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California sea lion below Bonneville Dam
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California
sea lion fact sheet
California sea lions
(Zalophus californianus californianus) are large marine mammals
in the pinniped family, which includes seals and walruses. Male California
sea lions can measure eight feet long and reach a weight of 1,000 pounds
or more. Females can reach six feet in length and weigh up to 250 pounds.
California sea lions
are one of two species of sea lions found in Washington state waters,
the other being Steller sea lions (Eumetopias jubata), which
are larger in size.
- Range:
California sea lions are found from the southern tip of Baja California
to southeast Alaska. They breed mainly on offshore islands from southern
California’s Channel Islands south to Mexico. Non-breeding males
often roam north in spring foraging for food. Since the mid-1980s, increasing
numbers of California sea lions have been documented feeding on fish
along the Washington coast and – more recently – in the
Columbia River as far upstream as Bonneville Dam, 145 miles from the
river mouth.
- Population:
The U.S. population of California sea lions is currently estimated at
up to 300,000 animals, all on the Pacific coast. From an estimated population
of about 10,000 animals in the 1950s, U.S. California sea lion numbers
have grown rapidly since the 1970s and the species is now at “carrying
capacity”—near the highest level the environment can sustain—according
to wildlife biologists. A population survey conducted in 2006 by the
Washington Department of Fish and Wildlife (WDFW) documented 1,200 California
sea lions and 1,000 Steller sea lions near the mouth of the Columbia
River alone.
- Diet:
California sea lions feed on a variety of fish and shellfish, including
salmon, steelhead, Pacific whiting, herring, mackerel, eulachon, lamprey,
codfish, walleye Pollock, spiny dogfish and squid. In recent years,
they have also been observed preying on Columbia River sturgeon. Studies
of scat samples collected in coastal waters and the Columbia River estuary
indicate that salmon comprise 10 to 30 percent of the animals’
diet. Additional studies have shown that the percentage of salmon and
steelhead in sea lions’ diet increases as they move upriver. Each
year since 2004, California sea lions have consumed 3,000 to 3,500 salmon
and steelhead immediately below Bonneville Dam, according to an ongoing
study by the U.S. Army Corps of Engineers.
- Conservation
status: Like all marine mammals, California sea lions are managed
under the federal Marine Mammal Protection Act (MMPA) of 1972. They
are not, however, designated as a “depleted” population
under the MMPA, nor are they listed for protection under the Endangered
Species Act (ESA). While the MMPA was intended to protect marine mammals
from human interference, the law was amended in 1994 to provide a process
for states to lethally remove individual California sea lions that threaten
recovery of salmon and steelhead stocks listed for protection under
the ESA. This provision does not apply to Steller sea lions, which are
listed as “threatened” under the ESA.
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