The northern pike (Esox lucius), known simply as a pike in Britain, Ireland, and the USA, or as jackfish in Canada), is a popular sporting and food fish that inhabits freshwaters around the northern hemisphere, and are found in brackish waters of the Baltic Sea. Northern pike in Europe can grow up to about 25 kg and 150 cm long; females are generally larger than males. They become sexually mature at 3-4 years of age, and live between 10-12 years. Solitary and territorial, these fish ambush predators. As young fish they feed on small invertebrates, and as they grow older their broad diet grows to include amphibians and fish of all sorts (including their own kind), and even small mammals and birds. Pike has been used to stock waterways (often illegally) in many areas, and has impacted native fish populations and fish communities in negative ways. In Alaska, Colorado, Montana and Maine, E. lucius have been documented as threatening stickleback and native salmonids. The northern pike can hybridize with the closely related muskellunge E. masquinongy, and in some areas E. lucius threaten native muskellunge populations.

( Department of Natural Resources; Fuller 2012; Wikipedia 2012)