Freshwater Mussel Conservation

Freshwater mussel conservation is a hot topic and our very own Heidi Dunn recently published an innovative assessment framework to evaluate freshwater mussel communities from a conservation status standpoint. Almost all multi-metric indices of biological integrity (IBI’s), including fish community IBI’s, benthic macroinvertebrate community IBI’s, or periphyton community IBI’s, evaluate attributes of community structure through the lens of water quality or habitat quality impairment. The Mussel Community Assessment Tool (MCAT) is designed to evaluate the health of freshwater mussel communities for conservation purposes.

Developing the Multi-Metric Index

Data from 25 sites within the Upper Mississippi River, spanning 925 river kilometers from Pool 2 to Pool 26, were used to develop the MCAT. These freshwater mussel survey data were collected in support of permit applications under Section 404 of the Clean Water Act or Section 10 of the Rivers and Harbors Act. Most data were collected by Ecological Specialists, Inc. (now EcoAnalysts, Inc.). A suite of 46 candidate metrics was evaluated for potential inclusion into the MCAT. Metrics covered a variety of community attributes such as conservation status (percent species federally or state listed), environmental sensitivity (percent tolerant), taxonomic composition (e.g. percent Lampsilini), population processes (age structure, live vs. recently dead shells, etc.), abundance, and diversity.

Metrics having strong correlations within the same group were eliminated and those metrics least influenced by sample size or distribution were prioritized to be retained. A final list of 10 metrics was included in the MCAT. To validate the results, a workgroup of 10 natural resources managers was convened to evaluate MCAT performance on additional data sets. Agencies present at the workshop included Minnesota Department of Natural Resources, Wisconsin Department of Natural Resources, Iowa Department of Natural Resources, Missouri Department of Conservation, National Park Service, US Army Corps of Engineers, and US Fish and Wildlife Service. 

Evaluating Freshwater Mussel Community Health

The MCAT can be used to compare the health of freshwater mussel assemblages between sites, or over time at same sites. It can also be used to evaluate the impact of management decisions, such as dam removal, construction of in-river habitat features, reservoir drawdown, etc. Although developed specifically for the Upper Mississippi River, the authors encourage mussel researchers and resource managers to experiment with its application in other systems to provide feedback and improve the MCAT over time.

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Citation

Dunn, H. L., S. Zigler and T. Newton. 2020. Mussel Community Assessment Tool for the Upper Mississippi River System. Freshwater Mollusk Biology and Conservation 23: 109-123.

Heidi Dunn is a senior aquatic ecologist at EcoAnalysts in O’Fallon, MO. Co-authors Steve Zigler (retired) and Teresa Newton are biologists at the US Geological Survey, Upper Midwest Environmental Sciences Center in LaCrosse, WI.