Article

Gray whale distribution relative to benthic invertebrate biomass and abundance: Northeastern Chukchi Sea 2009–2012

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The shallow continental shelf waters of the Bering and Chukchi seas are the northernmost foraging grounds of North Pacific gray whales (Eschrichtius robustus). Benthic amphipods are considered the primary prey of gray whales in these waters, although no comprehensive quantitative analysis has been performed to support this assumption. Gray whale relative abundance, distribution, and behavior in the northeastern Chukchi Sea (69°–72°N, 155–169°W) were documented during aerial surveys in June-October 2009–2012. Concurrently, vessel-based benthic infaunal sampling was conducted in the area in July-August 2009–10, September 2011, and August 2012. Gray whales were seen in the study area each month that surveys were conducted, with the majority of whales feeding. Statistical analyses confirm that the highest densities of feeding gray whales were associated with high benthic amphipod abundance, primarily within 70 km of shore from Point Barrow to Icy Cape, in water <50 m deep. Conversely, gray whales were not seen in 40-km×40-km cells containing benthic sampling stations with 85 m⁻² or fewer amphipods. Continuing broad-scale aerial surveys in the Chukchi Sea and prey sampling near feeding gray whales will be an important means to monitor and document ongoing and predicted ecosystem changes.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... This change in migration timing could be due to a decrease in benthic amphipod biomass in the gray whale foraging areas of the Chirikov Basin from the 1980s to 2000s causing the gray whale foraging range to expand north (Moore et al. 2003, Coyle et al. 2007). Currently, the central feeding area for the eastern North Pacific gray whales is in the Chukchi Sea along the continental shelf between Point Lay and Point Barrow, where their presence is correlated with high abundances of amphipods (Schonberg et al. 2014, Brower et al. 2017). If gray whales swim farther north to find suitable prey, they may also need to consume more calories to sustain their journey to and from the southern wintering areas. ...
... We averaged the daily sea ice concentrations over the feeding area from Dease Inlet, east of Point Barrow, to Cape Lisburne covering the area from ~20 to 120 km from shore. This area was chosen based on gray whale aerial sighting data reported by Brower et al. (2017). ...
... For example, benthic prey abundance should be quantified in the gray whale feeding area in the Arctic at the same sampling locations for the duration of the study. Benthic amphipod abundance has been measured as a function of location in the Arctic feeding areas (Brower et al. 2017) but has not been measured as a function of time on less than decadal time scales. Prey abundance and distribution is likely an important variable that would affect the gray whale population size, health, and migration timing. ...
... In this period, UAS has been applied to a range of marine megafauna, including studies on body condition of cetaceans (Christiansen et al., 2016a;Dawson et al., 2017;Burnett et al., in press) and pinnipeds (Goebel et al., 2015;Krause et al., 2017) through photogrammetry techniques; population, density and distribution estimates of pinnipeds (Goebel et al., 2015;Johnston et al., 2017), cetaceans (Hodgson et al., 2017), seabirds (Goebel et al., 2015), sirenia (Hodgson et al., 2013), and turtles (Sykora-Bodie et al., 2017); photo-identification studies of pinnipeds (Pomeroy et al., 2015) and cetaceans (Koski et al., 2015); and exhalent sample collection of cetacean blows (Acevedo-Whitehouse et al., 2010;Pirotta et al., 2017). Prior to application of UAS technology, collection of many of these data types was limited and/or reliant on costly, noisy and risky helicopter or fixed wing platforms (e.g., Perryman and Lynn, 2002;Torres et al., 2005;Brower et al., 2017). UAS has the potential to significantly reduce the human risk associated with aerial marine megafauna surveys by eliminating the need for manned flights. ...
... While most ENP gray whales are benthic suction feeders that exploit thick mats of ampeliscid amphipods in the Bering and Chukchi seas (Coyle et al., 2007;Brower et al., 2017), PCFG gray whales display flexible foraging habitats and prey items. In their northern range along the coasts of Vancouver Island (Canada) and Washington (United States), PCFG gray whales have been documented benthic feeding on amphipods and ghost shrimp (Callianassa californiensis) (Oliver et al., 1984;Weitkamp et al., 1992;Dunham and Duffus, 2001) and consuming epibenthic and pelagic mysid (Mysidae Dana, 1850), herring eggs/larvae (Clupu barengus pallasi), and crab larvae (Family Porcellanidae) (Darling et al., 1998;Dunham and Duffus, 2001;Nelson et al., 2008;Feyrer and Duffus, 2011). ...
... We documented that gray whales use multiple foraging tactics, highlighting their adaptability to prey availability and various habitats. This foraging plasticity may help explain the rapid population increase of Northeast Pacific gray whales since whaling (Alter et al., 2007), their broad spatial distribution across the northeast Pacific during their foraging season (Calambokidis et al., 2002;Moore et al., 2003;Brower et al., 2017), and their potential to respond to multiple scales of habitat change, from seismic surveys (Bröker et al., 2015) to climate change (Alter et al., 2015;Salvadeo et al., 2015). This new information can be applied to refine management plans so that mitigation of human induced threats, such as vessel strikes, noise pollution, and fisheries entanglement, is targeted and effective. ...
Presentation
From our traditional boat-based horizontal perspective, cetacean behavioral observations are typically limited to when the animal is at the surface, and health assessment is constrained to photographs captured of this limited body view. Achieving an aerial perspective has been restricted to brief helicopter or plane based observations that are costly, noisy and risky. The emergence of commercial small unmanned aerial systems (sUAS) has significantly reduced these constraints, and provide a stable, relatively quiet and inexpensive platform that enables replicate cetacean observations for prolonged periods with minimal disturbance. With the imminent proliferation of UAS cetacean studies comes the need for robust quantitative methods of video analysis. Between May and October 2016, we flew 73 sUAS flights over 189 foraging gray whales along the Oregon, USA coast. We conducted photogrammetric health assessments and behavioral analyses using >300 minutes of recorded whale footage. We analyzed video frames of whales with a customized interactive program that measures body length and width, scales pixels to metric lengths, assesses measurement error, calculates width:length ratios, and computes a unique length-normalized body area index (BAI) that facilitates body condition comparison. Results indicate individual body condition variation relative to demographics (e.g., age, lactating, pregnant), and increased girth at an individual and population level across the foraging season. Small UAS videography of whales was categorized by general behavior state (e.g., travel, rest, forage, social, unknown) and sub-class behavior events (e.g., defecation, feeding tactic, nursing) to calculate behavioral budgets. Novel behavioral observations (e.g., paired feeding, extensive upside-down swimming) were also documented. Amount of time visible at surface and underwater were tabulated to demonstrate increased observational capacity offered by sUAS. Visible whale response to the sUAS was limited to a few incidences of potential head turning for visual inspection. Our study highlights the emerging multi-purpose applications of sUAS technology to cetacean studies.
... In this period, UAS has been applied to a range of marine megafauna, including studies on body condition of cetaceans (Christiansen et al., 2016a;Dawson et al., 2017;Burnett et al., in press) and pinnipeds (Goebel et al., 2015;Krause et al., 2017) through photogrammetry techniques; population, density and distribution estimates of pinnipeds (Goebel et al., 2015;Johnston et al., 2017), cetaceans (Hodgson et al., 2017), seabirds (Goebel et al., 2015), sirenia (Hodgson et al., 2013), and turtles (Sykora-Bodie et al., 2017); photo-identification studies of pinnipeds (Pomeroy et al., 2015) and cetaceans (Koski et al., 2015); and exhalent sample collection of cetacean blows (Acevedo-Whitehouse et al., 2010;Pirotta et al., 2017). Prior to application of UAS technology, collection of many of these data types was limited and/or reliant on costly, noisy and risky helicopter or fixed wing platforms (e.g., Perryman and Lynn, 2002;Torres et al., 2005;Brower et al., 2017). UAS has the potential to significantly reduce the human risk associated with aerial marine megafauna surveys by eliminating the need for manned flights. ...
... While most ENP gray whales are benthic suction feeders that exploit thick mats of ampeliscid amphipods in the Bering and Chukchi seas (Coyle et al., 2007;Brower et al., 2017), PCFG gray whales display flexible foraging habitats and prey items. In their northern range along the coasts of Vancouver Island (Canada) and Washington (United States), PCFG gray whales have been documented benthic feeding on amphipods and ghost shrimp (Callianassa californiensis) (Oliver et al., 1984;Weitkamp et al., 1992;Dunham and Duffus, 2001) and consuming epibenthic and pelagic mysid (Mysidae Dana, 1850), herring eggs/larvae (Clupu barengus pallasi), and crab larvae (Family Porcellanidae) (Darling et al., 1998;Dunham and Duffus, 2001;Nelson et al., 2008;Feyrer and Duffus, 2011). ...
... We documented that gray whales use multiple foraging tactics, highlighting their adaptability to prey availability and various habitats. This foraging plasticity may help explain the rapid population increase of Northeast Pacific gray whales since whaling (Alter et al., 2007), their broad spatial distribution across the northeast Pacific during their foraging season (Calambokidis et al., 2002;Moore et al., 2003;Brower et al., 2017), and their potential to respond to multiple scales of habitat change, from seismic surveys (Bröker et al., 2015) to climate change (Alter et al., 2015;Salvadeo et al., 2015). This new information can be applied to refine management plans so that mitigation of human induced threats, such as vessel strikes, noise pollution, and fisheries entanglement, is targeted and effective. ...
