Impact of the 1982–1983 El Niño on the Northern Fur Seal Population at San Miguel Island, California

1991 ◽  
pp. 75-83 ◽  
Author(s):  
R. L. DeLong ◽  
G. A. Antonelis
Keyword(s):  
El Niño ◽  
El Nino ◽  
Northern Fur Seal ◽  
Fur Seal ◽  
Seal Population ◽  
San Miguel Island

Long term population changes of fur seals Arctocephalus gazella and Arctocephalus tropicalis on subantarctic (Crozet) and subtropical (St. Paul and Amsterdam) islands and their possible relationship to El Niño Southern Oscillation

1994 ◽  
Vol 6 (4) ◽  
pp. 473-478 ◽  
Author(s):  
C. Guinet ◽  
P. Jouventin ◽  
J-Y. Georges
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events ◽  
Fur Seals ◽  
Fur Seal ◽  
Arctocephalus Tropicalis

The population trend over the last decade for subantarctic fur seals (Arctocephalus tropicalis) on Amsterdam and St. Paul islands and on Possession Island (Crozet Archipelago) and Antarctic fur seals (A. gazella) on Possession Island are analysed. At Amsterdam Island, based on pup counts, the subantarctic fur seal population appears to have stabilized after a period of rapid growth. At Possession Island subantarctic fur seal and Antarctic fur seal, with respective annual growth rates of 19.2 and 17.4%, are reaching the maximum growth rate for the genus Arctocephalus. Annual pup censuses at Possession Island since 1978 indicate important variations from year to year with pup production for A. gazella significantly lower the year after an El Niño Southern Oscillation (ENSO) event, but with no such relationship for A. tropicalis. Several other long term demographic studies of seabirds and marine mammals at different breeding locations in the Southern Ocean indicate that the breeding success of several of these predators appears to be widely affected in years which appear to be related to the ENSO events. To clarify this, it is necessary to analyse in more detail the demographic data obtained for the different subantarctic and Antarctic locations where long term monitoring programmes are conducted.

A Review of Northern Fur Seal Population Modelling

1992 ◽  
pp. 1051-1061
Author(s):  
Timothy J. Ragen ◽  
Charles W. Fowler
Keyword(s):  
Population Modelling ◽  
Northern Fur Seal ◽  
Fur Seal ◽  
Seal Population

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

Evidence of a genetic bottleneck in an El Niño affected population of South American fur seals, Arctocephalus australis

2009 ◽  
Vol 89 (8) ◽  
pp. 1717-1725 ◽  
Author(s):  
Larissa Rosa de Oliveira ◽  
Diogo Meyer ◽  
Joseph Hoffman ◽  
Patricia Majluf ◽  
João S. Morgante
Keyword(s):  
Population Size ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Genetic Bottleneck ◽  
South American ◽  
Enso Events ◽  
Fur Seals ◽  
The Pacific ◽  
Fur Seal

The South American fur seal, Arctocephalus australis, was one of the earliest otariid seals to be exploited by humans: at least 6000 years ago on the Atlantic coast and 4000 on the Pacific coast of South America. More than 750,000 fur seals were killed in Uruguay until 1991. However, a climatological phenomenon—the severe 1997–1998 El Niño Southern Oscillation (ENSO)—was responsible for the decline of 72% of the Peruvian fur seal population due to starvation as a consequence of warming of sea-surface temperatures and primary productivity reduction. Currently, there is no precise information on global population size or on the species' conservation status. The present study includes the first bottleneck test for the Pacific and Atlantic populations of A. australis based on the analysis of seven microsatellite loci. Genetic bottleneck compromises the evolutionary potential of a population to respond to environmental changes. The perspective becomes even more alarming due to current global warming models that predict stronger and more frequent ENSO events in the future. Our analysis found moderate support for deviation from neutrality–equilibrium for the Pacific population of fur seals and none for the Atlantic population. This difference among population reflects different demographic histories, and is consistent with a greater reduction in population size in the Pacific. Such an event could be a result of the synergic effects of recurrent ENSO events and the anthropogenic impact (sealing and prey overfishing) on this population.

scholarly journals Mammalia, Carnivora, Otariidae, Arctocephalus galapagoensis Heller, 1904: first continental record for Costa Rica

