The Sacramento splittail is a hearty minnow native to the upper San Francisco Estuary and the Central Valley in California. It once swam in lakes and rivers throughout the Central Valley and in the Sacramento-San Joaquin River Delta, but massive water diversions and alteration of important spawning and rearing habitat have driven this formerly common species to near extinction. Remnant populations of splittail in the Delta require adequate freshwater outflow and periodic floodplain inundation.

ENDANGERED SPECIES ACT PROFILE

PROTECTION STATUS: Delisted

YEAR PLACED ON LIST: Threatened 1999, delisted 2003

CRITICAL HABITAT: None

RECOVERY PLAN: None

RANGE: Formerly occurred in lakes and rivers throughout the Central Valley and in the Sacramento-San Joaquin River Delta; now largely restricted to the Delta, Suisun Bay, Suisun Marsh, and Napa Marsh

THREATS: Reduced water outflow and changed estuarine hydraulics due to dams and water diversions, modification of spawning habitat by wetland draining and filling, climatic change, toxic substances, introduced species, and fishing

POPULATION TREND: Formerly common in the Sacramento, San Joaquin, Feather, and American rivers, the splittail is extinct in all but a fraction of its former range. Populations in the minnow’s constricted range in the Delta are estimated to be only 35 to 60 percent as abundant as they were in 1940; the percentage decline over the species’ historic range is much greater. Splittail numbers in the Delta have declined steadily since 1980, and in 1992 numbers declined to the lowest on record. Population levels appear to fluctuate widely from year to year.