Dramatic multiyear fluctuations in water temperature and seasonal sea ice extent and duration across the BeringâChukchi continental shelf have occurred in this century, raising a pressing ...ecological question: Do such environmental changes alter marine production processes linking primary producers to upper trophicâlevel predators? We examined this question by comparing the blubber fatty acid (FA) composition and stable carbon isotope ratios of individual FA (δ¹³CFA) of adult ringed seals (Pusa hispida), bearded seals (Erignathus barbatus), spotted seals (Phoca largha), and ribbon seals (Histriophoca fasciata), collectively known as âice seals,â sampled during an anomalously warm, low sea ice period in 2002â2005 in the Bering Sea and a subsequent cold, high sea ice period in 2007â2010. δ¹³CFA values, used to estimate the contribution to seals of carbon derived from sea ice algae (sympagic production) relative to that derived from water column phytoplankton (pelagic production), indicated that during the cold period, sympagic production accounted for 62â80% of the FA in the blubber of bearded seals, 51â62% in spotted seals, and 21â60% in ringed seals. Moreover, the δ¹³CFA values of bearded seals indicated a greater incorporation of sympagic FAs during the cold period than the warm period. This result provides the first empirical evidence of an ecosystemâscale effect of a putative change in sympagic production in the Western Arctic. The FA composition of ice seals showed clear evidence of resource partitioning among ringed, bearded, and spotted seals, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. Despite interannual variability, the FA composition of ringed and bearded seals showed little evidence of differences in diet between the warm and cold periods. The findings that sympagic production contributes significantly to food webs supporting ice seals, and that the contribution apparently is less in warm years with low sea ice, raise an important concern: Will the projected warming and continuing loss of seasonal sea ice in the Arctic, and the associated decline of organic matter input from sympagic production, be compensated for by pelagic production to satisfy both pelagic and benthic carbon and energy needs?
Changing environmental conditions in the Pacific Arctic are expected to affect ice-adapted marine food webs. As such, understanding ringed seal (
Pusa hispida
) dive and haul-out behavior is vital to ...understanding if and how these environmental changes affect seal foraging behavior. Working with Alaska Native subsistence hunters, we tagged 14 adult and 20 subadult ringed seals with satellite-linked data recorders in Kotzebue Sound, Alaska, during late-September and October 2007–2009. Information about dive and haul-out behavior in the Bering and Chukchi seas was collected for 12–297 days. We analyzed indices of dive depth, duration, and rate, and haul-out probability using a model selection framework for adults during fall (late-September–November) and winter (December–March) and for subadults during fall, winter, and also spring (April–June). We found differences by season and time of day, but not by sex. Where subadults and adults occurred together, they dove to similar depths; although subadults were commonly located in deeper waters where they generally dove deeper than adults. Both age classes dove longer during winter and subadults tended to make a few more (~3.5) dives per hour than adults. Both age classes hauled out less and dove deeper, longer, and more frequently during midday than at other times of day. We suspect that seals dive deeper during midday because their prey migrates deeper. Dive and haul-out behaviors of ringed seals are influenced by a combination of factors, including prey distribution and abundance, sea ice, and seal diving physiology.
