The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Steven H. Ferguson - One of the best experts on this subject based on the ideXlab platform.
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Abundance estimation from genetic mark-recapture data when not all sites are sampled: An example with the Bowhead Whale
Global Ecology and Conservation, 2020Co-Authors: Timothy R. Frasier, Mads Peter Heide-jørgensen, Lianne D. Postma, Lucy Johnson, Stephen D Petersen, Steven H. FergusonAbstract:Abstract Estimating abundance is one of the most fundamental and important aspects of population biology, with major implications on how the status of a population is perceived and thus on conservation and management efforts. Although typically based on one of two methods (distance sampling or mark-recapture), there are many individual identification methods that can be used for mark-recapture purposes. In recent years, the use of genetic data for individual identification and abundance estimation through mark-recapture analyses have increased, and in some situations such genetic identifications are more efficient than their field-based counterparts for population monitoring. One issue with mark-recapture analyses, regardless of which method of individual identification is used, is that the study area must provide adequate opportunities for “capturing” all individuals within a population. However, many populations are unevenly and widely distributed, making it unfeasible to adequately sample all necessary areas. Here we develop an analytical technique that accounts for unsampled locations, and provides a means to infer “missing” individuals from unsampled locations, and therefore obtain more accurate abundance estimates when it is not possible to sample all sites. This method is validated using simulations and is used to estimate abundance of the Eastern Canada-West Greenland (EC-WG) Bowhead Whale population. Based on these analyses, the estimated size of this population is 11,747 individuals during the sampling period, with a 95% highest density interval of 8,169–20,043.
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Bayesian abundance estimation from genetic mark-recapture data when not all sites are sampled: an example with the Bowhead Whale
bioRxiv, 2019Co-Authors: Timothy R. Frasier, Mads Peter Heide-jørgensen, Lianne D. Postma, Lucy Johnson, Stephen D Petersen, Steven H. FergusonAbstract:Abstract Estimating abundance is one of the most fundamental and important aspects of population biology, with major implications on how the status of a population is perceived and thus on conservation and management efforts. Although typically based on one of two methods (distance sampling or mark-recapture), there are many individual identification methods that can be used for mark-recapture purposes. In recent years, the use of genetic data for individual identification and abundance estimation through mark-recapture analyses have increased, and in some situations such genetic identifications are more efficient than their field-based counterparts for population monitoring. One issue with mark-recapture analyses, regardless of which method of individual identification is used, is that the study area must provide adequate opportunities for “capturing” all individuals within a population. However, many populations are unevenly and widely distributed, making it unfeasible to adequately sample all necessary areas. Here we develop an analytical technique that accounts for unsampled locations, and provides a means to infer “missing” individuals from unsampled locations, and therefore obtain more accurate abundance estimates when it is not possible to sample all sites. This method is validated using simulations and is used to estimate abundance of the Eastern Canada-West Greenland (EC-WG) Bowhead Whale population. Based on these analyses, the estimated size of this population is 11,747 individuals, with a 95% highest density interval of 8,169-20,043.
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reconstructing variability in west greenland ocean biogeochemistry and Bowhead Whale balaena mysticetus food web structure using amino acid isotope ratios
Polar Biology, 2017Co-Authors: Corinne Pomerleau, Steven H. Ferguson, Mads Peter Heidejorgensen, Harry L Stern, Jacob L Hoyer, Gary A SternAbstract:Climate change is causing physical and biological changes in the polar marine environment, which may impact higher trophic level predators such as the Bowhead Whale (Balaena mysticetus) and the structure of their food webs. We used bulk stable isotope analysis and compound-specific isotope analysis (CSIA) of individual amino acids (AA) to examine Bowhead Whale trophic position and the biogeochemistry of one of their feeding grounds, Disko Bay, West Greenland, over a period of 7 years (2007–2013). We also examined whether environmental conditions such as sea ice concentration and sea surface temperature were causing any interannual variation in isotope data. Bulk δ 15N values were consistent across the 7 years of sampling and were similar between sex classes. Bulk δ 13C and essential-AAs δ 13C values displayed an overall temporal decline of 1.0 and 1.4‰, respectively. A significant positive linear relationship was found between δ 13C of bulk skin and essential-AAs suggesting that some of the observed isotopic variation in Bowhead Whales between years reflect changes in the carbon at the base of the food web. There were no correlations between the δ 13C and δ 15N values of isotopic tracers with sea ice concentrations or sea surface temperatures. The trophic level of Bowhead Whales remained stable over time despite large interannual variability in ice and temperature regimes. Our results indicate that the recent environmental changes in West Greenland resulted in no trophic perturbation being transferred to Bowhead Whales during that time period. Our study shows that the novel approach of CSIA-AA can be used effectively to study the combined temporal variation of Bowhead Whale food web structure and ecosystem isotopic baseline values and detect changes at the species and ecosystem levels.
