|Scientific Name:||Acipenser gueldenstaedtii|
|Species Authority:||Brandt & Ratzeburg, 1833|
|Red List Category & Criteria:||Critically Endangered A2bcde ver 3.1|
|Assessor/s:||Gesner, J., Freyhof, J. & Kottelat, M.|
|Reviewer/s:||Pourkazemi, M. & Smith, K.|
The species is now very rare in the Black Sea basin where almost all of the species' spawning sites have been lost due to dam construction, except in the lower Danube river where some spawning still exists (see Juvenile Spawning Index) but individuals are rare. The Caspian basin has lost 70% of spawning grounds since the 1950s mainly due to hydroelectric power stations; flow regulation of the Kuban has led to the loss of 140,000 ha and damming of the river Don removed 68,000 ha spawning ground (CITES 2000).
The last natural population still migrates up the Danube and the Rioni (last recorded in Rioni in 1999), where the sturgeons are heavily overfished and poached. The Caspian populations are also under massive pressure from overfishing and loss of spawning habitats. Almost all migrating spawners are poached below the Volgograd dam. The Ural river still has spawning individuals.
It is estimated that the species' wild native population has undergone a massive population decline of over 90% in the past three generations (estimated at 45 years). This is based on the 88.5% decline in global catches of the species in just 15 years despite large levels of stocking (average global catch from 1992-1999 was 1,531.75 tonnes; from 2000-2007 it was 175.37 tonnes), the 92.5% decline in estimated spawning stock biomass in the Volga from 1961-65 to 1998-2000, the 88% decline in the average number of spawners entering the lower Volga from the 1962-75 average to the 1992-2002 average, and the decline in the Juvenile Production Index from Romanian Danube.
This decline is predicted to continue as illegal fishing at sea, and in rivers, for caviar will soon result in the extinction of the remaining natural wild population. In the immediate future, survival can only depend on stocking.
|Range Description:||This species is known from the Caspian, Black and Azov Sea basins. Aquaculture has resulted in intentional and accidental introductions throughout Europe.
It is currently only known from the Caspian Sea, where it spawns in the rivers Ural and Volga, and the Black Sea where spawning occurs in the lower Danube and Rioni rivers (last recorded in the Rioni in 1999 (Kolman & Zarkua 2002)). There is no native spawning population remaining in the Sea of Azov, only introduced (stocked) individuals. The species reproduction within the Kura is debated (Vecsei 2001).
Native:Azerbaijan; Bulgaria; Georgia; Iran, Islamic Republic of; Kazakhstan; Moldova; Romania; Russian Federation; Serbia (Serbia); Turkey; Turkmenistan; Ukraine
Regionally extinct:Austria; Croatia; Hungary
|FAO Marine Fishing Areas:||
Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
The species wild native population has undergone major decline which is currently occurring. But due to the large levels of stocking (particularly Russia and Iran) the exact levels are unknown. According to CITES (2000) Russia released 25 million fingerlings into the Vologa between 1979-80, 35 million between 1981-85, 40.8 million between 1986-90, 42 million between 1991-95 and 28 million 1996-98; Iran released 300,000 fingerlings in 1994 which has risen nearly every year to 960,000 in 1999.
Despite this level of stocking, fisheries catches have fallen, particularly from the early 1990s in the Caspian. According to FAO fisheries statistics (FAO 2009) global catches fell from 4,250 tonnes in 1992 (first available catch data) to 67 tonnes in 2007 (last available catch data), a decline of 98% in 15 years. The average catch from 1992-1999 (8 year period) was 1,531.75 tonnes, whereas the average catch from 2000-2007 (8 year period) was 175.37 tonnes, a decline of 88.5%.
Data from the Caspian Sea (Khodorevskaya et al. 2009) shows similar declines: catches were between 6,000 and 9,000 tonnes per year in the 1960s to a peak of around 14,500 tonnes in the late 1970s early 1980s to less than 1,000 per year from 2000 to 2008. The estimated spawning stock biomass in the Volga has also drastically declined, from 13,200 tonnes (1961-65) and 22,200 tonnes (1966-70) to 1,000 tonnes (1996-97) and 1,000 tonnes (1998-2002). Average number of spawners (1,000 individuals) passing fishery zones to the spawning grounds in the lower Volga (per year) has declined by 88% from the 1962-75 average to the 1992-2002 average.
