Sturgeon

Sturgeon
Temporal range: Upper Cretaceous-Holocene[1]
Atlantic sturgeon
(Acipenser oxyrinchus oxyrinchus)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Acipenseriformes
Family: Acipenseridae
Bonaparte, 1831
Subfamilies

Acipenserinae
Scaphirhynchinae
See text for genera and species.

Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. Their evolution dates back to the Triassic some 245 to 208 million years ago.[2] The family is grouped into four genera: Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. Four species may now be extinct.[3] Two closely related species, Polyodon spathula (paddlefish) and Psephurus gladius (Chinese paddlefish, possibly extinct) are of the same order, Acipenseriformes, but are in the family Polyodontidae and are not considered to be "true" sturgeons. Both sturgeons and paddlefish have been referred to as "primitive fishes" because their morphological characteristics have remained relatively unchanged since the earliest fossil record.[4][5] Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America.[6]

Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to that of sharks, and an elongated spindle-like body that is smooth-skinned, scaleless and armored with 5 lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 7–12 feet (2-3½ m) in length. The largest sturgeon on record was a Beluga female captured in the Volga estuary in 1827, weighing 1,571 kg (3,463 lb) and 7.2 m (24 ft) long. Most sturgeons are anadromous bottom-feeders which migrate upstream to spawn but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean.

Several species of sturgeon are harvested for their roe which is processed into caviar—a luxury food and the reason why caviar-producing sturgeons are among the most valuable of all wildlife resources.[7] They are particularly vulnerable to overexploitation and other threats, including pollution and habitat fragmentation. Most species of sturgeon are considered to be at risk of extinction, making them more critically endangered than any other group of species.[8]

In art, a sturgeon is the symbol on the coat of arms for Saint Amalberga of Temse.[9]

Evolution

Acipenseriform fishes appeared in the fossil record some 245 to 208 million years ago presumably near the end of the Triassic, making them among the most ancient of actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils.[10][11] This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. Although their evolution has been remarkably slow, they are a highly evolved living fossil, and do not closely resemble their ancestral chondrosteans. They do however still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension.[12]

Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray-finned fishes have a long evolutionary history culminating in our most familiar fishes, past adaptive radiations have left only a few survivors, like sturgeons and garfish.[13]

The wide range of the acipenserids and 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 scientists.[14] It is still unclear whether the species in the Acipenser 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.[11][15]

Physical characteristics

Sturgeon skull - a, Rostrum; b, nasal capsule; c eye-socket; d, foramina for spinal nerves; e, notochord; g, quadrate bone; h, hyomandibular bone; i, mandible; j. basibranchials; k, ribs; l, hyoid bone; I, II, III, IV, V, branchial arches.

Sturgeons retain several primitive characters among the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because the skeleton is almost entirely cartilaginous. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one: sturgeon ancestors had bony skeletons.[12][16][17] They also lack vertebral centra, and are partially covered with 5 lateral rows of bony plates called scutes rather than scales.[18] They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray-finned fish is inside the body wall, although the ray-like structures in the webbing of the fins can be seen externally.

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 Sea reportedly attain over 5.5 m (18 ft) and 2000 kg[19] (4400 lb) while for kaluga (H. dauricus) in the Amur River, similar lengths and over 1,000 kg (2,200 lb) weights have been reported.[20] They are also among the longest-lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more.[21] 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 four, eight, or 16 sets of chromosomes.[22]

Life cycle

Sturgeons are long-lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in Spring, clear water with shallow rock or gravel substrate where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs but not all will be fertilized. The fertilized eggs become sticky and will adhere to the bottom substrate upon contact. It takes 8–15 days for the embryos to mature into larval fish. During that time, they are dependent on their yolk sac for nourishment.[23][24] River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs where the free-swimming fry will spend their first year feeding on insect larvae and crustacea. During their first year of growth, they will reach 18 to 20 cm (7.1 to 7.9 in) in length and migrate back into the swift-flowing currents in the main stem river.

