When large numbers of paddlefish turned up near the spillway in the Sam D. Hamilton Noxubee National Wildlife Refuge, investigators at Mississippi State University were left scratching their heads at the species’ presence in the system. Considering the species’ typical habitat of deeper and bigger lakes and rivers, the spillway isn’t exactly what most researchers would consider an ideal habitat.
Paddlefish are large fish that date back to about 70 million years ago, with a current record size of around 140 pounds. The Missouri Department of Conservation describes paddlefish as a shark-like fish with “a greatly elongated, paddle-like snout.” The snout on smaller examples of the species is more than one-third of the fish’s total length. Adult paddlefish have no teeth and forward-set eyes with no scales other than a patch on the tale.
American paddlefish are native to the Mississippi River Basin, often found in the open waters of big rivers, swimming close to the surface and constantly on the move, meaning the species likely does not have a specific home range. Considering their regular migration and habitat choices, their residence in the small spillway surprised the researchers who have set up a study to investigate further. They are hoping to garner population size estimates and determine what factors drew the fish to the area in the first place.
In order to understand migration patterns, Mississippi State scientists tagged 30 of the fish with acoustic tags. These tags will communicate data to sensors spread throughout the Noxubee River, wherein scientists are ready to retrieve and analyze the information. These tags will help explain where the paddlefish come from and where they are going once they’ve left the refuge area.
Since the Mississippi River Basin includes Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi and Louisiana, the paddlefish found in the Noxubee have been spotted as far as the Tombigbee River in Tennessee. This inter-state tracking is a result of researchers and agencies from multiple states working together to learn more about the species.
Since paddlefish have never been spotted in such high densities in a small system like that of the Sam D. Hamilton Noxubee National Wildlife Refuge spillway, investigators aren’t sure what to expect from the population. There are concerns about how these unideal habitats might impact fish health and overall population distributions. Paddlefish are a particularly sensitive conservation topic as American paddlefish are the only paddlefish left in the world after Chinese paddlefish were declared extinct in 2020.
Investigators suspect that the spillway’s management creates good water quality conditions that attract the fish. This lure leads the species to stray from historical migration patterns and stay in the waterway throughout the year. Since the small system is not the best-suited environment for large fish like paddlefish, there are concerns that this new trend will impact population sizes in an already endangered species.
According to the Missouri Department of Conservation, much of the damage done to paddlefish populations can be attributed to dams, “stream channelization, levee construction, and drainage of bottomlands.” Dams prevent the fish from reaching spawning sites upstream, inhibiting the continuation of the species organically. Poor spawning statistics have created a reliance on human-run hatcheries and stocking efforts as the species cannot reach the “open, free-flowing rivers, oxbows and backwaters needed for feeding and gravel bars for spawning.”
In hopes of understanding the ties between water quality and paddlefish presence, researchers have installed sensors that monitor the spillway’s temperature, water levels and flow. With any luck, the data will correlate with paddlefish populations which could later help to inform management in fisheries throughout the basin. Paddlefish have historically been overfished for caviar, and the population has suffered greatly–these new management methods may help stabilize populations throughout the basin.