Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Actinopterygii
Order: Esociformes
Family: Esocidae
Genus: Esox
Species: Esox lucius (Linnaeus, 1758) - northern pike

Intro:
It would not be remiss to describe the northern pike as the aggressive cousin of the muskellunge. Though smaller, E. lucius will hit pretty much any lure or prey that comes within the strike-zone. N. pike will strike small mammals, birds, other pike, and seemingly anything that triggers their predatory impulse.

Tips for Identifying: First the BAM then the FAD

Koaw's Guide to Telling Musky, N. Pike and Pickerel Apart <- Really great reference!

Body:
Long, streamlined body. 
Weighs up to 28.4 kg (62.6 lb) (IGFA, 2001).
Length up to 150 cm (4.9 ft), normally 40 cm/55 cm for m/f (1.3 ft/1.8 ft) (Muus, 1968).
Appearance:
Appears to have yellow jelly-beans pasted on a darker background. Fins can vary in color from green to yellowish-orange to red.
Mouth:
Jaw is slightly upturned with a flattened mouth full of sharp teeth.
Fins:
The pectoral and pelvic fins are very ventral (belly-set) on the body. The anal fin and the only dorsal fin are posterior (near the tailfin).
Area (Habitat):
Freshwater systems, usually. Circumpolar in the northern hemisphere.
Demeanor:
Aggressive.

Table of Contents - The Fishes