Range and habitat

Sturgeon range from subtropical to subarctic waters in North America and Eurasia. In North America, they range along the Atlantic Coast from the Gulf of Mexico to Newfoundland, including the Great Lakes and the St. Lawrence, Missouri, and Mississippi Rivers, as well as along the West Coast in major rivers from California and Idaho to British Columbia. They occur along the European Atlantic coast, including the Mediterranean basin, especially in the Adriatic Sea and the rivers of North Italy;[25] in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga and Don); the north-flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian-Chinese border, on Sakhalin Island, and in the Yangtze and other rivers in northeast China.[21][26]

Throughout this extensive range, almost all species are highly threatened or vulnerable to extinction due to a combination of habitat destruction, overfishing, and pollution.[26]

No species are known to naturally occur south of the equator, though attempts at sturgeon aquaculture are being made in Uruguay, South Africa, and other places.[27]

Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient-rich, brackish waters of estuaries or 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[28] and Siberian sturgeon (A. baerii) in the Ob basin.[29]

Behavior

The underside and mouth of a sturgeon

Sturgeon are primarily benthic feeders, with a diet of shells, crustaceans and small fish. They feed by extending their syphon-like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals can swallow very large prey items, including whole salmon.[30] Sturgeons feed non-visually. They are believed to use a combination of sensors, including olfactory, tactile and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini.[31]

The sturgeons' electroreceptors are located on the head and are sensitive to weak electric fields generated by other animals or geoelectric sources.[32] The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration.[31]

In 1731, an observer of leaping sturgeon wrote:

Many sturgeon leap completely out the water,[34] usually making a loud splash which can be heard half a mile away on the surface and probably further under water. It is not known why they do this, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air.[35] Another explanation is that it "simply feels good".[33] Leaping sturgeon are known to occasionally cause injuries to humans in boats;[36] in 2015, a 5-year-old girl died after a sturgeon leapt from the Suwannee River and struck her.[37]

Conservation status

Because of their long reproductive cycles, long migrations, and sensitivity to environmental conditions, many species are under severe threat from overfishing,[38] poaching, water pollution, and damming of rivers.[39] There is also a noticeable decline in sturgeon populations as the demand for caviar increases. According to the IUCN, over 85% of sturgeon species are classified as at risk of extinction, making them more critically endangered than any other group of species.[8][40]

A 2013 study on the critically endangered sturgeon populations in the Danube River Basin determined that ongoing illegal fishing activity and caviar trade is threatening the future of Danube sturgeons.[41] Jutta Jahrl, a conservation expert with the World Wildlife Federation stated that "Romania and Bulgaria are home to the only viable wild sturgeon populations left in the European Union, but unless this sophisticated illegal fishing is stopped, these fish are doomed”.[41]

Uses

Woman selling sturgeon at a market in Türkmenbaşy, Turkmenistan

Globally, sturgeon fisheries are of great value, primarily as a source for caviar, but also for flesh.

Before 1800, swim bladders of sturgeon (primarily Beluga sturgeon from Russia) were used as a source of isinglass, a form of collagen used historically for the clarification of wine and beer, as a predecessor for gelatin, and to preserve parchments.[42]

The Jewish law of kashrut, which only permits the consumption of fish with scales, forbids sturgeon, as they have ganoid scales instead of the permitted ctenoid and cycloid scales. While all Orthodox groups forbid the consumption of sturgeon, some conservative groups do allow it.[43][44] The theological debate over its kosher status can be traced back to such 19th-century reformers as Aron Chorin, though its consumption was already common in European Jewish communities.[45]

Classification

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.[26]

Subfamily Genera Image Species Common name Max reported Fish-
base		 FAO IUCN status
Length Weight Age
A

