Sturgeon

Sturgeon is the common name for 27 species of fish in the family Acipenseridae.
Evolution.
Sturgeons have been referred to as "living fossils" or "primitive fish" because their features have not changed very much since their earliest fossil record.
Habitat.
Sturgeon range from subtropical to subarctic waters in North America and Eurasia. In North America, they range along the Atlantic coast from the Gulf of Mexico to Newfoundland. They used to be found throughout the Mississippi River, the Great Lakes and the Hudson River.
Throughout this extensive range, almost all species are highly threatened or vulnerable to extinction due to a combination of habitat destruction, overfishing, and pollution.
In the last century, this large fish was often regarded as a nuisance because it often became entangled in and caused commercial fishing nets to become ripped. Only much later did the sturgeon become prized for its meat, eggs (caviar) and oil. Gelatin from the inner lining of its air bladder was used to make isinglass--a substance used as a clarifying agent in jellies, glues and in the isinglass windows of carriages and early cars. Nowadays, the lake sturgeon's dark form can be sometimes be discerned in reedy shallows or near river mouths.