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Evidence of molting and the function of “rock-nosing” behavior in Bowhead Whales in the eastern Canadian Arctic - Fig 6
2017Co-Authors: Sarah M. E. Fortune, Jeff W Higdon, William R. Koski, Andrew W. Trites, Mark F. Baumgartner, Steven H. FergusonAbstract:Example of sloughing epidermis (A) located behind the blowholes of a Bowhead Whale (Balaena mysticetus) and mottled skin (B) found near the blowholes.
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killer Whale orcinus orca predation in a multi prey system
Population Ecology, 2012Co-Authors: Jeff W Higdon, Michael C S Kingsley, Steven H. FergusonAbstract:Predation can regulate prey numbers but predator behaviour in multiple-prey systems can complicate understanding of control mechanisms. We investigate killer Whale (Orcinus orca) predation in an ocean system where multiple marine mammal prey coexist. Using stochastic models with Monte-Carlo simulations, we test the most likely outcome of predator selection and compare scenarios where killer Whales: (1) focus predation on larger prey which presumably offer more energy per effort, (2) generalize by feeding on prey as encountered during searches, or (3) follow a mixed foraging strategy based on a combination of encounter rate and prey size selection. We test alternative relationships within the Hudson Bay geographic region, where evidence suggests killer Whales seasonally concentrate feeding activities on the large-bodied Bowhead Whale (Balaena mysticetus). However, model results indicate that killer Whales do not show strong prey specialization and instead alternatively feed on narwhal (Monodon monoceros) and beluga (Delphinapterus leucas) Whales early and late in the ice-free season. Evidence does support the conjecture that during the peak of the open water season, killer Whale predation can differ regionally and feeding techniques can focus on Bowhead Whale prey. The mixed foraging strategy used by killer Whales includes seasonal predator specialization and has management and conservation significance since killer Whale predation may not be constrained by a regulatory functional response.
Stephen R Okkonen - One of the best experts on this subject based on the ideXlab platform.
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lingering chukchi sea sea ice and chukchi sea mean winds influence population age structure of euphausiids krill found in the Bowhead Whale feeding hotspot near pt barrow alaska
PLOS ONE, 2021Co-Authors: Carin J Ashjian, Robert G Campbell, Stephen R Okkonen, Philip AlataloAbstract:Interannual variability in euphausiid (krill) abundance and population structure and associations of those measures with environmental drivers were investigated in an 11-year study conducted in late August-early September 2005-2015 in offshelf waters (bottom depth > 40 m) in Barrow Canyon and the Beaufort Sea just downstream of Distributed Biological Observatory site 5 (DBO5) near Pt. Barrow, Alaska. Statistically-significant positive correlations were observed among krill population structure (proportion of juveniles and adults), the volume of Late Season Melt Water (LMW), and late-spring Chukchi Sea sea ice extent. High proportions of juvenile and adult krill were seen in years with larger volumes of LMW and greater spring sea ice extents (2006, 2009, 2012-2014) while the converse, high proportions of furcilia, were seen in years with smaller volumes of LMW and lower spring sea ice extent (2005, 2007, 2010, 2011, 2015). These different life stage, sea ice and water mass regimes represent integrated advective responses to mean fall and/or spring Chukchi Sea winds, driven by prevailing atmospheric pressure distributions in the two sets of years. In years with high proportions of juveniles and adults, late-spring and preceding-fall winds were weak and variable while in years with high proportions of furcilia, late-spring and preceding-fall winds were strong, easterly and consistent. The interaction of krill life history with yearly differences in the northward transports of krill and water masses along with sea ice retreat determines the population structure of late-summer krill populations in the DBO5 region near Pt. Barrow. Years with higher proportions of mature krill may provide larger prey to the Pt. Barrow area Bowhead Whale prey hotspot. The characteristics of prey near Pt. Barrow is dependent on krill abundance and size, large-scale environmental forcing, and interannual variability in recruitment success of krill in the Bering Sea.