Arctic marine mammals have had little exposure to vessel traffic and potential associated disturbance, but sea ice loss has increased accessibility of Arctic waters to vessels. Vessel disturbance ...could influence marine mammal population dynamics by altering behavioral activity budgets that affect energy balance, which in turn can affect birth and death rates. As an initial step in studying these linkages, we conducted the first comprehensive analysis to evaluate the effects of vessel exposure on Pacific walrus (Odobenus rosmarus divergens) behaviors. We obtained >120,000 h of location and behavior (foraging, in‐water not foraging, and hauled out) data from 218 satellite‐tagged walruses and linked them to vessel locations from the marine automatic identification system (AIS). This yielded 206 vessel‐exposed walrus telemetry hours for comparison to unexposed hours, which we used to assess if vessel exposure altered walrus behavior. We developed a filter to account for misclassification of vessel exposure of telemetered walruses. Then we tested for an effect of vessel exposure on walrus behaviors using a combination of exact and propensity score‐based matching to account for confounding covariates, and we conducted statistical power analyses. We did not detect an effect of vessel exposure on walrus behaviors even when statistical power was high (i.e., for foraging walruses), which may have been due to the sample size‐driven need to define vessel presence within a larger than desired distance (15‐km measured radius) around a walrus. Although this study did not determine at what distance vessel exposure affects walrus behaviors, it provided an upper bound on the distance at which the vessels encountered may disturb foraging walruses. When more situation‐specific information is lacking, this distance could be used as a conservative buffer to maintain between vessels and areas of high use by foraging walruses. Studies on behavioral consequences of closer proximities between walruses and vessels are needed, and our assessments of misclassification rates and statistical power can be used for future studies. We demonstrated that analytical approaches such as matching, which are rarely used in wildlife studies, are particularly useful for testing hypotheses with observational data.
Northwest Passage opens for bowhead whales Heide-Jørgensen, Mads Peter; Laidre, Kristin L; Quakenbush, Lori T ...
Biology letters (2005),
04/2012, Letnik:
8, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The loss of Arctic sea ice is predicted to open up the Northwest Passage, shortening shipping routes and facilitating the exchange of marine organisms between the Atlantic and the Pacific oceans. ...Here, we present the first observations of distribution overlap of bowhead whales (Balaena mysticetus) from the two oceans in the Northwest Passage, demonstrating this route is already connecting whales from two populations that have been assumed to be separated by sea ice. Previous satellite tracking has demonstrated that bowhead whales from West Greenland and Alaska enter the ice-infested channels of the Canadian High Arctic during summer. In August 2010, two bowhead whales from West Greenland and Alaska entered the Northwest Passage from opposite directions and spent approximately 10 days in the same area, documenting overlap between the two populations.
Among emerging threats to the Arctic is the introduction, spread, or resurgence of disease. Marine brucellosis is an emerging disease concern among free-ranging cetaceans and is less well-studied ...than terrestrial forms. To investigate marine-origin Brucella sp. exposure in two beluga stocks in Alaska, USA, this study used serological status as well as real-time polymerase chain reaction (rtPCR) and bacterial culture. In total, 55 live-captured–released belugas were tested for Brucella exposure in Bristol Bay (2008–2016) and 112 (8 live-captured; 104 subsistence-harvested) whales were tested in the eastern Chukchi Sea (2007–2017). In total, 73% percent of Bristol Bay live captures, 50% of Chukchi Sea live captures, and 66% of Chukchi Sea harvested belugas were positive on serology. Only 10 of 69 seropositive belugas were rtPCR positive in at least one tissue. Only one seropositive animal was PCR positive in both the spleen and mesenteric lymph node. All animals tested were culture negative. The high prevalence of seropositivity detected suggests widespread exposure in both stocks, however, the low level of rtPCR and culture positive results suggests clinical brucellosis was not prevalent in the belugas surveyed. Continued detection of Brucella exposure supports the need for long-term monitoring of these and other beluga populations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Display omitted
•Polar bear body condition and recruitment are related to prey and sea ice variables.•These relationships can serve as indicators of polar bear population status.•Predicted body ...condition and recruitment provided good fit to the observed data.•Indicators for the Chukchi Sea polar bear population suggest continued stability.•Environmental indicators can augment wildlife population monitoring.
