Genus Anodonta main content.

Genus Anodonta

Family Unionidae



One species of Anodonta occurs in the metro area and adjacent New Jersey. The native species Anodonta implicata is known in the two metro area from two populations, until recently abundant in the Hudson and Delaware Rivers of New York. These are reported by local biologists to be in decline- presumably affected by the proliferation of the zebra mussel Dreissena polymorpha. The current status of A. implicata in the Connecticut River and in New Jersey portions of the Delaware River is unknown. A. implicata is not legally protected by the US or the states of the metro area.

Species Summaries

Species Summary

Anodonta implicata (Say, 1829)
alewife floater



size: 100mm (up to 125mm)
beak: double-looped sculpture not nodulous; umbos not elevated above the hinge line
color patterns: occasionally with fine rays; periostracum yellowish-brown, greenish-brown, or reddish-brown; nacre pink or purple, sometimes white;
shape: sub-ellipitical and elongate; ventral margin straight
shell features: a marked increasing shell thickness from posterior to anterior below the pallial line; rounded posterior ridge
teeth: absent


abundance: uncommon
status: reportedly in decline; US, NY, NJ, CT: not legally protected
conservation challenges: evidence for this species should be sought in Connecticut


N.A. distribution: Nova Scotia (Canada) west to the St. Lawrence River drainage, and south to Florida
present metro distribution: NY: upper Hudson River and upper Delaware River watersheds; NJ: Hackensack River; Lamington/Raritan River, Stony Brook, Ramapo River (lower Hudson River watershed), Lubbers Run/Musconetcong River, and Paulins Kill River (upper Delaware River watershed). Pequest River, Hayne's Creek; CT: Connecticut River and Thames River watersheds
other regional localities: CT: all Connecticut watersheds except southwest coast and Hudson River watersheds
historical localities: CT: Housatonic River watershed

Map of Mid-Atlantic seaboard with counties shown in NJ and southern NY and CT

Life History:

habitat: favors slow, sometimes fast running water, and also quiet standing water; substrate: cobble; known from stony river bottom on the Neversink River in the lower Delaware River watershed (NY) Habitat Photo
hosts: Alosa pseudoharengus (Wilson, 1811) alewife; Catostomus commersoni (Lacepede, 1803) white sucker; Gasterosteus aculeatus (Linneaus, 1758) three spine stickleback; Lepomis gibbous (Linnaeus, 1758) pumpkinseed; Morone americana (Gmelin, 1789) white perch



A. implicata

Left view
Left view
Right view
Right view
Dorsal view
Profile view
profile viewshape sub-elliptical and elongate
nacre pink; teeth absent
beak without protruberances