Abstract
The rapid expansion of offshore wind development along the United States east coast has
raised concern over its potential effects on marine mammal populations. Potential increases in
regional vessel traffic associated with wind energy development are of particular importance in
this context because of the heightened vessel strike risk and additional noise exposure they
present. Of particular concern, this could pose an increased threat to the critically endangered
North Atlantic right whale. There are only an estimated 356 right whales remaining in the
population. The species is at risk of extinction, largely because of mortality induced by
entanglement and vessel strikes. To address this concern, we obtained monthly vessel density
data before, during, and after the construction of three wind energy projects: the Block Island
Wind Farm, Coastal Virginia Offshore Wind Pilot Project, and Vineyard Wind I. We analyzed
these data to determine whether vessel density increased during the development process.
Automatic Identification System (AIS) vessel data were synthesized and cleaned by the Global
Marine Traffic Density Service. We conducted a spatiotemporal analysis of vessel density on
monthly rasters of vessel occupancy time. The data included layers with all vessels aggregated
together, and layers subset by vessel category. We then extrapolated potential outcomes of wind
development in these areas based on the changes we observed. Our analysis found that vessel
density increased between pre-construction and post-construction by 2.52 – 4.98 monthly hours
on average. Substantially larger increases in vessel density occurred once construction started,
but they were immediately offset once construction concluded. Overall, the risks to right whales
imposed by offshore wind-related vessel density appear low, though continued monitoring in the
future is critical to assess these impacts across longer operational periods and larger-scale wind
farms.