Ice Seals Research Articles

CS-PHOC: weekly census counts of Southern Ocean phocids at Cape Shirreff, Livingston Island

Rapid climatic warming of the Antarctic Peninsula is driving regional population declines and distribution shifts of predators and prey. Affected species include Antarctic ice seals and the southern elephant seal, all of which rely on the peninsula region for critical stages of their life cycle. However, data collection is difficult in this remote region, and therefore long-term time series with which to identify and investigate population trends in these species are rare. We present the Cape Shirreff Phocid Census (CS-PHOC) dataset: weekly counts of phocids (crabeater, leopard, southern elephant, and Weddell seals) hauled out at Cape Shirreff, Livingston Island, during most austral summers since 1997. Data from these censuses were cleaned and aggregated, resulting in robust and comparable count data from 284 censuses across 23 field seasons. The CS-PHOC dataset, which is publicly available through the SCAR Biodiversity Portal, will be updated yearly to provide important information about Southern Ocean phocids in the Antarctic Peninsula.

Transformative Ecological and Human Impacts from Diminished Sea Ice in the Northern Bering Sea

Abstract Our goal is to tie climate-scale meteorology to regional physics and ecosystem changes and demonstrate a few resulting impacts to which regional peoples are having to respond in the Alaskan Bering Strait region. The sea ice loss events in the winters of 2017/18 and 2018/19 initiated a series of marine environmental, ecological, and industrial changes through a chain of connected events from jet-stream meanders, storms, southerly winds, warmer sea temperatures, and minimum sea ice cover. Resulting impacts continue as coastal communities respond to ongoing nutritional, cultural, and economic challenges. Global warming potentially initiated these events through a weakened atmospheric Arctic Front. Ecological shifts included a transition/reorganization of the Bering Strait regional marine ecosystem. Subsequent changes included shifts in zooplankton species, increases in large-bodied, predatory fish species moving northward, an ice seal unusual mortality event, and seven consecutive years of multispecies seabird die-offs. These changes in the marine ecosystem create a serious food security concern. Ongoing impacts include large, toxic harmful algal blooms and coastal erosion. Recent changes to the maritime industries of the transboundary waters of the Bering Strait include increased industrial ship traffic, planned development of the Port of Nome, and northward proximity of foreign fishing activity. Projections for the next decades are for an increasing frequency of low sea ice years and continuing ecosystem and industrial transitions that contribute to increasing economic and food security concerns for the 16 coastal communities that compose the Bering Strait region. Significance Statement Extreme events in the atmosphere/oceans and resultant record sea ice minimums in 2018 and 2019 were manifested in marine ecosystem transitions and maritime industry impacts. This led to ongoing concerns over the food safety and food security of marine resources essential to the nutritional, cultural, and economic well-being of Alaskan coastal communities of the Bering Strait region. Persistent weakening of the Arctic Front may signal an increased frequency of low sea ice events into the next decades.

Insights into carbonate environmental conditions in the Chukchi Sea

Abstract. Healthy Arctic marine ecosystems are essential to the food security and sovereignty, culture, and wellbeing of Indigenous Peoples in the Arctic. At the same time, Arctic marine ecosystems are highly susceptible to impacts of climate change and ocean acidification. While increasing ocean and air temperatures and melting sea ice act as direct stressors on the ecosystem, they also indirectly enhance ocean acidification, accelerating the associated changes in the inorganic carbon system. Yet, much is to be learned about the current state and variability of the inorganic carbon system in remote, high-latitude oceans. Here, we present time series (2016–2020) of pH and the partial pressure of carbon dioxide (pCO2) from the northeast Chukchi Sea continental shelf. The Chukchi Ecosystem Observatory includes a suite of subsurface year-round moorings sited amid a biological hotspot that is characterized by high primary productivity and a rich benthic food web that in turn supports coastal Iñupiat, whales, ice seals, walrus (Odobenus rosmarus), and Arctic cod (Boreogadus saida). Our observations suggest that near-bottom waters (33 m depth, 13 m above the seafloor) are a high carbon dioxide and low pH and aragonite saturation state (Ωarag) environment in summer and fall, when organic material from the highly productive summer remineralizes. During this time, Ωarag can be as low as 0.4. In winter, when the site was covered by sea ice, pH was <8 and Ωarag remained undersaturated under the sea ice. There were only two short seasonal periods with relatively higher pH and Ωarag, which we term ocean acidification relaxation events. In spring, high primary production from sea ice algae and phytoplankton blooms led to spikes in pH (pH > 8) and aragonite oversaturation. In late fall, strong wind-driven mixing events that delivered low-CO2 surface water to the shelf also led to events with elevated pH and Ωarag. Given the recent observations of high rates of ocean acidification and a sudden and dramatic shift of the physical, biogeochemical, and ecosystem conditions in the Chukchi Sea, it is possible that the observed extreme conditions at the Chukchi Ecosystem Observatory are deviating from the carbonate conditions to which many species are adapted.

