Since 1993, marine mammal strandings in the Northern Mariana Islands have been documented and archived by the Department of Lands and Natural Resources Division of Fish and Wildlife (DFW), mainly from Saipan. Until recently, the distribution and abundance of cetaceans in the Mariana Archipelago was relatively unstudied. The Mariana Archipelago, consisting of the islands of Guam to the south and the Commonwealth of the Northern Mariana Islands (including Saipan and Tinian, hereafter referred to as the Northern Mariana Islands) to the north, has been designated as a strategic location by the US Department of Defense, and serves as the principal US military training and basing location in the Western Pacific. However, these authors only included data beginning in 1978 for Japan, and did not consider atypical mass beaked whale stranding events that occurred during the 1960s and 1970s in Japan, which may have also been associated with MFAS. The author's conclusions were that beaked whale mass strandings were correlated with naval activity in the Mediterranean and Caribbean Seas, but not correlated off the coasts of Japan and southern California. , with more robust information on historical naval activity to examine the correlation between beaked whale mass strandings and military events. used the same stranding data as D'Amico et al. An additional 27 other beaked whale mass stranding events have been documented near a naval base or ship, but very few have had direct evidence of associated sonar use. Since the introduction of MFAS in the range of 4.5–5.5 kHz in the early 1960s, there have been at least 12 beaked whale mass stranding events (involving two or more individuals) that coincided in space and time with naval exercises that may have used MFAS. Beaked whales compared to other cetacean species, are reported to be more vulnerable to severe and sometimes fatal responses to mid-frequency active sonar (MFAS) operations. We strongly recommend more visual monitoring efforts, at sea and along coastlines, for stranded cetaceans before, during and after naval exercises.īeaked whales (Family Ziphiidae) are a poorly understood family of 23 species of deep-diving cetaceans. We highlight strandings of individual BWs can be associated with ASW, and emphasize the value of ongoing passive acoustic monitoring, especially for beaked whales that are difficult to visually detect at sea. Half of these strandings occurred during or within 6 days after naval activities, and this co-occurrence is highly significant. Eight BW stranding events between June 2006 and January 2019 each included one to three animals. We compared the history of known naval operations and BW strandings from the Mariana Archipelago to consider potential threats to BW populations.
Both recorders documented MFAS on 21 August 2011 before two Cuvier's beaked whales stranded on 22–23 August 2011. Signals from Cuvier's ( Ziphius cavirostris) and Blainville's beaked whales ( Mesoplodon densirostris), and a third unidentified BW species, were detected throughout the recording period. We report BW and MFAS acoustic activity near the islands of Saipan and Tinian from March 2010 to November 2014. Multinational naval ASW exercises have used MFAS offshore of the Mariana Archipelago semi-annually since 2006.
Mid-frequency active sonar (MFAS), used for antisubmarine warfare (ASW), has been associated with multiple beaked whale (BW) mass stranding events.
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