Helcom : Salmo salar

Salmo salar (Linnaeus 1758), Atlantic salmon (Salmonidae)

Author: Ronald Fricke, Germany

1. Description of the habitat/autecology of the species

This is an amphihaline species, spending much of its life in freshwater. The young remain in freshwater for 1-6 years, then migrate to the sea and stay there for 1-4 years, before returning to freshwater for their anadromous spawning migration (Atlantic salmons usually return to their river of origin). After spawning on gravel beds far upstream in September to February, some adults return to the sea soon after spawning, some later in spring, but many of them die. Juveniles mainly feed on insects, crustaceans and fish; adults in the Baltic Sea feed mainly on fish (sprat, herring, three-spined stickleback and sandeel), in the western Baltic Sea also on shrimps. Growth is slow in freshwater but very rapid in the sea. Although preferring warmer surface layers in the pelagic this species may also tolerate low water temperatures at larger depths and in the northern rivers. Maximum total length 150 cm (male) or 120 cm (female), maximum weight 46.8 kg, maximum individual age 13 years (Curry-Lindahl, 1985; Fricke, 1987: 65; Froese & Pauly, 2005).

2. Distribution (past and present)

This species is distributed throughout the HELCOM area including adjacent rivers and streams (e.g. IBSFC & HELCOM, 1999; Kaukoranta et al., 2000; Kangur & Wahlberg, 2001). Outside the HELCOM area, the species naturally occurs across the North Atlantic, in the east from Bay of Biscay to northern Norway, and Russia (Verspoor et al., 2005); it has been introduced also into other parts of the world. In the Baltic Sea, salmon migrate from the northern rivers to the Bothnian Sea and Baltic Proper, even to the most southern parts, for feeding, whereas in the Atlantic even longer migrations of adults have been observed.

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

According to the definition in HELCOM (2007), Baltic Sea populations of Salmo salar are of global importance. It still is very important for commercial as well as recreational fishery in the Baltic Sea.

4. Status of threat/decline

The species is threatened throughout its range in the HELCOM area and its autochthonous populations have been significantly declining. The implementation of the IBSFC salmon action plan and national measures in Finland and Sweden have greatly improved the status of the most important Baltic salmon stocks. These measures have resulted in an increase in wild salmon production and 37 salmon rivers have smolt production in the Baltic Sea area. Threats are still existent and some of the wild populations are far from being safe. In the HELCOM area, this species is classified as endangered (EN) according to IUCN criteria and classified as a HELCOM high priority species (HELCOM, 2007). It is listed as critically endangered (CR) by Poland (self sustaining populations do not exist at present in Poland), as endangered (EN) by Denmark (self sustaining populations do not exist at present in Denmark), Estonia, Finland, Germany (self sustaining populations do not exist at present in Germany), and as threatened migrant by Lithuania. It was considered as not threatened by ICES (Anonymous, 2005), and as least concern (LC) by Sweden (but with the landlocked Gullspång stock as endangered EN) (Gärdenfors, 2005; Tjernberg & Svensson, 2007). Salmo salar is also included as a priority species on the OSPAR list (Anonymous, 2004), and on the Annexes II and V of the EU Habitats Directive (at present only in freshwater habitats).

5. Threat/decline factors

Threatened by a variety of factors: it is a target species of fisheries, sometimes caught as by-catch in pelagic and demersal fisheries, competition, parasites and introgression from released hatchery reared salmon (takes place in the river basin by using the home river strain or nearby river strain), eutrophication and silting of the spawning habitat (as clean gravel beds are needed), constuctions of dams and weirs in rivers that hampers the spawning migration, and habitat loss (especially concerning the spawning and nursery habitats). Another threat is the construction of power stations where salmons may die in the cooling water intake. The species is not considered rare, though autochthonous populations may well be; it is highly sensitive to human activities, and a keystone species, especially during spawning migrations.

6. Options for improvement

This species would benefit by a range of measures including conservation and protection of unobstructed salmon rivers, fisheries management, reduction of eutrophication in the spawning rivers, when necessary, ban of gravel extraction in such rivers, construction of fish passes across barriers along the spawning migration route.

7. References

Anonymous 2004. 2004 Initial OSPAR List of Threatened and/or Declining Species and Habitats (References number 2004-06). OSPAR Convention on the Protection of the Marine Environment of the North-east Atlantic, Meeting of the OSPAR Commission (OSPAR), Reykjavik, 28 June-1 July 2004.

Anonymous 2005. Report of the Working Group on Assessment of Baltic Salmon and Trout, Helsinki, Finland, 5-14 April 2005. International Council for the Exploration of the Sea, Advisory Committee on Fishery Management, ICES CM 2005/ACFM: 18.

Curry-Lindahl, K. 1985. Våra Fiskar. Havs- och sötvattensfiskar I Norden och övriga Europa. Norstedt & Söners Förlag, Stockholm. 528 p.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).

Gärdenfors, U. (Ed.). 2005. The 2005 Red List of Swedish Species. Artdatabanken, SLU, Uppsala. 496 p.

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.

IBSFC & HELCOM. 1999. Baltic salmon rivers – status in the late 1990s as reported by the countries in the Baltic Region. The Swedish Environmental Protection Agency & The Swedish National Board of Fisheries, Görteborg, 69 pp.

Kangur, M. & B. Wahlberg (Eds.) 2001. Present and potential production of salmon in Estonian rivers. Swedish Salmon Research Institute, Estonian Marine Institute at the University of Tartu & Department of Environmnetal Engineering, Tallinn Technical University. Estonian Academy Publishers, Tallinn. 108 pp.

Kaukoranta, M., M.-L. Koljonen, J. Koskiniemi, J. Pennanen & J. Tammi. 2000. Atlas of Finnish Fishes. Riistan-, Ja Kalantutkimus. 41 pp.

Tjernberg, M. & M. Svensson. 2007. Swedish Red Data Book of Vertebrates. Artdatabanken, SLU, Uppsala. 549 pp.

Verspoor, E., J.A. Beardmoore, S. Consuegras, C. Garcia de Leaniz, K. Hindar, W.C. Jordan, M.-L. Koljonen, A.A. Mahkrov, T. Paaver, J.A. Sánchez, Ø. Skaala, S. Titov & T.F. Cross. 2005. Population structure in the Atlantic salmon; insights from 40 years of research into genetic protein variation. Journal of Fish Biology 67 (Supplement A): 3-54.