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19 results for “Steller sea lion.”
Beta-hydroxybutyrate ketone concentrations via ketometer and colorimetric assay in Steller sea lion whole blood and plasma
<p>We evaluated the Precision Xtra™ ketometer during a larger study categorizing free-ranging Steller sea lion (<em>Eumetopias jubatus</em>; SSL) pup fasting status, necessitating identification of plasma β-hydroxybutyrate concentrations ([β-HBA]) around a < and ≥0.3 mmol/L threshold. Whole blood samples mixed with sodium heparin (NaHep) or ethylenediaminetetraacetic acid liquid anticoagulants were tested <10 minutes after collection (n=14; triplicate technical replicates). Plasma (stored at -80°C, NaHep, <em>Thaw1</em>) measured via our laboratory's <em>Reference Assay </em>(Sigma Aldrich, St. Louis, MO, Kit #MAK041) served as the standard [β-HBA] for ketometer comparisons. Our observed β-HBA range (0.0–1.6 mmol/L), consistent with published [β-HBA] of free-ranging Otariid pups, represented the lower 20% of the ketometer's range (0.0–8.0 mmol/L). The maximal coefficient of variation (%CV) of ketometer technical replicates was 9.1% (NaHep, whole blood). The majority of ketometer technical replicate sets (84%, including all matrices, anticoagulants, and thawings) were identical (CV=0%). We found linear relationships and agreement of ketometer [β-HBA] between whole blood preserved with different anticoagulants and between whole blood and plasma (<em>Thaw1</em>) measurements. The ketometer produced results with linearity to the <em>Reference Assay</em> for both whole blood and plasma (<em>Thaw1</em>). We identified a non-linear relationship between plasma at <em>Thaw1</em> and <em>Thaw2</em> (tested four months apart, NaHep), as only samples with higher SSL [B-HBA] decreased in concentration, and all others remained the same. With respect to categorizing SSL pup fasting, the ketometer % Accuracy, %Sensitivity, and %Specificity for samples with <em>Reference Assay</em> β-HBA <0.2 and >0.4 mmol/L were 100%. We adopted a modified procedure: plasma samples with mean ketometer concentrations ±0.1 mmol/L of 0.3 mmol/L β-HBA were re-evaluated using the <em>Reference Assay</em>, improving measurement precision from tenths (ketometer) to thousandths (assay) mmol/L. The Precision Xtra™ ketometer was valuable to our application, over the range of [β-HBA] observed in SSL pup plasma and whole blood samples.</p>
Mark-recapture dataset to estimate age-specific reproductive rates of Steller sea lions in Southeast Alaska
<p>Age, region, and year-specific estimates of reproduction are needed for monitoring wildlife populations during periods of ecosystem change. Population dynamics of Steller sea lions (<em>Eumetopias jubatus</em>) in Southeast Alaska varied regionally (with high population growth and survival in the north versus the south) and annually (with reduced adult female survival observed following a severe marine heatwave event), but reproductive performance is currently unknown. We used mark-resighting data from 1,006 SSL females marked as pups at age ~3 weeks of age from 1994–1995 and 2001–2005 and resighted from 2002–2019 (to a maximum age of 25) to examine age-, region-, and year-specific reproduction. In the north versus the south, age of first reproduction was earlier (beginning at age 4 versus age 5, respectively) but annual birth probabilities of parous females were reduced by 0.05. In an average year pre-heatwave, the proportion of females with pup at the end of the pupping season peaked at ages 12–13 with ~0.60/0.65 (north/south) with pup, ~0.30/0.25 with juvenile, and ~0.10 (both regions) without a dependent. In both regions, reproductive senescence was gradual after age 12: ~0.40, 0.40, and 0.20 of females were in these reproductive states, respectively, by age 20. Correcting for neonatal mortality, true birth probabilities at peak ages were 0.66/0.72 (north/south). No cost of reproduction on female survival was detected, but pup production remained lower (-0.06) after the heatwave event, which if sustained would result in population decline in the south. Reduced pup production and greater retention of juveniles during periods of poor prey conditions may be an important strategy for Steller sea lions in Southeast Alaska, where fine-tuning reproduction based on nutritional status may improve the lifetime probability of producing pups under good conditions in a variable and less productive environment. </p>
Steller sea lion pup plasma metabolites
