Experimental PIT-tagging and translocation of Yellow Lampmussels (Lampsilis cariosa), Tidewater Muckets (Leptodea ochracea), and Eastern Lampmussels (Lampsilis radiata radiata) for removal of the Fort Halifax Dam on the Sebasticook River, Maine
Cynthia S. Loftin, US Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME;
Jennifer E. Kurth, Department of Wildlife Ecology, University of Maine, Orono, Maine;
Judith Rhymer (retired), Department of Wildlife Ecology, University of Maine, Orono, Maine.


Abstract:

Improvement of environmental conditions degraded by impounding flowing waters often is a goal in stream and river restoration projects involving dam removal. Determining whether those improvements are realized requires thoughtful pre-dam removal planning so that appropriate response variables can detect effects indicating system improvement and restoration. Dam removals often improve water quality and increase habitat access for fish, which ultimately improves conditions for some freshwater mussel species. Other mussel species potentially benefit from reduced flow and consistent water levels found in impoundments, and dam removal may reduce the habitat quality and area for them. Minimizing negative effects of dam removals on freshwater mussel populations requires identifying the pre-dam removal mussel species composition, population age structure, and distribution in the water body's impounded and non-impounded areas, knowledge about species-specific habitat suitability, and reliable predictions of the distribution and condition of the post-dam removal environment to ensure survival of translocated mussels. Incomplete information about any of these factors will increase uncertainty about whether conservation measures to minimize effects of a dam removal on freshwater mussel populations actually are successful.

The Fort Halifax dam on the Sebasticook River in Waterville, Maine, was identified for removal in 2002. Two state-listed threatened freshwater mussel species, the yellow lampmussel (Lampsilis cariosa) and the tidewater mucket (Leptodea ochracea), were found in the impoundment, however, their numbers, distribution, and population size structures were unknown, creating uncertainty in the anticipated effects of the dam removal on these species. Although nearby water bodies were identified for translocating mussels from the area to be dewatered, the suitability of the translocation sites also was unknown. We conducted pre-dam removal impoundment surveys to document mussel distribution and abundance and an experimental translocation of tidewater muckets, yellow lampmussels, and eastern lampmussels (Lampsilis radiata radiata) to develop translocation, marking, and monitoring methodology to assess survival one-year post translocation within the Fort Halifax dam impoundment and two additional nearby water bodies. PIT tags improved recaptures of translocated mussels and revealed unsuitability of the Incidental Take Plan (ITP)-proposed translocation sites owing to unstable substrates and muskrat predation. Our surveys revealed yellow lampmussels and tidewater muckets throughout the impoundment, with greatest concentration in the impoundment's upper reaches. Translocation experiments in the upper impoundment indicated that within-waterbody translocation to this area was a viable alternative that would provide a source of mussels to repopulate the newly formed channel following dam removal. Our pre-dam removal impoundment surveys and population estimates, and translocation and recapture of PIT-tagged freshwater mussels informed yellow lampmussel and tidewater mucket conservation measures when the dam was removed in 2008.

Biography:

Dr. Cynthia Loftin is the Unit Leader of the U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit.  She is an Associate Professor of Wildlife Ecology at the University of Maine, Orono, where she advises and collaborates with graduate students in the Wildlife Ecology and Ecology and Environmental Sciences graduate degree programs.  Dr. Loftin’s research interests in systems, landscape, and wetlands ecology drive her research program involving natural systems restoration issues.