When Is It Better to Use Sex-Specific Assessment Models?

Many fish and shellfish species have traits or management that cause fishing mortality to differ between sexes.  In contrast, most stock assessments use sex-aggregated data and models to determine stock status and to provide fishing level recommendations.  The disconnect may cause poor performance of common assessment techniques when sex-specific differences in fishing mortality occur.  We conducted a simulation study of the accuracy of sex-specific and sex-aggregated stock assessment models under three scenarios of sex-specific fishing mortality: 1) no differences between the sexes, 2) differences between the sexes based on size-specific selectivity and sexually dimorphic growth, and 3) differences in fishing mortality and selectivity between the sexes. In addition to the sex-aggregated assessment model, two sex-specific assessment models were fitted to data sets: one with sex-specific data only available for a survey, and one with sex-specific data available for all data sources.  The data generating model was based on the life history and fisheries for Summer Flounder in the Mid-Atlantic US.  Preliminary results indicate all three assessment models perform reasonably well when sex-specific differences are absent, but model accuracy diverges when sex-specific differences increase.