Author ORCID Identifier

https://orcid.org/0000-0003-1037-6258

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

Carol Arantes

Committee Member

Patricia Mazik

Abstract

Invasive species have the potential to dramatically change both aquatic and terrestrial ecosystems with rates of introduction only expected to increase across the Globe. In the Mississippi River basin filter feeding silver (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) collectively known as invasive carp were introduced into aquaculture ponds where they subsequently escaped and spread to interconnected basins. Invasive carp have not yet completely established throughout the entire Ohio River. Managers recognize three distinct phases of carp invasion: establishment front, invasion front and presence front. In the Illinois River invasive carp are very well established and have reduced total zooplankton density almost completely eliminating larger zooplankton (copepods and cladocerans) from the system. Zooplankton play important roles in aquatic ecosystems by connecting primary producers (phytoplankton) to secondary consumers (fish). In addition, zooplankton serve as an important food source for larval fish that are unable to consume other sources of food due to their size. Without zooplankton or with a greatly depressed zooplankton density native fish may not have enough resources and can potentially lead to a food web collapse as the food web is disconnected from primary producers with energy sequestered in large filter feeding invasive carp. The purpose of my thesis is to assess current effects of invasive carp on zooplankton in the Ohio River.

In Chapter 1, I compare zooplankton communities across the three carp invasion fronts to establish effects. Additionally, I compare my sampling conducted in 2021-2022 to a historical baseline from 1991-1992 to assess potential changes in the relative abundance of taxonomic composition of zooplankton assemblages over the past 30 years. I did not find differences in zooplankton community composition across the different carp invasion fronts. However, large-bodied copepods were more abundant and emerging earlier throughout the year while smaller-bodied rotifers were less abundant. Another notable change was the dominating presence of zebra mussel larvae that were absent in earlier data set.

In Chapter 2, I used Normalized Biomass Size Spectra, an ataxic approach that expresses community structure as a function of body size instead of taxonomic identity to assess potential effects of invasive carp on zooplankton. Additionally, I looked at seasonality of the NBSS model and how it changed throughout the season. I did not find significant differences of NBSS models across carp invasion fronts, although the nonsignificant differences were consistent with our hypothesis. NBSS models did change throughout the year and followed along with typical observed zooplankton phenology

In chapter 1 I looked at Ohio River zooplankton from a taxa based approach while in chapter two I used a body size based approach. In both chapter one and two I looked at the effects of invasive carp on the Ohio River zooplankton community, however, in chapter one I used a taxa-based evaluation while in chapter two I used a body size-based evaluation. I did not find any effect of invasive carp to either zooplankton body size or taxa in the section of the Ohio River I sampled. Both chapters suggest that densities of invasive carp have not reached the threshold required to produce negative effects on the zooplankton community.

Download

Share

COinS