Shipping noise in the Azores: A threat to the Faial-Pico cetacean community?

Abstract

The Azores archipelago is an important cetacean habitat spot, registering a very relevant resident and migratory population. Due to its geographical position, it also represents an important commercial crossroad between America and Europe. Vessels represent the major source of underwater noise which may affect cetaceans. Since 2017 acoustic measurements have been performed in the southern side of the channel between Pico-Faial. Although foreground biological signatures are numerous and relatively easy to spot in the data, it is not clear how to separate background abiotic, biotic and man made noise and, therefore, to single out the noise due to shipping. In order to address these questions, a shipping noise prediction tool using a 10-min resolution AIS coverage of the area, together with bathymetric, water column space-time descriptors and surface wind generated noise model, showed a significant noise variability between Pico-Faial islands. This variability was mainly observed in the strait and to the south of it, both along the coast associated with ferries and around offshore banks due to fishing activity. Time series of predicted sound pressure level at three receiver locations favorably compare with it in-situ noise measurements in the 44-177Hz a frequency band.