Download Endangered species of fish

Endangered species of fish
(Grayling; Beluga)
Dasha O., UKRAINE
Grayling (genus)
Thymallus is a genus of freshwater fish in the salmon family (family Salmonidae) of order
Salmoniformes; it is the only genus of subfamily Thymallinae. The type species is T. thymallus,
the grayling. The genus's five distinct species are generically called graylings, but without
qualification this also refers specifically to T. thymallus.
The fishes of this genus are native to the northern parts of the Palearctic and Nearctic ecozones,
ranging from the United Kingdom and northern Europe across Eurasia to Siberia, as well as
northern North America. T. thymallus, the grayling proper, is widespread in Europe, and T.
arcticus arcticus, the Arctic grayling, is widespread throughout Eurasia east of the Ural
Mountains and in the Nearctic. The other species and T. arcticus subspecies have more
localized ranges.
The Thymallus species are distinguished from other members of the salmon family by their larger
scales, their small mouths with teeth on the maxillary bone, and most striking of all, their showy, saillike dorsal fins. This fin is longer in males and highly colourful, with spots of red, orange, purple or
green. The body is also colourful; the dorsal surface is a dark purplish to bluish black or gray, grading to
dark blue or silver gray on the flanks and gray or white on the belly. The body is further decorated with
a smattering of small dark spots; these are much more numerous in juveniles. The largest of the
graylings in terms of length is the Arctic grayling (T. arcticus arcticus) at a maximum length of 76 cm (30
in) and a maximum weight of 3.8 kg (8.4 lb); other subspecies of T. arcticus are typically half this length
or less. The grayling proper, T. thymallus, while somewhat shorter - 60 cm (24 in) - may weigh
significantly more, 6.7 kg (15 lb). The fishes of this genus may live for 18 years or more.
As they are highly sensitive to changes in water quality, Thymallus fishes may be considered indicator
species; T. arcticus arcticus has largely disappeared from the Great Lakes Basin. These fishes require
cool, well-oxygenated water, preferably with a swift current; they are found in large sandy- or gravellybottomed rivers and lakes, but T. thymallus may occasionally be found in brackish conditions.
Generally omnivorous, they feed primarily on crustaceans, insects, and zooplankton.
The grayling species, typically for salmonids, spawn in rivers and do not guard their brood,
although they do conceal their eggs in silt. The spawning behavior of the Arctic grayling may be
typical for the Thymallus species.
Arctic grayling (T. arcticus arcticus) leaping for a fly fisherman's bait.
Alaskan Arctic Grayling
Due to their agreeable taste and attractive form, the grayling species are valued as food and
game fishes, and they are occasionally seen in public aquaria. The most economically important
of these fishes, for which fisheries and aquaculture operations exist, are the grayling proper (T.
thymallus) and the Arctic grayling (T. arcticus arcticus)
Beluga (sturgeon)
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, slow-growing and late-maturing fish that
can live for 118 years.[2] The species' numbers have been greatly reduced by overfishing and
poaching, prompting many governments to enact restrictions on its trade. The most similar
to the Huso huso Beluga is the Huso dauricus Kaluga, also referred to as the "River Beluga".
The common name for the sturgeon, as for the unrelated beluga whale, is derived from the
Russian word белый (belyy), meaning "white".
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Behaviour
The beluga is a large predator which feeds on other fish.
As do many sturgeons, the beluga travels upstream in rivers to spawn. Accordingly, sturgeons are
sometimes likened to sea fish; however most scientists consider them to be river fish.
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Caviar
Beluga caviar is considered a delicacy worldwide. The meat of the beluga, on the other hand, is
not particularly renowned. Beluga caviar has long been scarce and expensive, but the
endangered status of the fish has made its caviar more expensive than before.
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Status
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.
The United States banned import of beluga caviar in 2006 after listing beluga sturgeon under the
U.S. Endangered Species Act.
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Size
The largest generally accepted record is of a female taken in 1827 in the Volga estuary at 1,476 kg
(3,250 lb) and 7.2 m (24 ft),[3] making the beluga the largest freshwater fish in the world;
larger even than the Mekong giant catfish or the pirarucu. Nevertheless, some scientists still
consider the Mekong giant catfish to be the largest freshwater fish, owing to sturgeons'
ability to survive in seawater.
Beluga of such great sizes are always very old (continuing to grow throughout life) and have
become increasingly rare in recent decades due to the heavy fishing of this species. 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 is typically 20% larger than the male.