Like other sunfish, bluegill have very deep and highly compressed bodies. In other words, they are "tall" and "flat." They have a small mouth on a short head. The dorsal fin is continuous, with the front part spiny and the back part soft and round with a dark smudge at the base. The tail fin is slightly forked but rounded. The body is mainly olive green with yellowish underneath. Their name "bluegill" comes from the iridescent blue and purple region on the cheek and gill cover (opercle). A close look reveals six to eight olive-colored vertical bars on the sides.
Typically, adults are between 10 and 15 cm but they can grow as large as 41 cm.
This species is native to lakes and streams in the St. Lawrence, Great Lakes, and Mississippi River systems. Thus, it ranges from Quebec to northern Mexico. However, it has been introduced widely in places such as Hawaii, Africa, Asia, South America, and Europe. (Froese and Pauly, eds., 2002; Murdy, et al., 1997)
Bluegill prefer to live in lakes and slow-moving, rocky streams. They can often be found in deep beds of weeds. In Hawaii they primarily inhabit reservoirs. Though they are freshwater fish, they can tolerate some saltiness and are present in tributaries of the Chesapeake Bay. (Froese and Pauly, eds., 2002; Murdy, et al., 1997)
Males make nests in colonies with from 20 to 50 other males in shallow water less than 1 m deep. The nests are circular shallow depressions, about 20 to 30cm in diameter, in sand or fine gravel from which the male has fanned all debris.
Once his nest is made, a male waits in it and grunts to attract females. When one enters, both male and female swim in circles. Eventually they stop and touch bellies, the male in an upright posture and the female leaning at an angle. They release eggs and sperm and then start the process again by swimming in circles.
Spawning occurs when water is between 17 and 31 degrees C; in the Chesapeake Bay area it can begin when water temperatures reach 12 degrees C. Females can carry up to 50,000 eggs which take several days to hatch. After a week, young leave the nest. (Conservation Commission of Missouri, 2002; Murdy, et al., 1997; Williams, 1996)
Bluegill are most active at dawn. During the day they stay hidden under cover, and they move to shallow water to spend the night. Schools may contain 10 to 20 fish. (Williams, 1996)
Home ranges of bluegill are less than 30 square meters. (Williams, 1996)
Males change color during breeding season so it seems likely that visual cues are important either to other males or to females. Grunting is involved in courtship.
The very small mouth of this fish is an adaptation to eating small animals. Bluegills are carnivores, primarily eating invertebrates such as snails, worms, shrimp, aquatic insects, small crayfish, and zooplankton. They can also consume small fish such as minnows and plant material such as algae. Young bluegill eat worms and zooplankton, staying under cover while adults feed more in the open. (Froese and Pauly, eds., 2002; Murdy, et al., 1997; Williams, 1996)
Bluegill travel in schools and come into shallow water only at night. During the day they try to remain hidden. (Williams, 1996)
Bluegill are an important prey species for larger fish predators. They also impact insect populations by eating aquatic larvae.
Several countries where this species has been introduced report that it causes ecological problems. Bluegill overcrowd and stunt the growth of other fish and may even be responsible for causing extinction of a native fish in Panama. It is considered a pest in its introduced range.
This is an important game fish in the United States. Bluegill are fairly easy to catch and are good to eat. They are also used to stock rivers and lakes with food for largemouth bass, another important game fish.
Cynthia Sims Parr (author), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
an animal that mainly eats meat
uses smells or other chemicals to communicate
active at dawn and dusk
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
animals that have little or no ability to regulate their body temperature, body temperatures fluctuate with the temperature of their environment, often referred to as 'cold-blooded'.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
uses sight to communicate
small animals that float or drift in great numbers in fresh or salt water, especially at or near the surface. These serve as food for many larger organisms. (Compare to phytoplankton.)
Conservation Commission of Missouri, 2002. "Bluegill fishing in Missouri" (On-line). Accessed 26 March 2002 at http://www.conservation.state.mo.us/fish/fishid/bluegill/.
Froese, R., D. Pauly, eds.. 2002. "FishBase: Lepomis macrochirus" (On-line). Accessed 26 March 2002 at http://www.fishbase.org.
Murdy, E., R. Baker, J. Musick. 1997. Fishes of Chesapeake Bay. Washington, D.C.: Smithsonian Institution Press.
Williams, T. 1996. "Fish capsule report: Lepomis macrochirus" (On-line). Accessed 26 March 2002 at http://www.umich.edu/~bio440/fishcapsules96/Lepomis.html.