c

i

p

e

n

s

e

r

i

d

a

e		 Acipenserinae Acipenser Acipenser baerii Siberian sturgeon 200 cm 210 kg 60 yrs [46] [47] Endangered[48]
Acipenser brevirostrum Shortnose sturgeon 143 cm 23 kg 67 yrs [49] [50] Endangered[51]
Acipenser dabryanus Yangtze sturgeon 250 cm [52] [53] Critically endangered[54]
Acipenser fulvescens Lake sturgeon 274 cm 125 kg 152 yrs [55] [56] Vulnerable[57]
Acipenser gueldenstaedtii Russian sturgeon 236 cm 115 kg 46 yrs [58] [59] Critically endangered[60]
Acipenser medirostris Green sturgeon 250 cm 159 kg 60 yrs [61] [62] Near threatened[63]
Acipenser mikadoi Sakhalin sturgeon 150 cm [64] [65] Critically endangered[66]
Acipenser naccarii Adriatic sturgeon 200 cm 25 kg [67] [68] Critically endangered[69]
Acipenser nudiventris Fringebarbel sturgeon 200 cm 80 kg [70] [71] Critically endangered[72]
Acipenser oxyrinchus Atlantic or Gulf sturgeon 403 cm 60 yrs [73] [74] Near threatened[75]
Acipenser persicus Persian sturgeon 242 cm 70 kg [76] Critically endangered[77]
Acipenser ruthenus Sterlet 125 cm 16 kg 20 yrs [78] [79] Vulnerable[80]
Acipenser schrenckii Amur sturgeon 300 cm 190 kg 65 yrs [81] [82] Critically endangered[83]
Acipenser sinensis Chinese sturgeon 400 cm 600 kg 13 yrs [84] [85] Critically endangered[86]
Acipenser stellatus Starry sturgeon 220 cm 80 kg 27 yrs [87] [88] Critically endangered[89]
Acipenser sturio European sea sturgeon 600 cm 400 kg 100 yrs [90] [91] Critically endangered[92]
Acipenser transmontanus White sturgeon 610 cm 816 kg 104 yrs [93] [94] Least concern[95]
Huso Huso dauricus Kaluga sturgeon 560 cm 1000 kg 80 yrs [96] [97] Critically endangered[98]
Huso huso Beluga sturgeon 800 cm 1571 kg 118 yrs [99] [100] Critically endangered[101]
Scaphi-
rhynchinae		 Scaphi-
rhynchus		 Scaphirhynchus albus Pallid sturgeon 200 cm 130 kg 41 yrs [102] [103] Endangered[104]
Scaphirhynchus platorynchus Shovelnose sturgeon 100 cm 7 kg 43 yrs [105] [106] Vulnerable[107]
Scaphirhynchus suttkusi Alabama sturgeon [108] Critically endangered[109]
Pseudo-
scaphi-
rhynchus		 Pseudoscaphirhynchus fedtschenkoi Syr Darya sturgeon 65 cm [110] Critically endangered[111]
Pseudoscaphirhynchus hermanni Dwarf sturgeon 28 cm 0.5 kg 6 yrs [112] [113] Critically endangered[114]
Pseudoscaphirhynchus kaufmanni Amu Darya sturgeon 75 cm 2 kg [115] [116] Critically endangered[117]

Species

A young lake sturgeon (Acipenser fulvescens)
European sturgeon (Huso huso) feeding on another fish

