|Scientific Name:||Acipenser stellatus|
|Species Authority:||Pallas, 1771|
|Red List Category & Criteria:||Critically Endangered A2cde ver 3.1|
|Reviewer/s:||Pourkazemi, M. & Smith, K.|
The species was known from the Caspian, Black and Aegean Seas. It is now extirpated from the Aegean Sea, and in the Black Sea basin the last natural population migrates up the Danube where it is heavily overfished. Only very few spawners remain in the rest of the Black Sea basin. The Caspian populations are under massive pressure from overfishing (including poaching) and loss of spawning sites and the stocks are declining very fast. Almost all migrating spawners are poached below the Volgograd dam. Overfishing will soon cause extinction of the natural populations. In the immediate future, survival can only depend on stocking and effective fisheries management and combating illegal fishing. Based on catch data, and number of individuals migrating into the Volga and Ural rivers it is estimated that the species has undergone a population decline of at least 80% (possibly close to 100%) in the past three generations (minimum estimate of 30 years, possibly up to 40), which is expected to continue. Catch data shows massive declines across the species range with a 98% decline between 1980 and 2007 in the Caspian Sea, and a 72.5% in four years (2002-2005) in Romania (Danube).
|Range Description:||Stellate Sturgeon inhabits in the Caspian, Black and Azov Seas, and rarely in the Aegan Sea. The Volga, Ural, Terek, Sulak, Kura, Don, Danube, Kuban Rivers are the major spawning rivers. The length of the spawning migration route of the Volga to the cascade of dams is up to Rybinsk, in the Ural - to Uralsk, in the Don - to Pavlovsk, in the Kuban - to Armavir. The highest abundance and biomass of natural population remained in the Caspian Sea.
The feeding area in the Caspian Sea of Stellate Sturgeon extended from the shallow water area of the northern part of the sea to the Iranian coast. An intensive migration of Stellate Sturgeon began in spring (March-May) to the shallow water area, in the Northern Caspian where the largest concentrations of fish were observed at the western coast of this part of the sea, as well as in the pre-mouth areas in the eastern part of the Volga River Delta (Belinskii and Igolkinskii Banks (Khodorevskaya et al. 2009)).
Native:Azerbaijan; Bulgaria; Iran, Islamic Republic of; Kazakhstan; Moldova; Romania; Russian Federation; Serbia (Serbia); Turkey; Turkmenistan; Ukraine
|FAO Marine Fishing Areas:||
Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
In the early 1990s it was estimated that nearly 100% of the Sea of Azov population and 30% of the Caspian Sea population were from stocking. Recent estimations are that more than 50% of the Caspian Sea populations are from stocking (Pourkazemi pers. comm.).
Global catches show that in 1992, 2,730 tonnes were caught, falling to a low of 38 tonnes in 2004, and 50 tonnes in 2007 (a decline of over 98% in 15 years). The average catch between 1992-1999 was 1,063 tonnes, and between 2000 and 2007 it was 132 tonnes, a decline of 87% (FAO 2009). The decline in commercial catch for the species is believed to reflect a decline in the species population (CITES 2000).
For the whole Caspian basin, catch peaked in 1977 with 13,700 tonnes; this has shown an almost continuous decline to 305 tonnes in 2003 (most recent data) (over 97% decline in 32 years) (Pikitch et al. 2005). In 2008 the agreed catch quota for A.stellatus for all Caspian Sea countries in 2008 was set at 240 tonnes, including commercial and scientific catch; the quota has not been met (Pourkazemi pers. comm.).
Khodorevskaya et al. (2009) shows that the average numbers of spawners entering the lower Volga per year has fallen from a peak of 230,000 (between 1986-90) to just 50,000 (between 1998-2002), a decline of 78%. It is expected that the decline has continued at a similar rate to the present time (though data does not exist) and will continue. In the Ural the estimated number of migrating individuals per year has also shown a decline, in 1970: 1,100,000; 1979: 1,050,000; 1990: 300,000 migrating individuals (Veschev 1995); 1998: 103,600; 2001: 87,400 (Pikitch et al. 2000). This shows a 92% decline from 1979 to 2001 (also from 1970 to 2001, as migrating individuals per year remained relatively stable between 1970 and 1979).
