Delayed Metamorphosis with Reduced Larval Growth in aCoral Reef Fish (Thalassoma bifasciatum)

Analyses of daily otolith increment sequences in the bluehead wrasse, Thalassoma bifasciatum, from the San Blas Islands of Panama indicated that (1) the duration of the planktonic larval period of this species ranges from 38 to 78 d, (2) those larvae with extended larval durations reach settlement size at the same age as average individuals but then remain planktonic for several more weeks, and (3) the estimated larval growth rate during this period of delayed metamorphosis (0.08 mm∙d−1) is distinctly lower than both the estimated growth rate before attaining settlement size (0.26 mm∙d−1) as well as the growth rate of juveniles after settlement (0.31 mm∙d−1). The ability to delay metamorphosis, the first documented for a vertebrate, may be an adaptation for maximizing the return of planktonic larvae to coastal waters.