Author ORCID Identifier

https://orcid.org/0009-0001-3117-7824

Semester

Summer

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Caroline Chaves Arantes

Committee Co-Chair

Brent A. Murry

Committee Member

Friedrich W. Keppeler

Abstract

Invasive species can cause measurable impacts on the properties of recipient ecosystems, with effects that often vary spatially and temporally. One of the most complex and pressing invasion cases in the United States involves invasive carp. Invasive carp have quickly expanded throughout the Mississippi River Basin, with ecological impacts that may vary across space and time. Silver Carp has the potential to provoke community-wide impacts on native fish abundances and food webs of native fish communities. My study area ranged from the confluence of the Mississippi River and the Ohio River to R.C. Byrd Lock and Dam. The Ohio River is divided into sections that reflect invasion status of invasive carp based on differences in density, reproduction, and recruitment. Fish assemblage data used in this study are part of a long-term monitoring program conducted by the Ohio River Valley Water Sanitation Commission (ORSANCO). I utilized data from 2015 to 2023 collected through annual fish surveys to assess taxonomic and trophic guild structure variation in response to Silver Carp relative abundance. I used distance-based and multivariate model-based analysis to detect species-specific and trophic guild-specific changes in abundance. pRDA results suggest that Silver Carp explains little variation in fish (0.47%) and trophic guild (0.17%) communities. Several species were positively associated with increasing Silver Carp relative abundance (RA): Moxostoma erythrurum (0.006), M. anisurum (0.005), Lepomis macrochirus (0.004), Dorosoma cepedianum (0.004), Sander canadensis (0.003). Conversely, some species were negatively associated with increasing Silver Carp RA, including Morone chrysops (-0.0055), Ictalurus punctatus (-0.005), Cyprinella spiloptera (-0.004), Micropterus dolomieu (-0.004) and Notropis atherinoides (-0.004). These results suggest that the effect of spatial and temporal components are important drivers of fish (9.9% total variation) and trophic guild community (8.2%) structuring in the Ohio River. pRDA results indicate no statistically significant change in trophic guild levels composition (p-value = 0.22). Modeling indicates that Silver Carp may have negatively impacted Mississippi silvery minnow (Hybognathus nuchalis), Smallmouth bass (Micropterus dolomieu), White bass (Morone chrysops), and primary and tertiary consumers. The use of species and trophic guild responses to assess community-wide impact allowed for a better understanding of overall patterns of response at an assemblage level. Our results suggest that Silver Carp are not yet impacting fish or trophic guild communities in the Ohio River, as we only observed weak associations and limited species-level responses. We recommend future research to account for factors such as land use, temperature, hydrological variables and habitat availability as previous research suggests these factors to be key drivers of community structuring reflecting the river natural longitudinal gradient in the Ohio River. Finally, we encourage the use of approaches that consider not only species identity but also trophic guilds, as these complementary approaches can provide more accurate insights on ecological impacts.

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