Alewives are predominantly silver, except for a grayish green back. There is also a single black spot just behind the head at eye level. The common name "sawbelly" originates from the very distinctive overlapping scales along the belly that creates a saw-like keel. They have a moderately large terminal (ending at tip of snout) mouth that extends below the eye to just beyond the front edge but not to the center of the eye. The dorsal fin is positioned directly above the pelvic fins.