SAVING LONGFIN SMELT

Longfin smelt live for several years, spawning in freshwater and inhabiting estuaries and nearshore waters, and even ranging out into the ocean. Usually growing from 3.5 to 4.3 inches as adults, these medium-sized fish are translucent silver on their sides and olive to iridescent pink on their back. Their most distinctive characteristic is their long pectoral fins, which give the species its common name.

Background

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. Due to poor management of California's largest estuary ecosystem, which has allowed excessive water diversions and reduced freshwater flow into the Bay, longfin smelt have undergone catastrophic declines. Longfin smelt abundance has declined more than 99% from 1980s levels, reaching record lows from 2007 to 2023.

Our Campaign

Formerly so common that they supported a commercial fishery in San Francisco Bay, longfin smelt were long treated by government agencies as undeserving of Endangered Species Act protection. But these fish are far from immune to the devastation of their habitat, and — as with delta smelt — their rapidly falling numbers are a bright-red flag. In 2007 the Center and other conservation groups petitioned for state endangered species protection for longfin smelt in California and federal endangered species protection for the San Francisco estuary population. In 2009 the California Fish and Game Commission voted to declare the smelt threatened under the state's Endangered Species Act. But the U.S. Fish and Wildlife Service repeatedly denied federal protection. After two petitions, six lawsuits, and 30 years of delay, the Center and San Francisco Baykeeper finally won endangered status for the San Francisco Bay population of longfin smelt in 2024. In 2025 the Service proposed to designate 91,630 acres of critical habitat for the San Francisco Bay population of longfin smelt in San Pablo and Suisun bays and the Delta.

Unsustainable water diversions from Central Valley tributary rivers for industrial agribusiness slash more than half the annual freshwater flow into the Bay — and more than 70% during the critical winter-spring period for longfin smelt. That causes perpetual drought-like conditions for longfin smelt and other native fishes. Despite these consequences, the state plans to divert even more fresh water from the Bay’s watershed through such projects as the Delta Conveyance Project and the proposed Sites Reservoir, which would further degrade Bay-Delta habitat. The Center and a coalition of conservation, fishing, and Tribal groups are suing and protesting water-rights applications to stop these damaging projects.

Check out our press releases to learn more about the Center’s actions for longfin smelt.