The lake sturgeon (Acipenser fulvescens), also known as the rock sturgeon, is a North American temperate freshwater fish, one of about 25 species of sturgeon. Like other sturgeons, this species is an evolutionarily ancient bottom feeder with a partly cartilaginous skeleton, an overall streamlined shape and skin bearing rows of bony plates on its sides and back, resembling an armored torpedo. The fish uses its elongated, spade-like snout to stir up the substrate and sediments on the beds of rivers and lakes while feeding. The lake sturgeon has four purely sensory organs that dangle near its mouth. These organs, called barbels, help the sturgeon to locate bottom-dwelling prey. Lake sturgeons can grow to a relatively large size, topping 7. 25 ft (2. 2 m) long and weighing over 240 lb (108 kg).