High-frequency Acoustic Recording Packages Research Articles

Migrating gray whale vocalizations and concurrent visual observations near Santa Barbara, California

The vocalizations of migrating eastern North Pacific gray whales (Eschrichtius robustus) are not well understood, but studying these sounds may provide insights to their behaviors and encounters along their migratory route. To record migratory gray whale sounds over long periods, a high frequency acoustic recording package (HARP) was deployed from March to May 2010 off the north coast of the Santa Barbara Channel, an area where the gray whale northbound migration is close to shore. The HARP recorded continuously and concurrently with a shore-based visual survey of marine mammals. Comparisons of calls and sightings were conducted to relate calling repertoires with various types of migrating whale behaviors and groups (e.g., cow/calf pairs, juveniles, etc.). The spatial and temporal overlap of the visual and acoustic data enabled the estimation of call detection ranges and source levels. Characterization of gray whale vocalizations also will help with the development of automatic detectors which will aid in future the investigations of long-term gray whale recordings, including potential responses to anthropogenic activity.

Ocean conditions and occurrence of cetacean species near Pt. Sur, California, in 2008–2010

The central California region of the California Current system is characterized by rich marine life and highly variable physical and biological ocean conditions. Here, patterns of marine mammal occurrence near Point Sur are analyzed and linked to seasonal and larger scale variability of the California Current system. A summary of marine mammal vocalizations was created by scanning passive acoustic recordings in the 10–100 kHz frequency band acquired with High-frequency Acoustic Recording Packages (HARPs) deployed at depth of approximately 840 m from August 2008–November 2010. Calls of detected baleen and toothed whales were presented as occurrence time diagrams. To characterize the ocean conditions of the California Current system during this time period, various datasets were used including current meter data collected at Sur Ridge and satellite-derived information on chlorophyll-a concentration (MODIS), temperature (AVHRR), and sea surface height anomalies (AVISO SSH products). Data series of chlorophyl...

Passive acoustic and visual monitoring of humpback whales (Megaptera novaeangliae) in the Olympic Coast National Marine Sanctuary: Importance of quantifying call type

Humpback whales (Megaptera novaeangliae) produce a variety of vocalizations such as social and feeding calls as well as patterned calls that comprise song. Typically, social and feeding vocalizations do not follow the highly structural format of song. High-frequency acoustic recording packages were deployed in the Olympic Coast National Marine Sanctuary July 2004 through June 2009 while visual surveys were conducted throughout the year at approximately monthly intervals. Humpback whales were detected visually and acoustically; however, there was a mismatch in the peak seasonality of these detections. Visual detections occurred in all seasons but peaked in summer and early fall. Acoustic detections were documented primarily in late summer to early winter. Male humpback whales are known to produce long songs primarily during their winter breeding season. To test whether the detection differences between visual and acoustic surveys could be explained by changes in the whales' vocal behavior, we quantified the relative occurrence of song and non-song calling using a variety of metrics and related the occurrence to the visual survey sightings. We show how identification of the type of acoustic detection is an important consideration and can help address biases introduced by seasonal differences in the production rate of reproduction-related calls.

Acoustic monitoring of dolphin populations in the Gulf of Mexico

High-Frequency Acoustic Recording Packages (HARPs) continuously monitored delphinids at five sites in the northeastern Gulf of Mexico during and after the Deepwater Horizon oil spill. Surface oil reached two sites, while the three unexposed sites functioned as “controls.” Presence of dolphin vocalizations (clicks, whistles, and burst pulses) was documented at exposed and unexposed sites over the course of a year following the oil spill. These sites are within the known habitat ranges of 11 species of delphinids. Broadband towed array recordings with visual identifications were used to determine species-specific vocalization characteristics, which were then compared with autonomously recorded vocalizations. Two species have distinctive vocalizations that match between towed array and autonomous recordings. At least four more unique vocalization patterns were detected autonomously, which may be species-specific. Both clicks and whistles were explored for identifying features. The data provide a comparative ...

Passive acoustic monitoring of sperm whales during and after the Deepwater Horizon oil spill

The Deepwater Horizon oil spill during the summer of 2010 impacted a region of sperm whale habitat along the continental slope and deep waters of the Gulf of Mexico. Passive acoustic monitoring was used to study the potential impact of the oil spill on sperm whales by recording trends in their characteristic sounds, such as echolocation clicks and foraging creaks. High-frequency Acoustic Recording Packages (HARPs) were deployed shortly after the oil spill began; one was located close to the Deepwater Horizon well, above which the sea surface was contaminated by oil throughout the summer of 2010, and another was deployed in a region of sperm whale habitat that remained unexposed to surface oil to function as a “control” site. At both sites, sperm whales were detected on a majority of days during the nearly year-long recording period. Sperm whale presence was evaluated from detected clicks and creaks, and changes in these sounds over time and between sites were compared.