Notes

  1. ↑ Froese, Rainer, and Daniel Pauly, eds. (2009). "Acipenseridae" in FishBase. January 2009 version.
  2. ↑ Birstein, V.J., R. Hanner, and R. DeSalle. 1997. Phylogeny of the Acipenseriformes: cytogenic and molecular approaches. Environmental Biology of Fishes 48: 127-155.
  3. ↑ Chadwick, Niki; Drzewinski, Pia; Hurt, Leigh Ann (March 18, 2010). "Sturgeon More Critically Endangered Than Any Other Group of Species". International News Release. International Union for Conservation of Nature. Retrieved September 19, 2015.
  4. ↑ Chesapeake Bay Field Office. "Atlantic Sturgeon". U.S. Fish & Wildlife Service. Retrieved June 10, 2014.
  5. ↑ "Lake sturgeon". Minnesota Dept. of Natural Resources. Retrieved June 10, 2014.
  6. ↑ "Biology of Fishes (chapter: Biodiversity II: Primitive Bony Fishes and The Rise of Modern Teleosts)" (PDF). University of Washington. Retrieved May 30, 2014.
  7. ↑ "Sturgeons". Convention on International Trade in Endangered Species of Wild Fauna and Flora. Retrieved September 21, 2015.
  8. 1 2 "Sturgeon more critically endangered than any other group of species". IUCN, the International Union for Conservation of Nature. 18 March 2010. Retrieved December 6, 2010.
  9. ↑ Cromwell, James (1 July 2009). Saints, Signs, and Symbols: The Symbolic Language of Christian Art. Church Publishing Inc. p. 21. Retrieved 15 May 2017.
  10. ↑ 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.
  11. 1 2 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.
  12. 1 2 Gene Helfman; Bruce B. Collette; Douglas E. Facey; Brian W. Bowen (3 April 2009). The Diversity of Fishes: Biology, Evolution, and Ecology. John Wiley & Sons. pp. 252–. ISBN 978-1-4443-1190-7.
  13. ↑ "Craniata, (2) Subclass Actinopterygii-the ray-finned fishes". San Francisco State University. Retrieved May 31, 2014.
  14. ↑ W. E. Bemis, E. K. Findeis, and L. Grande. (1997). An overview of Acipenseriformes. Environmental Biology of Fishes 48:25–71.
  15. ↑ F. Fontana, J. Tagliavini, L. Congiu (2001) Sturgeon genetics and cytogenetics: recent advancements and perspectives. Genetica 111: 359–373
  16. ↑ Caleb E. Finch (16 May 1994). Longevity, Senescence, and the Genome. University of Chicago Press. pp. 134–. ISBN 978-0-226-24889-9.
  17. ↑ J. D. McPhail (28 September 2007). Freshwater Fishes of British Columbia (The). University of Alberta. pp. 23–. ISBN 978-0-88864-853-2.
  18. ↑ "Atlantic Sturgeon". Virginia Institute of Marine Science. 2009. Retrieved August 26, 2016.
  19. ↑ Frimodt, C., (1995). Multilingual illustrated guide to the world's commercial coldwater fish. Fishing News Books, Osney Mead, Oxford, England. 215 p.
  20. ↑ 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.
  21. 1 2 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).
  22. ↑ Anderson, Rachel (2004). "Shortnose Sturgeon". McGill University. Archived from the original on 2007-10-24. Retrieved 2007-08-23.
  23. ↑ "Fish & Habitats– White Sturgeon (Acipenser transmontanus) in British Columbia". British Columbia Ministry of Environment, Ecosystems Branch. Retrieved October 28, 2015.
  24. ↑ "Life Cycle of the White Sturgeon" (PDF). HSBC Fraser River Sturgeon Education Program. Fraser River Conservation Society. Retrieved October 28, 2015.
  25. ↑ LIFE 04NAT/IT/000126 “Conservation and Breeding of Italian Cobice Endemic Sturgeon”
  26. 1 2 3 Froese, Rainer, and Daniel Pauly, eds. (2016). "Acipenseriformes" in FishBase. 12 2016 version.
  27. ↑ 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
  28. ↑ 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.
  29. ↑ G.I. Ruban, 1999. The Siberian Sturgeon Acipenser baerii Brandt: Structure and Ecology of the Species, Moscow, GEOS. 235 pp (in Russian).
  30. ↑ 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.
  31. 1 2 Zhang, X., Song, J., Fan, C., Guo, H., Wang, X. and Bleckmann, H. (2012). "Use of electrosense in the feeding behavior of sturgeons". Integrative Zoology. 7 (1): 74–82.
  32. ↑ Herzog, H. (2011). "Response properties of the electrosensory neurons in hindbrain of the white sturgeon, Acipenser transmontanus". Neuroscience Bulletin. 27 (6): 422–429.
  33. 1 2 Waldman, J. (2001). "Outdoors: The lofty mystery of why sturgeon leap". The New York Times.
  34. ↑ Video of leaping sturgeon can be see at approximately 6:50
  35. ↑ Sulak, K. J.; Edwards, R. E.; Hill, G. W.; Randall, M. T. (2002). "Why do sturgeons jump? Insights from acoustic investigations of the Gulf sturgeon in the Suwannee River, Florida, USA". Journal of Applied Ichthyology. 18 (4‐6): 617–620. doi:10.1046/j.1439-0426.2002.00401.x.
  36. ↑ Wilson, J.P., Burgess, G., Winfield, R.D. and Lottenberg, L. (2009). "Sturgeons versus surgeons: leaping fish injuries at a level I trauma center". The American Surgeon. 75 (3): 220–222.
  37. ↑ "Leaping sturgeon kills girl in boat on Florida river". The Huffington Post. 2015.
  38. ↑ 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
  39. ↑ Pallid Sturgeon - Montana Fish, Wildlife and Parks
  40. ↑ Species, status and population trend of Sturgeon on the IUCN Red List of Threatened Species (pdf)
  41. 1 2 http://www.traffic.org/home/2013/6/18/europes-last-wild-sturgeons-threatened-by-ongoing-illegal-fi.html Sturgeon illegal fishing
