Stable-isotope ratios of blood components from captive northern fur seals (Callorhinus ursinus) and their diet: applications for studying the foraging ecology of wild otariids

Stable nitrogen and carbon isotope ratios (13C/12C and 15N/14N, respectively) of plasma, serum, clotted red blood cells, and unclotted red blood cells from six captive northern fur seals (Callorhinus ursinus) and two fish species in their diet, Atlantic herring (Clupea harengus) and Icelandic capelin (Mallotus villosus), were measured. The δ15N values from the fur seal blood components ranged from 15.5 ± 0.1 (mean ± SE; all RBCs) to 16.7 ± 0.1 (plasma), and δ13C values ranged from 18.3 ± 0.1 (serum) to 17.5 ± 0.1 (clotted RBCs). Fur seal blood components had higher δ15N and δ13C values than their diet. Mean enrichments of 15N between fur seal RBCs and plasma/serum and their prey were +4.1 and +5.2, respectively, while mean 13C enrichments were +0.6 (serum), +1.0 (plasma), and +1.3 to +1.4 (all RBCs). Fur seal blood components did not differ in δ15N or δ13C between the sexes. One female (Baabs) was pregnant at the time of sampling and was resampled 4 months later, when she was approximately 3 months post parturient. The δ15N values of the blood components taken from Baabs during pregnancy were all higher by 0.6 (unclotted RBCs) to 1.3 (plasma) than those of samples taken during lactation, while her δ13C values were nearly the same (RBCs) for the two time periods or lower during lactation by 0.5 (serum) and 0.7 (plasma). This study was the first to analyze isotope ratios of blood components from captive fur seals and their prey. The subsequent establishment of fractionation values between captive fur seals and their diet can be used to interpret trophic level and habitat usage of otariids feeding in the wild.

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Cation transport and regulatory volume increase in red blood cells of northern fur seals (Callorhinus ursinus)

Comparative Clinical Pathology ◽

10.1007/s00580-006-0615-5 ◽

2006 ◽

Vol 15 (2) ◽

pp. 76-81 ◽

Cited By ~ 2

Author(s):

H. Ochiai ◽

N. Hishiyama ◽

K. Higa ◽

S. Hisamatsu ◽

K. Koyama ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Cation Transport ◽

Callorhinus Ursinus ◽

Volume Increase ◽

Regulatory Volume Increase ◽

Fur Seals ◽

Northern Fur Seals

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Spatial segregation and the influence of habitat on the foraging behavior of northern fur seals (Callorhinus ursinus)

Canadian Journal of Zoology ◽

10.1139/cjz-2014-0087 ◽

2014 ◽

Vol 92 (10) ◽

pp. 861-873 ◽

Cited By ~ 16

Author(s):

C.E. Kuhn ◽

R.R. Ream ◽

J.T. Sterling ◽

J.R. Thomason ◽

R.G. Towell

Keyword(s):

Conservation Strategy ◽

Foraging Strategies ◽

Habitat Segregation ◽

Callorhinus Ursinus ◽

Foraging Habitat ◽

Northern Fur Seal ◽

Dive Behavior ◽

Fur Seals ◽

Fur Seal ◽

Northern Fur Seals

Central place foraging by colonial breeders can lead to depleted prey resources around breeding areas. Segregation of foraging areas both within and between large colonies may act as a mechanism to reduce competition for prey resulting in increased foraging success. We reassessed horizontal (spatial) foraging habitat segregation for northern fur seals (Callorhinus ursinus (L., 1758)) within and between colonies on the Pribilof Islands, Alaska (St. Paul and St. George islands), after the population declined by approximately 40%. Additionally, we examined vertical habitat segregation, where foraging ranges overlapped, and describe the influence of different foraging habitats on northern fur seal dive behavior. Spatial habitat segregation in northern fur seal foraging areas occurred between islands but was variable within islands, which is similar to the pattern previously described. There was no evidence for vertical habitat segregation when fur seals from different rookeries on St. George Island used the same foraging area. Additionally, fur seals from St. Paul Island rookeries that foraged in similar habitats showed fewer differences in dive behavior, indicating that foraging habitat plays a significant role in shaping dive behavior. The use of multiple foraging strategies within the Pribilof Island fur seal population could indicate that a complex management and conservation strategy may be necessary to stop the continuing decline of this population.

