The Altamaha River Basin in Georgia drains more than 14,000 square miles—including rivers in Athens, Macon, and parts of southeast Atlanta—into the Atlantic Ocean. Fish species like American eel, shad, blueback herring, and sturgeon use the Ocmulgee and Oconee Rivers and other tributaries in the watershed as they migrate upstream. However, several barriers, including the Juliette and Sinclair Dams, limit access to upstream habitat these fish have historically used for spawning. These dams are also reducing the quality of habitat by converting natural, free-flowing rivers into artificial lakes and interrupting the downstream flow of sediment.
NOAA worked alongside state and federal resource agencies to develop a basin-wide plan to re-establish fish passage above human-made barriers. The plan also addressed restoring the quality and quantity of available spawning habitat. To inform strategic fish passage design and implementation of the plan, we funded two university-led studies in the basin.
Using eDNA to Track Sturgeon
The first study, led by the University of Georgia, used environmental DNA (eDNA) to determine areas of upstream habitat use of sturgeon species in the Ocmulgee River. eDNA refers to the genetic material shed by aquatic species into the surrounding water. Through continually advancing techniques, researchers can capture that DNA from water samples and identify the species it comes from. eDNA has become an increasingly powerful tool for detecting which species have passed through the water.
Researchers from the University of Georgia analyzed eDNA from water samples collected above and below Juliette Dam on the Ocmulgee River. The eDNA analysis detected Atlantic sturgeon DNA in the water samples from below the dam. This confirmed that this endangered species uses the rocky shoal habitat just below Juliette Dam, possibly for spawning. The findings suggest that sturgeon may migrate further upstream of the Juliette Dam if those habitats were accessible. This study was funded for a second year to sample during additional seasons and assess possible shortnose sturgeon eDNA at the same sites.
Documenting Shad Spawning Locations
NOAA Fisheries also partnered with the U.S. Fish and Wildlife Service to fund a second study led by Georgia Southern University. This study aimed to document American shad spawning locations in currently accessible reaches of the Ocmulgee, Oconee, and Altamaha Rivers.
Researchers sampled several locations to collect shad eggs and recently hatched larvae. They found evidence of American shad spawning near the base of the Juliette and Sinclair Dams. These results confirm that American shad are using the upper limits of their currently accessible habitat and would likely migrate further if the habitat were accessible.
The results from these two studies will help resource managers make the best decisions to reopen these areas to fish migration. They will help us restore the quality and quantity of available spawning habitat. This research will also help resource agencies prioritize future habitat restoration and fish passage efforts in the region.
