Author ORCID Identifier

https://orcid.org/0009-0008-0058-6511

Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Brent Murry

Committee Member

Caroline Arantes

Committee Member

Andrew Stump

Abstract

The introduction of silver carp (Hypophthalmichthys molitrix) has had dramatic effects on native fish communities. Silver carp are large bodied planktivores and compete with native planktivores which can cause cascading effects throughout the food web. Our study strives to determine the threshold of abundance beyond which silver carp alter fish community structure. We used a community size spectra approach to evaluate fish community structure and compare size spectra across spatial and temporal gradients of silver carp abundances. Community size spectra (CSS) is an ataxic approach quantifying the predictable decrease in fish abundance with increasing body size that reacts predictably to many ecosystem stressors. For example, fishing exploitation tends to steepen the slope of size spectra due to the removal of large-bodied fish. We predict that silver carp will cause a flattening of the size spectra slope because they are large-bodied but feed low on the food chain. Data provided by the Kentucky Department of Fish and Wildlife Resources and the Illinois Natural History Survey include fish lengths and weights derived from electrofishing surveys in four pools of the Ohio River and the La Grange pool of the Illinois River. Electrofishing was conducted from 2015 - 2020 for the Ohio River and 1994 - 2021 for the Illinois River. Results show the Illinois River CSS has changed predictably in response to the invasion of silver carp. While there has been an increase of silver carp in the Ohio River, management and removal may have kept them below the threshold where they would impact CSS. While specific removal targets were not obtained from using CSS, CSS alongside adaptive management could be used for the management of silver carp.

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