Physical habitat of zebra mussel (Dreissena polymorpha) in the lower Ebro River (Northeastern Spain): influence of hydraulic parameters in their distribution

Dreissena polymorpha (zebra mussel) is a freshwater bivalve mollusc and has been present for more than one decade in Spain. The zebra mussel causes serious ecological and socioeconomic impacts in areas where they settle. Our research aims to analyze its hydraulic habitat, developing physical models for this species, which indicates its preference and optimal microhabitat requirements. To get it, a survey was completed in a lotic reach in the lower Ebro River (Tarragona, Spain). Habitat suitability curves for the variables include water velocity, depth, Froude number, velocity/depth ratio, shear stress and shear stress ratio (RSS). In addition, interactive effects between hydraulic parameters on habitat selection and its use were studied and bivariate habitat models were developed. A close relationship was observed between the D. polymorpha presence and mean flow velocity combined with depth, Froude number and RSS. Suitable habitat requirements for Dreissena were detected in areas with stable river beds under high flows, and velocity below 1.2 m/s with a depth of less than 5 m under regular flows. Information about zebra mussel preferences may enhance the design of monitoring programmes and the integrated control management of this invasive mussel.