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Delta Smelt Hypomesus transpacificus


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Delta Smelt
© B. Moose Peterson/U. S. Fish and Wildlife Service

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Family: Osmeridae, Smelts view all from this family

Description 2-5" (5-12.5 cm). Elongate and fusiform, with a small adipose fin just ahead of the forked tail. Shiny and silvery overall, bluish above, with wide lateral stripe.

Endangered Status The Delta Smelt is on the U.S. Endangered Species List. It is classified as threatened throughout its range in California, where it occurs only in Suisin Bay and the Delta in San Francisco Bay, at the mouths of the San Joaquin and Sacramento Rivers. This once-abundant fish is said to have declined by 90 percent since the 1970s. Its decline can be attributed to the draining of water from the two rivers for agricultural and residential use. This has lowered the water level in the smelt’s habitat, altering the ecosystem and the natural balances within it. Pollution and the introduction of non-native species that compete for food and habitat has contributed to this fish’s diminished numbers.

Habitat Estuarine waters and upstream into rivers.

Range San Joaquin and Sacremento Rivers estuary, San Francisco Bay, California.

Discussion The fish are in the trout family, and like their larger relatives migrate upstream to spawn and generally die afterwards.