Entanglement in marine debris and fishing gear is increasingly recognized as a serious source of human-caused mortality for pinniped population world-wide and has been shown to contribute to Steller sea lion injury and mortality. As such, our primary goal in testing these location-only satellite flipper tags was to track post-entanglement response survival of Steller sea lions in Southeast Alaska, USA. The minimum data set necessary to determine post-release survival included: (a) location data sufficient to demonstrate movement indicating the tag was still attached to a live sea lion, and (b) tag endurance sufficient to track a disentangled sea lion beyond the molt (most entanglement response occurs during the summer in conjunction with other Steller sea lion research so tags glued to the pelage typically only last two to three months before falling off). For this study, we tested Wildlife Computers (Redmond, Washington, USA) Smart Position and Temperature (SPOT) 6 Model 371B inline satellite tags (SPOT 6 tags) on Steller sea lions. This first application of attaching SPOT 6 satellite flipper tags on otariids was a success with tags transmitting up to 2.05 years. Overall, the benefits of these tags outweighed their limitations and for the first time, allowed us to track Steller sea lions beyond the annual molt.

Abstract 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 (Eumetopias jubatus) in Southeast Alaska varied regionally (with high population growth and survival in the north vs. 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 1006 Steller sea lion females marked as pups at ~3 weeks of age from 1994 to 1995 and from 2001 to 2005 and resighted from 2002 to 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 vs. 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 could 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.

The North Pacific marine heatwave of 2014–2016 (PMH), one of the most geographically-extensive and severe marine heatwaves on record, resulted in widespread and persistent perturbation of the Gulf of Alaska and California Current ecosystems. Negative effects of the PMH on marine mammals have been observed, but are not yet well understood. The endangered Steller sea lion Eumetopias jubatus is an important top predator in the Gulf of Alaska that is also particularly vulnerable to sudden or severe ecosystem shifts. We examined survival of 4,178 known-aged Steller sea lions marked from 2000 to 2016 from Kodiak Island through Southeast Alaska, using mark-recapture models and 12,811 resightings collected from 2001 to 2021. Survival of adult females aged 3–15 was reduced -0.05 to -0.23 during the PMH in the areas east, but not west, of Cook Inlet. Survival of Kodiak females was unaffected by the PMH, but survival of Sugarloaf females aged 5–8 was reduced -0.13 from summer 2015 to summer 2016. Lowest survival in Southeast Alaska occurred from summer 2016 to summer 2017, but was also reduced from summer 2014 to summer 2016. Reduced survival continued post-PMH in Kenai Peninsula/Prince William Sound, but not in Southeast Alaska. Survival of adult males was insensitive to the PMH, except in Southeast Alaska where male survival was reduced -0.25 from summer 2016 to summer 2017. Prolonged or intermittent high adult female mortality may reduce population growth and initiate regional declines. Survival response of Steller sea lions to the PMH varied regionally despite similar patterns of ocean warming throughout our study area, suggesting areas east versus west of Cook Inlet were affected differently by the PMH, perhaps due to habitat and oceanographic differences.

Most research that has been done regarding Steller sea lions (SSLs; Eumetopias jubatus) has been during the breeding season. Adult SSLs are known to have high among-year breeding-season site fidelity, typically with movement away from breeding-season locations during non-breeding seasons. Using non-breeding-season sighting data of permanently marked SSLs from four areas in Alaska and broad-scale breeding-season sightings, we estimated among-year non-breeding-season site fidelity (i.e., the probability a SSL moves from its breeding-season location to a specific non-breeding-season area). Some SSLs, especially females, have high site fidelity to non-breeding-season areas; fidelity is markedly lower for males. We found no evidence that site fidelity varied among natal rookeries, but our sample sizes were relatively small, possibly limiting our ability to determine such effects. With our estimates of non-breeding-season site fidelity, coupled with previously demonstrated breeding-season site fidelity, we concluded that SSLs should be considered partial migrants (i.e., migratory behavior exhibited by only some individuals in a population) with at least some individual SSLs, particularly females, exhibiting migratory behavior.

