Estimating singing fin whale population density using frequency band energy

• Published in: The Journal of the Acoustical Society of America 2014-10, Vol.136 (4_Supplement), p.2275-2275
• Main Authors: Mellinger, David K., Küsel, Elizabeth T., Harris, Danielle, Thomas, Len, Matias, Luis
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4900221

Fin whale (Balaenoptera physalus) song occurs in a narrow frequency band between approximately 15 and 25 Hz. During the breeding season, the sound from many distant fin whales in tropical and subtropical parts of the world may be seen as a “hump” in this band of the ocean acoustic spectrum. Since a higher density of singing whales leads to more energy in the band, the size of this hump—the total received acoustic energy in this frequency band—may be used to estimate the population density of singing fin whales in the vicinity of a sensor. To estimate density, a fixed density of singing whales is simulated; using acoustic propagation modeling, the energy they emit is propagated to the sensor, and the received level calculated. Since received energy in the fin whale band increases proportionally with the density of whales, the density of whales may then be estimated from the measured received energy. This method is applied to a case study of sound recorded on ocean-bottom recorders southwest of Portugal; issues covered include variance due to acoustic propagation modeling, reception area, variation in whale song acoustic level and frequency, and elimination of interfering sounds. [Funding from ONR.]