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North Dakota's

Federally Listed Endangered, Threatened, and Candidate Species – 1995


Elktoe (Alasmidonta marginata)

GIF -- species photo gif--species map

Note: If you have a photo of this species that you feel would be appropriate for this resource, please contact us at npwrc@usgs.gov. All photos will be properly credited and will remain the property of the photographer.

Status: Former Candidate (Note: As of February 28, 1996, this species is no longer listed as a Candidate species. However, it remains a species of management concern.)

Historical Status:
The elktoe mussel has been historically found in Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Maryland, Michigan, Missouri, Minnesota, North Dakota, New York, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Virginia, Wisconsin, West Virginia, and Ontario, Canada. The elktoe has not been observed in the Upper Mississippi River drainage in recent decades. The last elktoe collection in North Dakota was reported by Dr. J.K. Neel of the Department of Biology, University of North Dakota in 1970.

Present Status:
The elktoe is listed as a species of "special concern" by the American Fishery Society Endangered Species Committee in twenty-two states, including North Dakota and the canadian province of Ontario in 1990. The elktoe is also listed as state threatened in Iowa. The elktoe is distributed in the Mississippi River drainage west to North Dakota, south to Arkansas, north into Ontario and Manitoba, and east in the Ohio River extending to New York. The species is usually not abundant where it is found, but some locally abundant populations are present. The elktoe has been collected in North Dakota in the Red River.

Habitat:
The elktoe mussel requires a specific habitat in order to maintain a healthy population. The components of habitat that the elktoe requires include: a specific depth, a specific flow of water, and a specific mix of bottom composition. The elktoe is known to live in the riffle sections of small to medium sized streams with gravel and sand bottoms.

Life History:
The elktoe mussel begins reproduction in early spring. A female elktoe, after fertilization, produces glochidia (larvae), which are expelled into the water. The elktoe mussel requires a "host" organism, which usually is one or several fish species, to incubate their larvae. The fish which the elktoe uses are the white sucker, northern hogsuckers, shorthead redhorse, rock bass, and warmouth. The attached larvae grow and change into young mussels. The young elktoe drop to the bottom and become independent. The elktoe mussel becomes dormant during winter, reducing growth and body functions.

Aid to identification:
The elktoe's shell is elongated with a dorsal margin gently rounded and the ventral margin nearly straight. The anterior end is rounded and the posterior end is obliquely truncated ending in a squarish point. The shell is yellow-brown with numerous broad green rays and speckled with dark green dots. Average size of an adult elktoe is 5 inches.

Reasons for decline:
Elktoe mussels are threatened by waterway modification, streambed changes, commercial barge activities, sedimentation, commercial mussel fishing, host fish absence, exotic mussel competition, and environmental contaminants.

Recommendations:
If you observe an elktoe mussel please notify a natural resource agency.

References:
Field Guide to Freshwater Mussels of the Midwest, by K.S. Cummings and C.A. Mayer, 1992. Published by the Illinois Natural History Survey Manual 5, Champaign, Illinois.
Missouri Naiades. A Guide to the Mussels of Missouri, by R.D. Oesch, 1984. Published by the Missouri Department of Conservation, Jefferson City, Missouri.
Conservation Status of Freshwater Mussels of the United States and Canada, by J.D. Williams, M.L. Warren, Jr., K.S. Cummings, J.L. Harnes, and R.J. Neves, 1993. Published in Fisheries, Vol. 18, No. 9.


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