Two for the Price of One: eDNA Metabarcoding Reveals Temporal and Spatial Variability of Mussel and Fish co-distributions in Michigan Riverine Systems
Freshwater mussels have an intriguing life cycle because their larvae often “hitchhikes” for days or weeks as low-cost parasites on fish before settling to the bottom and growing a shell. That critical coupling makes it important to understand the distribution of both mussels and fish as managers strive to avoid further losses of endangered mussels.
This challenge is taken up in the recent publication, “Two for the Price of One: eDNA Metabarcoding Reveals Temporal and Spatial Variability of Mussel and Fish co-distributions in Michigan Riverine Systems,” which appears in the journal Environmental DNA and was coauthored by NE CASC Principal Investigator Peter McIntyre.
For the study, McIntyre and his collaborators employed an environmental DNA (eDNA metabarcoding) approach in which water samples were filtered to collect sloughed cells from both mussels and fish and then analyzed for species-specific DNA 'barcodes' to categorize samples by taxa. The team surveyed dozens of Lake Michigan tributaries and discovered that sampling at tributary outlets did not accurately capture the upstream diversity of mussels and fish. However, extensive sampling within the Grand River network revealed hotspots of mussel diversity, including new locations for many species. To complement traditional species-based assessments of mussel-host fish coupling, the team analyzed the co-distribution patterns of fish and mussels using eDNA detections. Through this approach, researchers learned that flathead catfish and shiner minnows are associated with peak mussel diversity, suggesting that these species may function as key hosts.
This study is among the first to validate the use of eDNA methods for overcoming the challenge of surveying mussels in the field, a time-consuming process that has left many reaches unassessed even within priority river basins. More importantly, it demonstrates that eDNA results can help direct intensive field surveys if applied in a systematic way, thereby maximizing the complementarity among these methods. Finally, its findings also suggest that eDNA-based insights into co-distribution of fish and mussels could enhance the success of restoration efforts as mussel populations are deliberately planted following habitat improvements such as dam removals and erosion controls.