Monitoring trends in large mammal populations is a fundamental component of wildlife management and conservation. However, direct estimates of population size and vital rates of large mammals can be logistically challenging and expensive. Indicators that reflect trends in abundance, therefore, can be valuable tools for supporting population monitoring. Polar bears have a relatively simple life history such that a few key variables may be effective indicators for tracking changes in body condition and recruitment that affect abundance. Direct estimates of polar bear abundance are difficult to obtain due to their large home ranges in remote Arctic habitats. Changes in abundance associated with environmental conditions appear to affect polar bears largely via effects on female body condition which influence reproduction and cub survival (i.e., recruitment). Loss of sea ice habitat is further limiting researcher access for population monitoring creating a need for alternative approaches. Here we used relationships established from eight years (2008–2017) of data collected on 439 polar bears in the Chukchi Sea, to transform previously published individual-based relationships with annually available sea ice, atmospheric circulation, and prey body condition variables to predict annual mean body condition and recruitment during 2018–2022. Although annual sample sizes were limited for verifying predicted body condition and recruitment via techniques such as cross-validation, in most cases predicted annual means were closely correlated with observed means for 2008–2017. Summer sea ice and prey body condition remained within or increased relative to levels observed during 2008–2017 and predicted polar bear body condition and recruitment during 2018–2022 were largely within or above observed annual means during 2008–2017. A lack of trend in environmental and ecological variables or polar bear body condition and recruitment metrics during 2008–2022 is suggestive that the Chukchi Sea polar bear population was likely stable during this time. Our results provide support for developing models that predict important population parameters of large mammals based on environmental and ecological indicators. Given that trend information is lacking for 10 of the 19 recognized polar bear populations and is outdated for others, the use of environmental and ecological indicators may be particularly useful for augmenting direct estimates of polar bear vital rates in between periods of data collection. Although demographic assessments for polar bears have primarily focused on correlations with sea ice availability, our study and others highlight that prey health is also an important indicator of polar bear population status.
We describe the annual distribution of beluga whales (Delphinapterus leucas) in Bristol Bay, Alaska, using data from 31 satellite‐linked transmitters during 2002–2011. Bristol Bay has one of the ...largest and best studied Pacific salmon (Oncorhynchus spp.) fisheries in the world, allowing us to link the seasonal distribution of belugas to that of salmon. During salmon migrations, beluga movements were restricted to river entrances. Belugas generally did not relocate to different river entrances or change bays during peak salmon periods. However, the location of belugas was not related to the number of salmon passing counting towers, suggesting that belugas were either selecting locations that were good for catching salmon or there were simply more salmon than belugas needed to supply their nutritional needs. The distribution of belugas expanded after salmon runs ended, and was greatest in winter when belugas ranged beyond the inner bays, traveling as far west as Cape Constantine. Belugas continued to frequent the inner bays in winter whenever sea ice conditions allowed, e.g., when winds moved sea ice offshore; however, they were never located south of the southern ice edge in open water or outside of Bristol Bay.
At least five populations (stocks) of beluga whales (Delphinapterus leucas) are thought to winter in the Being Sea, including the Bristol Bay, Eastern Bering Sea (Norton Sound), Anadyr, Eastern ...Chukchi Sea, and Eastern Beaufort Sea (Mackenzie) populations. Belugas from each population have been tagged with satellite‐linked transmitters, allowing us to describe their winter (January–March) distribution. The objectives of this paper were to determine: (1) If each population winters in the Bering Sea, and if so, where? (2) Do populations return to the same area each year (i.e., are wintering areas traditional)? (3) To what extent do the winter ranges of different populations overlap? Tagged belugas from all five populations either remained in, or moved into, the Bering Sea and spent the winter there. Each population wintered in a different part of the Bering Sea and populations with multiple years of data (four of five) returned to the same regions in multiple years. When data were available from two populations that overlapped in the same year, they did not occupy the shared area at the same time. Although our sample sizes were small, the evidence suggests belugas from different populations have traditional winter ranges that are mostly exclusive to each population.
