Seasonality of fin whale "Balaenoptera physalus" call interval obtained from ocean bottom seismic observation system in Northeast Japan

We analyzed the seismic data from 2009 to 2013 obtained from seafloor cable seismic network off Kushiro, Hokkaido, Japan, which was deployed by Japan Agency for Marine Earth Science and Technology in 1999. Two kinds of calls were recorded, one is "Single" which is not related to the preceding and following intervals, and the other is "Doublet" which alternates short intervals and long intervals. Especially the interval of "Doublet" shows a seasonal change, it is characterized as a long interval in January and February, while becomes shorter interval in October and November. It is quite unlikely that the same group of fin whales are calling while the call is appearing off Kushiro. The seasonal change of "Doublet" might be a change of the group appearing off Kushiro.