River lamprey (Lampetra fluviatilis)
|Size||Head-body length at spawning: 17 - 50 cm (2)|
Classified as Least Concern (LC) on the IUCN Red List (3). Listed on Annex III of the Bern Convention, Annexes II and V of the EC Habitats Directive and Schedule 3 of the Conservation Regulations (1994) (4).
Lampreys are some of the most primitive vertebrates alive today. They are known as cyclostomes, which means 'round mouths' and refers to the fact that they are jawless, having instead a round sucker-like mouth. A further primitive characteristic is that the skeleton consists of cartilage and not bone (2). Lampreys are similar in shape to eels, and have a series of uncovered round gill openings (known as gill pores) on the sides of the head. The river lamprey can be distinguished from other lampreys as it has two separate dorsal (back) fins, and just a few teeth around the mouth. It is bluish grey or green on the back and sides (2) and the underside is white (5). The larval stages of different lampreys are very similar in appearance (2).
In the UK the river lamprey has a wide distribution, and is known in many rivers south of the Great Glen, Scotland. Elsewhere the species is found in Western Europe from the western Mediterranean north to Norway, Sweden and Finland (3) (6).
The river lamprey inhabits high quality rivers (6).
Although some populations exist where the entire life cycle takes place in freshwater, generally the river lamprey is anadromous; the adults migrate to the sea and return to freshwater to spawn. Upon reaching a suitable breeding area, a male wriggles around and creates a depression on the riverbed. He then attaches to the back of a female's head with his mouth and wraps around her body. The eggs are deposited, fertilised externally and covered with sand, a succession of males are involved and one female can lay up to 25,000 eggs in this way (7). After spawning the adults die. The blind juveniles hatch and then spend four to six years buried in the substrate, filtering organic particles from the water (7). After they mature the adults travel to the sea where they live for about two summers before returning to spawn. Whilst at sea, they feed on fish flesh and bodily fluids by attaching to small fishes with the sucking mouth and rasping away at the flesh (5). Roman, Viking and Medieval Britons regarded river and sea lampreys as delicacies (8).
Pollution, river engineering works and changes in land use have impacted upon this species (2).
The strong UK populations are internationally important, and their protection is fundamental if the species is to be conserved in the EC (6). A number of areas have been proposed as candidate Special Areas of Conservation (SACs). The areas chosen support strong populations and reflect the geographical range of the river lamprey in the UK as well as the range of habitat features required by the species (6). Although this should help to improve the conservation status of this primitive fish in the UK, it has been noted that further measures will be required to maintain the species (6). Draft Action Plans have been produced for the three lamprey species found in the UK in order to guide their conservation (2). Furthermore, the Life in UK Rivers Project is helping to conserve this species.
For more on the Life in UK Rivers Project see:
- English Nature:
Information authenticated by the Environment Agency:
- Anadromous: in fish: those species that spend most of their lives at sea but migrate to fresh water to spawn.
- Larval: of the stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Vertebrates: animals with a backbone.
IUCN Red List (December, 2009)