U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Kids' Species Information

Delta Smelt

Photo by B. Moose Peterson, USFWS

Delta Smelt


Photo, Delta smelt, FWS photo

Photo: USFWS

Threatened. This means that we are worried about the species but that it is not about to go extinct right now. However, during the last few years the number of Delta smelt has declined steeply.


Delta smelt are slender fish. They are about 5.0 to 7.0 cm long. (about 2 to 3 inches) They have a steely blue sheen on the sides. They almost seem translucent. They live together in groups called schools. Most live only one year.


Small aquatic animals, especially tiny shrimp-like animals called copepods.


Delta smelts can tolerate a wide range of saltiness in the water. But they spend most of their time in water with 2 parts salt to 1000 parts water.


Delta smelts spawn in shallow, fresh or slightly brackish water. They swim upstream from where they usually hang out. Spawning happens in the spring.


Larger fishes. The non-native striped bass and largemouth bass are threats to the Delta smelt.

American Indians once caught Delta smelt for food. But now days people do not fish for them.


Delta smelt are found only from the Suisun Bay upstream through the Sacramento/San Joaquin River Delta.


Reduced water flow. Smelt getting trapped in water pumps and power plant intakes. Changes in food supply. Water contamination. Competition and predation from non-native species.


Be careful what you pour down sinks. Remember that it will end up in your community's water. Do not release exotic fish into streams. Find out why.

See What You Can Do to Help Wildlife and Plants (201 KB PDF) for more ideas.

Photo Credit: U.S. Fish & Wildlife Service

Words to Learn

Biologists call the Delta smelt Hypomesus transpacificus. Scientific names are in Latin or Greek.

Delta smelts are in the Osmeridae (smelt) family.

Spawning - fish reproduction. The females release eggs into the water. Males release sperm to fertilize them.

Salinity - the amount of mineral salts dissolved in water. Saline - salty water. Ppt - parts per thousand.

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Last updated: November 29, 2017