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Heide-Jorgensen M.P.,Greenland Institute of Natural Resources | Nielsen N.H.,Greenland Institute of Natural Resources | Hansen R.G.,Greenland Institute of Natural Resources | Schmidt H.C.,Greenland Institute of Natural Resources | And 3 more authors.
Journal of Zoology | Year: 2015

Comparison of behavioural similarities between subpopulations of species that have been isolated for a long time is important for understanding the general ecology of species that are under pressure from large-scale changes in habitats. Narwhals (Monodon monoceros) east and west of Greenland are examples of separated populations that, in different ocean parts, will be coping with similar anthropogenic and climate-driven habitat alterations. To study this, 28 narwhals from the Scoresby Sound fjord system were tracked by satellite in 2010-2013. The average duration of contact with the whales was 124 days with one tag lasting 305 days and one whale recaptured <1km from its tagging site 366 days later. All whales exhibited the same migratory pattern. The whales departed from the summering grounds in Scoresby Sound in September and arrived at the edge of the continental shelf by November. Here, they stayed through May-June and conducted daily dives to the mesopelagic zone at ∼1000m depth. Despite the isolation by the landmass of Greenland and the genetic differentiation from other narwhal populations, there is still a remarkable similarity not just in behavioural traits like phenology of migrations and movements in relation to sea ice formation, but also in site fidelity, diving behaviour, feeding ecology, habitat selection, daily travel speed and even potential conflicts with fisheries for Greenland halibut (Reinhardtius hippoglossoides). Greenland halibut are likely target prey during the deep dives in winter but capelin (Mallotus villosus) may, with ocean warming, become of increasing importance. The ocean-wide predictability in culturally inherited migration patterns, size of wintering grounds and habitat selection among narwhal populations is certainly different from other Arctic cetaceans and renders narwhals more vulnerable to large-scale changes in their restricted and specialized habitats. Journal of Zoology © 2015. Source

Holst M.,LGL Ltd | Greene Jr. C.R.,Greeneridge science Inc. | Richardson W.J.,LGL Ltd | McDonald T.L.,West Inc. | And 3 more authors.
Aquatic Mammals | Year: 2011

To document the responses of pinnipeds to launches of missiles and similar aerial vehicles, three species of pinnipeds were observed during 77 launches from Navy-owned San Nicolas Island off California from August 2001 to October 2008. Pinniped behavior and flight sounds during each launch were recorded by unattended video cameras and acoustic recorders set up around the island's periphery, usually in pairs, as vehicles flew over or near haul-out sites. Multiple logistic regression was used to assess dependence of pinniped responses on received sound, distance from flight path, type of vehicle, and natural fac-tors. The majority of observed California sea lions (Zalophus californianus) startled and showed increased vigilance up to 2 min after each launch; responses often included movement on the beach or into the water and were significantly related to received sound level and distance from the vehicle's closest point of approach. Most observed northern elephant seals (Mirounga angustirostris) showed little reaction to launches and merely raised their heads briefly. Nonetheless, their responses were also related to received sound level and distance from vehicle trajectory. The harbor seal (Phoca vit-ulina) was the most responsive species. During the majority of launches, most (average 68%; range 7 to 100%) observed harbor seals within ~4 km of the launch trajectory left their haul-out site by entering the water; harbor seals hauled out again at the same site several hours after a launch. Within the range of conditions studied, there was no clear correlation between harbor seal response and received sound level or distance from the closest point of approach of the vehicle. Despite these short-term behavioral reactions, the effects of launch operations are likely to have been minor and localized, with no conse-quences for local pinniped populations as pinniped population sizes on San Nicolas Island are stable or increasing. Source

Thode A.M.,University of California at San Diego | Kim K.H.,Greeneridge science Inc. | Norman R.G.,Greeneridge science Inc. | Blackwell S.B.,Greeneridge science Inc. | Greene C.R.,Greeneridge science Inc.
Journal of the Acoustical Society of America | Year: 2016

