Availability to Steller sea lions (Eumetopias jubatus) of a seasonal prey resource: a prespawning aggregation of eulachon (Thaleichthys pacificus)

2004 ◽  
Vol 61 (8) ◽  
pp. 1475-1484 ◽  
Author(s):  
Michael F Sigler ◽  
Jamie N Womble ◽  
Johanna J Vollenweider
Keyword(s):  
North Pacific Ocean ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Southeast Alaska ◽  
Sea Lions ◽  
The North ◽  
Large Numbers ◽  
Spawning Run ◽  
The North Pacific

The availability of seasonally abundant energy-rich prey can be a significant factor for the survival and reproductive success of predator populations. Large numbers of Steller sea lions (Eumetopias jubatus) were attracted to a prespawning aggregation of eulachon (Thaleichthys pacificus) in Berners Bay in southeast Alaska during April–May in 2002 and 2003. Sea lion abundance increased as eulachon gathered in Berners Bay, peaked as eulachon abundance peaked, and decreased as the eulachon moved up-river. As sea lion abundance increased in Berners Bay, sea lion abundance decreased at Benjamin Island, a sea lion haulout located 22 km away. The eulachon provided an abundant, energy-rich, predictable prey source for the Steller sea lions: (i) eulachon energy density was 9.70 ± 0.24 kJ·g–1, much higher than that of any forage species reported in the North Pacific Ocean except northern lampfish (Stenobrachius leucopsarus); (ii) a large surplus of prey was available per sea lion while the eulachon aggregation was present; and (iii) the spawning run usually begins between late April and early May. The eulachon pulse may be critical to Steller sea lions during a period of high energetic demands.

Ecosystem models show combined effects of fishing, predation, competition, and ocean productivity on Steller sea lions (Eumetopias jubatus) in Alaska

2006 ◽  
Vol 63 (11) ◽  
pp. 2495-2517 ◽  
Author(s):  
Sylvie Guénette ◽  
Sheila JJ Heymans ◽  
Villy Christensen ◽  
Andrew W Trites
Keyword(s):  
Time Series Data ◽  
Series Data ◽  
Ecosystem Structure ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Ecosystem Models ◽  
Sea Lion ◽  
Southeast Alaska ◽  
Sea Lions ◽  
Ocean Productivity

Steller sea lions (Eumetopias jubatus) increased in the eastern portion of their range while declining in the Gulf of Alaska and Aleutian Islands from the late 1970s to late 1990s. We constructed ecosystem models of the central and western Aleutians and of southeast Alaska to simultaneously evaluate four hypotheses explaining sea lion dynamics: killer whale (Orcinus orca) predation, ocean productivity, fisheries, and competition with other species. Comparisons of model predictions with historical time series data indicate that all four factors likely contributed to the trends observed in sea lion numbers in both ecosystems. Changes in ocean productivity conveyed by the Pacific Decadal Oscillation influenced the abundance trajectory of several species. Fishing could have affected the ecosystem structure by influencing the abundance of Atka mackerel (Pleurogrammus monopterygius) in the Aleutians and Pacific herring (Clupea pallasii) in southeast Alaska. Pacific halibut (Hippoglossus stenolepis) in the Aleutians and arrowtooth flounder (Atheresthes stomias) in southeast Alaska appear to impede sea lion population growth through competitive interactions. Predation by killer whales was important when sea lions were less abundant in the 1990s in the Aleutians and in the 1960s in Southeast Alaska, but appear to have little effect when sea lion numbers were high.

scholarly journals The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9709
Author(s):  
Nahoko Tsuzuku ◽  
Naoki Kohno
Keyword(s):  
North Pacific ◽  
Japan Sea ◽  
Early Pleistocene ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Sea Lions ◽  
The North ◽  
Fur Seals ◽  
The North Pacific

The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 mandibles of fur seals and sea lions with GKZ-N 00001. As results of bivariate analyses and PCA based on 39 measurements for external morphologies with internal structures by CT scan data, there is almost no difference between GKZ-N 00001 and extant male individuals of E. jubatus. In this regard, GKZ-N 00001 is identified specifically as the Steller sea lion E. jubatus. Consequently, it is recognized as the oldest Steller sea lion in the North Pacific. About 0.8 Ma, the distribution of the Steller sea lion had been already established at least in the Japan Sea side of the western North Pacific.

