Developmental Temperature Shapes the Otolith Morphology of Metamorphosing and Juvenile Gilthead Seabream (Sparus aurata Linnaeus, 1758)

Otolith morphological variability is used as a reliable indicator to discriminate fish that experience different environmental conditions during their lifetimes. The present study examined the effects of developmental temperature (DT) during the egg and yolk-sac larval period on the otolith shape and asymmetry of Gilthead seabream in the later metamorphosis (56-58 days post-hatching, dph) and the early juvenile stage (93-95 dph). The experimental populations were reared at different water temperatures (17, 20, or 23 degrees C DT) from epiboly onset to the end of the yolk-sac larval stage (5-7 days post-fertilization, dpf) and then at a common rearing temperature (20 degrees C), up to the end of the trials (93-95 dph). Otolith shape and bilateral asymmetry were analyzed at metamorphosis (20-21 mm standard length, SL) and the early juvenile stage (31-32 mm SL). The results of elliptic Fourier analysis showed that DT significantly affected the otolith shape at both stages examined. Furthermore, elevated DT significantly increased the asymmetry levels of seabream otoliths in the early juvenile stage. The results are discussed in terms of the thermally induced long-term changes of seabream otolith morphology and the potential effects of the raised otolith asymmetry on wild seabream juveniles.