Article
Full-text available
During traditional boat-based surveys of marine megafauna, behavioral observations are typically limited to records of animal surfacings obtained from a horizontal perspective. Achieving an aerial perspective has been restricted to brief helicopter or airplane based observations that are costly, noisy, and risky. The emergence of commercial small unmanned aerial systems (UAS) has significantly reduced these constraints to provide a stable, relatively quiet, and inexpensive platform that enables replicate observations for prolonged periods with minimal disturbance. The potential of UAS for behavioral observation appears immense, yet quantitative proof of utility as an observational tool is required. We use UAS footage of gray whales foraging in the coastal waters of Oregon, United States to develop video behavior analysis methods, determine the change in observation time enabled by UAS, and describe unique behaviors observed via UAS. Boat-based behavioral observations from 53 gray whale sightings between May and October 2016 were compared to behavioral data extracted from video analysis of UAS flights during those sightings. We used a DJI Phantom 3 Pro or 4 Advanced, recorded video from an altitude ≥25 m, and detected no behavioral response by whales to the UAS. Two experienced whale ethologists conducted UAS video behavioral analysis, including tabulation of whale behavior states and events, and whale surface time and whale visible time (total time the whale was visible including underwater). UAS provided three times more observational capacity than boat-based observations alone (300 vs. 103 min). When observation time is accounted for, UAS data provided more and longer observations of all primary behavior states (travel, forage, social, and rest) relative to boat-based data, especially foraging. Furthermore, UAS enable documentation of multiple novel gray whale foraging tactics (e.g., headstands: n = 58; side-swimming: n = 17; jaw snapping and flexing: n = 10) and 33 social events (nursing and pair coordinated surfacings) not identified from boat-based observation. This study demonstrates the significant added value of UAS to marine megafauna behavior and ecological studies. With technological advances, robust study designs, and effective analytical tools, we foresee increased UAS applications to marine megafauna studies to elucidate foraging strategies, habitat associations, social patterns, and response to human disturbance.
... Ampeliscid amphipods in the eastern Russian and western North American Arctic are a key resource for Pacific gray whales (Eschrichtius robustus), which travel from as far as Baja California, Mexico to the Bering and Chukchi Seas to forage there during the summer ice-free season Fadeev 2011;Budnikova and Blokhin 2012;Heide-Jørgensen et al. 2012;Schonberg et al. 2014;Demchenko et al. 2016;Brower et al. 2017). Ampeliscids are one of the most abundant prey species, because they form dense beds of self-made tubes, with a biomass up to 300 g wet wt m −2 (Heide- Jørgensen et al. 2012). ...
... The ampeliscid tubes also provide attachment sites to elevate into the water column. Various tube-living amphipods associate with ampeliscid beds in this way (Wildish 1984;Rigolet et al. 2011Rigolet et al. , 2012Myers et al. 2012;Mironov 2013;Brower et al. 2017). ...
... In the Chukchi Sea, gray whales target areas where amphipod densities are > 85 m −2 (Brower et al. 2017). Most parts of the CBS meet this density criterion for ampeliscids alone (Fig. 1). ...
Article
Full-text available
The first known ampeliscid (Amphipoda: Ampeliscidae) bed for the Canadian Arctic was reported in 2013 from the Canadian Beaufort Shelf (CBS), but species patterns were not examined. This study examines their distributions relative to differences in life strategies and environmental variables. The intent is to build a better understanding of this highly productive system in comparison with ampeliscid beds in the neighboring Bering and Chukchi Seas which are important resources for higher trophic level consumers. Data from 412 samples collected to 1000 m depth over 2002–2009 indicate that there are at least eight ampeliscid species on the CBS. Five occur elsewhere in polar and temperate latitudes and three may be new to science or are species complexes. All are limited to bottom temperatures < 0.41 °C. Congeners do not distribute coherently (Similarity Profiles analysis, p < 0.05). Resource-demanding Ampelisca macrocephala (max. 8467 ind. m⁻²) dominates Byblis spp. and Haploops laevis on the shelf enriched by wind-driven upwelling but dominance switches with depth to Haploops tubicola, Haploops sibirica and Haploops sp. Obligate suspension feeding with adaptations for fine particle capture enables deep living while abundance dominants supplement their diets with deposit feeding and predation. The ampeliscids may facilitate other amphipods by providing attachment sites on their tubes. Polychaetes may facilitate the ampeliscids by bringing buried resources to the surface. Given that the CBS is undergoing substantial environmental change, we recommend the CBS ampeliscids for monitoring its environmental regime to complement ongoing monitoring in other polar and temperate ampeliscid beds.
... With shifting climate and increasing human impacts, long-term conservation planning requires delineating and projecting changes in habitats and the food webs they support (Brigham, 2011;Carroll, Dunk, & Moilanens, 2010;Gormley, Porter, Bell, Hull, & Sanderson, 2013;Hole et al., 2011). In the shallow seas of the Amerasian Arctic, much of the food-web biomass is benthic, and a number of endothermic top predators [sea ducks, bearded seals (Erignathus barbatus Erxleben), walruses (Odobenus rosmarus Linnaeus), and gray whales (Eschrichtius robustus Lilljeborg)] feed mainly or entirely on benthic fish or invertebrates (Brower, Ferguson, Schonberg, Jewett, & Clarke, 2017;Crawford, Quakenbush, & Citta, 2015;Lovvorn et al., 2014;Sheffield & Grebmeier, 2009). Developing cost-effective ways to monitor and predict changes in the dispersion of different prey assemblages is key to conserving adequate habitats for these predators into the future (Pace, Carpenter, & Cole, 2015;Reiss et al., 2015;Weinert et al., 2016). ...
... Nevertheless, the presence of smaller (younger) bivalves near the sediment surface may indicate larger individuals buried deeper, and in the past, side-scan sonar detected extensive areas of walrus feeding furrows in what appear to have been type-3 habitats in the Chirikov Basin (Nelson & Johnson, 1987). Gray whales in this region feed mainly on amphipods (Brower et al., 2017;Oliver & Slattery, 1985). The amphipod biomass was greatest in assemblage type 3, corresponding to the traditionally heavy use of the Chirikov Basin by gray whales (Moore, Grebmeier, & Davies, 2003;Nelson & Johnson, 1987). ...
Article
Full-text available
• In marine spatial planning, conserving adequate habitats and the food webs they support requires delineating habitats and projecting future trends. For bottom‐feeding marine birds and mammals, repeated benthic sampling over large areas to document changes and to develop predictive models of prey dispersion is quite costly. More easily monitored variables that relate strongly to the biomass and structure of benthic assemblages, and are more readily predicted from physical models of climate change, would facilitate planning efforts. • The organic carbon (OC) content of sediments integrates diverse physical and biotic processes, and can be less variable over time than primary production, salinity, temperature, or position of water masses. Sediment OC further subsumes inputs at the base of food webs that can limit carbon flows to higher taxa. • For the northern Bering Sea, this study explored the utility of sediment OC as a predictor of benthic assemblage types. Cluster analysis and multi‐dimensional scaling distinguished three main types along a gradient of sediment OC. • The assemblage for highest sediment OC had a much greater biomass of brittlestars, diverse marine worms, and two mid‐sized, thinner‐shelled bivalves selected as prey by diving sea ducks. The assemblage for lowest sediment OC lacked brittlestars, had a much greater biomass of amphipods sought by gray whales (Eschrichtius robustus), and had a much higher biomass of two often larger or thicker‐shelled bivalves commonly targeted by walruses (Odobenus rosmarus). Areas of exceptionally low sediment OC tended towards dominance by sand dollars with low foraging value. • Our study shows that sediment OC has promise as a proxy for monitoring and predicting changes in important prey assemblages in a given region. Models that link predicted hydrographic patterns to lateral advection of phytodetritus, and the resulting sediment OC, may further allow the use of physical climate models to project the future dispersion of benthic habitats for endothermic predators.
... However, within those general areas are more localized patches of preferred prey types with high enough density to support profitable foraging. These subareas typically occupy only a fraction of the total area, and in some years can be quite restricted in size or in accessibility to air-breathing endotherms relative to ice cover (Nelson & Johnson 1987, Lovvorn et al. 2009, Brower et al. 2017. Ensuring that such suitable patches are available in all years requires consideration of food web types at smaller scales (Blanchard & Feder 2014). ...
... In the northern Bering Sea, different food web types associated with different ranges of sediment OC are more favorable to certain bottom-feeding predators owing to differing composition of major prey. For example, spectacled eiders Somateria fischeri prefer thinshelled, deposit-feeding bivalves that are shallowly buried in muddy, highly organic sediments (Lovvorn et al. 2009; walruses Odobenus rosmarus often feed on thicker-shelled, facultative or filter-feeding bivalves buried deeper in less organic sediments (Oliver et al. 1983, Born et al. 2003, Sheffield & Grebmeier 2009); and gray whales Eschrichtius robustus typically focus on filter-feeding crustaceans in sandier sediments with lower OC (Oliver & Slattery 1985, Brower et al. 2017. These prey items are interdependent components of diverse assemblages which form recognizable food web types in different areas of the northern Bering Sea (Lovvorn et al. 2015a(Lovvorn et al. , 2016. ...
... Improved documentation of in-flight observation protocols began in 2006, with a primary observer stationed at port and starboard bubble windows, and a dedicated data recorder that served as a secondary observer . A few recent studies have analysed data from surveys after 2008, when survey protocols were more homogeneous (Brower, Ferguson, Schonberg, Jewett, & Clarke, 2017;Clarke, Ferguson, Willoughby, & Brower, 2018). However, because our study included survey data from 1988-2012, a period of time when data were collected with different aerial survey platforms and without comprehensive documentation of observer configurations and data collection protocols, we treated the entire dataset as a presence-absence dataset. ...
