Evaluating the Vulnerability to Exploitation of an Atypical Protogynous Hermaphrodite, Black Sea Bass (Centropristis striata), Using a Population Simulation Model

Fishes that are protogynous hermaphrodites generally have sex ratios skewed toward males at larger sizes.  These skewed sex ratios at length can make a stock more vulnerable to over-exploitation, particularly in fisheries where minimum size is regulated, resulting in a removal of dominant males. We developed a length-based population model to test the vulnerability to exploitation of a population with an atypical protogynous life-history, in particular the northern stock of black sea bass (Centropristis striata). Black sea bass north of Cape Hatteras, NC are unusual for protogynous species in that they may undergo pre-maturational transformation, retain females at larger sizes, involve males in spawning that are sub-dominant and undertake seasonal migrations. The model was developed to examine the impact of sub-dominant male participation in population productivity, the influence of size-at-sex transformation and the subsequent robustness of the population to exploitation. Although the model does not capture all the dynamics of the population, such as density-dependent regulation of sex transformation, it does show that the northern sea bass are more robust to exploitation than would be expected.