The Walleye (Sander vitreus) is a large (to 911 mm) predatory freshwater fish of the family Percidae and is a popular game and food fish. The Walleye is native to the Great Lakes, Arctic, and upper Mississippi basins, and has been widely introduced to 16 states in the United States by government stocking and private releases. It was an early introduction to the Susquehanna (1879), Delaware (1910), and Hudson estuaries (1893), but is rare in tidal East Coast waters. An introduction to the San Francisco Bay watershed in the 1950s was unsuccessful, but in the 1940–1950s, Walleye were stocked in Lake Roosevelt, Washington. They survived, bred and spread downstream, and were first collected in Willamette River, near Portland in 1981. They are now established in the lower Willamette and Columbia Rivers. These fish are a concern in the rivers' estuaries and reservoirs, because of their predation on migrating salmon.