The Atlantic salmon has black spots on its head and body, with two or three large spots on the gill cover. The caudal fin usually does not have spots, but if there are spots, they are not in rows. The pelvic and anal fins do not have a white edge. The upper jaw reaches to below the center of the eye and may go further back in a large male. The back is brown or green, and the body is dark. (Atlantic salmon in the ocean have different coloration, being silvery on the sides and belly.) Breeding adults are bronze and brown and may have red spots. The male has a hooked lower jaw. Adults may reach 55 inches in length.
The Atlantic salmon was Introduced to Lake Michigan and other Great Lakes by humans for fishing. It was stocked in Lake Michigan until the 1990s and did not establish breeding populations. Occasionally some Atlantic salmon migrate into Lake Michigan from Lake Huron, where the species does reproduce.