Stellate Sturgeon, Star Sturgeon
IUCN: СR; Be (III); Bo (II); EUHD (V); CITES (II); RDBBS: VU; RDBUkr: Вразливі
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)).
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.).
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.
Stellate Sturgeon has no commercial value in the basins of the Black and Azov Seas.
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