We investigated the cultureable bacterial communities in the native freshwater mussel faunal in the Clinch River, VA/TN during mussel mortality events in 2018, 2019 and 2020 and examine the spatial and temporal distribution of bacterial genera among Pheasantshells and six other unionid species.

The diagnosis of bacterial disease in freshwater unionid mussels has been hindered by a lack of baseline information regarding the microbial communities associated with these animals. In this study, we cultured and identified bacteria from the hemolymph of stable mussel populations from the upper Mississippi River basin and compared results to mussel populations associated with a mortality event in the Clinch River, VA and TN. Several bacterial genera were consistently identified across mussel species and locations, appearing to be part of the natural bacterial flora. One noteworthy isolate was identified from the Clinch River. Yokenella regensbergei was found with relatively high prevalence during the mortality event but was absent from post-mortality samples. Its role, if any, in the mortality event is unknown and deserves further investigation. We suggest that future studies of freshwater mussel health utilize hemolymph samples due to its relative disconnect with the aquatic environment, role in the circulatory system and nonlethal nature of collection.

The diagnosis of bacterial disease in freshwater unionid mussels has been hindered by a lack of baseline information regarding the microbial communities associated with these animals. In this study, we cultured and identified bacteria from the hemolymph of stable mussel populations from the upper Mississippi River basin and compared results to mussel populations associated with a mortality event in the Clinch River, VA and TN. Several bacterial genera were consistently identified across mussel species and locations, appearing to be part of the natural bacterial flora. One noteworthy isolate was identified from the Clinch River. Yokenella regensbergei was found with relatively high prevalence during the mortality event but was absent from post-mortality samples. Its role, if any, in the mortality event is unknown and deserves further investigation. We suggest that future studies of freshwater mussel health utilize hemolymph samples due to its relative disconnect with the aquatic environment, role in the circulatory system and nonlethal nature of collection.

Data from metabarcoding assays to detect a suite of mussel species using mitochondrial DNA regions of the cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit (ND1) genes sequences.

Data from metabarcoding assays to detect a suite of mussel species using mitochondrial DNA regions of the cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit (ND1) genes sequences.

Data are included for two types of field surveys conducted for freshwater mussels throughout the Susquehanna River Basin (and one site in the Potomac River Basin) in the Mid-Atlantic region of the United States from 2008-2010. Timed search (qualitative) surveys were conducted in consecutive ~200 meter sections of river (at least 8 in each stream). The number of mussels of each species and associated search time were recorded for each survey section to determine a catch per unit effort (CPUE; number of individuals found per person hour). Within qualitatively surveyed areas, one ~200 meter section of stream was selected in which to conduct quantitative surveys to estimate mussel abundance, assess presence of juvenile mussels, and quantify population demographics. At each survey site, a subset of ~30 Elliptio complanata was haphazardly selected and retained for shell thin-sectioning and age determination. Two sites (Pine Creek and Buffalo Creek) were resurveyed both qualitatively and quantitatively in 2014 and 2015 after experimental re-introduction of the American eel (Anguilla rostrata), a documented host fish for E. complanata.

Data are included for two types of field surveys conducted for freshwater mussels throughout the Susquehanna River Basin (and one site in the Potomac River Basin) in the Mid-Atlantic region of the United States from 2008-2010. Timed search (qualitative) surveys were conducted in consecutive ~200 meter sections of river (at least 8 in each stream). The number of mussels of each species and associated search time were recorded for each survey section to determine a catch per unit effort (CPUE; number of individuals found per person hour). Within qualitatively surveyed areas, one ~200 meter section of stream was selected in which to conduct quantitative surveys to estimate mussel abundance, assess presence of juvenile mussels, and quantify population demographics. At each survey site, a subset of ~30 Elliptio complanata was haphazardly selected and retained for shell thin-sectioning and age determination. Two sites (Pine Creek and Buffalo Creek) were resurveyed both qualitatively and quantitatively in 2014 and 2015 after experimental re-introduction of the American eel (Anguilla rostrata), a documented host fish for E. complanata.

