Investigators at Mississippi State University say that it’s important not to underestimate different habitat types after finding prehistoric fish near the spillway in the Sam D. Hamilton Noxubee National Wildlife Refuge. They have found unexpectedly high numbers of paddlefish, a fish typically found in larger waterways.
Paddlefish are large fish that date back about 70 million years ago. American paddlefish are native to the Mississippi River Basin, so their residence in the small spillway came as a surprise to the researchers who have set up a study to investigate further. They are hoping to garner estimates of population size and to determine what factors drew the fish to the area in the first place.
To get at those questions, Mississippi State scientists have tagged 30 of the fish with acoustic tags that will trigger sensors in place along the Noxubee River. Each fish tag has a special ID so that tracking their movements will be simple. If the paddlefish are migrating, they will be recorded in different geographic areas, giving researchers a better idea of where they’re coming from and their usual migration pattern.
Collaboration with the Alabama Game and Fish Division has allowed the researchers to track the fish even as they move into the Tennessee-Tombigbee River. They have set up sensors within Alabama that share data with those in Mississippi, allowing scientists to gauge just how far the fish are traveling.
Because paddlefish have never been seen in such high densities in a small system like this one, investigators aren’t sure what to expect from the population. However, they suspect that the spillway’s management creates conditions that attract the fish so they may veer off course from their traditional migratory route and end up staying through the year. That could create problems for the species, which already is endangered and even extirpated in parts of the United States due to overfishing for caviar.
To look for correlations between water conditions and paddlefish presence, sensors have also been installed in the spillway to monitor temperature, water levels and flow. With any luck, the instruments will reveal a link between spillway conditions and paddlefish behavior and explain in part why they’re drawn to the area.
Once the fish are there, investigators are also hoping to see if they’re spawning or not. If the fish are being drawn to the area and then not spawning, or just not spawning successfully, that could have large implications for the diversity of the species.
Sampling has revealed a few pregnant females so far this season, but not any young paddlefish. The next step for the work depends on what scientists discover. If it appears that paddlefish are successfully spawning near the spillway, refuge managers may undertake habitat restoration efforts to help ensure the population’s success. But if the fish aren’t spawning, or the young are being eaten by predators, managers will look for ways to change the spillway so the prehistoric fish aren’t drawn to it.
Funding for the project is provided by the U.S. Fish and Wildlife Service and the U.S. Geological Survey’s Quick Response Program.