Abstract
Vessel strikes are one of the leading causes of human-related mortality for large whales. In the Gulf of Mexico, there is a high volume of vessel traffic from commercial shipping, fishing, recreation, oil and gas, and military vessels. This puts the sperm whale and the Gulf of Mexico Bryde's whale, both of which are listed as endangered under the U.S. Endangered Species Act, at risk of vessel strikes. To date, the magnitude and spatial extent of this risk is poorly understood. We quantified spatially-explicit vessel strike risk in the Gulf of Mexico for these two large whale species by combining several years of Automatic Identification System (AIS) vessel data with modeled species distribution data. Our analysis of the AIS data confirmed a large amount of vessel traffic in the Gulf of Mexico, a substantial portion of which was attributed to the oil and gas industry. Spatial analyses of the co-occurrence of vessel traffic and species distribution data indicated that Bryde’s whales face considerable vessel strike risk near De Soto Canyon and on the West Florida shelf, while sperm whales face elevated vessel strike risk in shipping lanes associated with the ports of Galveston and Port Arthur, Texas. For both species, the risk of lethal vessel strike is also high off the coast of Louisiana, near the Mississippi Canyon. This work represents one of the first attempts to quantify the spatially-explicit vessel strike risk for the Gulf of Mexico’s two resident large whales species. The identified areas of higher risk can help managers prioritize where mitigation measures can be implemented to reduce the risk of vessel strikes for both sperm whales and the Gulf of Mexico Bryde's whale.
