The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Habitat & Distribution
This was a widespread species in UK rivers but it has declined to extinction in some areas. Current strongholds include the Rivers Wye and Severn. This fish is quite scarce in Cornish rivers and waters and the only recent records for Cornwall come from the Tamar, East Looe, Lynher and Camel rivers. The Sea Lamprey, the largest of the anadromous, parasitic lampreys, enters the rivers in the springtime, (mainly May-June) for spawning. They require high quality, deep, fast-flowing rivers with clean gravel and silty, sandy substrates, for the resulting ammocoete larvae, which take 6-8 years to metamorphose into the adult, to burrow into. Numbers in Cornish rivers vary from year to year but in spring of 2007 in excess of 500 specimens were recorded passing upstream at Gunnislake on the Tamar River. Occasionally the Sea Lamprey may be found attached to various fish
species such as Whiting Merlangius merlangus in the estuaries and open sea around the Cornish coastline. Outside of the UK it is known from most of the Atlantic coastal areas between Norway and the Mediterranean. It is also known from the eastern regions of North America.
Pollution by agricultural wastes (silage, etc.) and changes in land use have affected this species. Also the construction of dams, weirs and the like has interfered with or prevented migration along many traditionally used rivers.
This species is listed under Appendix III of the Bern Convention and under Annex IIa of the EC Habitats Directive. It is also on the UK and OSPAR Lists of Priority Species. Also a number of UK sites that support the Sea Lamprey have been designated as Special Areas of Conservation (SAC). A draft Action Plan has also been produced to guide further conservation efforts. The Life in UK Rivers Project has also helped to highlight the conservation of this species.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.