Elevated carbon dioxide has the potential to impact alarm cue responses in some freshwater fishes

Freshwater fish behaviors have the potential to be impacted by acidification due to increases in dissolved carbon dioxide (CO₂). Recent work in the marine environment suggests that increased CO₂ levels due to climate change can negatively affect fishes homing to natal environments, while also hindering their ability to detect predators and perform aerobically. The potential for elevated CO₂ to have similar negative impacts on freshwater communities remains understudied. The objective of our study was to quantify the effects of elevated CO₂ on the behaviors of fathead minnows (Pimephales promelas) and silver carp (Hypophthalmichthys molitrix) following exposure to conspecific skin extracts (alarm cues). In fathead minnows, their response to conspecific skin extracts was significantly impaired following exposure to elevated CO₂ levels for at least 96 h, while silver carp behaviors were unaltered. However, fathead minnow behaviors did return to pre-CO₂ exposure in high-CO₂-exposed fish following 14 days of holding at ambient CO₂ levels. Overall, this study suggests there may be potential impacts to freshwater fishes alarm cue behaviors following CO₂ exposure, but these responses may be species-specific and will likely be abated should the CO₂ stressor be removed.