In recent years, the fisheries catches of both wild and hatchery-produced and released red sea bream Pagrus major have continually declined in Hyuga-nada, Miyazaki Prefecture. To reveal the changes in life history traits and their relationships with this fluctuation in red sea bream population, maturational and somatic conditions of the fish caught during the period 2012 -2014 were examined and compared with previous data. The condition factor ( body-mass index) after 1998 was found to be significantly lower than that before 1989. At the same time, the spawning period moved earlier, and mean size at maturation size increased. The condition factor is inversely related to coastal water temperature. Higher mean water temperature is considered to be a causal factor of the observed changes in life history traits. Oceanographic fluctuations may also have an impact on these changes through the food condition for red sea bream.