Dams and Clams: Freshwater Mussel Surveys and Translocations in the Context of Dam Removal Projects

Dams have multiple negative impacts on freshwater mussel populations, and dam removals are sometimes partly justified by expected long-term benefits to mussel communities. However, dam removal activities can also negatively impact upstream and downstream mussel populations, and it may be necessary to translocate all or selected mussel species from the project area. Quantitative surveys of the project site are usually required to assess the need for translocation activities, and also of potential translocation sites to assess their suitability for long-term mussel survival and reproduction. Planning and executing a translocation project must consider multiple factors, including choice of a translocation site, collection procedures at the project site, details of mussel transport to the translocation site, timing of mussel breeding, water and air temperatures, and post-translocation monitoring. Selection of an appropriate translocation site is absolutely vital to the success of a translocation project, and factors to consider include proximity and similarity to the project site, sediment stability and quality, existing mussel populations, water quality, and host fish and invasive species presence. A decision tree that outlines the information requirements and recommendations for mussel translocations, which is under consideration by the Department of Interior's multi-agency Subcommittee on Sedimentation, is discussed.