Introduction
With global warming, understanding the temperature effect on fish growth is essential for sustainable aquaculture. The European seabass is an ideal model for this, as a key aquaculture species in the Mediterranean, which is strongly affected by global warming. We tested the hypothesis that the Atlantic (AT), West Mediterranean (WM) and East Mediterranean (EM) wild populations of European seabass would each perform better in their own temperature regime.
Material and Methods
We evaluated body weight and daily growth coefficient (DGC) of the three populations, as well as their genetic parameters, when reared in common garden, in three thermal regimes that reflected their three native habitats: a cold Atlantic (rAT), an intermediate Western Mediterranean (rWM) and a warmer Eastern Mediterranean (rEM) seasonal temperature regimes. Body weight was measured every six weeks for 2-3 years. All fish were genotyped on the DlabChip 57K SNP chip, allowing a posteriori parentage assignment as well as estabilishing the genomic relationship matrix.
Results and discussion
The AT fish were heavier than WM and EM in all regimes and at all times. The DGC of the AT population was higher than that of WM and EM during the first year, while in the second and third year this was only true for rearing temperatures below 18 °C. Thus, they grew faster at all times in their own rAT regime, and during autumn and winter in rWM and rEM regimes The EM population had higher DGC in spring and summer in the Mediterranean regimes. Overall, these phenotypic results can be interpreted as local adaptation of the populations to their natural thermal regime. Both temperature and age were associated with declines in the heritability of DGC, but the expected response to selection remained higher in summer, due to higher genetic and phenotypic variance. The genetic correlations (rG) of DGC between two seasons decreased when the temperature difference between both seasons increased. The EM population had overall higher rG across seasons than WM and AT, thus showing a potential for more stable growth performance. A residual seasonal effect on rG showed there are specific seasonal metabolic pathways. The EM population should be preferred for high temperature culture, and based on previous studies, we hypothesize that a terminal cross of AT and EM fish could have a good aquaculture potential.
Acknowledgements
This study was conducted as part of the ANR FishNess project (ANR-21-CE20-0043).