Close the fish’s mouth and look where the upper jaw ends. On a largemouth bass it reaches past the rear edge of the eye; on a smallmouth bass it never does. That single mark, from the Texas Parks and Wildlife species keys, settles smallmouth vs largemouth on nearly every fish you will ever hold. The rest of the differences are just as clear once you know them: color and pattern, the notch in the dorsal fin, the water each one lives in, how big they get, and how they fight. Below: the identification table, where to find each species, how their seasons differ, and the two record fish.
A largemouth’s upper jaw reaches past the eye; a smallmouth’s stops under it. Learn that one mark and you will never mix them up again.
Identification: the table that settles it
| Feature | Largemouth bass | Smallmouth bass |
|---|---|---|
| Upper jaw | Extends well past the rear edge of the eye | Never extends beyond the eye |
| Flank pattern | Dark blotches joined into a horizontal stripe | Dark vertical bands, no horizontal stripe |
| Color | Green back, pale belly | Bronze to brown, hence “bronzeback” and “brown bass” |
| Dorsal fin | Nearly divided in two; 9 spines, 12–13 soft rays | Shallow notch, one continuous fin; 13–15 soft rays |
| Eye | Usually dark | Often red or orange-tinted |
| Scientific name | Micropterus nigricans (until 2022 M. salmoides) | Micropterus dolomieu |
| All-tackle record | 22 lb 4 oz (10.1 kg), Georgia, 1932; tied in Japan, 2009 | 11 lb 15 oz (5.4 kg), Dale Hollow Lake, 1955 |
| Common length | 16 in (41 cm), USFWS | 12–16 in (30–41 cm) in most waters |
Two more checks when the fish is small or the light is bad. The dorsal fin on a largemouth is so deeply notched that the spiny front half and the soft rear half look like two separate fins; on a smallmouth the notch is shallow and the fin reads as one. And smallmouth often carry three dark bars radiating back from the eye across the cheek, which largemouth lack.
Color alone can fool you. A largemouth from stained water can be nearly black and a smallmouth from a clear lake can look pale olive. The jaw and the stripe do not change with the water.
The largemouth, for comparison: the jaw runs past the eye and the flank carries a horizontal stripe. Illustration: Duane Raver, U.S. Fish and Wildlife Service (public domain).
Where each one lives
The two species split the country’s water between them by temperature, clarity and bottom.
Largemouth are native east of the Rockies, from the Great Lakes down the Mississippi basin to northern Mexico, and have been stocked almost everywhere else. The U.S. Fish and Wildlife Service describes their home as “clear, vegetated lakes, ponds, swamps, and the backwaters of pools, creeks and rivers.” They want cover: weed beds, laydowns, docks, flooded brush. Texas Parks and Wildlife adds that they “prefer clear quiet water, but will survive quite well in a variety of habitats,” which is why a farm pond and a muddy reservoir both hold them.
Smallmouth are native from Minnesota and southern Quebec south to the Tennessee River and west to eastern Oklahoma, and now live in most states except Florida and Louisiana. Their water is cooler and cleaner. Texas describes their preferred lakes as larger than 100 acres and deeper than 30 ft (9 m), and their streams as cool, clear and gravel-bottomed. The Wisconsin DNR puts it in one line: a rocky stream or lake environment where crayfish are abundant. A good smallmouth stream in its survey has a summer water temperature above 72 °F (22 °C), coarse rock and gravel, and pools 3–4 ft (1–1.2 m) deep.
The practical rule at the ramp: weeds and wood, think largemouth; rock, gravel and current, think smallmouth. Many lakes hold both, and there the largemouth own the weedy bays while the smallmouth own the rocky points and reefs.
Spawning and seasons
Both species spawn when the water reaches about 60 °F (16 °C), and in both the male builds and guards the nest. The differences are in the nest site and the timing.
| Largemouth | Smallmouth | |
|---|---|---|
| Spawn trigger | About 60 °F; USFWS gives 59–75 °F (15–24 °C) | About 60 °F; Wisconsin DNR gives usually 62–64 °F (17–18 °C), recorded as low as 53 °F |
| Season | February in the South to May in the North | Mostly May and June; mid-May through June in southern Wisconsin |
| Nest site | Sand, mud or gravel in 2–8 ft (0.6–2.4 m) among vegetation | Gravel bed next to a log or boulder in 3–10 ft (1–3 m); downstream of boulders in streams |
| Eggs | 2,000–43,000 | 2,000–15,000; average nest about 2,500 |
| Hatch | 5–10 days | About 10 days in the mid-50s °F, 2–3 days in the mid-70s |
| Male guards | Fry for 7–10 days | Up to a month |
Because smallmouth spawn a little later and in cooler water, a lake with both species gives you two spawns a few weeks apart. The largemouth are on beds in the back of the bays first; the smallmouth follow on the gravel flats and rocky shorelines as the main lake warms.
Through summer the largemouth stay with cover in the shallows or move to deep weed edges, while smallmouth drop onto rock humps, points and river channel edges and feed on crayfish. In fall both chase baitfish, and in winter smallmouth in particular gather in deep, slow water where they can be caught in numbers on a jig or a blade bait.
Size and the fight
Largemouth are the bigger fish. The all-tackle record is 22 lb 4 oz (10.1 kg), caught by George Perry at Montgomery Lake, Georgia, in 1932 and tied by Manabu Kurita at Lake Biwa, Japan, in 2009. A 10-pounder is a fish of a lifetime in most states. Growth in Texas runs 4–6 in (10–15 cm) in the first year, 8–12 in at two years and 16 in (41 cm) at three.
The smallmouth record is 11 lb 15 oz (5.4 kg), caught by David L. Hayes at Dale Hollow Lake on the Tennessee–Kentucky line on 9 July 1955. The fish was struck from the record book in 1996 after an affidavit alleged weight had been added, and reinstated after later documentation. A 5 lb (2.3 kg) smallmouth is a trophy almost anywhere; a 6 lb fish is news.
Ask anyone who has caught both and the answer on fighting is the same: pound for pound the smallmouth pulls harder. It jumps more, runs longer and does not give up at the boat. Largemouth make one or two heavy surges and a head-shaking jump, then come in. Part of that is water: smallmouth live in cooler, better-oxygenated water and current, and they are built for it.
Catching each one
The tackle overlaps, the presentations lean different ways.
- Largemouth: cover fishing. Texas-rigged plastics and jigs flipped to wood and grass, spinnerbaits and chatterbaits along weed edges, topwater frogs over mats in summer. Medium-heavy casting gear, 15–20 lb fluorocarbon or braid. The how to catch bass page and the best bass lures list go deeper.
- Smallmouth: rock and current, usually smaller baits. Tubes and Ned rigs dragged on gravel, drop shots on deep rock, small crankbaits and jerkbaits along points, topwater walkers on calm mornings. Spinning gear, 6–10 lb fluorocarbon, is the standard. Crayfish colors (green pumpkin, brown, orange) outfish everything else because that is what they eat.
Both species pages, largemouth bass and smallmouth bass, carry the full season tables, and the bass hub sets these two beside the spotted, Alabama and Guadalupe bass, which are more often confused with each other than with either of these.
The third fish people mistake for both
A spotted bass looks like a largemouth with a smallmouth’s jaw. It has the horizontal stripe of a largemouth, but the upper jaw stops at the rear edge of the eye, the dorsal fin is only shallowly notched, and there is a rough tooth patch on the tongue that neither largemouth nor smallmouth carry. Rows of dark spots below the lateral line give it its name. The spotted bass page shows how to separate it from the Alabama bass, which by eye you cannot.