Pack-ice seals contribute to biological transfers of iron in the Southern Ocean

Pack-ice seals contribute to biological transfers of iron in the Southern Ocean

Large and in charge: cortisol levels vary with sex, diet, and body mass in an Antarctic predator, the leopard seal

Evaluating physiological responses in the context of a species’ life history, demographics, and ecology is essential to understanding the health of individuals and populations. Here, we measured the main mammalian glucocorticoid, cortisol, in an elusive Antarctic apex predator, the leopard seal (Hydrurga leptonyx). We also examined intraspecific variation in cortisol based on life history (sex), morphometrics (body mass, body condition), and ecological traits (δ15N, δ13C). To do this, blood samples, life history traits, and morphometric data were collected from 19 individual leopard seals off the Western Antarctic Peninsula. We found that adult leopard seals have remarkably high cortisol concentrations (100.35 ± 16.72 μg/dL), showing the highest circulating cortisol concentration ever reported for a pinniped: 147 μg/dL in an adult male. Leopard seal cortisol concentrations varied with sex, body mass, and diet. Large adult females had significantly lower cortisol (94.49 ± 10.12 μg/dL) than adult males (120.85 ± 6.20 μg/dL). Similarly, leopard seals with higher isotope values (i.e., adult females, δ15N: 11.35 ± 0.69‰) had lower cortisol concentrations than seals with lower isotope values (i.e., adult males, δ15N: 10.14 ± 1.65‰). Furthermore, we compared cortisol concentrations across 26 closely related Arctoid taxa (i.e., mustelids, bears, and pinnipeds) with comparable data. Leopard seals had the highest mean cortisol concentrations that were 1.25 to 50 times higher than other Arctoids. More broadly, Antarctic ice seals (Lobodontini: leopard seal, Ross seal, Weddell seal, crabeater seal) had higher cortisol concentrations compared to other pinnipeds and Arctoid species. Therefore, high cortisol is a characteristic of all lobodontines and may be a specialized adaptation within this Antarctic-dwelling clade. Together, our results highlight exceptionally high cortisol concentrations in leopard seals (and across lobodontines) and reveal high variability in cortisol concentrations among individuals from a single location. This information provides the context for understanding how leopard seal physiology changes with life history, ecology, and morphology and sets the foundation for assessing their physiology in the context of a rapidly changing Antarctic environment.

Trends in Subsistence Harvests of Ice Seals in the Yukon-Kuskokwim Delta Region, Alaska, 1962 – 2018

Ringed (Pusa hispida), bearded (Erignathus barbatus), spotted (Phoca largha), and ribbon seals (Histriophoca fasciata), or ice seals, are harvested for subsistence purposes by many Alaska Native communities. We address trends in the subsistence harvest of ice seals for the Yukon-Kuskokwim Delta region of Alaska for more than 50 years using two types of data collected by the Alaska Department of Fish and Game: (1) bounty data collected from 1962 to 1972 for 16 communities, and (2) household survey data collected for seven of these communities from 1997 to 2018. Both include information on the number of ice seals harvested by each community annually. In addition, more detailed household surveys were conducted from 2008 to 2018 for Hooper Bay, Tununak, and Quinhagak, which collected data on the number of seals harvested by species, the percentage of households engaged in hunting or using seal products, and hunter perceptions. For the bounty period, we identified several years where most communities had above or below average harvests, suggesting regional drivers contributed to patterns in the ice seal harvest. For the seven communities with household survey data, the mean total harvest estimate during the household survey years was only slightly lower than during the bounty period, however, the human population doubled during this time, resulting in a substantial decline in the mean number of seals harvested per person. The more detailed surveys for Hooper Bay, Tununak, and Quinhagak also showed declines in seal harvests during the most recent decade. The declining harvest in some communities may be driven by reduced participation in hunting and less use of seal products. Ongoing sea ice loss is also likely contributing to the decline in harvest across the region. Current seal population estimates indicate all four species are abundant in Alaskan waters, and most hunters have not observed changes in seal abundance.

