Predation of freshwater fish in environments with elevated carbon dioxide

Abstract

Carbon dioxide (CO2) in fresh-water environments is poorly understood, yet in marine environments CO2 can affect fish behaviour, including predator–prey relationships. To examine changes in predator success in elevated CO2, we experimented with predatory Micropterus salmoides and Pimephales promelas prey. We used a two-factor fully crossed experimental design; one factor was 4-day (acclimation) CO2 concentration and the second factor CO2 concentration during 20-min predation experiments. Both factors had three treatment levels, including ambient partial pressure of CO2 (pCO2; 0–1000 μatm), low pCO2 (4000–5000 μatm) and high pCO2 (8000–10000 μatm). Micropterus salmoides was exposed to both factors, whereas P. promelas was not exposed to the acclimation factor. In total, 83 of the 96P. promelas were consumed (n=96 trials) and we saw no discernible effect of CO2 on predator success or time to predation. Failed strikes and time between failed strikes were too infrequent to model. Compared with marine systems, our findings are unique in that we not only saw no changes in prey capture success with increasing CO2, but we also used CO2 treatments that were substantially higher than those in past experiments. Our work demonstrated a pronounced resiliency of freshwater predators to elevated CO2 exposure, and a starting point for future work in this area.