Romanian catch data (Danube) shows that in 2002, 3,726 kg was caught; in 2003, 1,499 kg; in 2004, 440 kg; and in 2005, 37 kg, showing a 99% decline in just four years (Paraschiv et al. 2006). A Juvenile Production Index (evidence of breeding) for the Danube (Romania) also shows a decline: CPUE was just over 0.7 in 2000, < 0.2 in 2001, 0.3 in 2002, 0 in 2003, < 0.1 in 2004, 0.1 in 2005, 0 in 2006, < 0.05 in 2007 and 0 in 2008. (CPUE = number of Young of the Year - number of < 1 year olds caught - from natural recruitment captured in one netting (Suciu 2008, pers. comm.; Paraschiv et al. 2006; Knight et al. 2010).
|Habitat and Ecology:||
Habitat: At sea, shallow coastal and estuarine zones. In freshwaters, in deep parts of large rivers with moderate to swift current. Spawns in strong current (1-1.5 m/s) in large and deep rivers on stone or gravel bottom.
Biology: Anadromous and freshwater populations (freshwater populations existed in the Danube and Volga - both are now extinct). A complicated pattern of spawning migrations includes spring and autumn runs. Individuals migrating in spring enter freshwater just before spawning; they tend to spawn in lower reaches of rivers (320-650 km in the unregulated Ural). Individuals migrating in autumn overwinter in rivers and spawn the following spring further upstream (900-1200 km in the Ural).
Males reproduce for the first time at 8-13 years, females at 10-16. Generation length (average age of parents of current cohort) is estimated to be 15 years under natural circumstances, but due to the impacts this species is facing the generation length ranges from between 12 years in the Caspian Sea to over 20 in the Danube. Females reproduce every 4-6 years and males every 2-3 years in April-June, when the temperature rises above 10°C. Larvae drift on currents; juveniles then move towards shallower habitats, before migrating to the sea during their first summer. They remain at sea until maturity. The Russian Sturgeon feeds on a wide variety of benthic molluscs, crustaceans and small fish.
Most spawning sites have been lost due to dam construction. The Caspian basin lost 70% of spawning grounds since the 1950s, mainly due to the construction of hydroelectric power stations; the Ural is now the only river in the basin with unregulated flow. Flow regulation of the Kuban River has led to the loss of 140,000 ha, and damming of the river Don has removed 68,000 ha spawning ground. For example, in the Yugoslavian section of the Danube, the annual catch dropped from 14,636 kg in 1983 to 1,636 kg in 1985 (a decline of just under 90%), this is believed to be due to the construction of the Djerdap (Irongate) II dam which was constructed in 1984, leaving no accessible spawning grounds for the species in the upstream reaches and in former Yugoslavia (CITES 2000).
Poaching and illegal fishing, which appears to be increasing, is also a threat to the species. Enforcement of legislation regulating the fishery for the species appear to be lacking. 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 2000). Bycatch is also a threat to the species (in both marine and freshwater).
High levels of pollution (from oil and industrial waste), in both the Black and Caspian Sea basins have altered hormonal balance, and increased the number of hermaphroditic fish. Pollution levels are now decreasing since the break up of the Soviet Union (Levin, 1977 in CITES 2000). In 1990, 55,000 sturgeon were found dead on the shore of the Sea of Azov as the result of pollution.
Genetic pollution is also a potential threat as stocks are moved to different locations (e.g. Caspian stocks moved to Sea of Azov).
The Allee affect is also a potential threat to the species.
Restocking measures are ongoing, however stocks are continuing to decline. In the early 1990s, between 30-55% of the Caspian stock reportedly originated from hatcheries (Barannikova 1995 in CITES 2000, Khodorevskaya et al. 2000). In Russia, between 1991 and 1998, 70 million fry of A. gueldenstaedtii were released in the Volga river and just over 32 million fry into the Sea of Azov.
The species is not fully protected in any range state, though licenses are required in most countries and Iran has banned private sturgeon fisheries. Overall, however, enforcement measures seem to be lacking. Fish lifts and artificial spawning grounds have been introduced to parts of the Caspian region (CITES 2000) without much success. This species was listed on CITES Appendix II in 1998.
Gene bank of live specimens and cryopreservation is ongoing in Russia and Iran.
|Citation:||Gesner, J., Freyhof, J. & Kottelat, M. 2010. Acipenser gueldenstaedtii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 December 2013.|
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