Freshwater mussels (Unionids) are a very diverse group of bivalves, with about 300 species in the United States. Although freshwater mussels are very diverse, they are also critically endangered and are declining at extremely high rates. In fact, the U.S. Fish and Wildlife Service proposed excluding eight freshwater mussel species from the Endangered Species Act (ESA) in 2021 because they went extinct. Mussels play a key role in keeping our water systems healthy because of their filter feeding method. Filter feeding influences the rest of the ecosystem through the transfer of energy, cycling of nutrients, and purification of the surrounding water. Multispecies mussel beds challenge ecological theory which suggests that multiple species cannot occupy the same niche because of resource competition. This study focuses on determining what food resources freshwater mussels consume and evaluate if, and to what extent, mussel species in a complex, multispecies freshwater mussel bed are partitioning available food resources. We examined the available food resources using eDNA and the preferred food resources of four species of freshwater mussels (pistolgrip (Tritogonia verrucose), yellow sandshell (Lampsilis teres), Texas pigtoe (Fusconaia askewi), and the bluefer (Potamilis purpuratus)) found in a single mussel bed in the Sabine River (Texas). These species will be used to address the following questions: 1) Does shell morphology and habitat preference affect the food resources that freshwater mussels are utilizing; 2) Are tissue and shell coloration of some mussels related to the algae (pigments) they are utilizing as food resources? Results show that the pigments of the algae mussels are consuming has likely no relationship to the colorization of the mussel’s tissue or shell; however, our results did support that the shell morphology of the mussel can determine if a mussel is a food resource specialist or generalist. Based on the data presented here and previous habitat data, the pistolgrip can be classified as a specialist and the yellow sandshell a generalist based on these mussel’s habitat and food resource preferences. These results support ecological theory that mussels co-exist in the same environment because they utilize different food resources. Overall, this study aids in our ability to promote healthy freshwater environments through the management of mussel conservation.

Date of publication

Summer 8-23-2022

Document Type




Persistent identifier


Committee members

Dr. Matthew Greenwold, Dr. Lance Williams, Dr. Katrin Kellner


Masters in Biology

Included in

Biology Commons