The beluga sturgeon is arguably the world’s largest living species of bony fish (Osteichthys)
Damming the Volga
Following the end of World War II, the U.S.S.R. underwent massive post-war industrialization. Under the decree of Premier Joseph Stalin, the Soviet Union constructed the “Great Building Sites of Communism”. This followed the success of Stalin’s “Great Plan for the Transformation of Nature.”
At the crest of this wave of modernization was the Volgograd Hydroelectric Power Plant (VHPP), designed to control the mighty Volga River’s flow into the Caspian Sea. At forty-four feet in height and nearly half a mile in length, the concrete portion of VHPP is the largest dam in all of Europe (“Volga Hydroelectric Station”). It is supported by a two-mile-long, 150-foot-high landfilled dam that offers railway and road crossings of the Volga River. The dam itself generates 12.3 billion kilowatt-hours annually (“Volga Hydroelectric Station”). Most of the power produced by the Station goes to Volgograd (formerly Stalingrad) and Moscow.
The Volga River, like the Volgograd Station, is the largest river in terms of length, discharge, and watershed. Originating in the Valdai Hills in Northwestern Russia, the Volga’s waters flow southward 3700 kilometers into the Caspian. The River’s watershed (see below) covers more than 1.3 million square kilometers of land and serves as an important breeding ground for sturgeon. Astrakhan, located on the Caspian Delta, is the center of the caviar industry (“Volga River”). The Volga is also the primary spawning ground for Caspian beluga sturgeon (“Huso huso”). It is estimated that the dams around the Caspian have impacted 90% of beluga sturgeon breeding grounds (Barannikova et al., 1995).
Traditionally, the reproduction of sturgeons in the Volga was an important source for replenishing their abundance and stock in the Caspian Sea. Prior to regulation of the Volga, the vast water area of its basin provided ample living space for a large stock of sturgeons, which amounted to hundreds of thousands of spawners, allowing them to disperse freely and effectively use a wide variety of spawning grounds. This ensured a high survival rate of the offspring and consistent replenishment of the sturgeon stock in the Volga-Caspian Region (Veshchev 2012).
In 2011, Russian scientists P. Veshchev, G. Guteneva, and R. Mukhanova sought out to determine the effects of the Volgograd Hydroelectric Power Plant on Volga sturgeon. They synthesized data from twenty years of sturgeon censes, and discovered a decline in both the number of spawners and yield of larvae. Between 1991 and 2009, they monitored four sturgeon species—beluga (H. huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus), and sterlet (Acipenser ruthenus)—during spawning season. Veshchev, Guteneva, and Mukhanova performed regular, annual observations on migratory larvae from May to August at eight stations along the southern portion of the Volga. The distances between stations were taken into account to exclude recapture of the same larvae (Veshchev 2012).
Larvae were collected daily with cone nets installed at four to six positions in the surface, middle, and bottom layers of the water column (3 m each). Three nets were assembled on a collapsible pole and submerged for ten minutes at a time. They calculated the number of larvae caught every 24 hours at each station, and then calculated a total from the entire period of downstream migration (Veshchev 2012).
Their analysis revealed that the optimal conditions for sturgeon reproduction are formed in the spring-flooded spawning grounds in the lower reaches of the Volga, when water discharge through the Volgograd HPP dam is between 22,000 and 25,000 cubic meters/second. It also showed the ideal water temperature to be between 9 and 13 degrees Celsius (Veschev 2012).
Veshchev et. al calculated the reproduction rate of those four species of sturgeon during two periods: 1991-2000 (when Volga water levels were high) and 2001-2009 (when levels were lower). They discovered that the reproductive rate was dependent on the maximum height of river waters. When river flow (due to the dam) was reduced between 2001 and 2009, sturgeon spawners could not effectively use spring-flooded spawning grounds. When compared to the high-water period (1991-2000), the low-water period experienced a half-reduction in the number of larvae among all four species studied (Veschev 2012).
Because the health of the Volga’s sturgeon population hinges on the number of breeding adults, these four species suffered. Like other anadromous fish, sexually mature sturgeon are more likely to complete the journey upstream and are thus more likely to lay eggs in their spawning grounds. Veshchev and colleagues’s study gives us numerical evidence for that relationship.
