Responses of native and invasive fishes to carbon dioxide: potential for a nonphysical barrier to fish dispersal

Upon arrival in a novel environment, invasive species have the potential to cause negative consequences at their new location. Rather than try to eliminate invasive species after introduction, preventing their spread is a more efficient strategy to mitigate impact. The current study used a laboratory setting to quantify the efficacy of elevated carbon dioxide (CO2) in water to act as a nonphysical barrier to deter fish movement. Our focus was on deterring the movements of silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), but largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) were also examined to quantify the impact of elevated CO2 on native species. Exposure of all species to 30 mg.L-1 dissolved CO2 for 1 h, compared with ambient CO2 concentrations of 10 mg.L-1, resulted in an elevated stress response, along with alterations to ionic-osmotic balance. Exposure of fish to 70 mg.L-1 CO2 caused a reduction in ventilation rates after 1 h, while both silver carp and bighead carp lost equilibrium. Silver carp, largemouth bass, and bluegill also showed avoidance of CO2 at approximately 100 mg.L-1. Together, results suggest that zones of elevated CO2 have potential to deter the movement of fishes.