Changes in Texas Stream Flows Could Prove Disastrous for Endangered Freshwater Mussels

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South Central CASC project builds off a U.S. Fish and Wildlife Service study that highlights how changes in stream flows affect mussel survival across Central Texas. 

Six freshwater mussels of varying shapes and colors sit in a person’s cupped hands.

A biologist displays six endangered freshwater mussel species collected in in the Clinch and Powell River Watersheds in Virginia. Credit: USFWS, Northeast Region.  

(Public domain.)

Read the feature story on the U.S. Fish and Wildlife Service website here

Although often small and easy to overlook, freshwater mussels are important for stream ecosystems. They provide crucial ecosystem services, such as water filtration, and serve as food and habitat for many species, including culturally important sport fish. Yet mussels are both extremely sensitive to change and unable to move away from unsuitable conditions, making them highly vulnerable to disturbance, pollution, and climate change.  

Under climate change, many streams are experiencing unusual changes in stream flows, where water levels dip from lack of rain, surge after storms, or bounce back and forth between low and high levels (“whiplashes” or “boomerangs”). Mussels that position themselves poorly are dried up or washed away during these extremes. As such, understanding the new realities of North American stream dynamics is crucial for freshwater mussel conservation. 

Researchers from Texas A&M and The Nature Conservancy have partnered with the U.S. Fish and Wildlife Service to study how stream flows in Texas waterways affect a rare mussel species by depositing juvenile mussels reared by Inks Dam National Fish Hatchery into study sites along the San Saba River in Texas. The researchers will measure the juveniles over time to determine how stream levels and water temperature affect growth and survival. 

Building off of this collaboration’s work, the South Central CASC has funded a companion study to determine how shifts between streamflow extremes affect freshwater mussel populations across the Colorado River basin. The South Central CASC supported researchers will model rainfall and river data to project future precipitation patterns and extremes in Central Texas and use this information to better understand future river conditions that freshwater mussels may experience.  

Both projects hope that their results will be directly applicable for resource managers tasked with mussel conservation.  

This research is part of the “Assessing the Impacts of Rapid Rainfall Shifts (“Whiplashes” and “Boomerangs”) on Freshwater Mussels in Central Texas” funded by the South Central CASC. 

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Split-open, dead mussels litter a rocky stream bed punctuated by strands of tall grass.

Dead mussels are visible in the water of the Clinch River in Virginia after a mussel die-off. Credit: Meagan Racey, USFWS 

(Public domain.)