Fin whale song variability in the Southern California Bight, from 2008 through 2012 /

Male fin whales (Balaenoptera physalus) sing a low frequency song consisting of downswept calls with most energy around 20 Hz. There are some indications fin whale song patterns may be used as a population indicator as they vary amongst regions. Four and a half years of recordings from the San Nicolas Basin in Southern California were analyzed to investigate changes in song inter-pulse-intervals (IPI). The song patterns detected at this site were the Southern California singlet and doublet, and the Gulf of California triplet pattern. The Southern California doublet IPIs increased by ̃5 s during the study period; this was the most abundant song type with IPI of ̃17 - 23 s in late 2012. The singlet was the second most common song type with an IPI in 2012 of ̃18.7 s and it also increased by ̃ 5 s over the course of the study. The doublets were present year-round with slight seasonal variability. The singlet presence was higher in the fall and winter. The Gulf of California triplet song pattern was recorded on only one day with IPIs 6 - 6 - 20 s. A comprehensive explanation for the increasing IPI is not evident although the relationship to ship noise may be important and should be further researche