Conference Paper
Full-text available
Background/Question/Methods The effects of climate change are projected to be disproportionately pronounced in polar regions, where changes in the concentration and extent of sea ice will affect the spatio-temporal dynamics of the marine planktonic ecosystem. The endangered bowhead whale (Balaena mysticetus) is one of the largest animals in the Arctic, yet they feed on some of the smallest arctic animals, zooplankton. Changes in the abundance and distribution of zooplankton due to changes in sea ice would have direct effects on bowhead whales. The objective of our research is to improve understanding of how the arctic planktonic ecosystem and sea ice affects the regional distribution of bowhead whales in the Beaufort and Chukchi seas, and to develop hindcasts and long-term forecasts of bowhead whale distribution under different arctic climate change scenarios. Our approach combines a multi-decadal bowhead whale survey dataset with modeled environmental data from the pan-Arctic Biology/Ice/Ocean Modeling and Assimilation System (BIOMAS) – a fully coupled 3D model with an 11-component lower-trophic model that includes three zooplankton groups (microzooplankton, copepods, and predatory zooplankton). Results/Conclusions We used 23 years of aerial survey data and BIOMAS model output to train monthly bowhead whale species distribution models for the Beaufort Sea. Mean model performance as measured by AUC was 0.82. The most influential co-variate was bathymetry (30%). Zooplankton prey groups were the most influential modeled environmental co-variates: predatory zooplankton (15%), microzooplankton (13%) and copepods (12%). Sea ice, diatoms and silicates had little influence on modeled distributions. Understanding the link between secondary productivity and loss of sea ice is a necessary step to assessing the impact of increased human activities in the Arctic, such as seismic exploration, offshore drilling and commercial vessel traffic. In the next phase of our work BIOMAS will be used to project the future responses of Beaufort and Chukchi seas' marine production cycles and food web dynamics in correlation with the continued decline in sea ice cover under the IPCC global climate model. BIOMAS predictions will then be used to drive species distribution models for bowhead whales. This type of scenario study will help us understand the potential changes in bowhead whale habitat and help evaluate strategies for minimizing human-whale interactions as sea ice extent and whale populations change in the coming decades.
... As noted by Schonberg et al. (2014), gray whales, which feed on benthic-dwelling amphipods, appear concentrated over an area between Icy Cape/Wainwright and Point Barrow, a region known to have great concentrations and persistence of amphipods since the 1970s. Through the use of combined data sets from COMIDA CAB, Hanna Shoal, and the Alaska Monitoring and Assessment Program (AKMAP), Brower et al. (2017) conducted a comprehensive quantitative analysis to test this relationship. Their statistical analyses confirmed that the highest densities of feeding gray whales were associated with high benthic amphipod abundance, and that gray whale behavior represents an important proxy for Arctic change. ...
... A well-known gray whale foraging area is located along the Alaska coast, between Icy Cape and Utqiaġvik (formerly Barrow), where benthic amphipods are abundant (e.g. Moore et al., 2000;Brower et al., 2017). The region near Utqiaġvik is also known to have Fig. 13. ...
Article
We collated available satellite telemetry data for six species of ice-associated marine mammals in the Pacific Arctic: ringed seals (Pusa hispida; n=118), bearded seals (Erignathus barbatus, n=51), spotted seals (Phoca largha, n=72), Pacific walruses (Odobenus rosmarus divergens, n=389); bowhead whales (Balaena mysticetus, n=46), and five Arctic and sub-arctic stocks of beluga whales (Delphinapterus leucas, n=103). We also included one seasonal resident, eastern North Pacific gray whales (Eschrichtius robustus, n=12). This review summarized the distribution of daily locations from satellite-linked transmitters during two analysis periods, summer (May–November) and winter (December–April), and then examined the overlap among species. Six multi-species core use areas were identified during the summer period: 1) Chukotka/Bering Strait; 2) Norton Sound; 3) Kotzebue Sound; 4) the northeastern Chukchi Sea; 5) Mackenzie River Delta/Amundsen Gulf; and 6) Viscount Melville Sound. During the winter period, we identified four multi-species core use areas: 1) Anadyr Gulf/Strait; 2) central Bering Sea; 3) Nunivak Island; and 4) Bristol Bay. During the summer period, four of the six areas were centered on the greater Bering Strait region and the northwestern coast of Alaska and included most of the species we examined. The two remaining summer areas were in the western Canadian Arctic and were largely defined by the seasonal presence of Bering-Chukchi-Beaufort stock bowhead whales and Eastern Beaufort Sea stock beluga whales, whose distribution overlapped during both summer and winter periods. During the winter period, the main multi-species core use area was located near the Gulf of Anadyr and extended northwards through Anadyr and Bering Straits. This area is contained within the Bering Sea “green belt”, an area of enhanced primary and secondary productivity in the Bering Sea. We also described available telemetry data and where they can be found as of 2017. These data are important for understanding ice-associated marine mammal movements and habitat use in the Pacific Arctic and should be archived, with appropriate metadata, to ensure they are available for future retrospective analyses.
... We anticipated that this emphasis would enhance our chances of receiving FAA permission for beyond visual line-of-sight flights needed for the project. Second, large cetaceans, particularly gray whales and bowhead whales, are reliably found in high densities in portions of this area during the open water (ice-free) season (Clarke et al. 2014;Citta et al. 2015;Brower et al. 2017). Further, modeling efforts using existing gray whale data collected during previous aerial surveys indicated that the project should be able to achieve a coefficient of variation of 0.3 in estimated gray whale density in this area with approximately 50 h of UAS flight time. ...
Article
Full-text available
Manned aerial surveys are routinely used to assess cetacean distribution and density, often over large geographic areas. Unmanned aircraft systems (UAS) have been identified as a technology that could augment or replace manned aerial surveys for cetaceans. To understand what research questions involving cetacean distribution and density can be addressed using manned and UAS technology in the Arctic, we conducted paired aerial surveys for cetaceans near Utqiaġvik (Barrow), Alaska. We present the methods and operational results from the project, and challenges encountered during the field work. Fall arctic weather varied dramatically over small spatiotemporal scales and harsh environmental conditions increased the maintenance required for repeated UAS operations. Various technologies, such as temperature and humidity sensors, a software system that provided near-term forecasts of highly variable weather, and a surface-based air traffic radar feed, directly contributed to the ability to conduct routine, successful, beyond line-of-sight UAS flights under these situations. We provide recommendations for future projects to help streamline project planning and enhance researchers’ ability to use UAS to collect data needed for ecological research.
... The survey area provides important feeding grounds and migration pathways for gray whales, bowhead whales, and belugas, which use the area seasonally (e.g., Citta et al. 2015;Clarke et al. , 2018Stafford et al. 2016;Brower et al. 2017b). Gray whales are reliably found in high densities in the west sector during the open water (ice-free) season, which occurs from July to October. ...
Article
Full-text available
Manned aerial surveys have been used successfully for decades to collect data to infer cetacean distribution, density (number of whales/km2), and abundance. Unmanned aircraft systems (UAS) have potential to augment or replace some manned aerial surveys for cetaceans. We conducted a three-way comparison among visual observations made by marine mammal observers aboard a Turbo Commander aircraft; imagery autonomously collected by a Nikon D810 camera system mounted to a belly port on the Turbo Commander; and imagery collected by a similar camera system on a remotely controlled ScanEagle® UAS operated by the US Navy. Bowhead whale density estimates derived from the marine mammal observer data were higher than those from the Turbo Commander imagery; comparisons to the UAS imagery depended on survey sector and analytical method. Beluga density estimates derived from either dataset collected aboard the Turbo Commander were higher than estimates derived from the UAS imagery. Uncertainties in density estimates derived from the marine mammal observer data were lower than estimates derived from either imagery dataset due to the small sample sizes in the imagery. The visual line-transect aerial survey conducted by marine mammal observers aboard the Turbo Commander was 68.5% of the cost of the photo strip-transect survey aboard the same aircraft and 9.4% of the cost of the UAS survey.
... Their range extends from the Bering Sea through the Chukchi and into the western Beaufort, with occasional sightings as far east as the Canadian Beaufort Sea. Gray whales select shallow coastal and shoal habitats throughout this area, where they feed primarily on benthic infaunal amphipods, but they also take epifauna and pelagic prey when available ( Brower et al., 2017;Moore et al., 2000). Aerial surveys and satellite telemetry studies indicate gray whales remain in localized areas while feeding, with slow movements and strong site fidelity described for foraging on amphipods in nearshore waters of the Chukotka peninsula (Heide-Jørgensen et al., 2012b). ...
Article
Biophysical changes in marine ecosystems of the Arctic and subarctic sectors of the Atlantic and Pacific are now evident, driven primarily by sea ice loss, ocean warming and increases in primary productivity. As upper trophic species, baleen whales can serve as sentinels of ecosystem reorganization in response to these biophysical alterations, via changes in their ecology and physiological condition. This paper is the first to review baleen whale ecology in high-latitude marine ecosystems of both the north Atlantic and north Pacific. Oceanographically, these sectors offer four contrasting habitats to baleen whales: (i) a broad-deep-strait and deep-shelf inflow system in the Northeast Atlantic (NEA), (ii) a combination of inflow and outflow systems north of Iceland in the central North Atlantic (CNA), (iii) an outflow shelf and basin in the Northwest Atlantic (NWA), and (iv) a narrow-shallow-strait inflow shelf system in the Pacific sector. Information on baleen whale ecology from visual and passive acoustic surveys, combined with available telemetry and diet studies, show contrasting patterns of baleen whale occurrence among sectors. In brief, arctic and subarctic waters in the Atlantic sector support a far greater number of seasonally-migrant baleen whales than the Pacific sector. Thousands of humpback, fin and common minke whales occupy the diverse habitats of the Atlantic sector. These species all exhibit flexible diets, focused primarily on euphausiids (krill) and forage fishes (e.g., capelin, herring, sand lance), which are now responding to ecosystems altered by climate change. Conversely, the Pacific sector supports a far greater number of arctic-endemic bowhead whales than the Atlantic sector, as well as a large population of seasonally-migrant gray whales. Currently, differences in migratory timing and, to a lesser extent, foraging behaviors, serves to restrict prey competition between the arctic-endemic bowhead whale and seasonally migrant baleen whale species in both sectors. Regional aspects of changes in prey type and availability will likely impact future migratory timing, habitat selection, body condition and diet of baleen whales. Tracking variability in these attributes can provide valuable input to ecosystem models and thereby contribute the sentinel capability of baleen whales to forecasts of future states of high latitude marine ecosystems.
