Fish behavior in elevated CO2: implications for a movement barrier in flowing water

Preventing the spread of invasive fishes is an important aspect of management programs, but is challenging due to the behavior of fish and the nature of aquatic environments. The use of dissolved carbon dioxide (CO2) has recently gained traction as a nonphysical barrier for invasive fishes due to its ability to elicit avoidance behaviors in fish. Research to date has focused on the development of CO2 barriers using static water environments. Because CO2 barriers have been proposed for flowing water (i.e., in rivers or shipping canals), understanding the dynamics between fish and elevated CO2 in flowing water is essential. Our study aims to define threshold levels required to alter behavior of bluegill (Lepomis macrochirus) and largemouth bass (Micropterus sahnoides) in flowing water, and to quantify behavioral metrics of fish exposed to < 200 [ambient], 25,000, 50,000, and 100,000 mu atm pCO(2). We also sought to quantify the impacts of repeated CO2 exposure on fish behavior. Bluegill showed increased activity at 25,000 mu atm, while largemouth bass showed increased activity at 100,000 mu atm. When repeatedly exposed to cycles of 50,000 mu atm pCO(2), bluegill exhibited increased activity followed by a diminished response after the second exposure. Results from this study define threshold levels required to elicit behavioral responses, and show that the effects that multiple exposures of elevated pCO(2) can decline, possibly due to habituation. Results will help shape the development and deployment of a CO2 barrier to control the movements of invasive fishes.