Spatial distribution of native freshwater mussels across six reaches of the upper Mississippi River, 2006-2019

We conducted large-scale systematic surveys for native mussels across six reaches of the upper Mississippi River. In each reach, divers placed two 0.25 square meter quadrat frames on the river bottom. The duplicate quadrats, which were placed 10 m apart in an upstream to downstream direction, were used to increase the area sampled at each site and increase the effectiveness of this cluster design. Divers excavated substrates to a depth of about 15 cm and placed material into a 6 mm mesh bag. Mussels were identified to species, aged via external annuli, measured for shell length, and sexed (in species with external sexual dimorphism).