For inquiries contact Karen Kellogg, Darwin Fellow, Biology Department, University of Massachusetts Amherst


The black basses (genus Micropterus) are the largest of the centrarchids, and because of their importance as game fish, they are also the most well studied. There are seven living species within this genus, although for more than a century only two species,

Smallmouth bass (Micropterus dolomieu) (Thompson, 1980)


Largemouth bass (Micropterus salmoides) (Thompson, 1980).

were recognized (Jenkins & Burkhead 1994). The native range of smallmouth bass includes much of central United States, whereas largemouth are native to central as well as southeastern states. Both species have subsequently been introduced over most of the U.S. and Canada (Page & Burr 1991). Large- and smallmouth bass were introduced as game species to Massachusetts and are now widespread and common (Hartel 1992).

Smallmouth bass:

Smallmouth bass have characteristics that are typical of carnivorous fish predators: cryptic coloration, a streamlined body, and a large mouth

Smallmouth bass in the Connecticut River (photo taken by Ed Klekowski, University of Massachusetts Amherst).

Even fingerling smallmouth exhibit a carnivorous appetite by feeding on small crustaceans, insects, and small fishes. Juveniles graduate to crayfishes and fishes, and this food preference continues in adults. Smallmouth bass attain lengths of up to 430 mm (about 17 inches) total length (Page & Burr 1991).

Smallmouth inhabit cool and warm, generally clear, large streams and rivers with gravely and rocky substrates. They are most often found in runs and pools, and a frequent succession of riffles, runs, and pools is an indicator of a good smallmouth site. Often they become the dominant species in reservoirs that impound streams with the above attributes, and are prolific in many natural northern lakes (Jenkins & Burkhead 1994).

Both sexes of smallmouth mature in about three to four years and the maximum age is fifteen. Spawning occurs in the spring, usually early May to early June depending on the latitude. Males construct nests near shore in 30-60 cm depth, on firm bottoms in slow currents and often adjacent to cover. Females have been found with 27,000 mature ova, and up to 4,000 eggs have been observed on a single male's nest. Males vigorously defend nests having eggs and remain aggressive for several days after the eggs hatch (Jenkins & Burkhead 1994).

The smallmouth bass is indeed one of the most valued and studied fish in North America. Before the turn of the century, J. A. Henshall declared that "inch for inch and pound for pound [smallmouth are] the gamest fish that swims", and this statement is still very accurate today. In fact, a magazine entitled "Smallmouth" was recently started (Jenkins & Burkhead 1994). Recommended readings for smallmouth patrons include Robbins & MacCrimmon (1974) and Stroud & Clepper (1975).

Largemouth bass:

Largemouth bass are similar in anatomy to smallmouth, although they have striped sides, an even larger mouth, and adults attain lengths of up to 650 mm (about 26 inches) total length.

A seven pound largemouth bass from Lake Hamilton, Arkansas (Sternberg, 1987)

As with smallmouth, largemouth juveniles feed on insects and small fishes, and adults feed on larger insects, larger fishes, and crayfishes. Adult largemouth, however, are even more piscivorous than smallmouth (Jenkins & Burkhead 1994).

Largemouth bass inhabit marshes, swamps, ponds, lakes, reservoirs, and creeks to large rivers. In river systems, largemouth can be found in pools and backwaters. It prefers warm, generally clear water, and is less tolerant of turbidity than other black basses (Jenkins & Burkhead 1994). Largemouth can tolerate a range of salinities and is often found in estuaries.

Maturation in largemouth is correlated with length of growing season, and ranges from maturity at age one in southern latitudes to age three or four in northern areas. Survival is typically eight to ten years, although specimens of age sixteen have been found. Spawning occurs in the spring from early May to early June. Typically, the male fans out and guards a nest, although spawning sometimes occurs on unprepared bottom. Nests are made of a variety of substrates in pools and backwaters of streams. In ponds and reservoirs, nests can be found along the shores, typically at depths of 0.3-0.6 m, but sometimes as deep as 8.2 m. Nests are located in either open areas or in association with some type of cover. Females have been observed with up to 21,000 ova (Jenkins & Burkhead 1994).

Largemouth bass fishing generates millions of dollars annually. It is the most important species of black bass in forty-two states and the most important gamefish in eleven of them. Largemouth bass was probably the first fish to be raised in culture ponds which attests to its table-fare quality and economic value (Jenkins & Burkhead 1994). Again, for those interested in additional reading, both Robbins & MacCrimmon (1974) and Stroud & Clepper (1975) provide a wealth of information.


Hartel, K. E. 1992. Non-native fishes known from Massachusetts freshwaters. Occasional

reports of the MCA Fish Department, 2:1-9.

Jenkins, R. E. and Burkhead, N. M. 1994. Freshwater fishes of Virginia. American Fisheries

Society, Bethesda, MD.

Page, L. P. and Burr, B. M. 1991. Freshwater fishes. Houghton Mifflin Co, Boston, MA.

Robbins, W. H. and MacCrimmon, H. R. 1974. The black-bass in America and overseas.

Biomanagement Research Enterprises, Sault Ste. Marie, Ontario.

Sternberg, D. 1987. Freshwater gamefish of North America. Cy DeCosse, Inc., Minnetonka, MN.

Stroud, R. H. and Clepper, H., eds. 1975. Black bass biology and management. Sport Fishing

Institute, Washington, D.C.

Thompson, P. 1980. The game fishes of New England and southeastern Canada. Down East, Camden, ME.