A Fur Seal Population Model Based on Age Structure Data

1990 ◽  
Vol 47 (1) ◽  
pp. 122-127 ◽  
Author(s):  
L. L. Eberhardt
Keyword(s):  
Adult Female ◽  
Structure Data ◽  
Age Structure ◽  
Survival Rates ◽  
Reproductive Rate ◽  
Chi Square ◽  
Female Population ◽  
Fur Seals ◽  
Female Survival ◽  
Major Period

About 16 000 female fur seals from the Pribilof Islands population were aged in pelagic collections from 1958 through 1974. A simple simulation model of the female population was used to vary population parameters until a minimum chi-square value was achieved for the fit of simulated annual age structures to those observed in the pelagic collection. Population trajectories resulting from either a diminishing reproductive rate or diminishing adult female survival rate approximated estimated pup population sizes, which were not used in developing the model, except that a subset of five observations was used to constrain model trajectories to the general neighborhood of the observed pup populations. The main finding of the study was that adult female survival rates varied sharply during the 1964 through 1974 period, after the major period of harvests of female fur seals. Further study of the age structure data may thus be useful in evaluating the poorly understood long-term reduction in abundance of Pribilof fur seals.

Age structure, growth, and demographic parameters in breeding-age female subantarctic fur seals, Arctocephalus tropicalis

2004 ◽  
Vol 82 (7) ◽  
pp. 1043-1050 ◽  
Author(s):  
Willy Dabin ◽  
Gwénaël Beauplet ◽  
Enrique A Crespo ◽  
Christophe Guinet
Keyword(s):  
Age Distribution ◽  
Reproductive Rate ◽  
Reproductive Period ◽  
Demographic Parameters ◽  
Island Population ◽  
Female Population ◽  
Regulatory Processes ◽  
Fur Seals ◽  
Subantarctic Fur Seals ◽  
Arctocephalus Tropicalis

Age distribution was estimated for 108 breeding-age female subantarctic fur seals, Arctocephalus tropicalis (Gray, 1872), sampled during the 1999–2000 breeding season on Amsterdam Island, southern Indian Ocean. The growth features were described and demographic parameters assessed from transversal life tables constructed for this female population. The breeding females had a longer mean body length than was observed for other breeding populations of the same species. These females also showed a later start to reproduction (6 years old), a lower overall age-specific reproductive rate (R6–16 = 48.0%), and a lower survival in older age classes (>13 years). Females reproduced up to a maximum age of 16 years, with none older than 19 years observed in the colony, suggesting an apparent senescence in the population. This consequently reduced the theoretical reproductive period of the females, which has led to a lower number of reproductive outputs per individual (i.e., 3.65 weaned pups per female throughout its reproductive life). Although such differences between islands may be related to genotypic traits, these results are consistent with low food availability and suggest that density-dependent regulatory processes operate on the Amsterdam Island population.

Estimating Survival Rates with Age-Structure Data

1998 ◽  
Vol 62 (2) ◽  
pp. 779 ◽  
Author(s):  
Mark S. Udevitz ◽  
Brenda E. Ballachey
Keyword(s):  
Structure Data ◽  
Age Structure ◽  
Survival Rates

scholarly journals Estimating survival rates with time series of standing age-structure data

Ecology ◽  
2012 ◽  
Vol 93 (4) ◽  
pp. 726-732 ◽  
Author(s):  
Mark S. Udevitz ◽  
Peter J. P. Gogan
Keyword(s):  
Time Series ◽  
Structure Data ◽  
Age Structure ◽  
Survival Rates

Influence of intrinsic variation on foraging behaviour of adult female Australian fur seals

2015 ◽  
Vol 526 ◽  
pp. 227-239 ◽  
Author(s):  
AJ Hoskins ◽  
DP Costa ◽  
KE Wheatley ◽  
JR Gibbens ◽  
JPY Arnould
Keyword(s):  
Adult Female ◽  
Foraging Behaviour ◽  
Fur Seals

A longitudinal study of senescence in a pinniped

2002 ◽  
Vol 80 (3) ◽  
pp. 395-401 ◽  
Author(s):  
Pierre A Pistorius ◽  
Marthán N Bester
Keyword(s):  
Longitudinal Study ◽  
Adult Female ◽  
No Reduction ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Reproductive Senescence ◽  
Southern Elephant Seals ◽  
Female Survival ◽  
Breeding Seasons

To measure the prevalence of senescence in southern elephant seals (Mirounga leonina Linn.) at Marion Island, changes in adult-female survival and breeding probabilities with age were quantified. Mark–recapture data that had been collected over a 17-year period were analysed using recently developed software to obtain likelihood estimates of survival and capture probabilities. With recapture effort constant over the study period, capture probabilities during the breeding seasons were used as indices of breeding probabilities. Longevity in the population was assessed from the resighting of tagged and hence known-age individuals. Less than a 1% difference between prime-age survival and post prime age survival was found over 8 cohorts of marked females. In addition, no reduction in survival of very old individuals was detected, suggesting the absence of senescence in terms of reduced survival in southern elephant seals. No evidence of reproductive senescence in terms of reduced breeding probability with age was detected. Mortality throughout the population therefore resulted in no individuals surviving to the age where physiological decline would become a mortality agent or result in failure to breed. Five percent of female southern elephant seals survived to age 10 and 0.5% to age 17.

