Karolin Klinck

Sounds from airguns and fin whales recorded in the mid-Atlantic Ocean, 1999–2009

Between 1999 and 2009, autonomous hydrophones were deployed to monitor seismic activity from 16° N to 50° N along the Mid-Atlantic Ridge. These data were examined for airgun sounds produced during offshore surveys for oil and gas deposits, as well as the 20 Hz pulse sounds from fin whales, which may be masked by airgun noise. An automatic detection algorithm was used to identify airgun sound patterns, and fin whale calling levels were summarized via long-term spectral analysis. Both airgun and fin whale sounds were recorded at all sites. Fin whale calling rates were higher at sites north of 32° N, increased during the late summer and fall months at all sites, and peaked during the winter months, a time when airgun noise was often prevalent. Seismic survey vessels were acoustically located off the coasts of three major areas: Newfoundland, northeast Brazil, and Senegal and Mauritania in West Africa. In some cases, airgun sounds were recorded almost 4000 km from the survey vessel in areas that are likely occupied by fin whales, and at some locations airgun sounds were recorded more than 80% days/month for more than 12 consecutive months.

Seasonal presence of cetaceans and ambient noise levels in polar waters of the North Atlantic.

In 2009 two calibrated acoustic recorders were deployed in polar waters of the North Atlantic to study the seasonal occurrence of blue, fin, and sperm whales and to assess current ambient noise levels. Sounds from these cetaceans were recorded at both locations in most months of the year. During the summer months, seismic airguns associated with oil and gas exploration were audible for weeks at a time and dominated low frequency noise levels. Noise levels might further increase in the future as the receding sea ice enables extended human use of the area.

Confirmation of right whales near a nineteenth-century whaling ground east of southern Greenland.

North Atlantic right whales (Eubalaena glacialis) were found in an important nineteenth century whaling area east of southern Greenland, from which they were once thought to have been extirpated. In 2007–2008, a 1-year passive acoustic survey was conducted at five sites in and near the ‘Cape Farewell Ground’, the former whaling ground. Over 2000 right whale calls were recorded at these sites, primarily during July–November. Most calls were northwest of the historic ground, suggesting a broader range in this region than previously known. Geographical and temporal separation of calls confirms use of this area by multiple animals.

Temporal segregation of the Australian and Antarctic blue whale call types (Balaenoptera musculus spp.)

We examined recordings from a 15-month (May 2009–July 2010) continuous acoustic data set collected from a bottom-mounted passive acoustic recorder at a sample frequency of 6 kHz off Portland, Victoria, Australia (38°33′01″S, 141°15′13″E) off southern Australia. Analysis revealed that calls from both subspecies were recorded at this site, and general additive modeling revealed that the number of calls varied significantly across seasons. Antarctic blue whales were detected more frequently from July to October 2009 and June to July 2010, corresponding to the suspected breeding season, while Australian blue whales were recorded more frequently from March to June 2010, coinciding with the feeding season. In both subspecies, the number of calls varied with time of day; Antarctic blue whale calls were more prevalent in the night to early morning, while Australian blue whale calls were detected more often from midday to early evening. Using passive acoustic monitoring, we show that each subspecies adopts different seasonal and daily call patterns which may be related to the ecological strategies of these subspecies. This study demonstrates the importance of passive acoustics in enabling us to understand and monitor subtle differences in the behavior and ecology of cryptic sympatric marine mammals.

Long-range underwater vocalizations of the crabeater seal (Lobodon carcinophaga)

This study provides a comprehensive description of the acoustic characteristics of the predominant long-range underwater vocalizations of the crabeater seal, Lobodon carcinophaga, derived from stationary and continuous long-term recordings obtained in the Southern Ocean in 2007. Visual screening of data recorded between 1 October and 15 December 2007 indicates that the principal period of vocal activity of the crabeater seal is the latter part of October and all of November, coinciding with the breeding season of this species. Two call types were identified during this period: the low moan call, which has been described in previous studies and the high moan call, a call type newly described here. Out of 17 052 manually extracted crabeater seal calls, high-quality recordings of 152 low moans and 86 high moans with a signal-to-noise ratio exceeding 15 dB were selected and call-specific acoustic features were determined. While the mean duration of the two call types was comparable ( approximately 2.5 s), the high moan occurred at notably higher frequencies (1000-4900 Hz) than the low moan (260-2500 Hz). This study provides baseline information necessary to develop automated detection algorithms to facilitate systematic screening of extended data sets for crabeater seal vocalizations.

