Southern California Coastal–Baja California is a

freshwater ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of l ...

in Western North America. It covers portions of central and southern California and west of the Coast Ranges as well as most of

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

's Baja California Peninsula, extending from the southern end of

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area and its major city at the south of the bay, San Jose. San Francisco itself is further north along the coast, by ...

to the southern tip of the Baja California Peninsula."Southern California Coastal - Baja California". Freshwater Ecoregions of the World. Accessed 14 September 2021

/ref>

Geography

The rivers and streams are mostly short and not very large, and run from origins in the mountains to the sea. The climate ranges from semi-humid to arid, and rainfall is highly seasonal and can be irregular, so many streams have big seasonal variations in flow, or are intermittent. The ecoregion has an area of . 76% of the ecoregion is in Mexico's states of

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

and Baja California Sur, and 24% is in California. Elevations range from sea level to over 3300 meters. The ecoregion includes the western slope of the

Santa Lucia Mountains The Santa Lucia Mountains (sæntə luˈsiːə) or Santa Lucia Range is a rugged mountain range in coastal central California, running from Carmel southeast for to the Cuyama River in San Luis Obispo County. The range is never more than from ...

in central California, the seaward slopes of the

Transverse Ranges The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa ...

and northern Peninsular Ranges in Southern California and Northern Baja California, and both the western and eastern (Pacific and

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

) sides of the Peninsular Ranges on the Baja California Peninsula. It also includes the

Channel Islands of California The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. The four Northern Channel Islands are part of the Transverse Ranges geologic province, ...

, and

Cedros Island Cedros Island (''Isla de Cedros'', "island of cedars" in Spanish) is an island in the Pacific Ocean belonging to the state of Baja California, Mexico. The dry and rocky island had a population of 1,350 in 2005 and has an area of which include ...

off the western coast of Baja California. Larger rivers include the

Santa Ynez River The Santa Ynez River is one of the largest rivers on the Central Coast of California. It is long, ArcExplorer GIS data viewer. flowing from east to west through the Santa Ynez Valley, reaching the Pacific Ocean at Surf, near Vandenberg Space Fo ...

Santa Barbara County Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barba ...

, the

Ventura River The Ventura River, in western Ventura County in southern California, United States, flows from its headwaters to the Pacific Ocean. The smallest of the three major rivers in Ventura County, it flows through the steeply sloped, narrow Ventura V ...

Ventura County Ventura County () is a County (United States), county in Southern California, the southern part of the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 843,843. The largest city is Oxnard, California ...

, the Santa Clara River in

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...

and Ventura counties, and the

, San Gabriel, and Santa Ana rivers in the

Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east-west trending chains of mountai ...

.Howard, J., and C. Revenga (2009). "California’s freshwater biodiversity in a continental context". Science for Conservation Technical Brief Series. The Nature Conservancy of California. San Francisco, CA. 29 pp + Appendices. Accessed 18 September 2021

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Fauna

Fish species endemism, endemic to the ecoregion include the Santa Ana sucker (''Catostomus santaanae''), California killifish (''Fundulus parvipinnis''), Peninsular clingfish (''Gobiesox juniperoserrai''), and Baja California killifish (''Fundulus lima''). Two subspecies of

three-spined stickleback The three-spined stickleback (''Gasterosteus aculeatus'') is a fish native to most inland and coastal waters north of 30°N. It has long been a subject of scientific study for many reasons. It shows great morphological variation throughout its ra ...

(''Gasterosteus aculeatus'') are endemic to southern California – the unarmored threespine stickleback (''G. a. williamsoni'') and the Santa Ana stickleback (''G. a. santaeannae''). Anadromous

steelhead trout Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and ...

(''Onchorhynchus mykiss'') are found some southern California streams. The ecoregion is the southern limit of their range, and the Southern California steelhead populations are genetically adapted to warmer water than most steelhead and salmon species. The San Pedro Mártir trout is endemic to the

Sierra San Pedro Mártir Sierra (Spanish for "mountain range" and " saw", from Latin '' serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nieves, a mountain rang ...

in northern Baja California. Some authorities consider the San Pedro Mártir trout a separate species (''Onchorhynchus nelsoni''), while others consider it a subspecies of steelhead (''Onchorhynchus mykiss nelsoni'').Kurlansky, Mark (2020). ''Salmon''. Patagonia, Ventura CA.

References

{{DEFAULTSORT:Southern California Coastal-Baja California Freshwater ecoregions Ecoregions of California Ecoregions of Mexico Drainage basins of the Pacific Ocean