brook floater
FWS Focus

Overview

Characteristics
Overview

The brook floater is a small stream-dwelling mussel native to 16 states in the eastern U.S., the District of Columbia, and two Canadian provinces. Brook floaters depend on streams with clean, flowing water and substrate that they can anchor into while filter feeding, and they are vulnerable to pollution and climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's…

Learn more about climate change
. A coordinated effort is underway across the range of the brook floater to standardize data collection on the species and develop the most effective strategies for restoration. 

In 2016, the Massachusetts Division of Fisheries and Wildlife received a State Wildlife Grant from the U.S. Fish and Wildlife Service to coordinate brook-floater conservation efforts across the region in partnership with Maine, New Hampshire, New York, Virginia, and the U.S. Geological Survey’s Massachusetts Cooperative Fish and Wildlife Research Unit.

The grant led to the formation of a multi-partner brook floater working group, standard survey protocols, and advances in propagation techniques. Propagated brook floater are now stocked in some rivers within its range and stocking is under consideration by managers in other states.

The species is currently found in 14 of the 16 states where it was found historically, and 15 watersheds in New Brunswick and Nova Scotia, Canada. The largest brook floater population is found at the foot of its range, along the Georgia-South Carolina state line in the Chattooga River, a river largely protected by national forests. 

Scientific Name

Alasmidonta varicosa
Common Name
brook floater
FWS Category
Clams
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Habitat

Characteristics
Habitat

The brook floater depends on streams with clean, flowing water and substrate that they can anchor into while filter feeding. Evidence suggests they are sensitive to high water flows that can dislodge them from stream bottoms. Their habitat is vulnerable to pollution, development, invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

Learn more about invasive species
, and changes in temperature and precipitation patterns resulting from climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's…

Learn more about climate change
.

Strayer DL and AR Fetterman. 1999. Changes in the distribution of freshwater mussels (Unionidae) in the Upper Susquehanna River Basin, 1955-65 to 1996-97. American Midland Naturalist 142:328-339.

River or Stream
Characteristic category

Physical Characteristics

Characteristics
Color & Pattern

Brook floaters have yellowish or greenish shells. As juveniles, the shells are covered with dark green rays. The outer surface becomes brownish with rays partially obscured or almost black in adults. The inner shell surface is a bluish white, often with salmon, pink or purple in the beak cavity.

Freshwater Mussels and the Connecticut River Watershed, Connecticut River Watershed Council

Size & Shape

The brook floater has an elliptical-shaped shell that grows to a maximum length of about 3 inches, or 75mm – no bigger than a credit card.

 

Physical Characteristics

The brook floater depends on streams with clean, flowing water and substrate that they can anchor into while filter feeding. Their habitat is vulnerable to pollution, development, invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

Learn more about invasive species
, and changes in temperature and precipitation patterns resulting from climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's…

Learn more about climate change
.

Characteristic category

Lifecycle

Characteristics
Lifecycle

The brook floater is a long-term brooder, which means it undergoes fertilization in the summer and holds onto its larvae -- called glochidia -- until the following spring or summer. After the glochidia are released, they use hook-like appendages to latch onto the gills, body, or fins of fish. The glochidia take in nutrients from their unassuming hosts until they metamorphize into juvenile mussels, and drop off onto the stream bottom to mature. 

Characteristic category

Behavior

Characteristics
Behavior

When removed from the water, they have a peculiar habit of gaping their shell open to expose their orange “foot,” giving the appearance that they are sticking out their tongue.

Geography

Characteristics
Range

The brook floater is found along the North Atlantic coast from eastern Canada to the Savannah River basin in South Carolina and Georgia.

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Timeline

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