The shovelnose sturgeon (Scaphirhynchus platorynchus), also called hackleback or switchtail, is a fish living only in the Missouri and Mississippi Rivers of the United States. It is the most abundant species of sturgeon, the smallest freshwater species, and the only sturgeon to be commercially fished in the United States. Shovelnose sturgeons, like other sturgeons, are valued for their meat and their caviar.
Sturgeons are fish of the Acipenseridae family, comprising about 25 species in four genera: Acipenser, Huso, Scaphirhynchus, and Pseudoscaphirhynchus. All species are threatened, and even the most abundant species, the shovelnose sturgeon, is of vulnerable conservation status. Sturgeons are among the most commercially valuable fish. There are marine and freshwater species, and some live in both types of environment. Sturgeons are distributed throughout the northern hemisphere.
Shovelnose sturgeons are light brown, with white bellies. They feature a flat, shovel-shaped snout, a long filament attached to their tail fin, and four curved barbels on their chin. Their bellies are covered with scales, unlike the closely related pallid sturgeon (Scaphirhynchus albus), also native to the Missouri and Mississippi Rivers. Sturgeons have hard, plate-like scales called ganoid scales.
Like most sturgeon species, shovelnose sturgeons are bottom-feeders. Their diet consists mainly of insect larvae, small crustaceans and fish, and worms. The shovelnose sturgeon is also a host to the parasitic larvae of a number of mollusc or mussel species, and is the only species to host the larvae of the hickorynut mussel (Obovaria olivaria).
Shovelnose sturgeons migrate upstream to breed about every three years. In the breeding season, the behavior of the fish changes, and they swim more closely to the surface. The females lay eggs in fast moving water over gravel.
The eggs hatch three to five days after spawning, and the hatchlings are carried downstream on the current. Like most sturgeons, the shovelnose sturgeon is slow to grow. It only becomes able to breed when it is eight to ten years old.
Both the flesh and the caviar of the shovelnose sturgeon are considered delicacies. The flesh is often smoked, and the roe may be referred to as hackleback caviar. It has become increasingly popular as the caviar of endangered old world sturgeon species, such as the beluga, has become rarer. Poaching and overfishing presents a serious problem to the shovelnose sturgeon, because it does not breed often or easily and takes a long time to reach maturity.