Cisco Identification Guide

Key identification features

• Slender, elongated, laterally compressed body
• Terminal to slightly upturned mouth with the lower jaw often projecting a bit past the upper jaw
• Large eye relative to head size
• Dark bluish-green to steel-gray back fading sharply to silver sides and a white belly
• Deeply forked tail and a single small adipose fin

Common look-alikes

• Lake whitefish: deeper-bodied with a subterminal, downturned mouth built for bottom feeding rather than open-water feeding
• Bloater: a close relative found in deeper water, generally with an even larger eye and slimmer profile adapted to low light
• Rainbow smelt: similarly silvery and slender, but smelt have a large mouth with prominent teeth and lack the small adipose fin typical of a cisco

Where you'll see one

Ciscoes are pelagic schooling fish found in the open, deep, cold waters of the Great Lakes and many boreal lakes across Canada and the northern United States, where they feed on plankton well off the bottom. Large schools often suspend at mid-depth over open water rather than hugging shorelines or structure.