Delineation of essential habitat for juvenile red snapper in the northwestern Gulf of Mexico

Seasonal habitat suitability index models were developed for juvenile red snapper Lutjanus campechanus in the western Gulf of Mexico. Habitat factors considered in the analysis included water temperature, salinity, and dissolved oxygen at the bottom; depth and density of offshore petroleum platforms; and low-relief bottom structures. High-value habitat for juvenile red snapper is characterized by depths between 18 and 64 m, water temperatures of 24-26 degrees C, salinities around 35%, and dissolved oxygen levels of at least 5 mg/L. Density of low-relief structures was not a significant habitat element, and an inverse association was found between juvenile red snapper abundance and the density of offshore platforms. Results of the model analysis suggest that the step-like expansion of the hypoxic area (dissolved oxygen less than or equal to 2 mg/L) offshore of the mouth of the Mississippi River and west to the Louisiana-Texas border, which first occurred in 1993, has reduced habitat carrying capacity for juvenile red snapper in this region by up to 25%, averaging 19%. This environmental change may limit the level to which overfished Golf red snapper stocks can be rebuilt to historical levels.