Delta smelt

Appearance

Efforts to protect the fish from further decline and extinction have focused on limiting or modifying the large-scale pumping activities of state and federal water projects at the southern end of the estuary, thereby limiting water available to farming.

The delta smelt is an endangered slender-bodied smelt, about 5 to 7 cm (2.0 to 2.8 in) long, in the family Osmeridae.

Range and habitat

The delta smelt is endemic to the Sacramento–San Joaquin River Delta in California, where it is distributed from the Suisun Bay upstream through the delta in Contra Costa, Sacramento, San Joaquin, and Solano Counties. The delta smelt is a pelagic (lives in the open water column away from the bottom) and euryhaline species (tolerant of a wide salinity range). Historically, delta smelt were distributed from San Pablo Bay upstream to Sacramento on the Sacramento River and Mossdale on the San Joaquin River, that varied seasonally and with freshwater outflow.

Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.

Diet and breeding

The delta smelt is semelparous, living one year and dying after its first spawning. Their spawning occurs in spring in river channels and tidally influenced backwater sloughs upstream of the mixing zone where salt water meets fresh water.

Young delta smelt then feed and grow in the mixing zone before starting their upstream spawning migration in late fall or early winter. Endemic to the upper Sacramento-San Joaquin Estuary of California, it mainly inhabits the freshwater-saltwater mixing zone of the estuary, except during its spawning season, when it migrates upstream to fresh water following winter "first flush" flow events (around March to May).

In crisis

It is listed as a federally threatened species under the Endangered Species Act of 1973. Even so, these efforts have not prevented the species from becoming functionally extinct in the wild. It primarily inhabits low-salinity waters and is critically endangered due to habitat loss and water management practices.

Efforts to conserve and restore the delta smelt population have been ongoing for decades, as this species continues to face significant threats from habitat degradation, climate change, and water management practices. Multiple state and federal agencies, in partnership with universities and conservation organizations, have implemented a variety of strategies aimed at preventing the extinction of this critically endangered species.

Delta smelt is Critically Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.

Sources

Written for this catalog from the English Wikipedia article on Delta smelt, Wikidata item Q631383. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.