Diet composition of Steller sea lions (Eumetopias jubatus) in Frederick Sound, southeast Alaska: a comparison of quantification methods using scats to describe temporal and spatial variabilities

2015 ◽  
Vol 93 (5) ◽  
pp. 361-376 ◽  
Author(s):  
D.J. Tollit ◽  
M.A. Wong ◽  
A.W. Trites
Keyword(s):  
Pacific Salmon ◽  
Biomass Energy ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Merluccius Productus ◽  
Sea Lions ◽  
Sampling Protocols ◽  
Dietary Indices

We compared eight dietary indices used to describe the diet of Steller sea lions (Eumetopias jubatus (Schreber, 1776)) from 2001 to 2004 in Frederick Sound, southeast Alaska. Remains (n = 9666 items) from 59+ species categories were identified from 1684 fecal samples (scats) from 14 collection periods. The most frequently occurring prey were walleye pollock (Theragra chalcogramma (Pallas, 1814) = Gadus chalcogrammus Pallas, 1814; 95%), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; 30%), Pacific hake (Merluccius productus (Ayres, 1855); 29%), and arrowtooth flounder (Atheresthes stomias (Jordan and Gilbert, 1880) = Reinhardtius stomias (Jordan and Gilbert, 1880); 21%). These species, along with Pacific salmon (genus Oncorhynchus Suckley, 1861) and skate (genus Raja L., 1758), accounted for 80%–90% of the reconstructed biomass and energy contribution, with pollock contributing 37%–60%. Overall, 80% of fish were 14–42 cm long and mainly pelagic, though 40% of scats contained benthic-associated prey. Steller sea lions switched from adult pollock to strong cohorts of juvenile pollock, and took advantage of spawning concentrations of salmon in autumn and herring in late spring and summer, as well as a climate-driven increase in hake availability. Observed temporal and site differences in diet confirm the need for robust long-term scat sampling protocols. All major indices similarly tracked key temporal changes, despite differences in occurrence and biomass-energy-based diet estimates linked to prey size and energy-density effects and the application of correction factors.

scholarly journals Demographic consequences and characteristics of recent population mixing and colonization in Steller sea lions, Eumetopias jubatus

2019 ◽  
Vol 101 (1) ◽  
pp. 107-120
Author(s):  
Kelly K Hastings ◽  
Michael J Rehberg ◽  
Gregory M O’corry-Crowe ◽  
Grey W Pendleton ◽  
Lauri A Jemison ◽  
...  
Keyword(s):  
Genetic Material ◽  
Genetic Lineage ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Population Mixing ◽  
Western Population ◽  
Sea Lions ◽  
Asymmetric Dispersal ◽  
Fitness Benefits

Abstract 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.

Stable carbon and nitrogen isotope values in teeth of Steller sea lions: age of weaning and the impact of the 1975–1976 regime shift in the North Pacific Ocean

2008 ◽  
Vol 86 (1) ◽  
pp. 33-44 ◽  
Author(s):  
A. E. York ◽  
J. R. Thomason ◽  
E. H. Sinclair ◽  
K. A. Hobson
Keyword(s):  
Regime Shift ◽  
North Pacific Ocean ◽  
Large Population ◽  
Nitrogen Isotope ◽  
Steller Sea Lions ◽  
Linear Discriminant ◽  
Sea Lions ◽  
The North ◽  
Tooth Width ◽  
The Impact

We measured δ15N and δ13C values and tooth width from the first 4 years’ dentinal growth layer groups (GLGs) in the teeth of 113 female Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) born between 1960 and 1983, a period that included a large population decrease and a climate regime shift. A linear discriminant analysis on the δ13C and δ15N values estimated 60% of Steller sea lions were weaned in their 1st year, 30% in their 2nd year, and 8% in their 3rd year. GLG-1 was wider in “weaned” animals than those still “nursing” in their 2nd year, suggesting that faster growing pups weaned earlier. Except during the regime shift, the average age at weaning increased and the size of GLG-1 in weaned animals decreased. We suggest that during the regime shift a greater proportion of pups which survived (to have their teeth sampled for this study) grew faster and were weaned by the end of their 1st year. We hypothesize that the long-term weaning age increase and growth rate decrease are consistent with a change in relative mortality of weaned pups and those that continued to nurse, possibly caused by a reduction in available resources, characterized as a switch from a “live-fast” to a “live-slow” life history.

