A muskellunge (Esox masquinongy), also known as a muskelunge, muscallonge, or maskinonge (and often abbreviated "muskie" or "musky"), is a large, relatively uncommon freshwater fish of North America. Muskellunge are the largest member of the pike family, Esocidae. The name comes from the Ojibwe word maashkinoozhe, meaning "ugly pike", by way of French masque allongé (modified from the Ojibwe word by folk etymology), "elongated mask." The French common name is masquinongé or maskinongé.
Muskellunge are known by a wide variety of trivial names including Ohio muskellunge, Great Lakes muskellunge, barred muskellunge, Ohio River pike, Allegheny River pike, jack pike, unspotted muskellunge and the Wisconsin muskellunge.
Muskellunge closely resemble other Esocids such as the northern pike and American pickerel in both appearance and behavior. Like other pikes, the body plan is typical of ambush predators with an elongate body, flat head and dorsal, pelvic and anal fins set far back on the body. Muskellunge attain lengths of 60–150 cm (2–5 ft) and weights of over 30 kg (66 lb). The fish are a light silver, brown or green with dark vertical stripes on the flank, which may tend to break up into spots. In some cases, markings may be absent altogether, especially in fish from turbid waters. This is in contrast to northern pike which have dark bodies with light markings. A sure way of distinguishing the two similar species is by counting the sensory pores on the underside of the mandible. A muskie will have seven or more per side while the northern pike never has more than six. The lobes of the caudal (tail) fin in muskellunge come to a sharper point while those of northern pike are more generally rounded. In addition, unlike pike, muskies have no scales on the lower half of the operculum.
Muskellunge are found in oligotrophic and mesotrophic lakes and large rivers from northern Wisconsin and northern Minnesota through the Great Lakes region, north into Canada, throughout most of the St Lawrence River drainage and northward throughout the upper Mississippi valley, although the species also extends as far south as Chattanooga in the Tennessee River valley. They are also found in the Red River drainage of the Hudson Bay basin. They prefer clear waters where they lurk along weed edges, rock outcrops or other structure to rest. A fish forms two distinct home ranges in summer: a shallow range and a deeper one. The shallow range is generally much smaller than the deeper range due to shallow water heating up. A musky will continually patrol the ranges in search of available food in the appropriate conditions of water temperature, pH and clarity.