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relationships among high river discharges upwelling events and Bowhead Whale balaena mysticetus occurrence in the central alaskan beaufort sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Stephen R Okkonen, Janet T Clarke, Rachel A PotterAbstract:Abstract Aerial surveys for Bowhead Whales have been conducted with a relatively consistent methodology over the Alaskan Beaufort Sea since 1989. Sightings of Bowhead Whales in the central Alaskan Beaufort Sea in September 1997 and September 2014 were unusual in that hundreds of Whales were observed within a few kilometers of local barrier islands. We compare Bowhead Whale sightings, river discharge data, wind records, and satellite imagery to argue that the large numbers of Bowhead Whales observed nearshore in September 1997 and 2014 resulted from favorable feeding conditions established by high river discharges and prior upwelling events. These results are then generalized in a simple binary-based mechanistic framework that links the relevant physics to occurrences of observed and potential feeding opportunities for Bowhead Whales in the central Alaskan Beaufort Sea and in other locales along the Beaufort coast.
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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.
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episodic upwelling of zooplankton within a Bowhead Whale feeding area near barrow ak
2009Co-Authors: Carin J Ashjian, Robert G Campbell, Stephen R Okkonen, Kathleen M StaffordAbstract:Abstract : Our long term goals are to understand (1) the biological-physical oceanographic characteristics and mechanisms on the shelf near Barrow, AK that together produce a favorable feeding environment for the Bowhead Whale there and (2) the potential impact of climate change, particularly the ongoing reduction in sea ice and variability in Pacific Water presence near Barrow, on this feeding environment. This region is a critical feeding area for migrating Bowhead Whales, particularly during the fall migration (e.g., Lowry et al., 2004). Results from biophysical sampling conducted during August-September 2005- 2008 demonstrated that the oceanography of the shelf is complex, dynamic, and highly variable and that advection is closely coupled to the direction and magnitude of the winds. In addition, oceanographic and atmospheric conditions impact the composition, distribution, and availability of plankton prey for the Bowhead Whale. Assessment and understanding of interannual and longer-term variability in the physical mechanisms influencing ocean conditions and the resulting distribution and abundance of plankton on the shelf are necessary to predict potential impacts of climate change.
Janet T Clarke - One of the best experts on this subject based on the ideXlab platform.
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Bowhead Whale balaena mysticetus and killer Whale orcinus orca co occurrence in the u s pacific arctic 2009 2018 evidence from Bowhead Whale carcasses
Polar Biology, 2020Co-Authors: Raphaela Stimmelmayr, Amy L Willoughby, Megan C Ferguson, Janet T Clarke, Amelia A BrowerAbstract:Imagery and sighting data on Bowhead Whale (Balaena mysticetus) carcasses documented from 2009 to 2018 during aerial surveys in the eastern Chukchi and western Beaufort seas have provided evidence for killer Whale (Orcinus orca) predation on Bowhead Whales of the Bering–Chukchi–Beaufort Seas stock. The Aerial Surveys of Arctic Marine Mammals (ASAMM) project provides information on distribution, behavior, and relative density of marine mammals. ASAMM surveys large areas of Bowhead Whale and killer Whale summer and autumn habitat and offers consistent information on Bowhead Whale carcasses. Thirty-three Bowhead Whale carcasses were documented in July–October, from 2009 to 2018. Carcasses were distributed across the eastern Chukchi and western Beaufort seas from 141.6° W to 168.1° W and 68.9° N to 72.0° N. Carcass sighting rates (carcasses/1000 km) varied by month, year, and region. Statistical results suggest an alternating series of high and low annual carcass sighting rates. Eighteen Bowhead Whale carcasses having injuries consistent with probable killer Whale predation were photo-documented: four each in 2016 and 2018, three each in 2013 and 2015, two in 2012, and one each in 2010 and 2017. Four carcasses, two in 2015 and one each in 2013 and 2018, were likely Whales struck and lost during aboriginal subsistence hunting. Cause of death could not be determined for 11 carcasses. This study is the first systematic inquiry into non-harvest related mortality of Bowhead Whales in the U.S. Pacific Arctic and provides multi-year evidence for killer Whale predation on Bowhead Whales in this portion of their range.
