Aquaculture of white-legged shrimp (Litopenaeus vannamei) in low-salinity ponds is a small but growing industry in the southeastern United States. High variabil ity in survival among ponds has been linked to variation in thermal regimes. Water temperatures in July and August can periodically reach and/or exceed 36 ºC in commercial shrimp production ponds, which are typically two meters in depth and can heat up considerably by late afternoon. In this study, we examine the physiological basis of thermal tolerance in shrimp using the concept of aerobic scope - the difference between the metabolic rate required for basic maintenance of an organism (resting metabolic rate: RMR) and the maximum metabolic rate an organism is capable of (potential metabolic activity: PMA). As aerobic scope increases, organisms can potentially utilize more energy for growth and reproduction. We hypothesize that aerobic scope can be used to predict optimal and lethal temperatures for shrimp, with optimal growth occurring at temperature(s) where aerobic scope is maximized and morality occurring at temperatures where aerobic scope approaches zero. To test the concept of aerobic scope, w e exposed shrimp to temperature changes at a rate of 1°C/hr across a range of 20 - 42°C. At each temperature, we used intermittent respir ometry to estimate RMR and the electron transport system (ETS) assay to estimate PMA. Aerobic scope was calculated as the difference between RMR and PMA. Critical thermal maximum (CTM) was estimated as the temperature at which shrimp could be flipped over and were unable to right thems elves for at least 30 seconds. Upcoming experiments will measure growth at multiple temperatures. Data is currently being analyzed to estimate aerobic scope of L. vannamei and to test whether aerobic scope assays can serve as a useful tool to estimate optimal and lethal temperatures for shrimp in aquaculture systems.