A calibrated autonomous seafloor acoustic recorder was used to collect acoustics recordings on Cross Seamount. The first deployment recorded from April 26th and October 28th 2005 and the second from November 20th 2005 to May 10th 2006. The National Marine Fisheries Service office in Hawaii (Jeff Polovina www.pifsc.noaa.gov, and Dave Johnston,) and Scripps Institution of Oceanography (John Hildebrand, cetus.ucsd.edu) are collaborators. The goal of the work is to better determine the presence, relative abundance and behavior of cetacean species at Cross Seamount as relevant to fisheries interactions with cetaceans (primarily longline bycatch). The instrument recorded at 200 ksamples/second with a schedule of 5 minutes on and 20 minutes off.
Cross Seamount is located about 100 miles south of Oahu
The top of Cross Seamount is about 400 m deep, the seafloor recorder location shown with the yellow star.
Beaked whales were the most prominant species observed in the acoustic record, there being one primary call type as illustrated in the Figure below.
Spectrogram of the echolocation sound, presumed associated with beaked whales at Cross Seamount. The echo is from the seafloor, approximately 10 meters below the hydrophone.
These calls showed a strong diurnal pattern occuring only at night, with each dive of a group of animals extending to the seafloor at 400 m depth. Analyses of these and other cetacean sounds from these recordings are subject of ongoing study. One publication is out now (link to abstract ) and a second manuscript is in review.