Exposure to elevated pCO2 alters post‐treatment diel movement patterns of largemouth bass over short time scales

Abstract

Summary Studies with marine fishes indicate that exposure to elevated partial pressures of CO2 (pCO2) related to climate change have negative consequences for fish behaviour. Freshwater fishes may experience similar increases in pCO2 due to a number of different mechanisms, but there is a paucity of information on how freshwater fishes may respond to exposure to elevated pCO2. To define the effects of elevated pCO2 on a free‐swimming freshwater fish, 19 adult largemouth bass (Micropterus salmoides) were tagged with acoustic transmitters, held in water with pCO2 levels of either ˜10 000 μatm or ambient pCO2 (<100 μatm) for 5 days and released into a naturalised, 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. Changes in home range size and daily distance travelled were not observed. However, based on an assessment of position estimates after the completion of the telemetry monitoring portion of the study, space use differed for fish exposed to elevated pCO2. Exposure to elevated pCO2 therefore can have consequences for some movement behaviours of freshwater fish and this may influence a variety of ecological processes including energetics, foraging and predator–prey dynamics. CO2‐induced alterations to behaviour should recover upon a return to ambient water.