Twin Cities Ecological Services Field Office

Midwest Region


Twin Cities Field Office

4101 American Boulevard East
Bloomington, MN 55425
Phone: 952-252-0092
Fax: 952-646-2873
TTY: 1-800-877-8339 (Federal Relay)




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(Epioblasma triquetra)


The U.S. Fish and Wildlife Service listed the rayed bean and snuffbox mussels as endangered species.

The snuffbox is found in the St. Croix River between Minnesota and Wisconsin.

Logperch approaching a snuffbox mussel.

The logperch is a host fish for snuffbox mussels. In this photo, a logperch approached the female mussel, which then snapped shut. Oftentimes,the mussel will snap closed on a fish’s head or snout, ensuring that glochidia are released into the fish’s gills.

Photo by Dr. Chris Barnhart, Missouri State University



The snuffbox is a freshwater mussel that was historically widespread, occurring in 210 streams and lakes in 18 States and Ontario, Canada. This species has experienced a 62 percent rangewide decline. Most remaining populations are small and geographically isolated from one another, further increasing their risk of extinction.


The life cycle of the snuffbox, like most freshwater mussels, is unusual and complex. The male releases sperm in the water column that is then siphoned by the female to fertilize her eggs. Fertilized eggs develop into microscopic larvae, called glochidia, within special gill chambers. After brooding for up to seven months, the female expels mature glochidia, which then must attach to the gills or fins of a specific host fish species to complete development into juvenile mussels. If successfully attached to a host fish, glochidia mature within a few weeks. Juvenile mussels then drop off and continue to grow, if they fall onto appropriate substrate. Using fish as a host species allows the snuffbox to move upstream and populate habitats it could not reach otherwise.


News Release (Feb. 13, 2012): U.S. Fish and Wildlife Service Lists Two Freshwater Mussels as Endangered Species - - links to Regional FWS site


Federal Register Final Rule: Endangered and Threatened Wildlife and Plants; Listing the Rayed Bean and Snuffbox as Endangered (Feb. 14, 2012) - - links to Regional FWS site


Questions and Answers: Rayed Bean and Snuffbox Mussels Listed as Endangered (Feb. 2012) - - links to Regional FWS site


Fact Sheet: Snuffbox (Nov. 2010) - - links to Regional FWS site



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Last updated: February 11, 2016