page_title: San Francisco Bay Area
section_title: Marine wildlife
hierarchical_section_title: San Francisco Bay Area / Geography / Ecology / Marine wildlife
caption_attribution_description: English: Photograph of yearling beaver.
context_page_description: The San Francisco Bay Area, popularly referred to as the Bay Area or simply the Bay, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. While the exact boundaries of the region are variously defined, the Bay Area is defined by the Association of Bay Area Governments to include the nine counties that border the aforementioned estuaries: Alameda, Contra Costa, Marin, Napa, San Mateo, Santa Clara, Solano, Sonoma, and San Francisco. Other boundaries may exclude parts of or even entire counties, or expand the definition to include neighboring counties that do not border the bay such as San Benito, San Joaquin, and Santa Cruz.
  Home to approximately 7.75 million people, Northern California's nine-county Bay Area contains many cities, towns, airports, and associated regional, state, and national parks, connected by a complex multimodal transportation network. The larger combined statistical area of the region, which includes fourteen counties, is the second-largest in California, the fifth-largest in the United States, and the 41st-largest urban area in the world with 9.67 million people.
context_section_description: The Bay Area is home to a diverse array of wildlife and, along with the connected San Joaquin River Delta represents one of California's most important ecological habitats. California's Dungeness crab, Pacific halibut, and the California scorpionfish are all significant components of the bay's fisheries. The bay's salt marshes now represent most of California's remaining salt marsh and support a number of endangered species and provide key ecosystem services such as filtering pollutants and sediments from the rivers. Most famously, the bay is a key link in the Pacific Flyway and with millions of shorebirds annually visiting the bay shallows as a refuge, is the most important component of the flyway south of Alaska. Many endangered species of birds are also found here: the California least tern, the California clapper rail, the snowy egret, and the black crowned night heron.
  There is also a significant diversity of salmonids present in the bay. Steelhead populations in California have dramatically declined due to human and natural causes; in the Bay Area, all naturally spawned anadromous steelhead populations below natural and manmade impassable barriers in California streams from the Russian River to Aptos Creek, and the drainages of San Francisco, San Pablo, and Suisun Bays are listed as threatened under the Federal Endangered Species Act. The Central California Coast coho salmon population is the most endangered of the many troubled salmon populations on the west coast of the United States, including populations residing in tributaries to the San Francisco Bay. Industrial, mining, and other uses of mercury have resulted in a widespread distribution of that poisonous metal in the bay, with uptake in the bay's phytoplankton and contamination of its sportfish.
  Aquatic mammals are also present in the bay. Before 1825, Spanish, French, English, Russians and Americans were drawn to the Bay Area to harvest prodigious quantities of beaver, river otter, marten, fisher, mink, fox, weasel, harbor and fur seals and sea otter. This early fur trade, known as the California Fur Rush, was more than any other single factor, responsible for opening up the West and the San Francisco Bay Area, in particular, to world trade. By 1817 sea otter in the area were practically eliminated. Since then, the California golden beaver has re-established a presence in the Alhambra Creek. The North American river otter which was first reported in Redwood Creek at Muir Beach in 1996, has since been spotted in the North Bay's Corte Madera Creek, the South Bay's Coyote Creek, as well as in 2010 in San Francisco Bay itself at the Richmond Marina. Other mammals include the internationally famous sea lions who began inhabiting San Francisco's Pier 39 after the 1989 Loma Prieta earthquake and the locally famous Humphrey the Whale, a humpback whale who entered San Francisco Bay twice on errant migrations in the late 1980s and early 1990s. Bottlenose dolphins and harbor porpoises have recently returned to the bay, having been absent for many decades. Historically, this was the northern extent of their warm-water species range.
caption: A California golden beaver in Alhambra Creek in Martinez
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