| Atlantic sturgeon |
(Acipenser oxyrinchus oxyrinchus)
|Family:|| Acipenseridae |
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 period some 245 to 208 million years ago.The family is grouped into four genera: Acipenser , Huso , Scaphirhynchus and Pseudoscaphirhynchus . Four species may now be extinct. Two closely related species, Polyodon spathula (American paddlefish) and Psephurus gladius (Chinese paddlefish, 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. Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America.
Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle-like body that is smooth-skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 7–12 ft (2–3 1⁄2 m) in length. The largest sturgeon on record was a beluga female captured in the Volga estuary in 1827, measuring 7.2 m (24 ft) long and weighing 1,571 kg (3,463 lb). 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 the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction.
Sturgeons retain several primitive characters among the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons.They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. 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.
Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over 5.5 m (18 ft) and 2000 kg (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. 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. 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.
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 adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. 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.River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free-swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach
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;in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural 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 some 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 is known to naturally occur south of the equator, though attempts at sturgeon aquaculture are being made in Uruguay, South Africa, and other places.
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 Riverand Siberian sturgeon (A. baerii) in the Ob basin.
Sturgeons are primarily benthic feeders, with a diet of shells, crustaceans, and small fish. Exceptionally, both Huso species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. 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 and more predatory species can swallow very large prey items, including whole salmon.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.
The sturgeons' electroreceptors are located on the head and are sensitive to weak electric fields generated by other animals or geoelectric sources.The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration.
Many sturgeons leap completely out of the water,usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, 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. Another explanation is that it "simply feels good". There have been some incidents of leaping sturgeon landing in boats, and causing injuries to humans; in 2015, a 5-year-old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
...in May, June and July, the rivers abound with them, at which time it is surprising, though very common to see such large fish elated in the air, by their leaping some yards out of the water; this they do in an erect posture, and fall on their sides, which repeated percussions are loudly heard some miles distance....
Acipenseriform fishes appeared in the fossil record some 245 to 208 million years ago (Mya) near the end of the Triassic, making them among the most ancient of still-living 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.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.
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 (Actinopterygii) have a long evolutionary history culminating in our most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars.
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.Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques.
The phylogeny of the Acipenseridae, as on the cladogram, shows that they have evolved from among the bony fishes.Approximate dates are from Near et al., 2012.
In currently accepted taxonomy, the class Actinopterygii and the order Acipenseriformes are both clades. The family Acipenseridae is subdivided into 2 subfamilies, the Acipenserinae including the genera Acipenser and Huso , and Scaphirhynchinae, including the genera Scaphirhynchus and Pseudoscaphirhynchus .
The family contains 8 extinct species and 28 extant species/subspecies (include 1 species of Sterlet and 2 species of living fossils), in 4 genera:
Globally, sturgeon fisheries are of great value, primarily as a source for caviar, but also for flesh.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 and endangered of all wildlife resources.
During the 19th century, the US was the global leader in caviar production, having cornered 90% of the world's caviar trade.Atlantic sturgeon once thrived along the east coast from Canada down to Florida. They were in such abundance in the Hudson River, they were called "Albany beef" and sturgeon eggs were given away at local bars as an accompaniment to 5¢ beer. White sturgeon populations along the US west coast declined simultaneously under the pressure of commercial fishing and human encroachment. Within the course of a century, the once abundant sturgeon fisheries in the US and Canada had drastically declined, and in some areas had been extirpated under the pressure of commercial overharvesting, pollution, human encroachment, habitat loss, and the damming of rivers that blocked their ancestral migration to spawning grounds.
By the turn of the century, commercial production of sturgeon caviar in the US and Canada had come to an end. Regulatory protections and conservation efforts were put in place by state and federal resource agencies in the US and Canada, such as the 1998 US federal moratorium that closed all commercial fishing for Atlantic sturgeon.It was during the 20th century that Russia grew to become the global leader as the largest producer and exporter of caviar. As with the decline in sturgeon populations in the US and Canada, the same occurred with sturgeon populations in the Caspian Sea.
Beginning with the 1979 US embargo on Iran, poaching and smuggling sturgeon caviar was big business but an illegal and dangerous one.Officers with the Washington Department of Fish and Wildlife (WDFW) busted a poaching ring that was based in Vancouver, Washington. The poachers had harvested 1.65 tons of caviar from nearly 2,000 white sturgeon that were poached from the Columbia River. The caviar was estimated to be worth around $2 million. WDFW busted another ring in 2003, and conducted an undercover sting operation in 2006-2007 that resulted in 17 successful attempts out of a total of 19.