  42. ↑ Davidson, Alan (1999). ""Isinglass"". Oxford Companion to Food. p. 407. ISBN 0-19-211579-0.
  43. ↑ http://cor.ca/en/15#12
  44. ↑ "Sturgeon: A controversial fish.". bluethread.com.
  45. ↑ Lupovich, Howard (2010). "7". Jews and Judaism in World History. p. 258. ISBN 0-203-86197-3.
  46. ↑ Froese, Rainer and Pauly, Daniel, eds. (2013). "Acipenser baerii" in FishBase. November 2013 version.
  47. ↑ Acipenser baerii (Brandt, 1869) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  48. ↑ Ruban, G. & Bin Zhu (2010). "Acipenser baerii". IUCN Red List of Threatened Species. Version 2013.1. International Union for Conservation of Nature. Retrieved 11 November 2013.
  49. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser brevirostrum" in FishBase. November 2012 version.
  50. ↑ Acipenser brevirostrum (Lesueur, 1818) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  51. ↑ Friedland, K.D. & Kynard, B. (2004). "Acipenser brevirostrum". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  52. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser dabryanus" in FishBase. November 2012 version.
  53. ↑ Acipenser dabryanus (A. H. A. Duméril, 1869) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  54. ↑ Qiwei, W. (2010). "Acipenser dabryanus". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  55. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser fulvescens" in FishBase. November 2012 version.
  56. ↑ Acipenser fulvescens (Rafinesque) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  57. ↑ St. Pierre, R. & Runstrom, A. (2004). "Acipenser fulvescens". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  58. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser gueldenstaedtii" in FishBase. November 2012 version.
  59. ↑ Acipenser gueldenstaedtii (J. F. Brandt & Ratzeburg, 1833) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  60. ↑ Gesner, J., Freyhof, J. & Kottelat, M. (2010). "Acipenser gueldenstaedtii". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  61. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser medirostris" in FishBase. November 2012 version.
  62. ↑ Acipenser medirostris (Ayres, 1854) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  63. ↑ St. Pierre, R. & Campbell, R.R. (2006). "Acipenser medirostris". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  64. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser mikadoi" in FishBase. November 2012 version.
  65. ↑ Acipenser mikadoi (Hilgendorf, 1892) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  66. ↑ Mugue, N. (2010). "Acipenser mikadoi". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  67. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser naccarii" in FishBase. November 2012 version.
  68. ↑ Acipenser naccarii (Bonaparte, 1836) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  69. ↑ Bronzi, P., Congiu, L., Rossi, R., Zerunian, S. & Arlati, G. (2011). "Acipenser naccarii". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  70. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser nudiventris" in FishBase. November 2012 version.
  71. ↑ Acipenser nudiventris (Lovetsky, 1828) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  72. ↑ Gesner, J., Freyhof, J. & Kottelat, M. (2010). "Acipenser nudiventris". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  73. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser oxyrinchus" in FishBase. November 2012 version.
  74. ↑ Acipenser oxyrinchus (Vladykov, 1955) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  75. ↑ St. Pierre, R. & Parauka, F.M. (2006). "Acipenser oxyrinchus". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  76. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser persicus" in FishBase. November 2012 version.
  77. ↑ Gesner, J., Freyhof, J. & Kottelat, M. (2010). "Acipenser persicus". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  78. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser ruthenus" in FishBase. November 2012 version.
  79. ↑ Acipenser ruthenus (Linnaeus, 1758) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  80. ↑ Gesner, J., Freyhof, J. & Kottelat, M. (2010). "Acipenser ruthenus". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
  81. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). "Acipenser schrenckii" in FishBase. November 2012 version.
  82. ↑ Acipenser schrenckii (J. F. Brandt, 1869) FAO, Species Fact Sheet. Retrieved 11 November 2013.
  83. ↑ Ruban, G. & Qiwei, W. (2010). "Acipenser schrenckii". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 11 November 2013.
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  94. ↑ Acipenser transmontanus (J. Richardson, 1836) FAO, Species Fact Sheet. Retrieved 11 November 2013.
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  97. ↑ Huso dauricus (Georgi, 1775) FAO, Species Fact Sheet. Retrieved 11 November 2013.
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  113. ↑ Pseudoscaphirhynchus hermanni (Kessler, 1877) FAO, Species Fact Sheet. Retrieved 11 November 2013.
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References

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