Exposure to Elevated CO2 Alters Diel Movement Patterns of Largemouth Bass over Short Time Scales

Studies with marine fishes indicate that exposure to elevated partial pressures of CO₂ (pCO₂) related to climate change have consequences for fish behavior.  Freshwater fishes may experience similar increases in pCO₂, but there is a paucity of information on how freshwater fishes may respond to elevated pCO₂. To define the effects of elevated pCO₂ on free-swimming freshwater fish, 19 adult largemouth bass were tagged with acoustic transmitters, held in water with elevated pCO₂ levels of either ~10,000 µatm or ambient pCO₂ (< 100 µatm) for five days, and released into a naturalized, earthen-bottom pond outfitted with an acoustic telemetry array.  Findings indicate that largemouth bass not exposed to elevated levels of pCO₂ decreased movement over 35% during the daylight periods; however, fish exposed to elevated levels of pCO₂ did not exhibit this pattern.  This difference in diel movement patterns between fish exposed to elevated pCO₂ and fish not exposed was not detectable after 11 days.  Space-use did differ slightly for fish exposed to elevated pCO₂. Exposure to elevated pCO₂ therefore can have consequences for some movement behaviors of freshwater fishes and this may influence a variety of ecological processes.