Check List ◽  
2010 ◽  
Vol 6 (4) ◽  
pp. 630 ◽  
Author(s):  
Andrea Montero-Cordero ◽  
Damián Martínez Fernández ◽  
Gabriela Hernández-Mora
Keyword(s):  
Costa Rica ◽  
El Niño ◽  
El Nino ◽  
First Record ◽  
Costa Rican ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Eastern Equatorial Pacific ◽  
Fur Seal ◽  
Eastern Equatorial Pacific Ocean

This is the first record of Arctocephalus galapagoensis for the mainland coast of Costa Rica, which is outside the geographical distribution of this species about 1,300 km from its type locality. Changes in environmental conditions during El Niño events might be responsible for a higher incidence of these sightings. The presence of a moderate El Niño along the central and eastern equatorial Pacific Ocean during this month coincides with the occurrence of the fur seal in Costa Rican coasts. No photo record had ever been registered before for this country.

scholarly journals Peruvian Fur Seals as Archivists of El Niño Southern Oscillation Effects

2021 ◽  
Vol 8 ◽  
Author(s):  
Mickie R. Edwards ◽  
Susana Cárdenas-Alayza ◽  
Michael J. Adkesson ◽  
Mya Daniels-Abdulahad ◽  
Amy C. Hirons
Keyword(s):  
Food Web ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events ◽  
La Nina ◽  
Fur Seal

Peru’s coastal waters are characterized by significant environmental fluctuation due to periodic El Niño- La Niña- Southern Oscillation (ENSO) events. This variability results in ecosystem-wide food web changes which are reflected in the tissues of the Peruvian fur seal (Arctocephalus australis). Stable isotope ratios (δ13C and δ15N) in Peruvian fur seal vibrissae (whiskers) are used to infer temporal primary production and dietary variations in individuals. Sea surface temperature anomaly (SSTA) recordings from the Niño 1+2 Index region captured corresponding ENSO conditions. Fluctuations in δ15N values were correlated to SSTA records, indicating that ENSO conditions likely impact the diet of these apex predators over time. Anomalous warm phase temperatures corresponded to decreased δ15N values, whereas cold phase anomalous conditions corresponded to increased δ15N values, potentially from upwelled, nutrient-rich water. Vibrissae δ13C values revealed general stability from 2004 to 2012, a moderate decline during 2013 (La Niña conditions) followed by a period of increased values concurrent with the 2014–2016 El Niño event. Both δ13C and δ15N values were inversely correlated to each other during the strongest El Niño Southern Oscillation event on record (2014–2016), possibly indicating a decline in production leading to an increase in food web complexity. Lower δ13C and δ15N values were exhibited in female compared to male fur seal vibrissae. Findings suggest ENSO conditions influence resource availability, possibly eliciting changes in pinniped foraging behavior as well as food web of the endangered Peruvian fur seal.

scholarly journals Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation

1999 ◽  
Vol 77 (8) ◽  
pp. 1204-1216 ◽  
Author(s):  
Thomas Dellinger ◽  
Fritz Trillmich
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Season ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Niche Separation ◽  
Fish Prey ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal

Analysis of fish otoliths in scats and vomits of Galápagos fur seals (Arctocephalus galapagoensis) and Galápagos sea lions (Zalophus californianus wollebaeki) was used to determine the numerical composition of the diets for the post-El Niño year 1983, the cold seasons in 1984 and 1985, and the warm season in 1986. Between 84 and 99% of all otoliths in fur seal scats were from myctophids and bathylagids. The fur seals' diet included 26 species. Only 3 species contributed more than 1% of otoliths. No seasonal differences in diet were found. Sea lion samples contained a mean of 14 otoliths. Sardines (Sardinops sagax) contributed 75-85% of otoliths. Sea lions preyed on 24 species, but only 3 surpassed 1% abundance. Seasonality was not reflected in the sea lions' diet. After the 1982-1983 El Niño, the diets of both species deviated from those in all other years of the study. Food-niche overlap between the two sympatric species was almost non-existent. This is hard to understand, based on our knowledge of the diving capabilities of the two species, but reflects the fact that Galápagos fur seals are nighttime foragers and sea lions are daytime foragers.

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