Figure 1.
Adult male and female northern fur seal migratory routes.
Map shows Large Marine Ecosystem delineations and all 6(the black dots), six adult females with diving data (the red dots), and four adult females without diving data (the blue dots).
Table 1.
Summary of capture information, satellite transmission durations, and Aleutian pass usage of adult male and female northern fur seals.
Figure 2.
Percent of the estimated total adult male and female northern fur seal migratory period spent in each ecosystem.
To make this calculation, we assumed return dates of 1 June for males (M) and 10 July for females (F).
Figure 3.
The effect of wind and season on adult male and female northern fur seal behavioral states.
These figures were constructed using the linear mixed-effects model coefficients from Table 3 depicting days since 1 October (season) and wind speed. The vertical dashed lines indicate the first and last migration departure date of the seals in this study.
Table 2.
Top three linear mixed-effects models selected using Akaike Information Criterion (AIC) for each adult male and female northern fur seal response variable examined.
Table 3.
Best linear mixed-effects model results and estimated coefficients for the effects on adult male and female northern fur seal behavioral state.
Figure 4.
Relationships between adult male and female northern fur seal mass and dive behaviors.
Significant linear regression relationships were found between fur seal mass and their average dive depth (A), average maximum dive depth (B), average dive duration (C), and average maximum dive duration (D). The relationship between average fur seal dive depths and the average number of dives (E) was also significant.
Table 4.
Average dive depth and the percentage of dives of adult male and female northern fur seals summarized for each Large Marine Ecosystem (LME) and grouped by daylight periods.
Figure 5.
Dive response of adult male and female northern fur seals to light (moon and sun) and mixed-layer depth.
These figures were constructed using the linear mixed-effects model coefficients from Table 5. The top figure shows the effect of moonlight and sunlight on female dive behavior while the bottom figure shows the effect of sunlight and mixed-layer depth on male dive behavior. Both plots represent adult diving in the North Pacific Ocean (NP) ecosystem.
Table 5.
Best linear mixed-effects model results and estimated coefficients for the effects on adult male and female northern fur seal average dive depths.
Figure 6.
The effect of daylight on the number of dives of adult male and female northern fur seals.
Each line represents an ecosystem: NP = North Pacific Ocean, AS = Alaska Stream, BB = Bering Sea Basin, BS = Bering Sea Shelf, CC = California Current, GA = Gulf of Alaska (see Fig. 1). In most cases, male dives (bottom) increased with increased proportion of light in each 6 h period. This response was opposite of adult females (top), which dived more during the night; a notable exception occurred in the CC ecosystem where one female exhibited an increase in the number of dives per 6 h period with increasing daylight.
Table 6.
Best linear mixed-effects model results and estimated coefficients for the effects on adult male and female northern fur seal average number of dives.
Figure 7.
Spatial distribution of stormy days in relation to adult male and female northern fur seal migratory tracks.
Stormy days, defined as the proportion of days wind speeds were greater than 11−1 [53] during the November-March time period, were compared to male (the black dots) and female (the red dots) migratory tracks. Males remained in the stormy regions of the North Pacific Ocean, while females traveled to regions experiencing fewer stormy days along the continental margins of North America.
Figure 8.
Relationship between adult female northern fur seal behavioral state, eddy distribution and ecosystem.
Left panels: Behavioral states (solid black line; left y-axis) of four females compared to the distance of the closest eddy edge (colored dots; right y-axis) in each Large Marine Ecosystem traversed: NP = North Pacific Ocean, AS = Alaska Stream, BB = Bering Sea Basin, BS = Bering Sea Shelf, CC = California Current, GA = Gulf of Alaska (see Fig. 1). Right panels: female geographic distributions–color dots scale distance to the closest eddy edge. While females traversed several eddies during their winter migration, they appeared to dramatically shift their behavioral state to resident when aligned along eddy edges and once they arrived in the GA and CC ecosystems.
Figure 9.
Adult male northern fur seal average dive depths in relation to the mixed-layer depth (MLD).
Left panels: Average dive depth (colored dots) in relation to the MLD for males 679 and 682. The black line is the MLD calculated from the CTD measurements taken onboard the males, and the colored dots represent the proportion of light during each 6 h dive period grouped into four categories (Day, Mostly Day, Mostly Night, and Night). Male 679 (top panel) foraged in several Large Marine Ecosystems (LME) before spending the majority of his time in the North Pacific Ocean (NP) ecosystem. Each LME visited by male 679 is identified by a combination of the bottom depth (gray line) and the corresponding LME (NP = North Pacific Ocean, BB = Bering Sea Basin, BS = Bering Sea Shelf). Right panels: foraging locations of these males during the winter.