On today’s blog, we’re celebrating a recent milestone in the Mission Reach Mussel Reintroduction Project: the successful reintroduction of all four target mussel species into the Mission Reach. These four species, the Yellow Sandshell (Lampsilis teres), Threeridge (Amblema plicata), Pistolgrip (Tritogonia verrucosa), and Pimpleback (Cyclonaias pustulosa), were selected for their ecological significance and their potential to thrive in the restored river ecosystem. As of the end of 2024, a total of over 3,500 mussels from all four species have been reintroduced into the Mission Reach, marking a significant step forward in the reintroduction effort!
All four species of reintroduced mussels (Yellow Sandshell, Threeridge, Pistolgrip and Pimpleback). Can you identify them?
The Mussel Reintroduction Project—Let’s Recap!
The Upper San Antonio River once boasted a diverse mussel community, but as the river was modified to help with flood control, these mussels disappeared from the area. In 2013, the San Antonio River Authority (River Authority) completed the Mission Reach Restoration Project, which aimed to improve the river’s health, enhance wildlife habitats, and increase opportunities for recreation. This ambitious project reintroduced native vegetation, restored natural river meanders, and improved water quality. But one key element was still missing: the freshwater mussels that once played a crucial role in the river’s ecosystem.
Aquatic biologist Caille Marshall holding a Flathead Catfish that will serve as a host for mussel propagation.
In 2017, Aquatic Biologists at the River Authority began planning the reintroduction of freshwater mussels into the Mission Reach. To guide this effort, they conducted several feasibility studies to evaluate the river’s habitat, water quality, and the availability of host fish, which are essential for the mussels’ life cycle. Based on these findings, a strategy for mussel propagation was developed in collaboration with the U.S. Fish and Wildlife Service. With the prep-work for the project complete, the first cohort of Yellow Sandshell (Lampsilis teres) mussels were reintroduced to the river on May 17th 2024, in a groundbreaking and highly anticipated milestone.
Aquatic biologist Mitch Magruder places mussels in the San Antonio River.
Tracking Success: Mark and Recapture Study
Beyond simply reintroducing the mussels — Aquatic Biologists at the River Authority are closely monitoring their progress to ensure their success. Through a Mark-Recapture study, they’re tracking the survival, growth, and movement of the mussels. Here’s how it works: before the mussels were re-introduced, the biologists at the River Authority measured the size, and etched a small mark on the shells for identification. On 25% of the individuals of each species, a PIT tag (Passive Integrated Transponder) was attached to the shell of the mussel. This tiny microchip contains a unique code that will be used to identify and track the mussels.
Aquatic biologists marking and attaching PIT tags.
Juvenile mussels with attached PIT tags.
In the spring of 2025, the biologists will attempt to re-capture the re-introduced mussels by conducting timed searches and sieving specific quadrats to find the individuals. If a mussel without a mark is found, it will be an indication that the mussels have begun to reproduce naturally in the wild—a key goal of the project! To assist in the search effort, biologists will also be using a PIT tag reader, which emits an electromagnetic signal. The biologists will scan the reader over the water, and if a PIT tagged mussel is in range, the unique code will be read by the reader. This will allow the biologists to track the mussel’s movements and measure its growth.
Over time, the goal is to evaluate the natural reproduction of these mussels, determine average growth rates, and track their movements. This will help scientists understand their impact on the ecosystem by improving water quality, creating habitats for other species, and boosting biodiversity! Stay tuned for more mussel milestones!
