Delta Smelt (Hypomesus transpacificus)
– photo credit: US Fish & Wildlife Service
The little delta smelt is back in the headlines. An Alameda County judge has ruled that giant pumps operated by the Department of Water Resources are illegally killing delta smelt and Chinook salmon, two species protected under the California Endangered Species Act (CESA). He has given the state 60 days to obtain the proper permits or shut down the pumps.

I talked to our Senior Scientist, Tina Swanson, about the fish that’s been causing so much fuss. As she summed it up, “The delta smelt is a little fish at the center of a huge hurricane.”

The fish at issue is petite (generally 2-3 inches), steely blue and nearly translucent. Delta smelt live 1-2 years, feed exclusively on plankton, and, amazingly, smell like cucumbers. The species is endemic to the upper San Francisco Bay and the Delta, meaning it is found nowhere else on earth. Unfortunately, the place it calls home is a place in crisis. And that is cause for concern, even if you don’t happen to be a delta smelt.

The Delta– where the Sacramento and San Joaquin Rivers converge before flowing into the Bay– is the heart of the Bay watershed and the hub for much of the state’s freshwater supply. 2 in 3 Californians– some 23 million people– depend on the system for at least part of their water. (If you live in the East or South Bay, chances are you are one of them.)

The Delta’s troubles are manifold. Once a vast and ecologically abundant inland marsh, it was diked and channelized starting in the 1800s. Today, many of its islands have subsided as much as 20 feet below sea level behind aging levee systems, putting farms, homes, our water supply, and human lives at risk (think hurricane Katrina). The rivers flowing into the Delta have been dammed, and water quality suffers due to pesticides and other pollutants from Central Valley and Delta farms. Native species like the smelt are in steep decline, and invasives are taking over. And more and more people are moving into the Delta, building houses on land better suited for flood bypasses or tidal marsh restoration.

Then there are the giant pumps. They suck in water with the force of a large river, squashing the delicate smelt against– or pulling them right through– screens meant to keep them out of the facilities. Further, by extracting so much fresh water, we are altering the unique chemical composition of the system and disrupting the seasonal ebb and flow of salty and fresh water– natural rhythms that serve as vital cues for migration and spawning for the smelt and other species.

Once one of the Delta’s most common pelagic– or open water– fishes, today the delta smelt is thought by many scientists to be on the brink of extinction. In an effort to help save it, The Bay Institute has filed emergency petitions with federal and state agencies seeking to change the status of the species from threatened to endangered. We are also analyzing the effects of Delta water operations and promoting actions that could be taken to help the fish, such as limiting pumping in the early spring to protect vulnerable young smelt hatched during the winter.

The delta smelt has been described as an aquatic “canary in the coalmine”– a key indicator of the condition of the Delta and upper San Francisco Bay. Its disappearance is a sounding alarm bell of a system in crisis. Let’s hope this latest court ruling is enough to finally wake us up.

Ann Dickinson is Communications Manager for The Bay Institute (, a nonprofit research, education, and advocacy organization dedicated to protecting and restoring San Francisco Bay and its watershed, “from the Sierra to the sea.”

Little Fish, Big Crisis 23 April,2013Ann Dickinson

  • Desmond Bishop


    Great article, very informative. I hope this does serve as some sort of wake up call to the Bay Area residents.


  • Pingback: QUEST Science Blog - KQED » Keep focus on the Delta… with or without whales()


Ann Dickinson

Before moving to California almost five years ago, Ann served as Sally Brown Fellow in Environmental Literature at the University of Virginia, where she taught undergraduate seminars on literature and the environment and coordinated an ongoing reading series featuring nationally prominent nature writers. Prior to that, she spent a year as a research assistant at the Smithsonian Tropical Research Institute's field station on Barro Colorado Island, Panama, studying how young leaves defend themselves against herbivores.

Sponsored by

Become a KQED sponsor