Any of about 20 species (family Acipenseridae) of large, primitive fishes that live mainly in southern Russia, Ukraine, and North America. Most species live in the sea and ascend rivers to spawn; a few live permanently in fresh water. Four tactile barbels near the toothless mouth detect invertebrates and small fishes on the mud bottom. Sturgeon flesh and eggs, or roe (caviar), are sold for food. The swim bladder is used in isinglass, a gelatin. The Baltic sturgeon (Acipenser sturio) and several other species are endangered. The Atlantic sturgeon (A. oxyrhynchus), however, is common along the eastern coast of North America and generally is about 10 ft (3 m) long and weighs about 500 lb (225 kg). See alsobeluga.