After a frustrating summer marked by very poor offshore weather conditions, everything came together in early August, allowing us to conduct a successful Controlled Exposure Experiment (CEE) with tactical mid-frequency sonar signals deployed by the USS Farragut. A brief weather window allowed our field team to deploy five satellite-linked dive recorders on Cuvier’s beaked whales Ziphius cavirostris on 4 and 5 August, adding to two tags that we deployed in late June.
On 07 August we relocated one of our satellite-tagged beaked whales, Zc135, just off the shelf break at The Point, 40 nautical miles east of Cape Hatteras. We were able to deploy a Digital Acoustic Tag (DTAG) on Zc22_219a, one of the two whales with Zc135 at approximately 10:00 local time from the RV Barber. DTAG placement was good – on the right flank just forward of the dorsal fin. The two tagged animals separated shortly after we deployed the DTAG, so we used a chartered fishing vessel to monitor Zc135 while the Barber followed Zc22_219a. The R/V Shearwater was not available.
While we were following the two focal whales, Dr. Brandon Southall, Chief Scientist of the Atlantic Behavioral Study, was running acoustic propagation models on shore and in frequent communication with the Farragut via Navy personnel in Norfolk, VA. We also had excellent real-time, direct ship-to-ship communication with the Farragut.
The CEE was flawless, lasting from 13:10 to 14:10 local time, with the Farragut initially positioned approximately 15 miles from the two focal whales. Both whales submerged shortly before the CEE commenced. We returned to shore, leaving the DTAG on Zc22_219a overnight. The DTAG was programmed to last for a 24-hour deployment, but there is always a risk that it could jettison early and be advected away from the study area by the Gulf Stream.
The next morning, we relocated Zc135 using another chartered fishing vessel. The Barber commenced searching for Zc22_219a and at 10:45 we heard the VHF signal from the DTAG which had been jettisoned on schedule and floated to the surface. We tracked the DTAG for three miles and recovered it, with 24 hours of data onboard, just after 11:00.
We are currently in the process of examining the rich trove of data from this successful CEE. Field experiments like this one are complex and challenging and we are very fortunate to have a very highly skilled field team, including Zach Swaim, Daniel Webster, Danielle Waples, Danielle Alvarez, Kate Sutherland, Annie Harshbarger, and Dr. Will Cioffi. This is the second CEE we have conducted with the Farragut and we are very particularly grateful for the commitment and skill of its crew and officers. Our work is conducted under Marine Mammal Protection Act permits issued by the National Marine Fisheries Service and is funded by U.S. Fleet Forces Command, as part of the Navy’s Marine Species Monitoring Program, managed by Naval Facilities Engineering Systems Command Atlantic and supported by HDR Inc.