Masking from industrial noise can hamper the ability to detect marine mammal sounds near industrial operations, whenever conventional (pressure sensor) hydrophones are used for passive acoustic monitoring. Using data collected from an autonomous recorder with directional capabilities (Directional Autonomous Seafloor Acoustic Recorder), deployed 4.1 km from an arctic drilling site in 2012, the authors demonstrate how conventional beamforming on an acoustic vector sensor can be used to suppress noise arriving from a narrow sector of geographic azimuths. Improvements in signal-to-noise ratio of up to 15 dB are demonstrated on bowhead whale calls, which were otherwise undetectable using conventional hydrophones. © 2016 Acoustical Society of America. Source

Abadi S.H.,University of Michigan | Thode A.M.,University of California at San Diego | Blackwell S.B.,Greeneridge science Inc. | Dowling D.R.,University of Michigan
Journal of the Acoustical Society of America | Year: 2014

This paper presents the performance of three methods for estimating the range of broadband (50-500 Hz) bowhead whale calls in a nominally 55-m-deep waveguide: Conventional mode filtering (CMF), synthetic time reversal (STR), and triangulation. The first two methods use a linear vertical array to exploit dispersive propagation effects in the underwater sound channel. The triangulation technique used here, while requiring no knowledge about the propagation environment, relies on a distributed array of directional autonomous seafloor acoustics recorders (DASARs) arranged in triangular grid with 7 km spacing. This study uses simulations and acoustic data collected in 2010 from coastal waters near Kaktovik, Alaska. At that time, a 12-element vertical array, spanning the bottom 63% of the water column, was deployed alongside a distributed array of seven DASARs. The estimated call location-to-array ranges determined from CMF and STR are compared with DASAR triangulation results for 19 whale calls. The vertical-array ranging results are generally within ±10% of the DASAR results with the STR results providing slightly better agreement. The results also indicate that the vertical array can range calls over larger ranges and with greater precision than the particular distributed array discussed here, whenever the call locations are beyond the distributed array boundaries. © 2014 Acoustical Society of America. Source

Clark C.W.,Cornell University | Berchok C.L.,National Oceanic and Atmospheric Administration | Blackwell S.B.,Greeneridge science Inc. | Hannay D.E.,JASCO Applied science | And 3 more authors.
Progress in Oceanography | Year: 2015

Bowhead whales, Balaena mysticetus, in the Bering-Chukchi-Beaufort (BCB) population, experience a variable acoustic environment among the regions they inhabit throughout the year. A total of 41,698. h of acoustic data were recorded from 1 August 2009 through 4 October 2010 at 20 sites spread along a 2300. km transect from the Bering Sea to the southeast Beaufort Sea. These data represent the combined output from six research teams using four recorder types. Recorders sampled areas in which bowheads occur and in which there are natural and anthropogenic sources producing varying amounts of underwater noise. We describe and quantify the occurrence of bowheads throughout their range in the Bering, Chukchi, and Beaufort seas over a 14-month period by aggregating our acoustic detections of bowhead whale sounds. We also describe the spatial-temporal variability in the bowhead acoustic environment using sound level measurements within a frequency band in which their sounds occur, by dividing a year into three, 4-month seasons (Summer-Fall 2009, August-November 2009: Winter 2009-2010, December 2009-March 2010: and Spring-Summer 2010, April-July 2010) and their home range into five zones. Statistical analyses revealed no significant relationship between acoustic occurrence, distance offshore, and water depth during Summer-Fall 2009, but there was a significant relationship during Spring-Summer 2010. A continuous period with elevated broadband sound levels lasting ca. 38. days occurred in the Bering Sea during the Winter 2009-2010 season as a result of singing bowheads, while a second period of elevated levels lasting at least 30. days occurred during the early spring-summer season as a result of singing bearded seals. The lowest noise levels occurred in the Chukchi Sea from the latter part of November into May. In late summer 2009 very faint sounds from a seismic airgun survey approximately 700. km away in the eastern Beaufort Sea were detected on Chukchi recorders. Throughout the year, but most obviously during the November into May period, clusters of intermittent, nearly synchronized, high-level events were evident on multiple recorders hundreds of miles apart. In some cases, these clusters occurred over 2-5. day periods and appear to be associated with high wind conditions. © 2015 Elsevier Ltd. Source

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