Longfin smelt were once one of the most abundant open-water fishes in the San Francisco Bay Estuary — commercially important fish, key to the Bay food web. Today the species’ numbers have plummeted to record lows in the Bay-Delta, and it’s nearing extinction in other northern California estuaries. Thanks to poor management of California’s largest estuary ecosystem, which has allowed excessive water diversions and reduced freshwater flow into the Bay, the longfin smelt has undergone two catastrophic declines in just 20 years.

ENDANGERED SPECIES ACT PROFILE

PROTECTION STATUS: Not listed

PETITIONED: 2007

RANGE: Estuaries along the Pacific  Coast, from San Francisco Bay to Alaska

THREATS: Degraded environmental conditions in the Bay-Delta Estuary caused by massive water diversions that reduce freshwater inflow; loss of fish at agricultural, urban, and industrial water diversions; direct and indirect impacts of nonnative species on food supply and habitat; and lethal and sub-lethal effects of pesticides and toxic chemicals

POPULATION TREND: Longfin smelt may already be extinct in some smaller estuaries in northern California, and the San Francisco Bay-Delta population has experienced two catastrophic population plunges in two decades. So far, throughout the 2000s, the Bay-Delta longfin smelt population has been at just 3 percent of levels measured fewer than 20 years ago, and numbers in this estuary dropped to record lows from 2004 to 2007.