Brook Floater

Alasmidonta varicosa

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The Brook Floater (Alasmidonta varicosa) is a freshwater mussel native to North America, found from Georgia (United States) to the Maritime provinces.

The species is considered a medium-sized mussel. It is distinctly kidney shaped, with one end that is inflated and rounded. The shell is smooth with growth lines forming ridges. The shell exterior varies in colour from yellow-green to brown-black and can be up to 70 mm long, 40 mm high and 30 mm wide. The shell's interior is bluish-white, sometimes with an olive or pink tint.

Similar to other freshwater mussels, the species' larvae rely on certain fish species to complete a portion of its life cycle. This means that the larvae attaches to the gills of a host fish and releases when it has grown to the appropriate size. In this way, the brook floater is dispersed into the water.

Habitat

Brook Floaters in Canada are found in rivers, streams, and lakes. They prefer watercourses with a moderate to high water flow with rocks, cobble and sand-pocket areas and may also be found in certain lakes in Nova Scotia. They are typically found clustered in sand-pocket areas behind boulders and stream banks, likely as a means of protection in high-flow velocity. In Canada, the Brook Floater is only found in New Brunswick and Nova Scotia.

Because this mussel has disappeared from approximately half of its locations in the United States, the Canadian population now represents an important global stronghold for the species.

Threats

The Brook Floater's habitat is subject to impacts such as changes in water quality resulting from excess nutrients or contaminants from forestry and agriculture runoff into watercourses, shoreline development, sedimentation in watercourses, and disturbance of habitat including barriers to migration (dams and culverts) for host fish species.

Further Information

For further information, visit the Species at Risk (SARA) Public Registry Profile.

Brook Floater

Brook Floater

Photo credit: Southeastern Anglers Association Inc.

Scientific name: Alasmidonta varicosa
SARA Status: Special Concern
COSEWIC Status: Special Concern (2009)
Region: New Brunswick, Nova Scotia

This map indicates Brook Floater distribution as described in the following paragraph

Map of the three Maritime provinces outlining the distribution of the Brook Floater. The range of this freshwater mussel is shaded in green within the provinces of New Brunswick and Nova Scotia.

Related information