Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish who date back to the Triassic period some 245 to 208 million years ago. Sturgeons have been referred to as "primitive fishes" because their morphological characteristics have remained relatively unchanged since the earliest fossil record. Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a tail fin similar to those of sharks, and an elongated, spindle-like body that is smooth-skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 7–12 ft (2–3+1⁄2 m) in length. The largest sturgeon on record was a beluga female captured in the Volga estuary in 1827, measuring 7.2 m (24 ft) long and weighing 1,571 kg (3,463 lb). Most sturgeons are bottom-feeders, which migrate upstream to spawn, but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Sturgeons are primarily bottom feeders, with a diet of shellfish, crustaceans, and small fish. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non-visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini (lateral line). Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". There have been some incidents of leaping sturgeon landing in boats, and causing injuries to humans; in 2015, a 5-year-old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her. -Copy and pasted from Wikipedia Courtesy of The Bellisseria Oceanographic Institute