Pup Production Following Harvest of Female Northern Fur Seals

1981 ◽  
Vol 38 (1) ◽  
pp. 84-90 ◽  
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

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

2014 ◽  
Vol 92 (10) ◽  
pp. 861-873 ◽  
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.

Average Age at First Reproduction of the Northern Fur Seal (Callorhinus ursinus)

1983 ◽  
Vol 40 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Anne E. York
Keyword(s):  
Cohort Analysis ◽  
The United States ◽  
Callorhinus Ursinus ◽  
Northern Fur Seal ◽  
Third Way ◽  
Age At First Reproduction ◽  
Fur Seal ◽  
First Reproduction ◽  
The Difference ◽  
First Time

Three methods of estimating average age at first reproduction of the northern fur seal, Callorhinus ursinus, are presented. For the first, the percentage of females pregnant for the first time is estimated from the percentage of primiparous pregnant females in the population. For the second, the percentage of females pregnant for the first time is estimated from the difference in the percentages of females pregnant at least once at successive ages. The jackknife variances of both estimates are presented. The estimates are calculated for the 1954–64 year-classes of northern fur seals using data collected at sea by the United States and Canada during 1958–74. By fitting parametric curves to the fraction pregnant at least once as a function of age and applying the second method to that resulting curve, the average age at first reproduction is estimated in a third way; this method is applicable to year-classes for which data are incomplete and estimates are given for the 1952, 1953, 1965, and 1966 year-classes. Age at first reproduction was lowest for the 1952–55 year-classes, increased sharply beginning with the 1956 year-class, and then gradually decreased almost to the level of the 1952–55 year-classes. Average age at first reproduction is negatively correlated with juvenile survival (birth to age 2 yr).Key words: fur seal, northern fur seal, Callorhinus ursinus; average age at first reproduction, cohort analysis, population dynamics

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

1975 ◽  
Vol 32 (12) ◽  
pp. 2447-2452 ◽  
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.

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

2000 ◽  
Vol 78 (1) ◽  
pp. 100-109 ◽  
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.

Separation of foraging habitat among breeding sites of a colonial marine predator, the northern fur seal (Callorhinus ursinus)

2004 ◽  
Vol 82 (1) ◽  
pp. 20-29 ◽  
Author(s):  
Bruce W Robson ◽  
Michael E Goebel ◽  
Jason D Baker ◽  
Rolf R Ream ◽  
Thomas R Loughlin ◽  
...  
Keyword(s):  
Breeding Site ◽  
Callorhinus Ursinus ◽  
Northern Fur Seal ◽  
Breeding Sites ◽  
Marine Predator ◽  
Fur Seals ◽  
Geographical Separation ◽  
Fur Seal ◽  
Satellite Transmitters ◽  
Breeding Seasons

This study examines whether lactating northern fur seals (Callorhinus ursinus) from different breeding sites on the Pribilof Islands in the eastern Bering Sea forage in separate areas. Satellite transmitters were attached to 97 northern fur seal females from nine breeding areas for 119 complete foraging trips during the 1995 and 1996 breeding seasons. Females from St. Paul and St. George islands tended to travel in different directions relative to their breeding site in both years of the study. St. Paul Island females dispersed in all directions except to the southeast, where St. George Island females foraged. Habitat separation was also observed among breeding areas on northeastern and southwestern St. Paul Island and to a lesser degree on northern and southern St. George Island. Although foraging direction led to geographical separation among sites, the maximum distance traveled and the duration of foraging trips did not differ significantly among islands in either year. The results of this study document that lactating fur seals from the same site share a common foraging area and that females from different breeding sites tend to forage in separate areas and hydrographic domains.

scholarly journals Antarctophthirus nevelskoyi n.sp. (Anoplura: Echinophthiriidae) - a new species of parasite of the Northern fur seal (Callorhinus ursinus L., 1758) at Tyuleniy Island, Okhotsk Sea, Russia

2021 ◽  
Vol 16 (2) ◽  
pp. 17-25
Author(s):  
M. Yu. Shchelkanov ◽  
E. M. Shchelkanov ◽  
T. V. Moskvina
Keyword(s):  
New Species ◽  
Room Temperature ◽  
Scientific Literature ◽  
Far East ◽  
Callorhinus Ursinus ◽  
Okhotsk Sea ◽  
Northern Fur Seal ◽  
Fur Seals ◽  
Fur Seal ◽  
A New Species

