Benefits and detrimental effects of ocean warming for Tasmanian salmon aquaculture

Atlantic salmon (Salmo salar) is the main aquaculture species in Tasmania, Australia. This species is known to be sensitive to ocean temperature and has its own optimal temperature range for exceptional growth. As a hotspot of ocean warming, adaptation planning may be necessary for Tasmanian salmon aquaculture industries in coming years. In this study, we used high-resolution sea surface temperature (SST) satellite observations to investigate ocean temperature variability and trends in the southeastern Tasmania over the past 28 years, and their impacts on growth suitability for sea-farmed Atlantic salmon using a metric called optimal days. We found that long-term ocean warming in the region was evident but showed both positive and negative effects on optimal days. Winter warming would make salmon farms more suitable for salmon growth, while summer warming would make it too warm to grow optimally, which could lead to increased fish disease and even death. This seasonal difference also explained the year-to-year variability in the number of optimal days. Furthermore, spatial distributions of optimal day anomalies indicated that some farm regions were affected more than the others. Northern regions are becoming unsuitable for salmon aquaculture, while southern regions are still optimal for salmon growth in the next few decades. These findings demonstrate the complexity of consequences of global warming for salmon aquaculture industries, and can help stakeholders to develop a blue print for strategizing future farm development and climate change adaptation plans.