Esox lucius (Northern Pike) has a broad Holarctic distribution. including northern parts of Atlantic, Arctic, Great Lakes and Mississippi Basins, from Labrador to Alaska, and Pennsylavania ans Missouri, and in Europe, as far south as Italy, and in Russia, south to the Bering Sea Basin. Northern Pike ia a popular gamefish and has been introduced to 39 states. It is a substantial predaor, reaching a maximum length of 1370 mm. It tolerates salinites up to 10 PSU, and temperatures up to 35°C, but seems to prefer cooler waters. It is established in estuaries from Maine to the Hudson River, and has been stocked from the Delaware River to the James River. It ws introdiced to the Connecitcut River in 1941 and rhe Hudson estuary by 1976. Since it is a popular gamefish, illegal introdctions have been a problem, especailly in Pacific Coast rivers, where Northern Pike are regarded as a threat to salmon and trout.