SealNet 2.0: Human-Level Fully-Automated Pack-Ice Seal Detection in Very-High-Resolution Satellite Imagery with CNN Model Ensembles

Pack-ice seals are key indicator species in the Southern Ocean. Their large size (2–4 m) and continent-wide distribution make them ideal candidates for monitoring programs via very-high-resolution satellite imagery. The sheer volume of imagery required, however, hampers our ability to rely on manual annotation alone. Here, we present SealNet 2.0, a fully automated approach to seal detection that couples a sea ice segmentation model to find potential seal habitats with an ensemble of semantic segmentation convolutional neural network models for seal detection. Our best ensemble attains 0.806 precision and 0.640 recall on an out-of-sample test dataset, surpassing two trained human observers. Built upon the original SealNet, it outperforms its predecessor by using annotation datasets focused on sea ice only, a comprehensive hyperparameter study leveraging substantial high-performance computing resources, and post-processing through regression head outputs and segmentation head logits at predicted seal locations. Even with a simplified version of our ensemble model, using AI predictions as a guide dramatically boosted the precision and recall of two human experts, showing potential as a training device for novice seal annotators. Like human observers, the performance of our automated approach deteriorates with terrain ruggedness, highlighting the need for statistical treatment to draw global population estimates from AI output.

Assessing vocal activity patterns of leopard seals (Hydrurga leptonyx) In the Bransfield Strait, Antarctica using machine learning

Leopard seals (Hydrurga leptonyx) are widely distributed pack-ice seals in Antarctic and sub-Antarctic waters. As apex predators, these animals play a crucial role in the Southern Ocean food web. Data on population-level changes in their abundance and distribution may be a useful indicator of ecosystem-level changes in this unique and fragile environment. Over the past few decades, many studies have conclusively shown that passive acoustic monitoring (PAM) is an effective tool to monitor the abundance and distribution of vocally active marine mammals in remote and inaccessible areas for extended periods. However, handling and analyzing the vast amount of PAM data being collected remains challenging. Within the scope of this effort, we explored the use of a machine learning algorithm (convolutional neural network; CNN) to automatically detect the ‘low double trill’; one of the most common leopard seal vocalizations, in three years of continuous acoustic data recorded in the Bransfield Strait, Antarctica between 2005 and 2008. After optimizing the algorithm, we evaluated its detection performance on various temporal scales (weeks, days, hours) to assess if CNNs are useful for monitoring leopard seal populations at ecologically relevant scales in the Southern Ocean.

Seasonal and Developmental Patterns of Energy Intake and Growth in Alaskan Ice Seals

Seasonal and Developmental Patterns of Energy Intake and Growth in Alaskan Ice Seals

Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals

The quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx). We used SI data of their vibrissae and FA data of their outer blubber to produce comparable diet estimates for the same individuals. Both SI and FA models predicted the same main diet components, although the predicted proportions differed. For the crabeater seal, both methods identified krill, Euphausia superba, as the main, and almost exclusive, food item, although the FA model estimated a slightly lower proportion, potentially due to the low lipid content of krill compared to the fish species used in the model. For the Weddell seal the FA model identified the fish Pleuragramma antarcticum as the most important prey, whereas the SI model was not able to distinguish among prey species, identifying a ‘fish-squid’ group as the main diet component. For the leopard seal, both models identified krill as the main contributor; however, the predicted proportions for the secondary sources differed. Although vibrissae and outer blubber may not represent the same timeframe, the use of MixSIAR with FA data provides diet estimates comparable to those obtained with SI data, thus, both approaches were complimentary. The use of both biotracers offers a feasible option to study diets of wild animals in a quantitative manner.

Ice seals as sentinels for algal toxin presence in the Pacific Arctic and subarctic marine ecosystems.

