Foraging behavior of adult female Steller sea lions during the breeding season in Southeast Alaska

2009 ◽  
Vol 25 (3) ◽  
pp. 588-604 ◽  
Author(s):  
M. J. Rehberg ◽  
R. D. Andrews ◽  
U. G. Swain ◽  
D. G. Calkins
Keyword(s):  
Foraging Behavior ◽  
Breeding Season ◽  
Adult Female ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Sea Lions

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 Mixing it up in Alaska: Habitat use of adult female Steller sea lions reveals a variety of foraging strategies

Ecosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Michelle E. Lander ◽  
Brian S. Fadely ◽  
Thomas S. Gelatt ◽  
Jeremy T. Sterling ◽  
Devin S. Johnson ◽  
...  
Keyword(s):  
Habitat Use ◽  
Adult Female ◽  
Foraging Strategies ◽  
Steller Sea Lions ◽  
Sea Lions

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.

Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions

2007 ◽  
Vol 85 (2) ◽  
pp. 190-200 ◽  
Author(s):  
L.D. Rea ◽  
D.A.S. Rosen ◽  
A.W. Trites
Keyword(s):  
Mass Loss ◽  
Body Mass ◽  
Breeding Season ◽  
Lower Percentage ◽  
Metabolic Adaptation ◽  
Body Lipid ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Nonbreeding Season ◽  
Total Body

Nine captive Steller sea lions ( Eumetopias jubatus (Schreber, 1776), 1.75–6 years of age) were fasted for 7–14 d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8% ± 0.2%·d–1) than in subadults (1.2% ± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5% ± 0.3%·d–1; subadults, 1.7% ± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3 d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.

Foraging behavior of adult female and young-of-the-year Steller sea lions in Alaskan waters

1997 ◽  
Vol 75 (5) ◽  
pp. 776-786 ◽  
Author(s):  
Richard L. Merrick ◽  
Thomas R. Loughlin
Keyword(s):  
Adult Female ◽  
Prey Availability ◽  
Gulf Of Alaska ◽  
First Year ◽  
Home Ranges ◽  
Steller Sea Lions ◽  
Foraging Effort ◽  
Sea Lions ◽  
Adult Females ◽  
Young Of The Year

One explanation for recent declines in the Alaskan Steller sea lion (Eumetopias jubatus) population is that the availability of preferred prey has changed. Part of our evaluation of this hypothesis involved the use of conventional radio and satellite-linked time–depth recorder transmitters to compare summer and winter foraging of adult female and young-of-the-year Steller sea lions in Alaska waters. Foraging effort was not significantly different seasonally for postpartum adult females, though females with dependent young in winter may increase their foraging effort. In winter, all adult females made longer trips over larger home ranges and dove deeper. Young sea lions exerted less foraging effort, had the shallowest and briefest dives, and had home ranges intermediate in size to the two groups of adult females. Their foraging ability appears to develop throughout the first year. We conclude that adult female sea lions can exploit prey throughout the Gulf of Alaska and Bering Sea, and are constrained only by their reproductive status and seasonal changes in prey availability. Young sea lions' diving is more limited because their physiological and behavioral development constrains them from diving like an adult. Perhaps most important, dives remain shallow through the first year. Consequently, young sea lions could be more easily food-limited by changes in prey distribution.

Low prey abundance leads to less efficient foraging behavior in Steller sea lions

2015 ◽  
Vol 470 ◽  
pp. 70-77 ◽  
Author(s):  
Elizabeth T. Goundie ◽  
David A.S. Rosen ◽  
Andrew W. Trites
Keyword(s):  
Foraging Behavior ◽  
Prey Abundance ◽  
Steller Sea Lions ◽  
Sea Lions

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.

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.

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