Divergent time course of cortisol response to stress in fish of different ages

► We investigated the cortisol response to stress in fish of different ages. ► Fingerling and juvenile elevates cortisol with a similar pattern of adult ones. ► Peak post-stress cortisol occurred after 5 and 30 min in fingerlings and juveniles. ► Peak post-stress cortisol occurred after 60 min in adult fish. ► These results have strong applicability for stress and welfare studies.