Steller sea lions (Eumetopias jubatus) are composed of two genetically distinct metapopulations (an increasing "eastern" and a reduced and endangered "western" population, or stock for management purposes in U.S. waters) that are only recently mixing at new rookeries in northern Southeast Alaska, east of the current stock boundary. We used mark-recapture models and 18 years of resighting data of over 3,500 individuals marked at the new rookeries and at neighboring long-established rookeries in both populations to examine morphology, survival, and movement patterns of pups born at new rookeries based on whether they had mitochondrial DNA haplotypes from the western or eastern population (mtW or mtE); examine survival effects of dispersal to the Eastern Stock region for animals born in the Western Stock region; and estimate minimum proportions of animals with western genetic material in regions within Southeast Alaska. Pups born at new rookeries with mtW had similar mass, but reduced body condition and first-year survival (approximately -10%) compared to pups with mtE. mtE pups ranged more widely than mtW pups, including more to the sheltered waters of Southeast Alaska's Inside Passage. Fitness benefits for western-born females that dispersed to Southeast Alaska were observed as higher female survival (+0.127, +0.099, and +0.032 at ages 1, 2, and 3+) and higher survival of their female offspring to breeding age (+0.15) compared to females that remained west of the boundary. We estimated that a minimum of 38% and 13% of animals in the North Outer Coast-Glacier Bay and Lynn Canal-Frederick Sound regions in Southeast Alaska, respectively, carry genetic information unique to the western population. Despite fitness benefits to western females that dispersed east, asymmetric dispersal costs or other genetic or maternal effects may limit the growth of the western genetic lineage at the new rookeries, and these factors require further study.

[This corrects the article DOI: 10.1371/journal.pone.0176840.].

Population dynamics of long-lived vertebrates depend critically on adult survival, yet factors affecting survival and covariation between survival and other vital rates in adults remain poorly examined for many taxonomic groups of long-lived mammals (e.g. actuarial senescence has been examined for only 9 of 34 extant pinniped species using longitudinal data). We used mark–recapture models and data from 2795 Steller sea lion (Eumetopias jubatus) pups individually marked at four of five rookeries in southeastern Alaska (SEAK) and resighted for 21 years to examine senescence, annual variability and covariation among life-history traits in this long-lived, sexually dimorphic pinniped. Sexes differed in age of onset (approx. 16–17 and approx. 8–9 years for females and males, respectively), but not rate (−0.047 and −0.046/year of age for females and males) of senescence. Survival of adult males from northern SEAK had greatest annual variability (approx. ±0.30 among years), whereas survival of adult females ranged approximately ±0.10 annually. Positive covariation between male survival and reproductive success was observed. Survival of territorial males was 0.20 higher than that of non-territorial males, resulting in the majority of males alive at oldest ages being territorial.

Steller sea lions Eumetopias jubatus in the Glacier Bay region of northern Southeast Alaska experience greater survival and more rapid population growth than sea lions elsewhere in this region. To better understand demographics of sea lions in the region, and to describe the origins and behavior of sea lions and relate these descriptions to previous studies, we studied genetic origins, residency, foraging range, diving behavior, and dispersal of immature sea lions (≤24 mo of age) captured in Glacier Bay. Fifty-two percent of individuals had maternal origins in the distant (550 km) endangered western population rather than in the local recovered eastern population. During winter, 5 mo old pups, dependent on their dams for nutrition, remained within Glacier Bay, diving to shallow depths (≤108 m) mainly during daylight, whereas older (17 mo old) juveniles ranged more widely to areas of known seasonal prey aggregations, performing deep (≥241 m) nocturnal dives. Both pups and juveniles remained within the northern portion of Southeast Alaska, in contrast to farther-ranging pup and juvenile sea lions captured elsewhere in Southeast Alaska. Over the long term, females from Glacier Bay remained within this northern area through maturity and were sighted breeding in this area only. Restricted ranging patterns and natal and breeding philopatry by Steller sea lions of both eastern and western distinct population segment origin in the Glacier Bay region reveal that optimal foraging and breeding conditions likely prevail and help explain the recent colonization, increased survival, and rapid population growth of this species in the region.

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.

We estimated survival probabilities for Steller sea lion ( Eumetopias jubatus ) pups from 3 wk to 6 wk old and from 6 wk to 1 yr at three rookeries in southeastern Alaska. We also investigated the effect of mass, body condition, health variables, and the genetic origin on 3–6 wk survival. Survival differed substantially among rookeries and between sexes, with survival lowest at Hazy Islands, intermediate at White Sisters, and highest at Graves Rocks and survival lower for males than females. Body mass, body condition, and hematocrit were positively related to survival and blood %H 2 O and haptoglobin level (for females; no relationship for males) were negatively related to survival. Taking predictor variables collectively, sea lion pups at Hazy Islands, which had the lowest survival probability, had the lowest mass, hematocrit, and hemoglobin, and had high levels of blood %H 2 O, and hookworm infection. Values from Graves Rocks, which had the highest survival, were the opposite of those from Hazy Island ( e.g ., high mass, body condition, hematocrit, and hemoglobin), while those from White Sisters (intermediate survival) had varying means ( e.g ., high hematocrit and hemoglobin and low hookworms, but also low body condition); these patterns suggest that physiological factors potentially underlie rookery differences in survival.

