name = Sturgeon
image_width = 250px
("Acipenser oxyrinchus oxyrinchus")
phylum = Chordata
familia = Acipenseridae
subdivision_ranks = Subfamilies
Acipenserinae ScaphirhynchinaeSee text for genera and species.
Sturgeon is the
common nameused for some 26 species of fish in the family Acipenseridae, including the genera " Acipenser", " Huso", " Scaphirhynchus" and " Pseudoscaphirhynchus". The term includes over 20 species commonly referred to as sturgeon and several closely related species that have distinct common names, notably sterlet, kaluga and beluga. Collectively, the family is also known as the True Sturgeons. Sturgeon is sometimes used more exclusively to refer to the species in the two best-known genera; "Acipenser" and "Huso".
One of the oldest families of
bony fishin existence, they are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasiaand North America. They are distinctive for their elongated bodies, lack of scales, and occasional great size: Sturgeons ranging from 7–12 feet (2-3½ m) in length are common, and some species grow up to convert|18|ft|m|1. Most sturgeons are anadromousbottom-feeders, spawning upstream and feeding in river deltasand estuaries. While some are entirely freshwater, very few venture into the open ocean beyond near coastalareas.
Several species of sturgeons are harvested for their
roe, which is made into caviar- a luxury goodwhich makes some sturgeons pound for pound the most valuable of all harvested fish. Because they are slow-growing and mature very late in life, they are particularly vulnerable to exploitation and to other threats, including pollutionand habitat fragmentation. Most species of sturgeons are currently considered either vulnerable, endangeredor critically endangered.
Sturgeon and related
paddlefishfirst appear in the fossil record approximately 200 million years ago, making them among the most ancient of teleostfish. In that time they have undergone remarkably little morphological change, indicating that their evolution has been exceptionally slow and earning them informal status as living fossils. [B. G. Gardiner (1984) Sturgeons as living fossils. Pp. 148–152 in N. Eldredge and S.M. Stanley, eds. Living fossils. Springer-Verlag, New York.] J. Krieger and P.A. Fuerst. (2002) Evidence for a Slowed Rate of Molecular Evolution in the Order Acipenseriformes "Molecular Biology and Evolution" 19:891-897.] This is explained in part by the long inter-generation time, tolerance for wide ranges of temperatureand salinity, lack of predatorsdue to size, and the abundance of prey items in the benthicenvironment. Despite the existence of a fossilrecord, it has been difficult to fully classify the sturgeon species or unambiguously determine their phylogeny. This is in part due to the high individual and ontogenic variation, including geographical clinesin certain features, such as rostrum shape, number of scutesand body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. The wide range of the Acipenseridsand their endangered status have made collection of systematic materials difficult. These factors have led researchers in the past to identify over 40 additional species that were rejected by later workers.W. E. Bemis, E. K. Findeis, and L. Grande. (1997). An overview of Acipenseriformes. Environmental Biology of Fishes 48:25–71.] It is still unclear whether the species in the "Asipenser" and "Huso" genera are monophyletic(descended from one ancestor) or paraphyletic(descended from many ancestors)- though it is clear that the morphologically motivated division between these two genera is not supported by the genetic evidence. There is an ongoing effort to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. [F. Fontana, J. Tagliavini, L. Congiu (2001) Sturgeon genetics and cytogenetics: recent advancements and perspectives. "Genetica" 111: 359–373]
Along with other members of the
Chondrosteiand the Acipenseriformesorder, sturgeon are primarily cartiligenous, lack a vertebral centrum, and are covered with bony plates called " scutes" rather than scales. They also have four " barbels" - unique tactile organs that precede their toothless mouth and are dragged along often murky river bottoms. Sturgeon are distinctly and immediately recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes.