In response to concerns over the future of sturgeons and associated commercial products, international trade for all species of sturgeons has been regulated under CITES since 1998.
Sturgeons are long-lived, late maturing fishes with reproductive cycles that include long migrations, and require specific environmental conditions.They are an ancient species that have survived for millions of years but their future is threatened, due in part to their inherent ancestral characteristics and reproductive specificities. The negative impacts of overfishing, poaching, habitat destruction, and the construction of dams that have altered or blocked their annual migration to ancestral spawning grounds have taken a serious toll. Some species of sturgeon are extinct, several are on the verge of extinction, including the Chinese sturgeon, the highly prized beluga sturgeon, and the Alabama sturgeon. Many species are classified as threatened or endangered with noticeable declines in sturgeon populations as the demand for caviar increases. IUCN data indicates that over 85% of sturgeon species are at risk of extinction, making them more critically endangered than any other group of animal species.
In addition to global restocking efforts, the monitoring of populations and habitat, and various other conservation efforts by national and state resource agencies as applicable to their respective countries, several conservation organizations have been formed to assist in the preservation of sturgeons around the world. On a global scale, one such organization is the World Sturgeon Conservation Society (WSCS) whose primary objectives include fostering the "conservation of sturgeon species and restoration of sturgeon stocks world-wide”, and supporting the "information exchange among all persons interested in sturgeons."The North American Sturgeon and Paddlefish Society (NASPS) and Gesellschaft zur Rettung des Störs e.V. are WSCS affiliates. WSCS has been instrumental in organizing global conferences where scientists and researchers can exchange information and address the various conservation challenges that threaten the future of sturgeons. Conservation efforts at the grass roots level are also instrumental in helping to preserve sturgeon populations, such as Sturgeon For Tomorrow which was founded in 1977, consists of volunteers and a sturgeon guarding program to monitor known spawning sites. The organization has grown exponentially over the years and has become "the largest citizen advocacy group for sturgeon in the world", and has expanded with affiliate chapters in other states that have sturgeon populations.
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.
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.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.
Sturgeons were declared to be a royal fish under a statute dating back to 1324 by King Edward II of England. Technically, the British monarchy still owns all sturgeons, whales, and dolphins that inhabit the waters around England and Wales.Under the law of the United Kingdom any sturgeons captured within the realm are personal property of the monarch.
In heraldry, a sturgeon is the symbol on the coat of arms for Saint Amalberga of Temse.
Acipenseriformes is an order of basal ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families.
Caviar is a food consisting of salt-cured roe of the family Acipenseridae. Caviar is considered a delicacy and is eaten as a garnish or a spread. The roe can be "fresh" (non-pasteurized) or pasteurized, with pasteurization reducing its culinary and economic value.
The Beluga or Great sturgeon 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 formerly in the Adriatic Sea. Going on maximum size, it is the eight most massive living species of bony fish. Heavily fished for the female's valuable roe, known as beluga caviar, wild populations have been greatly reduced by overfishing and poaching.
The kaluga is a large predatory sturgeon found in the Amur River basin. Also known as the river beluga, they are claimed to be the largest freshwater fish in the world, with a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18.6 ft). The kaluga is one of the biggest of the sturgeon family. Like the slightly larger beluga, it spends part of its life in salt water. Unlike the beluga, this fish has 5 major rows of dermal scutes, nail-like teeth in its jaws, and feeds on salmon and other fish in the Amur. They have gray-green to black backs with a yellowish green-white underbelly.
Acipenser is a genus of sturgeons. With 17 living species, it is the largest genus in the order Acipenseriformes. They are native to Europe, Asia and North America, and most species are threatened.
The Chinese sturgeon is a critically endangered member of the family Acipenseridae in the order Acipenseriformes. Historically, this anadromous fish was found in China, Japan, and the Korean Peninsula, but it has been extirpated from most regions due to habitat loss and overfishing.
Ossetra caviar is one of the most prized and expensive types of caviar. It is obtained from the Ossetra sturgeon which weighs 50-400 pounds and can live up to 50 years.
The European sea sturgeon, also known as the Atlantic sturgeon or common sturgeon, is a species of sturgeon previously found on most coasts of Europe. It is anadromous and breeds in rivers. It is currently a critically endangered species. Although the name Baltic sturgeon sometimes has been used, it has now been established that sturgeon of the Baltic region are A. oxyrinchus, a species otherwise restricted to the Atlantic coast of North America.
