Smallmouth vs Largemouth Bass: How to Tell Them Apart

The upper jaw settles smallmouth vs largemouth bass: on a largemouth it reaches past the rear edge of the eye, on a smallmouth it never does. Close the fish’s mouth and look where the jaw ends. That one mark separates the two on nearly every fish you will ever hold. The flank backs it up: a largemouth wears a dark horizontal stripe on green, a smallmouth vertical bars on bronze.

A 20-inch smallmouth is a trophy to a fisheries biologist; a 20-inch largemouth is only “memorable.” At that length both weigh about 4.7 lb.

How do you tell a smallmouth from a largemouth?

The jaw comes first, the stripe second. The rest of the table confirms what those two have already told you.

Two more checks help 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. Up close, a smallmouth’s cheek scales are much smaller than its body scales, a key mark in the Missouri Department of Conservation’s field guide.

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 nicknames follow the same marks. The IGFA lists green bass and Oswego bass among the largemouth’s other names, and Field & Stream’s taste test calls it the bucketmouth. Missouri’s guide lists brown bass, brownie and bronzeback for the smallmouth, which anglers shorten to smallie.

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).

Are smallmouth and largemouth the same species?

No, but they are close relatives. Both are black bass, the genus Micropterus, which belongs to the sunfish family rather than to the true basses. The Missouri field guide calls the smallmouth “most closely related to the largemouth and spotted basses.” A 2022 genetic revision counted 19 black bass species. It also moved the largemouth’s name to M. nigricans and kept M. salmoides for the Florida bass.

The two differ in size inside the family. The IGFA calls the smallmouth the second-largest sunfish; only the largemouth grows bigger. The types of bass page sorts out the rest of the family and the fish that only borrow the name.

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Where does each one live, and what water does it want?

The two species split the country’s water between them by temperature, clarity and bottom.

Largemouth are native east of the Rockies, with limited populations in southeastern Canada and northeastern Mexico, by Texas Parks and Wildlife’s account. Today they can be found in every state, the IGFA notes. 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.” That 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. They now live in most states, but Texas Parks and Wildlife reports Florida and Louisiana “apparently free” of them. Their water is cooler and cleaner: lakes larger than 100 acres and deeper than 30 ft (9 m) by the Texas profile, and cool, clear, gravel-bottomed streams. Wisconsin’s DNR ties the smallmouth to a rocky stream or lake “where its favorite food, the crayfish, is abundant.”

The temperatures come from the bass water temperature chart; Florida’s FWC gives largemouth the same 65–80 °F feeding range. The stress line matters most. A smallmouth lake at 78 °F (26 °C) is a hard day, while a largemouth pond at that reading is a good one. Wisconsin’s DNR puts it plainly: “Bass like warm water and warm weather.”

Streams show what a smallmouth needs. Wisconsin DNR’s driftless team describes the streams that hold a fully developed population: summer water above 72 °F (22 °C), coarse rock and gravel, and pools 3–4 ft (1–1.2 m) deep on average.

Do smallmouth and largemouth live in the same lake?

Yes, in many lakes, and they split it between them. The rule at the ramp: weeds and wood, think largemouth; rock, gravel and current, think smallmouth. In a lake with both, the largemouth hold the weedy bays and the smallmouth the rocky points and reefs. In the clear, cool, permanent-flowing streams of the Ozarks, the Missouri field guide calls the smallmouth “the ecological replacement, or counterpart” of the largemouth and spotted bass.

They eat differently, too. Craig Bonds, a Texas Parks and Wildlife biologist, studied the black bass of Claytor Lake, Virginia, for his master’s thesis. About 75% of the smallmouth and spotted bass diet was crayfish; for the largemouth in the same lake it was about 20%. He notes the lake “did not have much vegetation,” and adds that “lakes with hydrilla have lots of crayfish, and fish go in there and feed on them.” The what bass eat page has the six diet studies side by side.

Will a largemouth eat a smallmouth?

If it fits, yes. Adult largemouth eat mostly fish, and the U.S. Fish and Wildlife Service notes that “some largemouth bass can be cannibalistic too.” In an Auburn University study at West Point Lake, the largest shad a largemouth swallowed were about half its own length.