Domoic acid (DA) and saxitoxin (STX)‐producing algae are present in Alaskan seas, presenting exposure risks to marine mammals that may be increasing due to climate change. To investigate potential increases in exposure risks to four pagophilic ice seal species (Erignathus barbatus, bearded seals; Pusa hispida, ringed seals; Phoca largha, spotted seals; and Histriophoca fasciata, ribbon seals), this study analyzed samples from 998 seals harvested for subsistence purposes in western and northern Alaska during 2005–2019 for DA and STX. Both toxins were detected in bearded, ringed, and spotted seals, though no clinical signs of acute neurotoxicity were reported in harvested seals. Bearded seals had the highest prevalence of each toxin, followed by ringed seals. Bearded seal stomach content samples from the Bering Sea showed a significant increase in DA prevalence with time (logistic regression, p = .004). These findings are consistent with predicted northward expansion of DA‐producing algae. A comparison of paired samples taken from the stomachs and colons of 15 seals found that colon content consistently had higher concentrations of both toxins. Collectively, these results suggest that ice seals, particularly bearded seals (benthic foraging specialists), are suitable sentinels for monitoring HAB prevalence in the Pacific Arctic and subarctic.

Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea.

Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial-temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition, and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008-2017. The body condition of ringed seals (Pusa hispida), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals (Erignathus barbatus) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short term. In the long term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat.

Summer circumpolar acoustic occurrence and call rates of Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals in the Southern Ocean

Two of the Antarctic pack ice seals, Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals, are extremely difficult to study via traditional visual survey techniques, yet are ideal for an acoustic survey as they are highly vociferous and produce an array of underwater sounds during the austral summer. To determine their acoustic occurrence in the Antarctic pack ice, we use their calls, detected within 680 acoustic recordings made between 1999 and 2009 as part of two multinational programmes. Siren calls of Ross seals were detected mainly in January, and 9.88 calls per minute from low siren calls was the highest call rate for this species. High numbers of Ross seal calls were detected close to the ice edge in areas between 0° and 20° E and 60° and 130° E, suggesting these are important summer habitats. Leopard seal calls were detected mainly in December and January, and December had the highest percentage of calls. Call rate of 11.93 calls per minute from low double trills was the highest call rate for leopard seals. Leopard seal calls were detected throughout the Southern Ocean with more calls detected throughout the pack ice. There was little spatio-temporal overlap in call occurrence of Ross and leopard seals, but both species were more vocally active during the day. Longitude and latitude were the most important predictors of Ross seal occurrence, and month of the year highly predicted leopard seal occurrence. This is the first study to examine the circumpolar acoustic occurrence of Ross and leopard seals in the Southern Ocean pack ice.

Habitat-based density models of pack-ice seal distribution in the southern Weddell Sea, Antarctica

Climate variability and changes in sea ice dynamics have caused several ice-obligate or krill-dependent populations of marine predators to decline, eliciting concern about their demographic persistence and the indirect ecological consequences that predator depletions may have on marine ecosystems. Pack-ice seals are dominant ice-obligate predators in the Antarctic marine ecosystem, but there is considerable uncertainty about their abundance and population trends. We modelled the density and distribution of pack-ice seals as a function of environmental covariates in the southern Weddell Sea, Antarctica. Our density surface modelling approach used data from aerial surveys of pack-ice seals collected in the 2013/14 austral summer. Crabeater seals Lobodon carcinophaga, the most numerous pack-ice seal we observed, occurred at the highest densities in areas with extensive sea ice near the continental shelf break, but were almost absent in areas of similar sea ice concentration in the southern extent of the Weddell Sea. The highest densities of Weddell seals Leptonychotes weddelli, which were less abundant than crabeater seals within the pack-ice habitat, were predicted to occur over the continental shelf, near the shelf break. The distribution of both seal species broadly corresponded with the distribution and relative abundance of their main prey (Antarctic krill Euphausia superba and Antarctic silverfish Pleuragramma antarctica) obtained from concurrent ecosystem surveys. Ross seals Ommatophoca rossii and leopard seals Hydrurga leptonyx were not detected at all and are apparently rare within the southern Weddell Sea. These results can contribute to biodiversity assessments in the context of marine protected area planning in this region of the Southern Ocean.

Antarctic pack ice seal observations during spring across the Lazarev Sea

Abstract The distribution, density and percentage contribution of pack ice seals during ship-board censuses in the marginal sea ice zone beyond the Lazarev Sea in spring 2019 are presented. Adult/juvenile crabeater seals (n = 19), leopard seals (n = 3) and Ross seals (n = 10) were sighted during 582.2 nm of censuses along the ship’s track line in the area bounded by 00°00’–22°E and 56°–60°S. Antarctic fur seals (n = 21) were only encountered on the outer fringes of the pack ice, and Weddell seals were absent due to their primary use of fast ice and inner pack ice habitats close to the coast. Crabeater seal sightings included juveniles (n = 2) and another four groups of 2–3 unclassified crabeater seals, singletons (n = 5), single mothers with pups (n = 3) and a family group (n = 1 triad). Only one leopard seal attended a pup, while no Ross seal pups were located. The survey was likely of insufficient effort, in both extent (north of 60°S) and duration (18 days), to locate seals in considerable numbers this early (late October/early November) in their austral spring breeding season.

