People often confuse the bluegill with the sunfish, because they don't see the differences in appearance that can be subtle in some cases. However, a bluegill (Lepomis macrochirus) is actually a type of sunfish (Centrarchidae family). Sunfish are a genus of freshwater fish, and one variety within the Lepomis genus is the bluegill -- the "difference" is that all bluegills are sunfish but not all sunfish are bluegills.
The Sunfish Family
The sunfish family belongs to the order Perciformes. There are 27 species, including pumpkinseed, redear, warmouth, redbreast, longear, spotted, and green, as well as rock bass, crappie and bluegill. Fish in this group may also be called perch, bream or brim. All members of the sunfish family are nest-building carnivores.
History and Names
The bluegill was first described in 1819 by Rafinesque. In the United States it is referred to by a variety of names: bream, brim, copperbelly, copper nose, sunperch, yellowbelly, bluemouth sunfish, baldface, red-breasted bream, roach and sun granny, among others.
The bluegill sunfish is identified by a black dot by the back part of the dorsal fin. The ear flap is black, while cheeks and gill covers frequently are a blue shade, The bluegill's mouth is small. Bluegills build their nests in shallow waters, often near those of largemouth bass. They are often introduced and maintained in bodies of water to serve as food for the bass, but fisherman also consider them an excellent panfish. Young or nonbreeding bluegills are lighter grey or olive in color with several darker bands. Breeding males turn darker, acquiring a purple tone on the upper portions, but they also show bright blue and orange markings. Females are duller. Bluegill bellies are white or light yellow. Adults reach lengths of 6 to 10 inches. Bluegills range throughout the United States, southern Canada and northern Mexico. They inhabit rivers, swamps, ponds and reservoirs. Their spawning season is between April and September, depending on whether they live farther south or north. They can live for five to six years.
Bluegills are density dependent, meaning that their size decreases if their numbers increase. Bluegills feed primarily on water insects, although larger specimens can leave the weedy areas for open-water feeding, where they find small zooplankton. In times of scarce food supply, bluegills may eat their own eggs. Females can lay more than 50,000 eggs; males guard first the eggs and later the fry.