|Scientific Name:||Huso huso|
|Species Authority:||(Linnaeus, 1758)|
|Infra-specific Taxa Assessed:|
|Red List Category & Criteria:||Critically Endangered A2bcd ver 3.1|
|Assessor/s:||Gesner, J., Chebanov, M. & Freyhof, J.|
|Reviewer/s:||Pourkazemi, M. & Smith, K.|
The species was historically known from the Caspian, Black, Azov and Adriatic Sea basins. It has been extirpated from the Adriatic (in the early 1970s, Gessner pers. comm.) and Azov Seas due to overfishing and loss of spawning sites due to dams. As the species is very long lived, individuals can still be caught in areas where their spawning sites have been cut off. The last wild population in the Black Sea basin migrates up the Danube river. All other Black Sea stocks are almost extirpated due to overfishing and impoundment of spawning rivers. In the Caspian basin, the last wild population migrates up the River Ural. The Volga population depends on stocking as the construction of Volgograd dam led to the loss of almost all of the species spawning sites in the river. Most of the few recorded females are in their first year of maturation. Based on catch data, and number of recorded spawning individuals it is estimated that the species has seen a wild native population decline of over 90% in the past three generations (a minimum of 60 years) and overfishing for meat and caviar will soon cause global extinction of the remaining natural wild populations. In the immediate future, survival can only depend on stocking and effective fisheries management and combating illegal fishing. Range states are also encouraged to provide protection to the species spawning and feeding grounds.
|Range Description:||This species has been recorded in the basins of the Caspian, Black, Azov, and Adriatic Seas, however its current native wild distribution is restricted to the Black Sea (in the Danube only) and the Caspian Sea (in the Ural only). It is one of the largest anadromous fish in the Caspian Sea, where at least three Beluga populations have been identified by microsatellite technique (Pourkazemi 2008). It does occur in the Azov Sea, and Volga River but these are stocked fish.|
Native:Azerbaijan; Bulgaria; Georgia; Iran, Islamic Republic of; Kazakhstan; Moldova; Romania; Russian Federation; Serbia (Serbia); Turkey
Regionally extinct:Austria; Croatia; Hungary; Slovakia
|Range Map:||Click here to open the map viewer and explore range.|
Global fisheries statistics show that there has been a 93% decline in catch from 1992 (520 tonnes) to 2007 (33 tonnes) (FAO 2009).
The number of Beluga annually entering the Volga dropped from 26,000 (1961-65) to 2,800 (1998-2002), a decline of 89% in 33 years (Khodorevskaya et al. 2009). Only 2,500 migrated up Ural in 2002 (Pikitch et al. 2005).
Currently it is thought that nearly 100% of Beluga in the Volga are hatchery reared, but there is evidence of spawning elsewhere in its distribution (Khodorevskaya et al. 2009). Despite intensive restocking in the Caspian Sea (91% of each generation is estimated to come from hatchery stock), the annual catch in the northern Caspian Sea has drastically fallen. Catches in the Caspian were: 1945-55 average of 1,380 tonnes; 1956-65 average of 1,283 tonnes; 1966-75 average of 1,623 tonnes; 1976-85 average of 849 tonnes; 1986-95 average of 506 tonnes; 1996-2003 (latest data) average of 60.8 tonnes (in Doukakis et al. accepted). This shows a decline of 95%. The official catch statistics support this trend, as they show that the species was abundant in 1938 and then stable to the late 1980s, with the major decline starting from 1990 to the present showing over a 90% decline in the past 60 years (see Khodorevskaya et al. 2009). The agreed Beluga catch quota for all of the Caspian Sea (2007/8 - 28th session of the Commission) was 99.8 tonnes; this quota was not achieved. The proportion of Beluga (to other sturgeon species) in trawl catches of the northern Caspian Sea in all seasons of observations was at an average of 11%. Over the recent years, this percentage has decreased to 8.3%, and the catch of beluga during trawl surveys did not exceed 31 specimens per year (Khodorevskaya et al. 2009).
Spawning numbers for the Volga from 1961-65 was 26,000, whilst in 1996/1997 it was 1,800 (Khodorevskaya et al. 2000), with 2,800 in 1998-2002 (Khodorevskaya et al. 2009).
In the Sea of Azov, between 1979-1981 it is estimated that 551,000 individuals existed (from stocked, and dominated by sub-adult and juveniles); in 1988-1993 there were 25,000 and after 1994 they were only caught sporadically, despite banning of commercial fishing of Beluga in 1986. After 1986 the major threat was from bycatch. Since 1994, 98% of individuals recorded in the Azov Sea have been juvenile. In 2001 the first individuals were produced from captive bred individuals and released (Chebanov and Koziritskaya 2007).
Catches in the Danube have also declined. In the mid-Danube the annual catch was 23 tonnes (average between 1972-76) which dropped to 7.5 tonnes (average between 1985-89), a decline of 67% in around 12 years (CITES 2000). In 2002, 21.3 tonnes were caught in Romania, whilst only 8.4 tonnes were caught in 2005, showing a 60% decline in three years. The percentage of catch quota achieved in Romania was 85% in 2002, 84% in 2003, 46% in 2004, and 34% in 2005. In 2006 the catching of Beluga was banned in the Danube (Paraschiv et al. 2006).
|Habitat and Ecology:||
At sea, this species is found in the pelagic zone, following food organisms. It migrates further upriver to spawn than any other sturgeon; however this migration has now been disrupted due to river regulation (in the Danube drainage up to Morava River). It spawns in strong-current habitats in the main course of large and deep rivers on stone or gravel bottom.