SealNet: A fully-automated pack-ice seal detection pipeline for sub-meter satellite imagery

Antarctic pack-ice seals, a group of four species of true seals (Phocidae), play a pivotal role in the Southern Ocean foodweb as wide-ranging predators of Antarctic krill (Euphausia superba). Due to their circumpolar distribution and the remoteness and vastness of their habitat, little is known about their population sizes. Estimating pack-ice seal population sizes and trends is key to understanding how the Southern Ocean ecosystem will react to threats such as climate change driven sea ice loss and krill fishing. We present a functional pack-ice seal detection pipeline using Worldview-3 imagery and a Convolutional Neural Network that counts and locates seal centroids. We propose a new CNN architecture that detects objects by combining semantic segmentation heatmaps with binary classification and counting by regression. Our pipeline locates over 30% of seals, when compared to consensus counts from human experts, and reduces the time required for seal detection by 95% (assuming just a single GPU). While larger training sets and continued algorithm development will no doubt improve classification accuracy, our pipeline, which can be easily adapted for other large-bodied animals visible in sub-meter satellite imagery, demonstrates the potential for machine learning to vastly expand our capacity for regular pack-ice seal surveys and, in doing so, will contribute to ongoing international efforts to monitor pack-ice seals.

Subsistence harvest of ringed, bearded, spotted, and ribbon seals in Alaska is sustainable

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 40:1-16 (2019) - DOI: https://doi.org/10.3354/esr00973 Subsistence harvest of ringed, bearded, spotted, and ribbon seals in Alaska is sustainable Mark A. Nelson1, Lori T. Quakenbush1,*, Brian D. Taras1, Ice Seal Committee2 1Alaska Department of Fish and Game, Fairbanks, AK 99701, USA 2North Slope Borough, Utqiaġvik, AK 99723, USA *Corresponding author: lori.quakenbush@alaska.gov ABSTRACT: In 2012, climate-warming related decreases in sea ice led to listings of ringed Pusa hispida and bearded seals Erignathus barbatus as threatened under the United States Endangered Species Act (ESA) prior to evidence of population declines. These and 2 other ice-associated species (spotted Phoca largha and ribbon seals Histriophoca fasciata) are vital subsistence resources to coastal Alaska Native communities. ESA-related assessments concluded that subsistence removals (seals that were harvested as well as those that were struck and lost) were sustainable; however, limited data precluded a quantitative evaluation. Potential biological removal (PBR), defined as the maximum number of animals that can be removed from a stock while allowing the stock to reach or maintain its optimal sustainable size, is typically used to determine whether human-caused mortality is sustainable. Although developed to address commercial fisheries bycatch, PBR serves as a conservative measure of sustainability. We compiled annual subsistence removal of ice seals in Alaska between 1992 and 2014 for 41 of 55 ice seal hunting communities and used per capita (based on the 2015 human population) removal estimates from surveyed communities to estimate regional and statewide average removals. We used average per capita values of harvest, combined with struck and lost, for surveyed communities (average removals) to extrapolate to unsurveyed communities. To account for underreported harvest, we also extrapolated using maximum harvest values, providing a liberal estimate. Both the average and liberal estimates of removals were below PBR for all 4 species. Thus, the best available data indicate that subsistence hunting is currently sustainable for all 4 species of ice seals. KEY WORDS: Erignathus barbatus · Pusa hispida · Phoca hispida · Phoca largha · Histriophoca fasciata · Ice seal · Potential biological removal · Struck and lost Full text in pdf format NextCite this article as: Nelson MA, Quakenbush LT, Taras BD, Ice Seal Committee (2019) Subsistence harvest of ringed, bearded, spotted, and ribbon seals in Alaska is sustainable. Endang Species Res 40:1-16. https://doi.org/10.3354/esr00973 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 40. Online publication date: September 19, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Leukocyte counts in three sympatric pack-ice seal species from the western Antarctic Peninsula

