Tasmanian Atlantic salmon (Salmo salar) are cultured in the warmest summer temperatures in the world. During the summer months, farmed salmon in Tasmania can experience warming of up to 23°C and concurrent intermittent periods of hypoxia. As associated with these environmental stressors, fish respond through a reduction or complete cessation of feeding to affect growth, overall condition and product quality. Individual responses to these conditions can vary substantially within a closely related population of Atlantic salmon, whereby some individuals are better able to maintain performance through and/or recover from periods of summer stress and others are not. The distribution of phenotypes and the degree of phenotypic plasticity within a population will contribute to the summer performance of Atlantic salmon in Tasmania. As part of this research, we show how plasticity in the digestive system of Atlantic salmon is associated with superior summer growth performance. These data show for the first time how the fish gut phenotype might influence an individual’s capacity for environmental plasticity and resilience in aquaculture. Identifying traits associated with superior summer performance will be necessary to inform selective breeding programs and mitigate the continued impacts of climate change on Tasmania’s billion dollar salmon industry.