Growth acceleration, behaviour and otolith check marks associated with sex change in the wrasse Halichoeres miniatus

Abstract

In protogynous sex-changing fishes, females are expected to compete for the opportunity to change sex following the loss of a dominant male and may exhibit growth and behavioural traits that help them maintain their dominant status after sex change. A male removal experiment was used to examine changes in female growth and behaviour associated with sex change in the haremic wrasse Halichoeres miniatus and to test whether any changes in growth associated with sex change were recorded in otolith microstructure. Dominant females began displaying male-characteristic behaviour almost immediately after the harem male was removed. The frequency of interactions between females increased following male removal. In contrast, feeding frequency of females decreased. The largest one to three females in each social group changed sex following male removal and exhibited an increase in growth associated with sex change. Sex changers grew more than twice as fast as non-sex changers during the experimental period. This growth acceleration may enable new sex-changed males to rapidly reach a size where they can defend the remaining harem from other males. An optical discontinuity (check mark) was present in the otoliths of sex-changed fish, and otolith accretion rate increased significantly after the check mark, corresponding with the increased growth rate of sex-changing females. Wild caught males, but not females, exhibited an analogous check mark in their otoliths and similar increases in otolith increment widths after the check. This indicates that an increase in growth rate is a regular feature of sex-change dynamics of H. miniatus.