An analysis of the mussel species distribution in the St. Croix had been published:

Hornbach, D.J. 2001. Macrohabitat factors influencing the distribution and abundance of naiads in the St. Croix River, MN and WI, USA, pp. 213-230. In G. Bauer and W. Wächtler [eds] Ecology and Evolutionary Biology of the Freshwater Mussels Unionoidea. Ecological Studies Vol. 145 Springer Verlag: Berlin.

Click on a graph below

The River:

The Distribution of the subfamilies:

Change in Eveness and Diversity: