Many sunfishes are important game fish, but few are as popular among North American anglers as largemouth bass and smallmouth bass are. While both reach respectable sizes and pack plenty of fight once hooked, they exhibit several key biological and behavioral differences. Understanding these differences can help you fish for them with more confidence.
The most effective way to distinguish between largemouth bass and smallmouth bass is by examining the jaw and mouth. As their common name suggests, largemouth bass have gigantic mouths when compared to other members of the genus, such as smallmouth bass. Observe the fish from the side while its mouth is closed – if the corner of the fish’s mouth extends beyond the rear of the eye, it is a largemouth bass. The corner of a smallmouth bass’s mouth only extends to the middle of the eye.
Largemouth bass reach much larger sizes than their smallmouth kin. Smallmouth bass average between 12 and 15 inches in length, while largemouth bass average closer to 18 inches in length. The world record largemouth bass tipped the scales at over 22 pounds, while the largest smallmouth caught weighed only about 12 pounds.
While both species are subject to regional and individual variation, smallmouth bass are usually bronze to brown in color, with dark vertical bars on their sides. By contrast, largemouth bass are olive to dark green and have a distinct lateral stripe that travels down their sides. Bass do exhibit a small degree of color-changing ability, so it is wise to consider other factors when making an identification.
Both smallmouth and largemouth bass are opportunistic eaters that consume a very wide range of prey. Largemouth bass feed primarily on fish, but they will take crustaceans, reptiles, amphibians and insects if the opportunity presents itself. Researchers have even found terrestrial species, such as chipmunks, red-winged blackbirds and meadow voles in the stomachs of largemouth bass. Being smaller than their cousins, smallmouth bass do not often prey upon large, terrestrial prey; instead, they concentrate on fish. However, they will consume crayfish if available. The two species also exhibit differences in hunting behavior, as largemouth bass tend to stay near the surface for extended periods when hunting floating prey, while smallmouth bass tend to remain deeper, and surface quickly before returning to the depths.
Both species are broad habitat generalists, but they do exhibit a few tendencies. Largemouth bass are commonly associated with slow-moving rivers, ponds and lakes that feature abundant vegetation, while smallmouth bass are more likely to inhabit areas with rapid water flow and gravel-covered riverbeds. In fact, when they must compete with their large-mouthed cousins, smallmouth bass fail to persist in areas with muddy bottoms.
- University of Massachusetts, Amherst: Small- and Largemouth Bass
- University of Notre Dame: Terrestrial Prey Items in the Diet of Largemouth Bass (Micropterus Salmoides) in a Small North Temperate Lake
- Fish Base: Family Centrarchidae - Sunfishes
- FishingInfo.com: Smallmouth Bass
- Texas A&M University: Predatory Behavior and Competition Among Laboratory-Housed Largemouth and Smallmouth Bass
- Minnesota Department of Natural Resources: Smallmouth Versus Largemouth Bass - Identification
- Texas Parks and Wildlife: Bass Identification
- Bass Master: David Hayes' World Record Smallmouth Bass
- Florida Museum of Natural History: Largemouth Bass
- Ohio Department of Natural Resources: Smallmouth Bass
- Maurizio Bonora/iStock/Getty Images