Atlantic salmon (Salmo salar) aquaculture in a changing climate: Quantitative insights from industry records and climate projections.

Predicting and understanding the implications of climate change on Atlantic salmon (Salmo salar) aquaculture is a fundamental step to understanding risk and mitigating potential impacts. Here, we statistically downscale established climate models using satellite-based sea surface temperature data and in situ industry measurements to inform climate resiliency predictions for Atlantic salmon aquaculture on the south coast of Newfoundland, Canada. Our objectives were to (1) understand how local climate conditions and depth effects vary in the coastal marine environments that support farmed Atlantic salmon production; (2) apply these relationships to understand how seasonal chronology and forecasted interannual changes to water temperature will affect future farmed Atlantic salmon growth and sea lice (Lepeophtheirus salmonis) exposure; and (3) identify the seasonal mortality risk to farmed Atlantic salmon smolt under multiple climate change and sea lice scenarios. While the absolute growth of farmed Atlantic salmon was determined to be minimally affected, the chronology of growth changed with optimal growth periods predicted at deeper sea cage depths (10 and 15 m), and shifted from unimodal growth distributions throughout the summer to scenarios with two distinct growth peaks bookending a low summer growth period for 1 and 5 m depths as the time series progressed. Warm summer temperatures also increased the projected abundance of sea lice and decreased farmed Atlantic salmon smolt survival. Our results identify both resilience and vulnerabilities in Newfoundland Atlantic salmon aquaculture sites and highlight the risk to industry and an opportunity to mitigate vulnerabilities prior to their predicted onset.