Smallmouth Bass

Micropterus dolomieu

Learn about Smallmouth Bass, including its identifying features, habitat, spread, impacts and our response.

The Smallmouth Bass (Micropterus dolomieu) is a freshwater fish and a member of the sunfish family. They are a top predator that eat a wide range of prey, including insects, crayfishes, fishes, tadpoles, frogs and plant material. They can be invasive when introduced to new lakes and rivers.

Identifying features

You can identify Smallmouth Bass by their:

upper jaw does not extend past the eye
dark bars radiating back from the eye and one bar radiates from the eye to the snout
eye that is sometimes red in colour
laterally compressed body (more than the Largemouth Bass)
sides that have golden flecks on most scales
sides that have vertical bars that are sometimes broken (ranging from very visible to slightly visible)
joined dorsal fins that appear as one (unlike the Largemouth Bass, which has a more obvious separation between dorsal fins)

The body colour of Smallmouth Bass changes with size, condition and habitat. It will be darker with pronounced, contrasting markings in clear water and lighter, with blurry markings in cloudy water.

Where is it invasive?

In Canada, Smallmouth Bass has been confirmed as introduced in:

southern British Columbia, including:

many lakes in southern Vancouver Island
Saltspring Island
Columbia River system
small number of systems in the Fraser drainage
most of the lowland Okanagan lakes
in the Kootenays

south-eastern Saskatchewan
the south end of Lake Winnipeg in Manitoba
Ontario, inland lakes as far north as Timmins
southern Quebec
southern and western New Brunswick
southern Nova Scotia

Distribution

Smallmouth Bass is native to the fresh waters of eastern-central North America. The original Canadian distribution of Smallmouth Bass was restricted to the Great Lakes – St Lawrence system with the exception of Lake Superior.

Historically, introductions of Smallmouth Bass to other parts of Canada for recreational fishing were allowed until the late 1900s. Smallmouth Bass is a popular sport fish, but can be invasive when introduced to new lakes and rivers. Recent spread is a result of accidental introductions when used as live bait and unauthorized transfers between waterbodies for recreational fishing.

In some areas, Smallmouth Bass is considered established and is managed for recreational fishing. With the appropriate fishing licences, it is legal to fish for Smallmouth Bass in these areas. Outside of these areas, Smallmouth Bass are considered invasive. Each province has different management approaches. For detailed information on the status of Smallmouth Bass in your region, contact provincial authorities or your local DFO office.

Habitat

Smallmouth Bass prefer cool water and are usually found near shoals or submerged logs and in moderately shallow, rocky and sandy areas.

It is seldom found in dense aquatic vegetation (which are favoured by Largemouth Bass). Therefore, the habitats of Largemouth and Smallmouth Bass don’t often overlap, even if both species inhabit the same lake.

Impacts

Smallmouth Bass is a top predator that can dramatically change the native food web after introduction to a new waterbody. When established in new areas Smallmouth Bass can:

change the food web by reducing the amount of prey available to native fish
reduce native fish populations or cause them to alter their behaviour

There are many factors that make Smallmouth Bass a successful invader, including their:

ability to produce many offspring
low habitat overlap with other predators
small size at which they begin eating other fish

Management

Management of Smallmouth Bass in Canada is complex. In parts of the country it is native, in other parts it is well established and managed for sport fisheries and in other parts it is invasive and managed as such. The boundaries between these different management strategies are not always clearly defined and in most provinces or regions this species is managed on a case-by-case basis.

In many provinces/regions, inland waters are delegated to the provinces, meaning the provinces take the leadership role in managing Smallmouth Bass (either as native, invasive or sportfish), with the extent of DFO involvement varying across regions, depending on partnership agreements made between the different levels of government.