Investigating Strategies for Restoring Freshwater Mussels

Freshwater mussels are one of the most imperiled groups of organisms worldwide. As filter feeders, they are keystone species that provide critical ecosystem services, similar to oysters in estuaries. As such, they serve as indicators of the integrated response of watersheds to human activities. Mussels also are high-priority conservation targets because over 80 species are threatened or endangered. Since the 1970s, entire mussel communities have disappeared from streams throughout the U.S., and these declines continue. These declines are enigmatic because no clear causes are evident and other aquatic organisms appear unaffected. Current explanations are based mainly on speculation. This severely limits our ability to develop science-based conservation and restoration strategies, and it may have caused scarce conservation dollars to be spent in ways that do not address the problem. We propose to conduct a series of studies aimed at discovering causes of mussel declines and evaluating land management and other strategies that may be effective for addressing them. The first component will be evaluating the potential for viral and bacterial pathogens as a cause of mussel declines. We will assess this by exposing juvenile mussels to ambient conditions in about 8 streams in Kentucky. After exposure, we will screen for viral and bacterial pathogens using genetic screening and histological examination. The second component involves assessing potential impacts of invasive Asian Clams (Corbicula fluminea) on native mussels. This work will be conducted through a series of field and laboratory experiments. The third component will be a meta-analysis of associations between large-scale landscape and other factors and mussel faunal health. For this component, we will build a comprehensive dataset including current and historical observations on hydrology, land use, invasive species, water chemistry, climate, and other potential causal factors, as well as assessments of mussel faunal health, across a series of study streams in the southeastern US. This work will provide valuable information about specific factors involved in mussel declines, which will inform management strategies. The work also will assess the extent to which streams may have recovered from previous impacts and are now candidates for mussel restoration. Phase one of this work will be conducted from 2020-2022. Additional, follow-up work will be undertaken in subsequent years dependent on acquisition of additional funding.