We used satellite telemetry to examine bowhead whale movement behavior, residence times, and dive behavior in the Alaskan Beaufort Sea, 2006 – 18. We explored the timing and duration of use of three ...subregions (western, central, eastern) within the Alaskan Beaufort Sea and applied a two-state switching state-space model to infer bowhead whale behavior state as either transiting or lingering. Transiting whales made direct movements whereas lingering whales changed direction frequently and were presumably feeding. In spring, whales migrated across the Alaskan Beaufort Sea in 7.17 ± 0.41 days, primarily off the continental shelf over deep water. During the autumn migration, whales spent over twice as much time crossing the Alaskan Beaufort Sea than in spring, averaging 18.66 ± 2.30 days, spending 10.05 ± 1.22 days in the western subregion near Point Barrow. Most whales remained on the shelf during the autumn migration and frequently dove to the seafloor, where they spent 45% of their time regardless of behavioral state. Consistent dive behavior in autumn suggests that the whales were looking for food while migrating, and the identification of lingering locations likely reflects feeding. The lack of lingering locations in the eastern and central subregions suggests that prey densities are rarely sufficient to warrant whales pausing their migration for multiple days, unlike in the western subregion near Point Barrow, where bowhead whales regularly lingered for long periods of time.
À l’aide de la télémétrie satellitaire, nous avons examiné les comportements de déplacement des baleines boréales, leurs temps de séjour et leurs comportements de plongée dans les eaux alaskiennes de la mer de Beaufort entre 2006 et 2018. Nous avons exploré le moment et la durée d’utilisation de trois sous-régions (ouest, centre et est) des eaux alaskiennes de la mer de Beaufort et appliqué un modèle à changement binaire espace-état afin de déduire l’état du comportement des baleines boréales comme étant soit en mode transit, soit en mode flânerie. Les baleines en mode transit se déplaçaient de manière directe, tandis que celles en mode flânerie changeaient souvent de direction et étaient probablement en train de se nourrir. Au printemps, les baleines migraient dans les eaux alaskiennes de la mer de Beaufort en 7,17 ± 0,41 jours, principalement au large du plateau continental, dans les profondeurs. Durant la migration automnale, les baleines passaient plus de deux fois plus de temps à traverser les eaux alaskiennes de la mer de Beaufort qu’au printemps, en moyenne 18,66 ± 2,30 jours, passant 10,05 ± 1,22 jours dans la sous-région de l’ouest, près de Point Barrow. Pendant la migration automnale, la plupart des baleines restaient dans le plateau continental et plongeaient souvent jusqu’au plancher océanique, où elles passaient 45 % de leur temps, peu importe leur état de comportement. À l’automne, le comportement de plongée régulier suggère que les baleines étaient à la recherche de nourriture pendant leur migration, et les lieux où elles flânaient étaient vraisemblablement indicateurs d’un mode d’alimentation. L’absence de lieux de flânerie dans les sous-régions de l’est et du centre suggère que la densité des proies est rarement suffisante pour que les baleines justifient d’interrompre leur migration pendant plusieurs jours, contrairement à la sous-région de l’ouest, près de Point Barrow, où les baleines boréales flânaient régulièrement pendant de longues périodes.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Habitat partitioning by adult and subadult ringed seals (
Phoca hispida
) is poorly understood. Conclusions about displacement of subadult seals to suboptimal offshore habitat are largely based on ...nearshore observations as few satellite tagging studies include data from winter months. In this study, movement patterns of 14 subadult and 11 adult ringed seals were monitored in the Bering and Chukchi seas using satellite-linked telemetry. Seals were captured in Kotzebue Sound, Alaska, during October 2007 and 2008 and tracked for 17–297 days. Subadult ringed seals traveled south from the Chukchi Sea into the Bering Sea (
= 36 km/day) as sea ice coverage increased during November and December, remained ~1,000 km south near the ice edge during winter and returned north in the spring with the receding ice edge. Adults remained in the Chukchi and northern Bering seas, where their movements were more localized (
= 22 km/day). Adults were on average 322 km farther from the ice edge and 48 km closer to land and shorefast ice than were subadults. During winter, adult ringed seals construct and maintain breathing holes through the ice, and in spring, females give birth in subnivean lairs, mostly in shorefast ice; adult males defend breeding territories around those lairs. Our results show that subadult ringed seals, unconstrained by the need to maintain territories that contain stable breeding/pupping habitat, moved south to the Bering Sea ice edge, where there are better feeding opportunities, lower energetic costs (no breathing hole maintenance), and less exposure to predation.
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