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Snuffbox (Epioblasma triquetra)



Snuffbox (Epioblasma triquetra) is both State Endangered and Federally Endangered in Wisconsin and is found in very clean water of large to medium-sized streams in the Mississippi River and Lake Michigan drainages. It is most abundant in large riffle areas. Known populations are small and local. The known fish hosts are the log-perch and banded sculpin.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Snuffbox (Epioblasma triquetra). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Documented locations of Epioblasma triquetra in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusEND
Federal Status in WisconsinLE
State RankS1
Global RankG3
Tracked by NHIY

Species guidance

Note: a species guidance document is not available at this time. Information below was compiled from publication PUB-ER-085-99 (now out-of-print).

Identification: Thick, triangular shell with a sharply defined, broadly expanded posterior slope. Epidermis yellow or yellowish-green with green rays, blotches or chevron markings. Males are triangular while females are somewhat elongate. The anterior end is rounded, and the posterior end is truncated in males, but expanded in females. The beak sculpture has three or four faint, double-looped bars. The beak cavity is fairly deep and the nacre is pearly white. 2.5 inches (6.4 cm) long.

Habitat: Inhabits medium to large, clear rivers in gravel riffles.

State Distribution: Occurs in the Embarrass, St.Croix, Wolf, and Little Wolf Rivers.

Phenology: Host fish for this species in Wisconsin is the logperch (Percina caprodes). Breeding occurs from May through July.

Management Guidelines: Habitat destruction and river pollution have resulted in mussel declines. Protection of habitat and improvements in water quality along with restriction of dredging, impoundments, sand and gravel mining, and navigational improvements would benefit this species. The development of fish runways to facilitate the movement of host species through or around dams would also help to protect the snuffbox.


No additional photos are available for Snuffbox at this time. Please consider donating a photo to the Natural Heritage Conservation program.

Last revised: Tuesday, February 19, 2019