New York Natural Heritage Program
Alewife Floater
Anodonta implicata Say, 1829
Bivalves
Family: Unionid Mussels (Unionidae)

State Protection: Not Listed
The species is not listed or protected by New York State.

Federal Protection: Not Listed

State Rarity Rank: S1S2
A State Rarity Rank of S1S2 means: Critically Imperiled or Imperiled in New York - Especially or very vulnerable to disappearing from New York due to rarity or other factors; typically 20 or fewer populations or locations in New York, very few individuals, very restricted range, few remaining acres (or miles of stream), and/or steep declines. More information is needed to assign a single conservation status.

Global Rarity Rank: G5
A Global Rarity Rank of G5 means: Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.


Did you know?
The shad restoration program on the Connecticut River increased the range of A. implicata upstream about 125 miles (Smith 1985).

State Ranking Justification [-]
In New York, alewife floaters are found in only the tidal Hudson River, and in the lower Delaware and Neversink Rivers, where it can be locally abundant. Historical records from elsewhere in New York appear to be misidentifications (Strayer and Jirka 1997). The species has been heavily impacted in the Hudson River estuary by the zebra mussel (Dreissena polymorpha) invasion.

Short-term Trends [-]