How do their spawns differ?

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.

The smallmouth’s trigger is no lower, but its rocky main-lake water warms later than the bays, so 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. The bass spawn page has the calendar by region.

Which grows bigger: smallmouth or largemouth?

The largemouth, by nearly two to one at the top. The all-tackle record is 22 lb 4 oz (10.1 kg), caught by George Perry at Montgomery Lake, Georgia, in 1932. Manabu Kurita matched it at Lake Biwa, Japan, in 2009. Since the 2024 species split the IGFA lists his fish as the all-tackle Florida bass record, and Perry’s stands alone under largemouth.

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 July 9, 1955. The fish was struck from the record book in 1996 after an affidavit alleged weight had been added, and reinstated after later documentation. The world record smallmouth page tells that story. The length records say the same: 65 cm (25.6 in) for largemouth, 53 cm (20.9 in) for smallmouth.

What counts as a big one of each?

Most bass you catch are far below either record. A typical adult largemouth weighs 1–6 lb (0.5–2.7 kg) and a smallmouth 1–4 lb (0.5–1.8 kg), the figures on the bass hub. Field & Stream calls a 4-pounder of either species “a very nice fish in most places.”

Fisheries biologists sort bass into five length classes, and the two species have different scales. The weights are each species’ standard weight for that length, from its national equation. That is not an average: it is the 75th-percentile weight across populations, the benchmark for a well-fed fish.

The table holds the surprise of the whole comparison. At the same length the two weigh almost the same: about 4.7 lb at 20 in, and 5 lb at about 20½ in for both. The largemouth is bigger because it grows longer, not because it is built heavier. A 5 lb smallmouth is past the trophy line; a largemouth needs nearly 10 lb to reach its own.

That largemouth line is a high one. Florida’s TrophyCatch program had approved 17,166 bass of 8 lb (3.6 kg) or more by July 2026, and only 3,598 of them reached 10 lb. The largemouth bass page explains how the program counts.

The big smallmouth live in the North and in a few deep, clear reservoirs. Field & Stream names Lake Erie and the St. Lawrence River for “thousands of 5-plus-pound bronzebacks.” The smallmouth page compares the four best smallmouth waters, Dale Hollow and Mille Lacs among them.

How fast do they grow, and how old is a 5 lb smallmouth?

Largemouth grow faster where the season is long. A Texas largemouth is 4–6 in (10–15 cm) after one year, 8–12 in at two and 16 in (41 cm) at three, and lives 16 years on average.

Smallmouth grow slowly, and slower in rivers. In Wisconsin’s Namekagon River a 14-inch smallmouth is about six years old and an 18-incher ten to eleven. Those river fish level off short of 20 in, the length of a standard 5-pounder. Ohio’s DNR calls it rare for a smallmouth to pass fourteen years; the 10.15 lb (4.6 kg) Lake Erie fish of 2022 was sixteen. So a 5 lb river smallmouth is likely more than ten years old; lake fish grow faster and can get there sooner. The smallmouth bass page has the full length-at-age table.

Which fights harder?

The smallmouth has the reputation, and an agency has written it down. “Pound for pound, the smallmouth bass is the scrappiest fish of all in Wisconsin,” says the state’s DNR. Anglers mean the jumps and the runs. A largemouth is usually hooked next to weeds or wood, so the first job is to pull it clear of that cover before it buries the line.

Are smallmouth harder to catch than largemouth?

Not harder, but different. Wisconsin’s DNR says largemouth “will bite on almost anything,” and they wait in ambush beside cover you can see. Smallmouth roam more, so finding them is the work. They also hunt by sight. Field & Stream calls smallmouth “more visual feeders,” while largemouth often home in on prey by feel, sensing vibrations through the lateral line along their sides. In clear water a smallmouth gets a good look, so lighter line and smaller, finesse baits matter more. Once found they are usually more aggressive, which is why river smallmouth are the fish many anglers learn on.

How do you fish for each one?

The tackle overlaps; the presentations lean different ways. Largemouth fishing is cover fishing: Texas-rigged plastics and jigs flipped to wood and grass, spinnerbaits and chatterbaits along weed edges, frogs over mats in summer. Wisconsin’s DNR adds that a weedless bait “will often be necessary.” Smallmouth fishing is rock and current with smaller baits: tubes, the Ned rig and the drop shot, with crayfish colors to match the menu.