Aim. To perform a morphological study of seal lice (Anoplura: Echinophthiriidae) of the genus Antarctophthirus Enderlein, 1906 taken from Northern fur seals (Callorhinus ursinus L., 1758) at Tyuleniy Island, Okhotsk Sea, Russia).Material and Methods. Seal lice were collected from the nasal passages of Northern fur seal C. ursinus pups during a scheduled ecological and virological expedition to Tyuleniy Island in August 2017. Fourteen samples of seal lice (11 imago males, 1 imago female, 1 nymph of the 2nd age, 1 nymph of the 3-rd age) were stored in 70% ethanol at room temperature from the time of collection until the start of the study. Morphological features of the insects were studied using light and scanning electron microscopy and compared with the available data in the scientific literature.Results. Unique patterns of the arrangement of spines were found in the examined samples that is a sufficient species feature for representatives of this family and allows the identification of a new species of seal lice.Conclusion. A new species of seal lice, Antarctophthirus nevelskoyi n.sp., was identified and described and named after the famous Russian explorer of the Far East, Admiral Gennady Ivanovich Nevelskoy (18131876).

scholarly journals Swimming velocities in otariids

1990 ◽  
Vol 68 (10) ◽  
pp. 2105-2112 ◽  
Author(s):  
Paul J. Ponganis ◽  
Edward P. Ponganis ◽  
Katherine V. Ponganis ◽  
Gerald L. Kooyman ◽  
Roger L. Gentry ◽  
...  
Keyword(s):  
Metabolic Cost ◽  
Energy Costs ◽  
Callorhinus Ursinus ◽  
Northern Fur Seal ◽  
Cost Of Transport ◽  
Feeding Sites ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal ◽  
Time Partitioning

Velocities during surface swimming and diving were measured with microprocessor recorders in four otariid species: northern fur seals (Callorhinus ursinus), Galapagos sea lions (Zalophus californianus wollebaeki), Galapagos fur seals (Arctocephalus galapagoensis), and Hooker's sea lions (Phocarctos hookeri). Mean surface swimming velocities ranged from 0.6 to 1.9 m/s. Transit distances to feeding sites (1.2–90 km) were calculated using these velocities. Dive velocities, recorded every 15 s, ranged from 0.9 to 1.9 m/s. These velocities were consistent with calculated minimal cost of transport velocities in the smaller species. Using time partitioning, the metabolic cost of a northern fur seal foraging trip is estimated on the basis of recorded velocities and their calculated energy costs. This value is within 6% of that previously made with doubly labeled water techniques.

scholarly journals Analysis of commercial hunting on northern fur seal ( Callorhinus ursinus) at Tyuleny Island

2015 ◽  
Vol 183 (4) ◽  
pp. 71-80
Author(s):  
Alexey E. Kuzin
Keyword(s):  
Age Structure ◽  
Common Reason ◽  
Callorhinus Ursinus ◽  
Age Group ◽  
Commercial Fishery ◽  
Sex Composition ◽  
Northern Fur Seal ◽  
Fur Seals ◽  
Fur Seal ◽  
Commercial Hunting

Structure of commercial hunting on northern fur seal at Tyuleny Island is considered including effectiveness of podding, age-sex composition of the podded and captured animals, age structure of culled males, and reasons of culling. In total, the number from 2650 to 5099 of fur seals were podded during the harvest seasons of 1990-2008, 45.80 ± 2.17 % of them were killed and 54.20 ± 2.16 % were released. The bachelors prevailed among the podded animals, as well as in the bachelor rookeries (51.70 ± 2.56 %). The bulls were more numerous in the pod (35.80 ± 2.12 %) in compare with the half-bulls (10.20 ± 0.99 %) and the females (2.00 ± 0.85 %). Among the harvested animals, the bachelors prevailed, as well (93.50 ± 1.06 %), whereas the bulls, females, and half-bulls weren’t numerous (3.83 ± 0.87 %, 2.51 ± 0.67 %, 1.49 ± 0.29 %, respectively); frequency of the bulls and females captures changed from year to year. The most numerous age group of captured seals was the 3-year old animals (52.80 ± 1.60 %). All groups were presented among the culling animals, but the bachelors prevailed. The most common reason for culling was injuring of seals by commercial fishery wastes (scraps of fishing nets, ropes, packaging tapes, etc.): 64.20 ± 6.86 % of the culled animals were injured by the wastes.

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

2002 ◽  
Vol 80 (5) ◽  
pp. 902-909 ◽  
Author(s):  
Carolyn M Kurle
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Foraging Ecology ◽  
Isotope Ratios ◽  
Clupea Harengus ◽  
Callorhinus Ursinus ◽  
Blood Components ◽  
Fur Seals ◽  
Fur Seal ◽  
Northern Fur Seals

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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