Physical Characteristics
Along with other members of the subclass Chondrostei, sturgeon are primarily cartilaginous, lack vertebral centra, and are partially covered with bony plates called scutes rather than scales. They also have four barbels—tactile organs that precede their toothless mouth and are dragged along often murky river bottoms. Sturgeon are distinctly and immediately recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes.
They are primarily benthic feeders. With their projecting, wedge-shaped snouts, they stir up the soft bottom, and use the barbels to detect shells, crustaceans and small fish, on which they feed. Having no teeth, they are unable to seize prey, though larger specimens can swallow very large prey items, including whole salmon.
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 (4400 lbs.) while for kaluga (H. dauricus) in the Amur River, similar lengths and over 1000 kg (2200 lb) weights have been reported. They are also probably 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.
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