Brook Floater
Alasmidonta varicosa

The brook floater is a freshwater mussel that can be found throughout the Chesapeake watershed.

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A mussel rests among algae-covered rocks, its soft filtering tissues visible in a partly open shell.
Brook floaters burrow into the sediment and anchor themselves to the bottom, typically only moving short distances to find the best sites for feeding and reproducing. (Photo courtesy of hunterefs/iNaturalist CC BY-NC 4.0 DEED, cropped and toned)

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Appearance

The brook floater often has a yellowish-green shell in its youth and grows into an almost black color with green rays as it ages. On the inside of its shell, it is a bluish white with pink or purple in its beak cavity. The mussel has an elliptical shape and grows to a maximum length of 3 inches.

Feeding

Mussels such as the brook floater are filter feeders, meaning they take in water and consume the bacteria, algae and plant and animal debris, leaving the water cleaner.

Predators

Mammals such as otters, muskrats and racoons prey on this mussel.

Reproduction and life cycle

The brook floater breeds in the summer, when males release sperm into the water column and females take in the sperm when filtering the water. Once the eggs are fertilized, females release the growing larvae, called glochidia, into the water. At this stage the glochidia of most freshwater mussels attach themselves to the gills of a host fish to be transported to other areas of the river or stream. Reported host fish for the brook floater include longnose dace, blacknose dace, golden shiners, pumpkinseed sunfish, slimy sculpin and yellow perch.

Did you know?

  • Brook floaters and other filter feeding mussels are important for cleaning the water in rivers and streams.

  • Brook floaters are endangered due to human activity and climate change effects.

Sources and additional information

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