Marine mammal vocalizations and shipping patterns off the California coast near Sur Ridge

Studying the effects of anthropogenic noise on marine life is the focus of many ongoing research efforts, and regional studies can provide useful insight into the broader issues. Waters off the central California coast are well known for the rich occurrence of a variety of marine mammal species. The region also contains important ship routes used by vessels transiting between major US west coast ports. Here, we examine the relationship between marine mammal vocalizations collected near Sur Ridge and local shipping patterns determined from automatic identification system (AIS) reports broadcast by ships passing through the region. Passive acoustic recordings of vocalizations were acquired with a moored high-frequency acoustic recording package (HARP) over the frequency bandwidth 10 Hz–100 kHz. Number of vessels within several different radii from the HARP mooring is correlated with presence/absence data of several baleen whale, beaked whale, and dolphin species over 5-min intervals between January 2009 and November 2010. We also examine whether diel patterns of marine mammal distribution are influenced by diel patterns in ship traffic. These data will be useful for establishing mammal-vessel interaction rates in the Monterey Bay National Marine Sanctuary. [Research supported by US Navy CNO(N45)].

Acoustic monitoring of killer whale populations off the west coast of Vancouver Island.

Killer whales inhabiting the waters of British Columbia and Washington are at risk. The occurrence of these animals has been extensively monitored in protected inshore waters off the east coast of Vancouver Island and Puget Sound, but there has been very little visual effort off Southwestern Vancouver Island and Washington. The objective of this study is to use acoustic techniques to determine the seasonal use of that area by different lineages of killer whales. Other questions include whether the current critical habitat needs to be expanded, or if there is any habitat sharing between different populations. Long-term acoustic data were obtained from passive acoustic devices including high frequency acoustic recording packages at three different sites. The recordings were analyzed using long term spectral averages, a tool that allows efficient analysis of large data sets in shorter periods of time. California-type transient calls were heard throughout the year, Southern Residents were detected from February through June, and Northern Residents were found from July through September. These results show a considerable overlap in habitat range between Southern and Northern Residents, as the latter use the southern parts of their range more frequently than previously thought.

Discriminating features of echolocation clicks of melon-headed whales (Peponocephala electra), bottlenose dolphins (Tursiops truncatus), and Gray’s spinner dolphins (Stenella longirostris longirostris)

Spectral parameters were used to discriminate between echolocation clicks produced by three dolphin species at Palmyra Atoll: melon-headed whales (Peponocephala electra), bottlenose dolphins (Tursiops truncatus) and Gray's spinner dolphins (Stenella longirostris longirostris). Single species acoustic behavior during daytime observations was recorded with a towed hydrophone array sampling at 192 and 480 kHz. Additionally, an autonomous, bottom moored High-frequency Acoustic Recording Package (HARP) collected acoustic data with a sampling rate of 200 kHz. Melon-headed whale echolocation clicks had the lowest peak and center frequencies, spinner dolphins had the highest frequencies and bottlenose dolphins were nested in between these two species. Frequency differences were significant. Temporal parameters were not well suited for classification. Feature differences were enhanced by reducing variability within a set of single clicks by calculating mean spectra for groups of clicks. Median peak frequencies of averaged clicks (group size 50) of melon-headed whales ranged between 24.4 and 29.7 kHz, of bottlenose dolphins between 26.7 and 36.7 kHz, and of spinner dolphins between 33.8 and 36.0 kHz. Discriminant function analysis showed the ability to correctly discriminate between 93% of melon-headed whales, 75% of spinner dolphins and 54% of bottlenose dolphins.

From mysticete song to odontocete echolocation: Monitoring cetacean sounds with high-frequency acoustic recording packages (HARPs).

Marine mammals produce a wide range of sounds from 10s of Hz to 100s of kHz. To remotely monitor these various sounds with autonomous systems, instruments with wide bandwidths are required. A general purpose, autonomous, high-frequency acoustic recording package (HARP) is described that can record sounds ranging from low-frequency blue whale (Balaenoptera musculus) song to mid-frequency dolphin whistles and beaked whale sweeps to high-frequency dolphin clicks. In addition to monitoring marine mammals, sounds from fish, contributions from wind and rain, and anthropogenic sources such as ships and sonar also are recorded potentially allowing for the study of cetacean behavioral response to these sounds. HARPs have been deployed for periods of up to one year, in various configurations such as standard moorings, seafloor packages, and arrays, and in remote locations including the Arctic, Bering Sea, Gulf of California, around Hawaii, and offshore of Washington State and southern California. The various configurations of these deployments and the wide range of marine mammal monitoring data they have provided are discussed in addition to lessons learned from these studies. [Work supported by the U.S. Navy CNO-N45.]