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Pup Production Following Harvest of Female Northern Fur Seals

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f81-011 ◽

1981 ◽

Vol 38 (1) ◽

pp. 84-90 ◽

Cited By ~ 43

Author(s):

Anne E. York ◽

James R. Hartley

Keyword(s):

Cohort Analysis ◽

Survival Rates ◽

Callorhinus Ursinus ◽

Northern Fur Seal ◽

Fur Seals ◽

Fur Seal ◽

Seal Population ◽

Northern Fur Seals ◽

Early Survival ◽

The Difference

Female northern fur seals (Callorhinus ursinus) were harvested commercially from 1956 to 1968 and pelagic collections were taken for research purposes from 1958 to 1974. Early survival rates (birth to age 2) for males increased from an average of 0.32 before the harvest to 0.38 afterwards. Numbers of female pups whose births were precluded by the harvest are estimated for the years 1956–79; these account for about 70% of the difference between the numbers of pups actually born and the level of pup births before 1956. Estimates of the increased numbers of pups due to the increase in the early survival rates are presented for the years 1958–74.Key words: northern fur seal, population dynamics, female harvest, cohort analysis, St. Paul Island

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Regulatory volume decrease in northern fur seal (Callorhinus ursinus) red blood cells

Comparative Clinical Pathology ◽

10.1007/s00580-006-0643-1 ◽

2006 ◽

Vol 16 (1) ◽

pp. 61-63

Author(s):

H. Ochiai ◽

N. Hishiyama ◽

K. Higa ◽

K. Koyama ◽

M. Seita ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Regulatory Volume Decrease ◽

Callorhinus Ursinus ◽

Northern Fur Seal ◽

Fur Seal ◽

Volume Decrease

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Acanthocephalans in northern fur seals (Callorhinus ursinus) and a harbor seal (Phoca vitulina) on St. Paul Island, Alaska: species, prevalence, and biodiversity in four fur seal subpopulations

Parasitology Research ◽

10.1007/s00436-012-2930-x ◽

2012 ◽

Vol 111 (3) ◽

pp. 1049-1058 ◽

Cited By ~ 11

Author(s):

T. A. Kuzmina ◽

O. I. Lisitsyna ◽

E. T. Lyons ◽

T. R. Spraker ◽

S. C. Tolliver

Keyword(s):

Harbor Seal ◽

Phoca Vitulina ◽

Callorhinus Ursinus ◽

Fur Seals ◽

Fur Seal ◽

Northern Fur Seals

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Method of Determining Natural Mortality in the Northern Fur Seal (Callorhinus ursinus) from Known Pups and Kill by Age and Sex

Journal of the Fisheries Research Board of Canada ◽

10.1139/f75-282 ◽

1975 ◽

Vol 32 (12) ◽

pp. 2447-2452 ◽

Cited By ~ 15

Author(s):

Robert H. Lander

Keyword(s):

Relative Error ◽

Present Method ◽

Callorhinus Ursinus ◽

Natural Mortality ◽

Northern Fur Seal ◽

Fur Seals ◽

Hypothetical Data ◽

Fur Seal ◽

Northern Fur Seals ◽

Age And Sex

From known values of the number of northern fur seals, Callorhinus ursinus, born in a given year and the commercial kill of older animals of this species, by age and sex, a method is given for approximating natural mortality or survival 1) between times of birth and the first kill and 2) during the successive ages of kill. An example with hypothetical data indicates small relative error in these estimators, although bias may be considerable in certain of the associated age-specific estimators of abundance and exploitation rates. The problem of bias warrants further investigation. Estimates of natural survival from birth to the start of the kill at age 2 yr agree closely with independent tagging estimates for the 1964–66 year-classes of males from the Pnbilof Islands, Alaska. For this stock, further applications of the present method to the 1961–66 year-classes of males indicate natural survival of 31–42% during ages 0–2 yr and 84–89% annually during ages 2–5 yr.

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Ontogeny of swimming and diving in northern fur seal (Callorhinus ursinus) pups

Canadian Journal of Zoology ◽

10.1139/z99-190 ◽

2000 ◽

Vol 78 (1) ◽

pp. 100-109 ◽

Cited By ~ 16

Author(s):

Jason D Baker ◽

Mary J Donohue

Keyword(s):

Surface Temperature ◽

Early Growth ◽

Sea Surface ◽

Diving Behavior ◽

Callorhinus Ursinus ◽

Northern Fur Seal ◽

Fur Seals ◽

Fur Seal ◽

Northern Fur Seals ◽

Maternal Strategy

Time spent in the water and diving behavior of northern fur seal (Callorhinus ursinus) pups were monitored between birth and weaning at St. Paul Island, Alaska. The median age when pups began swimming was 26 days, but prior to 40 days of age they spent virtually all their time on shore and only rarely took brief (15-20 min) swims. Pups began spending substantial time in the water at approximately 40-50 days of age, coinciding both with the early growth of insulating underfur and a seasonal peak in sea surface temperature. This suggests that pups had earlier been constrained to remain on shore by their undeveloped thermoregulatory capabilities. Time in the water increased up to approximately 100 days of age, when molted pups spent about 35% of their time in the water and swim bouts were several hours in duration. Moreover, the presence of a pup's mother on shore, photoperiod, and precipitation also influenced the amount of time pups spent in the water. Pups (mean age = 100 days) dove to very shallow depths (mean = 3 m) for short durations (mean = 11 s). Because pups did not gain mass unless suckled by their mothers, it is unlikely that they fed extensively while diving prior to migration. The pattern of development of swimming and diving in northern fur seals is intermediate between typical phocid and otariid patterns, as is the maternal strategy.

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