Examining Bigheaded Carp Ichthyoplankton Drift in Tributary and Mainstem River Systems of Two Midwestern Rivers

Abstract

The bigheaded carp invasion in North America continues to negatively impact ecosystems making it essential to understand their reproductive dynamics at various spatial scales. Previous studies have highlighted the suitability of tributaries of large rivers for bigheaded carp reproduction, and the importance of tributaries for ichthyoplankton drift to mainstem rivers. This study investigated patterns in tributary-mainstem ichthyoplankton drift dynamics in two invaded river systems of the Midwestern United States, with distinct hydrology, the Illinois and Wabash Rivers. From May-September 2021, I sampled ichthyoplankton from three tributaries and three mainstem sites in each river basin. I analyzed bigheaded carp egg and larval presence/absence and drift (ichthyoplankton/s) in relation to location type and basin spatial variables to assess the tributaries’ contribution to mainstem ichthyoplankton drift and to examine differences between two river basins. Results showed that tributaries contributed substantially to mainstem bigheaded carp egg drift in the Illinois basin but not in the Wabash basin. Tributaries did not contribute substantially to mainstem larval drift in either basin in 2021. Overall, the Illinois basin had higher levels of bigheaded carp ichthyoplankton drift than the Wabash basin. This study demonstrates that tributaries can serve as important sources of and thoroughfares for bigheaded carp egg drift to large mainstem rivers. However, the relative contribution of tributary-sourced eggs to later stages of development remains unclear. Further elucidating variations in drift patterns between tributaries and mainstem rivers over multiple years is necessary to gain a comprehensive understanding of bigheaded carp reproduction within metapopulations.

Date of Award	2024
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Eden L Effert-Fanta (Supervisor)