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Delta Smelt

The endangered Delta smelt is a 3-inch fish found only in the Sacramento-San Joaquin Delta. It is considered especially sensitive because it lives just one year, has a limited diet and exists primarily in brackish waters (a mix of river-fed fresh and salty ocean waters that is typically found in coastal estuaries).

Along with other fish, smelt populations declined because of a combination of entrainment in pumping facilities, poor water quality, limited food supply, lack of habitat and nonnative species that compete for food.

The smelt’s tendency to swim near the State Water Project and Central Valley Project export pumps in the South Delta has complicated water deliveries to farmers and cities.

Surveys conducted in 2009 showed the smelt is close to extinction. Two other fish species, longfin smelt (a native fish) and striped bass (an introduced species) fell to their second-lowest measures ever.

For more than 40 years, fish counts have occurred from September to December to measure the health of a half-dozen key Delta fish species. The numbers show that since about the time the big Delta export pumps started operating, the numbers for all those fish including the smelt have fallen dramatically.

Delta Smelt and the Environment

The fate of the Delta smelt is part of a continuing controversy over the fate of the faltering Delta ecosystem—the hub of the state’s water supply. Many lawsuits have been filed in a dispute over the amount of water that can be safely exported through the region.

In 2005, the U.S. Fish and Wildlife Service issued a biological opinion on the effects of the coordinated operations of the state and federal projects on Delta smelt, stating that Delta export pumping operations would not jeopardize the continued existence of the fish. Environmental groups challenged the opinion, and in May 2007 federal Judge Oliver Wanger ruled that the biological opinion was faulty in its assumptions and needed to be performed again [see also Wanger Decision].

In November 2009, environmentalists filed two lawsuits against the U.S. Fish and Wildlife Service for failing to protect the Delta smelt and the longfin smelt.

Today, there are court-ordered pumping restrictions on exporting water from the Delta to minimize effects on Delta smelt and other species.

In 2009, the Delta smelt was designated as endangered by California.

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