Global warming, and its consequences, constitute one of the main stressors for organisms worldwide, affecting different factors such as the geographic distribution and the abundance of parasites, which in turn can affect the immune system of their hosts, and vice versa. Therefore, it is important to have baseline information on immune parameters of organisms in order to make future comparisons within this changing ecological context. Here, we report on the leukocyte counts of the Antarctic pack ice seals, the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard (Hydrurga leptonyx) seals, sampled off the western Antarctic Peninsula. We captured and sampled seals in the pack ice off the Danco Coast, Antarctica in the austral summers, January to March, of 2015 and 2016. The leukocyte counts, along with the counts of each different leukocyte (e.g., basophil, neutrophil, eosinophil, lymphocyte and monocyte), were made from blood smears viewed under the light microscope. As a potential stress indicator, we examined whether seals with lice, so presumably under greater physiological stress, had changes in leukocyte counts, including higher ratios of neutrophil-to-lymphocytes (N/L ratio). Leukocyte counts were different among the seal species. While crabeater and Weddell seals had higher neutrophil counts, followed by lymphocyte counts, leopard seals had the reverse pattern. Basophil, eosinophil, and lymphocyte counts were higher in the leopard seal, while the N/L ratio, as well as the neutrophil counts, were higher for the crabeater seal. We show, for the Weddell seal, that the animals with lice were more likely to have higher N/L ratios. This suggests that future research into the potential of the N/L index as a stress indicator, that incorporates additional stress parameters including cortisol concentrations, oxidative damage, as well as other measures of immune function, is warranted for the pack ice seals. Our results are a first step towards establishing leukocyte count baselines for the Antarctic pack ice seals off the western Antarctic Peninsula.

Index‐based approach for estimating vulnerability of Arctic biota to oil spills

AbstractRisk of an Arctic oil spill has become a global matter of concern. Climate change induced opening of shipping routes increases the Arctic maritime traffic which exposes the area to negative impacts of potential maritime accidents. Still, quantitative analyses of the likely environmental impacts of such accidents are scarce, and our understanding of the uncertainties related to both accidents and their consequences is poor. There is an obvious need for analysis tools that allow us to systematically analyze the impacts of oil spills on Arctic species, so the risks can be taken into account when new sea routes or previously unexploited oil reserves are utilized. In this paper, an index‐based approach is developed to study exposure potential (described via probability of becoming exposed to spilled oil) and sensitivity (described via oil‐induced mortality and recovery) of Arctic biota in the face of an oil spill. First, a conceptual model presenting the relevant variables that contribute to exposure potential and sensitivity of key Arctic marine functional groups was built. Second, based on an extensive literature review, a probabilistic estimate was assigned for each variable, and the variables were combined to an index representing the overall vulnerability of Arctic biota. The resulting index can be used to compare the relative risk between functional groups and accident scenarios. Results indicate that birds have the highest vulnerability to spilled oil, and seals and whales the lowest. Polar bears’ vulnerability varies greatly between seasons, while ice seals’ vulnerability remains the same in every accident scenario. Exposure potential of most groups depends strongly on type of oil, whereas their sensitivity contains less variation.

Acoustic occurrence and behavior of ribbon seals (Histriophoca fasciata) in the Bering, Chukchi, and Beaufort seas

Due to the difficulty of studying ice seals in their natural environment, distribution and movement patterns of ribbon seals (Histriophoca fasciata) over large spatio-temporal scales are poorly understood. In this study, we analyzed their distribution patterns in the Bering, Chukchi, and Beaufort seas, using passive acoustic data collected between August 2012 and July 2013 at 53 recording sites. Ribbon seal downsweeps were found using spectrogram correlation autodetection, at 30 of these recording sites. These detections were further manually analyzed to investigate the vocal repertoire and quantify the diel pattern in acoustic presence. We found that the Beaufort Sea shelf and the northern Bering Strait/southern Chukchi Sea are ecologically important for ribbon seals during the open-water season. Our results suggest that the northeastern Chukchi Sea serves as part of a migration corridor to and from the Chukchi Plateau and/or Beaufort Sea. In the Bering Sea, most detections occurred from February to June. Vocal activity was higher at nighttime than during the daytime prior to the peak calling period, while during the peak calling period, diel rhythm became less pronounced. The number of calls, proportional use of downsweeps, and bandwidth of downsweeps (estimated broadband source level 170–178 dB re 1 μPa-m) increased during the breeding period, from March to June, peaking in May. An additional call type, the “shuffle”, was identified in this study. These results improve our understanding of the migration, occurrence, and acoustic behavior of ribbon seals in the Bering, Chukchi, and Beaufort seas.