Potential for juvenile freshwater mussels to settle onto riverbeds from field investigation

Abstract

Freshwater mussel populations have been declining at an alarming rate around the world. Herein, we investigate whether changing flow conditions, as they affect juvenile freshwater mussel settling, could be a potential causative factor for this decline in the Dan River, North Carolina, USA. We deployed two uplooking velocity sensors on the riverbed between May and November 2019: one where mussels reside and another where they do not. From this data, we calculated shear velocity, which is a measure of the turbulence that acts to lift particles into suspension and acts against particle settling. We determined that a shear velocity less than 0.66 cm/s would be required to settle relatively large and dense juvenile mussels onto the riverbed; however, the lowest shear velocity we measured was 0.9 cm/s. Additionally, we estimated that juvenile freshwater mussels as large as 280-510 µm could always be suspended and not be able to settle onto the riverbed at these two locations. Therefore, the flow during May-November 2019 was high enough to prohibit recruitment of juvenile freshwater mussels at the sensor locations. Furthermore, we have identified that the magnitude of the lowest flows has increased since 2000, which may be exacerbating the decline in freshwater mussels.

Keywords:

• Dan River
• James spinymussel
• juvenile freshwater mussel
• Parvaspina collina
• sediment transport
• settling velocity

Acknowledgments

We thank David Byrd, Marilyn Knight, John McCloskey and Rick McCorkle (U.S. Fish and Wildlife Service) and Nicholas Christensen, Katie Hegadorn, Dan Irving, Sarah Moorehead, John T. Schubert, and Clayton Travis (Virginia Tech) for their assistance with field data collection. We thank Sierra Benfield (North Carolina Wildlife Resources Commission) for her assistance with the laboratory experiments. We also thank Jason Mays, John McCloskey, Jennifer Stanhope, and Rick McCorkle (U.S. Fish and Wildlife Service), Michael Perkins and Chris Wood (North Carolina Wildlife Resources Commission), and Brian Watson (Virginia Department of Wildlife Resources) for their involvement in discussing this work. We thank two anonymous reviewers, Associate Editor, and Editor-in-Chief (Takashi Asaeda) for their comments that helped improve the presentation of our work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Datasets for this research are freely available via CUAHSI’s HydroShare: https://doi.org/10.4211/hs.a79f3ec8559341bb83cd1dd5705a49f1

Additional information

Funding

This work was partially supported by the North Carolina Wildlife Resources Commission, Virginia Agricultural Experiment Station, and the USDA Hatch program (1017457).