Sounds from airguns and fin whales recorded in the mid-Atlantic Ocean, 1999–2009

TLDR

The authors investigated whether offshore seismic airgun noise masks fin whale 20‑Hz pulse calls across the Mid‑Atlantic Ridge. They deployed autonomous hydrophones from 1999‑2009, used an automatic detection algorithm to identify airgun patterns, and performed long‑term spectral analysis of fin whale calls while acoustically locating survey vessels off Newfoundland, northeast Brazil, and Senegal/Mauritania. Airgun and fin whale sounds were detected at all sites; fin whale calling rates were higher north of 32°N, rose in late summer/fall, peaked in winter when airgun noise was common, and airgun noise was recorded up to 4000 km from vessels, with some sites experiencing >80 % of days/month over 12 months.

Abstract

Between 1999 and 2009, autonomous hydrophones were deployed to monitor seismic activity from 16° N to 50° N along the Mid-Atlantic Ridge. These data were examined for airgun sounds produced during offshore surveys for oil and gas deposits, as well as the 20 Hz pulse sounds from fin whales, which may be masked by airgun noise. An automatic detection algorithm was used to identify airgun sound patterns, and fin whale calling levels were summarized via long-term spectral analysis. Both airgun and fin whale sounds were recorded at all sites. Fin whale calling rates were higher at sites north of 32° N, increased during the late summer and fall months at all sites, and peaked during the winter months, a time when airgun noise was often prevalent. Seismic survey vessels were acoustically located off the coasts of three major areas: Newfoundland, northeast Brazil, and Senegal and Mauritania in West Africa. In some cases, airgun sounds were recorded almost 4000 km from the survey vessel in areas that are likely occupied by fin whales, and at some locations airgun sounds were recorded more than 80% days/month for more than 12 consecutive months.