Effect of substrate and hydrodynamic conditions on the formation of mussel beds in a large river

A numerical model for simulation of freshwater mussel dynamics was used to investigate the effects of substrate and hydrodynamic conditions on the formation of mussel beds in a 10-km reach of the Upper Mississippi River (UMR). Suitable habitats for mussel survival were identified by creating a dimensionless parameter (shear stress ratio) combining shear force and substrate type. This parameter is a measure of substrate stability that could be used in many different applications. Dispersal of juvenile mussels with flow as they detach from their fish hosts was simulated by a particle-tracking mechanism that identified suitable areas for colonization with the potential to evolve into mussel beds. Simulated areas of mussel accumulation coincided with reported locations of mussel beds, and simulated densities were in the range of abundant mussel beds in other reaches of the UMR. These results, although more qualitative than quantitative, provide insight into factors influencing the formation of mussel beds in a large river.