Bright, R.C., C. Gatenby, D. Olson, and E. Plummer. 1990. A survey of the mussels of the Minnesota River, 1989. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 106 pp.
A survey of the mussels of the Minnesota river of southern Minnesota was made during the summer of 1989. Fifty-nine sites were studied and 1268 live specimens representing 20 species were examined for size, condition, and abundance. The distribution of both live and dead species was determined from the site analysis. Both quadrats and timed searches were employed to gather the data.
Forty native species have been reported to have occurred in the river since the late 1800's, but one of them, Anodonta grandis corpulenta, was not distinguished from Anodonta grandis grandis for the purposes of this study. Of the 39 taxa recognized, only 20 were found to be living in the Minnesota river now, 17 others apparently have been extirpated, and two species are extralimital. Corbicula fluminea, the introduced Asiatic Clam, was found in the lowermost part of the river in 1978, but has not been found live there since.
Many of the extant species are considered to be in some degree of trouble. No signs of reproduction or recruitment were found at many sites, and at others they ranged from poor to good. Both reproduction and recruitment success differed among the species.
Density was found to be low at most sites and no mussels were found at a few others. Both density and diversity (as number of species) were highest just below dams as the result of fish congregating there and the reasonably stable habitat provided by the dam.
Among the variety of limiting factors affecting the mussels of the Minnesota river, drought, unstable substrates, excessive siltation, and perhaps chemical pollution emerge as the most important ones.
In its present condition, the Minnesota river mussel fauna cannot tolerate commercial harvesting.