A sturgeon is a primitive type of fish from the Acipenseridae family. The term “sturgeon” actually incorporates 25 different species of fish, all identified by the bone plates on their heads and bodies and by the barbels that dangle from around their toothless mouths. The evolution of sturgeons can be traced as far back as the dinosaur era. Species of sturgeons are most commonly found in North America and Russia.
The sturgeon's bony plates, or scutes, serve as protection and replace the scales present on most fish. Their barbels, which look like whiskers, help them find food. The barbels are very sensitive, and sturgeons will drag them along the ocean floor or river bed to locate food sources. The sturgeon's diet consists mostly of small fish and invertebrates.
The term "sturgeon" incorporates more than two dozen species of fish, so their size and weight vary. For example, at its largest, a shortnose sturgeon measures about 4.7 feet (1.4 m) and weighs about 51 pounds (23 kg). The largest freshwater fish in North America, the white sturgeon, can be 20 feet (6 m) long and weigh about 1,500 pounds (680 kg). Still larger, the beluga, found in the Caspian and Black seas, measures about 24.6 feet (7.5 m) and can weigh 2,900 pounds (1,315 kg).
Sturgeons live in temperate waters. Some are restricted to freshwater areas, but many live at sea or near estuaries and enter rivers only to spawn. For many species, the spawning location is determined by the speed of the river. For example, shortnose sturgeons live primarily in areas where the water flow is slow, but they travel to faster-moving rivers to spawn.
Some sturgeons can live more than 300 years, although like their size and weight, their life cycles vary. White sturgeons generally live more than 100 years, reaching maturity between ages 15 to 25 and spawning every four to 11 years. By contrast, shortnose sturgeons have a much shorter life span. Males live only about 30 years, though the females can live as long as 67 years, spawning every three years.
Sturgeons are very useful to humans and have thus been over-fished to the extent that some species, such as the shortnose, have been placed on the endangered species list. To combat this decline, fishing is limited in some areas, and many species are also breed in fisheries. Sturgeon flesh, eggs and swim bladders are all used by humans. The flesh is good to eat, and the eggs are used for caviar. Swim bladders are made into a gelatin called isinglass, which is used in industry.