Better characterizing fish survival at the most vulnerable larval stage, represents a challenge in a context of global warming and for effective resource management. The European seabass provides a good model to study the interactive effects of temperature and genetics on survival. The species is structured into three genetically distinguishable populations along a geographic gradient from Atlantic (AT) to Western Mediterranean (WM) and then Eastern Mediterranean (EM), with populations a priori adapted to different natural environments. Larval survival was studied in four thermal regimes reflecting natural temperatures of the three populations, and a typical temperature regime used in hatcheries. The AT population showed higher survival in colder regimes compared to the Mediterranean populations. Conversely, larval survival in warmer regimes was higher for the EM population. The WM population had the lowest survival in all thermal regimes. A quadratic relationship was revealed between larval survival and temperature with an estimated maximum around 13.6 degrees C for AT survival, compared to above 17 degrees C for the Mediterranean populations. The level of reciprocal introgression of Atlantic and Mediterranean genomes strongly affected larval survival. The greater the degree of introgression the lower the survival, which partly explained the poor performance of the central WM population. These results demonstrate local adaptation of AT and EM populations to their natural regimes. For the introgression effect, we found a strong purging effect acting on the introgressed ancestry or reproductive isolation barriers. In this species, therefore, population introgression should be carefully considered in strategies for establishing domesticated and/or selected lineages.