Seasonal contribution of mysticete vocalization to ambient noise in southern California waters

Abstract

Many species of baleen whales reside or migrate annually through California waters. During these times some species of vocalizing whales can be detected, identified, and tracked with SOSUS arrays. Historical research by W. Cummings documented strong seasonal changes in narrow-band ambient sound associated with then unidentified sounds. Contemporary research shows these sounds to be blue and fin whale vocalizations. The current study compares historical and contemporary narrow-band ambient measurements with respect to mysticete residency and movement through southern California waters. Seasonal peaks in ambient noise agree with earlier reports, but increased anthropogenic sound reduced the magnitude of the effect. Potential sources of changes in ambient noise and their effects on the whales are discussed. [Research supported by the Strategic Environmental Research and Development Program, Project CS-1082.]