Environmental Determinants of Gulf Menhaden Condition

Gulf Menhaden (Brevoortia patronus) is an economically and ecologically important harvested species in the northern Gulf of Mexico (NGOM). In this study we describe and investigate the inter-annual variation in condition of the B. patronus stock in the NGOM (estimated as oil density, liters/kg). We hypothesize that the contrasts in inter-annual condition are controlled by abiotic conditions. We examined the relationship of potential predictor variables: chlorophyll a phenology and magnitude, the temporal and spatial patterns of sea surface temperature, the magnitude of river discharge, the strength and direction of wind and the spatial characteristics of freshwater intrusion in the NGOM. We show that there exists, in the NGOM, an ecoregion that exhibits coherent productivity dynamics, that the time-series of observed and modeled condition is characterized by marked inter-annual variability, and that environmental conditions in the NGOM have explanatory power to predict annual oil content in the stock. If Gulf Menhaden are a critical link to the productivity of higher trophic levels and their condition is indicative of large-scale changes in ecosystem productivity, then the continued monitoring of menhaden oil content can provide information about the expected status of stocks that prey on Gulf Menhaden.