The tiny, controversial Delta smelt | Photo: USFWS
California's most controversial threatened species, the Delta smelt, has never been closer to extinction, but a state agency that could help it with the stroke of a pen is failing to do so.
That's according to a group of environmental organizations that are pleading with the State Water Resources Control Board (SWRCB) to force aqueduct operators to leave enough fresh water in the Delta for the smelt.
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The Delta smelt, a three-inch fish that once numbered in the millions in the Bay Delta area, is in trouble for many reasons. Invasive species increasingly compete with smelts for food. Other invasive species eat the smelts. Pollution from much of California eventually drains into the Delta, where it can injure smelts and other wildlife.
But the biggest problem facing the Delta smelt is, at least in an engineering sense, the easiest one to end: the giant pumps that suck Delta water into the federal Central Valley Project and the State Water Project. The pumps have several effects on the Delta ecosystem, but most critically for the smelt they reduce the amount of fresh water flowing through the Delta into the Bay. That lets seawater come farther into the Delta at high tide. And that is bad for the Delta smelt, which thrives only in a relatively narrow range of salinity. The smelt stick to a slightly salty mixing zone where there's about 17 gallons of freshwater for every gallon of saltwater.
Without diversions, that mixing zone shifts with the tides and the seasons, but the smelts can generally cope with that. With diversions, especially in a drought year, the mixing zone moves far inland, drastically narrowing the band of salinity acceptable to the Delta smelt.
Why is the threat from pumping easy to end? Turn off the pumps, and in a short time whatever water is available in the Sacramento starts flowing out to the Bay again. Of course, thats only easy if you ignore the politics.
Earlier this month, the Natural Resources Defense Council (NRDC), Defenders of Wildlife, and the Bay Institute sent a letter to SWRCB urging the agency to enact emergency regulations requiring the federal Bureau of Reclamation (BuRec) and the California Department of Water Resources (DWR) to cut summer pumping of Sacramento River water into the aqueducts of the Central Valley Project and the State Water Project in order to protect the smelt. The groups, which charge that SWRCB is legally obligated to protect the smelt and other threatened species in the Bay and Delta, wants the Board to force the aqueduct operators to reduce pumping until the end of September to protect the Delta smelt's brackish habitat.
So far the Board hasn't acted, despite pleas by state and federal wildlife agencies for increased water for the smelt. NRDC and the other groups are essentially asking the Board to follow the law. We know what to do to save the Delta smelt, said Kate Poole, a senior attorney at NRDC who directs the organization's Wildlife and Water program. We just need to take steps to do it.
The Delta smelts fate is in our hands. | Photo: USFWS/John Ridilla
The SWRCB is legally required to protect the Delta smelt under the California Endangered Species Act; the fish is on the state's Endangered list. The Delta smelt was also listed as Threatened under the federal Endangered Species Act in 1990; an attempt to downgrade its status to Endangered failed a few years back, when the U.S. Fish and Wildlife Service placed the smelt on its Warranted but Precluded list. That means USFWS agrees the Delta smelt ought to be listed as Endangered, but other species in more trouble are ahead of it in line.
It's hard to imagine how much more trouble a species could be in without already being extinct.
Precluded or not, the Delta smelt has never needed the water more. Its numbers have dropped catastrophically in the last two years, and fisheries biologists are holding meetings at which they ask whether the smelt's extinction is inevitable.
Until this year, Delta smelt population estimates have been very rough guesses. Smelts are hard to count: they're small, they're distributed throughout a maze of channels, sloughs and shallows, and they prefer murky, sediment-laden water. Biologists have historically conducted a series of sampling trawls throughout the year, counted the smelts in the nets, and then released those numbers - and how many smelt went unsampled was more or less anyone's guess.
But a new set of mathematical models developed by statistician Ken Newman now allows biologists to take the number of fish sampled in trawls, the amount and quality of available habitat, and other factors to calculate more reliable estimates of smelt numbers. Using historic trawl results gave researchers a glimpse into how the actual population of smelts has changed over the decades. And doing so revealed a stark recent decline for the Delta smelt. In early 2015, the U.S. Fish and Wildlife Service estimates, there were around 112,000 adult Delta smelt remaining in the Delta, an all-time low.
By mid-2016, that had dropped to around 13,000 Delta smelt.
The decline is stark enough, and the ongoing drought bad enough, that on August 2 BuRec and DWR asked the Fish and Wildlife Service to redraft a controversial document required by the Federal Endangered Species Act governing how the two agencies must operate their respective aqueducts to protect the smelt. That document, known as a Biological Opinion or BiOp, details restrictions on how many smelts the projects are allowed to harm in the course of normal operations, and measures the agencies must take to reduce that harm.
From the Sacramento River to the Mojave Desert via the California Aqueduct | Photo: Raymond Shobe, some rights reserved
That's not a step the aqueduct operat
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The tiny, controversial Delta smelt | Photo: USFWS 