This species is anadromous (spending at least part of its life in salt water and returning to rivers to breed). Males reproduce for the first time at 10-15 years, females at 15-18 years, with an estimated generation length of 20-25 years. This species spawns every 3-4 years in April-June. A complicated pattern of spawning migrations includes one peak in late winter and spring and one in late summer and autumn. In spring, it migrates from the sea before spawning. Individuals migrating in autumn remain in the rivers until the following spring. Spawning occurs at temperature from 6 to 14 °C in the channel and spring flooded spawning grounds at a current speed of 0.8-1.2 m / sec. Spawners the late winter/spring run dominate the spawners in the Volga River (80%), whereas the late summer/autumn run dominates in the Ural River. Yolk-sac larvae are pelagic for 7-8 days and drift with current. Juveniles migrate to sea during their first summer and remain there until maturity.
In the past this species was the largest fish of the Caspian Sea, reaching lengths of more than 5 m and a weight of 1,000 kg. The lifetime of such large specimens, apparently, exceeded 100 years. Currently there are individuals up to 280 cm, weighing up to 650 kg. Average length of females is 240, males is 220 cm, weight respectively is 130 and 65 kg. The maximum age of 53 years was observed in 2003.
Various environmental factors influence the distribution of the species in the Caspian Sea. One factor is water temperature, as mature Beluga prefer water temperatures not exceeding 30°C. They spend the spring and summer mostly in the northern and middle parts of the Caspian Sea and then move southwards to spend the winter in the southern areas, which coincides with highest densities of food organisms. The diet includes roach Rutilus rutilus (L.), common carp (Cyprinus carpio L.), herrings (Clupeidae), kilka (Clupeonella), crayfish (Astacus), gobies (Gobiidae), pike-perch (Sander lucioperca (L.)), birds, sturgeons (Acipenseridae), and even seal (Khodorevskaya et al., 1995). Mature individuals of Beluga are less sensitive to low temperature than the immature, as they feed in the northern part of the Caspian Sea under the ice. With water temperatures decreasing, Belugas reduce the range of depths at which they feed. Immature individuals in spring and autumn prefer the more desalinated sea areas. In summer the highest concentrations occur at the salinity of 3 to 7%. The largest concentrations of Beluga in the northern Caspian occur during the migration of its main prey organisms (herrings, kilka, gobies, roach, etc.).
Overfishing at sea and poaching in estuaries and rivers for meat and caviar is a major threat to the species. Overharvesting and a sharp increase in poaching has led to the largest and most mature specimens being removed from the population and reducing natural reproduction to almost zero (Krassikov and Fedin 1996). In the Ural river current fishing rates are 4 to 5 times sustainable levels (F Max) (Doukakis et al. accepted).
Bycatch is also a threat to the species. The species caviar is very high value (8,000 USD per kilo in 2009).
Impoundment of rivers has destroyed most of the species spawning grounds. The Volgograd dam, built in 1955, has decreased the area of available spawning grounds by 88-100% in the Volga river, similar areas have been reduced in the Terek and Sulak rivers from 132 ha and 202 ha, respectively. The Don river dam removed 68,000 ha of spawning ground and flow regulation in the Kuban river led to the loss of 140,000 ha (CITES 2000).
Due to the longevity of the species there is evidence of pesticide contamination, leading to many problems including reduced reproductive success (Gessner, J. pers comm.).
The Allee effect could also be a threat to the species.
This species was listed on CITES Appendix II in 1998. Restocking programmes are ongoing. However the programmes do not compensate for the loss of natural reproduction and the populations continue to decline (CITES 2000).
The annual number of fingerlings released into the Volga show 0.4 million in 1951; 13.1 million between 1966-70 (average per year); 19.4 million between 1981-85; 11.3 million between 1996-2000; and 3 million between 2001-2005 (Khodorevskaya et al. 2009). The Report of the 28th Session of Caspian Bioresource Commission states that the total fingerling release of beluga in 2008 was 7.02 million from Russia, Iran and Khazakstan.
Some natural reproduction of the species remains in the Volga and Ural Rivers. However, at present the abundance of Beluga is extremely low. Since 2000 in Russia, it has only been caught for the purposes of reproduction (for hatcheries) and science. The protective measures at the feeding grounds are necessary to maintain the population of beluga, as well as the preservation of natural spawning and juveniles breeding at hatcheries.
In the Danube the release of recruitment size (over 15 cm long) from Romania into the Danube has risen from 12,500 in 2006, to 15,130 in 2007 and 20,000 in 2008 (Suciu pers. comm.).
Iran, in work with the World Bank, are increasing the rate of release of Beluga; in 2003, 6,000 individuals (CWT tagged and visible tagged) were released. The size of the released individuals has been increased from 3-5 g to 10-25 g to increase survival rates (Pourali et al. 2003). Hatchery experts (which are state owned) are given financial incentives upon the delivery of individuals ready to be released. Iran has also developed beluga farming to supply meat and caviar production to minimize the impact to the wild population (Pourkazemi pers. comm.).
The species is not fully protected in any range state, though fishing licences are required in most countries and Iran has banned private sturgeon fisheries. Overall however, enforcement measures seem to be lacking. In 1996, fishing in the open sea for the species was banned through an agreement between the countries bordering the Caspian Sea. Artificial spawning grounds have been attempted below Volgograd dam, which has shown some success (Ruban pers. comm.). In the Sea of Azov commercial fishing was banned in 1986.
Gene banks, DNA and tissue cryopreservation exists in Iran and Russia.
Azerbaijan have voluntarily proposed a zero quota for Caviar export for 2009 to CITES.
Range states are also encouraged to provide protection to the species spawning and feeding grounds.
|Citation:||Gesner, J., Chebanov, M. & Freyhof, J. 2010. Huso huso. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 24 May 2013.|
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