One of the most interesting fish found in the Mississippi River system is also one of the most unusual - the paddlefish. Like its closest living relative, the sturgeon, the paddlefish is an ancient fish that has been swimming the rivers and tributaries of the Mississippi River system for thousands of years. The paddlefish has a cartilaginous skeleton, with only the jaw having hard bone. The paddlefish is a filter feeder and swims along near the surface of the water, opening its mouth wide and using its gill rakers to filter out tiny plankton. From time to time it closes its mouth to swallow. The paddle, which is covered with taste buds and numerous nerve endings, helps locate concentrations of plankton. The paddle is also believed to act as a stabilizer and to reduce drag when the paddlefish has its mouth open for feeding. Prized for its excellent white meat and valuable roe, the paddlefish has been severely over fished.