Using ocean bottom seismometer networks to better understand fin whale distributions at different spatial scales

• Published in: The Journal of the Acoustical Society of America Vol. 136; no. 4_Supplement; p. 2092
• Main Authors: Weirathmueller, Michelle, Wilcock, William SD, Soule, Dax C.
• Format: Journal Article
• Language: English
• Published: 01-10-2014
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4899518

Ocean bottom seismometers (OBSs) are designed to monitor ground motion caused by earthquakes, but they also record low frequency vocalizations of fin and blue whales. Seismic networks used for opportunistic whale datasets are rarely optimized for acoustic localization of marine mammals. We demonstrate the use of OBSs for studying fin whales using two different networks. The first example is a small, closely spaced network of 8 OBSs deployed on the Juan de Fuca Ridge from 2003 to 2006. An automated method for identifying arrival times and locating fin whale calls using a grid search was applied to obtain 154 individual fin whale tracks over one year, revealing information on swimming patterns and spatial distribution in the vicinity of a mid ocean ridge. The second example is a network with widely spaced OBSs, such that a given call can only be detected on one instrument. The Cascadia Initiative Experiment is a sparse array of 70 OBSs covering the Juan de Fuca Plate from 2011 to 2015. Localization methods based on differential arrival times are not possible but techniques to locate the range and bearing to fin whales with a single OBS can be applied to constrain larger scale spatial distributions by comparing call densities in different regions.