Effects of the El Niño 1982–83 on California Sea Lions in Mexico

We compared the nonbreeding-season foraging behavior of lactating California sea lions ( Zalophus californianus californianus (Lesson, 1828)) at San Miguel Island, California, during El Niño conditions in 1993 and non-El Niño conditions in 1996. Lactating females were instrumented with satellite-linked time–depth recorders between January and March in 1993 (n = 6) and 1996 (n = 10) and data were collected through May in each year. Females foraged northwest of the colony, up to 367 km from it and 230 km from the California coast. Mean dive depths ranged from 19.5 to 279.3 m, but most females achieved dives deeper than 400 m. Most females fed exclusively in the offshore habitat, traveled farther from the colony, spent more time traveling, made deeper and longer dives, and terminated lactation earlier during the 1993 El Niño. The results suggest that prey were concentrated in the offshore habitat and located farther from the colony and deeper in the water column during El Niño. Females did not change their foraging direction, foraging-trip duration, foraging effort, or prey species consumed.

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Effects of El Niño 1983 on the Foraging Patterns of California Sea Lions (Zalophus californianus) near San Miguel Island, California

Ecological Studies - Pinnipeds and El Niño ◽

10.1007/978-3-642-76398-4_16 ◽

1991 ◽

pp. 146-155 ◽

Cited By ~ 4

Author(s):

S. D. Feldkamp ◽

R. L. DeLong ◽

G. A. Antonelis

Keyword(s):

El Niño ◽

El Nino ◽

Zalophus Californianus ◽

California Sea Lions ◽

Foraging Patterns ◽

Sea Lions ◽

San Miguel Island

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

Canadian Journal of Zoology ◽

10.1139/z99-095 ◽

1999 ◽

Vol 77 (8) ◽

pp. 1204-1216 ◽

Cited By ~ 34

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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Effective population size for South American sea lions along the Peruvian coast: the survivors of the strongest El Niño event in history

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315411001871 ◽

2012 ◽

Vol 92 (8) ◽

pp. 1835-1841 ◽

Cited By ~ 9

Author(s):

Larissa Rosa de Oliveira ◽

Lúcia Darsie Fraga ◽

Patricia Majluf

Keyword(s):

Population Size ◽

El Niño ◽

El Nino ◽

South American ◽

Effective Population ◽

Sea Lions ◽

El Niño Event ◽

Peruvian Coast ◽

El Niño Events ◽

El Nino Events

The South American sea lion, Otaria flavescens, has been considered vulnerable and under the threat of extinction in Peru due to the drastic demographic changes as a result of the impact of low food availability and the unusual timing of the severe El Niño event of 1997–1998. We present the first estimate of effective population size (Ne) for the species that takes into account the effects of mating system and variation in population size in different generations caused by the severe El Niño event of 1997–1998. The resulting Ne was 7715 specimens. We believe that the estimated Ne for the Peruvian population is not a critical value, because it is higher than the mean minimum viable population generally accepted for vertebrates (ca. 5000 breeding adults). However, the viability of O. flavescens on the Peruvian coast may depend primarily on local availability of food resources. Climatic change models predict stronger and more frequent El Niño events. In this sense, the Ne of 7715 should be considered as a value to be maintained in order to keep the population large enough to avoid inbreeding or to retain adaptive genetic variation to survive to future El Niño events. Moreover, this Ne estimate is important data in discussions about resuming culling activities, based on the statement of an increasing competition between fishery activity and sea lions during El Niño events. Thus, this Ne should be taken into account in future management plans to ensure the conservation of the species on the Peruvian coast.

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