... Improved documentation of in-flight observation protocols began in 2006, with a primary observer stationed at port and starboard bubble windows, and a dedicated data recorder that served as a secondary observer . A few recent studies have analysed data from surveys after 2008, when survey protocols were more homogeneous (Brower, Ferguson, Schonberg, Jewett, & Clarke, 2017;Clarke, Ferguson, Willoughby, & Brower, 2018). However, because our study included survey data from 1988-2012, a period of time when data were collected with different aerial survey platforms and without comprehensive documentation of observer configurations and data collection protocols, we treated the entire dataset as a presence-absence dataset. ...
Article
Full-text available
Aim Species distribution models (SDMs) are a widely used tool to estimate and map habitat suitability for wildlife populations. Most studies that model marine mammal density or distributions use oceanographic proxies for marine mammal prey. However, proxies could be a problem for forecasting because the relationships between the proxies and prey may change in a changing climate. We examined the use of model‐derived prey estimates in SDMs using an iconic species, the western Arctic bowhead whale (Balaena mysticetus). Location Western Beaufort Sea, Alaska, USA. Methods We used Biology Ice Ocean Modeling and Assimilation System (BIOMAS) to simulate ocean conditions important to western Arctic bowhead whales, including important prey species. Using both static and dynamic predictors, we applied Maxent and boosted regression tree (BRT) SDMs to predict bowhead whale habitat suitability on an 8‐day timescale. We compared results from models that used bathymetry with those that used only BIOMAS simulated variables. Results The best model included bathymetry and BIOMAS variables. Inclusion of dynamic variables in SDMs produced predictions that reflected temporal dynamics evident from the survey data. Bathymetry was the most influential variable in models that included that variable. Zooplankton was the most important variable for models that did not include bathymetry. Models with bathymetry performed slightly better than models with only BIOMAS derived variables. Main conclusions Bathymetry and modelled zooplankton were the most important predictor variables in bowhead whale distribution models. Our predictions reflected within‐year variability in bowhead whale habitat suitability. Using modelled prey availability, rather than oceanographic proxies, could be important for forecasting species distributions. Predictor variables used in our study were derived from a biophysical ocean model with demonstrated ability to project future ocean conditions. A natural next step is to use output from our biophysical ocean model to understand the effects of Arctic climate change.
... This reduction in benthic prey populations has occurred simultaneously to increased pelagic fish populations, a reduction of sea ice, and increased air and ocean temperatures, and it is believed that a major ecosystem shift from arctic to subarctic conditions is occurring in the northern Bering Sea (Grebmeier et al., 2006). Coincident with this decline in primary prey and ecosystem change, the foraging habitat of ENP gray whales has shifted further north into the Chukchi Sea to an area where water depths range from 40 to 60 m (Moore et al., 2003;Bluhm et al., 2007;Brower et al., 2017Brower et al., , 2018, which is markedly deeper than where gray whale foraging was previously concentrated in the shelf waters of the northern Bering Sea (20-40 m; Coachman et al., 1975). The increased depth range means that benthically feeding ENP gray whales must dive deeper than previously, which may increase the energetic cost of foraging. ...
Article
Full-text available
Predators must consume enough prey to support costly events, such as reproduction. Meeting high energetic requirements is particularly challenging for migrating baleen whales as their feeding seasons are typically restricted to a limited temporal window and marine prey are notoriously patchy. We assessed the energetic value of the six most common nearshore zooplankton species collected within the Oregon, United States range of the Pacific Coast Feeding Group (PCFG) gray whale (Eschrichtius robustus) feeding grounds, and compared these results to the energetic value of the predominant amphipod species fed on by Eastern North Pacific (ENP) gray whales in the Arctic. Energetic values of Oregon zooplankton differed significantly between species (Kruskal–Wallis χ2 = 123.38, df = 5, p < 0.0001), with Dungeness crab (Cancer magister) megalopae displaying the highest mean caloric content of all tested species (4.21 ± 1.27 kJ g– 1). This value, as well as the mean energetic value of the mysid Neomysis rayii (2.42 ± 1.06 kJ g– 1), are higher than the mean caloric content of Ampelisca macrocephala, the predominant Arctic amphipod. Extrapolations of these results to daily energetic requirements of gray whales indicate that lactating and pregnant gray whales feeding in the PCFG range would require between 0.7–1.03 and 0.22–0.33 metric tons of prey less per day if they fed on Dungeness crab megalopae or N. rayii, respectively, than a whale feeding on A. macrocephala in the Arctic. Yet, these results do not account for differences in availability of these prey species to foraging gray whales. We therefore suggest that other factors, such as prey density, energetic costs of feeding, or natal philopatry and foraging site fidelity play a role in the differences in population sizes between the PCFG and ENP gray whales. Climate change is implicated in causing reduced body condition and increased mortality of both PCFG and ENP gray whales due to decreased prey availability and abundance. Therefore, improved understanding of prey dynamics in response to environmental variability in both regions is critical.
... See Appendix S1: Fig. S15 for results using all 100 replicates for each whale length. Brower et al. 2017, Blanchard et al. 2019. While we characterized the prey landscape using data from a single year, a trend of higher prey biomass in the offshore cells has been consistently observed for at least the past 15 yr (Blanchard et al. 2019). ...
Article
Acoustic disturbance is a growing conservation concern for wildlife populations because it can elicit physiological and behavioral responses that can have cascading impacts on population dynamics. State‐dependent behavioral and life history models implemented via Stochastic Dynamic Programming (SDP) provide a natural framework for quantifying biologically meaningful population changes resulting from disturbance by linking environment, physiology, and metrics of fitness. We developed an SDP model using the endangered western gray whale (Eschrichtius robustus) as a case study because they experience acoustic disturbance on their summer foraging grounds. We modeled the behavior and physiological dynamics of pregnant females as they arrived on the feeding grounds and predicted the probability of female and offspring survival, with and without acoustic disturbance and in the presence/absence of high prey availability. Upon arrival in mid‐May, pregnant females initially exhibited relatively random behavior before they transitioned to intensive feeding that resulted in continual fat mass gain until departure. This shift in behavior co‐occurred with a change in spatial distribution; early in the season, whales were more equally distributed among foraging areas with moderate to high energy availability, whereas by mid‐July whales transitioned to predominate use of the location that had the highest energy availability. Exclusion from energy‐rich offshore areas led to reproductive failure and in extreme cases, mortality of adult females that had lasting impacts on population dynamics. Simulated disturbances in nearshore foraging areas had little to no impact on female survival or reproductive success at the population level. At the individual level, the impact of disturbance was unequally distributed across females of different lengths, both with respect to the number of times an individual was disturbed and the impact of disturbance on vital rates. Our results highlight the susceptibility of large capital breeders to reductions in prey availability, and indicate that who, where, and when individuals are disturbed are likely to be important considerations when assessing the impacts of acoustic activities. This model provides a framework to inform planned acoustic disturbances and assess the effectiveness of mitigation strategies for large capital breeders.
... Additionally, Arctic marine mammals are at greater risk as the climate warms as a result of increased exposure to, or toxicity of, contaminants (Sonne et al. 2017) and increasing disease risks (VanWormer et al. 2019). Yupik and Inupiaq subsistence hunters report changes in the distribution of a wide variety of marine mammals with declines in sea ice in recent decades and although marine mammal populations are thought to be healthy in their region, access is an increasing challenge because sea ice is less safe for travel, particularly for more southerly communities, making hunting more dangerous or impossible especially in spring (Huntington et al. 2017).. Northward expansions of summer ranges of a variety of temperate whales that feed in the Arctic have been documented on both the Pacific and Atlantic sides of the Arctic in recent years (e.g., Brower et al. 2017, Stafford et al. 2018a, Storrie et al. 2018; longer seasonal presence of these traditional summer visitors is likely to negatively impact available resources for Arctic species. A recent global assessment identified polar coastal waters as one of three geographic hotspots for levels of cumulative risk to marine mammals; Arctic marine mammals fell in the highest risk category when species diversity was incorporated into the spatial analyses (Avila et al. 2018). ...
Technical Report
Full-text available
This document provides an update on the status of marine mammals in the circumpolar Arctic from 2015– 2020
... Some gray whale carcasses documented from 2009 to 2019 may have been transported by northward moving currents from other locations within or outside of the study area. However, carcasses overwhelmingly overlap with gray whale occurrence in the eastern Chukchi Sea (Clarke et al. 2016;Brower et al. 2017). An investigation into the drift direction and distance of three floating bowhead whale carcasses in the eastern Chukchi Sea was best explained by the prevailing wind direction and mean current circulation (S. ...
