The question of whether a bluegill is the same as a sunfish is common among anglers and nature enthusiasts. This confusion stems from the use of regional common names for various fish species, which often overlap or are used interchangeably. The Bluegill is frequently called “bream,” “brim,” or “sunny,” depending on the locality. The difficulty in differentiating these fish is compounded by their similar physical appearance, as many share a compressed, disc-like body shape. Sorting out the relationship requires understanding the formal system of biological classification.
The Taxonomic Relationship
The definitive answer to the relationship between Bluegill and Sunfish lies within their scientific classification, known as taxonomy. The term “Sunfish” refers broadly to the entire family of North American freshwater fish called Centrarchidae. This family includes small, colorful species, as well as larger sport fish like Black Bass and Crappies.
The Bluegill is a single, specific species (Lepomis macrochirus). It belongs to the genus Lepomis, often called the “true sunfish” genus, which is contained within the larger Centrarchidae family. Therefore, a Bluegill is a type of Sunfish. The common term “sunfish” applies to any member of the Centrarchidae family, while “Bluegill” is reserved for this single species.
Identifying the Bluegill Species
The Bluegill possesses several distinct physical markers that set it apart from its sunfish relatives. The most reliable identifying feature is the dark, flexible flap at the posterior edge of the gill cover, known as the opercular flap or “ear flap.” This flap is entirely black on a pure Bluegill, extending to the margin without any colored edging.
Another specific trait is the dark, prominent spot located at the base of the dorsal fin. The Bluegill’s body is deep and laterally compressed, giving it a characteristic flat, round, or “slab-sided” appearance. Its mouth is notably small compared to many other sunfish.
The Bluegill often displays six to eight faint, olive-colored vertical bars along its sides. The head and cheek area frequently exhibit an iridescent blue or purple sheen, which gives the species its common name. The pectoral fins are long and pointed. During the spawning season, the male Bluegill becomes vibrant, developing a bright orange or reddish-orange breast and belly.
Common Sunfish Species Often Confused With Bluegill
Many other species within the Lepomis genus are frequently mistaken for Bluegill. The Pumpkinseed sunfish (Lepomis gibbosus) is often confused with the Bluegill because it shares the same deep body shape. However, the Pumpkinseed is distinguished by a bright orange or red spot on the posterior tip of its black opercular flap. Furthermore, the cheek and gill plate of the Pumpkinseed are marked by wavy, iridescent blue streaks.
The Green Sunfish (Lepomis cyanellus) is another common sunfish that can be easily identified by its contrasting characteristics. It has a significantly larger mouth than the Bluegill, extending back to at least the middle of the eye. The Green Sunfish’s opercular flap is black but is bordered by a pale, non-reddish margin, and the fish tends to have a thicker, less disc-like body shape compared to the flatter Bluegill.
A third species, the Redear Sunfish (Lepomis microlophus), is often called the “shellcracker” and can be differentiated by its ear flap. This species has a dark opercular flap that features a distinct red or orange margin along its edge, giving it the appearance of having a red ear. Like the Bluegill, the Redear has an elongated, pointed pectoral fin and a relatively small mouth, making the coloration of the ear flap the most reliable way to distinguish it from a pure Bluegill.