Stock assessment of protogynous fish: evaluating measures of spawning biomass used to estimate biological reference points

Simulations to investigate the performance of three measures of spawning biomass for their ability to estimate biological reference points (BRPs) were applied. Two deterministic models were constructed, both structured by age and sex, to describe a protogynous stock. Total egg production was determined by the product of mature females and eggs per female, summed across ages. Estimates of BRPs were closest to the true values from simulations when the assessment model counted both males and females. For all measures of spawning biomass, the steepness of the fertilization function explained more of the variation in estimated BRPs than any other model factor. In protogynous fish, dome-shaped selectivity would reduce fishing pressure mainly on males.