Muskellunge closely resemble other esocids such as the northern pike and American pickerel in both appearance and behavior. Like the northern pike and other aggressive pikes, the body plan is typical of ambush predators with an elongated body, flat head, and dorsal, pelvic and anal fins set far back on the body. Muskellunge are typically 28–48 in (71–122 cm) long and weigh 15–36 lb (6.8–16.3 kg), though some have reached up to 6 ft (1.8 m) and almost 70 lb (32 kg). According to past references the muskellunge attains 8 feet (244 cm) in length, this however has never been confirmed and is based most likely on exaggerations. A fish with a weight of 61.25 lb (27.8 kg) was caught in November 2000 in Georgian Bay, Ontario. 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 reliable method to distinguish 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 their opercula.
Muskellunge are found in oligotrophic and mesotrophic lakes and large rivers from northern Michigan, 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. Also, a small population is found in the Broad River in South Carolina. Several North Georgia reservoirs also have healthy stocked populations of muskie. They are also found in the Red River drainage of the Hudson Bay basin. Muskie were introduced to western Saint John River in the late 1960s and have now spread to many connecting waterways in northern Maine.
They prefer clear waters where they lurk along weed edges, rock outcrops, or other structures 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 muskie continually patrols the ranges in search of available food in the appropriate conditions of water temperature.
Most of their diets consist of fish, but can also include crayfish, frogs, ducklings, snakes, muskrats, mice, other small mammals, and small birds. The mouth is large with many long, needle-like teeth. Muskies will attempt to take their prey head-first, sometimes in a single gulp. They will take prey items up to 30% of their total length. In the spring, they tend to prefer smaller bait since their metabolism is slower, while large bait are preferred in fall as preparation for winter.
Length and weight
As muskellunge grow longer they increase in weight, but the relationship between length and weight is not linear. The relationship between them can be expressed by a power-law equation:
The exponent b is close to 3.0 for all species, and c is a constant for each species. For muskellunge, b = 3.325, higher than for many common species, and c = 0.000089 pounds/inch³.
This equation implies that a 30-in (76-cm) muskellunge will weigh about 8 lb (3.6 kg), while a 40-in muskellunge will weigh about 18 lb.
Muskellunge are sometimes gregarious, forming small schools in distinct territories. They spawn in mid to late spring, somewhat later than northern pike, over shallow, vegetated areas. A rock or sand bottom is preferred for spawning so the eggs do not sink into the mud and suffocate. The males arrive first and attempt to establish dominance over a territory. Spawning may last from five to 10 days and occurs mainly at night. The eggs are negatively buoyant and slightly adhesive; they adhere to plants and the bottom of the lake. Soon afterward, they are abandoned by the adults. Those embryos which are not eaten by fish, insects, or crayfish hatch within two weeks. The larvae live on yolk until the mouth is fully developed, when they begin to feed on copepods and other zooplankton. They soon begin to prey upon fish. Juveniles generally attain a length of 12 in (30 cm) by November of their first year.
Adult muskellunge are apex predators where they occur naturally. Only humans pose a threat to an adult but juveniles are consumed by other muskies, northern pike, bass, trout, and occasionally birds of prey. The musky’s low reproductive rate and slow growth render populations highly vulnerable to overfishing. This has prompted some jurisdictions to institute artificial propagation programs in an attempt to maintain otherwise unsustainably high rates of angling effort and habitat destruction.