A Comparison of the Relative Influence of Environmental and Ecological Drivers on the Dynamics of Gulf Menhaden (Brevoortia patronus) within the Gulf of Mexico

Gulf menhaden Brevoortia patronus play a key ecological role in energy transfer from primary producers to upper consumers in the Gulf of Mexico (GoM). The expected increase in global demand for seafood/fishmeal, typical boom-and-bust cycles of forage fish (such as menhaden), and GoM ecosystem threats (such as hypoxia and harmful algal blooms) suggest a need to better understand the drivers of this stock's dynamics. These dynamics were assessed by simulating harvest strategies within the Ecopath with Ecosim (EwE) framework. The optimization of EwE's vulnerability parameters indicate that menhaden dynamics are largely driven by bottom-up processes, suggesting primary productivity is an important driver of menhaden dynamics within the GoM. Indeed, gulf menhaden continue to thrive in this ecosystem despite supporting an industrial fishery and a number of top predators. Furthermore, gulf menhaden constitute a relatively large proportion of total consumption by a number of GoM piscivores, reflecting the ecological importance of this forage fish. Efforts are underway to incorporate environmental covariates into this model as additional sources of mortality (ex: hypoxia, harmful algal blooms) and inter-annual deviations in system primary productivity (ex: temperature, salinity, rainfall).