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relationships among high river discharges upwelling events and Bowhead Whale balaena mysticetus occurrence in the central alaskan beaufort sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Stephen R Okkonen, Janet T Clarke, Rachel A PotterAbstract:Abstract Aerial surveys for Bowhead Whales have been conducted with a relatively consistent methodology over the Alaskan Beaufort Sea since 1989. Sightings of Bowhead Whales in the central Alaskan Beaufort Sea in September 1997 and September 2014 were unusual in that hundreds of Whales were observed within a few kilometers of local barrier islands. We compare Bowhead Whale sightings, river discharge data, wind records, and satellite imagery to argue that the large numbers of Bowhead Whales observed nearshore in September 1997 and 2014 resulted from favorable feeding conditions established by high river discharges and prior upwelling events. These results are then generalized in a simple binary-based mechanistic framework that links the relevant physics to occurrences of observed and potential feeding opportunities for Bowhead Whales in the central Alaskan Beaufort Sea and in other locales along the Beaufort coast.
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trends in sea ice cover within Bowhead Whale habitats in the pacific arctic
Deep-sea Research Part Ii-topical Studies in Oceanography, 2018Co-Authors: Matthew L Druckenmiller, John C. George, Megan C Ferguson, Janet T Clarke, John J Citta, Lori T QuakenbushAbstract:Abstract The range of the Bering-Chukchi-Beaufort (BCB) population of Bowhead Whales (Balaena mysticetus) extends across the seasonally ice-covered waters of the Pacific Arctic region. The majority of Whales summer in the eastern Beaufort Sea and winter in the Bering Sea, migrating across the Chukchi Sea in fall and spring. As arctic sea-ice extent rapidly diminishes, the increasing length and variability of the open water season is changing Bowhead habitat substantially, with many areas now regularly ice-free when Whales are present. This study examines changes in the number of open water days (OWD) between 1979 and 2014 within annual Bowhead Whale core-use areas as defined by satellite tagging data, and within the western Beaufort Sea (140–157°W; to 72°N) sampled by fall aerial surveys. Ice cover has decreased more in the core-use areas in the northern extent of the range than in core-use areas in the southern extent. The numbers of OWD within the core-use areas near Point Barrow and along the northern Chukotka Coast during peak use have increased by 13 and 10 days/decade, respectively. The most dramatic reductions in sea-ice cover have taken place in the western Beaufort Sea where the number of OWD on the shelf and slope have increased by 20 and 25 days/decade, respectively. In contrast, sea-ice cover has not significantly changed within the winter core-use area near the Gulf of Anadyr. Using aerial survey data, we found that Bowheads in the Beaufort Sea during the fall migration have a preference for being closer to shore than to the ice edge, and that their distance to shore decreases as the fraction of open water increases. This distribution may be due to increased feeding opportunities closer to shore as a result of greater upwelling along the shelf break when the ice cover is farther from shore. Furthermore, the aerial survey data also revealed a substantial shift westward toward Point Barrow in the Whales’ use of the western Beaufort Sea during fall in the period 1997–2014 compared to 1982–1996. The extent and timing of sea-ice coverage has changed relatively little over time in the Bering Sea. Bowheads typically migrate north prior to spring ice melt and retreat; therefore, large changes in the timing of the spring migration are not expected. We anticipate that Bowheads will spend increasingly more time within summer and fall feeding areas, delaying their arrival to wintering areas in the Bering Sea. Reduced ice coverage and thickness in the southern Chukchi Sea may make wintering there more common in the future. Summer and fall movements may be more variable as productivity and zooplankton aggregations in existing feeding areas are altered in response to sea ice thinning and retreat, and as new areas become available.
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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.
Frederik Valeur Seersholm - One of the best experts on this subject based on the ideXlab platform.
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dna evidence of Bowhead Whale exploitation by greenlandic paleo inuit 4 000 years ago
Nature Communications, 2016Co-Authors: Frederik Valeur Seersholm, Mikkel Winther Pedersen, Martin Jensen Soe, Hussein Shokry, Sarah S T Mak, Anthony Ruter, Maanasa Raghavan, William W FitzhughAbstract:The demographic history of Greenland is characterized by recurrent migrations and extinctions since the first humans arrived 4,500 years ago. Our current understanding of these extinct cultures relies primarily on preserved fossils found in their archaeological deposits, which hold valuable information on past subsistence practices. However, some exploited taxa, though economically important, comprise only a small fraction of these sub-fossil assemblages. Here we reconstruct a comprehensive record of past subsistence economies in Greenland by sequencing ancient DNA from four well-described midden deposits. Our results confirm that the species found in the fossil record, like harp seal and ringed seal, were a vital part of Inuit subsistence, but also add a new dimension with evidence that caribou, walrus and Whale species played a more prominent role for the survival of Paleo-Inuit cultures than previously reported. Most notably, we report evidence of Bowhead Whale exploitation by the Saqqaq culture 4,000 years ago.
