Passive Acoustic Recorders Enable Cetacean Monitoring and Assessment

Long-term monitoring of cetaceans in the Pacific Islands Region is currently underway at three locations within the Hawaiian Archipelago and Palmyra Atoll using stationary, passive acoustic recorders. During a May 2009 research expedition of the NOAA Ship Oscar Elton Sette, scientists from the PIFSC Cetacean Research Program deployed a High-Frequency Acoustic Recording Package (HARP) at Ladd Seamount off Midway Atoll in the Northwestern Hawaiian Islands. This HARP is specifically positioned to assess the occurrence of baleen whales, sperm whales, and false killer whales in this remote region. The acoustic data, which provide information on the occurrence of various species, will be studied along with oceanographic data collected from satellite-borne sensors to help identify physical and ecological factors that may influence the occurrence of cetaceans in the region.

Long-term acoustic recording has been underway at Palmyra Atoll and off the Island of Hawai'i for several years. The HARPs in both locations were recovered and redeployed during the May Sette cruise. To date, the HARP at Palmyra has provided insight into the year-round occurrence of a newly-identified species of beaked whale (Mespolodon hotuala) and the diel behavior of melon-headed whales at the Atoll. Monitoring off Hawai'i has indicated that at least three species of beaked whale regularly occur in this location, and as many as three other as yet unidentified beaked whale species may also be found here. The cetacean occurrence data from the Hawai'i HARP are being compared to visual cetacean survey data from the same region to develop the statistical relationships required for assessment of cetaceans using acoustic recorders only.