Acoustic tracking of whistling dolphins offshore of Southern California.

Dolphin whistles were recorded near San Clemente Island, offshore of Southern California, by four autonomous high-frequency acoustic recording packages (HARPs) deployed in a sea-floor array (dimensions: 2 km × 2 km) centered around the R/P FLIP. This array layout allowed localization of the calling animals using time difference of arrivals (TDOAs) from the same calls simultaneously recorded on the four instruments. Whistle TDOAs were calculated using cross-correlations of spectrograms. A matched-field least-squares minimization procedure used whistle TDOAs to localize the animals. Successive localizations were combined to track movement over time, revealing local movements of presumably common dolphins (Delphinus spp.), typically during elevated nocturnal activity. These tracks, coupled with the animals’ acoustic activity, provide insight into their behavior and could potentially be used to study their response to various stimuli including anthropogenic sources such as sonar. [This research is supported by CNO-N45.]

High-frequency Acoustic Recording Package (HARP) for long-term monitoring of marine mammals

Advancements in low-power and high-data-capacity computer technology during the past decade have been adapted to autonomously record sounds from marine mammals over long time periods. Acoustic monitoring has advantages over traditional visual surveys including greater detection ranges, continuous long-term monitoring in remote locations under various weather conditions, and lower cost. However, until recently, the technology required to autonomously record whale sounds over long durations has been limited to low-frequency ( ‘ 1000 Hz) baleen whales. The need for a broader-band, higher-data capacity system capable of autonomously recording toothed whales and other marine mammals for long periods has prompted the development of a High-frequency Acoustic Recording Package (HARP) capable of sample rates up to 200 kHz. The HARP design is described and data analysis strategies are discussed using examples of broadband recorded data. [Work supported by the U.S. Navy CNO-N45.]

Acoustic monitoring of resident, offshore, and transient killer whales off the Washington coast

Three acoustically distinct populations of killer whales representing each of the known ecotypes (resident, offshore, transient) were recorded in the Summer–Fall of 2004 off the southern Olympic Coast of Washington. Two high-frequency acoustic recording packages (HARPs) continuously recording at 80-kHz sample rate were deployed to assess the seasonal occurrence of vocal odontocetes in this region. From mid-July to early-October the population-specific discrete calls of killer whales were heard on 8 days and were classified to population by Volker Deecke (UBC) and John Ford (DFO-Canada) using an acoustic ID catalogue. West Coast Transient killer whales producing calls of the California dialect were heard on three occasions from August through October. Offshore killer whales were heard twice in August–September, and Northern Resident killer whales were heard once in August. Although Northern Resident killer whales have been extensively studied within Puget Sound and coastal British Columbia, they have been visually sighted only once off the northern Olympic Peninsula, making their detection at this offshore southerly location unique. Endangered Southern Resident killer whales were not heard at this site from July–October. Analysis of year-round data from a site further offshore is underway. [Funded by Chief of Naval Operations- N45.]

High-frequency Acoustic Recording Package (HARP) for long-term monitoring of marine mammals

Advancements in low-power and high-data-capacity computer technology during the past decade have been adapted to autonomously record sounds from whales over long time periods. Acoustic monitoring of whales has advantages over traditional visual surveys including greater detection ranges, continuous long-term monitoring in remote locations under various weather conditions, and lower cost. One currently used tool for providing long-term acoustic monitoring of marine mammals is an autonomous acoustic recording package (ARP) which uses a tethered hydrophone above a seafloor-mounted instrument frame. Since 2000, ARPs have been deployed to record baleen whale sounds in the Bering Sea, in the Beaufort Sea, in the Gulf of Alaska, off the coast of southern California, around Antarctica and near Hawaii. ARP data have provided new information on the seasonal presence, abundance, call character and patterns of calling whales. The need for a broader-band, higher-data capacity system capable of recording odontocete whales, dolphins and porpoises for long time periods has prompted the development of a High-frequency Acoustic Recording Package (HARP). The HARP design is described and data analysis strategies are discussed using examples of HARP broad-band (sample rates up to 200 kHz) recorded data.