The Experts below are selected from a list of 31218 Experts worldwide ranked by ideXlab platform
David L Garshelis - One of the best experts on this subject based on the ideXlab platform.
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revisiting western hudson bay using Aerial Surveys to update polar bear abundance in a sentinel population
Biological Conservation, 2014Co-Authors: Seth P Stapleton, Stephen N Atkinson, Daryll Hedman, David L GarshelisAbstract:Abstract Capture-based studies of the Western Hudson Bay (WH) polar bear population in Canada have reported declines in abundance, survival, and body condition, but these findings are inconsistent with the perceptions of local people. To address this uncertainty about current status, we conducted a comprehensive Aerial Survey of this population during August, 2011, when the region was ice-free and bears were on shore. We flew a combination of overland transects oriented perpendicular to the coastline, coastal transects parallel to shore, and transects across small islands. We used distance sampling and sight–resight protocols to estimate abundance. Bears were concentrated along the coast in central and southern Manitoba and Ontario portions of the population, although sightings >10 km inland were not uncommon in central Manitoba. We analyzed 2 combinations of data and derived an abundance estimate of 1030 bears (95% CI: ∼754–1406). This figure is similar to a 2004 mark–recapture estimate but higher than projections indicating declining abundance since then. Our results suggest that mark–recapture estimates may have been negatively biased due to limited spatial sampling. We observed large numbers of bears summering in southeastern WH, an area not regularly sampled by mark–recapture. Consequently, previous mark–recapture estimates are not directly comparable to our Aerial Survey of the entire population. Whereas our results do not necessarily contradict the reported declines in this population, we believe that improvements are needed in monitoring, and methodological limitations and inconsistencies must be resolved to accurately assess status and the impacts of climate change.
Joshua Jones - One of the best experts on this subject based on the ideXlab platform.
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beluga whales in the western beaufort sea current state of knowledge on timing distribution habitat use and environmental drivers
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Kathleen M Stafford, Janet T Clarke, Stephen R Okkonen, Megan C Ferguson, Donna D W Hauser, Catherine L Berchok, John J Citta, Ellen C Garland, Joshua JonesAbstract:Abstract The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from Aerial Surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An Aerial Survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the Aerial Survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.
Donna D W Hauser - One of the best experts on this subject based on the ideXlab platform.
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beluga whales in the western beaufort sea current state of knowledge on timing distribution habitat use and environmental drivers
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Kathleen M Stafford, Janet T Clarke, Stephen R Okkonen, Megan C Ferguson, Donna D W Hauser, Catherine L Berchok, John J Citta, Ellen C Garland, Joshua JonesAbstract:Abstract The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from Aerial Surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An Aerial Survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the Aerial Survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.
Stephen R Okkonen - One of the best experts on this subject based on the ideXlab platform.
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beluga whales in the western beaufort sea current state of knowledge on timing distribution habitat use and environmental drivers
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Kathleen M Stafford, Janet T Clarke, Stephen R Okkonen, Megan C Ferguson, Donna D W Hauser, Catherine L Berchok, John J Citta, Ellen C Garland, Joshua JonesAbstract:Abstract The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from Aerial Surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An Aerial Survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the Aerial Survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.
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satellite observations of circulation features associated with a bowhead whale feeding hotspot near barrow alaska
Remote Sensing of Environment, 2011Co-Authors: Stephen R Okkonen, Janet T Clarke, Sue E Moore, Carin J Ashjian, Robert G Campbell, Kevin D TaylorAbstract:Abstract Satellite images, along with oceanographic, meteorological, and whale Aerial Survey data, are used to illustrate aspects of ocean circulation associated with a bowhead whale feeding ‘hotspot’ near Barrow, Alaska. In response to weak winds, a strong front forms near the shelf-break along the southern edge of Barrow Canyon when the Alaska Coastal Current flows adjacent to the southern flank of Barrow Canyon or intrudes onto the western Beaufort shelf. This front is of particular local interest because it is indicative of aggregation and retention of zooplankton on the western Beaufort shelf and, as a result, is a locus for bowhead whales pausing to feed during their westward fall migration. Groups (4 or more individuals) of bowhead whales are primarily seen on the western Beaufort shelf following wind conditions that promote the formation of this front.
Janet T Clarke - One of the best experts on this subject based on the ideXlab platform.
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beluga whales in the western beaufort sea current state of knowledge on timing distribution habitat use and environmental drivers
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Kathleen M Stafford, Janet T Clarke, Stephen R Okkonen, Megan C Ferguson, Donna D W Hauser, Catherine L Berchok, John J Citta, Ellen C Garland, Joshua JonesAbstract:Abstract The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from Aerial Surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An Aerial Survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the Aerial Survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.
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satellite observations of circulation features associated with a bowhead whale feeding hotspot near barrow alaska
Remote Sensing of Environment, 2011Co-Authors: Stephen R Okkonen, Janet T Clarke, Sue E Moore, Carin J Ashjian, Robert G Campbell, Kevin D TaylorAbstract:Abstract Satellite images, along with oceanographic, meteorological, and whale Aerial Survey data, are used to illustrate aspects of ocean circulation associated with a bowhead whale feeding ‘hotspot’ near Barrow, Alaska. In response to weak winds, a strong front forms near the shelf-break along the southern edge of Barrow Canyon when the Alaska Coastal Current flows adjacent to the southern flank of Barrow Canyon or intrudes onto the western Beaufort shelf. This front is of particular local interest because it is indicative of aggregation and retention of zooplankton on the western Beaufort shelf and, as a result, is a locus for bowhead whales pausing to feed during their westward fall migration. Groups (4 or more individuals) of bowhead whales are primarily seen on the western Beaufort shelf following wind conditions that promote the formation of this front.