Jeff W Higdon - One of the best experts on this subject based on the ideXlab platform.
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Evidence of molting and the function of “rock-nosing” behavior in Bowhead Whales in the eastern Canadian Arctic - Fig 6
2017Co-Authors: Sarah M. E. Fortune, Jeff W Higdon, William R. Koski, Andrew W. Trites, Mark F. Baumgartner, Steven H. FergusonAbstract:Example of sloughing epidermis (A) located behind the blowholes of a Bowhead Whale (Balaena mysticetus) and mottled skin (B) found near the blowholes.
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prey assemblage isotopic variability as a tool for assessing diet and the spatial distribution of Bowhead Whale balaena mysticetus foraging in the canadian eastern arctic
Marine Ecology Progress Series, 2012Co-Authors: Corinne Pomerleau, Stephen D Petersen, Veronique Lesage, Steve Ferguson, Gesche Winkler, Jeff W HigdonAbstract:The eastern Canada-West Greenland (EC-WG) Bowhead Whale Balaena mysticetus population is slowly recovering from the intensive commercial whaling of the 18th and 20th cen- turies. However, climate change, through effects on ice conditions and prey availability, is one of several threats that might affect Bowhead Whale recovery. In this study, we exploited the variabil- ity observed in isotopic signatures of prey assemblages across the eastern Arctic to examine vari- ability in diet among Bowhead Whales (n = 202) and identify their potential foraging areas. We compared δ 13 C and δ 15 N isotope ratios of biopsied skin samples with those of potential zooplank- ton prey species collected across the Canadian eastern Arctic, and calculated the proportional contributions of various sources (zooplankton) to the diet of Bowhead Whales using a Bayesian sta- ble isotope mixing model. A cluster analysis indicated some variability in isotopic composition among groups of individuals, but not between males and females or age classes. The isotopic model discounted Davis Strait and Disko Bay as potential foraging areas for Bowhead Whales, at least in spring and summer. Lancaster Sound, Baffin Bay and the Gulf of Boothia were the 3 main areas likely used for summer feeding, where Bowhead Whales fed primarily on large Arctic calanoid copepods (Calanus hyperboreus, C. glacialis, Metridia longa, and Paraeuchaeta spp.), mysids and euphausiids. While some inter-individual variability in diet was observed, the strong dependence of this endemic Arctic species on Arctic zooplankton may make them vulnerable to the predicted latitudinal shift in prey species composition caused by ongoing warming.
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killer Whale orcinus orca predation in a multi prey system
Population Ecology, 2012Co-Authors: Jeff W Higdon, Michael C S Kingsley, Steven H. FergusonAbstract:Predation can regulate prey numbers but predator behaviour in multiple-prey systems can complicate understanding of control mechanisms. We investigate killer Whale (Orcinus orca) predation in an ocean system where multiple marine mammal prey coexist. Using stochastic models with Monte-Carlo simulations, we test the most likely outcome of predator selection and compare scenarios where killer Whales: (1) focus predation on larger prey which presumably offer more energy per effort, (2) generalize by feeding on prey as encountered during searches, or (3) follow a mixed foraging strategy based on a combination of encounter rate and prey size selection. We test alternative relationships within the Hudson Bay geographic region, where evidence suggests killer Whales seasonally concentrate feeding activities on the large-bodied Bowhead Whale (Balaena mysticetus). However, model results indicate that killer Whales do not show strong prey specialization and instead alternatively feed on narwhal (Monodon monoceros) and beluga (Delphinapterus leucas) Whales early and late in the ice-free season. Evidence does support the conjecture that during the peak of the open water season, killer Whale predation can differ regionally and feeding techniques can focus on Bowhead Whale prey. The mixed foraging strategy used by killer Whales includes seasonal predator specialization and has management and conservation significance since killer Whale predation may not be constrained by a regulatory functional response.