Micropterus salmoidesAmerican black bass(Also: Green bass; Northern largemouth bass)

Geographic Range

Micropterus salmoides is native to eastern North America and historically ranged from southern Canada to northern Mexico, and from the Atlantic coast to the central region of the United States. Since the beginning of the twentieth century largemouth bass have been introduced successfully all over the world. (Carlander, 1977; Hubbs, 1964; Page and Burr, 1991)


Largemouth bass prefer quiet, clear waters with abundant vegetation (Iguchi and Matsuura, 2004). More specifically, they prefer shallow water that is usually no deeper than 2.5 meters, but they sometimes occupy deeper regions. Abundant vegetation is important because it allows bass to hide from their prey and provides protection against predators. Their environment is also made up of regions of clear waters where the bass' vision can be utilized to detect prey. (Hannon, 1996; Iguchi and Matsuura, 2004)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range depth
    0 to 3 m
    0.00 to 9.84 ft

Physical Description

Micropterus salmoides has a large mouth, a notch between the two dorsal fins, and a dark stripe along the side of the body (Bailey et al., 2004). This black band is seemingly made up of small oval shapes to a closer eye. Coloration is variable, but is usually a darkish green on the back and sides, fading to an off-white on the belly. The anterior dorsal fin has nine to eleven spines while the posterior dorsal fin has twelve to fourteen rays (Boschung et al., 2004). The average weight of M. salmoides is one kilogram; however, certain individuals have reached weights of over ten kilograms. Males usually do not surpass 40 cm, while females can reach up to 56 cm in length. (Bailey, et al., 2004; Boschung, et al., 2004)

  • Sexual Dimorphism
  • female larger
  • Range mass
    10 (high) kg
    22.03 (high) lb
  • Average mass
    .9 kg
    1.98 lb
  • Range length
    56 (high) cm
    22.05 (high) in


After hatching, which usually takes from three to four days, larvae form a school that moves with the close protection of a male adult. Once the individuals reach a length of almost three centimeters they leave the school to fend for themselves. At this point, the juveniles are approximately one month in age. From this point on their growth rate occurs at different speeds throughout their lives. During the first year, largemouth bass grow from 10 to 20 centimeters in length. Growth rate decreases every year, and after about five to six years there is very little change in length. (Scovell, 2005)


During the breeding season, each male prepares and builds a nest in shallow water. Nests are generally very crude in design. Once the nest is built a female swims near, and following an act of courtship, she lay her eggs in the nest. (Becker, 1983; Dewoody, et al., 2000)

Micropterus salmoides breeds in the spring. This time is determined by the temperature of the water, which usually ends up being around 60 degrees Fahrenheit. Females lay their eggs in the nests of males, and males then guard the eggs until they hatch. On average there are about 3,000 fry per nest, but as many as 6,000 have been observed (Becker, 1983). Following hatching, the schooling fry remain close to their father for at most one month (Dewoody et al., 2000). Largemouth bass females reach sexual maturity at four to five months of age, and males reach sexual maturity at three to four months of age. (Becker, 1983; Dewoody, et al., 2000)

  • Breeding interval
    Largemouth bass breed once per year
  • Breeding season
    Largemouth bass breed in the spring months (when water temperature reaches about 60 degrees Fahrenheit)
  • Range number of offspring
    6000 (high)
  • Average number of offspring
  • Range time to hatching
    3 to 4 days
  • Average time to independence
    1 months
  • Range age at sexual or reproductive maturity (female)
    4 to 5 months
  • Range age at sexual or reproductive maturity (male)
    3 to 4 months

Female largemouth bass do not invest anything more than their gametes to their offspring. Males begin their investment by constructing nests as well as defending these nests from intruders. Once the eggs hatch males remain with their broods and defend them against all predators. This continues usually for about a month. (Becker, 1983; Cooke, et al., 2001)

  • Parental Investment
  • pre-fertilization
    • protecting
      • male
  • pre-hatching/birth
    • protecting
      • male
  • pre-weaning/fledging
    • protecting
      • male


Largemouth bass live much longer in the wild than they do in captivity. The longest known lifespan of a wild largemouth bass was 23 years. The expected lifespan in the wild, though, is around 15 years. In captivity the longest lifespan recorded was 11 years, while the average age of death in captivity is around 6 years. (Becker, 1983; Boschung, et al., 2004; Carlander, 1977; Hubbs, 1964)


In the morning, largemouth bass tend to be very mobile and remain in deep waters (>2.5 m). In the afternoon, bass are sedentary and are usually found near a larger structure in deeper water. As the sun goes down largemouth bass become very mobile and move into shallow water. They remain active throughout the night with a slight decrease in mobility. Movement of bass usually correlates to movement of prey species. The home ranges of largemouth bass are relatively small and overlap with each other. Despite this, there is very little agonistic behavior between individuals and most interaction occurs during spawning. (Demers and McKinley, 1996; Sammons and Maceina, 2005)

