Der Schaufelstör (engl.: shovelnose sturgeon, auch: hackleback, sand sturgeon, switchtail; Scaphirhynchus platorynchus) ist eine stark gefährdete Fischart aus der Familie der Störe (Acipenseridae) in den Vereinigten Staaten. Sie ist die kleinste Art der Süßwasser-Störe und endemisch in Missouri und Mississippi River. Er wird kommerziell befischt.[1]
| Hackleback | ||||||||||||
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Hackleback | ||||||||||||
| Systematik | ||||||||||||
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| Wissenschaftlicher Name | ||||||||||||
| Scaphirhynchus platorynchus | ||||||||||||
| (Rafinesque, 1820) |
Name
Der deutsche und englische und griechische Name beziehen sich auf das schaufelförmige Rostrum. Scaphirhynchus bedeutet übersetzt "Spatenschnautze" und platorynchus zusätzlich "breitschnauzig". Das Englische "Switchtail" bezieht sich auf einen langen Strahl der Schwanzflosse, der bei älteren Exemplaren allerdings oft verloren ist.
Description
Die Störe zeichnen sich durch reihig angeordnete Hornschuppen entlang der Seiten und vier Barteln auf der Unterseite des Rostrum. Sie werden wegen ihres wohlschmeckenden Fleisches und ihres Rogen, der zu erstklassigem Kaviar verarbeitet wird[2], kommerziell befischt.
Schaufelstöre erreichen 1 m Länge und 4,8 kg Gewicht. Die meisten Exemplare erreichen Längen von 50–85 cm und 2,5 kg.
The shovelnose sturgeon is characterized by a long slender filament on the upper lobe of the caudal fin. They have a flattened rostrum (modified snout) that is also shovel shaped. There are four fringed barbels 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 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).
Verbreitung und Lebensraum
The shovelnose sturgeon, as its distribution represents, is impacted very little by turbidity. The Missouri River and the Mississippi River 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, true flies (Diptera), and caddisflies. 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 (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.[3]
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 growth of the shovelnose sturgeon is relatively slow, at 21.3 inches (54.1 cm) in five years.
Kommerzielle Bedeutung
The roe of the shovelnose sturgeon is marketed as "hackleback" caviar. As old world sources of Caspian and Black Sea sturgeon caviar have become endangered, roe from shovelnose sturgeon and paddlefish have recently become commercially important.[4] 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.[3]
Literatur
- M. Barton: Bond's Biology of Fishes. Thompson Brooks/Cole, Belmont, California 2007.
- D.M. Carlson, W.L. Pflieger, L. Trial, P.S. Haverland: Distribution, biology, and hybridization of Scaphirhynchus albus and S. platorynchus in the Missouri and Mississippi rivers. In: Env. Biol. Fishes 14(1) 1985: 51-59.
- J.W. Held: Some early summer foods of the shovelnose sturgeon in the Missouri River. In: Trans. Am. Fish. Soc. 98(3) 1969: 514-517.
- W.L. Pflieger: The Fishes of Missouri. Conservation Commission of the State of Missouri, Jefferson City, Missouri 1997.
Einzelnachweise
- ↑ Pflieger 1997.
- ↑ Barton 2007
- ↑ a b Shovelnose Sturgeon Brochure
- ↑ American Hackleback Caviar