Alameda Creek Fish Then and Now
Fish communities in the Alameda Creek watershed have been studied by universities and the California Department of Fish and Game since the early 1900s. There is evidence Alameda Creek and its tributaries historically supported an impressive diversity of anadromous (migratory) cold-water fish, including steelhead trout, chinook salmon, Pacific lamprey, river lamprey and coho salmon in some years. Although there are no good records of the size of steelhead spawning populations or the distribution of spawning and rearing areas, the watershed likely supported one of the largest historical steelhead runs in the San Francisco estuary.
Construction of Calaveras Dam in the 1920s blocked access to many of the best tributaries for steelhead, and San Antonio Dam was constructed without provision for fish passage. Habitat restriction and degradation from water projects and other development related to urbanization caused substantial decline in the population of steelhead and salmon entering the watershed to spawn. In the 1970s, flood control and water diversion projects in the lower portion main stem Alameda Creek were approved and constructed without regard for anadromous fish passage. These structures completely blocked access to suitable spawning and rearing habitat in the system.
Although the native salmon runs have been lost, small numbers of wild steelhead continue to try to enter Alameda Creek regularly along with a few chinook salmon thought to be hatchery strays. Adult steelhead thought to be native to Alameda Creek have been documented in the flood control channel attempting to migrate upstream during winter spawning runs since 1997. There are several self-sustaining populations of resident rainbow trout in the upper parts of the watershed, including landlocked steelhead in Calaveras and San Antonio Reservoirs that are descendants of the original steelhead run. Plans are underway to remove or mitigate all migration barriers to allow successful re-establishment of a steelhead run in the creek by 2015.
A dozen other species of native freshwater fish have been collected in the watershed during the past century. Although some of these native fish may have been lost (such as speckled dace and riffle sculpin) and despite extensive urbanization, changes to the channel from flood control projects and construction of major dams, Alameda Creek still supports one of the best assemblages of native stream fishes in the San Francisco Bay region. In addition to common stream species (such as California roach, hitch, threespine stickleback, Sacramento sucker, Sacramento pikeminnow and prickly sculpin), rarer native fish such as hardhead, Sacramento blackfish, Sacramento perch and tule perch have been documented. San Francisco biologists have surveyed fish species distribution and population structure throughout the watershed on an annual basis since 2000.
Unfortunately, introduced exotic fish have increased in abundance and distribution within the watershed, with the potential for predation on or competition with native fish. Invasive fish in Alameda Creek include carp, white catfish, bluegill, smallmouth bass, largemouth bass, golden shiner, black bullhead, brown bullhead, mosquitofish, inland silverside, green sunfish, goldfish, black crappie and bigscale logperch.