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

Slippershell Mussel (Alasmidonta viridis)



Slippershell Mussel (Alasmidonta viridis), listed as Threatened in Wisconsin, is found in small to medium-sized streams with flowing hard water, sand, or gravel bottoms. It is presently found only in the eastern and southern parts of Wisconsin. The known hosts are banded and mottled sculpins and johnny darter.

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 Slippershell Mussel (Alasmidonta viridis). 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 Alasmidonta viridis 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 rhomboid-shaped shells are light yellow, green or brown, sometimes with green rays. They have an armed hinge plate. Anterior and posterior ends are rounded. The beak sculpture consists of coarse loops with an uneven surface. The beak is swollen, but low. Pseudocardinal teeth are triangular, lateral teeth poorly developed. Beak cavity is moderately deep. One of the smallest mussels in the state at 46 mm (1.8 inches) long or less.

Habitat: Usually found buried in sand or fine gravel in shallow water or small streams. Also occurs along lakeshores on a sand bottom.

State Distribution: Occurs in the Embarrass, Little Suamico, Meeme, Mukwonago, Mullet, Pensaukee, Pigeon, and Wolf Rivers plus Kelly Brook. This species may yet be found to occur in rivers for which there are currently only historical records. See the species map.

Phenology: Johnny darter (Etheostoma nigrum) and mottled sculpin (Cottus bairdi) are host fish. They are probably infested from February through April.

Management Guidelines: Because it inhabits small streams and headwaters, this mussel is particularly vulnerable to siltation and pollution from runoff. Habitat protection and water quality improvements would benefit this species. Increased development along waterways in southeastern and northeastern Wisconsin is of great concern to the continued existence of this species.



Slippershell Mussel

Photo ©  Illinois Natural History Survey.

Wildlife Action Plan

Wisconsin Wildlife Action Plan graphic

Natural community (habitat) associations

The table below lists the natural communities that are associated with Slippershell Mussel. Only natural communities for which Slippershell Mussel is "high" (score=3) or "moderate" (score=2) associated are shown. See the key to association scores for complete definitions. Please see the Wildlife Action Plan to learn how this information was developed.

Natural community Score
Warmwater streams 3
Coolwater streams 2
Warmwater rivers 2

Ecological landscape associations

The table below lists the ecological landscape association scores for Slippershell Mussel. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.

This map shows the probability of Slippershell Mussel occurring in each of Wisconsin's Ecological Landscapes.  Actual scores can be found in the table to the left.

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Landscape-Community combinations of highest ecological priority*

Ecological priorities are the combinations of natural communities and ecological landscapes that provide Wisconsin's best opportunities to conserve important habitats for a given Species of Greatest Conservation Need. The 10 highest scoring combinations are considered ecological priorities and are listed below. More than 10 combinations are listed if multiple combinations tied for 10th place. For more information, please see the Wildlife Action Plan.

* Ecological priority score is a relative measure that is not meant for comparison between species. This score does not consider socio-economical factors that may dictate protection and/or management priorities differently than those determined solely by ecological analysis. Further, a low ecological priority score does not imply that management or preservation should not occur on a site if there are important reasons for doing so locally.

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Issues/threats and conservation actions

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for rare animals

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Last revised: Thursday, December 22, 2022