Figure H-2. Zebra mussel infestation of native unionids at two sites in Reach 15 of the Upper 

 Mississippi River from July 1994 through September 1995. (a) % Infestation refers to 

 the number of unionids with one or more attached zebra mussels, (b) Degree of 

 Infestation refers to the number of attached zebra mussels on each unionid. 



July 

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