Seasonal and diel acoustic activity of sei whales (Balaenoptera borealis) in the New York Bight.

High levels of anthropogenic activity in the northwest Atlantic may have impacts on marine species. As such, it is important to document species distribution in order to monitor behavioral responses to changes in these activities or the environment. Sei whales (Balaenoptera borealis) are an endangered species consistently documented in the New York Bight (NYB), though they are understudied in this region. Here, we used passive acoustic monitoring from 2017 to 2020 to investigate sei whale acoustic presence and vocal activity in the NYB, as well as the relationship between seasonal acoustic presence and environmental variables [sea surface temperature (SST) and chlorophyll-a concentration (Chl-a)]. Sei whales were primarily present in spring, exhibiting low levels of activity in other seasons, potentially reflecting migratory patterns. Vocal activity was higher during daylight, supporting growing evidence that vocalizations are reduced at night when sei whales are thought to forage. Presence and vocal activity were highly correlated with SST, particularly in spring; both tended to decrease once temperatures reached around 9˚C. However, acoustic activity was not significantly related to Chl-a. These findings suggest that the NYB may be an important spring habitat and potential feeding ground for sei whales in the northwest Atlantic.