Sea lamprey  (Petromyzon marinus)

The sea lamprey is fairly widespread in UK rivers, but it has declined to extinction in some areas. It is absent north of the Great Glen, Scotland, possibly as it prefers warm water (6). Current strongholds are the rivers Wye and Severn (2). Outside of the UK it is known from most of the Atlantic coastal areas of western and northern Europe between Norway and the Mediterranean. It is also found in eastern parts of North America (6).

Breeds in high quality, deep, fast flowing rivers with clean gravel in which to spawn and a sandy substrate for the larvae to burrow into (6). The adults migrate out to sea (4).