Do European Seabass Larvae Grow Better in Their Natural Temperature Regime?

Abstract

Understanding how warming surface waters impact the larval growth of highly prized marine fishes such as the European seabass, Dicentrarchus labrax, is important for sustainable fisheries and aquaculture. We studied the growth of larvae from three genetically differentiated seabass populations, Atlantic (AT), Western Mediterranean (WM), and Eastern Mediterranean (EM), reared in a common garden under three thermal regimes, representative of seasonal changes in a relatively cold Atlantic (rAT), intermediate Western Mediterranean (rWM), and warm Eastern Mediterranean (rEM). Survival was higher in warmer regimes until larvae reached a length of 23 mm, after which there was no major difference. Growth was monitored from 20 days posthatch to 1.5 g, with individuals sampled at regular intervals and their population of origin identified by parentage assignment using their genotypes for 96 SNPs. Significant length differences emerged among populations, the AT population being longer than WM and EM in all thermal regimes. In conclusion, the AT population had higher growth than the WM and EM populations in all thermal regimes, not just in its own, and the AT population can be considered the most robust to temperature variations at the larval stage. Further research is required to understand whether the high growth rate of the AT population reflects a process of local adaptation to a relatively cold thermal regime.

Keywords: Adaptation; European seabass; Growth; population genetics; temperature.

FIGURE 1

General experimental scheme. (AT, Atlantic population; WM, Western Mediterranean population; EM, Eastern Mediterranean population; rAT, Atlantic thermal regime; rWM, Western Mediterranean thermal regime; rEM, Eastern Mediterranean thermal regime).

FIGURE 2

Temperature profiles of the three thermal regimes (rAT, Atlantic thermal regime [blue]; rWM, Western Mediterranean thermal regime [yellow]; rEM, Eastern Mediterranean thermal regime [red]). The solid lines represent the actual temperature measured twice a day in each regime. The dashed lines represent the target temperature.

FIGURE 3

Panel (a) Average log‐transformed body length (mm) of three populations of European seabass (AT, Atlantic; WM, Western Mediterranean; EM, Eastern Mediterranean) as a function of day posthatching into three thermal regimes (rAT, Atlantic regime; rWM, Western Mediterranean regime; rEM, Eastern Mediterranean regime); error bars represent the standard error of the mean in each population × regime × age combination; Panel (b) shows the thermal regime‐specific slopes of the regression of Log(BL) on days posthatching from Model 3, and Panel (c) shows the population‐specific slopes of the regression of Log(BL) on days posthatching from the same model.

FIGURE 4

Length of the Atlantic seabass population in the Atlantic thermal regime in the present experiment (rAT, blue dashed line), seabass captured from the Atlantic natural environment in Brittany (Chevalier , blue solid line), Western Mediterranean seabass population from Western Mediterranean thermal regime in the present experiment (rWM, yellow dashed line), seabass captured from the Western Mediterranean natural environment in the Gulf of Marseilles (Guérin‐Ancey ; yellow solid line).