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 Oregon 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.