How to Identify a Smallmouth Bass (Micropterus dolomieu)

• Body shape: A large, elongated fish with a moderately large mouth, smaller than that of the largemouth.
• Jaw length: In adults, the upper jaw reaches to about the rear margin of the eye, not beyond it.
• Dorsal fin: The two dorsal fins are connected (with only a shallow notch between them).
• Body markings: Bronze to brownish-green, with dark vertical bars on the sides; three dark lines radiate outward from the eye.
• Absence of markings: There is no dark horizontal stripe, and it lacks rows of dark spots.

The smallmouth's upper jaw does not extend beyond the back of the eye; in the largemouth bass, the upper jaw extends far behind the back of the eye. See the Largemouth Bass page for its full mark list.

The smallmouth has vertical bars on its sides and no rows of spots; the spotted bass has rows of dark spots forming horizontal streaks on the lower sides. See the Spotted Bass page for its full mark list.

A freshwater fish that thrives in clear streams with silt-free rock or gravel bottoms, near riffles but not in the main current. Native to the upper and middle Mississippi River drainage.

Lay the fish flat on its side in even light and photograph the whole body first, then the details below. Get a close, sharp frame of the head: mouth, jaw length and any barbels. Raise the dorsal and anal fins fully; ray counts and fin edges only read when the fin is spread. Shoot the side of the body before the fish dries; spots and stripes fade fast out of water. The app reads the photo and names the likely species; use the marks on this page to confirm it.

Size and daily limits for this species differ by state and by water, and some waters are catch-and-release only. Check the current regulations for where you are fishing before keeping any fish; if you are unsure of the species, release it.