Demographic independence along ecosystem boundaries in Steller sea lions revealed by mtDNA analysis: implications for management of an endangered species

2006 ◽  
Vol 84 (12) ◽  
pp. 1796-1809 ◽  
Author(s):  
G. O’Corry-Crowe ◽  
B.L. Taylor ◽  
T. Gelatt ◽  
T.R. Loughlin ◽  
J. Bickham ◽  
...  
Keyword(s):  
Foraging Ecology ◽  
Gulf Of Alaska ◽  
Ocean Basin ◽  
Population Trends ◽  
Population Declines ◽  
Steller Sea Lions ◽  
Dispersal Patterns ◽  
Sea Lions ◽  
Ecosystem Boundaries ◽  
Haplotypic Diversity

Previous genetic studies indicate Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) comprise three phylogeographically distinct populations. However, differences in population trends and ecology and the limited extent of recorded dispersal suggest structure may be present at smaller scales. We examined sequence variation within a longer segment (531 bp) of the mtDNA control region in greater numbers (n = 1654) of sea lions from across Alaska than earlier investigations to investigate fine-scale dispersal patterns in Steller sea lions. We detected high levels of haplotypic diversity (h = 0.934) and confirmed phylogeographic differentiation between southeastern and western Alaska (Φst = 0.23, P < 0.0001), but also found significant differentiation at regional and local scales. Rookeries in the Gulf of Alaska, eastern Bering Sea, and eastern Aleutians were distinct from rookeries in the central and western Aleutians (Fst = 0.021, P < 0.0001; Φst = 0.017, P < 0.0001). The location of this split coincides with an oceanographic divergence between continental shelf and ocean basin waters and with differences in sea lion foraging ecology and population trends. A number of rookeries were also significantly differentiated from nearby rookeries (Fst = 0.02–0.025, P < 0.05), signifying substantial female-mediated philopatry, in some cases, at local scales. These findings have important implications for understanding the ecology of Steller sea lions in relation to marine ecosystems and the causes of population declines, and they provide guidance for management, including the identification of management stocks.

Comparing total body lipid content of young-of-the-year Steller sea lions among regions of contrasting population trends

2016 ◽  
Vol 32 (4) ◽  
pp. 1200-1218 ◽  
Author(s):  
Lorrie D. Rea ◽  
Brian S. Fadely ◽  
Sean D. Farley ◽  
Julie P. Avery ◽  
Wendy S. Dunlap-Harding ◽  
...  
Keyword(s):  
Lipid Content ◽  
Population Trends ◽  
Body Lipid ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Young Of The Year ◽  
Total Body

scholarly journals Age Specific Survival Rates of Steller Sea Lions at Rookeries with Divergent Population Trends in the Russian Far East

PLoS ONE ◽  
2015 ◽  
Vol 10 (5) ◽  
pp. e0127292 ◽  
Author(s):  
Alexey V. Altukhov ◽  
Russel D. Andrews ◽  
Donald G. Calkins ◽  
Thomas S. Gelatt ◽  
Eliezer D. Gurarie ◽  
...  
Keyword(s):  
Russian Far East ◽  
Survival Rates ◽  
Far East ◽  
Population Trends ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
The Russian Far East

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.

REDUCED BODY SIZE OF FEMALE STELLER SEA LIONS FROM A DECLINING POPULATION IN THE GULF OF ALASKA

1998 ◽  
Vol 14 (2) ◽  
pp. 232-244 ◽  
Author(s):  
Donald G. Calkins ◽  
Earl F. Becker ◽  
Kenneth W. Pitcher
Keyword(s):  
Body Size ◽  
Gulf Of Alaska ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Reduced Body

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.

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.

Pollock and the decline of Steller sea lions: testing the junk-food hypothesis

2000 ◽  
Vol 78 (7) ◽  
pp. 1243-1250 ◽  
Author(s):  
David AS Rosen ◽  
Andrew W Trites
Keyword(s):  
Body Mass ◽  
Energy Content ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Net Energy ◽  
Junk Food ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Gross Energy

The decline of Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska and the Aleutian Islands may be the result of them eating too much pollock (a gadid fish) instead of a more balanced and diverse diet containing fattier fishes, such as herring or sandlance. We sought to test this junk-food hypothesis by feeding six captive Steller sea lions (ages 0.9-4.5 years) only pollock or herring. All sea lions gained mass while eating herring. However, eating only pollock for short periods (11-23 d) caused the study animals to lose an average of 6.5% of their initial body mass (0.6 kg/d) over an average feeding trial of 16 d (initial mass averaged 125 kg). The animals were allowed to eat as much pollock as they wanted but did not increase their food intake to compensate for the low energy they were receiving. The sea lions showed progressive metabolic depression while losing body mass on a pollock-only diet. The loss of body mass while eating pollock was due to the lower gross energy content of pollock versus herring, the higher cost of digesting pollock, and the increased energy loss from digesting the larger quantity of fish needed to compensate for the lower energy content of pollock. Thus, our sea lions would have had to eat 35-80% more pollock than herring to maintain similar net energy intakes. Results from our captive-feeding studies are consistent with the junk-food hypothesis and have serious implications for Steller sea lions that have been eating primarily pollock in the Gulf of Alaska and the Aleutian Islands.

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