California’s Most Endangered Fish Having Worst Year Ever

by Chris Clarke
January 27, 2016

Delta smelt | Photo: USFWS

The good news is we were wrong last summer. The Threatened Delta smelt isn’t extinct, or at least it wasn’t in mid-January when the California Department of Fish and Wildlife found some in the western Sacramento Delta.

The bad news: CDFW’s mid-January trawls — referred to by the agency as Spring Kodiak Trawls, after the Kodiak nets used by biologists — found just a handful of the three-inch fish: four males and three females. That’s the lowest count for January since Kodiak trawling began in 2002: less than half the number found in 2015’s January trawl, and less than one-twentieth 2014’s numbers. The startlingly low January smelt census follows similarly low counts in late 2015: A total of six Delta smelt were found in the state’s Fall Midwater Trawls between September and December. The 2015 Fall Midwater Trawl count was the lowest on record as well.

That’s not good news for a fish that may well be the California species hit hardest by the ongoing drought. And that drought is just the capper: water exports, pollution, increasing water temperatures and competition from invasive species have all worked together to bring the Delta smelt to the edge of extinction.

Losing the smelt seemed increasingly inevitable even before the poor showing in January. “It seems to be about whether (smelt) are going to be extirpated in the wild in one, five or 10 years, not whether they have a real future in the system,” fisheries biologist Peter Moyle told the Stockton Record in late December.

The smelt, Hypomesus transpacificus, is found only in the San Francisco Bay Delta. There, it sticks to brackish water areas where freshwater from the Sacramento River and its tributaries mix with tidally driven seawater from the Golden Gate. Water diversions for agricultural and urban use reduce the amount of freshwater in the Delta, making much of the Delta region too salty for the smelt.

It makes sense that drought, which reduces the availability of freshwater in the system even further, would be really hard on Delta smelt. And since the smelt has a lifespan of a single year, a crash in population like this year’s runs a good chance of being permanent. Permanent, meaning extinction.

That’s extinction in the wild, mind you. UC Davis maintains a captive population of Delta smelt at its Fish Conservation and Culture Laboratory in the Delta town of Byron; that population numbered about 20,000 last year. (About the number that one 19th Century fishing boat could harvest in a single pull of its nets.) Some smelts from that lab are sent to the U.S. Fish and Wildlife Service’s Livingston Stone National Fish Hatchery north of Redding, where they serve as a vital backup.

Rearing Delta smelt in captivity is a crucial backup, and it’s not without its complications. The water’s salinity has to be carefully controlled, as does its temperature: too warm and the fish will suffer. Newly hatched smelts won’t eat commercially available fish food, so the facilities raise live food for them as well — mostly rotifers and brine shrimp.The fish are moved from tank to tank at the Fish Conservation and Culture Laboratory as they grow, and spawning is carefully managed among more than 200 separated populations of the fish in order to minimize inbreeding.

It’s a lot of work, and the smelt are a lot harder to raise than many other species of fish. Still, the breeding programs do constitute a hedge against the species’ extinction in the wild. But none of those captive-bred smelts will be put back in the wild anytime soon. As long as we continue to damage the smelt’s wild habitat, those captive-bred fish will stay safe in their tanks to keep the species going.

There’s a chance that this season’s heavy rains may offer a bit of a reprieve for the smelt: if El Niño continues to bring rain and snow to Northern California through March and April, that will mean additional fresh water in the Sacramento, and smelt spawning has historically spiked in wet years. But in order for the fish to spawn and create a new generation of Delta smelt, they have to be there in the first place. If a wet year allows the smelt in the Delta to triple their numbers from this year, that still leaves them perilously close to extinction.

But not this month. This month, there are still wild smelt in the Delta. Next month? Who knows?