Swimming performance of a freshwater fish during exposure to high carbon dioxide.

Deterring the spread of invasive fishes is a challenge for managers, and bigheaded carp (including bighead and silver carp, Hypophthalmichthys spp.) are invasive fish that have spread throughout large portions of the Mississippi River basin and threaten to invade the Great Lakes' ecosystem. Studies have shown that elevated levels of carbon dioxide gas (CO2) have the ability to act as a nonphysical fish barrier, but little work has been done on the efficacy of CO2 to deter fish movement in flowing water. An annular swim flume was used to measure Uburst and sprint duration of the model species largemouth bass (Micropterus salmoides) across a range of pCO2 levels (< 400 μatm [ambient]; 10,000 μatm; 50,000 μatm; and 100,000 μatm). This species was tested as a proxy because of the likelihood of a similar CO2 response being produced, as well as constraints in obtaining and housing appropriately sized Asian carp. A significant decrease in Uburst swimming occurred when exposed to 100,000 μatm. No effects on sprint duration were detected. In both swimming tests, 15% of fish lost equilibrium when exposed to 50,000 μatm pCO2, while 50% of fish lost equilibrium when exposed to 100,000 μatm. Together, results define target levels for managers to impede the spread of largemouth bass and potentially other invasive freshwater fishes, helping guide policy to conserve aquatic ecosystems.