Chelsea M. Center

Western Illinois University

1 University Circle

Macomb, Illinois 61455

(309) 530-2977

Invasive fish species are a problem across the United States. Currently, the most widely recognized invaders in the Mississippi River Basin are silver and bighead carp collectively known as bigheaded carp. Silver carp caught the attention of the media and public because of their predator avoidance strategy of leaping from the water when they feel threatened. This behavior becomes a spectacle when boaters pass through a school of silver carp and there are suddenly hundreds of fish launching themselves into the air. The physical threat to boaters is not the only peril posed by bigheaded carp. Both silver and bighead carp are extraordinarily efficient planktivores which means they filter feed phytoplankton and zooplankton out of the water column. In the areas where bigheaded carp densities are the highest, populations of phytoplankton and zooplankton have decreased which is concerning because these microscopic organisms are a primary food source for young fish. Likewise, native planktivores are also suffering because of bigheaded carp introduction. For example, the body condition of bigmouth buffalo and gizzard shad decreased as a result of the presence of bigheaded carp. This is significant because bigmouth buffalo are a commercially fished species and gizzard shad are a food source for many native fish species. Because bigheaded carp have the potential to economically and ecologically damage aquatic systems, their presence must be managed. Monitoring the spread of bigheaded carp has been a priority since their introduction and particularly important in the last decade as efforts to prevent them from entering Lake Michigan gained momentum. The drive to keep bigheaded carp out of Lake Michigan is compelling because the lake ecosystem is already struggling against the effect of human stressors like pollution and other invasive species like zebra mussels, sea lampreys, and round gobies.

A joint effort between the Department of Biological Sciences at Western Illinois University, the United States Geological Survey, and the Illinois Department of Natural Resources collaborated to track bigheaded carp using new technology. The project’s primary objective was to determine if this technology, GPS satellite tags, could be successfully used in a river system. Tags capable of gathering and sending GPS coordinates to satellites were attached to bigheaded carp. Previously, GPS satellite tags had only been used in marine settings to tag and record locations of animals that come to the surface to breathe or feed like sea lions, sea turtles, and ocean sunfish. Because GPS satellite tags only collect and send information when the tags are at the surface, bigheaded carp seemed to be a good candidate for this technology since they feed and spawn near the surface. GPS satellite technology allows for the tracking of an individual fish 24 hours a day, 7 days a week for the length of the battery life of the tag which is between 60 and 80 days on average. The traditional technology used to track bigheaded carp requires someone to be on the river to actively track fish or download information from stationary receivers while the GPS satellite technology allows a biologist to track fish movement from anywhere that has internet access. This equates to fewer hours needed to collect information and the collection of more timely information.

Seven GPS satellite tags were deployed in August 2017 in a 15 mile stretch of the Upper Illinois River about 50 miles southwest of Chicago. This technology allows minute movements of tagged bigheaded carp to be monitored in the section of the river closest to Lake Michigan with a population of carp. All seven tags collected location information and transmitted it. About 185 fish locations were collected and plotted so that areas of fish congregation could be noted. Deployment of the seven tags confirmed the technology works in a river system and that areas of congregation could be detected (Figure1). The white circles are areas where bigheaded carp tend to congregate and removal efforts would best be focused in an attempt to control the population. While some limitations were discovered, GPS satellite tags proved to be a useful tool to inform management efforts.

Figure1. This is the lower third of the study area with fish locations plotted. Each color represents a different fish. The white circles are areas of congregation.