innipeds of the Southern California Planning Area
Pinnipeds, seals and sea lions, are an important part of the marine life of southern
California. Four species of non-endangered pinnipeds occur in this area: the California
sea lion, northern fur seal, northern elephant seal, and harbor seal. Two other species,
the Guadalupe fur seal and Steller sea lion, are listed as threatened under the Endangered
Species Act.
California sea lions range from British Columbia to Mexico. The world population
(excluding a small Galapagos population) is estimated at over 200,000 animals, of which
the U.S. population accounts for about 110,000. In California, California sea lions are
the most abundant pinnipeds on land and in waters over the continental shelf. They breed
in the summer, from May through July, on islands from the Gulf of California in Mexico to
the California Channel Islands. In the fall following the breeding season, thousands of
California sea lions, mainly immature and adult males, disperse northward from the
California breeding grounds to winter along the coast as far north as British Columbia.
California sea lions currently breed on four islands in southern California: San
Miguel, San Nicolas, Santa Barbara, and San Clemente. Of these, San Miguel and San Nicolas
are by far the largest rookeries. Other islands and nearshore rocks along the coast are
frequented by nonbreeding animals. California sea lions feed on a variety of prey,
including seasonally abundant small schooling fishes and squids. In southern California,
the major components of the California sea lion diet include anchovy, rockfish, whiting,
mackerel, squids, and octopus.
Northern fur seals range at sea from the Bering Sea south to Baja California in the
eastern North Pacific. The world population is estimated at a little over 1 million
animals, of which more than 900,000 are associated with the Pribilof Islands rookeries in
Alaska; the remainder are associated with Russian islands and the small San Miguel Island
rookery off southern California. This rookery has a breeding population of 5,000 to 7,000
animals. Northern fur seals have been harvested commercially for their pelts since the
late 1700's, although currently they are only taken in low numbers in Russian waters
Northern fur seals breed during the summer, from June through August. Pups are weaned
in October or November, when their mothers leave the rookeries to begin their winter
migration. Following the breeding season, adult females and many juveniles migrate
southward along the west coast of North America between Southeast Alaska and California;
most adult males apparently remain in Alaskan waters. Fur seal numbers off California, the
major wintering ground, peak in February when several hundred thousand are present. Mature
females begin returning northward in March, while younger animals may remain until May or
June. While at sea, northern fur seals are generally found offshore along the continental
slope and shelf. Off California, important northern fur seal prey includes fish species
such as anchovy, herring, whiting, saury, rockfish, and a variety of squids.
Northern elephant seals have substantially recovered from near extinction by commercial
sealers in the 19th century and have recolonized much of their former range. The species'
breeding range presently extends from Baja California to Point Reyes in northern
California, and elephant seals range at sea from Mexico to the Gulf of Alaska. As of 1991,
the northern elephant seal population was estimated at approximately 130,000 animals.
More than half of the total elephant seal population is associated with rookery islands
in southern California. The largest populations are found on San Miguel and San Nicolas
Islands; small colonies also exist on Santa Barbara and San Clemente Islands.
Northern elephant seals typically come ashore only to breed and molt. The breeding
season lasts from mid-December to March, and pups remain on the rookery for another month
or so. Juveniles of both sexes and adult female elephant seals come ashore again to molt
their hair and skin in late April and early May. Large males and a few juveniles come
ashore for their annual molt in mid-summer, while yearling and some juvenile elephant
seals are on land in autumn.
Northern elephant seals make two migrations per year, and the sexes segregate while at
sea. Females generally travel to foraging areas in the central Pacific, while males forage
in waters in the Gulf of Alaska and south of the Aleutians. Elephant seals are capable of
diving to depths of nearly a mile. They apparently forage mainly in waters over and beyond
the continental shelf, and feed on a wide variety of prey, including squids, fishes,
sharks and rays, lamprey, octopi, crustaceans, and tunicates.
Harbor seals in the eastern North Pacific are found along the coastline from Mexico to
the Aleutians. The North Pacific harbor seal population is estimated at 320,000 animals
and is centered in Alaska.
In southern California, harbor seals come ashore in greatest numbers on the Channel
Islands, particularly the northern chain. Along the mainland, they occur primarily on
secluded rocks and beaches. Peak harbor seal populations on land occur during the species'
spring breeding and pupping season and during the early summer molt. Following the
breeding and pupping season, harbor seals disperse along the coast and spend more time at
sea during fall and winter. Although harbor seals apparently do not migrate, movements of
15 miles or more are common. Other studies have documented use of several different
beaches sometimes separated by more than 60 miles, by individual seals in a single season.
Harbor seals forage close to shore and are typically sighted in coastal waters. They feed
on a variety of marine and estuarine prey, including a number of species of fish, lamprey,
octopus, squids, and shrimp.
Selected Readings
Bonnell, M.L., and M.D. Dailey. 1993. Marine mammals of the Southern California Bight.
Pp. 604-681, in, M.D. Dailey, D.J. Reish, and J.W. Anderson (eds.), Ecology of the
Southern California Bight: A Synthesis and Interpretation. University of California Press,
Berkeley/Los Angeles
Croxall, J.P., and R.L. Gentry (eds.). 1987. Status, Biology, and Ecology of Fur Seals.
Proceedings of an International Symposium and Workshop, Cambridge, England, 23-27 April
1984. NOAA Technical Report NMFS 51. 212 pp.
DeLong, R.L., B.S. Stewart, and R.D. Hill. 1992. Documenting migrations of northern
elephant seals using day length. Marine Mammal Science 8(2):155-159.
Gentry, R.L., and G.L. Kooyman. 1987. Fur Seals: Maternal Strategies on Land and at
Sea. Princeton Univ. Press, Lawrenceville, New Jersey. 291 pp.
Haley, D. (ed.). 1986. Marine mammals of the eastern North Pacific and Arctic waters
(2nd. ed. rev.). Pacific Search Press, Seattle, Washington.
Le Boeuf, B.J., and S. Kaza (eds.). 1981. The Natural History of Año Nuevo. The
Boxwood Press, Pacific Grove, California. 425 pp.
Le Boeuf, B.J., and M.L. Bonnell. 1981. Pinnipeds of the California Islands: abundance
and distribution. Pp. 475-493, in, D.M. Power (ed.), The California Islands: Proceedings
of a Multi-disciplinary Symposium. Santa Barbara Museum of Natural History, Santa Barbara,
California.
Le Boeuf, B.J., Y. Naito , A.C. Huntley, and T. Asaga. 1989. Prolonged, continuous,
deep diving by northern elephant seals. Canadian Journal of Zoology 67:2514-2519.
Orr, R.T., and R.C. Helm. 1989. Marine Mammals of California. California Natural
History Guides: 29. University of California Press, Berkeley. 93 pp.
Ridgway, S.H., and R.J. Harrison (eds.). 1981. Handbook of marine mammals, Vol. 1: The
walrus, sea lions, fur seals, and sea otter. Academic Press, New York.
Ridgway, S.H., and R.J. Harrison (eds.). 1981. Handbook of marine mammals,Vol. 2:
Seals. Academic Press, New York.
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