Simulation Study of Biological Reference Points for Summer Flounder

Abstract The biological reference point Fx % (i.e., the fishing mortality rate that maintains the spawning stock biomass per recruit at x% of its unfished value [where x is usually set to 40]) is a commonly used proxy for F MSY (the fishing mortality rate that results in the maximum sustainable yield). However, Fx % is not in general equivalent to F MSY. To investigate the difference between Fx % and F MSY, we developed a simple simulation model capable of representing the relationship between yield and fishing mortality, maximum spawning potential (%MSP), and the curvature of the stock–recruitment (S–R) curve (parameterized as β) for a stock similar to summer flounder Paralichthys dentatus (a high-β species). The model demonstrates that the dynamic trajectories of the stock are heavily dependent on β. The model confirmed the dependence of equilibrium yield on β and produced a specific relationship between the magnitude of β and yield. A decision-theoretic approach was used to suggest that setting x to 40...