Rusty Crayfish (Faxonius rusticus) Interactions with Benthic Macroinvertebrates in the Monocacy River

Abstract

The rusty crayfish (Faxonius rusticus) is an invasive species with origins in the Midwestern Unites States, that has the capacity to alter benthic macroinvertebrate community structure through predation. Since 2007, Faxonius rusticus migrated downstream in the Monocacy River, establishing its presence as one of the predominant crayfish species in certain areas of the river. I analyzed changes in benthic macroinvertebrate communities in 2016 and 2021 at sites with and without a presence of Faxonius rusticus using biodiversity, density, and biomass as biological metrics. No significant changes in these metrics were detected in comparisons of with and without Faxonius rusticus. Some significant differences were detected between habitats. Additionally, macroinvertebrate taxonomic composition was not statistically significant across treatments with the exception of one genus. The lack of changes in macroinvertebrate communities is likely attributed to the significant decline in densities of Faxonius rusticus over the past five years. Because of this decline, I hypothesize that rates of predation by Faxonius rusticus are not high enough to be detected by field sampling in the Monocacy River.