<p>Geographic differences in population growth trends are well-documented in Steller sea lions (<em>Eumetopias</em> <em>jubatus</em>), a species of North Pacific pinniped listed under the U.S. Endangered Species Act in 1990 following a marked decline in population abundance that began during the 1970s. As population growth is intrinsically linked to pup production and survival, examining factors related to pup physiological condition provides useful information to management authorities regarding potential drivers of regional differences. During dam foraging trips, pups predictably transition among three fasting phases, distinguished by the changes in the predominant metabolic byproduct. We used standardized ranges of two plasma metabolites (blood urea nitrogen and β–hydroxybutyrate) to assign pups to fasting categories (n=1528, 1990–2016, 12 subpopulations): <em>Recently Fed–Phase I</em> (digestion/assimilation–expected hepatic/muscle glycogen usage), <em>Phase II</em> (expected lipid utilization), transitioning between <em>Phases II–III</em> (expected lipid utilization with increased protein reliance), or <em>Phase III</em> (expected protein catabolism). As anticipated, the majority of pups were classified as <em>Recently Fed–Phase I </em>(overall mean proportion=0.72) and few pups as <em>Phase III</em> (overall mean proportion=0.04). By further comparing pups in Short (<em>Recently Fed–Phase II</em>) and Long (all other pups) duration fasts, we identified three subpopulations with significantly (p<0.03) greater proportions of pups dependent upon endogenous sources of energy for extended periods, during a life stage of somatic growth and development: the 1) central (0.27 ± 0.09) and 2) western (0.36 ± 0.13) Aleutian Island (declining population trend) and 3) southern Southeast Alaska (0.32 ± 0.06; increasing population trend) subpopulations had greater Long fast proportions than the eastern Aleutian Islands (0.10 ± 0.05; stabilized population). Due to contrasting population growth trends among these highlighted subpopulations over the past 50+ years, both density-independent and density-dependent factors likely influence the dam foraging trip duration, contributing to longer fasting durations for pups at some rookeries.</p>
Mark-recapture dataset to estimate age-specific reproductive rates of Steller sea lions in Southeast Alaska
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Steller sea lion pup plasma metabolites
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Beta-hydroxybutyrate ketone concentrations via ketometer and colorimetric assay in Steller sea lion whole blood and plasma
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Data from: Geographic variation in diet, prey resources and exposure to parasites and saxitoxin in Steller sea lions in the Gulf of Alaska
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Data from: Biogeochemical patterns in prey species reveal complex mercury exposure pathways from the environment to Aleutian Steller sea lions
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Data from: Spatial distribution, movements, and geographic range of Steller sea lions (Eumetopias jubatus) in Alaska
The two stocks of Steller sea lions (Eumetopias jubatus) in Alaska include an endangered western stock, recently recovering in parts of its range following decades of decline, and an eastern stock which was removed from the U.S. Endangered Species List in 2013 following increasing numbers since the 1970s. Information on overlapping distributions of eastern and western sea lions is needed for management considerations. We analyzed >30,000 sightings collected from 2000-2014 of 2,385 sea lions that were branded as pups at 10 Alaskan rookeries to examine mesoscale (mostly <500km) spatial distribution, geographic range, and geographic population structure based on natal rookery, sex, and age during breeding and non-breeding seasons. Analyses of summary movement measures (e.g., natal rookery, sex, and age-class differences in spatial distribution and geographic range) indicate wide variation in rookery-specific movement patterns. Correlations between movement measures and population dynamics suggested movement patterns could be a function of density dependence. Animals from larger rookeries, and rookeries with slower population growth and lower survival, had wider dispersion than animals from smaller rookeries, or rookeries with high growth and survival. Sea lions from the largest rookery, Forrester Island, where survival and population trends are lowest, were the most widely distributed. Analysis of geographic population structure indicated that animals born in the eastern Aleutian Islands had the most distinct movements and had little overlap with other western sea lions. Northern Southeast Alaska, within the eastern stock, is the area of greatest overlap between stocks, and is important to western animals, especially those born in Prince William Sound. Detailed knowledge of distribution and movements of western sea lions is useful for defining recovery and population trend analysis regions that better reflect dispersion and population structure and provides valuable information to managers as critical habitat is re-evaluated and the location of the stock boundary reconsidered.
