Passive Acoustic Monitoring: PRIEST (Pacific Right Whale Evaluation Study)
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The PRIEST project is a multiyear study of the distribution, abundance, and habitat use of North Pacific right whales in the North Aleutian Basin and southeastern Bering Sea using aerial and vessel surveys. There are three separate acoustic components within the PRIEST effort (Fig. 2).
Over 300 DiFAR sonobuoys were deployed throughout the entire 2008 field season to maintain 24 hr/day passive acoustic monitoring for right whale calls. Our estimated acoustic detection range was 5-10 mi during the cruise. Both right whale upsweep and gunshot calls were detected (Fig. 3).
The spatial distribution of the presence of these sounds on the sonobuoys is shown in Figure 4. If a call was detected, the acousticians could then direct the vessel to within sighting distance of the whale.
In 2007, the sonobuoys used were over 30 years old and had a poor success rate. For this reason, we are extremely grateful to Jeff Leonard (Naval Surface Warfare Center, Crane Division) and Theresa Yost (Naval Operational Logistics Support Center) for providing 15 pallets of newer surplus DiFAR buoys, which performed remarkably well.
Three EAR recorders (recording up to 2 kHz on a 10% duty cycle for a year) were also deployed within the North Aleutian Basin Lease Area on PMEL-built subsurface moorings (Fig. 5) designed for use in heavily-trawled locations.
Some of the highest costs associated with long-term acoustic recorder moorings, especially in the remote areas we need to monitor, are the moorings themselves and the ship-time required to transit to the mooring site and deploy the moorings. For this reason, we are fortunate to have the opportunity to occupy four moorings deployed by Phyllis Stabeno (PMEL/AFSC Ecosystems and Fisheries-Oceanography Coordinated Investigations (EcoFOCI)) in the Bering Sea.
The M2 and M4 moorings have Haruphones (recording up to 1 kHz continuously for a year), while AURALs (recording up to 4 kHz on a 30% duty cycle for a year) have been included on the M5 and M8 moorings. These instruments extend acoustic monitoring initiated near M2 in October 2000.
The BOWFEST project is a multiyear study on the feeding ecology of bowhead whales in the western Beaufort Sea. Passive acoustic surveillance began in 2007 when six AURAL recorders were deployed in an arc off Barrow, Alaska (Fig. 6).
Four of these recorders were moored along the 100-m isobath on PMEL-built subsurface moorings (Fig. 7), while the others were kindly piggybacked on two of Steve Okkonen's (University of Alaska–Fairbanks) shorter-term oceanographic moorings (Figs. 6, 8) in shallower water.
One of Okkonen's moorings was retrieved at the end of the 2007 season; but, unfortunately, the other was lost. During the 2008 field season, Kate Stafford (APL-UW) retrieved the four off-shore moorings and redeployed them, along with the fifth AURAL and two of her own (National Oceanographic Partnership Program (NOPP)-funded) AURALs, to make two 3-unit arrays and one single mooring (Fig. 6).
In addition, a pilot outreach study involving acoustic localization of bowhead whales, correlated with visual observations, was begun using four hand-deployable short-term PMEL-built EAR moorings (Fig. 6).
IPY (International Polar Year)
Compared to the PRIEST and BOWFEST projects, our IPY project was relatively straightforward: AURAL recorders (recording up to 4 kHz on a 30% duty cycle for a year) were installed on subsurface oceanographic moorings in the Chukchi Sea, Fram Strait, and NW Svalbard (Fig. 9) by collaborating scientists Humfrey Melling (Institute of Ocean Sciences, Sidney, BC, Canada), Ursula Schauer and Dirk Kalmbach (Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany), and Oystein Wiig (Natural History Museum, University of Oslo, Oslo, Norway), respectively.
Ultimately, acoustic data from these three recorders will be integrated with data obtained from recorders deployed by other researchers in the Alaskan and Canadian Beaufort Seas, providing a synoptic record of marine mammals and baseline ambient noise levels for roughly one-half of the Arctic continental shelf seas.
