|Scientific Name:||Acipenser sturio|
|Species Authority:||Linnaeus, 1758|
|Taxonomic Notes:||Archaelogical remains suggest that A.sturio colonised the Baltic Sea about 3000 years ago from the North Sea, and vanished from the Baltic Sea about 800 years ago. Climatic changes about 100 years ago (Little Ice Age) might have had an impact indirectly in favouring introgression by hybridization with A. oxyrinchus.|
|Red List Category & Criteria:||Critically Endangered A2cde; B2ab(ii,iii,v) ver 3.1|
|Assessor/s:||Gesner, J., Williot, P., Rochard, E., Freyhof, J. & Kottelat, M.|
|Reviewer/s:||Pourkazemi, M. & Smith, K.|
Once a very wide ranging species from the North and (Eastern) north Atlantic and Mediterranean coast of Europe and the Black Sea (one record from the White Sea in the 1950s), the last remaining population (in the Garonne in France) is still declining. The species last spawned in 1994 in the Garonne, where dams, pollution and river regulation has degraded and destroyed spawning sites. There are also plans to start gravel extraction. The current population size is between 20-750 wild, mature individuals (in the past three years there has been substantial stocking, but these animals will not reproduce until ~2016). Under normal population circumstances, the average reproductive age is suspected to be about 25 years. There has been more than a 90% population decline in the past 75 years based mainly on loss of habitat, along with pollution and exploitation.
This species now remains in just one location, where 27 spawning grounds (less than 10 km²) remain potentially accessible (the major threat to this species is bycatch). As this species continues to be caught as bycatch, the population is still decreasing.
|Range Description:||This species was once known from the North and Baltic Seas, English channel, European coasts of Atlantic, northern Mediterranean west of Rhodos, and western and southern Black Sea. It was occasionally recorded in Algeria, Morocco and Tunisia. The last record from the Rioni (Georgia) was in 1991, although further surveys have failed to find the species (J. Gessner, pers comm.). Today this species is restricted only to the Garonne River (France).|
Regionally extinct:Belgium; Denmark; Germany; Italy; Netherlands; Norway; Portugal; Spain; Tunisia; United Kingdom
|Range Map:||Click here to open the map viewer and explore range.|
The sturgeon was an important commercial fish until the beginning of the 20th century (Debus 2007). The last natural reproduction was in 1994 (previous reproduction in 1988). A population assessment in 2005 estimated 2,000 individuals remain. It is estimated that bycatch took around 200 fish per year (gill net and trawling at sea) (Rochard et al. 1997).
The size of the population today is much smaller (approximately 20-750 native wild adult fish, based on an assessment of the size the cohort before they leave the estuary). There are more individuals from stocking (7,000 in 2007; 80,000 in 2008; and 46,000 in 2009) (Rouault et al. 2008; Rochard 2010). These have not yet bred in the wild and first breeding (from the releases of 1995) is expected by 2014, F1 generation of 2007 and later releases around 2021. The limiting factor is the availability of females which won't reproduce until ~2016 (Rochard, pers. comm).
|Habitat and Ecology:||
Biology: Anadromous (spends at least part of its life in salt water and returns to rivers to breed).
Males reproduce for the first time at 10-12 years, females at 14-18. There are indications for a reproduction at two year intervals for males and 3-4 years for females in April-July. Adults do not eat during migration and spawning. The distance of the spawning migration seems to be positively correlated with water level, and a distance of 1000 km or more may be covered during years of high water. Spent fishes immediately return to the sea (FAO 2009).
Potential spawning grounds have been mapped. Juveniles migrate downstream and are present in upper estuary at one year old. They continue a slow downstream migration and penetrate the sea at 2-3 years. For the next 4-6 years, they leave the sea to enter the lower estuary at summer time where movements and feeding were determined. At sea, this species feeds on a variety of molluscs, crustaceans and small fish. Atlantic population feed benthically.
|Major Threat(s):||Bycatch is the major threat and the extraction of gravel in the Garonne is a potential threat to the species. Dam construction, pollution and river regulation have led to loss and degradation of spawning sites.|
An ongoing in situ conservation programme is in place. Ex-situ conservation is carried out in France and Germany. Bern Convention Action Plans have been developed, while National Action Plans are to come.
Restocking was initiated in 1995 and later in 2007 until 2009. Survival rate for the 1995 stocking is 3-5%; the survival rate for recent releases is unknown. For the first time in 2007, progenies were obtained from farmed specimen (Williot et al. 2009).
There is a fisheries awareness programme co-ordinated between National Fishermen Associations in Atlantic North Sea and WWF.
This species was listed on CITES Appendix II in 1975, and moved to Appendix I in 1983.
|Citation:||Gesner, J., Williot, P., Rochard, E., Freyhof, J. & Kottelat, M. 2010. Acipenser sturio. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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