News of the week
Hatchery raised delta smelt released to the wild.
In the San Joaquin River Delta, close to the town of Rio Vista, conservationists have released hatchery grown delta smelt into the Sacramento River. This is the first time hatchery grown smelt have been released to the wild.
The work is being done by a consortium that includes 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, the U.S. Geological Survey, and UC Davis.
The release was inaugurated in mid-December of last year, with a release of 12,000 smelt. The more recent release, in February, raises the total of fish released to the delta to 40,000. Winter is the preferred time to release the delta smelt. That is when they migrate upstream to spawn. In summer, young smelt swim downstream to the brackish waters of the estuary.
The hatchery developed their methods of breeding and raising the delta smelt in captivity soon after the fish was listed as Threatened under the Endangered Species Act in the mid nineties. To keep a genetically diverse population, up to 100 smelt from the wild are brought in every year to mate with the captive bred fish. In recent times, it’s been impossible for the hatchery to get that number of smelt from the wild. In the winter of 2018-2019, the catch fell to 28 individuals. Last winter the hatchery caught just two smelt.
This release is not expected to bolster the population of the small fish. Rather, the fish are being released as a sort of trial to find the best way to reintroduce this species to their native waterways. The consortium is comparing the success rates for two release methods. One way is a direct approach, releasing the fish straight into the water. In the other method, the fish are held in cages in the delta for up to three days, allowing them to acclimate to their wild surroundings.
Delta smelt are small, Their slender bodies usually growing no longer than two or three inches, maxing out at around four and a half inches in some cases. They only grow in the San Francisco Estuary, leaving only when they complete their small migration upstream for spawning. Traveling from brackish estuary to freshwater and back to brackish waters, they are euryhalic, which means that they are able to tolerate a wide range of salinity. They feed on planktonic copepods, cladocerans, and amphipods.
During the early eighties, the little fish that smells like cucumbers were so common that fishermen trawling through Suisun Marsh would haul in nets thick with delta smelt. Just ten years later, the smelt was almost completely extirpated from its environment in the San Joaquin River Delta.
Natural forces, such as drought are working against the delta smelt. More so, it is the pumping of enormous amounts of water from the river delta that has decimated the smelt. The San Joaquin River Delta provides water to farms in the Central Valley and cities in the southern, drier portion of the Golden State.The delta fulfills the water needs of two-thirds of California’s population and is used to irrigate millions of acres of farmland.
Much of that farmland is in the Central Valley, which produces a staggering amount of food. In 2013 the output of the Central Valley’s farms came to $43.5 billion. For years, increased salinity (a natural outcome of irrigation), drainage problems, a long-standing drought, and other complications have jeopardized farming in the Central Valley. Federal studies concluded years ago that many of the farms would need to retire, and many farmers have begun to agree. Even still, when it comes time to assign blame to the farmers’ plight, fingers are pointed at the delta smelt. This narrative has been played like a fiddle by big business and the GOP. The delta smelt was talked about specifically as the George W. Bush administration sought to weaken the Endangered Species Act.
The San Joaquin River Delta is a marvel. One of the few “reverse” river deltas in the world—the riverlets converge to the mouth, instead of spreading out, as do the deltas of the Nile and Mississippi—the estuary is the largest in the western United States. In its natural state, the delta followed daily and seasonal fluctuations of tidal water and salinity. Its marshes providing food and an environment for waterfowl, elk, and even grizzly bears.
Now the expanse incorporates man-made channels. Five other fish species associated with the San Joaquin and Sacramento Rivers, including steelhead trout and Chinook salmon, have been declared Endangered or Threatened by California or the federal government.
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Gross, Jane. "A Dying Fish may Force California to Break its Water Habits." New York Times, Oct 27, 1991. ProQuest, https://www.proquest.com/newspapers/dying-fish-may-force-california-break-water/docview/428232164/se-2?accountid=8064.
Goode, Erica. "Fragile Delta is a Key Battleground in California's Water Wars: [News; Series]." New York Times, Jun 26, 2015. ProQuest, https://www.proquest.com/newspapers/fragile-delta-is-key-battleground-californias/docview/1691212111/se-2?accountid=8064.