Acipenser oxyrinchus (Mitchill 1815), Atlantic sturgeon (Acipenseridae)

Author: Ronald Fricke, Germany

1. Description of the habitat/autecology of the species

Acipenser oxyrinchus (synonyms: A. oxyrhinchus, A. oxyrhynchus) is living demersally above sand and mud bottoms, in the ocean from inshore coastal waters down to 50 m depth. The species is usually living solitarily. As an anadromously migrating species, it enters rivers for reproduction, and spawns at depths of 2-10 m over stony bottoms. Females produce 800,000 to 2,400,000 sticky eggs which adhere to the stones; larvae hatching after 1 week. After hatching, juveniles may remain in fresh or brackish water for 3-5 years, then migrate slowly into the sea where they spend at least 8 years (often up to 30 years) before they mature and start their spawning migration again; they spawn every 3-4 years. Atlantic sturgeons feed on crustaceans, molluscs, polychaete worms, and small fishes (Gessner & Ritterhoff, 2004; Froese & Pauly, 2005). Maximum total length 403 cm (male) or 430 cm (female); maximum total weight 368 kg; maximum individual age 60 years.

2. Distribution (past and present)

Historically distributed throughout the the HELCOM area including adjacent rivers. Extinct at present. Outside the HELCOM area, it is distributed along the Atlantic coast of eastern North America.

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

This species is considered as of local importance (historically) in the HELCOM area.

4. Status of threat/decline

This species' populations have been severely declining to extinction throughout its distribution range in HELCOM area. Aong the Atlantic coast of eastern North America, more or less stable populations of the species belonging to several genetically distinct entities are extant. Former Baltic Sea populations have had a similar genetic structure as the northernmost population of the species which is extant in St. Lawrence and St. John rivers/Canada (Ludewig et al., 2002).

In the HELCOM area, this species is classified as extinct (EX) according to IUCN criteria, and as a HELCOM high priority species (HELCOM, 2007). It was listed as extinct (in part under the name A. sturio L, 1758) by Denmark, Estonia, Germany, Finland, Latvia, Lithuania, Poland and Sweden, and as endangered (EN) by Russia; the latter classification is considered erroneous by Fricke (MS) and based on confusion with other, introduced, sturgeon species. The species is included in the Annex II of the EU Habitats Directive as a priority species, under the name A. sturio. For eastern North America, the species is listed as near threatened (NT) by IUCN (Baillie et al., 2004). It is also listed on CITES (annex II).

5. Threat/decline factors

Threatened by a variety of factors: it is a target species of (historical) fisheries, it is caught as by-catch in demersal and river fisheries, eutrophication degrades its spawning sites (as the species spawns on clean gravel beds), and construction in rivers (dams and weirs) barrier spawning migration and cause too strong water velocity (affecting spawning migration of this slow-moving fish). The species used to be common, but is now extinct, and highly sensitive to human activities.

6. Options for improvement

This species is extirpated in the Baltic region and the possibilities for spontaneous reintroduction are very low. Therefore hatchery rearing and stocking are needed. However, before this action is taken, it is necessary to investigate the reasons for the extinction and to survey the natural conditions for reintroduction. Conservation schemes should include scientifically advised restocking programmes into suitable rivers over an extended period of time (using as stocking material specimens out of the northernmost population of the North American stocks, from around St.-Lawrence and St.-John rivers, Canada), as well as fisheries restrictions, freshwater and marine protected areas, measures to reduce eutrophication of the spawning rivers, and construction of special fish passes or sturgeon elevators around weirs.

7. References

Baillie J.E.M., Hilton-Taylor C. & Stuart S.N. 2004. 2004 IUCN red list of threatened species. A global species assessment. Gland & Cambridge (IUCN).

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

Gessner J. & Ritterhoff J. (eds.) 2004. Species differentiation and üpopulation identification in the  sturgeons Acipenser sturio L. and Acipenser oxyrhinchus. BfN-Skripten, 101, 2004.

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

Ludewig A., Debus L., Lieckfield D., Wirgin I., Benecke N., Jenneckens I., Williot P., Waldman J.R. and Pitra C. 2002. When the american sea sturgeon swam east. Nature 419, 447.