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Sheepnose (Plethobasus cyphyus)



Bullhead (Plethobasus cyphyus), also commonly referred to as Sheepnose, is both State Endangered and Federally Endangered in Wisconsin. This species is found in clean water of large rivers in the Western part of the state. It prefers a stable sand substrate but has been found in mixed sand and gravel. It is always rare where it is found. The only known fish host that has been reported is the sauger.

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 Sheepnose (Plethobasus cyphyus). 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 Plethobasus cyphyus 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: Elongated heavy, brown shell with several radial knobs on disc. The anterior end is rounded and the posterior end bluntly pointed. Epidermis is yellowish-brown in smaller shells and darker brown in older shells. Pseudocardinal and lateral teeth are heavy. The nacre is white. Length to 5 inches (12.7 cm).

Habitat: Found in large rivers with a rapid current where it lives on mud, sand or gravel bottoms in water 1-2 m. deep.

State Distribution: Occurs in the upper and lower reaches of the Wisconsin River as well as the Chippewa and the Flambeau Rivers.

Phenology: Host fish for this species is the sauger (Stizostedion canadense). Mussels are gravid and/or infesting fish 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 could help to protect this species.




Photo ©  Illinois Natural History Survey.

Last revised: Tuesday, February 19, 2019