The Minnesota Department of Natural Resources (MNDNR) has been quantitatively sampling a mussel bed in West Newton Chute (a side channel in Navigation Pool 5 of the Upper Mississippi River, UMR) annually since 2008. Briefly, ~200 systematically-placed 0.25 m2 quads are sampled annually; divers excavate substrates to a depth of ~15 cm and place material into a 6 mm mesh bag. Mussels are identified to species, aged via external annuli, measured for shell length, and sexed. From 2008-2016, this mussel bed contained 12-16 live species, had densities that ranged from 4-10/m2, and juveniles (≤ 5 years old) comprised 3-18% of the assemblage. Because this assemblage was well characterized, it represented an excellent location to estimate vital rates (i.e., survival and growth) in mussels. Our objectives were to estimate patterns in survival and growth across four species of mussels and over time within a mussel bed, and to assess if these patterns changed across patches with varying mussel densities. The counts of live mussels in quadrats sampled by the MNDNR during surveys from 2008-2011 was compiled and interpolated using an inverse distance weighted (IDW) algorithm in ArcGIS. The IDW surface of mussel density was classified by quartiles and the highest quartile was delineated as the core areas of the bed and the lowest quartile was delineated as the peripheral areas of the bed. This resulted in four polygons—two with relatively high mussel densities (core, labelled A1-A5 and B1-B5) and two with relatively low mussel densities (periphery, labelled C1-C5 and D1-D5). Five study plots (5 m x 5 m) were randomly selected within each polygon. Plot C5 was inaccessible, so we used plot C5a. Plots were aligned with the direction of river flow and demarcated into four quarters by driving nine pieces of PVC pipe into the substrate in a 3 x 3 array. To obtain mussels to PIT tag, we haphazardly searched West Newton Chute in August 2012 and obtained 578 mussels, including both common (Amblema plicata, Obliquaria reflexa) and less common (Cyclonaias pustulosa, Pleurobema sintoxia) species. Shells were scrubbed to remove existing zebra mussels. A 20- or 23-mm PIT tag was attached near the umbo of each mussel with cyanoacrylate glue to enable recovery of individual mussels in subsequent years. One end of a 36-cm piece of buoyant fishing line (color coded by species) was glued near the posterior edge of each shell to facilitate recovery. We randomly allocated 9-10 A. plicata and O. reflexa and 4-5 C. pustulosa and P. sintoxia into each plot. Mussels were placed into a randomly chosen quarter of each plot. The age, shell length, and PIT tag identification number of each mussel was recorded prior to placement within a plot. We returned to WNC to recover tagged mussels in August 2013, August 2014, July 2015, and July 2016. Once each plot was found, a diver placed a 2.5 m x 2.5 m PVC frame over each plot quarter to facilitate a thorough search. The diver systematically searched each plot quarter using an 18-cm loop antenna that was connected, via a 15.2 m cord, to a PIT-tag reader located in an attending boat. Surface to diver communication was used to notify the diver when a marked mussel had been found. During recovery efforts, divers searched within each plot and then searched the periphery of each plot (~1-2 m outside each plot) for any marked mussels that might have moved out of the plot. All recovered mussels were identified by PIT tag, recorded as alive or dead, measured for age and shell length, and any attached zebra mussels were removed and counted. If the PIT tag was damaged or missing, we replaced it with a new one and recorded the new PIT tag ID number.

The Minnesota Department of Natural Resources (MNDNR) has been quantitatively sampling a mussel bed in West Newton Chute (a side channel in Navigation Pool 5 of the Upper Mississippi River, UMR) annually since 2008. Briefly, ~200 systematically-placed 0.25 m2 quads are sampled annually; divers excavate substrates to a depth of ~15 cm and place material into a 6 mm mesh bag. Mussels are identified to species, aged via external annuli, measured for shell length, and sexed. From 2008-2016, this mussel bed contained 12-16 live species, had densities that ranged from 4-10/m2, and juveniles (≤ 5 years old) comprised 3-18% of the assemblage. Because this assemblage was well characterized, it represented an excellent location to estimate vital rates (i.e., survival and growth) in mussels. Our objectives were to estimate patterns in survival and growth across four species of mussels and over time within a mussel bed, and to assess if these patterns changed across patches with varying mussel densities. The counts of live mussels in quadrats sampled by the MNDNR during surveys from 2008-2011 was compiled and interpolated using an inverse distance weighted (IDW) algorithm in ArcGIS. The IDW surface of mussel density was classified by quartiles and the highest quartile was delineated as the core areas of the bed and the lowest quartile was delineated as the peripheral areas of the bed. This resulted in four polygons—two with relatively high mussel densities (core, labelled A1-A5 and B1-B5) and two with relatively low mussel densities (periphery, labelled C1-C5 and D1-D5). Five study plots (5 m x 5 m) were randomly selected within each polygon. Plot C5 was inaccessible, so we used plot C5a. Plots were aligned with the direction of river flow and demarcated into four quarters by driving nine pieces of PVC pipe into the substrate in a 3 x 3 array. To obtain mussels to PIT tag, we haphazardly searched West Newton Chute in August 2012 and obtained 578 mussels, including both common (Amblema plicata, Obliquaria reflexa) and less common (Cyclonaias pustulosa, Pleurobema sintoxia) species. Shells were scrubbed to remove existing zebra mussels. A 20- or 23-mm PIT tag was attached near the umbo of each mussel with cyanoacrylate glue to enable recovery of individual mussels in subsequent years. One end of a 36-cm piece of buoyant fishing line (color coded by species) was glued near the posterior edge of each shell to facilitate recovery. We randomly allocated 9-10 A. plicata and O. reflexa and 4-5 C. pustulosa and P. sintoxia into each plot. Mussels were placed into a randomly chosen quarter of each plot. The age, shell length, and PIT tag identification number of each mussel was recorded prior to placement within a plot. We returned to WNC to recover tagged mussels in August 2013, August 2014, July 2015, and July 2016. Once each plot was found, a diver placed a 2.5 m x 2.5 m PVC frame over each plot quarter to facilitate a thorough search. The diver systematically searched each plot quarter using an 18-cm loop antenna that was connected, via a 15.2 m cord, to a PIT-tag reader located in an attending boat. Surface to diver communication was used to notify the diver when a marked mussel had been found. During recovery efforts, divers searched within each plot and then searched the periphery of each plot (~1-2 m outside each plot) for any marked mussels that might have moved out of the plot. All recovered mussels were identified by PIT tag, recorded as alive or dead, measured for age and shell length, and any attached zebra mussels were removed and counted. If the PIT tag was damaged or missing, we replaced it with a new one and recorded the new PIT tag ID number.