Largemouth vs. Smallmouth Bass: How to Tell Them Apart

Largemouth bass (Micropterus salmoides) and smallmouth bass (Micropterus dolomieu) are both black bass, and state wildlife agencies point to the same few features to tell them apart. Check them in this order.

1. Look at the jaw

Close the fish's mouth and look at where the upper jaw ends. On a largemouth it reaches past the eye — “far beyond the rear margin of the eye,” in the Texas Parks and Wildlife Department's words. On a smallmouth, TPWD notes, the upper jaw never extends beyond the eye. The West Virginia Division of Natural Resources (WVDNR) uses the same test: largemouth have much bigger mouths, with the upper jaw reaching past the eye when closed.

2. Look along the sides

A largemouth has dark blotches that join into a horizontal stripe along the middle of each side; Alabama's Department of Conservation and Natural Resources describes it as a broad black band made of somewhat oval blotches. Smallmouth lack that dark lateral band.

Instead, WVDNR calls vertical bars a quick way to identify a smallmouth, since largemouth and spotted bass don't have them. The bars aren't always obvious: Alabama's description notes that the vertical blotches of young smallmouth typically disappear as they mature. When the bars are faint, the missing side band and the jaw settle it.

3. Use color as a hint, not proof

WVDNR describes smallmouth as usually brown or bronze, and largemouth and spotted bass as more olive or green. That's where the smallmouth's nicknames come from — TPWD lists brown bass, brownie and bronze bass — but TPWD also describes smallmouth as generally green with dark vertical bands. Since even the agencies describe their color differently, let the jaw and the markings make the call.

4. Consider where you caught it

Largemouth seek protective cover such as logs, rock ledges, vegetation and man-made structures, according to TPWD; they prefer clear, quiet water but survive well in a variety of habitats. Alabama's agency adds that they're more tolerant of murky water and slack current than the other black bass.

Smallmouth prefer fast-moving streams, WVDNR says, though they also live in lakes and reservoirs with rocky bottoms. TPWD describes their preferred habitat as large, clear lakes (over 100 acres and more than 30 feet deep) and cool, clear streams with gravel bottoms.

Quick reference

Upper jaw (mouth closed)

Largemouth: reaches past the eye. Smallmouth: doesn't extend beyond the eye.

Sides

Largemouth: dark horizontal band of blotches. Smallmouth: no dark band; vertical bars, sometimes faint.

Usual color

Largemouth: olive to green. Smallmouth: usually brown or bronze, but variable.

Typical water

Largemouth: cover-rich lakes, ponds and reservoirs. Smallmouth: clear, cool streams and rocky lakes.

What about spotted bass?

Spotted bass are a third black bass you may run into. Like largemouth, they have the dark side band and no vertical bars (WVDNR), so the band alone won't separate a spot from a largemouth; TPWD notes rows of dark spots on a spotted bass's lower sides. If you fish where spotted bass live, your state agency's identification guide is the place to check the finer points.

Why it matters on the water

Beyond bragging rights, regulations can be species specific. On Lake Fork in Texas, for example, the 16–24 inch slot limit applies to largemouth bass. Check the rules for the water you fish before you keep anything, and see our bass fishing terms for what a slot limit means.

When you're off the water, our bass fishing shirts include the American Lunker Vintage Bass Tee. And if you're wondering what makes a bass a lunker, we covered that in What Is a Lunker Bass?