Freshwater Mussel Relocation

Freshwater Mussel Relocation

Freshwater mussels are the most imperiled faunal group in North America. Nearly twothirds of the continent’s approximately 300 species are extinct, endangered, or in decline. In Maryland, 14 of the state’s 16 mussel species are rare, threatened, or endangered. Even common species, like Eastern elliptio, have declined in their range and abundance. Mussels have experienced a high rate of imperilment because they are very sensitive to habitat and landscape alterations.

Deer Creek is a Scenic River, which requires the state protect and enhance the river’s qualities. It is afforded further protection under the Maryland Clean Water Act. Maryland Route 24 runs parallel to Deer Creek within Rocks State Park in Harford County. Stream bank sloughing created concern that the road could fail without bank armoring, which required impacts to Deer Creek including temporary fill, excavation, and dewatering. The potential take of a state listed mussel and alteration to its habitat necessitated the removal of mussels from the impact area.

Mussel relocation has been used as a conservation strategy for decades to avoid harm from infrastructure projects. The success of early relocation projects was largely unknown since they were rarely monitored and the ecology of most species was poorly understood. Projects that were monitored often observed high mortality. Critical evaluation was also difficult because mussels can exist at very low numbers and be buried in the substrate. Prior research developed guidelines to reduce mortality due to handling, transportation, and stocking. Further study is needed to determine more effective ways to remove mussels from impact areas and minimize the risk that the relocation will cause harm to these mussels and populations in refuge habitat. 

In accordance with permit conditions of the Maryland Department of the Environment, the Maryland State Highway Administration contracted with the Maryland Department of Natural Resources to conduct a relocation of freshwater mussels in 2014. The effort removed mussels from within the direct and indirect impact areas associated with instream construction activities to stabilize MD Route 24, Section A, along Deer Creek. The project was designed in a manner to evaluate the success of the removal and relocation effort by incorporating standard protocols, relocation guidelines, and monitoring techniques proposed in other studies. The findings from this study can inform future management decisions when mussel relocation may be warranted.

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