Lampetra fluviatilis (Linnaeus 1758), River lamprey (Petromyzontidae)

Author: Ronald Fricke, Germany

1. Description of the habitat/autecology of the species

The river lamprey Lampetra fluviatilis is an anadromously long-distance migrating species. Adults enter freshwater habitats in autumn, winter and even spring, migrate far upstream, and spawn from February to May in gravel areas with adjacent clean sand bottoms. Short after spawning the adult river lampreys die. Larvae bury in sand or clean silt near the spawning site for 3-5 years; after metamorphosis, the juveniles migrate downstream to the sea in spring where they spend another 1-2 years, benthic in shallow and deeper water, mostly on hard bottom or parasitic on larger fishes (mainly cod or herring) (Fricke, 1987: 39; Froese & Pauly, 2005). All lampreys have bucal glands that excrete a substance that prevents blood from clotting (Holcik, 1986). This species reaches a maximum total length of 50 cm (in Finland a maximum of 44 cm), a maximum weight of 150 g, and an individual age of up to 10 years.

2. Distribution (past and present)

The species is distributed throughout HELCOM area including adjacent rivers and streams and the greater lakes in Sweden and Finland.

3. Importance (sub-regional, Baltic Sea-wide, global)

Due to strong populations in the northern Baltic Sea region (best stocks worldwide) and potential genetic differentiation, the Baltic populations are considered as of global importance  according to the definition in HELCOM (2007). In Finland, Sweden and Latvia, river lampreys are traditionally used as human food. The commercial use of river lampreys in the rivers of the Gulf of Bothnia has traditionally been important. Fishery by traps is giving seasonal income for local fishermen and is also an important tourist attraction.

4. Status of threat/decline

This species is considered as threatened and significantly declining mainly in the southwestern and southern Baltic Sea; it is classified as near threatened in the northern Baltic Sea, with only moderate decline in those areas. In the HELCOM area, it is classified as endangered (EN) according to IUCN criteria, and as a HELCOM high priority species (HELCOM, 2007).  The species is listed as critically endangered (CR) in Germany, as vulnerable (VU) in Poland, and as near threatened (NT) in Finland and Sweden. It is also included on Annexes II and V of the EU Habitats Directive.

5. Threat/decline factors

Eutrophication in the spawning habitats (larvae can live only in well oxygenated sand bottoms); construction of weirs and dams in rivers; in some areas fisheries (target species). The species is not considered rare in the HELCOM area. It is sensitive to human activities, including acid waters and daily water level regulations.

6. Options for improvement

Measures for protection of river lamprey should mainly improve the situation along the migration route and at the spawning sites. The construction of new weirs and other migration obstacles in rivers and streams should be avoided; fish passes should be constructed where weirs and other obstacles exist. Eutrophication of potential spawning sites should be reduced. It has been suggested that river lamprey could also benefit from cod and marine mammal protection schemes. However, most Finnish and Swedish river lamprey stocks in the northern Baltic Sea area are viable, and Baltic herring is the main prey species for river lamprey in these areas. Therefore, no special prey protection schemes are needed in Finland and Sweden. Furthermore, the fishing pressure on spawning migrating river lamprey has decreased in many places in Sweden. The reason is that the fishermen mostly are older persons and few younger will carry on.

7. References

Fricke, R. 1987. Deutsche Meeresfische. Bestimmungsbuch.  Hamburg (DJN), 219 pp.

Froese, R. & Pauly, D. (eds) 2005. FishBase. Available in: www.fishbase.org, version (11/2005).

HELCOM 2007. HELCOM Red list of threatened and declining species of lampreys and fish of the Baltic Sea. Baltic Sea Environmental Proceedings, No. 109, 40 pp.  Available in: http://www.helcom.fi/stc/files/Publications/Proceedings/bsep109.pdf

Holcik, J. (Ed) 1986. The freshwater fishes of Europe, Vol. 1, Part I Petromyzontiformes, edited by Juraj Holcik, with contributions by Pier Giorgio Bianco, Martin W. Hardisty, and Claude B. Renaud. AULA-Verlag. Wiesbaden.