The Bluegill (Lepomis macrochirus) is a species of freshwater fish. It is a member of the sunfish family (family Centrarchidae) of order Perciformes. It is native to a wide area of North America, from Québec to northern Mexico, and has been widely transplanted to stock game fish for anglers. It is commonly fished in Minnesota, but it is the state fish of the U.S. state of Illinois.

Of typical sunfish body shape, the Bluegill’s most notable feature is the blue or black “ear”, actually an extension of the gill cover called the opercular flap. Its name, however, comes from the bright blue edging visible on its gill rakers. It can be distinguished from similar species by the (not always pronounced) vertical bars along its flanks. The Bluegill grows to a maximum overall length of approximately 16 in (40 cm).

Bluegills are popular game fish, caught with live bait, flies or other lures, chiefly at dawn and dusk. They are noted for seeking out underwater vegetation for cover; their natural diet consists largely of small invertebrates and very small fish. The Bluegill is a schooling fish with schools of 20″“30 individuals. These fish spawn in June in nests in the shallows. During this period males assume a very bold coloration, as they are guarding their nests. An interesting piece of their biology is that some males assume the coloration of the female fish so that the nest guarding males won’t show aggression towards them. Then these “sneaker” males enter nests and spawn. Because of their size and the method of cooking them, Bluegills are often called panfish. Bluegills are also commonly referred to as bream. They are widely considered one of the tastiest of the panfish. Bluegills are excellent fish to teach children angling. They hit hard for their size (making it easy to tell when the angler has one on the line) and fight hard, but not so hard as to make them too difficult for a small child to land.

In some locations where it has been transplanted, it is considered a pest; trade in the species is prohibited in Germany and Japan.

The specific epithet, macrochirus, derives from the Greek μακρός (long) and χείρ (hand).

Role in Human Water Supply

The cities of San Francisco, New York, and Washington have utilized Bluegills for monitoring their water supply from non-biological toxicants such as pesticides, mercury, cyanide, heavy metals, fuel spills and phosphates. Fish cough by flexing their gills to expel unwelcome particles, like grains of sand, from their breathing passages. Sensitive instruments listen for unusual amounts of coughing. The American Army has given this device the commercial name “1090 Intelligent Aquatic BioMonitoring System”.