Influence of Dissolved Oxygen and Carbon Dioxide on Swimming Performance of Largemouth Bass and Coho Salmon

The final swimming speed of juvenile largemouth bass, Micropterus salmoides (Lacepede), was reduced markedly at oxygen concentrations below 5 or 6 mg/liter in tests at 25 C in a tubular chamber in which the velocity of water was increased gradually, at 10-min intervals, until the fish were forced by the current permanently against a screen. At levels above 6 mg/liter, the final swimming speed was virtually independent of the oxygen concentration. The performance of bass that had been acclimated overnight to elevated carbon dioxide levels was not materially affected by the highest tested concentrations of free carbon dioxide, averaging 48 mg/liter, at any tested level of dissolved oxygen.For juvenile coho salmon, Oncorhynchus kisutch (Walbaum), at temperatures near 20 C and carbon dioxide concentrations near 2 mg/liter, any considerable reduction of the oxygen concentration from about 9 mg/liter, the air-saturation level, resulted in some reduction of the final swimming speed. The performance of the salmon...