Toggle navigation. What would you like to search for? The WWF is run at a local level by the following offices Our News The Return of Sturgeons.
Is it Possible at All, or is it too Late Now? Posted on 20 January Shortly before the beginning of the holiday season, Spanish television RTVE launched their new documentary on sturgeons. If proper protection can be put in place this reproductive capability may gradually replenish their populations.
Event On 18 March , Dr. It is based on an objective system for assessing the risk of extinction of a species should no conservation action be taken. Species are assigned to one of eight categories of threat based on whether they meet criteria linked to population trend, population size and structure and geographic range.
It is a rich compendium of information on the threats to the species, their ecological requirements, where they live, and information on conservation actions that can be used to reduce or prevent extinctions.
The Institute transforms real-world policy while pursuing serious science, both of which are essential for ocean health. Thu, 18 Mar Photo: Heather Angel. Photo: Juan Manuel Borrero. Although these two species are the only members in the genus Huso , there are some doubts whether they are sister species Doukakis Bemis and Kynard, ; Bemis, et al.
Beluga sturgeon are considered euryhaline, capable of moving freely between freshwater and estuaries. Species of the order Acipenseriform often enter rivers for migration to other areas or for spawning. Beluga sturgeon spawn at a water temperature of degrees C and they are sensitive to these water conditions during periods of spawning Levin However, other than spawning times, adults are fairly resilient to many environmental factors, particularly considering that they live in some of the most polluted and altered waterways in the world.
Acipenseriformes are primitive actinopterygians that have a fossil record dating back to the Lower Jurassic mya , with an origin perhaps even earlier in the Mesozoic Bemis et al.
Acipenseriformes possess a unique blend of teleost-like character high fecundity small egg size and elasmobranch-like characters cartilaginous endoskeleton, hyostylic jaw suspension. They also possess a heterocercal caudal fin and remnants of ganoid scales; both are uncommon among extant actinopterygians. Sturgeon species are noted by a spindle-shaped body with five rows of bony scutes and a long snout with sensory barbels.
The genus Huso can be distinguished from other sturgeon by possession of branchiostegal membranes that are joined and form a flap Berg The two species in the genus also possess a relatively large crescent shaped mouth Berg Berg gives the following key for distinguishing between Huso congeners:.
Among freshwater fish species, H. Based on Debus's reports on bones excavated from the 14th century, one fifth of all H. Beluga this size today are extremely rare. Bemis et al. The largest beluga ever recorded measured six meters in length and weighed 3, kg Berg , Birstein , Freedman The decreased size of individuals today may reflect the shift to catching younger individuals because of overfishing of older and larger fish, polluted living conditions for beluga in the Caspian and other parts of its range, and the possible loss of large individuals from the gene pool.
Large beluga sturgeon have been targeted by fisherman for centuries. Sexual dimorphism is weakly expressed, and may only be notable in overall size and weight. This dimorphism is particularly notable in gravid females that bear the weight of heavy egg masses Berg , Raspopov Since fisherman or poachers capture nearly all beluga sturgeon before they can die of natural causes, the development of this species is little known.
Length and weight increases much more rapidly earlier in the life history of these fish than during later in ontogeny Raspopov Length and weight can range greatly in a given age class depending on environmental conditions of the sturgeon habitat Raspopov After hatching, downstream migrations of beluga larvae occur between May and June Levin From hatcheries data, it is observed that the weight of beluga after days averages around 2.
By the time they enter the sea they are cm in length. Recently hatched larvae are also purported to move at about 24 km per day during their migration to the sea. By the forth year, beluga may reach a meter in length. In the spring, mature fish enter the rivers to breed, while younger individuals less than 10 years disperse near the Northern Caspian, their distribution based mainly on ecological factors like water temperature and benthic silt Levin Beluga sturgeon mature later than most other acipenseriforms, usually after their 12th year Lelek Raspopov estimated that beluga sturgeon in the Caspian become sexually active every years for females, and every years for males.
Under favorable conditions, a beluga may spawn up to nine times in its lifetime. From in the Volga River which was once the most important spawning habitat of beluga , female spawners have ranged from to cm, and weighed between 48 to kg Levin These are much smaller than recorded sizes for previous years.