Pricetrema phocae and Pricetrema eumetopii spp.n. (Trematoda: Heterophyidae) from pinnipeds in the North Pacific

1978 ◽  
Vol 56 (3) ◽  
pp. 382-385
Author(s):  
Larry M. Shults
Keyword(s):  
North Pacific ◽  
Harbor Seal ◽  
Phoca Vitulina ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
The North ◽  
Phoca Vitulina Richardsi ◽  
The North Pacific

Pricetrema phocae and Pricetrema eumetopii spp.n. are described from the harbor seal, Phoca vitulina richardsi (Gray), and Steller sea lion, Eumetopias jubatus (Schreber), respectively.

Milk fatty acid composition of perinatal and foraging Steller sea lions (Eumetopias jubatus): examination from pup stomachs

2018 ◽  
Vol 96 (2) ◽  
pp. 153-162 ◽  
Author(s):  
C.N. Miller ◽  
L.K. Polasek ◽  
A.C.M. Oliveira ◽  
C.J. Frost ◽  
J.M. Maniscalco
Keyword(s):  
Fatty Acids ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Acid Composition ◽  
Steller Sea Lion ◽  
Milk Fatty Acid ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Sea Lions

To investigate the milk fatty acid composition of female Steller sea lions (Eumetopias jubatus (Schreber, 1776)) between and within maternal states (i.e., perinatal or foraging), milk samples were collected in 2010 and 2011 via gastric intubation from Steller sea lion pups on a small rookery in the central Gulf of Alaska. Maternal states of lactating females were determined upon reuniting with their sampled pups via remotely operated video cameras on the rookery. Milk fatty acid composition between Steller sea lion maternal states was significantly different, and thus can be utilized to distinguish between perinatal and foraging Steller sea lions of the same geographic region in the absence of direct observation. However, milk fatty acid composition remained relatively constant within perinatal Steller sea lions, suggesting steady mobilization of fatty acids from blubber to milk, and within foraging Steller sea lions, implying females forage on similar prey species within several days after their perinatal period. Differences in milk fatty acid composition between maternal states, including differences in the relative percentages of polyunsaturated fatty acids, may have important implications for growth and development of offspring.

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

2019 ◽  
Vol 97 (12) ◽  
pp. 1137-1155 ◽  
Author(s):  
L. Fritz ◽  
B. Brost ◽  
E. Laman ◽  
K. Luxa ◽  
K. Sweeney ◽  
...  
Keyword(s):  
Energy Density ◽  
Population Trend ◽  
Population Trends ◽  
Aleutian Islands ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Diet Diversity ◽  
Sea Lions ◽  
Using Data

Prey diversity and energy density have been linked to each other and to population trends in many studies of bird and mammal diets. We re-examined these relationships in Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using data collected from the Aleutian Islands, where there has been a strong longitudinal gradient in population trend. Diet diversity and energy density metrics were similar in the western Aleutians, where sea lion counts declined consistently, and in the easternmost Aleutian area, where population trends improved significantly. We compared traditional deterministic diet diversity metrics with diversity scores based on an occupancy model that accounts for differences in sample size and uncertainty in prey group detection. This analysis indicated that there was no significant change in diet diversity over the 23-year study period or any significant differences across the Aleutian Islands. These results are consistent with prey abundance data from nine groundfish bottom trawl surveys conducted over the same period. While diet studies detail what Steller sea lions eat and provide an estimate of their energy intake, they provide only limited information on the energy expended to obtain their food or the consequences of their diet and foraging ecology on individual or population fitness.

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