SACRAMENTO COUNTY, Calif. — Scale-covered delta smelt fish were abundant in regions like the San Joaquin River and the Sacramento River throughout the 1970s and 1980s — but this is no longer the case.
The small fish was deemed "critically endangered" by the International Union for Conservation of Nature in 2012, and the population has decreased ever since.
A recent survey from the California Department of Fish and Wildlife noted the agency failed to catch any delta smelt in 2022 despite 61 sampling days between September and December.
Even the 12,942 marked adult delta smelt they released into the Sacramento River near Rio Vista in November failed to turn up in any sampling the agency ran on the region in December.
"While [the survey] did not catch any Delta Smelt, it does not mean there were no smelt present, but the numbers are very low and below the effective detection threshold by most sampling methods," said a California Department of Fish and Wildlife spokesperson.
There yet to be any catches of delta smelt in the agency's Fall Midwater Trawl Survey since 2017.
Continued threats to the species of small fish are "multiple and synergistic" according to the agency. They include:
- Reduction in freshwater outflows
- Entrainment losses to water diversion
- High outflows
- Changes in food organisms
- Toxic substances
- Disease, competition, and predation
- Loss of genetic integrity
- The University of California, Davis Fish Conservation and Culture Laboratory maintains a genetically diverse population of Delta Smelt in culture.