They are primarily
benthicfeeders. With their projecting wedgeshaped snout they stir up the soft bottom, and use the barbels to detect shells, crustaceans and small fish, on which they feed. Having no teeth, they are unable to seize prey, though larger specimens can swallow very large prey items, including whole salmonand even baby seals. [Sergei F. Zolotukhin and Nina F. Kaplanova. (2007) Injuries of Salmon in the Amur River and its Estuary as an Index of the Adult Fish Mortality in the Period of Sea Migrations. NPAFC Technical Report No. 4. [http://www.npafc.org/new/publications/Technical%20Report/TR4/page%2067-69(Zolotukhin).pdf] ]
Sturgeon have been referred to as both the
Leviathans and Methuselahs of freshwater fish. They are among the largest fish: some beluga ("Huso huso") in the Caspian Seareportedly attain over 5.5 m and 2000 kg [Frimodt, C., (1995). Multilingual illustrated guide to the world's commercial coldwater fish. Fishing News Books, Osney Mead, Oxford, England. 215 p. ] while for kaluga ("H. dauricus") in the Amur Riversimilar lengths and over 1000 kg weights have been reported. [Krykhtin, M.L. and V.G. Svirskii (1997). Endemic sturgeons of the Amur River: kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii. Environ. Biol. Fish. 48(1/4):231-239. ] They are also probably the longest-lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. Berg, L.S. (1962). Freshwater fishes of the U.S.S.R. and adjacent countries. volume 1, 4th edition. Israel Program for Scientific Translations Ltd, Jerusalem. (Russian version published 1948).] The combination of slow growth and reproductive rates and the extremely high value placed on mature egg-bearing females make sturgeon particularly vulnerable to overfishing.
Sturgeons are polyploid; some species have 4, 8, or 16 sets of chromosomes.cite web |url=http://biology.mcgill.ca/undergra/c465a/biodiver/2000/shortnose-sturgeon/shortnose-sturgeon.htm |title=Shortnose Sturgeon|author=Anderson, Rachel|accessdate=2007-08-23 |year=2004 |publisher=McGill University]
Range and habitat
Sturgeon range from
subtropicalto subarcticwaters in North Americaand Eurasia. In North America, they range along the Atlantic coast from the Gulf of Mexicoto Newfoundland, including the Great Lakesand the Missouri and Mississippirivers, as well as along the West coast in major rivers from Californiato British Columbia. They occur along the European Atlanticcoast, including the Mediterraneanbasin, in the rivers that flow into the Black, Azov and Caspianseas ( Danube, Dnepr, Volgaand Don), the north-flowing rivers of Russia that feed the Arctic Ocean(Ob, Yenisei, Lena, Kolyma), in the rivers of Central Asia( Amu Daryaand Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur Riveralong the Russian-Chinese border, on Sakhalinisland, and in the Yangtzeand other rivers in northeast China.
Throughout this extensive range, almost all species are highly threatened or vulnerable to extinction due to a combination of habitat destruction, overfishing and pollution.
No species are known to naturally occur south of the equator, though attempts at sturgeon
aquacultureare being made in Uruguay, South Africaand other places. [LA. Burtzev (1999) The History of Global Sturgeon Aquaculture. " Journal of Applied Ichthyology" 15 (4-5), 325–325. doi:10.1111/j.1439-0426.1999.tb00336.x]
Most species are at least partially
anadromous, spawning in fresh water and feeding in nutrient rich brackish waters of estuariesor undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon("Acipenser fulvescens") and the Baikal sturgeon("A. baerii baicalensis"), or have been forced into them by anthropogenic or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon("A. transmontanus") in the Columbia River[S. Duke, P. Anders, G. Ennis, R. Hallock, J. Hammond, S. Ireland, J. Laufle, R. Lauzier, L. Lockhard, B. Marotz, V.L. Paragamian, R. Westerhof (1999) Recovery plan for Kootenai River white sturgeon (Acipenser transmontanus), " Journal of Applied Ichthyology" 15 (4-5), 157–163. ] and Siberian sturgeon("A. baerii") in the Ob basin. [G.I. Ruban, 1999. The Siberian Sturgeon "Acipenser baerii Brandt": Structure and Ecology of the Species, Moscow, GEOS. 235 pp (in Russian).]
