Habitat use of the threatened river redhorse (Moxostoma carinatum) in the Grand River, MI, USA

The resilience of aquatic ecosystems hinges on our ability to protect the native species that reside within them. The river redhorse (Moxostoma carinatum) is one such example and populations have become low enough to warrant a threatened status by the State of Michigan. An insufficient understanding of the species' habitat use outside of its spawning season hinders the ability of fisheries managers to implement appropriate habitat protection and restoration measures. To enhance our understanding of river redhorse habitat use, we implanted 15 individuals with radio transmitters during the spring spawning run and tracked their locations over the course of a summer. River redhorse movement varied greatly with some individuals remaining within the spawning area throughout the summer and others traveling as far as 50 km down river. Once post-spawn movement ceased, river redhorse established themselves in small home ranges between 0.04 and 0.12 km(2). We found no obvious selection for depth, sediment type, macrophyte presence, or water velocity. Instead, river redhorse strongly selected for habitat containing freshwater mollusks, the primary food source for the species. This suggests that they were seeking foraging habitat during this time period. These findings provide insight into river redhorse management, indicating that the recovery of the species may depend on our ability to protect these newly discovered feeding areas. Future river redhorse management efforts should therefore focus on the protection of native mussels and snails and the maintenance of migration routes between spawning and summer habitats.

Automated summary

The river redhorse is a threatened species in Michigan. However, there is a lack of understanding of its habitat use outside of the spawning season. Research showed that river redhorse exhibited varying movement patterns during the summer, but established small home ranges after spawning. They strongly selected habitat with freshwater mollusks as a food source. Protecting these newly discovered feeding areas is crucial for the recovery of the species.