Assessment of carbon dioxide as barrier to Bigheaded carp

Science Center Objects

Currently, prevention of the movement of bigheaded carps from the Mississippi watershed into the Great Lakes rests on a single electric barrier located in the Chicago Area Waterway System (CAWS).  Additional barriers and/or supplements to the electric barrier would improve the efficacy of deterring bigheaded carps movement into the Great Lakes through redundancy and ‘safety nets’, and offer greater confidence in their containment.  For example, development of a chemical barrier that generated noxious water conditions might repel bigheaded carps, preventing them from approaching the electric barrier.

Some work has been done to define biological limits and potential benchmarks for candidate chemicals that may serve as a non-physical barrier to deter the movement of bigheaded carps.  One candidate barrier chemical that has received a great deal of attention has been carbon dioxide gas (CO2).  Adding CO2 to water has two main effects: (1) a reduction in pH due to the formation of carbonic acid (a weak acid), and (2) elevation of dissolved CO2 (hypercarbia).  The ability of animals to sense environmental CO2 is highly conserved, and is common across kingdoms, spanning both prokaryotes and eukaryotes.  

A large-scale pond trial to assess behavioral response of bighead carp, silver carp and non-target fishes (bigmouth buffalo, channel catfish, paddlefish and yellow perch) has been completed. Results from this trial demonstrated that all fish avoided the area where CO2 was injected until the pond was saturated. This study demonstrated the potential to deliver CO2 to a large body of water. A second study evaluated the use of CO2 in a scaled version of the Brandon Road approach channel. This study validated that when CO2 was injected into one side of the channel, fish would avoid areas near the CO2 barrier and occupied the area with the lowest CO2 concentration. The goal of the next phase of this project is to determine if fish will avoid a CO2 when injected into a system of a size similar to an approach channel associated with a lock.  


  1. Determine efficacy of a CO2 as a barrier to bigheaded carp.
  2. Describe changes in the spatial occupancy of bigheaded carps when CO2 is deployed as a barrier.
UMESC scientist Nate Jensen holds bighead carp (invasive species) on the Illinois River, 2011

UMESC scientist Nate Jensen holds bighead carp (invasive species) on the Illinois River, 2011(Credit: Jon Amberg, USGS UMESC. Public domain.)