By Ethan Hatchett
The Ocmulgee River has changed. The cloudy water once ran clear. The sandy bottom was once rocky. Fish swam upriver to breed from places as distant as the Altamaha River, which the Ocmulgee and Oconee rivers join to form near Lumber City, and the Atlantic Ocean.
European settlement changed the Ocmulgee. Centuries of agriculture and development stripped away much of the land’s vegetation that filtered the flow, causing the river to fill with sediment. The soil particles gradually moved through the waterway, covering gravel that fish spawned in, smothering fishes’ eggs, mucking up the water and even building up on the banks, saturating the ground with sediment.
Robust redhorse (Alan Cressler)
It is impossible to know how many freshwater fish the Ocmulgee lost since the first Europeans arrived. Many species disappeared without being discovered. Yet on a clear afternoon last month, DNR aquatics biologist Paula Marcinek led a team on the upper Ocmulgee in search of one fish that reappeared in 1991.
The group kayaked more than six miles just south of Jackson searching for the robust redhorse.
This rare sucker species grows as long as 28 inches and weighs up to 18 pounds (it’s hard to believe it ever went missing). During spawning season, the redhorse swims upstream from the Altamaha pulled by its strong genetic memory to return to the same breeding ground the species has used for generations.
During breeding, the female lays along the bottom flanked by two males. As she releases hundreds of tiny eggs, the males fertilize them. The eggs sink into spaces between the gravel, which helps protect them. The larvae will remain buried in the gravel for two or three weeks until they can swim.
Surveying for the robust redhorse sounds simple, but it is not a relaxing day on the water. The clean gravel the fish need for spawning is in short supply and it’s found where the water moves the fastest. The path taken by biologists is often neglected because it is treacherous. But for as much time as they spend navigating the rushing water for a glimpse of the large suckers, they also crawl, dragging kayaks under fallen trees that lay across the river.
And often they don’t see any robust redhorse at all, like on this outing.
Why care about such a rare fish? Marcinek was quick to answer. “I see the robust redhorse as a keystone species. If we can protect habitat for this one species, we will help many more species from Brunswick all the way to Jackson.”
DNR biologist Paula Marcinek with a robust redhorse on the Ocmulgee (Peter Dimmick/DNR)
Sediment buildup has greatly reduced the available spawning habitat, and in turn the number of robust redhorse. But sediment buildup isn’t the only reason for the fish’s decline. The migration route for robust redhorse has been blocked in many places. In Juliette, the Ocmulgee is split by a dam separating the fish from their spawning grounds.
Conserving the robust redhorse is a game of catch up. There is so much to rediscover about this long-lost species. Techniques such as tagging fish help reveal their movements and preferred habitats, while surveys, such as the one in May on the Ocmulgee, help estimate how many robust redhorse are left and the quality of their habitat.
The robust redhorse is endangered in Georgia and is a candidate species for listing under the federal Endangered Species Act. Research and conservation efforts are made possible by a range of partners. Visit the Robust Redhorse Conservation Committee website to learn more. Georgia Public Broadcasting’s Georgia Outdoors also profiled the fish and recovery work in its episode “Mystery Fish.”
HOW YOU CAN HELP
The future of the robust redhorse resembles the water it inhabits: troubled, murky and shifting. But there is hope. Reducing your sediment runoff at home is a tangible way to help aquatic life in any watershed. Here are some tips:
- Create a rain garden to filter sediment runoff and help stem flooding.
- For “hardscaped” areas, use permeable materials that allow water to filter through to the soil.
- Cover bare soil with mulch or groundcover.
- Collect excess runoff in a barrel or other receptacle for reuse.
- Add native trees and shrubs to landscapes to reduce erosion.
DNR’s Paula Marcinek and crew surveying for robust redhorse on the Savannah River (Alan Cressler)
NEW GRANT GROWS RESEARCH
Studies to conserve robust redhorse will continue and even be expanded in Georgia and the Carolinas through a new $638,500 grant. The Competitive State Wildlife Grant from the U.S. Fish and Wildlife Service will extend monitoring supported by a similar grant since 2017. But the 2022 award, matched by $220,500 from the states, will also include sampling for the species’ DNA in the Oconee River and analyzing the otoliths (ear bones) of robust redhorse skeletons at the Georgia Museum of Natural History to see how long the fish lived – data that can help guide management. Grant project summaries.
Ethan Hatchett is a communications assistant in DNR’s Wildlife Conservation Section.