Article
Full-text available
Examining Eastern North Pacific gray whale (Eschrichtius robustus) carcasses and tracking mortality and morbidity are essential for assessing the health of this stock. In the eastern Chukchi Sea, the expansive coastline relative to few coastal communities makes monitoring for and physical examination of gray whale carcasses difficult. The Aerial Surveys of Arctic Marine Mammals (ASAMM) project offers an unparalleled dataset of gray whale carcasses, documented and photographed from July to October 2009–2019, providing a unique opportunity to investigate imaged gray whale carcasses for possible cause of death. Surveys covered expanses of gray whale and killer whale (Orcinus orca) summer and autumn habitat. ASAMM documented a total of 59 gray whale carcasses, distributed across the eastern Chukchi Sea (67.5° N–72.0° N, 155.5° W–169.0° W). Carcass sighting rates ([CPUE] carcasses per 1000-km of effort) varied by month and year. The highest numbers of carcasses were observed in 2012 (13) and 2019 (8). August had the highest number of gray whale carcass sightings (22) and the highest carcass sighting rate (0.231 CPUE). Images were obtained for 56 gray whale carcasses. The majority (41) of imaged gray whale carcasses had injuries consistent with probable killer whale predation, and were photo-documented every year except 2010 (when no carcasses were seen) and 2011. Eight carcasses were suspect killer whale predation, and cause of death could not be determined for seven carcasses. These results will be valuable for evaluating mortality, concurrent with rapid oceanographic changes, and increases in anthropogenic activities.
Article
Full-text available
Climate change is a global phenomenon, yet impacts on resource availability to predators may be spatially and temporally diverse and asynchronous. As capital breeders, whales are dependent on dense, predictable prey resources during foraging seasons. An Unusual Mortality Event (UME) of Eastern North Pacific (ENP) gray whales (Eschrichtius robustus) was declared in 2019 due to a dramatic rise in stranded animals, many emaciated. Climate change impacts may have affected prey availability on the primary foraging grounds of ENP gray whales (~20,000 individuals) in the Arctic and sub-Arctic region and in coastal habitats between northern California, USA and British Columbia, Canada where a small sub-group of ENP whales called the Pacific Coast Feeding Group (PCFG; ~230 individuals) forages. To investigate variability of gray whale body condition relative to changing ocean conditions, we compare two datasets of gray whale aerial photogrammetry images collected via Unoccupied Aircraft Systems (UAS) on the ENP wintering grounds in San Ignacio Lagoon, Mexico (SIL; n=111) and on the PCFG feeding grounds in Oregon, USA (n=72) over the same three-year period (2017–2019). We document concurrent body condition improvement of PCFG whales in Oregon while body condition of whales in SIL declined. This result indicates that the UME may have affected ENP whales due to reduced energetic gain on some Arctic/sub-Arctic foraging grounds, while PCFG whales are recovering from poor prey conditions during the NE Pacific marine heatwave event of 2014–2016. Surprisingly, we found that PCFG whales in Oregon had significantly worse body condition than whales in SIL, even when accounting for year and phenology. We derive support for this unexpected finding via photogrammetry analysis of opportunistic aerial images of gray whales on Arctic foraging grounds (n=18) compared to PCFG whales in Oregon (n=30): the body condition of PCFG whales was significantly lower (t=2.96, p=0.005), which may cause PCFG whales to have reduced reproductive capacity or resilience to environmental perturbations compared to ENP whales. Overall, our study elucidates divergent gray whale body condition across sub-groups and time, and we demonstrate the value of UAS to effectively monitor and identify the physiological response of whales to climate change.
Article
This paper describes the relationship between eastern North Pacific gray whale calf production and environmental conditions in the Pacific Arctic where they feed. The results show how interannual variation in sea ice cover in the Bering and Chukchi Seas along with broader indices of North Pacific climate, such as Pacific Decadal Oscillation (PDO) and North Pacific Index (NPI), are linked to variation in gray whale reproductive output. Estimates of gray whale calf production were derived from 23 consecutive years (1994–2016) of shore‐based visual surveys conducted off California during the northward migration. PDO and NPI in combination with ice cover in the Bering and Chukchi Seas during the early phase of gestation appear to be important in explaining the observed variability in calf production. Of the 2,285 time series linear models evaluated, the model of best‐fit included PDO(July), Ice(June), NPI(February), and explained 60% of the observed variability in calf production. After elimination of two data outliers in calf production estimates (2013 and 2014) a model including Ice(May), PDO(May), and NPI(July) explained 90% of the variability. We conclude that access to prey early in the gestation period is critical to reproductive success in this population and may be important for other capital breeding mammals.
Chapter
Climate change is the key driver reshaping the physical and geopolitical landscape of the Arctic. As we now know, the Arctic is warming three times the global average, Arctic sea ice extent and thickness continues to decrease drastically, the consequence of thawing permafrost impacts Indigenous communities and threatens critical infrastructure, and fires in the Arctic are more frequent and intense. Any framework that explores the key drivers of change in the Arctic must start with climate change; it is real, rapid, and relentless. Dr. Brendan Kelly and Ms. Elizabeth Francis take us on a climate tour de force, exploring the composition of and changes to our global climate system, the human impacts on this system, and as a result, the very real and accelerated changes occurring today throughout the Arctic.
Article
Full-text available
Changes in gray whale (Eschrichtius robustus) phenology and distribution are related to observed and hypothesized prey availability, bottom water temperature, salinity, sea ice persistence, integrated water column and sediment chlorophyll a, and patterns of wind-driven biophysical forcing in the northern Bering and eastern Chukchi seas. This portion of the Pacific Arctic includes four Distributed Biological Observatory (DBO) sampling regions. In the Bering Strait area, passive acoustic data showed marked declines in gray whale calling activity coincident with unprecedented wintertime sea ice loss there in 2017-2019, although some whales were seen there during DBO cruises in those years. In the northern Bering Sea, sightings during DBO cruises show changes in gray whale distribution coincident with a shrinking field of infaunal amphipods, with a significant decrease in prey abundance (r = -0.314, p
Article
With global climate change and increasing ocean-based human activities, large whales face novel challenges in the Arctic seas. Understanding and assessing large whale occurrence and the links between occurrence and environmental variables in this region is a key issue in current management and conservation strategies for Arctic marine mammal species. During the Chukchi Sea Environmental Studies Program, large whale occurrence data were collected from vessel surveys during >56,909 km of observation effort in summer and autumn, 2008 to 2014, in the northeastern Chukchi, southern Beaufort, and Bering Seas. The most-recorded species were the Bowhead (Balaena mysticetus) and Gray (Eschrichtius robustus) Whales. Subarctic species recorded included the Humpback Whale (Megaptera novaeangliae), Fin Whale (Balaenoptera physalus), and Minke Whale (Balaenoptera acutorostrata). Sightings data were analyzed with respect to environmental variables: sea-surface temperature (SST), depth (m), and distance from shore (km), by month and year. Investigating occurrence associations with environmental parameters is a key element for predicting large whale trends in these Arctic seas and for understanding marine mammals as sentinels of oceanic shifts.
Article
Full-text available
Arctic animals face dramatic habitat alteration due to ongoing climate change. Understanding how such species have responded to past glacial cycles can help us forecast their response to today's changing climate. Gray whales are among those marine species likely to be strongly affected by Arctic climate change, but a thorough analysis of past climate impacts on this species has been complicated by lack of information about an extinct population in the Atlantic. While little is known about the history of Atlantic gray whales or their relationship to the extant Pacific population, the extirpation of the Atlantic population during historical times has been attributed to whaling. We used a combination of ancient and modern DNA, radiocarbon dating and predictive habitat modelling to better understand the distribution of gray whales during the Pleistocene and Holocene. Our results reveal that dispersal between the Pacific and Atlantic was climate dependent and occurred both during the Pleistocene prior to the last glacial period and the early Holocene immediately following the opening of the Bering Strait. Genetic diversity in the Atlantic declined over an extended interval that predates the period of intensive commercial whaling, indicating this decline may have been precipitated by Holocene climate or other ecological causes. These first genetic data for Atlantic gray whales, particularly when combined with predictive habitat models for the year 2100, suggest that two recent sightings of gray whales in the Atlantic may represent the beginning of the expansion of this species' habitat beyond its currently realized range. © 2015 John Wiley & Sons Ltd.
Article
Full-text available
Thinning sea ice, thawing permafrost, and greening tundra are among numerous pervasive trends in today’s Arctic.
Article
Full-text available
Commercial vessel traffic through the Bering Strait is increasing. This region has high biological and cultural significance, to which commercial shipping poses several risks. For this environment, these risks include ship strikes of whales, noise disturbance, chronic pollution, and oil spills. Indigenous Chukchi, Iñupiaq, St. Lawrence Island Yupik, Siberian Yupik, and Yup’ik peoples may be affected by proximity between small hunting boats and large commercial vessels leading to swamping or collisions, through displacement of animals or impacts to food security from contaminants, and through loss of cultural heritage if archeological sites and other important places are disturbed by wakes or an increase in people spending time on shore. Several measures are available to govern shipping through the region, including shipping lanes, Areas to Be Avoided (ATBAs), speed restrictions, communications measures, reporting systems, emissions controls, oil spill prevention and preparedness and salvage, rescue tug capability, voyage and contingency planning, and improved charting. These measures can be implemented in various ways, unilaterally by the U.S. or Russia, bilaterally, or internationally through the International Maritime Organization (IMO). Regulatory measures can be established as voluntary measures or as mandatory measures. No single measure will address all risks, but the framework presented herein may serve as a means of identifying what needs to be done and evaluating whether the goal of safe shipping has been achieved.
