Meeting Abstract
Many estuarine organisms are frequently exposed to high water temperature and the accompanying reduction in water oxygen concentration. High water temperature also increases fish metabolic rate and therefore overall oxygen demand. Both routine and maximum metabolic rates (RMR and MMR, respectively) increase with temperature to maximum values at their optimum temperatures, and then decrease as temperature increases past optimum. Aerobic scope is the difference between MMR and RMR and represents aerobic metabolic capacity that can be used for activities such as locomotion, foraging, and digestion. Thus, reduced aerobic scope at non-optimal temperatures may inhibit physiological performance and alter behavior. This study investigates the effect of high temperature on aerobic scope and swimming performance of juvenile red drum. Oxygen consumption was measured at four temperatures mimicking summer temperatures in South Carolina: 24°C, 27°C, 30°C, and 33°C. Fish were starved, and RMR was measured overnight using respirometry. After RMR measurements, fish were exercised and placed back into the respirometer to estimate MMR. RMR was 13.47 ± 0.67 (mean ± S.E.) mmol kg-1 h-1 at 24°C and increased with temperature to a maximum value of 17.49 ± 0.87 mmol kg-1 h-1 at 33°C. MMR and aerobic scope peaked at 27°C (56.02 ± 2.82 and 39.99 ± 2.73 mmol kg-1 h-1, respectively) and decreased at temperatures lower and higher than this optimum. RMR demanded a larger proportion of the oxygen consumed as water temperatures increased, resulting in decreased aerobic scope. However, aerobic scope did not decrease significantly at the highest temperature tested, and so performance in the wild may not be reduced at high summer temperatures.
