|Scientific Name:||Alasmidonta marginata Say, 1818|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Woolnough, D. & Bogan, A.E.|
|Reviewer(s):||Ormes, M., Seddon, M.B. & Lopes-Lima , M.|
|Contributor(s):||Cordeiro, J. & Bogan, A.E.|
This species is listed as Least Concern because it is wide-ranging and is considered to be secure in the main part of its range. Whilst there is evidence of localized declines, it is currently suspected that the general decline lies between 15 and 20% of global population, and there is insufficient data to suggest this meets the 30% decline threshold over the last three generations.
However, the species is never abundant at any particular site, and as such it remains a candidate for Threatened species and as such it should be monitored closely for future declines.
|Previously published Red List assessments:|
|Range Description:||This species ranges in the north from Ontario, Canada (Great Lakes and St. Lawrence drainage) south to Alabama (Tennessee drainage) and on the east from New York (Susquehanna and St. Lawrence drainages) to Virginia (Ohio drainage) and on the west from eastern North Dakota to Arkansas, with the centre of abundance being in Ohio, Indiana and Illinois (Parmalee and Bogan 1998, Burch 1989, Clarke 1981). This species was previously thought to be extirpated in Alabama (McGregor and Haag 2004) but subsequently rediscovered in the Paint Rock River (Williams et al. 2008).|
The Atlantic slope form (var. susquehannae) is found in the Susquehanna basin of Pennsylvania and New York as well as the upper St. Lawrence River, Canada (Ortman 1919, Johnson 1970).
Historic range includes northeastern Oklahoma and Alabama.
Native:Canada (Ontario, Québec); United States (Alabama, Arkansas, District of Columbia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Nebraska, New York, North Dakota, Ohio, Oklahoma - Possibly Extinct, Pennsylvania, South Dakota, Tennessee, Vermont, Virginia, West Virginia, Wisconsin)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total population size is unknown. Although it is wide ranging, this species usually occurs in very small numbers, with survey efforts often yielding only one individual at a site. Five states (Ohio, Illinois, Pennsylvania, Tennessee, Wisconsin) have a substantial number of populations (Cordeiro 2009), with over 100 locations in Ohio (Lyons et al. 2007, Watters et al. 2009). In Ontario, it is broadly distributed throughout the Lake Huron, Lake St. Clair, Lake Erie, and Lake Ontario drainages and is frequently encountered and often plentiful (Metcalfe-Smith and Cadmore-Vokey 2004).|
It has experienced declines (perhaps 10-20% overall: Cordeiro, pers. comm., 2009), including in Minnesota, where it is listed as a threatened species (Minnesota DNR 2015), Virginia (Pinder et al. 2002), Tennessee (Parmalee and Bogan 1998) and Kentucky, where is it extant at only 23 out 70 listed populations (Cordeiro 2009).
It may be extinct in two states at the edges of its range, Alabama (Williams et al. 2008) and Oklahoma (Branson 1983).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Whilst the Elktoe can be found in medium to large rivers, Parmalee and Bogan (1998) state that it reaches its greatest abundance in small, shallow rivers with a moderately fast current in a mixture of fine gravel and sand (Cummings and Mayer 1992). Ortman (1919) described it as a riffle species that is found in swift current in firmly packed fine to course gravel. Parmalee (1967) reported the habitat to be small streams with good current and sand or gravel bottoms at depths of several inches to two feet. In contrast Neel and Allen (1964) found it to be more abundant in the mainstream Cumberland River than in small streams.|
|Continuing decline in area, extent and/or quality of habitat:||Unknown|
|Generation Length (years):||10-25|
|Movement patterns:||Not a Migrant|
|Use and Trade:||Although this species is found in areas where historically there were mussel shells used in the button and pearl industry, it is not likely that this species was used due to the rarity and thin shell.|
The most common threats to this species noted by the states are degradation of water quality due to run-off from agricultural, urban and industrial areas, impoundments or altered hydrology, coal mining (acid mine drainage, increased sedimentation, etc.), oil and gas development, stream gravel removal, and clear cutting of forest and riparian vegetation (Cordeiro 2009).
In Minnesota the populations are threatened by hydrologic alteration of streams and their watersheds, and non-point and point source water and sediment pollution (Minnesota DNR 2015).
This species is also being impacted by the infestation of non-native mussels (e.g., 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 (Minnesota DNR 2015).
Minnesota: A 10-year statewide mussel survey initiated by the Minnesota DNR in 1999 resulted in a better understanding of the Elktoe's ecology and current status in Minnesota. Ongoing mussel surveys in some of the rivers that make up this species' historical range will further aid in the documentation of the distribution of the Elktoe.
As with all unionid bivalves, maintaining water quality, flow, and ensuring that the host fish species are present is essential. Several common fish species are known as hosts therefore water quality and maintaining adequate habitat would be of primary importance.
In some areas control of invasive species would benefit this species.
|Citation:||Woolnough, D. & Bogan, A.E. 2017. Alasmidonta marginata. The IUCN Red List of Threatened Species 2017: e.T779A69490612.Downloaded on 25 February 2018.|
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