Influence of sex ratios in population dynamics of greater amberjack

Greater amberjack, Seriola dumerili, is a pelagic reef fish that is managed in the US as two separate stocks, the Gulf and the Atlantic.  The most recent stock assessment for the Gulf stock found it to be overfished and undergoing overfishing.   Sex-specific spatial distribution and exploitation may contribute to our understanding of the stock’s overexploitation.  This may be important for greater amberjack since schools in some regions may predominantly be one sex or the other and, based on the fisheries, amberjack may be subject to sex-specific mortality.  These factors may lead to sex ratios that are highly skewed from an assumed ratio of 1:1.  Altered sex ratios have been found to influence population dynamics in sex changing fish, and it may be that in a gonochoristic fish that exhibits sexually dimorphic growth, such as greater amberjack, there may also be an influence.  To explore the potential affects, a range of sex ratios based on previous and ongoing studies were incorporated into age, size, and sex structured models.  Several outputs, including total, total male, and total female spawning stock biomass per recruit and total egg, sperm, and fertilized egg production, are used to evaluate the potential effects of different sex ratios.