Lampetra fluviatilis, L. planeri and Petromyzon marinus
The lampreys (family Petromyzonidae, stone suckers) belong to a small but important group known as Agnatha, literally jawless, the most primitive of all living vertebrates. They are not true fish, since they have no lower jaws and the mouth is surrounded by a round, sucker-like disc within which, in the adults, are strong, horny, rasping teeth.
Lampreys are always eel-like in shape,
but have neither paired fins nor scales. They have no bones, all the skeletal
structures being made up of strong, flexible, cartilage. There is only
one nostril, situated on top of the head, just in front of the eyes, the
latter rarely being functional or even visible in the young. The gills
open directly on each side of the head (there is no gill cover or operculum)
forming a row of seven gill pores behind each eye.
The river lamprey is found only in western Europe, ranging from southern Norway to the western Mediterranean, in coastal waters, estuaries and accessible rivers. The species is mainly anadromous but there are a few land-locked, non-migratory populations isolated from the sea in Finland, Russia and Scotland. The species has disappeared from many rivers due to pollution, river engineering and various impassable barriers (weirs, dams, etc.).
In Britain, the ammocoetes of river lampreys occur in silt beds in many rivers and, occasionally, in suitable silts in large lakes. They are absent from a number of rivers because of pollution or obstacles that the adults cannot surmount during the spawning migration, such as natural waterfalls or artificial dams. The river lamprey has declined in Britain over the last hundred years and, though not yet distinctly threatened, is in need of general conservation measures to restore populations to their former status.
The brook lamprey is a purely freshwater species occurring in streams and, occasionally, lakes in northwest Europe, particularly in basins associated with the North and Baltic seas. Although it is the most common of the British lampreys and occurs over much of the British Isles, it is apparently absent from much of Scotland north of the Great Glen.
Because of a decline in several parts of Europe, the brook lamprey is now given some legal protection. It is listed in annexes IIa and Va of the Habitats Directive, Appendix III of the Bern Convention, and as a Long List Species in the UK Biodiversity Action Plan.
The anadromous sea lamprey occurs over much of the Atlantic coastal area of western and northern Europe, from northern Norway to the western Mediterranean, and eastern North America. It is also found in estuaries and easily accessible rivers in these regions. Occasional specimens are taken in midwater in the Atlantic Ocean.
In the British Isles it is absent from northern rivers (it does not appear to occur north of the Great Glen in Scotland), and has become extinct in a number of southern ones due to pollution and engineering barriers. There are several landlocked populations in North America, but in Britain the only site where the species is known to feed in freshwater is Loch Lomond.
Because of its decline across Europe, the sea lamprey is now given some legal protection. It is listed in annexes IIa and Va of the Habitats Directive, Appendix III of the Bern Convention, and as a Long List Species in the UK Biodiversity Action Plan.
|Andy Strevens/Environment Agency|