Geographic distribution of mariculture species determines the impacts of thermal variability on growth performance and thermal resilience

Climate change is increasing both ocean temperatures and thermal variability at various temporal and spatial scales. As mariculture species cannot change their location, they are highly vulnerable to changes in local environmental conditions, making their inter- and intraspecific thermal physiology economically important. It is well known that increased temperatures coupled with increased thermal variability can drive large changes in biological systems, but it is less well understood how this combination affects species across their geographic distribution depending on their thermal tolerance. To address this data gap, we used available published data on growth performance to develop thermal performance models bootstrapped to incorporate current thermal variability to estimate changes in growth performance across the geographic range of 33 commercially important fish and invertebrates in the northwest Pacific Ocean. Model predictions using thermally stable conditions overestimated growth compared to when natural variability was incorporated, but the discrepancy varied with latitude, with larger decreases in performance predicted at mid-latitudes where environments are more thermally variable. The potential resilience of species to future increases in warming - quantified by predicted thermal safety margin (EnvT max – T max ) and capacity for growth (T max – T opt ) across their range - also had a negative relationship with increasing thermal variability, which varied across latitude. We show that it is critical to incorporate the effects of a thermally variable environment into estimates of temperature-dependent growth performance when trying to predict the future resilience of species to climate change across their range, which currently remains a challenge due to data deficiencies for key species across oceanic boundaries.