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Goal: Sustain Our Nation’s Forests and Grasslands Discovering causes of mysterious mussel declines

Forest Service researchers developed a method for assessing responses of juvenile mussels caged in streams in concrete “silos” (A). Mussels in impaired streams show little growth (B), compared with those in streams that support healthy mussel populations (C). This suggests that chronic stressors that reduce growth may be factors in mussel declines. (Forest Service photo by Wendell R. Haag)


Freshwater mussels are keystone members of aquatic ecosystems that, as filter feeders, enhance water quality and overall ecosystem health. However, many species are on the verge of extinction, often for unknown reasons. Forest Service research is providing critical information for discovering causes of mussel declines and prescribing management actions that can address them.


The southeastern U.S. supports the most diverse mussel fauna on Earth. Freshwater mussels are filter feeders that enhance water quality and overall ecosystem health. However, mussels are declining alarmingly worldwide, and many species are on the verge of extinction.

Land management aimed at addressing this crisis is severely hampered by a lack of science-based information about the causes of these declines. SRS researchers are at the forefront of efforts to understand causes of declines and prescribe management actions to address them.

SRS researchers and collaborators developed a method for assessing stream health based on responses of caged young mussels. Caged mussels act as sentinels—similar to canaries in a coal mine—that provide valuable information about effects of a wide variety of factors on mussels and aquatic ecosystems in general. Mussels can be raised in hatcheries, which avoids impacts to wild populations yet provides large numbers of ideal study animals.

SRS research has produced three influential reviews of

  • The spatial and temporal occurrence of mussel declines,
  • An assessment of management efforts designed to address declines, and
  • A critique of hatchery production methods for restoration.

In addition, ongoing research is investigating the potential role of invasive species and pathogens in mussel declines.

Principal Investigator
Wendell R. Haag, Research Fisheries Biologist
4155 - Center for Bottomland Hardwoods Research
Strategic Program Areas
Invasive Species
Water, Air, and Soil
Wildlife and Fish
Growth and survival of juvenile freshwater mussels in streams: Implications for understanding enigmatic mussel declines
Reassessing enigmatic mussel declines in the United States
Biodiversity on the brink: an assessment of conservation strategies for North American freshwater mussels
Essay: Making the most of recent advances in freshwater mussel propagation and restoration
CompassLive Article
Closer to Understanding Enigmatic Mussel Declines
Research Partner
Daniel Boone National Forest, Kentucky
External Partners
Kentucky Department of Fish and Wildlife Resources
Kentucky Division of Water
U.S. Fish and Wildlife Service
University of Kentucky
Auburn University
University of Georgia
Kentucky State University
Murray State University