EFFECT OF SUMMER TEMPERATURES ON AEROBIC AND ANAEROBIC METABOLISM IN CULTURED JUVENILE RED DRUM, <i>Sciaenops ocellatus</i>
As ectotherms, temperature is critical in determining the aerobic metabolic rate of fishes. However, the influence of temperature on anaerobic metabolism is less clear. In particular, the amount of anaerobic metabolism fish utilize in response to exhaustive exercise across temperatures is not well studied. Red drum, a common Western Atlantic species, reside in estuaries during their juvenile years and are commonly exposed to a wide range of temperatures, including relatively high temperatures during summer months. This study investigated the impact of temperature on cultured juvenile red drum aerobic and anaerobic metabolism in a range of ecologically relevant summer temperatures (24ºC, 27ºC, 30ºC, and 33ºC). Specifically, this study tested two hypotheses: 1) juvenile red drum aerobic scope would increase with temperature and 2) juvenile red drum use a higher contribution of anaerobic metabolism to support exercise at high temperatures. Mean routine metabolic rate ± S.E.M. increased from 13.5 ± 0.67 mmolO<sub>2</sub> kg<sup>−1</sup> h<sup>−1</sup> at 24ºC to 17.5 ± 0.89 at 33ºC. Maximum metabolic rate increased from 41.8 ± 1.33 mmolO<sub>2</sub> kg<sup>−1</sup> h<sup>−1</sup> at 24ºC to 56.0 ± 2.82 at 27ºC and did not change from 27ºC to 33ºC. Aerobic scope increased significantly from 28.4 ± 1.19 mmolO<sub>2</sub> kg<sup>−1</sup> h<sup>−1</sup> at 24ºC to 40.0 ± 2.73 at 27 ºC and remained high from 27ºC to 33ºC. Resting lactate (6.37 ± 0.45 µmol g<sup>−1</sup>) and mean maximum lactate (79.6 ± 2.17 µmol g<sup>−1</sup>) did not change with temperature. Percent anaerobic contribution of energy expenditure was 35% ± 1.9 and did not change with temperature. Overall, juvenile red drum metabolism was not negatively impacted at 33ºC, suggesting this species is metabolically equipped to tolerate warm water temperatures. However, other factors such as hypoxia or pH shifts should be explored for a better understanding of how juvenile red drum tolerate warm summer seasons as well as future conditions.