Acoustic presence and demographics of sperm whales (Physeter macrocephalus) off southern New England and near a US offshore wind energy area

Abstract

Construction in the southern New England wind energy area (WEA), a large-scale offshore wind farm on the east coast of the United States, started in June 2023. Baseline data was collected from 2020 to 2022, with six passive acoustic recorders (SoundTraps) deployed at shallow (<60 m) sites in the vicinity of Nantucket Shoals and Cox’s Ledge. Data were analysed for sperm whale presence, and demographic composition was assessed using interclick intervals. Presence varied by site, season, and year. Sperm whales were detected year-round but the majority (78%) of days with acoustic occurrences were between May and August. Three demographic classes (putative social groups, adult males, and midsize animals) were detected across multiple seasons, with social groups detected most frequently. Sound propagation tests were conducted at two sites and predicted detection ranges within 20–40 km indicate that sperm whales were likely in proximity to the WEA. These results provide a baseline that will be used to assess ongoing sperm whale presence, especially that of social groups which may be more sensitive to disturbance. This study highlights why sperm whales, classed as endangered in US waters, should be considered in mitigation plans and permitting efforts for offshore wind energy.