LAMPREYS ON THE EDGE
A recent study funded by Scottish Natural Heritage has uncovered the presence of a fish species in the Western Isles, previously unrecorded in the area.
Brook Lamprey is one of three Lamprey species that occur in Scotland, the others being Sea Lamprey and River Lamprey. Fossils of lampreys indicate they date back to before dinosaurs walked the earth.
Unlike most fish, they lack scales, jaws, gill covers and a bony skeleton, and although they resemble eels they have a sucker-like mouth, simple sac-like gills and a skeleton of cartilage.
These three species of Lamprey are all listed on Annex II of the EC Habitats Directive, reflecting concern over widespread declines throughout Europe. Over the last two years, SNH has funded a study to find out exactly where these animals live within Scotland in an effort to assess the current status of each of the three species.
Prior to this work, it was thought that lampreys were absent from the Western and Northern Isles as well as those areas of mainland which lie north of the Great Glen.
Female brook lamprey slightly swollen with eggs
The first part of the study, to pull together existing data on lamprey distribution in Scotland, was carried out by environmental consultancy firm ‘Ecological Research Associates’. This uncovered 2,080 records of lamprey within Scotland from 79 river catchments. Few records existed for rivers and lochs located in the Northern and Western Isles or the North East Highlands.
Over the course of the last year 138 catchments throughout mainland Scotland, Orkney and Shetland and Western Isles were surveyed by fisheries biologists and they confirmed that lamprey were present in most rivers for which previous records existed. They also identified a further 17 catchments with previously unknown populations. Survey data extended the known range of all species, particularly in northern Scotland.
Sea lampreys were the rarest of the three species. Despite this scarcity, sea lampreys are widespread with extant populations in all regions except Orkney and Shetland and, perhaps, the Western Isles, where occasional adults are seen but breeding is unconfirmed. New populations were identified on the north coast of Scotland and in the west Highlands. River lampreys are largely restricted to rivers south of the Great Glen and were not recorded in the Western Isles. Brook lampreys however, were the most common species found throughout Scotland. Although they are now known to be absent from the Northern Isles, a notably isolated population was found in the River Barvas, on the Isle of Lewis. One other population of brook lamprey was found in the River Broadford, on the Isle of Skye. On the Scottish mainland, the distribution of brook lamprey is patchy in the far north of the country and they are absent from the far northwest between Applecross and Loch Erribol.
Despite the fact that lamprey are not widespread throughout the Western Isles, the present of at least two brook lamprey populations, in Lewis and Skye, suggest that these populations represent the extreme north western geographical limit for this species.