Smallmouth Bass

Micropterus dolomieu

Report it

If you think you have found an aquatic invasive species:

  1. take photos
  2. note:
    • the exact location (GPS coordinates)
    • the observation date
    • identifying features
  3. contact us to report it
The Smallmouth Bass (<em>Micropterus dolomieu</em>) is a member of the sunfish family.

The Smallmouth Bass (Micropterus dolomieu) is a member of the sunfish family.

Identifying features

  • a robust, laterally compressed body
  • a large, long head with dark bars that radiate back from the eyes
  • a long, blunt snout with a slightly longer lower jaw
  • two joined dorsal fins that appear as one
  • the back and top of the head range from brown to green
  • the sides are lighter than the back, more golden with golden flecks on most scales and marked by 8 to 15 pronounced to vague, thin vertical bars
  • the underside is cream to white
  • the pectoral fins are clear and the others are opaque, dark to amber with some black on rays, spines or membranes
  • the body colour is variable with size, condition and habitat. In clear water they are darker with pronounced, contrasting markings, and in turbid water they are lighter, with blurred markings.

Where it has been found

In Canada, it occurs in southern Nova Scotia, southern and western New Brunswick, southern Quebec, through Ontario at the latitude of Timmins, at the south end of Lake Winnipeg in Manitoba, in central Saskatchewan. In B.C., it has been introduced to the Columbia River system, as well as Saltspring Island and southern Vancouver Island.


The Smallmouth Bass is a warm-water fish species, usually found in moderately shallow, rocky and sandy areas of lakes and rivers and in near shoals or submerged logs. It is less often associated with dense growths of aquatic vegetation than largemouth bass. It is less often associated with dense growths of aquatic vegetation than largemouth bass. This species has been introduced intentionally for sport fishing opportunities as well as accidentally with live bait.

Ecological and economic impacts

Smallmouth Bass are considered top predators and can reduce native fish populations or alter their behaviour. They may also affect the native food web by reducing small invertebrates and fish. Once established, this species can rapidly dominate. It has been found to feed upon migrating salmon smolts and may pose a threat to salmon populations if the timing of the salmon run coincides with active bass populations.

Origins and mode of arrival

The Smallmouth Bass is a freshwater fish native to the lakes and rivers of eastern central North America.

Mode of dissemination

There are many factors favoring Smallmouth Bass invasion including the small size at which it begin piscivory, juvenile use of cover, low overlap with other predators and high fecundity combined with parental care.

Government action

Scientific research

Fisheries and Oceans Canada is studying the Smallmouth Bass population to improve its understanding of how it reacts and adapts to Canadian conditions.

For further information


  • Brown, T.G., Runciman B., Pollard, S., Grant, A.D.A., and Bradford, M.J. 2009. Biological synopsis of Smallmouth Bass (Micropterus dolomieu). Can. Manuscr. Rep. Fish. Aquat. Sci. 2887: v + 50 p.
  • Tovey, C. P., Bradford, M. J., Herborg, L. M., & Department of Fisheries and Oceans, Ottawa, ON (Canada); Canadian Science Advisory Secretariat, Ottawa, ON (Canada). (2009). Biological risk assessment for Smallmouth Bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) in British Columbia (No. 2008/075). DFO, Ottawa, ON (Canada).
Date modified: