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.

Pupping-site fidelity among individual Steller sea lions (Eumetopias jubatus) at Chiswell Island, Alaska

2008 ◽  
Vol 86 (8) ◽  
pp. 826-833 ◽  
Author(s):  
P. Parker ◽  
J. T. Harvey ◽  
J. M. Maniscalco ◽  
S. Atkinson
Keyword(s):  
Site Fidelity ◽  
Surf Zone ◽  
Gulf Of Alaska ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Photo Identification ◽  
Pup Survival ◽  
Breeding Seasons

Pupping-site fidelity (defined as pupping within 5.8 m of a previous location in ≥2 years) in Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) was investigated during the breeding seasons from 2001 to 2005 at Chiswell Island, a small rookery in the Gulf of Alaska. Density of females was minimal with 54–80 pups born. Photo-identification of individuals and GPS points, including elevation of the rookery, were used to determine locations of 297 births. Sixty-four percentage (35/55) of the females exhibited pupping-site fidelity, and mean frequency of site fidelity was greater for females that gave birth >3 times. Fifty percentage of the births occurred at 22% of the locations for all years, indicating that multiple births occurred at some locations throughout the breeding season. Competition or aggression among females for specific pupping locations before birth was not observed, and there was no temporal order of pupping locations used, indicating that the rookery was not overcrowded and that many suitable pupping locations existed. Multiparous females gave birth at significantly greater distances from the surf zone than primiparous females. Long-term monitoring of pupping-site fidelity in combination with other measures of maternal care will ultimately determine which factors have the greatest effect on pup survival.

A long-term study reveals multiple reproductive behavior strategies among territorial adult male Steller sea lions (Eumetopias jubatus)

2014 ◽  
Vol 92 (5) ◽  
pp. 405-415 ◽  
Author(s):  
Pamela Parker ◽  
John M. Maniscalco
Keyword(s):  
Reproductive Success ◽  
Gulf Of Alaska ◽  
Lifetime Reproductive Success ◽  
First Year ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Term Study ◽  
Sea Lions ◽  
Long Term Study

We conducted a long-term study to assess how tenure and territorial behaviors influence reproductive success among male Steller sea lions (Eumetopias jubatus (Schreber, 1776)). Copulations by males (n = 44) that maintained territories on a rookery in the Gulf of Alaska from 2001 to 2009 were observed using a remote video system. Approximately half of postpartum females copulated with a male in a different territory from where they gave birth. Nearly two-thirds of territorial males with known tenure were unsuccessful in copulating during their first year. Number of copulations for territorial males increased from acquisition year to year 2 with no change in subsequent years. Cluster analysis of tenure and territorial tactic variables for 15 males with observed lifetime reproductive success was used to describe multiple reproductive strategies. Characteristics of the two most successful strategies were the following: (i) males typically copulated in their first year, retained the same territories for 3–5 years, and occupied centrally located coastal territories where the highest percentage of females gave birth and (ii) males did not copulate until at least their third year and occupied peripheral territories with fewer births for a longer tenure of 7–8 years. Results indicated that lifetime reproductive success was not achieved solely by time on the breeding area; rather, it was achieved from a combination of tenure and territorial tactics.

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.

scholarly journals Steller Sea Lion (Eumetopias jubatus) Response to Non-lethal Hazing at Bonneville Dam

2021 ◽  
Vol 2 ◽  
Author(s):  
Kyle S. Tidwell ◽  
Brett A. Carrothers ◽  
Daniel T. Blumstein ◽  
Zachary A. Schakner
Keyword(s):  
Chinook Salmon ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Sea Lions ◽  
Physical Stimuli ◽  
Multiple Species ◽  
Fisheries Interactions

Protected Steller sea lions (Eumetopias jubatus) aggregate at Bonneville Dam on the Columbia River and prey upon multiple species of endangered salmon ascending the river. Hazing is a non-lethal activity designed to repel sea lions that includes aversive auditory and physical stimuli to deter animals from an area and has been employed with sea lion—fisheries interactions for more than 40 years but sea lion responses to hazing through time is not well-documented. We observed the behavior of Steller sea lions in periods with and without hazing during two spring Chinook salmon passage seasons to evaluate: (1) what effect hazing had on the number of animals present and their foraging behavior, and (2) whether they habituated to hazing. We found that hazing temporarily reduced the number of Steller sea lions, but only when actively hazed. During hazing, Steller sea lions were more likely to move away from hazers on the dam, decreased their foraging, and increased their time investigating the environment. However, these effects were temporary; their behavior returned to initial observation levels once hazing ceased. Furthermore, their responsiveness to hazing declined throughout the season, indicating habituation and raising concern for the application and long-term efficacy of hazing in managing predation on endangered salmon.

scholarly journals Winter movements and long-term dispersal of Steller sea lions in the Glacier Bay region of Southeast Alaska

2018 ◽  
Vol 37 ◽  
pp. 11-24 ◽  
Author(s):  
M Rehberg ◽  
L Jemison ◽  
JN Womble ◽  
G O’Corry-Crowe
Keyword(s):  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Glacier Bay ◽  
Sea Lions
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