New York Natural Heritage Program
Brook Floater
Alasmidonta varicosa (Lamarck, 1819)
Bivalves
A. varicosa walking E. Gordon
Family: Unionid Mussels (Unionidae)

State Protection: Threatened
A native species likely to become an endangered species within the foreseeable future in New York (includes any species listed as federally Threatened by the United States). It is illegal to take, import, transport, possess, or sell an animal listed as Threatened, or its parts, without a permit from NYSDEC. 1) Any native species likely to become an endangered species within the foreseeable future in New York. 2) Any species listed as threatened by the U.S. Department of the Interior.

Federal Protection: Not Listed

State Rarity Rank: S1
A State Rarity Rank of S1 means: Typically 5 or fewer occurrences, very few remaining individuals, acres, or miles of stream, or some factor of its biology makes it especially vulnerable in New York State.

Global Rarity Rank: G3
A Global Rarity Rank of G3 means: Either rare and local throughout its range (21 to 100 occurrences), or found locally (even abundantly at some of its locations) in a restricted range (e.g. a physiographic region), or vulnerable to extinction throughout its range because of other factors.


Did you know?
The brook floater has virtually disappeared from the Susquehanna River basin since the mid-1950's (Strayer and Fetterman 1999).

State Ranking Justification [-]
Formerly widespread in southeastern New York, this species has disappeared from many sites since the 1950's and is now extremely rare in the state. Populations in the Housatonic and Passaic basins have apparently disappeared and surveys of nearly a dozen historical populations throughout the Susquehanna River watershed in 1991 turned up only 1 living animal. Populations in the Shawangunk Kill and Delaware River basins (Lellis 2001) are sparse and limited in extent. Only the Neversink River population currently appears healthy although it also apparently declined by an estimated 38,000 individuals during the mid 1990's (Strayer and Jirka 1997).

Short-term Trends [-]

Long-term Trends [-]