The Largemouth Bass (Micropterus salmoides) is one of North America’s most recognizable and highly sought-after freshwater sport fish. Its common name strongly suggests a classification alongside other species known as “basses,” such as Striped Bass or White Bass. However, the true biological identity of this popular game fish often confuses anglers and the public alike. This confusion arises because the scientific classification of the Largemouth Bass places it within a group that many people associate with much smaller, disk-shaped fish. Examining the formal taxonomy of the species clarifies its place in the aquatic world.
The Taxonomic Answer
Despite its common name, the Largemouth Bass is officially a member of the sunfish family, known scientifically as Centrarchidae. This family is exclusively native to North America and contains a diverse group of freshwater ray-finned fish. The Largemouth Bass belongs to the genus Micropterus, which comprises all species commonly referred to as the “black basses.”
The classification under Centrarchidae is based on shared anatomical features. A defining characteristic is the structure of the dorsal fin, which is split into two sections: a front portion supported by hard spines and a rear portion supported by soft rays. In sunfish, these two sections are typically broadly joined, creating a single, continuous fin. All members of this family also possess three or more spines in their anal fin.
The use of the common name “bass” for Micropterus species is a historical misnomer, likely due to their predatory nature and elongated body shape. Scientifically, the family name Centrarchidae overrides this misleading common name. This places the Largemouth Bass in the same biological family as the smaller panfish, which are the typical sunfish species.
Physical Differences Between Bass and Sunfish
The main source of public confusion stems from the significant visual differences between the Largemouth Bass and classic sunfish, such as the Bluegill (Lepomis macrochirus). The most obvious distinction is body shape. The Largemouth Bass exhibits a torpedo-like, streamlined form built for active predation. In contrast, true sunfish of the genus Lepomis are deep-bodied and laterally compressed, possessing a flatter, disk-like appearance.
The mouth structure provides another clear point of differentiation, giving the Largemouth Bass its name. Its upper jaw, or maxilla, extends noticeably past the rear margin of the eye when the mouth is closed. Sunfish, by comparison, have a much smaller, terminal mouth that rarely extends past the eye.
Differences in fin structure also separate the black basses from the smaller sunfish. While all Centrarchids share the spiny and soft dorsal fin sections, the Largemouth Bass is distinguished by a deep notch that nearly separates these two parts. For many of the smaller sunfish, the two dorsal fins are connected with only a shallow groove, making the entire structure appear more like a single fin.
Other Relatives in the Centrarchidae Family
The sunfish family, Centrarchidae, encompasses a rich diversity of species beyond the Largemouth Bass and the Bluegill. The genus Micropterus alone includes other well-known game fish, such as the Smallmouth Bass (Micropterus dolomieu) and the Spotted Bass (Micropterus punctulatus). These “black basses” share the elongated body and aggressive predatory behavior of their Largemouth cousin.
Other prominent members belong to the genus Pomoxis, which includes the popular panfish known as crappie (Black Crappie and White Crappie). Crappies have a body shape intermediate between the flat sunfish and the streamlined bass. The family also contains the Rock Bass (Ambloplites rupestris) and the Flier (Centrarchus macropterus).