The tiny delta smelt is one of the best indicators of environmental conditions in the San Francisco Bay-Delta, an ecologically important estuary that is a major hub for California’s water system — and an ecosystem that is now rapidly unraveling. The “smeltdown in the Delta,” as the extinction trajectory of delta smelt is known, has left the once-abundant species in critical condition due to record-high water diversions, pollutants, and harmful nonnative species that thrive in the degraded Delta habitat.

This smelt’s catastrophic decline is a warning that we may lose other native Delta fish that have fallen to alarmingly low levels as well, such as longfin smelt, salmon, and sturgeon. In fact, the delta smelt is only one of 12 of the original 29 indigenous Delta fish species that have been eliminated entirely from the area or that are threatened with extinction. An extinction risk analysis in 2006 warned that the Delta smelt could go extinct within 20 years.

In 2007, when too few smelt were found during surveys to even calculate fish numbers, it was clear that the species was nearing extinction. Because federal and state agencies are failing to address the ecological problems in the Delta — moving forward with plans for water diversions and storage projects that will increase threats and further degrade Delta habitat — the Center is working to ratchet up protections for this species. A Center petition spurred the California Fish and Game Commission to upgrade its state protection status from threatened to endangered; we’ve also sued the U.S. Fish and Wildlife Service to achieve uplisting on the federal level.

The Delta habitat for delta smelt is polluted with often-lethal concentrations of herbicides and pesticides discharged and transported from California’s Central Valley into the fish’s estuary home. Toxic pulses of pesticides have been documented in the Delta during critical stages in fish development, and pesticides have been implicated in the recent collapse of the delta smelt population. The Center is challenging the Environmental Protection Agency’s registration and authorization-for-use of 46 toxic pesticides in and upstream of habitats for San Francisco Bay Area endangered species, including the Delta smelt; we continue to monitor and oppose harmful chemical pesticide use in California through our Pesticides Reduction Campaign.