When Volgograd Power Plant reduced water flow by 67% (due to the dam) between 2001 and 2009, only 14,400 spawners reached their breeding grounds. As a result, fishery yield among all four species collapsed to 520 tons. Similar declines have been seen in other rivers flowing into the Caspian, contributing to the rapid collapse of the beluga sturgeon fishery (see below).
But what can be done to save the beluga sturgeon? We must find solutions that fit the fish’s unique biology.
Biology of the Beluga Sturgeon
Today, caviar fishing and the presence of multiple dams along the Volga threaten the survival of sturgeons; including the critically endangered beluga (see below).
During the last 100 million years, beluga sturgeon have evolved life-history characteristics that allow them to thrive in river systems that are large, diverse, and constantly changing (Beamesderfer and Farr, 1997). Delayed maturation, longevity, and high fecundity (ability to produce a high number of offspring) buffer populations from annual variation in environmental conditions (Beamesderfer and Farr, 1997). The largest generally accepted record is of a female taken in 1827 in the Volga estuary at 1,571 kg (3,460 lb) and 7.2 m (24 ft). Several other records of aged sturgeon exceed 5 m (16 ft) (Wood 1983). Beluga of such great sizes are always very old (continuously growing) and have become increasingly rare in recent decades due to the heavy fishing of this species. Most belugas do not reach sexual maturity until 15 years of age (mindfully.org).
Today, belugas that are caught are generally 142–328 cm (4.66–10.76 ft) long and weigh 19–264 kg (42–580 lb). The female beluga sturgeon is typically 20% larger than the male (caspianenvironment.org). This decrease in size has been attributed to the harvest of sexually immature fish that barely meet the requirements for legal catch (Graham 2007).
The female is highly sought-after for its eggs—the world’s most expensive caviar (Young 1999). Considered a delicacy, beluga caviar’s current market price varies from $7,000 to $10,000 per kilogram (2.2 lb) (Schmidt 2003).
Caviar from the rare beluga sturgeon is most prized by connoisseurs, but harvesting the expensive delicacy is threatening the prehistoric fish with extinction. The female beluga sturgeon does not produce roe until it reaches 15 years of age and may live for more than 100 years (Mindfully.org).
As a result of this demand, wild beluga populations have collapsed. Overharvesting and a sharp increase in poaching has led to the largest and most mature belugas being removed from the population and reducing natural reproduction to almost zero (Gesner 2012). Illegal fishing is a huge problem within the sturgeon fisheries, with an estimated 50% of world trade being illegal (USFWS, 1998). Other threats include bycatch from fishing and habitat loss.
Impoundment of rivers has also destroyed most of the beluga’s original spawning grounds around the Caspian Sea. The Volgograd dam has decreased the area of the sturgeon’s spawning grounds by 88-99% since the 1950s. Similarly, 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 (Gesner 2012). Global fisheries statistics show a 93% decline in beluga catch between 1992 (520 tonnes) and 2007 (33 tonnes) (Gesner 2012).
In the face of these numbers, CITES advises that beluga survival can only depend on effective fisheries management and anti-poaching efforts (Gesner 2012). Veshchev et. al believe that spawners and their breeding grounds must be protected. They also recommend that the dam should increase river flow volume to maximize the number of potential spawning grounds (Veshchev 2012). Without intervention, then, the beluga’s extinction is imminent (Gesner 2012).
Barannikova, I.A., I.A. Burtsev, A.D. Vlasenko, A.D. Gershanovich and M.S. Chebanov. 1995. Sturgeon fisheries in Russia.6–11 Sept. 1993. VNIRO Publ., Moscow, Russia Proc. of the Second Int. Symp. on Sturgeon, Moscow–Kostroma–Moscow, Russia.
Beamesderfer, R.C.P. and R.A. Farr. 1997. Alternatives for the protection and restoration of sturgeons and their habitat. Environ. Biol. Fishes. 48:407–417. http://www.springerlink.com/content/k01v3647g8773873/
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Veshchev, GV; Guteneva, GI; Mukhanova, RS; “Efficiency of Natural Reproduction of Sturgeons in the Lower Volga under Current Conditions”. RUSSIAN JOURNAL OF ECOLOGY. Vol 43, Issue 2. Pages 142-147, March 2012. http://www.citeulike.org/article/10518857
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Young, Mark C. (1999). Guinness Book of World Records. p. 94.