LRP - Licenses

LRP - Regulations

LRP - Permits

Recreation - Statewide

Recreation - Trapping

Recreation - Fishing

Recreation - Hunting

Env. Protection - Management

Env. Protection - Emergency

Env. Protection - Resources

To sign up for updates or to access your subscriber preferences, please enter your contact information below.

Share your observations

Share your observations of plants or non-game animals with the Natural Heritage Inventory.

Rare animals
Find rare and non-game animals.
Rare plants
Learn about plants on the Natural Heritage Working List.
Rare lichens
Discover Wisconsin's lichens.
Natural communities
Explore Wisconsin's natural communities.
Other features
Discover unique resources.
Eagle license plate

Help care for rare plants and animals by ordering an Endangered Resources plate.

Contact information
For information on Wisconsin's rare animals, contact:
Rich Staffen
Conservation Biologist

Buckhorn (Tritogonia verrucosa)



Buckhorn (Tritogonia verrucosa),a mussel listed as Threatened in Wisconsin, is found in medium to large-sized rivers, with a moderate to swift current, and clean, firm substrates. The known host fish are yellow and brown bullheads and flathead catfish.

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 Buckhorn (Tritogonia verrucosa). 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 Tritogonia verrucosa in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS2
Global RankG4G5
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: The elongate shell is brown or black, moderately large, heavy, and has many pustules. Low umbo. Beak sculpture consisting of a series of ridges continuing down the side. Pseudocardinal teeth are heavy and serrated and the lateral teeth are long, straight and striated. Ventral margin usually arched. Beak cavity deep. The nacre is white and posteriorly iridescent. The female shell has larger wing-like extensions, which the males lack. Length to 8 inches (20.3 cm).

Habitat: Inhabits fairly deep water on a sand or mud bottom. Also found in riffles and in shallow water (1-3 m) of smaller streams.

State Distribution: Occurs in the following rivers: the Mississippi, the Black, the upper and lower Wisconsin, the White, the St. Croix, the Baraboo, the Chippewa, the Eau Claire, the Pecatonica, and the Wolf.

Phenology: The breeding season lasts from April to July. The brown bullhead (Ameiurus nebulosus), yellow bullhead (Ameiurus natalis), and flathead catfish (Pylodictis olivaris) are known hosts.

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 also help to protect this species.




Photo by Lisie Kitchell, WDNR.

Last revised: Thursday, January 10, 2019