Tuesday June 9, 2026
Maven’s Notebook —
Five years ago, a multi-agency team launched an effort to restore Delta smelt, a finger-sized iridescent fish unique to California’s Sacramento-San Joaquin Delta. Delta smelt were once among the most common fish in the region but are now critically endangered due to a suite of threats including loss of suitable habitat and food.
As Delta smelt dwindled, a refuge population was established a quarter century ago as a hedge against extinction at the University of California, Davis Fish Conservation and Culture Laboratory near Byron. Releases of hatchery Delta smelt into the wild began in 2021. Additional partners in this effort include the U.S. Fish and Wildlife Service, the California Department of Fish and Wildlife, the California Department of Water Resources, the U.S. Bureau of Reclamation and the U.S. Geological Survey.
Delta smelt are famously sensitive to their environment―including temperature, water quality, and physical disturbance―and must be handled with care. Initial experimental releases involved transporting the fish from the UC Davis hatchery to the Delta in 20-gallon carboys. While this method was intended to be easy on the smelt, it took a crew all day to release just 6,400 of them.