Avoidance of carbon dioxide in flowing water by bighead carp

Carbon dioxide (CO₂) in water has been explored for use as an invasive species deterrent system. To date, studies have not determined CO₂ avoidance by fish in flowing water, and this is a necessary step before an operational deterrent system can be implemented. The objective of the study was to define how flowing water influences the response of bighead carp (Hypophthalmichthys nobilis) to continuous plugs of CO₂. A choice experiment by which CO₂ was injected into channels of an annular flowing water flume was completed. In trials when CO₂ was injected into the inner vein, fish spent less time in the vein when compared with control conditions. An increased amount of lateral movements and reduced performance were also observed when fish were exposed to elevated CO₂. The study demonstrates that bighead carp in flowing water enriched with CO₂ move away, a finding consistent with static water experiments.