The beluga // or European sturgeon (Huso huso) is a species of anadromous fish in the sturgeon family (Acipenseridae) of order Acipenseriformes. It is found primarily in the Caspian and Black Sea basins, and occasionally in the Adriatic Sea. Heavily fished for the female's valuable roe—known as beluga caviar—the beluga is a huge and late-maturing fish that can live for about 118 years. Going on maximum size, it is the second most massive living species of bony fish behind the ocean sunfish. The species' numbers have been greatly reduced by overfishing and poaching, prompting many governments to enact restrictions on its trade.
The common name for the sturgeon, as for the unrelated beluga whale, is derived from the Russian word белый (beliy), meaning "white", probably referring to the extensive pale colour on the underside in beluga compared to other sturgeons.
The beluga are a large predator which feeds mostly on fish, also rarely consuming waterfowl and seal pups. The beluga will normally pursue prey in the pelagic zone unlike Acipenser sturgeons which remain more so in brackish areas for foraging, thus the beluga will pursue marine fish. However much prey is also taken in brackish areas such as river herrings, the asp and anchovies.
Like most sturgeons, the beluga is anadromous, migrating upstream in rivers to spawn. Males attain sexual maturity at 12–16 years of age, whereas females do so at 16–22 years. In both sexes, they will go to spawn every 4 to 7 years. At one time, beluga sturgeons could migrate up to 1,000 km (620 mi) upriver to spawn but dams in almost every major tributary they utilize has impeded historic spawning routes. The female lays her eggs on gravel from 4 to 40 m (13 to 131 ft) underwater. Upon hatching, the embryo are 11 to 14 mm (0.43 to 0.55 in) long, 10–14 days later when they absorb their yolk sack, the length is 18 to 20 mm (0.71 to 0.79 in). Thereafter, the larvae usually subsist on benthic invertebrates but at as small as 10 cm (3.9 in) in length will switch to a fish-based diet. While swimming back to the ocean, the young sturgeons may cover up to 60 km (37 mi) a day.
The largest accepted record is of a female taken in 1827 in the Volga estuary at 1,571 kg (3,463 lb) and 7.2 m (23 ft 7 in). Another specimen reportedly weighed 1,220 kg (2,690 lb) and measured 6.1 m (20 ft 0 in) in length. Several other records of aged sturgeon exceed 5 m (16 ft 5 in). These great sizes mark the beluga as the largest freshwater fish in the world. A few other species of sturgeon can attain great sizes but none match the maximum sizes known for the beluga, like Chinese, Pacific White, Oceanic European, Atlantic, Baikalian, and Kaluga, the latter a close cousin which can attain a maximum weight of 1,000 kg (2,200 lb).
The beluga may be considered a rival in size to the ocean sunfish among all extant bony fishes, although the sunfish has neither been nearly as heavily fished nor takes as long to attain great size, so more regularly attains massive weights. The beluga may be the second longest extant bony fish as well, after the giant oarfish, which is far more slender in build. The beluga also rivals the great white shark, the Greenland shark, and the tiger shark for the title of largest actively predatory fish, with only the great white easily exceeding the beluga's maximum size. The giant belugas are much larger than the Mekong giant catfish, the arapaima or other sizable rivals for the title of largest freshwater fish. Nevertheless, some scientists still consider the Mekong giant catfish to be the largest true freshwater fish, owing to sturgeons' ability to survive in seawater and that it spends much of its life in brackish environments.
Beluga of such great sizes are very old (continuing to grow throughout life) and have become increasingly rare in recent decades due to the heavy fishing of this species. Today, mature belugas that are caught are generally 142–328 cm (4 ft 8 in–10 ft 9 in) long and weigh 19–264 kg (42–582 lb). The female beluga is typically 20% larger than the male. An exceptionally big beluga caught recently reportedly weighed 960 kg (2,120 lb) and measured 3.4 m (11 ft 2 in).
Beluga caviar is considered a delicacy worldwide. The flesh of the beluga, though, is not particularly renowned but is a hearty white meat similar to that of swordfish. Beluga caviar has long been scarce and expensive and its endangered status has made its caviar more expensive throughout the world.
IUCN classifies the beluga as critically endangered. It is a protected species listed in appendix III of the Bern Convention, and its trade is restricted under CITES appendix II. The Mediterranean population is strongly protected under appendix II of the Bern Convention, prohibiting any intentional killing of these fish.
The United States Fish and Wildlife Service has banned imports of beluga caviar and other beluga products from the Caspian Sea since October 6, 2005, after listing beluga sturgeon under the U.S. Endangered Species Act.
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