Fig 1.
Rookeries where Steller sea lions were branded and regions where brand-resight surveys were conducted.
The primary study area, from Chirikof Island to Forrester Island, where Steller sea lions in Alaska were branded at natal rookeries in 2000–2011 and resighted from 2000–2014. Regions (circled and lettered) represent areas used to analyze mesoscale movements and distribution. Solid black lines indicate National Marine Fisheries Service-designated sub-regions (SEAK = Southeast Alaska, E. GOA = eastern Gulf of Alaska, C. GOA = central Gulf of Alaska, W. GOA = western Gulf of Alaska, E. Aleutians = eastern Aleutian Islands). Dashed line identifies stock boundary division at 144°W. Black dashed box indicates area within the eastern stock with the highest resight density of western stock sea lions.
Table 1.
Number of Steller sea lions branded as pups at their natal rookery in eastern and western stocks within Alaska.
Table 2.
Proportions of individual sea lions from each natal rookery, sex, and age-class seen in each Region during breeding season.
The natal rookery-age-sex diversity index for each region is shown at bottom of table, in italics. In sex-age column, F = female, M = male and associated numbers are animal ages in years. Bold face, underlined proportions indicate natal region. Regions (A-Q) and NMFS-designated sub-areas are shown on Fig 1.
Fig 2.
Mean distances Steller sea lions were observed from their natal rookery in Alaska.
(A) Female and (B) male distances were based on age and rookery of origin during the breeding season. Distances were plotted for each age group where ≥5 animals were observed. Dashed lines represent eastern stock rookeries and solid lines represent western stock rookeries.
Fig 3.
Maximum distances Steller sea lions were observed from their natal rookery in Alaska.
Distances were based on data collected during the breeding and non-breeding seasons.
Table 3.
Geographic ranges (i.e., minimum spanning tree lengths [km]) based on locations used by Steller sea lions, by natal rookery, sex, age class, and all ages combined.
Values are the distances among sites that were used by 2 or more marked SSLs; the values in parentheses include sites with only a single marked sea lion seen. Sample sizes for F:M are shown below rookery name.
Fig 4.
Geographic population range of female Steller sea lions born at Forrester and Hazy Islands.
Population range of female Steller sea lions born at Forrester and Hazy Islands estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 5.
Geographic population range of male Steller sea lions born at Forrester and Hazy Islands.
Population range of male Steller sea lions born at Forrester and Hazy Islands estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 6.
Geographic population range of female Steller sea lions born at Graves Rocks and White Sisters.
Population range of female Steller sea lions born at Graves Rocks and White Sisters estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 7.
Geographic population range of male Steller sea lions born at Graves Rocks and White Sisters.
Population range of male Steller sea lions born at Graves Rocks and White Sisters estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 8.
Geographic population range of female Steller sea lions born in Prince William Sound and at Chiswell Island.
Population range of female Steller sea lions born in Prince William Sound and at Chiswell Island estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 9.
Geographic population range of male Steller sea lions born in Prince William Sound and at Chiswell Island.
Population range of male Steller sea lions born in Prince William Sound and at Chiswell Island estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 10.
Geographic population range of female Steller sea lions born at Marmot and Sugarloaf Islands.
Population range of female Steller sea lions born at Marmot and Sugarloaf Islands estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 11.
Geographic population range of male Steller sea lions born at Marmot and Sugarloaf Islands.
Population range of male Steller sea lions born at Marmot and Sugarloaf Islands estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 12.
Geographic population range of Steller sea lions born at Ugamak Island.
Population range of male and female Steller sea lions born at Ugamak Island estimated using minimum spanning tree based on year-round observations of sea lions (of all ages combined) for each natal rookery. Thicker solid line indicates movement between two sites by >1 sea lion; thin lines indicate between-site movement by a single individual.
Fig 13.
Cluster analysis grouping of sites based on lists of branded sea lions at both sites.
All sites included in this figure had ≥10 individual Steller sea lions resighted there. Sites that join at 0 have the exact same individuals seen at both sites (i.e., 0 dissimilarity), while a value of 1 indicates no shared brands (i.e., complete dissimilarity). Colors represent the 7 most distinct groupings with 6 groups and 1 anomalous individual site. Letters before haulout and rookery names indicate the Region containing that site (see Fig 1 for Region designations), and National Marine Fisheries Service (NMFS) Sub-regions shown in abbreviate form before each Region (letter) used in this study.
Fig 14.
Correlations between female movement measures and population dynamics are shown within the black frame.
Movement measures include juvenile and adult proportion in natal region, juvenile and adult geographic range, and juvenile and adult mean distance from natal rookery; population dynamics include pup production, population trend, juvenile and adult survival. Correlations within population dynamics measures are shown outside the frame (top left) and correlations within movement measures are below the frame (bottom right).
Fig 15.
Correlations between male movement measures and population dynamics are shown within the black frame.
Movement measures include juvenile and adult proportion in natal region, juvenile and adult geographic range, and juvenile and adult mean distance from natal rookery; population dynamics include pup production, population trend, juvenile and adult survival. Correlations within population dynamics measures are shown outside the frame (top left) and correlations within movement measures are below the frame (bottom right).