Distribution of Stellate Sturgeon in the Caspian Sea has declined (based on CPUE distribution data) from the 1970s to 2004 (Khodorevskaya et al. 2009).
In summer, Stellate Sturgeon feed in the warmer waters, forming the densest concentration, more than 0.6 specimens per 10,000 m3 in the western region of the Caspian sea; this is four times higher than was recorded in 1994 (Khodorevskaya et al. 2009). Concentration of all species of sturgeons and in particular, of Stellate Sturgeon, remains high in the area off the island of Ogurchinskii in the southern part of the Caspian Sea off the Turkmenian coast, but its abundance has declined 3.4 times compared to 1991 (Khodorevskaya et al. 2009).
The total population size in the investigated water in 2008 was between 6.7-9.5 million specimens, this has fallen from 83 million in 1988 (Khodorevskaya et al. 2009).
Over recent decades, Stellate Sturgeon abundance in the Caspian Sea has reduced. Evidence of this is shown in the decrease of the average catch per unit effort during trawl surveys between 1978-1999. These showed a three-fold decrease in the northern Caspian Sea, a 2.7-fold decline in the middle part of the Caspian Sea and a six-fold decline off the Dagestan coast (Vlasenko et al. 2003). Decrease of CPUE has been more apparent in the southern part of the sea. The Stellate Sturgeon population has declined from 69.7 million specimens in 1978 to 15.6 million in 2002, and 7.6 million specimens in 2008. Commercial stock decreased by 12 times during this period (Khodorevskaya et al. 2009).
In the Black Sea, in Romania, from 2002-2005 the catches of wild individuals (stocking only started in 2006 in the Danube) dropped from 12.427 tonnes to 3.43 tonnes (72.5% in 4 years); in 2006 commercial catch was stopped (Suciu pers comm.). In Azov Sea, no wild mature females have been caught [for a stocking programme] since 2004 (Chebanov pers. comm.).
|Habitat and Ecology:||
This species is found at sea, coastal and estuarine zones, where it forages on clayey sand bottoms, as well as intensively in middle and upper water layers. It spawns in strong-current habitats in the main course of large and deep rivers, on stone or gravel bottoms. It is also known to spawn on flooded river banks, on sand or sandy clay. Juveniles inhabit shallow riverine habitats during their first summer (Khodorevskaya et al. 2009).
This species is anadromous (spending at least part of its life in salt water and returning to rivers to breed). Caspian fish first mature at 6-7 years for males, and 7-8 years for females, with a generation length not less than 10 years. Females reproduce every 3-4 years and males every 2-3 years in April-September. It spawns only under relatively constant hydrological conditions, as fluctuating hydrological conditions lead to high egg mortality. This species migrates upriver at higher temperatures and therefore later than other sturgeons, with two peaks, in spring and in autumn. Males remain at spawning sites no longer than six weeks and females only 10-12 days. Spent individuals migrate directly back to sea. Yolk-sac larvae are pelagic for 2-3 days and drift with current. Juveniles migrate to sea during their first summer and remain there until maturity. At sea, this species feeds on a wide variety of crustaceans, molluscs and benthic as well as pelagic fish (Khodorevskaya et al. 2009).
The main habitat in the Caspian Sea of the Stellate Sturgeon in the winter is the middle part of the sea (Legeza 1970). In the spring they migrate to the north, with its maximum density being observed off the mid-west coast in shallow water rich in food organisms (Legeza 1970). In late spring they move to the north-west coast. In autumn Stellate Sturgeons begin migrating to the south of the Caspian Sea (earlier than other species), concentrating at the mid-western coast and the south-eastern coast (Legeza 1970).