Data from: Natal and breeding philopatry of female Steller sea lions in southeastern Alaska
Information on drivers of dispersal is critical for wildlife conservation but is rare for long-lived marine mammal species with large geographic ranges. We fit multi-state mark-recapture models to resighting data of 369 known-aged Steller sea lion (Eumetopias jubatus) females marked as pups on their natal rookeries in southeastern Alaska from 1994-2005 and monitored from 2001-15. We estimated probabilities of females being first observed parous at their natal site (natal philopatry), and of not moving breeding sites among years (breeding philopatry) at large (> 400 km, all five rookeries in southeastern Alaska) and small (< 4 km, all islands within the largest rookery, Forrester Island Complex, F) spatial scales. At the rookery scale, natal philopatry was moderately high (0.776-0.859) for most rookeries and breeding philopatry was nearly 1, with < 3% of females switching breeding rookeries between years. At more populous islands at F, natal philopatry was 0.500-0.684 versus 0.295-0.437 at less populous islands, and breeding philopatry was 0.919-0.926 versus 0.604-0.858. At both spatial scales, the probability of pupping at a non-natal site increased with population size of, and declined with distance from, the destination site. Natal philopatry of < 1 would increase gene flow, improve population resilience, and promote population recovery after decline in a heterogeneous environment. Very high breeding philopatry suggests that familiarity with neighboring females and knowledge of the breeding site (the topography of pupping sites and nearby foraging locations) may be a critical component to reproductive strategies of sea lions.
On following pages: 12. South American Sea Lion (Otaria byronia); 13. Steller Sea Lion (Eumetopias jubatus); 14. California Sea Lion (Zalophus californianus); 15. Galapagos Sea Lion (Zalophus wollebaeki). in Otariidae
On following pages: 12. South American Sea Lion (Otaria byronia); 13. Steller Sea Lion (Eumetopias jubatus); 14. California Sea Lion (Zalophus californianus); 15. Galapagos Sea Lion (Zalophus wollebaeki).
Age at weaning in Steller sea lions
<p>The duration of offspring care is critical to female fitness and population resilience by allowing flexibility in life history strategies in a variable environment. Yet, for many mammals capable of extended periods of maternal care, estimates of the duration of offspring dependency are not available and the relative importance of flexibility of this trait on fitness and population viability has rarely been examined. We used data from 4,447 Steller sea lions <i>Eumetopias jubatus</i> from the Gulf of Alaska and multistate hidden Markov mark-recapture models to estimate age-specific weaning probabilities. Maternal care beyond age 1 was common: weaning was later for animals from Southeast Alaska (SEAK) and Prince William Sound (PWS, weaning probabilities: 0.538–0.648 / 0.784–0.873 by age 1 / 2) compared to animals born to the west (0.714–0.855 / 0.798–0.938). SEAK/PWS animals were also smaller than those born farther west, suggesting a possible link. Females weaned slightly earlier (+0.080 at age 1 and 2) compared with males in SEAK only. Poor survival for weaned versus unweaned yearlings occurred in southern SEAK (female survival probabilities: 0.609 versus 0.792) and the central Gulf (0.667 versus 0.901), suggesting poor conditions for juveniles in these areas. First-year survival increased with neonatal body mass (NBM) linearly in the Gulf and non-linearly in SEAK. The probability of weaning at age 1 increased linearly with NBM for SEAK animals only. Rookeries where juveniles weaned at earlier ages had lower adult female survival, but age at weaning was unrelated to population trends. Our results suggest the time to weaning may be optimized for different habitats based on long-term average conditions (e.g., prey dynamics), that may also shape body size, with limited short-term plasticity. An apparent trade-off of adult survival in favor of juvenile survival and large offspring size in the endangered Gulf of Alaska population requires further study.</p>
Age at weaning in Steller sea lions
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Data from: Natal and breeding philopatry of female Steller sea lions in southeastern Alaska
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Data from: Survival of adult Steller sea lions in Alaska: senescence, annual variation and covariation with male reproductive success
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Data from: Age specific survival rates of Steller sea lions at rookeries with divergent population trends in the Russian Far East
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Data from: Spatial distribution, movements, and geographic range of Steller sea lions (Eumetopias jubatus) in Alaska
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Data from: Crossing to safety: Dispersal, colonization and mate choice in evolutionarily distinct populations of Steller sea lions, Eumetopias jubatus.
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Novel applications of next generation sequencing tools to assess the health of Steller sea lion (Eumetopias jubatus) populations
GEO Series GSE100883. Eumetopias jubatus. 13 samples. Type: Expression profiling by high throughput sequencing.
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