|Scientific Name:||Acipenser nudiventris|
|Species Authority:||Lovetsky, 1828|
|Infra-specific Taxa Assessed:|
|Red List Category & Criteria:||Critically Endangered A2cde ver 3.1|
|Assessor/s:||Gesner, J., Freyhof, J. & Kottelat, M.|
|Reviewer/s:||Pourkazemi, M. & Smith, K.|
The species is known from the Black, Aral and Caspian seas. However, it is extirpated from the Aral Sea, nearly extirpated in the Black Sea basin and there are only occasional records from lower Volga. The only remaining population occurs in the rivers Ural (Russia, Kazakhstan) and possibly the Rioni (Georgia - last recorded 1997 through bycatch; there are no recent surveys), and possibly the Safid Rud (seven individuals recorded in 2002) in Iran. In Europe, it is thought that few individuals exist in the Danube - indeed it is considered possibly extinct. Even though there is no catch data it is suspected that the species has undergone a population decline of more than 90% in the past three generations (estimated at 45 years) which is expected to continue. It is believed the species is on the verge of global extinction. The largest population is in Lake Balkash (introduced for commercial reasons) which is outside the species natural range.
|Range Description:||This species has been recorded from the Black, Azov, Caspian and Aral Seas, and some rivers (Danube up to Bratislava, Volga up to Kazan, Ural up to Chkalov, Don and Kuban, Rioni). It was introduced to Lake Balkhash (Kazakhstan), to the upper Illi River in China, and to River Syr-Darya (Aral basin) in the 1960s.|
Native:Azerbaijan; Georgia; Hungary; Iran, Islamic Republic of; Kazakhstan; Russian Federation; Serbia (Serbia); Turkey
|FAO Marine Fishing Areas:||
Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
It is currently known from the Caspian Sea, where it ascends only the Ural river (where it naturally reproduces) and the Sefid Rud River (where there is no natural reproduction), where 5 fish were caught in 2002 (Parandavar et al. 2009). In the Black Sea, it ascends the Rioni (last recorded 1997 through bycatch (Zarkua pers. comm.)). In the Danube it was last recorded in 2003 in Serbia at Apatin (released alive) and in 2005 in Mura in Hungary (killed); both these caught fish were males (Simonovic et al. 2003; Streibel pers. comm.). In Romania, according to a fisherman survey carried out between 1996-2001, 15 individuals were caught by Romanian fishermen (last scientifically recorded in 1950s) (Suciu et al. 2009) .
Little catch data is available. It has not been caught in Ukraine for the past 30 years. In Kasakhstan 12 tonnes were caught in 1990, 26 tonnes in 1999; in Iran 1.9 tonnes were caught in 1990, 21 tonnes in 1999 (CITES Doc. AC.16.7.2), and 1 ton in 2005/6, with 0.5-1% of total sturgeon catch in Iran belonging to this species (in past 20 years) (Pourkazemi pers. comm.). According to Caspian Aquatic Bioresource Commission (CAB), since 2001/2 export quota for caviar is zero for all Caspian range states.
|Habitat and Ecology:||
Habitat : At sea, close to shores and estuaries. In freshwater, deep stretches of large rivers. Juveniles in shallow riverine habitats. This species spawns in strong-current habitats in main courses of large and deep rivers on stone or gravel bottom.
Biology: Anadromous (spending at least part of its life in salt water and returning to rivers to breed), with some non-migratory freshwater populations. Males reproduce for the first time at 6-15 years, females at 12-22, with an average generation length of 15 years (but in the Danube, the average population age has now increased and in the Caspian Sea, the average population age is decreasing because of overharvesting). In most drainages, there are two migration runs, in spring and autumn. Individuals migrating in autumn remain in the river until the following spring to spawn. Females reproduce every 2-3 and males every 1-2 years in March-May and at temperatures above 10°C. Most juveniles move to sea in their first summer and remain there until maturity. Some individuals remain in freshwater for a longer period. Feeds on a wide variety of benthic fishes, molluscs and crustaceans.
This species has the highest relative fecundity for any sturgeon species (Chebanov pers. comm.).
Over harvesting, bycatch and illegal fishing (poaching) along with dams, water abstraction and drought has led to the loss of spawning habitats/ground and has caused massive population declines. In the Caspian Sea and Sea of Azov the illegal sturgeon catch for all species was evaluated to be 6 to 10 times the legal catch (CITES Doc. AC.16.7.2).
Transfers of A. stellatus from the Caspian Sea, carrying a nematode parasite, were introduced to the Aral sea in the late 1960s and along with increasing salinity, helped cause the extirpation of A. nudiventris in the Aral sea within a few years (Gessner, J. pers. comm.).
The Allee affect is also a potential threat to the species (Gessner, J. pers comm.).
Hybridisation between this species and all sturgeons and especially A. stellatus occurs in freshwater naturally (Chebanov pers. Com.).
|Conservation Actions:||There is a zero quota of exporting of Caviar (CAB) but there is still a catch for domestic use. Iran and Russia have established gene bank conservation for this species for both live specimens and cryopreservation with DNA and tissue samples. The 2004 progeny have been produced from captive bred individuals - juveniles were released into the Don and Kuban rivers - and there are between 15 and 20 'farms' in Russia (Chebenov pers comm.). In Iran 80,000-1 million fingerlings (3-5 g each) (from ranched individuals) are released annually to the Caspian Sea (Pourkazemi pers comm.). This species was listed on CITES Appendix II in 1998.|
|Citation:||Gesner, J., Freyhof, J. & Kottelat, M. 2010. Acipenser nudiventris. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 16 April 2014.|
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