The spawning migration starts in April. Spawning occurs at temperatures from 9 to 16 °C in the channel and spring flooded spawning grounds at the current speed of 0.8-1.2 m / sec. The greatest number of Stellate Sturgeon migrate to the Ural River (Peseridi et al. 1986, Dovgopol et al. 1992). Stellate Sturgeon stop eating after the beginning of the spawning migration. After spawning, they return downstream into the sea, where they begin actively feeding. The juveniles of Stellate Sturgeon also do not delay in the river and migrate for feeding into the sea.
The reason for Stellate Sturgeon abundance decrease is primarily due to marine fishing and a sharp increase of poaching, seizing the largest and mature fish and nullifying the natural reproduction of sturgeon. 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). Single specimens of Stellate Sturgeon were harvested at the Azerbaijan coast during a trawl survey in 1994; this is most likely due to heavy illegal fishing (large number of poaching gears were observed).
Overfishing has prevented hatcheries catching enough mature individuals to maintain the necessary broodstock (Artyukhin 1997 in CITES 2000), and stocking has severely decreased in the Caspian Sea as the stocking process relies upon wild individuals (unlike other sturgeon species they are difficult to keep mature individuals in ponds, Nikolai pers. comm.). The annual release (over the past 10 years) of sturgeon juveniles from sturgeon hatcheries in Russia amounts to from 3 to 20 million specimens; in Kazakhstan - from 2.5 to 4.1 million specimens; in Azerbaijan - from 2.5 to 6.8 million specimens; in Islamic Republic of Iran - from 0.2 to 1.3 million specimens. This quantity of stocks recruitment of Stellate Sturgeon from industrial sturgeon culture is not enough to supply the population at an optimum level (Khodorevskaya et al. 2009).
Dams have also led to the loss of many spawning grounds. For example the Volgograd dam (built in 1955) led to loss of 40% of spawning sites formally available in the Volga (Khodorevskaya et al. 2009). The species is also considered extirpated from the upper and middle Danube since the building of the Djerdap Dams (Iron Gate Dams). The Don River dam removed 68,000 ha of spawning ground and flow regulation in the Kuban led to the loss of 140,000 ha of spawning grounds.
Pollution is a threat to the species. In 1990, 55,000 sturgeon were found dead on the shore of the Sea of Azov as the result of pollution.
The Allee affect is also a potential threat to the species (Gessner, J. pers. comm.).
Introduced Mnemiopsis (from US) which impacts the species food source (pelagic fishes) has impacted the Black Sea population (impacts now reduced in Black Sea) and is now impacting the Caspian Sea populations.
Introduction of fertilized eggs (from before 1986 and again 2003/4, and it may continue) from the Caspian Sea into the Azov Sea may impact the genetic integrity of Azov Sea population (Chebanov pers. comm.).
Restocking measures are ongoing. However, although aquaculture contributes considerably to the maintenance of the stocks, it cannot compensate for the damage caused to natural reproduction by overfishing (CITES 2000).
It is not fully protected in any range state apart from Moldova. A licence is required for fishing in most countries and private sturgeon fisheries are banned in Iran. This species was listed on CITES Appendix II in 1998.
According to 2007 Caspian Sea Bioresource Commission, 8.1 million fingerlings of A. stellatus were released into Caspian Sea by Khazakstan, Iran and Azerbaijan. Russia released 45 million (all sturgeon species) in 2007, but not specified how many were A. stellatus - but this is not less than 12 million (Ruban pers. comm.).
To preserve the commercial importance of Stellate Sturgeon population it is necessary to protect the recruitment from natural spawning and increase the industrial sturgeon aquaculture. Considering the state of stocks of the Caspian Sea it is necessary for all Caspian Sea states to suspend its harvest for commercial purposes (in Russia, the ban on Stellate Sturgeon commercial harvesting has been introduced since 2005).
Stellate Sturgeon has no commercial value in the basins of the Black and Azov Seas.
|Citation:||Qiwei, W. 2010. Acipenser stellatus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 11 March 2014.|
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