AUTHORS: Charles W. McDunn1, Brent A. Murry2, James E. Garvey3, Ruairi MacNamara4, David C. Glover5, David P. Coulter1
ABSTRACT: The invasion of bigheaded carps, Silver carp (Hypophthalmichthys molitrix) and Bighead carp (Hypophthalmichthys nobilis), has undoubtedly altered biotic communities since their escape from wastewater treatment ponds and aquaculture facilities in North America during the 1970’s. Concerns of the invasion reaching the Laurentian Great Lakes have caused extensive management actions including contracted removal in order to slow the advancement of these fishes in the Illinois River. An additional goal behind the removal of carp is to improve ecological function from its current carp-dominated status. Here, we suggest that it may be useful for community-based alternative indicators to be used in addition to catch rates for more comprehensive management assessments. We will explore this concept using size spectra as a potential indicator of community response to management by examining whether shifts in the annual size spectra regression of six reaches in the Illinois River can be detected since the start of our sampling period in 2012. If shifts in these metrics are measured, they could be related to environmental variability, and the ongoing selective harvest of invasive carps throughout the river. To determine the impact of these factors, we will compare multivariate environmental data and carp removal data to the size spectra metrics using ordination. The results of these analyses will identify which environmental variables are the most impactful to changes in community structure and to what extent the removal efforts have had on the Illinois River fish community over the past twelve years. If the annual community size spectrum is capable of measuring community response to management, it could be an additional tool for assessing and informing management actions and a potential tool for future community-minded management plan development.