Article
Full-text available
Spatial variations of processes driving macrofaunal distributions can arise from interactions among topographic features and oceanographic patterns, and are not understood at small scales in the northeastern Chukchi Sea. Benthic macrofauna and environmental characteristics were measured to determine factors driving macrofaunal distributions as part of a multidisciplinary environmental program in the northeastern Chukchi Sea from 2008 to 2010. Macrofauna were sampled in three study areas, named Klondike, Burger, and Statoil, with a van Veen grab at up to 82 stations each year, as well as an area where marine mammals were seen feeding. The macrofaunal assemblages in all study areas were similar in species-composition with deposit-feeding polychaetes (53% of density and of 26% biomass) and bivalves (15% of density and 52% of biomass) collectively the most prominent groups. Maldane sarsi dominated the polychaetes in terms of both density and biomass, while bivalves were numerically dominated by Ennucula tenuis, but their biomass was dominated by larger species such as Macoma calcarea and Astarte borealis. Exceptions occurred in the marine mammal feeding area that was dominated by amphipods (71% of density and 30% biomass). Average densities were higher in Burger than in Klondike or Statoil, while biomass values were similar between Burger and Statoil, and higher in these two study areas than in Klondike. Overall, the distributions, biomass and density of benthic macrofauna reflect the high volume of production reaching the seafloor in the shallow waters of the Chukchi Sea. Variations in community structure among study areas were correlated with water depth and bottom-water temperature. Short-term temporal differences in community structure covaried with interannual oceanographic variations that may have altered food availability, macrofaunal survival, or larval recruitment. Topographic control over circulation appears to be a primary driver in structuring benthic communities within the present study region, as well as throughout the Chukchi Sea.
Article
Full-text available
In the fall of 2011, two gray whales (Eschrichtius robustus) were observed to the west of the Novosibirskiye Is�lands archipelago during a scientific expedition on the Research Vessel “Mikhail Somov”. This is the first scientifically confirmed sighting of gray whales in the Laptev Sea. The range of the presence of this species in the Arctic shelf seas is extended more than 500 km to the west. In the near future, an areal expansion due to the climate changes in the Arctic is suggested.
Article
Full-text available
Gray whales (Eschrichtius robustus, Lilljeborg) migrate north each spring to feeding grounds, mainly in the Bering and Chukchi Seas. Regularly a few individuals travel as far northeast as Point Barrow, Alaska, and a few records have been made of sightings along the Alaska Beaufort Sea coast as far east as Barter Island .... During summer 1980, three sightings of gray whales were made in the Canadian Beaufort Sea, well east of any previously recorded .... All were in open water, well south of the pack ice front. ... These sightings constitute an eastward extension of the known range of the gray whale by 575 km. ... If these individuals migrated north along the coast from Baja California, Mexico, where the largest winter concentrations occur .... [and] If they returned successfully to that wintering area, they swam a round-trip distance of 20,400 km in 9.5 to 11 months. This would be one of the longest known migrations of any mammal species. Key words: gray whale, Eschrichtius robustus, cetacean, marine mammal, migration, Beaufort Sea
Article
Full-text available
The purpose of this study was to evaluate summer and fall residency and habitat selection by gray whales, Eschrichtius robustus, together with the biomass of benthic amphipod prey on the coastal feeding grounds along the Chukotka Peninsula. Thirteen gray whales were instrumented with satellite transmitters in September 2006 near the Chukotka Peninsula, Russia. Nine transmitters provided positions from whales for up to 81 days. The whales travelled within 5 km of the Chukotka coast for most of the period they were tracked with only occasional movements offshore. The average daily travel speeds were 23 km day−1 (range 9–53 km day−1). Four of the whales had daily average travel speeds <1 km day−1 suggesting strong fidelity to the study area. The area containing 95% of the locations for individual whales during biweekly periods was on average 13,027 km2 (range 7,097–15,896 km2). More than 65% of all locations were in water <30 m, and between 45 and 70% of biweekly kernel home ranges were located in depths between 31 and 50 m. Benthic density of amphipods within the Bering Strait at depths <50 m was on average ~54 g wet wt m−2 in 2006. It is likely that the abundant benthic biomass is more than sufficient forage to support the current gray whale population. The use of satellite telemetry in this study quantifies space use and movement patterns of gray whales along the Chukotka coast and identifies key feeding areas.
Article
Full-text available
Why competitive exclusion does not limit the number of coexisting plankton species is a persistent question for community ecology. One explanation, the intermediate disturbance hypothesis (IDH), proposes that elevated species diversity is a product of moderate levels of disturbance that allow the subsequent invasion of less competitive species. Here, we assess the shifts in species diversity in a mysid (Mysidae Dana, 1850) zooplankton community, where at least 10 species have, over the last 15 years, have come to comprise the primary prey base of summer resident gray whales (Eschrictius robustus Lilljeborg, 1861) in Clayoquot Sound, British Columbia. We evaluate trends in the community structure of mysids (species dominance, diversity, and richness) across mysid habitat in the study area during the gray whale foraging season (May–September) for the period 1996 and 2008. Mysid species composition varies among years and diversity has increased as whales shifted their predatory focus from benthic amphipods (Ampeliscidae Costa, 1857) to mysids, near our starting point in 1996. Holmesimysis sculpta Tattersall, 1933 was the dominant species in early years; however, in 2007, the dominance shifted to Neomysis rayi Murdoch, 1885. The habitat restrictions and life history attributes of local populations of coastal mysids leave them vulnerable to the cumulative impacts of increased predation pressure by gray whales. This case study presents a unique examination implicating predation as an agent of disturbance capable of altering the species structure of a local prey community.
Article
Full-text available
Benthic faunal abundance, diversity, and biomass were examined in the northeastern Chukchi Sea to determine factors influencing faunal distribution. Four taxon-abundance-based benthic station groups were identified by cluster analysis and ordination techniques. These groups are explained, using stepwise multiple discriminant analysis, by the gravel-sand-mud and water content of bottom sediments, and the organic carbon/nitrogen (OC/N) ratio. In contrast to previous benthic investigations in the northeastern Bering and southeastern Chukchi Seas, faunal diversity between inshore and offshore regions in our study area were not related to differences in sediment sorting. Instead, regional diversity differences in the northeastern Chukchi Sea were related to greater environmental stresses (e.g. ice gouging, wave-current action, marine-mammal feeding activities) inshore than offshore. The presence of a high benthic biomass north of Icy Cape in the vicinity of Point Franklin and seaward of a hydrographic front is presumably related to an enhanced local depositional flux of particulate organic carbon (POC) in the area. We postulate that POC-rich waters derived from the northern Bering and northwestern Chukchi Seas extend to our study area and the flux of the entrained POC provides a persistent source of carbon to sustain the high benthic biomass. Annual POC enrichment of the coastal region north of Icy Cape is reflected by the great abundance of amphipods and other invertebrates present there and the concentration in summer of walrus Odobenus rosmarus divergens and gray whales Eschrichtius robustus that feed on these invertebrates. This study demonstrates that there can be high standing stocks of benthos in arctic regions with relatively low annual primary production if local carbon is augmented by POC advected from highly productive areas.
Article
Full-text available
Ampeliscid amphipods are the dominant benthic fauna in the northern Bering Sea and the major food of the California gray whale. Field studies indicate that benthic amphipods brought to the surface during gray whale feeding provide a food source for surface-feeding birds (northern fulmars, red phalaropes, black-legged kittiwakes) as well as diving birds (thick-billed murres). A sampling grid was used to document zooplankton and benthic population structure. Neuston tows, behavioral observations and collections of birds for stomach content analyses were made within and outside of 'whale slicks', the muddy plumes at the sea surface marking a site where a feeding whale has surfaced. Results indicate that infaunal amphipods are abundant at the surface in whale slicks, and that abundance and size-class of these floating amphipods directly reflect relative abundance and size-class of the major amphipod species found in the underlying benthos. Surface-feeding birds ate mostly small amphipods at the slicks, which were the dominant amphipod size-class observed in the tows. Birds as divergent in size as northern fulmars (700 g) and red phalaropes (60 g) consumed small amphipods or fragments less than 2 mm in length. Thick-billed murres, which dive to feed, caught the larger amphipods that sank. Location and abundance of northern fulmars and red phalaropes feeding in the study area were positively related to occurrence of feeding whales. The breeding thick-billed murres and black-legged kittiwakes were in a more restricted distribution on the east side of the grid, nearest the seabird colonies on King Island, Alaska, USA. The local distribution of all 4 species is shaped by whale feeding activity, and their diet is a direct reflection of benthic population structure of the northern Bering Sea.
Article
Full-text available
The shallow continental shelves and slope of the Amerasian Arctic are strongly influenced by nutrient-rich Pacific waters advected over the shelves from the northern Bering Sea into the Arctic Ocean. These high-latitude shelf systems are highly productive both as the ice melts and during the open-water period. The duration and extent of seasonal sea ice, seawater temperature and water mass structure are critical controls on water column production, organic carbon cycling and pelagic–benthic coupling. Short food chains and shallow depths are characteristic of high productivity areas in this region, so changes in lower trophic levels can impact higher trophic organisms rapidly, including pelagic- and benthic-feeding marine mammals and seabirds. Subsistence harvesting of many of these animals is locally important for human consumption. The vulnerability of the ecosystem to environmental change is thought to be high, particularly as sea ice extent declines and seawater warms. In this review, we focus on ecosystem dynamics in the northern Bering and Chukchi Seas, with a more limited discussion of the adjoining Pacific-influenced eastern section of the East Siberian Sea and the western section of the Beaufort Sea. Both primary and secondary production are enhanced in specific regions that we discuss here, with the northern Bering and Chukchi Seas sustaining some of the highest water column production and benthic faunal soft-bottom biomass in the world ocean. In addition, these organic carbon-rich Pacific waters are periodically advected into low productivity regions of the nearshore northern Bering, Chukchi and Beaufort Seas off Alaska and sometimes into the East Siberian Sea, all of which have lower productivity on an annual basis. Thus, these near shore areas are intimately tied to nutrients and advected particulate organic carbon from the Pacific influenced Bering Shelf-Anadyr water. Given the short food chains and dependence of many apex predators on sea ice, recent reductions in sea ice in the Pacific-influenced sector of the Arctic have the potential to cause an ecosystem reorganization that may alter this benthic-oriented system to one more dominated by pelagic processes.
