Alewife Identification Guide

Key identification features

• Moderately deep, laterally compressed body with a grayish-green back and bright silver sides
• One prominent dark spot just behind the gill cover, usually not followed by a trailing row of additional spots
• Notably large eye, with the eye diameter roughly equal to or greater than the snout length
• Deeply forked tail fin and a row of scutes forming a keel along the belly
• Adults typically 20-30 cm, smaller and slimmer overall than American shad

Common look-alikes

• Blueback herring — very similar but has a darker, steel-blue to blue-black back and a smaller eye relative to snout length
• American shad — much larger, deeper-bodied, and usually shows a row of small spots trailing behind the main shoulder spot
• Gizzard shad — has a long whip-like filament trailing from the last dorsal fin ray, absent in alewife

Where you'll see one

Alewife are anadromous along the Atlantic coast of North America, migrating each spring from coastal waters into freshwater rivers, lakes, and ponds to spawn, with self-sustaining landlocked populations also established in the Great Lakes and other inland lakes.