Beluga do not spawn every year and females will resorb eggs unless conditions are suitable Artyukhin et al. Sturgeon can take between 6 and 25 years to reach sexual maturity, and females of this species may reproduce only every four to eight years Raspopov Beluga sturgeon are anadromous, migrating to freshwater spawning grounds in rivers from larger seas either the Caspian, Azov or Black.
Some authors have divided beluga populations into Winter or Spring races by the period they choose to spawn Berg These sturgeon typically spawn large numbers of eggs in shallow, gravely sites, and do not provide parental care Bemis et al. The beluga sturgeon is one of the most long-lived of all vertebrate species. Reportedly it may have reached ages over years Ono et al.
Most acipenseriform species mature at a late age normally greater than 10 years. Females mature later than males, normally after 15 years for females and 10 for males Berg Individuals no longer die of natural-age related causes, with most being fished soon after reaching reproductive maturity. The world demand for caviar sturgeon and paddlefish roe is to blame for the shortened lifespan of these fish.
The demand far exceeds the available supply, forcing legal fishers to catch increasingly younger and smaller fish, and providing fuel for a growing black market. Beluga congregate only during spawning times and seem to be a less gregarious species then other Ponto - Caspian sturgeon Levin Damming alters these cues, limiting natural recruitment.
A high rate of tumor development and significant percentage of goandal resorption near the Volgograd dams reveal that sturgeon species, including Huso huso , are often in a state of chronic physical stress caused by habitat degredation Altuf'ev et al Adult beluga sturgeon are mainly piscivores, swimming at middle depths and preying mostly on pelagic fish species.
This is unlike most other sturgeon species, which normally feed on bethic invertebrates while swimming along the bottom. In the Black Sea they feed on species such as flounder Platichthys flesus and other flatfish, gobies Gobiidae , and Black Sea anchovy Engraulis encrasicolus Berg In the Caspian they are reported to feed mainly on the Caspian roach Rutilus rutilus , but also on herring and native gobies.
Little is known about the diet of larval and juvenile H. Unlike other Ponto-Caspian sturgeon species beluga do not congregate, but remain dispersed when not migrating Levin The large size of adults makes predation on them difficult, and a natural predator besides humans is unknown. Many juveniles fall prey to pollution and hydroelectric dams Altuf'ev Most populations are supported solely by hatchery released individuals.
In the 's the number of young beluga's released from the Volga river per year was The survival rate of these individuals was estimated to be 0. The number killed by natural causes or causes other than fishing pressures has not been documented.
Beluga are the largest piscivores in the Pronto-Caspian region. It difficult to determine their role in the past given their endangered status, but in periods where they were quite abundant before they would have been among the top predators in the Ponto-Caspian, playing a similar role as the fish eating seals of the region.
Due to the incredible value of the roe of this species known commercially as beluga caviar - the most expensive food item in the world Birstein et al. This species has become so depleted that its survival is supported entirely or nearly entirely by hatcheries throughout its limited range Secor et al.
Without natural recruitment, population structure, age composition and genetic diversity of the beluga sturgeon have suffered Secor et al. Most beluga sturgeon were historically found in the Caspian Sea. Of the other rivers, the Ural River is the only remaining free-flowing major river feeding the Caspian. It is also the only such river where beluga sturgeon can reproduce naturally, without the benefits of hatcheries Khoderoveskya et al.
Poachers are reportedly removing half of the mature beluga individuals every year. From December to December U.
Fish and Wildlife Services confiscated With an average spawning size of Huso huso individuals being 70 kg Khodorevskya and a gonadosomatic index GSI ranging from.
Because of the unsupportable demand for caviar, beluga sturgeon are being caught at ages closer and closer to sexual maturity. With proper management it is said that it may take between 40 to 45 years for stocks in the Caspian Sea just to return to stable levels Artyukhin The slow maturation of sturgeon tied with low numbers have placed estimates of population recovery for some species at more than a century Secor and Waldman There is some evidence that PCPs and other dangerous chemicals may be retained with the eggs of beluga sturgeon Altuf'ev Small traces of environmental toxins appear in caviar Boyle The levels of some of these chemicals were considered high from samples chosen from some major retailers in the U.
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