Long-term passive acoustic recordings track the changing distribution of North Atlantic right whales (Eubalaena glacialis) from 2004 to 2014.

Given new distribution patterns of the endangered North Atlantic right whale (NARW; Eubalaena glacialis) population in recent years, an improved understanding of spatio-temporal movements are imperative for the conservation of this species. While so far visual data have provided most information on NARW movements, passive acoustic monitoring (PAM) was used in this study in order to better capture year-round NARW presence. This project used PAM data from 2004 to 2014 collected by 19 organizations throughout the western North Atlantic Ocean. Overall, data from 324 recorders (35,600 days) were processed and analyzed using a classification and detection system. Results highlight almost year-round habitat use of the western North Atlantic Ocean, with a decrease in detections in waters off Cape Hatteras, North Carolina in summer and fall. Data collected post 2010 showed an increased NARW presence in the mid-Atlantic region and a simultaneous decrease in the northern Gulf of Maine. In addition, NARWs were widely distributed across most regions throughout winter months. This study demonstrates that a large-scale analysis of PAM data provides significant value to understanding and tracking shifts in large whale movements over long time scales.

Bowhead whale acoustic activity in the southeast Beaufort Sea during late 2008-2010.

Autonomous passive acoustic recorders were deployed to record sounds of bowhead whales (Balaena mysticetus) in the southeast Beaufort Sea for periods of 30-55 days during the late summer, open-water seasons of 2008-2010. Recordings were made in three areas licensed for hydrocarbon exploration, spanning the continental slope and adjacent outer shelf, and in a shallow inner-shelf area where bowheads have been observed congregating to feed in recent decades. Bowhead sounds were counted in samples comprising 10% of each recorded hour. In mid-August and September in all 3 years, the rate of bowhead calling at outer shelf sites exceeded that at adjacent continental slope sites by one to two orders of magnitude. Higher rates of calling occurred on the slope in late July and early August than at later dates. Calling rates varied by an order of magnitude between years in the one area that was monitored in different years. The highest rates of calling occurred on the inner shelf, offshore of the northern Tuktoyaktuk Peninsula. These trends are consistent with patterns of habitat use previously reported from aerial surveys in this and nearby areas of the Beaufort Sea and with the results of satellite tagging studies.

Low frequency vocalizations attributed to sei whales (Balaenoptera borealis).

Low frequency (<100 Hz) downsweep vocalizations were repeatedly recorded from ocean gliders east of Cape Cod, MA in May 2005. To identify the species responsible for this call, arrays of acoustic recorders were deployed in this same area during 2006 and 2007. 70 h of collocated visual observations at the center of each array were used to compare the localized occurrence of this call to the occurrence of three baleen whale species: right, humpback, and sei whales. The low frequency call was significantly associated only with the occurrence of sei whales. On average, the call swept from 82 to 34 Hz over 1.4 s and was most often produced as a single call, although pairs and (more rarely) triplets were occasionally detected. Individual calls comprising the pairs were localized to within tens of meters of one another and were more similar to one another than to contemporaneous calls by other whales, suggesting that paired calls may be produced by the same animal. A synthetic kernel was developed to facilitate automatic detection of this call using spectrogram-correlation methods. The optimal kernel missed 14% of calls, and of all the calls that were automatically detected, 15% were false positives.