National Lamprey Survey of Scotland (2003-2005)
141 catchments throughout mainland Scotland, Orkney and Shetland and Western Isles were surveyed by electrofishing for larvae, confirming lamprey presence in most rivers with previous records and identifying 17 catchments with previously unknown populations, extending the known range of all species.
Lampreys were present in 65 of the 141 catchments and at 342 of 710 survey sites.
Lampreys were absent from all survey sites on Orkney and Shetland and from those areas of west Highlands north of Loch Carron. Distribution was patchy in east Sutherland, Caithness and Easter Ross, but several previously unrecorded populations were identified. Lampreys were present in most rivers south of the Great Glen.
Sea lamprey were present in 13 catchments, river lampreys in 20 and brook lampreys in 51. Unidentified Lampetra species were present in a further 13.
Sea lampreys were the rarest species in both records and survey. They have been recorded in 35 rivers, although their continuing presence in some of these is uncertain. Although scarce, sea lampreys are widespread with extant populations in all regions excepting Orkney and Shetland and, perhaps, Western Isles where occasional adults are seen but breeding is unconfirmed.
The survey identified several catchments with previously unrecorded river lamprey populations, particularly in south Argyll. River lampreys have now been recorded in 42 mainland rivers. There are no records from any of the islands. River lampreys are largely restricted to rivers south of the Great Glen.
Brook lampreys were the most common species in both records and survey. Their presence has now been confirmed in all regions excepting Orkney and Shetland. Single, isolated populations were present on Lewis, Skye and Islay. The species is common south of the Great Glen. Distribution is patchy in the far north of Scotland and they are absent from the far north-west.