  • Range territory size
    0.001 to .5 km^2

Home Range

Home range size for M. salmoides ranges from 0.1 to 50 ha. (Sammons and Maceina, 2005)

Communication and Perception

Largemouth bass perceive their environment through visual, auditory, tactile, and chemical means, as do most fish. (von der Emde, et al., 2004)

Food Habits

Immature Micropterus salmoides feed on zooplankton and aquatic insects. As they grow their diet shifts to crayfish and other fish species. Sunfish are the food of choice for most adult largemouth bass. (Olsen and Young, 2003)

  • Animal Foods
  • fish
  • insects
  • aquatic crustaceans
  • zooplankton


Larval and juvenile largemouth bass are prey species of yellow perch, walleye, northern pike, and muskellunge. As adults, largemouth bass can usually escape most predators. The primary predators on adult largemouth bass are humans. (Paulson and Hatch, 2002)

Ecosystem Roles

Micropterus salmoides plays an important role in the ecosystem as a top predator. Top predators are important because they maintain the populations of all of the animals below them in the food chain. Their success is not limited by any specific type of prey. Instead, they prey upon a number of species, and therefore maintain the health and viability of the ecosystem. (Olsen and Young, 2003)

Economic Importance for Humans: Positive

Largemouth bass are important game fish. They are one of the most popular fishes to catch and they continue to bring popularity to the sport of fishing. (Becker, 1983; Boschung, et al., 2004; Hubbs, 1964; Jackson, 2002; Paulson and Hatch, 2002; Scovell, 2005)

  • Positive Impacts
  • food
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

With its many introductions all over the world, M. salmoides has had many negative impacts on the native ecosystems. Two of the main impacts are the loss of biodiversity and the homogenization of ecosystems. Introduced poplulations also influence the densities of other sport fishes like trout and walleye. These issues are currently being studied and management plans are being implemented all over the world. (Jackson, 2002)

Conservation Status

Micropterus salmoides does not find itself on any of the lists of endangered species around the world. In fact the largemouth bass is one of the most successful fish, not only in its native areas, but also in freshwater areas all over the world where it has been introduced. There are certain fishing regulations that are set upon the catching of largemouth bass and these differ among regions. They involve either a limit to the number you can catch, a limit on the size that you can keep, or regulations on the season of the year in which you can catch them. (Becker, 1983; Boschung, et al., 2004; Hubbs, 1964; Jackson, 2002; Paulson and Hatch, 2002; Scovell, 2005)


Allison Poor (editor), University of Michigan-Ann Arbor.

Ryan Curtis (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.



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

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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.

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

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

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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.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

  1. active during the day, 2. lasting for one day.

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


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.


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.


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).


having the capacity to move from one place to another.


specialized for swimming

native range

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


active during the night


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

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


an animal that mainly eats fish


Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

seasonal breeding

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


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).


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


uses sight to communicate


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


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Boschung, H., R. Mayden, J. Tomelleri. 2004. Fishes of Alabama. Mobile, Al: Smithsonian Books.

Carlander, K. 1977. Handbook of Freshwater Fishery Biology. Ames: Iowa State University Press.

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Demers, E., R. McKinley. 1996. Activity Patterns of largemouth bass. Transactions of the American Fisheries Society, 125: 434-439.

Dewoody, J., D. Fletcher, D. Wilkins, W. Nelson, J. Anise. 2000. Genetic Monogamy and Biparental Care in a Externally Fertilizing Fish, the Largemouth Bass. The Royal Society, 267: 2431-2437.

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Hubbs, C. 1964. Fishes of the Great Lakes Region. Ann Arbor, MI: University of Michigan Press.

Iguchi, K., K. Matsuura. 2004. Predicting Invasions of North American Basses in Japan Using Native Range Data and a Genetic Algorithm. Transactions of the American Fisheries Society, 133: 845–854.

Jackson, D. 2002. Ecological effects of Micropterus introductions: The dark side of black bass. American Fisheries Society Symposium, 31: 221-232. Accessed December 07, 2005 at http://www.zoo.utoronto.ca/jackson/black%20bass%20symposium.pdf.

Olsen, M., B. Young. 2003. Patterns of Diet and Growth in Co-occurring Populations of Largemouth Bass and Smallmouth Bass. Transactions of the American Fisheries Society, 132: 1207-1213.

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Paulson, N., J. Hatch. 2002. "Largemouth Bass - Micropterus salmoides" (On-line). Accessed October 17, 2005 at http://www.gen.umn.edu/research/fish/fishes/largemouth_bass.html.

Sammons, S., M. Maceina. 2005. Activity Patterns of Largemouth Bass in a subtropical US Reservoir. Fisheries Management and Ecology, 12: 331-339.

Scovell, D. 2005. "Black Bass" (On-line). Accessed October 15, 2005 at http://floridafisheries.com/Fishes/bass.html.

von der Emde, G., J. Mogdans, B. Kapoor. 2004. The senses of fish : adaptations for the reception of natural stimuli. Boston: Kluwer.