Actinonaias ligamentina (Lamarck, 1819)
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Basis for Listing
The mucket mussel was once extremely important in the pearl button industry. Dawley (1947) reported that this species occurred in "all parts of the Mississippi drainage and in the Hudson Bay drainage", and while widely distributed in medium and large rivers, it was not present in large numbers. Specimens reported from the Red River of the North drainage are fat mucket (Lampsilis siliquoidea), a separate species. The mucket's widespread historical occurrence is supported by the distribution of dead shells found during surveys (Bright et al. 1988, 1990; Davis 1987). It is now common only in the St. Croix River and some of its tributaries (Doolittle 1988). It is apparently extirpated from the Minnesota River (Bright 1990) and many of its tributaries (Minnesota DNR, unpublished data), and occurs in only low densities in the Mississippi (M. Davis, Minnesota DNR, pers. comm.), Zumbro (Bright et al. 1988), Cannon (Davis 1987), and Otter Creek rivers. As the mucket mussel is now found alive in only a small number of drainages, it is vulnerable to habitat degradation and catastrophic events. For these reasons, the mucket was listed as a threatened species in Minnesota in 1996.
The mucket's shell is oblong, moderately thick, up to 15 cm (6 in.) long, and the posterior is sometimes bluntly pointed. The outside of the shell is yellowish to dark brown, with wide green rays often present, especially in young mussels. The beak sculpture is largely absent, and the pseudocardinal teeth are heavy and triangular. The mucket resembles the male fat mucket (Lampsilis siliquoidea) and the male plain pocketbook (L. cardium), but can be distinguished from these species by its uniformly oblong shape, heavier pseudocardinal teeth, and lack of beak sculpture.
The mucket mussel is known to inhabit medium to large rivers. Substrates that are most preferred include coarse sand and gravel (Parmalee and Bogan 1998).
Biology / Life History
Mussels are long-lived animals. Members of many species may live for several decades and in some instances, a century or more. They spend most of their lives buried in the bottom sediments of permanent water bodies, and often live in multi-species communities called mussel beds (Sietman 2003).
Conservation / Management
The continued persistence of mucket populations in Minnesota is threatened by the hydrologic alteration of streams and their watersheds; the continuing decline in habitat conditions on the Mississippi River associated with its management as a navigation canal; and water and sediment pollution from non-point and point sources. Dams, channelization, and dredging increase siltation, physically alter habitat conditions, and block the movement of fish hosts. The mucket is also being impacted by the infestation of non-native zebra mussels (Dreissena polymorpha) in the Mississippi River and its tributaries. Zebra mussels can attach themselves in large numbers to the shells of native mussels, eventually causing death by suffocation.
Conservation Efforts in Minnesota
A 10-year statewide mussel survey initiated by the Minnesota DNR in 1999 resulted in a better understanding of the mucket's ecology and current status in Minnesota. Additionally, six muckets were collected from zebra mussel infested habitats in the Mississippi River in 2000 and translocated into areas of the Mississippi River south of the Twin Cities, where habitats were devoid of zebra mussels. Efforts are also underway to propagate juveniles for restocking into areas where habitat has improved.