Freshwater mussels perform critical ecosystem functions and provide many valuable ecological services. However, anthropogenic effects have severely decreased mussel diversity and abundance at both local and regional scales. Understanding how human disturbances, particularly landuse change, and fish assemblages are related to mussel assemblages is essential for effective conservation and restoration. We used Random Forests (RF) regressions, a data-mining technique, to examine how mussel species richness, total abundance, and abundances of individual species were related to land use at different spatial scales and to fish species richness and abundance in east central Illinois, USA. Mussel richness increased with % wetlands, % open water, % grassland in the riparian zone, and total fish abundance; decreased with % urban land in the riparian zone; but responded poorly to fish species richness and fish Index of Biotic Integrity (IBI) scores. Total mussel abundance mainly increased with total fish abundance and decreased with both % urban land in the riparian zone and road density. Of 8 mussel species modeled, the abundances of 3 were strongly related to total fish abundance or fish-host abundance, 3 with both fish abundance and land use, and 2 with land use and other physical variables. These findings can help researchers and resource managers explain the spatial variation of mussel assemblages and choose abiotic and biotic variables to monitor or manipulate for maintaining or restoring overall mussel diversity or the populations of individual species.