Differential fertility among immigrants to England and Wales and some implications for population projections

1969 ◽  
Vol 1 (S1) ◽  
pp. 119-127 ◽  
Author(s):  
Jean Thompson
Keyword(s):  
Age Structure ◽  
Age Groups ◽  
Population Projections ◽  
Fertility Rates ◽  
Female Population ◽  
Differential Fertility ◽  
England And Wales ◽  
Adult Age ◽  
Completed Family Size ◽  
Socio Economic Factors

SummaryThe age structure of the immigrant female population as shown by the 1961 Census was heavily biased towards the young adult age groups, where fertility rates are highest. The birth rate for such a population could be expected considerably to exceed the average for this country as a whole, due to differences in age structure alone. The Census also showed marked differences betwen the fertility rates of different groups of immigrants but suggested that for the most important groups —from the Irish Republic, the Indian sub-continent and the Caribbean—they then amounted to a completed family size of roughly ½ child above the England and Wales average. There were also marked differences in 1961 between the socio-economic structure of immigrant groups; such evidence as there is points to socio-economic factors as playing an important part in explaining the fertility of immigrants, and its possible change over time.

scholarly journals Pediatric Brain tumors in Southeast Nigeria; An 8-year prospective longitudinal cohort study

2019 ◽  
Author(s):  
Enoch Uche ◽  
Nkechi Judith Uche ◽  
Obinna V Ajuzieogu ◽  
Dubem Amuta ◽  
ephraim Onyia ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Survival Rates ◽  
Pediatric Brain Tumors ◽  
Common Symptom ◽  
Chi Square ◽  
Study Results ◽  
Chi Square Test ◽  
Poor Outcomes ◽  
Prospective Longitudinal ◽  
Pediatric Brain

Abstract Background: Pediatric brain tumors (PBT’s) from previous studies are associated with poor outcomes in our subregion. Methods. An 8 -year single center prospective study. All cases investigated with neuroimaging and treated were enrolled. Data was analyzed with SPSS (Inc) Chicago IL, USA version 23. Chi Square test, One-way Anova and confidence limits were used to evaluate associations using the 95% level of significance. Patients were followed up for a range of 1 to 7.5 years with a mean of 4.9 ±1.3years. Ethical approval was obtained for our study. Results: 95 patients were enrolled, 84 satisfied the study criteria. There were 45 males and 39 females, M: F=1.1. The mean age was 9.9±2.7 years 95%CI with a range of 9 months to 16 years. The most common symptom was headache for supratentorial lesions (73%) and gait disturbance (80.2%) for infratentorial lesions. More tumors were supratentorial in location (45(54.2%), while 33(37.1%) were infratentorial. Craniopharyngiomas (n=19), medulloblastomas(n=17) and astrocytomas (n=11) were the most common tumors. Hemoglobin genotype(AA and AS) had some influence on tumor phenotype, Odds ratio 8.9 and 3.3 for medulloblastoma and craniopharyngioma. 69 cases were microsurgically resected while 14 patients were treated with radiotherapy alone. The 30-day mortality for operated cases is 7.9±1.3%. Overall 1-year and 5-year survival was 67.9% and 53.6 % respectively. Survival rates varied among treatment groups (X2=8.9, P=0.017). Conclusion: Survival profile in this series suggests some improvement in comparison to previous studies from our region.

scholarly journals Clinical Spectrum of Angiomatous Granuloma and Inflammatory Fibrous Hyperplasia- A Retrospective Study

2020 ◽  
Vol 11 (SPL3) ◽  
pp. 159-162
Author(s):  
Rithanya P ◽  
Archana Santhanam ◽  
Subhashree R
Keyword(s):  
Age Groups ◽  
Hospital Setting ◽  
Clinical Spectrum ◽  
Complete Analysis ◽  
P Value ◽  
Chi Square ◽  
Female Population ◽  
Gingival Enlargement ◽  
Gingival Diseases ◽  
Chi Square Test

Angiomatous granuloma is a reactive tumour-like lesion commonly seen in the oral cavity. It generally occurs due to proliferation of capillary blood vessels. Whereas, inflammatory fibrous hyperplasia (IFH) refers to gingival enlargement, which is the current terminology for an increase in the size of the gingiva and is a common feature of gingival diseases. Therefore, the aim of the current study is to analyse the clinical spectrum of angiomatous granuloma/ IFH in a private dental hospital. This study was carried out in a hospital setting (single centred study). The data of the study subjects was collected after a complete analysis of data of 86000 patients between June 2019 and March 2020. The data of the patients, including age, gender clinical diagnosis and histopathological reports, were collected and analysed using the Chi-square test to find the association between the clinical and histopathological reports in the study. In the present study, angiomatous granuloma(55%) had a higher prevalence compared to IFH (40%) with higher gender predilection among the female population (61.5%) and generally in the age group ranging from 20 to 40 years. (57.5%) [p value= 0.329] statistically not significant. Similarly, IFH was also found to be higher in the female population of about (38.4%), in the age groups between 20 to 50 years (41.3%). The knowledge of various clinical presentations and histopathological characteristics the lesion is necessary for proper identification and treatment planning.

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