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Havlik, M.E. 1995. A 1994 Unionid mussel survey (Mollusca: Bivalvia: Unionidae) from the headwaters of the Root River system, Minnesota, to the Mississippi River. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 28+ pp.


The Root River of Minnesota apparently has never been surveyed for unionid mussels. This report gives the results of sampling for unionids from 6 17 June 1994 at 117 bridge and road access sites between the Root River system headwaters and the Mississippi River. We also sampled sites on the nearby Upper Iowa (2) and Little Iowa Rivers (8), for a total of 127 sites.

The main stem of the Root River starts just NE of Lanesboro, MN, at the confluence of the North and Middle Branches, and flows easterly to its confluence with the Mississippi River, between La Crescent and Brownsville, MN. Sampling consisted of wading and shoreline searches in the headwaters and middle reaches of the Root River system, and shoreline searches by boat in the lower six miles of the Root River from Hokah, MN, to the, river's mouth.

This Root River survey included the main stem and all four major tributaries, and yielded at least 16 unionid mussel species. However, only three species were found alive, represented by five living mussels: Venustaconcha e. ellipsiformis (Conrad, 1836), Ellipse (3), and Lampsilis radiata luteola (Lamarck, 1819), Fatmucket (1) were found at one South Branch site, 0.5 mi N of Etna, MN, and one Anodontoides ferussacianus (Lea, 1834) Cylindrical Papershell, was found at a North Branch site, 4 mi NW of Dexter, MN. A number of the remaining species were represented by fairly fresh dead shells. The most species (12) were found in the North Branch of the Root River, among 22 sites, however the most shells were found in the South Branch among 40 sites (nine species). Eleven species were found among eight sites on the Middle Branch of the Root River. The most common species found, both dead and alive, Venustaconcha e. ellipsiformis, also lives in the Cannon and Zumbro Rivers of southeastern Minnesota, but apparently was not found in western Wisconsin for over 60 years, until 1992 1994, when it was found in a tributary of the Chippewa River, near Cadott, WI.

Overall, our data show severe impacts to the 117 sites on the Root River system. We were unable to pinpoint the precise impacts that led to this situation, but our preliminary conclusions are that cumulative impacts, primarily agricultural, are apparently responsible. Since the Zebra Mussel is exploding in the Mississippi system, we must quickly identify tributary molluscan fauna, or risk losing unique populations before they can be identified. We hope to have additional funding to complete areas not sampled in 1994, including portions of the North Branch, South Branch, and Root River main stem, plus a number of tributary creeks.

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