The year runs in the same order for both, with the smallmouth a few degrees cooler. The largemouth column is Kevin VanDam’s six-season model as Bassmaster published it. The smallmouth column is the pattern the Tennessee Wildlife Resources Agency (TWRA) describes for Dale Hollow, the lake of the record, and it transfers to any clear rocky lake.

For largemouth, a 7 ft medium-heavy casting rod with 15–20 lb fluorocarbon covers the single-hook baits. For smallmouth finesse rigs, a 7 ft medium-light spinning rod with 10–15 lb braid to a 6–8 lb fluorocarbon leader is the usual outfit. The how to catch bass page builds one outfit for both, and the best bass lures list goes deeper.

Which is better to eat?

Neither, by much. Will Brantley, writing in Field & Stream, ate both and calls the fillets “pretty much indistinguishable.” The water and the handling matter more than the species. Hank Shaw’s rule in Outdoor Life is to ice a bass as soon as it is dead, or the meat turns “to mush.” He also wants his bass from cold water, which gives firmer meat. That is the smallmouth’s home water, so it gets a head start.

Most bass of both species go back anyway. Catch and release became the bass custom after B.A.S.S. launched its Don’t Kill Your Catch campaign for tournament anglers in 1972, not because the fish taste bad. The is bass good to eat page has the mercury advice and the history.

Which should you fish for?

Neither is better; the water you can reach decides. Five questions settle it:

1. What water is near you? A pond, a weedy lake or a warm reservoir holds largemouth. A clear lake over rock or a cool gravel stream holds smallmouth. Many lakes hold both, in different parts.
2. How warm is it? Largemouth keep feeding to about 85 °F (29 °C). Smallmouth slow down above 75 °F (24 °C), so on a hot afternoon the largemouth is the easier fish.
3. What tackle do you own? A medium-heavy casting rod and 15–20 lb line suit largemouth in cover. A light spinning rod with a 6–8 lb leader suits smallmouth in clear water.
4. Do you want size or fight? For a 10-pounder, the largemouth is the realistic target: no smallmouth over 10 lb has entered the IGFA book since 1986. For the hardest pull per pound, Wisconsin’s DNR has already voted for the smallmouth.
5. Are you keeping one for dinner? Either works. Keep a small one from cool water and ice it at once.

Can smallmouth and largemouth crossbreed?

Yes, though in the wild it is rare. Dr. William Childers of the Illinois Natural History Survey crossed them in the 1960s: largemouth eggs fertilized with smallmouth milt produced live young. He named the hybrids meanmouths after a school of them attacked a swimmer. His hybrids were not sterile; they reproduced with each other and with both parents. A 2010 genetic study in Copeia confirmed the cross in the wild, from a smallmouth male guarding eggs from females of both species.

The record book keeps the two crosses apart. The IGFA’s “smallmouth x largemouth” record is an 11 lb 1 oz (5.02 kg) fish caught by Brady M. Stanford at O.H. Ivie Reservoir, Texas, on February 22, 2022. Its “meanmouth” category is a different cross, smallmouth × spotted bass. A largemouth × smallmouth hybrid tends to show a jaw that lines up with the back of the eye and a dorsal fin almost joined, halfway between the two, Wired2Fish notes; only a genetic test confirms one. The meanmouth bass page has all four hybrid records.

Which bass looks like 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. Its dorsal fin is only shallowly notched, and it carries a rough tooth patch on the tongue, which Virginia’s wildlife agency calls “rare in Largemouth Bass.” 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. All five black bass you are likely to meet are side by side on the bass hub.

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The Water Temperature Fishing Chart. Take one water temperature reading, find it on the chart, and see which of 26 freshwater fish are spawning, feeding hard or slowing down.

• Where bass, crappie, bluegill and walleye sit, and what to throw. Trout: the reading where you stop.
• Why a 3 ft drop beats a cold front, and what to throw each day of the front
• The three thermometer mistakes that make a reading lie

The chart's numbers come from state fish and wildlife agencies and fisheries research: 61 sources, each listed on the site.

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