Otolith daily increment formation in laboratory reared larval and juvenile bluefin tuna Thunnus thynnus

Otolith increments of bluefin tuna Thunnus thynnus were examined to estimate the periodicity of an increment formation and the timing of the first increment formation using larvae and juveniles with known age reared in three laboratories.The increment was formed daily up to 71 days after fertilization.The first increment was formed on the fifth day after fertilization, and around the fourth day after hatching which corresponded to the onset of feeding.Slower growing fish had otoliths with less distinct increments.Since wild captured larvae had otoliths with more distinct increments, fish in the wild either grow faster than that in a laboratory or only faster grown fish survived in the wild.