MULTI-SPECIES TROPHIC RESPONSE IN TRIBUTARIES OF THE OHIO RIVER ALONG A GRADIENT OF AN INVASIVE PLANKTIVORE

Author

Justin Kowalski, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2023

Degree Name

Master of Science

Department

Zoology

First Advisor

Garvey, James

Abstract

1. Aquatic invasive species often have a gradient of abundance along connected systems as invasion occurs. Invading species effects on native species may not be apparent when the species first colonizes a new area but as abundance of the invader increases they may have detrimental effects to native ecosystems even when not fully established. 2. A gradient of Silver Carp (Hypophthalmichthys molitrix) abundance in the Ohio River exists as invasion has been slowed by the many navigation dams that exist on the river. I examined how the isotopic niche of four native species differed along the Silver Carp gradient in tributaries of the Ohio River using stable isotopes of nitrogen (δ15N) and carbon (δ13C). I also determined if the body condition of native species changed in tributaries of the Ohio River along the invasion gradient using relative weight. 3. Trophic dynamics of Gizzard Shad (Dorosoma cepedianum) and Largemouth Bass (Micropterus salmoides) differed along the Silver Carp gradient. Isotopic niche space was larger and relative weight was lower where Silver Carp were more abundant. Trophic dynamics of Bluegill (Lepomis macrochirus) and Smallmouth Buffalo (Ictiobus bulbus) did not differ along the Silver Carp gradient. Trophic chains were compressed where Silver Carp were abundant compared to where they were rare or absent. 4. Invasive Silver Carp may have community wide effects on native species. However, feeding pathways of native species may play an important role in determining how a native species will be affected by invading Silver Carp as species that belong to the pelagic food web were most affected by Silver Carp invasion. 5. Future research should continue to focus on how native fish species from various trophic positions may be affected by Silver Carp invasion and how Silver Carp invasion plays a role in the complex interactions between biotic and abiotic factors in a complex, altered river system such as the Ohio River.