In Russia, sturgeon fisheries are of immense value. Early in summer the fish migrate into the rivers or towards the shores of freshwater lakes in large shoals for breeding purposes. The ova are very small, and so numerous that one female has been calculated to produce about three million in one season. The ova of some species have been observed to hatch within very few days after exclusion. In sturgeons that have attained maturity their growth appears to be much slower, although continuing for many years. Frederick the Great placed a number of them in the Garder See Lake in
Pomeraniaabout 1780; some of these were found to be still alive in 1866.Fact|date=February 2007 Professor von Baer also states, as the result of direct observations made in Russia, that the Hausen ("Acipenser huso") attains an age of 100 years, but can live over 210 years.Fact|date=February 2007
In countries like
England, where few sturgeons are caught, sturgeon is included as a royal fishin an act of King Edward II, although it probably only rarely graces the royal table of the present period, or even that of the lord mayor of London, who can claim all sturgeons caught in the Thamesabove London Bridge. Where sturgeons are caught in large quantities, as on the rivers of southern Russia and on the great lakes of North America, their flesh is dried, smoked or salted. The ovaries, which are of large size, are prepared for caviar, for this purpose they are beaten with switches, and then pressed through sieves, leaving the membranous and fibrous tissues in the sieve, whilst the eggs are collected in a tub. The quantity of salt added to them before they are finally packed varies with the season, scarcely any being used at the beginning of winter. Finally, one of the best sorts of isinglassis manufactured from the airbladder. After it has been carefully removed from the body, it is washed in hot water, and cut open in its whole length, to separate the inner membrane, which has a soft consistency, and contains 70% of glutin.
Sturgeon (and, therefore also the caviar trade) are under severe threat from overfishing, poaching and water pollution. [Clover, Charles. 2004. "The End of the Line: How overfishing is changing the world and what we eat". Ebury Press, London. ISBN 0-09-189780-7 ]
In currently accepted
taxonomy, the family Acipenseridae is subdivided into two subfamilies, Acipenserinae, including the genera "Acipenser" and "Huso", and Scaphirhynchinae, including the genera "Scaphirhynchus" and "Pseudosaphirhynchus".FishBase order | order = Acipenseriformes | year = 2007 | month = 12]
Siberian sturgeon, "Acipenser baerii baerii"
Baikal sturgeon, "Acipenser baerii baicalensis"
Shortnose sturgeon, "Acipenser brevirostrum"
Yangtze sturgeon, "Acipenser dabryanus"
Lake sturgeon, "Acipenser fulvescens"
Russian sturgeon, "Acipenser gueldenstaedtii"
Green sturgeon, "Acipenser medirostris"
Sakhalin sturgeon, "Acipenser mikadoi"
Japanese sturgeon, "Acipenser multiscutatus"
Adriatic sturgeon, "Acipenser naccarii"
Fringebarbel sturgeon, "Acipenser nudiventris"
Atlantic sturgeon, "Acipenser oxyrinchus oxyrinchus"
Gulf sturgeon, "Acipenser oxyrinchus desotoi"
Persian sturgeon, "Acipenser persicus"
Sterlet, "Acipenser ruthenus"
Amur sturgeon, "Acipenser schrenckii"
Chinese sturgeon, "Acipenser sinensis"
Starry sturgeon, "Acipenser stellatus"
European sturgeon, "Acipenser sturio" (also [wrongly] "Baltic sturgeon")
White sturgeon, "Acipenser transmontanus"
Beluga sturgeon, "Huso huso"
****Kaluga sturgeon, "Huso dauricus"
Pallid sturgeon, "Scaphirhynchus albus"
Shovelnose sturgeon, "Scaphirhynchus platorynchus"
Alabama sturgeon, "Scaphirhynchus suttkusi"
Dwarf sturgeon, "Pseudoscaphirhynchus hermanni"
Syr Darya sturgeon, "Pseudoscaphirhynchus fedtschenkoi"
Amu Darya sturgeon, "Pseudoscaphirhynchus kaufmanni"
Volga Delta- the largest sturgeon breeding ground in the world
World Sturgeon Conservation Society
*Wolf River-- the sturgeon guard
Saskatchewan River Sturgeon Management Board
* [http://www.fishbase.org/identification/specieslist.cfm?famcode=32&areacode= FishBase info on Acipenser]
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