Spatial Dynamics of the Northern Gulf of Mexico Shrimp Fishery in Relation to Large-Scale Hypoxia

The northwestern Gulf of Mexico shelf experiences one of the largest seasonal hypoxic (dissolved oxygen ≤ 2 mg l^-1) zones in the northern hemisphere. Hypoxia is most severe during summer (Jul-Aug) when the shrimp trawl fishery is at its peak. We conducted retrospective analyses of electronic logbooks of shrimping effort as well as synoptic hydrographic and aerial surveys to quantify the spatial dynamics of the shrimp trawl fleet in response to spatial variation in bottom dissolved oxygen (DO) conditions and other environmental factors. Shrimpers avoid regions of low bottom DO and re-distribute fishing effort to both the inshore and offshore edges of the hypoxic zone, as well as to more moderate bottom DO waters to the west. These shifts in the spatial distribution of the shrimp fleet are similar to those of both target (penaeid shrimp) and nontarget (juvenile fishes) species of the fishery, suggesting both harvest and bycatch interactions may be intensified during summer in oxygenated refuge habitats.  Our results indicate that fishermen are responsive to spatially varying environmental conditions, and that altered spatial distributions have implications for understanding the effects of fishing on both harvested and bycatch species.