Article
Full-text available
A comprehensive environmental monitoring program based on a sound statistical design is necessary to provide estimates of the status of, and changes or trends in, the condition of ecological resources. A sampling design based upon a systematic grid can adequately assess the condition of many types of resources and retain flexibility for addressing new issues as they arise. The randomization of this grid requires that it be regular and retain equal-area cells when projected on the surface of the earth. After review of existing approaches to constructing regular subdivisions of the earth's surface, we propose the development of the sampling grid on the Lambert azimuthal equal-area map projection of the earth's surface to the face of a truncated icosahedron fit to the globe. This geometric model has less deviation in area when subdivided as a spherical tessellation than any of the spherical Platonic solids, and less distortion in shape over the extent of a face when used for a projection surface by the Lambert azimuthal projection. A hexagon face of the truncated icosahedron covers the entire conterminous United States, and can be decomposed into a triangular grid at an appropriate density for sampling. The geometry of the triangular grid provides for varying the density, and points on the grid can be addressed in several ways.
Article
Full-text available
A total of 821 gray whales were seen during aerial surveys in the northeastern Chukchi Sea from July through October 1982–1987. Gray whale distribution extended from south of Point Hope to northeast of Point Barrow, Alaska, between 0.5 and 166 km offshore. Monthly abundance estimates (number of whales/survey hour) were highest in July (6.81) and lowest in October (0.40). Gray whales were usually in open water (82%, n = 670) or in light ice (16%, n = 134) and were seldom associated with heavy ice (2%, n = 17). Most whales were feeding (63%, n = 514), with the majority of the others swimming and diving (24%, n = 193) or forming part of a cow–calf association (9%, n = 72). One group of three whales was involved in sexual activity. Feeding whales were seen most often within 40 km of the shore, but also occurred offshore. Thirty-six gray whale calves were seen. Calf abundance (number of calves/survey hour) was significantly higher (p < 0.001) in July, when 92% (n = 33) of all calves were seen, than in any other month. Most cow–calf pairs were seen nearshore between Point Hope and Point Barrow. Monthly calf ratios (number of calves/number of whales) ranged from 0.09 in July to 0.00 in October, with an overall rate of 0.04.
Article
Full-text available
A total of 176 sightings of 488 gray whales ( Eschrichtius robustus) were made during 85.6 hours of aerial surveys in the southern Chukchi Sea and northern Bering Sea, east of the International Date Line, from August to early November 1980-1989. Surveys were flown infrequently and effort varied considerably between years and geographic areas. Gray whales were sighted in all areas where sur veys were flown, with the exceptions of Kotzebue Sound and Norton Sound. Abundance indices of whales per unit effort (WPUE) in the northe rn Bering Sea were higher than those in the southern Chukchi Sea during every month except September, when survey coverage was inadequate for abundance calculations, indicating comparatively higher overall use of that area or suggesting the onset of the southbound migration. Most gray whales were feeding (57%, n = 276). Incidental sightings of gray whales observed in and near the study area by other researchers were reviewed to better assess gray whale activity and migration patterns.
Article
Gray whales (Eschrichtius robustus) are distributed within the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean. They migrate to high-latitude feeding grounds each spring. Their main feeding grounds in the Arctic include the Chirikov Basin, the northeastern Chukchi Sea from Pt. Hope to Cape Lisburne and Pt. Lay to Pt. Barrow, and the northwestern Chukchi Sea along the Chukotka coast. Although sightings are rare in the Canadian Beaufort Sea, we observed three gray whales in two groups in this area in September 2014. A mud plume was observed near one of the whales, suggesting the animal had been feeding. In the Alaskan Beaufort Sea, large-scale monitoring of the distributions of marine mammals has been continuously conducted since 1979; however, there has been less monitoring in the Canadian Beaufort Sea. Therefore, it is necessary to record opportunistic sightings, such as those described here.
Book
The first edition of this book has established itself as one of the leading references on generalized additive models (GAMs), and the only book on the topic to be introductory in nature with a wealth of practical examples and software implementation. It is self-contained, providing the necessary background in linear models, linear mixed models, and generalized linear models (GLMs), before presenting a balanced treatment of the theory and applications of GAMs and related models. The author bases his approach on a framework of penalized regression splines, and while firmly focused on the practical aspects of GAMs, discussions include fairly full explanations of the theory underlying the methods. Use of R software helps explain the theory and illustrates the practical application of the methodology. Each chapter contains an extensive set of exercises, with solutions in an appendix or in the book’s R data package gamair, to enable use as a course text or for self-study.
Chapter
The analysis of point patterns appears in many different areas of research. In ecology, for example, the interest may be focused on determining the spatial distribution (and its causes) of a tree species for which the locations have been obtained within a study area. Furthermore, if two or more species have been recorded, it may also be of interest to assess whether these species are equally distributed or competition exists between them. Other factors which force each species to spread in particular areas of the study region may be studied as well. In spatial epidemiology, a common problem is to determine whether the cases of a certain disease are clustered. This can be assessed by comparing the spatial distribution of the cases to the locations of a set of controls taken at random from the population.
Article
Over the decade 2004–2013 environmental changes in the Pacific sector of the Arctic have been dramatic enough to suggest that a ‘new normal’ climate is emerging. The clearest indicator of this change is the dramatic loss of sea ice during the summer, which in some years has already resulted in essentially ice-free conditions in this region. For example, between 7 August and 11 October 2012, sea ice concentration in the Beaufort and Chukchi Seas between 70–80° N fell below 20% (with a record minimum concentration of only 5% on 2 September). Thick multiyear sea ice (older than 2 years) has almost entirely disappeared, replaced by thin and more mobile first-year ice. Year-to-year variability in ice concentration is associated with anomalous wind forcing linked to larger-scale atmospheric circulation patterns, which also affect ocean currents, including transport through Bering Strait. With reduced sea ice extent the area of ice-free ocean susceptible to rapid solar heating has increased. More heat is stored in the upper ocean early in the summer melt season and persists later into the autumn freeze-up. Monthly surface air temperature anomalies greater than 6 °C have occurred frequently in the autumn in the Beaufort and Chukchi seas. Environmental variations in the Bering Sea over the last decade have been subtle by comparison, and include an increase in winter sea-ice extent between 2007 and 2013.
Article
In summer 2009 and 2010, as part of Chukchi Sea Offshore Monitoring in Drilling Area – Chemical and Benthos (COMIDA CAB) program, we performed a quantitative assessment of the biomass, abundance, and community structure of benthic infaunal populations of the Northeastern Chukchi Sea. This analysis documented a benthic species inventory of 361 taxa collected from 142 individual van Veen grab samples (0.1 m−2) at 52 stations. Infaunal abundance was dominated by Polychaeta, Mollusca, and Crustacea. Large concentrations of bivalves (up to 1235 m−2; 920.2 gww m−2) were collected south of Hanna Shoal where flow from two water masses converge and deposit labile carbon to the seafloor, as indicated by low surface sediment C:N ratios. Amphipods (up to 1640 m−2; 26.0 gww m−2), and polychaetes (up to 4665 m−2; 114.7 gww m−2) were documented from multiple stations west of and within Barrow Canyon. This high productivity was most likely due to the “canyon effect”, where marine and coastal detrital carbon supplies are channeled by the canyon structure, enhancing carbon deposition and flux, which supports rich benthic communities within the canyon and surrounding areas. To examine the relationships between infaunal distributions of all collected taxa with the physical environment, we used a Biota and Environment matching (BIO–ENV) routine. A combination of water depth, bottom-water temperature and salinity, surface sediment total organic nitrogen (TON) and sediment C:N molar ratios correlated closest with infaunal abundance distribution (ρ=0.54), indicating that multiple factors influence the success of benthic communities. BIO–ENV routines produced similar correlation results when performed on targeted walrus prey items (bivalves (ρ=0.50), polychaetes (ρ=0.53), but gray whale prey items (amphipods) were not strongly correlated to any combination of physical environmental factors (ρ=0.24). Distributions of primary prey items for gray whales (amphipods) and walruses (bivalves, gastropods and polychaetes) were compared with gray whale and walrus distribution as described by sightings from the 2009 and 2010 aerial survey component of COMIDA. In general, concentrations of walruses and their prey occurred in a swath located south of Hanna Shoal and on the shoal itself although the large differences in sea-ice distribution between the two study years showed that walrus distributions were closely linked to sea-ice location. Other areas within Barrow Canyon and the shelf west of the canyon showed high concentrations of benthic amphipods that were coincident with gray whale sightings as quantified by COMIDA aerial surveys. Overall, data collected on this project indicate that the Northeast Chukchi Sea supports a highly productive and diverse benthic ecosystem that is of significant importance to higher trophic level megafauna.
Article
The recent loss of Arctic sea ice provides humans unprecedented access to the region. Marine mammals rely on sound as a primary sensory modality, and the noise associated with increasing human activities offshore can interfere with vital life functions. Many coastal communities rely on marine mammals for food and cultural identity, and subsistence hunters have expressed strong concerns that underwater sound from human activities negatively affects both the animals and hunting success. Federal regulations require scientists and oil and gas operators to acquire incidental harassment authorizations for activities that may disturb marine mammals. Currently, authorization requests are focused on the impacts of sound from activities considered in isolation of one another, and this precludes any possibility of a meaningful analysis of the cumulative impacts from multiple sources. We propose a new assessment framework that is based on the acoustic habitats that constitute the aggregate sound field from multiple sources, compiled at spatial and temporal scales consistent with the ecology of Arctic marine mammals.
