Effects of climate change on gilthead seabream aquaculture in the Mediterranean

Aquaculture of gilthead seabream, arguably the most important finfish aquaculture species in the Mediterranean, faces changing environmental conditions due to faster-than-average climate change in the region. We utilize physiological modelling to estimate effects of moderate and severe climate change on key indices of aquaculture production for all coastal regions of the Mediterranean. Two publicly available global climate change scenarios with daily sea temperature projections serve as forcing for the physiological model during two-year farming cycles representing: (i) reference period starting in 2021, (ii) mid-term effects starting in 2051, and (iii) longterm effects starting in 2091.We investigate effects of climate change by analyzing changes in time for fish to reach a market size, feed conversion ratio at the market size, and the weight of the fish and the associated feed conversion ratio after two years of farming. Additionally, we track the number of days with sea water temperatures equal to or greater than 28 degrees C during the two-year period, when gilthead seabream starts experiencing temperature stress. Time to market size generally decreases with climate change from the initial average of 450 days for the reference period by up to 36%. Feed conversion ratio at market size does not appreciably change with climate change, but it does change for the two-year culturing period for up to 10 %, primarily due to faster growth in warmer sea water, and the correspondingly greater weight achieved over the two-year growth cycle.While the outlook for aquaculture is positive in the mid-term, some indicators show a negative trend in the long-term. The long-term effects of climate change will be greatest in the currently most productive farming regions of the Mediterranean: Levantine, Aegean, and Adriatic seas, and coastal waters of Tunisia. Our analysis focuses on basin-level features, but we provide geospatially referenced simulation results that can be used to analyze effects of climate change in a particular region of interest.