Scaphirhynchus platorynchus
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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 Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
(often broken off as adults). Shovelnose sturgeon are the most abundant sturgeon, found in the Missouri River and
Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...
systems, and the only commercially fished sturgeon in the
United States of America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
(Pflieger 1997).


Description

The sturgeons of the family Acipenseridae have bony
scute A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
s along the sides and back and four
barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...
on the underside of the
rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...
. A total of 25 extant species of sturgeon are recognized, including 17 within the genus ''Acipenser''. Sturgeon are distributed around the northern part of the Northern Hemisphere (
holarctic distribution The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical regi ...
) and have marine, freshwater, and anadromous members. Sturgeons, including the shovelnose, are highly regarded for their flesh and their
roe Roe ( ) or hard roe is the fully ripe internal egg masses in the ovaries, or the released external egg masses, of fish and certain marine animals such as shrimp, scallop, sea urchins and squid. As a seafood, roe is used both as a cooked in ...
, from which premium grades of
caviar Caviar (also known as caviare; from fa, خاویار, khâvyâr, egg-bearing) 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. Traditionally, the te ...
are made (Barton 2007). They can reach 1m (39.4 in) in length and up to 4.8 kg (10.6 lb) in weight but 50–85 cm (19.7-33.5 in) and 2.5 kg (5.5 lb) is more common. The scientific name ''Scaphirhynchus'', Greek, means "spade snout," and ''platorynchus'', Greek, means "broad snout." The shovelnose sturgeon is characterized by a long slender filament on the upper lobe of the
caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
. They have a flattened rostrum (modified snout) that is also shovel shaped. There are four fringed
barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...
on the ventral side of the rostrum that can be found in a straight line, which is equidistant from the mouth opening to the tip of the snout, unlike
pallid sturgeon The pallid sturgeon (''Scaphirhynchus albus'') is an endangered species of ray-finned fish, endemic to the waters of the Missouri and lower Mississippi river basins of the United States. It may have even reached the St. Croix River before co ...
. The belly of the shovelnose sturgeon is covered with scale-like plates, which is another distinguishing factor from pallid sturgeon who have primarily scaleless bellies. Coloration of the shovelnose sturgeon ranges from a light-brown to buff with a white belly (Pflieger 1997).


Distribution, habitat, and reproduction

The shovelnose sturgeon, as its distribution represents, is impacted very little by
turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids ...
. The Missouri River and the
Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...
systems tend to carry high sediment loads. Here the sturgeon inhabits the open channel or main channel areas of the large rivers. It lives on the bottom, often in areas with swift current and sand or gravel bottom. As with many riverine fish species, the shovelnose sturgeon does not have a restricted home range and may travel long distances (Pflieger 1997). The shovelnose sturgeon feeds on the bottom, using its highly protrusible mouth to suck up its food. The diet is mainly aquatic insect larvae, consisting principally of
mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order ...
, true flies ( Diptera), and
caddisflies The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the ...
. The sturgeon also feed on crustaceans, worms, and small fish (Carlson et al. 1985;Held 1969). As a result, to bottom feeding it is a host to the
glochidia The glochidium (plural glochidia) is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels. These larvae are t ...
(larvae) of several species of freshwater mollusc, including '' Quadrula pustulosa'' (pimpleback), '' Obovaria olivaria'' (hickorynut) and '' Lampsilis teres'' (yellow sandshell). It is the only known host to the hickorynut mussel.Shovelnose Sturgeon Brochure
/ref> A typical sturgeon's life history includes a migration from feeding grounds to breeding grounds in large rivers. During spawning, behavior changes and swimming near the surface occurs. Females do not spawn every year and spawning chronology is not readily evident. Spawning takes place over gravel in fairly swift water. Eggs hatch after 3 to 5 days, and the larvae—about 1 cm long—drift downstream to suitable rearing areas in the river (Barton 2007). Carlson et al. (1985) found that the growth of the shovelnose sturgeon is relatively slow, at 21.3 inches (54.1 cm) in five years.


Commercial importance

The roe of the shovelnose sturgeon is marketed as "hackleback" caviar. As old world sources of Caspian and
Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Rom ...
sturgeon caviar have become
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...
, roe from shovelnose sturgeon and
paddlefish Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their titular elongla ...
have recently become commercially important. The flesh of the sturgeon is widely considered a delicacy, especially smoked sturgeon. Poaching of the shovelnose sturgeon is becoming a problem, as they must be 8–10 years old before spawning can occur, and females are only gravid once every 3 years. There is some interest in marketing the shovelnose sturgeon as an aquarium species.


References

* Barton, M. 2007. ''Bond's Biology of Fishes'', 3rd edition. Thompson Brooks/Cole, Belmont, California. * Carlson, D.M., W.L. Pflieger, L. Trial, and P.S. Haverland. 1985. Distribution, biology, and hybridization of ''Scaphirhynchus albus'' and ''S. platorynchus'' in the Missouri and Mississippi rivers. ''Env. Biol. Fishes'' 14(1):51-59. * Held, J.W. 1969. Some early summer foods of the shovelnose sturgeon in the Missouri River. ''Trans. Am. Fish. Soc.'' 98(3):514-517. * Pflieger, W.L. 1997. ''The Fishes of Missouri''. Conservation Commission of the State of Missouri, Jefferson City, Missouri. * Rafinesque, C.S. 1820. ''Icthyologia Ohiensis''


External links

* * * {{Taxonbar, from=Q2701034 Scaphirhynchus Fish described in 1820 Freshwater fish of North America Taxa named by Constantine Samuel Rafinesque