Marine Mammal ScienceVolume 32, Issue 2 p. 777-785 Note Age-specific variation in timing of parturition in Steller sea lions at Forrester Island Complex, Alaska Kelly K. Hastings, Corresponding Author Kelly K. Hastings Alaska Department of Fish and Game, Division of Wildlife Conservation, 1255 West 8th Street, Juneau, Alaska, 99811 U.S.A.Corresponding author (e-mail: [email protected]).Search for more papers by this authorLauri A. Jemison, Lauri A. Jemison Alaska Department of Fish and Game, Division of Wildlife Conservation, 1255 West 8th Street, Juneau, Alaska, 99811 U.S.A.Search for more papers by this author Kelly K. Hastings, Corresponding Author Kelly K. Hastings Alaska Department of Fish and Game, Division of Wildlife Conservation, 1255 West 8th Street, Juneau, Alaska, 99811 U.S.A.Corresponding author (e-mail: [email protected]).Search for more papers by this authorLauri A. Jemison, Lauri A. Jemison Alaska Department of Fish and Game, Division of Wildlife Conservation, 1255 West 8th Street, Juneau, Alaska, 99811 U.S.A.Search for more papers by this author First published: 26 November 2015 https://doi.org/10.1111/mms.12288Citations: 7Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Literature Cited Anderson, S. S., and M. A. Fedak. 1987. Grey seal, Halichoerus grypus, energetics: Females invest more in male offspring. 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Tidewater glacial fjords provide important habitat for breeding harbor seals (Phoca vitulina) that rest, give birth, and nurse pups on icebergs.These fjords also attract tourist vessels that potentially disturb seals.In May and June during 2001-2006, we documented seal abundance, pupping phenology, and seal-vessel interactions in Tracy Arm, a glacial fjord in southeastern Alaska.We used randomized observations to determine the frequency at which seals entered the water in the presence and absence of vessels, and we estimated the reaction distances of seals to approaching vessels.Mean daily vessel counts varied from 10.2 (2001) to 2.0 (2006) (range: 1-33).Tour and power vessels were the most common types of vessels, but seals were most sensitive to cruise ships and kayaks.The odds of a seal entering the water were higher when vessels were present (>2 times) or within 100 m (3.7 times), and when a pup was present (1.3 times).The baseline, undisturbed, rate of seals entering the water was 0.06 (95% CI: 0.05-0.08)per 10 min.Seal births occurred during 30 May-25 June and peaked (4-8 per day) during 7-13 June.The maximum pup count (408) was observed on 24 June.Harbor seal fitness in Tracy Arm may be reduced by vessel disturbances during breeding and pupping.

Genetic studies and differing population trends support the separation of Steller sea lions (Eumetopias jubatus) into a western distinct population segment (WDPS) and an eastern DPS (EDPS) with the dividing line between populations at 144° W. Despite little exchange for thousands of years, the gap between the breeding ranges narrowed during the past 15-30 years with the formation of new rookeries near the DPS boundary. We analyzed >22,000 sightings of 4,172 sea lions branded as pups in each DPS from 2000-2010 to estimate probabilities of a sea lion born in one DPS being seen within the range of the other DPS (either 'West' or 'East'). Males from both populations regularly traveled across the DPS boundary; probabilities were highest at ages 2-5 and for males born in Prince William Sound and southern Southeast Alaska. The probability of WDPS females being in the East at age 5 was 0.067 but 0 for EDPS females which rarely traveled to the West. Prince William Sound-born females had high probabilities of being in the East during breeding and non-breeding seasons. We present strong evidence that WDPS females have permanently emigrated to the East, reproducing at two 'mixing zone' rookeries. We documented breeding bulls that traveled >6,500 km round trip from their natal rookery in southern Alaska to the northern Bering Sea and central Aleutian Islands and back within one year. WDPS animals began moving East in the 1990s, following steep population declines in the central Gulf of Alaska. Results of our study, and others documenting high survival and rapid population growth in northern Southeast Alaska suggest that conditions in this mixing zone region have been optimal for sea lions. It is unclear whether eastward movement across the DPS boundary is due to less-optimal conditions in the West or a reflection of favorable conditions in the East.