White sturgeon is a species of sturgeon in the family Acipenseridae of the order Acipenseriformes. They are an anadromous fish species ranging in the Eastern Pacific; from the Gulf of Alaska to Monterey, California. However, some are landlocked in the Columbia River Drainage, Montana, and Lake Shasta in California, with reported sightings in northern Baja California, Mexico.
The Atlantic sturgeon is a member of the family Acipenseridae and along with other sturgeon it is sometimes considered a living fossil. The Atlantic sturgeon is one of two subspecies of A. oxyrinchus, the other being the Gulf sturgeon. The main range of the Atlantic sturgeon is in eastern North America, extending from New Brunswick, Canada, to the eastern coast of Florida, United States. A disjunct population occurs in the Baltic region of Europe. The Atlantic sturgeon was in great abundance when the first European settlers came to North America, but has since declined due to overfishing and water pollution. It is considered threatened, endangered, and even locally extinct in many of its original habitats. The fish can reach 60 years of age, 15 ft (4.6 m) in length and over 800 lb (360 kg) in weight.
The shovelnose sturgeon, Scaphirhynchus platorynchus, is the smallest species of freshwater sturgeon native to North America. It is often called "hackleback", "sand sturgeon", or "switchtail." Switchtail refers to the long filament found on the upper lobe of the caudal fin. Shovelnose sturgeon are the most abundant sturgeon, found in the Missouri River and Mississippi River systems, and the only commercially fished sturgeon in the United States of America.
The starry sturgeon also known as stellate sturgeon or sevruga, is a species of sturgeon. It is native to the Black, Azov, Caspian and Aegean sea basins, but it has been extirpated from the last and it is predicted that the remaining natural population will follow soon due to overfishing. It is considered critically endangered by the IUCN and international trade in this species is restricted by CITES. The starry sturgeon is an anadromous species, which migrates up rivers to spawn.
The Persian sturgeon is a species of fish in the family Acipenseridae. It is found in the Caspian Sea and to a lesser extent the Black Sea and ascends certain rivers to spawn, mainly the Volga, Kura, Araks and Ural Rivers. It is heavily fished for its flesh and its roe and is limited in its up-river migrations by damming of the rivers. Young fish feed on small invertebrates, graduating to larger prey such as crabs and fish as they grow. The threats faced by this fish include excessive fishing with the removal of immature fish before they have bred, damming of the rivers, loss of spawning areas and water pollution. The International Union for Conservation of Nature has listed the fish as critically endangered and has suggested that the increased provision of hatcheries could be of benefit.
The Siberian sturgeon is a species of sturgeon in the family Acipenseridae. It is most present in all of the major Siberian river basins that drain northward into the Kara, Laptev and East Siberian Seas, including the Ob, Yenisei Lena, and Kolyma Rivers. It is also found in Kazakhstan and China in the Irtysh River, a major tributary of the Ob. The species epithet honors the German Russian biologist Karl Ernst von Baer.
The Russian sturgeon, also known as the diamond sturgeon or Danube sturgeon, is a species of fish in the family Acipenseridae. It is found in Azerbaijan, Bulgaria, Georgia, Iran, Kazakhstan, Romania, Russia, Turkey, Turkmenistan, and Ukraine. It is also found in the Caspian Sea. This fish can grow up to about 235 cm (93 in) and weigh 115 kg (254 lb). Russian sturgeon mature and reproduce slowly, making them highly vulnerable to fishing. It is distinguished from other Acipenser species by its short snout with a rounded tip as well as its lower lip which is interrupted at its center.
Acipenser naccarii, the Adriatic sturgeon, is a species of fish in the family Acipenseridae. It is native to the Adriatic Sea and large rivers which flow in it of Albania, Greece, Italy, and States of former-Yugoslavia. Specimens can be seen in several public aquarium, such the Milan Aquarium, Aquarium Finisterrae, Aquarium of the Po, and Oasis of Sant'Alessio in Lombardy.
Pseudoscaphirhynchus is a genus of relatively small, highly threatened sturgeons that are restricted to the Aral Sea system, including the Amu Darya and Syr Darya river basins, in Central Asia.
The Amu Darya sturgeon or false shovelnose sturgeon is a critically endangered species of fish in the family Acipenseridae. It is found in Turkmenistan and Uzbekistan, and perhaps Afghanistan and Tajikistan. It inhabits quite shallow flowing waters that are turbid and muddy.
Acipenser oxyrinchus is a species of sturgeon.
Huso is a genus of large sturgeons from Eurasia. It contains two species, which both are critically endangered:
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