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Texas Invasive Species Institute

Texas Invasive Species Institute

Smallmouth Bass

Micropterus dolomieu

Class: Actinopterygii
Order: Perciformes
Family: Centrarchidae

Micropterus dolomieu

Photographer: Apple2000 Source: Wikimedia Commons Copyright: (CC0 1.0)


The smallmouth bass is green or brown with dark brown bands that run vertical, but sometimes when the fish grows older it loses the vertical bands. There are 13-15 soft rays in the dorsal fin, and the upper jaw never extends beyond the eye. Males are generally smaller than females. The males tend to range around two pounds, while females can range from three to six pounds. Smallmouth bass found in American waters tend to be larger due to the longer summers, which allow them to eat and grow for a longer period of time. Known maximum size in Texas exceeds 7.5 pounds.

Ecological Threat

The smallmouth bass has been introduced as a sport fish to the rest of the United States outside of native range. The problem with this introduction is that the smallmouth bass is out-competing other native fishes because this fish is very predatory and will even eat smaller smallmouth bass; making the smallmouth bass a serious threat to native fish populations. Also, the smallmouth bass seems to be very adaptable, which is what has allowed this fish to establish itself all over the United States, threaten fish populations everywhere. It has been documented that the smallmouth bass does significantly reduce the fish diversity in lakes that it is present, and also with their voracious appetite they reduce the availability of prey fauna for native fishes.


Spawning occurs in the spring and when water temperatures approach 60°F, males move into spawning areas. Nests are usually located near shore in lakes; downstream from boulders or some other obstruction that offers protection against strong current in streams. Mature females may contain 2000-15,000 golden yellow eggs. Males may spawn with several females on a single nest. Eggs hatch in about 10 days if water temperatures are in the mid-50's (°F), but can hatch in 2-3 days if temperatures are in the mid-70's (°F). Differently, males’ guard the nest from the time eggs are laid until fry begin to disperse, a period of up to a month. The fish fry begin to feed on zooplankton, switching to insect larvae and finally fish and crayfish as they grow.


Smallmouth bass originally ranged north into Minnesota and southern Quebec, south to the Tennessee River in Alabama and west to eastern Oklahoma and southwestern Arkansas. It is spread to new locations by fisherman catching it and releasing it to livable environments. Today there are few states, east or west of the Rocky Mountains, where populations have not become established. Florida and Louisiana are apparently free of smallmouth bass. The fish was also introduced into Texas and can be found in range of the Edwards Plateau.

Native Origin

Southern Quebec to Minnesota and over to the Tennessee River in Alabama. The western boundary is eastern Oklahoma and southwestern Arkansas making up the southern native boundary.

Current Location

U.S. Habitat: Smallmouth bass prefer large clear-water lakes and cool streams with clear water and gravel substrate. With their generalist and voracious diet the smallmouth bass is able to thrive in lakes all over the United States



U.S. Present (Exotic):  All other states not in native range except Louisiana and Florida

Texas: Eastern and Southern parts of Texas, especially around the Edwards Plateau


Since the smallmouth bass is already established in almost all of the continental United States, management would be difficult; especially since the fish is viewed as a sport fish and not an invasive in the non-native states. Introductions to other areas have not continued and can only help prevent the spread of the smallmouth bass allover every state it is present in. Education on the threat of invasive fish and encouraging angling of the smallmouth bass can also help prevent further establishment of the smallmouth bass.


Findlay, C. S., Bert, D. G., & Zheng, L. 2000. Effect of introduced piscivores on native minnow communities in Adirondack lakes. Canadian Journal of Fisheries and Aquatic Sciences, 57(3), 570-580.

Jackson, D. A. 2002. Ecological effects of Micropterus introductions: the dark side of black bass. In American Fisheries Society Symposium 31:221-232.

MacRae, P. S., & Jackson, D. A. 2001. The influence of smallmouth bass (Micropterus dolomieu) predation and habitat complexity on the structure of littoral zone fish assemblages. Canadian Journal of Fisheries and Aquatic Sciences, 58(2), 342-351.

Vander Zanden, M. J., Wilson, K. A., Casselman, J. M., & Yan, N. D. 2004. Species introductions and their impacts in North American Shield lakes. Boreal shield watersheds, 239-263.

Whittier, T. R., & Kincaid, T. M. 1999. Introduced fish in northeastern USA lakes: regional extent, dominance, and effect on native species richness. Transactions of the American Fisheries Society, 128(5):769-783.


Internet References




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