The Effectiveness of Carbon Dioxide As a Barrier to Prevent Fish Movement

Aquatic invasive fishes in the Midwest have a potential for wide-ranging impacts due to the interconnectedness of watersheds.  Of particular concern is the artificial connection between the Mississippi River basin and the Great Lakes via commercial shipping waterways, specifically the Chicago Area Waterway System.  Bigheaded carps have established themselves in the upper reaches of the Illinois River, and significant efforts have been made to prevent their further spread towards Lake Michigan.  Currently, three electric barriers are in place and serve to prevent fish passage through this waterway.  To provide redundancy and increase the likelihood of stopping the spread of carp into the Great Lakes, carbon dioxide (CO₂) is being investigated as a potential nonphysical barrier.  Here, we first review some of the work that has been done to define the potential of CO₂ as a fish barrier, as well as highlight several projects related to the potential impacts of CO₂ on fish behavior.  We also detail recent experiments designed to define the responses of fish in flowing water to CO₂ exposure. Together, data help define the potential for CO₂ to act as a non-physical deterrent to fish movement, and highlight work that has been done to refine and guide application.