Diversification of marine aquaculture in Norway under climate change

Recently there has been increased interest in species diversification in aquaculture as a strategy to adapt to climate change. Since species diversification is a long-term strategy, climate change and future farming conditions must be considered. The aim of this study was to evaluate how changing temperatures under different IPCC climate scenarios may affect marine aquaculture species diversification in Norway. Since farm conditions vary between locations, this study focused on four geographic areas (South, West, North and Arctic) and three farms within each area. Using a climate model downscaling of three climate scenarios (Shared Socioeconomic Pathways; SSP1-2.6, SSP2-4.5, and SSP5-8.5), daily temperatures from the years 2020-2099 were evaluated at each farm location to identify challenging conditions for 34 species. A Challenging Conditions Index (CCI) was developed based on species thermal tolerances to compare the 34 potential aquaculture species. The results showed differences in the number of challenging days (hot and cold) between areas, and even within areas, highlighting the need to consider site-specific conditions. For warm-water species more commonly farmed in the Mediterranean (e.g. European seabass, gilthead seabream), the calibrated model projections at the investigated Norwegian farm sites suggest that cold temperatures would still be challenging. Differences in the number of challenging days between the climate scenarios become more apparent towards the mid and end of century, though all scenarios show interannual variation rather than a constant change in conditions over time. Hence, any species selected for diversification purposes will have to be able to tolerate a range of temperature conditions, and species with narrower tolerance ranges could be a risk. These findings underline the importance of considering the interannually varying conditions that species will be exposed to rather than focusing solely on long-term averages. Establishing a new large-scale commercial aquaculture species takes a considerable amount of time and resources. Therefore, to support interpretation of the results and further studies on diversification under climate change, this study also introduces Aquaculture Readiness Level (ARL (R)) as a consistent evaluation of the research and development status, progress towards commercialisation and climate action orientated production. As species will have to be able to tolerate a range of temperature conditions over different years, the level of knowledge, resources, and innovation will have to be continually enhanced to improve adaptive capacity.