Article
The report summarizes the 1991 investigations of the distribution, abundance, migration timing and route, behavior, and habitat relationships of endangered whales in the Alaskan Chukchi and western Beaufort seas (hereafter, study area); 1991 was the third year of a three year (1989-91) study. Data were collected during transect and search surveys flown in a specially modified Grumman Goose (model G21G) aircraft over the study area from 20 September through 7 November. The Bering Sea stock of bowhead whales (Balaena mysticetus) was the principal species studied. Gray whales (Eschrichtius robustus) were also studied, with incidental sightings of all other marine mammals routinely recorded. Data collected during the 1991 study were subsequently integrated with the results of surveys conducted from 1982-1990. In 1991, there were 27 sightings of 32 bowhead whales and 20 sightings of 26 gray whales in the study area from 20 September through October.
Article
Although recent major changes in the physical domain of the Arctic region, such as extreme retreats of summer sea ice since 2007, are well documented, large uncertainties remain regarding responses in the biological domain. In the Pacific Arctic north of Bering Strait, reduction in sea ice extent has been seasonally asymmetric, with minimal changes until the end of June and delayed sea ice formation in late autumn. The effect of extreme ice retreats and seasonal asymmetry in sea ice loss on primary production is uncertain, with no clear shift over time (2003-2008) in satellite-derived chlorophyll concentrations. However, clear changes have occurred during summer in species ranges for zooplankton, bottom-dwelling organisms (benthos), and fish, as well as through the loss of sea ice as habitat and platform for marine mammals.
Article
We report results of ecosystem studies in Monterey Bay, California, during the summer upwelling periods, 1996–99, including impacts of El Niño 1997–98 and La Niña 1999. Random-systematic line-transect surveys of marine mammals were conducted monthly from August to November 1996, and from May to November 1997–99. CTDs and zooplankton net tows were conducted opportunistically, and at 10 predetermined locations. Hydroacoustic backscatter was measured continuously while underway to estimate prevalence of zooplankton, with emphasis on euphausiids, a key trophic link between primary production and higher trophic level consumers.The occurrences of several of the California Current’s most common cetaceans varied among years. The assemblage of odontocetes became more diverse during the El Niño with a temporary influx of warm-water species. Densities of cold-temperate Dall’s porpoise, Phocoenoides dalli, were greatest before the onset of El Niño, whereas warm-temperate common dolphins, Delphinus spp., were present only during the warm-water period associated with El Niño. Rorqual densities decreased in August 1997 as euphausiid backscatter was reduced. In 1998, as euphausiid backscatter slowly increased, rorqual densities increased sharply to the greatest observed values. Euphausiid backscatter further increased in 1999, whereas rorqual densities were similar to those observed during 1998. We hypothesize that a dramatic reduction in zooplankton biomass offshore during El Niño 1997–98 led to the concentration of rorquals in the remaining productive coastal upwelling areas, including Monterey Bay. These patterns exemplify short-term responses of cetaceans to large-scale changes in oceanic conditions.
Article
Gray whales Eschrichtius robustus forage in parts of Clayoquot Sound on several prey species in different habitats. Between June and September in 1.996 and 1997 we carried out analyses of the density, biomass, and other measures of their primary prey species, and of whales' movement patterns in response to prey characteristics. The prey base! consists of hyper-benthic mysids (family Mysidae), pelagic porcelain crab larvae (4 spp. of family Porcellanidae), benthic amphipods (family Ampeliscidae) and benthic ghost shrimp Callianassa californiensis. Whales foraged primarily for mysids, switching to porcelain crab larvae in August, and then to amphipods even later in the season when these organisms increased in body size. In 1997, whales rapidly switched from feeding on planktonic to benthic prey during mid-August. Sampling indicated low numbers of mysids and crab larvae at that time. Selection of amphipod prey was based on high biomass and a high proportion of individuals greater than or equal to6 mm in length. In parts of the study area gray whales did not return to forage on benthic amphipods when this size criteria was not met. A single whale departed from a ghost shrimp feeding ground because its search time for food was long, it achieved only a low biomass removal rate, and it was not able to find sufficient food each day. We show that gray whales are dynamic and selective foragers that switch prey and foraging tactics rapidly to take advantage of short-term availability of energy.
Article
The age class structure of ampeliscid populations is determined largely by competition for space. Population densities of the various ampeliscid species are regulated by a balance between required carbon flux rates to the seafloor, predation rates, competition for space and reproductive potential. The largest taxa require high organic matter input and low predation rates to mature and reproduce. Reductions in organic matter flux favor smaller taxa. Low predation rates favor larger taxa, which can out-compete the smaller taxa for available space. High predation rates favor smaller taxa, which have a higher reproductive rate and are therefore more effective colonizers. The above factors can explain the relative concentrations of Ampelisca macrocephala, Ampelisca birulai and Byblis spp., the most abundant ampeliscids in the northern Bering Sea. Elevated predation losses to gray whales will depress the density of the large-sized A. macrocephala populations and increase the density of the smallest species, A. birulai. Global warming should elevate ampeliscid food requirements, and may also lead to elevated predation rates, both selecting for smaller species.
Article
The climate of the North Pacific underwent an unusual event in the summer of 2005 with a very late spring transition. This event had profound effects on both resident gray whales (Eschrichtius robustus) and their food source, mysids, off Depoe Bay, Oregon. Near bottom swarms of gray whales' major prey item, Holmesimysis sculpta, were sparse until August, a marked contrast to normal years when mysid swarms are abundant all summer. A large percentage of mysid females had empty brood pouches in 2005 while in 2003 and 2004 all observed females had full brood pouches. Gray whales spent little time foraging and spent fewer days in residence than in earlier years. The 2005 resident whales also showed signs of poor body condition, reflecting a nutritional deficit.
Article
The earth's climate is changing, possibly at an unprecedented rate. Overall, the planet is warming, sea ice and glaciers are in retreat, sea level is rising, and pollutants are accumulating in the environment and within organisms. These clear physical changes undoubtedly affect marine ecosystems. Species dependent on sea ice, such as the polar bear (Ursus maritimus) and the ringed seal (Phoca hispida), provide the clearest examples of sensitivity to climate change. Responses of cetaceans to climate change are more difficult to discern, but in the eastern North Pacific evidence is emerging that gray whales (Eschrichtius robustus) are delaying their southbound migration, expanding their feeding range along the migration route and northward to Arctic waters, and even remaining in polar waters over winter—all indications that North Pacific and Arctic ecosystems are in transition. To use marine mammals as sentinels of ecosystem change, we must expand our existing research strategies to encompass the decadal and ocean-basin temporal and spatial scales consistent with their natural histories.
Article
Amphipod crustaceans dominate the benthic community in vast areas of the northern Bering Sea; they are the major prey of the California gray whale Eschrichtius robustus. The protected whale population is growing steadily and may be approaching the carrying capacity of the amphipod community, one of the most productive benthic communities in the world. The abundance and biomass of the amphipod community decreased during the 3 yr period 1986 to 1988, resulting in a 30 % decline in production. High-latitude amphipod populations are characterized by low fecundity and long generation times. Large, long-lived individuals are responsible for the majority of amphipod secondary production. A substantial reduction in the density of large individuals in the population will result in a significant, long-term decrease in production.
Article
Hundreds of gray whales (Eschrichtius robustus) stranded dead along beaches from Mexico to Alaska in 1999 and 2000. The cause of the mortalities remains unknown, but starvation resulting from a reduction in prey, especially in the Chirikov Basin, was suggested as the cause. In the 1980s, the Chirikov Basin was considered a prime gray whale feeding area, but there has been no recent comprehensive assessment of whale or prey distribution and abundance. In 2002, a 5-day survey for gray whales revealed restricted distribution in the basin and a 3- to 17-fold decline in sighting rates. To put these data in context, a retrospective summary of gray whale and benthic fauna distribution and abundance was undertaken. During the 1980s, gray whale sighting rates in the Chirikov Basin were highly variable. Ampeliscid amphipods dominated the benthos where gray whale sighting rates were highest. Available measures of biomass suggest a downturn in amphipod productivity from 1983 to 2000, when estimates of gray whale population size were increasing, suggesting that the whales simply expanded their foraging range. We encourage long-term study of the Chirikov Basin as a location where predator–prey responses to changing ocean climate can be researched, because decadal time series data are available.
Article
We describe gray whale (Eschrichtius robustus) distribution in the south-central Chukchi Sea in relation to environmental factors during two 5-day surveys in June and September of 2003. Whale counts per 10-min scan (an index of relative abundance) ranged from 0 to 41 in June and from 0 to 28 in September. CTD data showed an ocean front around 67.8°N with strong horizontal gradients in temperature, salinity, chlorophyll-a concentration and water-column stability. Highest whale abundance indices occurred in or near the front in both periods. Preliminary qualitative assessment of biological communities in the study area suggests that infaunal clams, echinoderms, euphausids, chaetognaths and Arctic cod were common, while ampeliscid amphipods, the previously abundant infauna (and likely prey) in the nearby Chirikov Basin feeding area, were not dominant. Euphausids may be a prey for gray whales in this area. We suggest that frontal systems may play an important role in eastern North Pacific gray whale foraging grounds. Further study is needed to fully describe the role of frontal systems in gray whale foraging grounds.
Article
HE migratory movements of the California grey whale (Eschrichtius glaucus) are better known than those of any other baleen whale. This is because it is the only species that enters shallow waters to calve and because part of its migration route lies close to the shore. Scammon (1874 p. 23), for example, states that these whales "will be seen . . . following the shore so near that they often pass through the kelp near the beach. It is seldom they are seen far out at sea." Its migration is known in con- siderable detail where it travels along the western coasts of the United States and southern Canada to and from calving grounds in the coastal lagoons of Baja California and adjacent mainland of Mexico. The foregoing comments are based on the works of Scammon (1874), Andrews (1914),