Sex-Specific Planktonic Larval Durations in the Bluehead Wrasse, Thalassoma bifasciatum

The bluehead wrasse, Thalassoma bifasciatum (Labridae), a protogynous hermaphrodite common to shallow reefs of the Caribbean, exhibits two color-phases: small, initial phase (IP) individuals may be either male or female, while larger, terminal phase individuals are always male. Among individuals in the initial phase, population sex ratios are generally female biased; however, that bias becomes increasingly pronounced on smaller reefs. We tested the hypothesis that this relationship between population size and IP sex ratio results from sex-specific recruitment strategies. Initial phase males experience very low reproductive success on small reefs, but do well on larger reefs. It would thus be adaptive for IP males to avoid small, patch reefs common in lagoons by preferentially settling on the first reef they encounter: the large, fringing reefs forming the seaward edge of lagoon systems. We used otolith analysis to test the prediction that IP males would exhibit shorter and less variable planktonic larval durations (PLD) relative to IP females. Our data confirm the second of these predictions, IP male PLDs were significantly less variable than those of IP females, but this difference was not strong enough to result in a shift in the mean PLDs of IP males and females.