Passive‐acoustic monitoring of odontocetes using a Seaglider: First results of a field test in Hawaiian waters.

In fall 2009 the University of Washington, Applied Physics Laboratory conducted in collaboration with the Oregon State University, a comprehensive field test of a passive‐acoustic Seaglider along the western shelf‐break of the island of Hawaii. During the 3 week mission, a total of approximately 170 h of broadband acoustic data [194 kHz sampling rate] were collected. The recordings were manually analyzed by an experienced analyst for beaked whale (Ziphiidae), dolphin (Delphinidae), and sperm whale (Physeter macrocephalus) echolocation clicks as well as echo sounder pings emitted by boats in the area. Here we present and discuss first results of these data analysis, which revealed that more than 50% of the recorded files (each of 1‐minute duration) contain bioacoustic signals. Furthermore the recorded data and the results of the manual analysis are used to validate and optimize an automated classifier for odontocete echolocation clicks, which was developed in a collaborative effort with San Diego State Uni...

Right whale gunshot calls in the southeastern Bering Sea.

The eastern population of the North Pacific right whale (Eubalaena japonica) is critically endangered. Following extensive historical whaling in the 19th century and large illegal catches by the USSR in the 1960’s, it is likely that this population now numbers in the tens of animals. Little is known about the distribution, movements, migrations, or habitat use of this population, but the existing data suggest that it now occupies a reduced range compared to historical times. In 2007, NMML began conducting 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. During the 2008 survey, directional sonobuoys were used 24 h a day to record right whale calls and obtain cross‐bearings to the whales. Although previous work in the Bering Sea focused on detections of the right whale upsweep call, our findings suggest that the gunshot call is much more ubiquitous. Spatial and temporal tre...

Seismic airgun surveys and vessel traffic in the Fram Strait and their contribution to the polar soundscape

Low-frequency (<1 kHz) noise associated with human offshore activities has increased dramatically over the last 50 years. Of special interest are areas such as the Arctic where anthropogenic noise levels are relatively low but could change dramatically, as sea ice continues to shrink and trans-polar shipping routes open. In 2009, we began an annual deployment of two calibrated autonomous hydrophones in the Fram Strait to record underwater ambient sound continuously for one year at a sampling rate of 2 kHz. Ambient noise levels were summarized via long-term spectral average plots and reviewed for anthropogenic sources. Vessel traffic data were acquired from the Automatic Identification System (AIS) archive and ship density was estimated by weighting vessel tracklines by vessel length. Background noise levels were dominated by sounds from seismic airguns during spring, summer and fall months; during summer these sounds were recorded in all hours of the day and all days of a month. Ship density in the Fram S...

Software for viewing and checking automatic detections.

Automatic detection of animal vocalizations is now used widely for handling long‐duration recording. Automatic detection methods inevitably make some errors—both false positive (wrong detection) and false negative (missed call) errors. Here a system is described for checking these errors. The MATLAB system “Osprey” allows viewing spectrograms, manipulating their parameters, and making various measurements of the displayed sounds. Another program, “checkDetections”, takes a log file that was output by an automatic detection software and systematically displays the detected sound in Osprey, allows a user to indicate whether the detection is correct, and then skips to the next detection in the log. This allows for rapid checking of detected sounds and calculation of the false‐positive (wrong‐detection) error rate. A second system, “checkMissedCalls”, displays random segments of sound in which no calls were found and allows the user to check whether there really were calls. This allows the user to estimate th...

Acoustic rediscovery of right whales in a former whaling area, the Cape Farewell Ground, between Greenland and Iceland.

The North Atlantic right whale (Eubalaena glacialis) is one of the world’s most endangered cetaceans, with only 300–350 animals believed alive. Most right whales are thought to range from Florida to Nova Scotia, though the whereabouts of a significant portion of the population remains unknown in both winter and summer. Here we describe an acoustic survey for right whales near the Cape Farewell Ground, a late 18th‐century whaling area. Continuously recording autonomous hydrophone instruments were deployed at five sites for one year in 2007–2008, after which data were analyzed by automatic detection with manual checking for “up” calls of right whales. Over 2000 calls were detected in all, with calls found at all sites but mostly from near the Cape Farewell Ground. The data are consistent with a seasonal migration northeastward toward Iceland in July–August followed by return movement later in the fall, with the last detection in December. At one site, calling occurred in the fall on 17 separate occasions, s...