Atlantic Sturgeon, Common Sturgeon, Baltic Sturgeon
IUCN: СR; Be (II); Bo (I); EUHD (V); CITES (I); CarpRL: EX; RDBUkr: Зниклі
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.
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).
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).
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.
- Соколов Н.Ю. Каталог колекції круглоротих і риб Державного природознавчого музею НАН України // Наукові записки Державного природознавчого музею. – Львів, 2004. – Т.19. – С. 15-28.