as adults, European brook lampreys have no parasitic relationship with other fish. Their larvae serve an important ecological role in nutrient cycling and as a food source for other stream-dwelling species.