Lamprey (Petromyzontiformes)

Scotland is home to three lamprey species: sea lamprey (Petromyzon marinus), European river lamprey (Lampetra fluviatilis), and European brook lamprey (Lampetra planeri). A study of 62 river catchments found the European brook lamprey to be the most widespread species in Scotland (Hume, 2017). 

Brook lamprey, exclusively freshwater dwellers, are the smallest at 15–19 cm. River lampreys grow larger, from 30 to 50 cm, and migrate between freshwater and coastal feeding grounds to spawn. The largest and only parasitic species, the sea lamprey, can reach up to 1 meter in length and also utilises both fresh and saltwater habitats (NatureScot, 2023). 

Lampreys have a unique anatomy, classified within the ancient vertebrate group Agnatha, or "jawless fish.” Unlike most vertebrates, their skeletons are made of strong, flexible cartilage instead of bone (NatureScot, 2023). Their eel-like body is long and cylindrical, featuring a dorsal fin near the tail and seven-gill openings on each side, behind the eyes (Canal and River Trust, 2020).

Lifecycle
Lampreys construct nests, called "redds," where they deposit their eggs. Brook and river lampreys typically spawn in large groups of up to 50 individuals, while sea lampreys spawn in much smaller groups. After hatching the larvae, known as ammocoetes, are carried downstream until they find suitable habitats with soft, sandy sediment in well-oxygenated water (NatureScot, 2023). Once settled, the larvae burrow into the sediment and feed on tiny particles, such as algae and bacteria, filtering them from the water. The larval stage lasts between three to seven years, depending on the species (Woodland Trust, n.d.). During this time, they develop into pre-adults and prepare for the next stage of their life cycle (NatureScot, 2023). 

As they mature, lampreys follow one of two distinct developmental pathways. Parasitic species, like the sea lampreys, undergo significant changes to support their feeding habits. Their mouths transform into sucker-like discs armed with sharp teeth and a rasping tongue, while their salivary glands produce anticoagulants to allow for blood feeding. Their digestive systems also adapt to digest blood and tissue of their host (Lennon, 1953). In contrast, nonparasitic species (e.g. European river and brook lamprey) do not undergo these changes and actually stop feeding upon reaching adulthood (NatureScot, 2023).

Population Status & Trends
In recent years the numbers of lamprey in Scotland and the rest of the UK have steadily declined, to the point in which all species are now classed as rare and protected (Natural Resources Wales, 2024). One of the biggest issues lamprey face are migration barriers, such as weirs and other man-made structures, which obstruct lamprey from reaching the suitable breeding grounds upstream in freshwater rivers. Another problem facing the species is pollution, primarily driven by chemical runoff from farmland and other infrastructure. Paired with the destruction of habitat, this combination of threats makes it hard for lampreys to persist. Fortunately, lampreys are not at risk from commercial fishing in Scotland due to their lack of commercial value, although this is not the case in some parts of Europe

Conservation Status
European Brook Lamprey (Lampetra planeri) is classified as Near Threatened (Ford, 2024a). 

Sea Lamprey (Petromyzon marinus) is classified as Least Concern, despite being listed as Threatened or Near Threatened on the national Red Lists of most European countries (OSPAR, 2022; Ford, 2024c). 

European River Lamprey (Lampetra fluviatilis) is classified as Near Threatened (Ford, 2024b).

Future of Lamprey in Scotland
In Scotland, lamprey species are safeguarded under Schedule 3 of the Conservation (Natural Habitats, &c.) Regulations 1994 (NatureScot, 2023). This simply means that it is an offence to use certain methods to catch or take these fish from freshwater habitats. In addition to this, lampreys are considered a priority species under the UK Post-2010 Biodiversity Framework (Wildlife Trusts, n.d.). In order to protect the species further into the future, initiatives must be created to preserve their habitat, reduce pollution in our waterways and remove man-made barriers blocking essential migratory routes.