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Lepomis macrochirusBluegill(Also: Sunfish)

By Cynthia Sims Parr

Geographic Range

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)

Habitat

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 salinities up to 18% and are present in tributaries of the Chesapeake Bay. (Froese and Pauly, eds., 2002; Murdy, et al., 1997)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

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.

Young bluegill are a paler version of the adults, usually silver with a slight purple sheen. (Froese and Pauly, eds., 2002; Murdy, et al., 1997; Williams, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    2.2 (high) kg
    4.85 (high) lb
  • Range length
    41.0 (high) cm
    16.14 (high) in

Reproduction

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 (Murdy et al., 1997).

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.

A female deposits her eggs into several nests, and a male's nest may be used by several females (Williams, 1996). (Murdy, et al., 1997; Williams, 1996)

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)

  • Breeding season
    Breeding occurs from May to September (Chesapeake Bay).
  • Average number of offspring
    50000.0
  • Average time to hatching
    3.0 days
  • Average
    7.0 days
  • Average time to independence
    3 days
  • Range age at sexual or reproductive maturity (female)
    1.0 to 2.0 years
  • Range age at sexual or reproductive maturity (male)
    1.0 to 2.0 years

Males guard nests both before and after females lay eggs. Paternal care involves fanning the eggs and chasing away predators. (Murdy, et al., 1997; Williams, 1996)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male

Lifespan/Longevity

Bluegill typically live 4 to 6 years but can reach 8 to 11 years old in captivity. (Froese and Pauly, eds., 2002; Williams, 1996)

  • Range lifespan
    Status: captivity
    8.0 to 11.0 years
  • Typical lifespan
    Status: wild
    4.0 to 6.0 years

Behavior

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 Range

Home ranges of bluegill are less than 30 square meters. (Williams, 1996)

Communication and Perception

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.

Food Habits

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)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • fish
  • insects
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • zooplankton
  • Plant Foods
  • algae

Predation

Bluegill travel in schools and come into shallow water only at night. During the day they try to remain hidden. (Williams, 1996)

Ecosystem Roles

Bluegill are an important prey species for larger fish predators. They also impact insect populations by eating aquatic larvae.

Economic Importance for Humans: Positive

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. (Conservation Commission of Missouri, 2002; Williams, 1996)

Economic Importance for Humans: Negative

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. (Froese and Pauly, eds., 2002)

Conservation Status

Bluegill are abundant in their native range. Many individuals are raised in aquaculture facilities and used to stock waterways. (Conservation Commission of Missouri, 2002; Williams, 1996)

Contributors

Cynthia Sims Parr (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

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.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

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. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

ecotourism

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.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

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.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

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).

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

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.

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