We estimated trends in numbers of Steller sea lions in the Glacier Bay region of the eastern population from the 1970s to 2009. We documented the colonization of several new haul-outs and the transition of one haul-out (Graves Rocks) to a rookery, assessed seasonal patterns in distribution, and compared counts from different observation platforms. Sea lions increased in the region by 8.2%/yr (95% CI = 6.4%-10.0%), with the most growth at South Marble Island in Glacier Bay (16.6%/yr, 1991-2009) and rapid growth in Cross Sound. Seasonal patterns in the distribution of sea lions were likely influenced by new breeding opportunities and the seasonal availability of prey. Factors that likely contributed to the exceptional growth include availability of new habitat following deglaciation, immigration, redistribution, decreases in mortality, and ecosystem-level changes. The rapid increase in sea lion numbers in this region is of particular interest in light of dramatic declines in the western population and evidence that Steller sea lions from both the eastern and western populations colonized the Graves Rocks rookery. The colonization and rookery development in this dynamic area may signal the reversal of the reproductive isolation of the two populations.

Information concerning mechanistic processes underlying changes in vital rates and ultimately population growth rate is required to monitor impacts of environmental change on wildlife. We estimated age-specific survival and examined factors influencing survival for a threatened population of Steller sea lions (Eumetopias jubatus) in southeastern Alaska. We used mark-recapture models and data from 1,995 individuals marked at approximately one month of age at four of five rookeries in southeastern Alaska, and resighted from Oregon to the Bering Sea. Average annual survival probability for females was 0.64 for pups and 0.77 for yearlings, and increased from 0.91 to 0.96 from age 3–7 yrs. Annual survival probability of males averaged 0.60 for pups and 0.88 by 7 yrs, resulting in probability of survival to age 7, 33% lower for males compared to females. Pups from northern southeastern Alaska (including an area of low summer population size but rapid growth) were twice as likely to survive to age 7 compared to pups from southern rookeries (including a large, historical, stable rookery). Effects of early conditions on future fitness were observed as (1) environmental conditions in the birth year equally affected first- and second-year survival, and (2) effects of body mass at approximately one month of age were still apparent at 7 yrs. Survival from 0–2 yrs varied among five cohorts by a maximum absolute difference of 0.12. We observed survival costs for long-distance dispersal for males, particularly as juveniles. However, survival was higher for non-pups that dispersed to northern southeastern Alaska, suggesting that moving to an area with greater productivity, greater safety, or lower population size may alleviate a poor start and provide a mechanism for spatial structure for sea lion populations.

Entanglement in marine debris is a contributing factor in Steller sea lion (SSL; Eumetopias jubatus) injury and mortality. We quantified SSL entanglement by debris type, sex and age class, entanglement incidence, and estimated population level effects. Surveys of SSL haul-outs were conducted from 2000–2007 in Southeast Alaska and northern British Columbia. We recorded 386 individuals of all age classes as being either entangled in marine debris or having ingested fishing gear. Packing bands were the most common neck entangling material (54%), followed by rubber bands (30%), net (7%), rope (7%), and monofilament line (2%). Ingested fishing gear included salmon fishery flashers (lures: 80%), longline gear (12%), hook and line (4%), spinners/spoons (2%), and bait hooks (2%). Entanglement incidence was 0.26% (SD = 0.0064, n = 69 sites). “Lose the Loop!” Simple procedures such as cutting entangling loops of synthetic material and eliminating the use of packing bands can prevent entanglements.

We are using demographics, scat analysis, and genetic measurements of Steller sea lions (SSLs)to understand the factors affecting population status throughout Alaska. Steller sea lions are listed as threatened throughout Southeast Alaska including Glacier Bay National Park where they frequent at least five terrestrial sites, including a recently established rookery on Graves Rock. Breeding season counts in GBNP increased at ~6 percent/yr between 1989 and 2002. Brand resighting during 2003 revealed 16 western stock SSLs seen within the park. Survival to two months of age was 90 percent. Fifty pups were branded at Graves Rock in 2002. It is necessary to mark more animals to estimate annual survival rates of juveniles and adults. Sandlance and pollock were top prey items at Graves Rock and South Marble Island. Mitochondrial DNA analysis indicates that the Graves Rock rookery was established in part by females from the western sea lion stock (west of 144° W longitude). Figure 1. Branded Steller sea lion on a haul out in Southeast Alaska. Each marked sea lion has a unique letter-number combination that identifies the individual. The preceding “F” on this individual signifies its birth place as the Forrester Island complex near Prince of Wales Island, Alaska. Tom Gelatt and others 1 5 1 Alaska Dept. of Fish and Game, 525 W. 67 Ave, Anchorage, AK 99518 2 Marine Mammal Research Unit, Fisheries Center, University of British Columbia, Hut B3, Room 18, 6248 Biological Science Road, Vancouver BC,