Delta smelt, pictured here, have declined in abundance by more than 99% since their listing in 1993 (Photo provided by DWR)

By Scott Hamilton, President, Hamilton Resource Economics

The Sacramento-San Joaquin Delta with the San Joaquin River highlighted in dark blue (Graphic from U.S. Geological Survey)

Driving north to Sacramento or San Francisco from Bakersfield, you don’t see much of the Sacramento-San Joaquin Delta – that area east of Antioch where the two rivers converge, draining the Central Valley of California as it has for centuries, and the sole home of delta smelt. It is picturesque now, dotted with communities and piers and farmland that fills the Delta Islands. How different now than what it must have looked like before people of European decent started to settle California – hundreds of thousands of acres of tidal marsh lands, countless dendritic dead-end sloughs, tall tules covering intertidal islands. It must have been easy for novices to those water ways to get lost in there. But the delta smelt apparently had no problem. They would have traveled many miles during their one-year life, moving west during periods of high flows and east after the snow had melted and the floodplains drained. They probably moved very far east in drought years to stay in that Goldilocks range where the water was just right – not too salty and not too fresh – a habitat requirement for delta smelt.

Delta smelt have been a tricky fish to conserve. Added to the endangered species list by state and federal agencies in 1993, the numbers of delta smelt sampled are now less than 1% of the number at the time that they were listed. With 28 years of state and federal protection, the population has diminished by more than 99%. So, the agencies charged with protecting them have taken some extreme measures to conserve the fish – some of which have been very controversial. 

One such measure is called the Fall X2 Action which was included in the 2008 Biological Opinion governing water project operations. The action calls for more water to flow out to the ocean in the years that are wetter than normal. The water cost, when implemented, typically exceeds 600,000 acre-feet. That is more than the capacity of Lake Isabella when it is full to the brim. The original thinking behind the action was shaky at best and the defense of it has changed over time. Initially the action was based on an unpublished study indicating that the action increased survival rates during the fall. That original analysis was flawed, and while the paper ended up being published, the part suggesting population benefits was removed from the manuscript and never published. 

So, there is no longer a need to implement the action, right? Wrong. Suisun Bay used to be a popular place for delta smelt but the reduced flows were making it too salty. Increasing flows would move the salty water further west and reopen Suisun Bay to delta smelt, vastly increasing the volume of water available to them, or so the argument went. The idea that delta smelt needed more space was itself unproven. The other problem is that delta smelt need to eat. Well, in 1987, a small mollusk, the Asian clam moved into Suisun Bay. A prolific feeder, it forever changed the food web. Now, food for delta smelt in Suisun Bay in the fall is sparse, not nearly sufficient to sustain delta smelt. So why try to move the fish there? There is no evidence to suggest the fish did move there as a result of the action. The food supplies were better upstream. In fact, what the action likely did was move the tiny crustaceans that delta smelt eat from the lower Sacramento River, where they were concentrated, downstream to Suisun Bay where they were diluted and the mortality rates were higher–which actually make conditions worse for the bulk of delta smelt still upstream. Scorecard for the action: improved salinity downstream which the fish did not need, likely moved a small percentage of the fish, and diminished food supplies.

This photo of Suisun Marsh provides an indication of what the historic Delta may have looked like (Photo: Wayne Hsieh)

So, there is not a good reason to implement the action, right? Wrong, again. Agency staff now argue that water exports from the Delta in the fall result in a degradation of habitat – another thing not allowed under the Endangered Species Act. So the argument is that Suisun Bay, an area that is already unsuitable for the fish, is degraded due to operations of exports? That logic is baffling. Interestingly, the water projects don’t reduce the supply of water to the Delta in the fall, they increase it. Before the construction of reservoirs in the Sacramento Valley, conditions would have gotten pretty salty in the Delta in dry years. Now cities lining the Delta take their water from the Delta. The water needs to be kept fresh and so water is released from the reservoirs both for conveyance south and to meet water quality requirements in the Delta that are set by the State Water Resources Control Board. This preserves low salinity conditions downstream, not degrades them. 

A group of 23 scientists just released a 265 page1 study considering the response of delta smelt to increased outflow in 2017. That study found no support for increased feeding success or growth rate of delta smelt in Suisun Bay. The logic in the above paragraphs would have led to the same conclusion. Of concern though, a two-page summary of the report was issued containing this main finding: “High fall outflow is necessary, but not sufficient to provide favorable conditions for delta smelt.” As Paul Weiland notes2, the statement is remarkable because nowhere in the report does the IEP conclude that high through-Delta outflow is “necessary” to provide favorable conditions for delta smelt. One might conclude the “finding” was written to perpetuate the indefensible. 

There are now at least five published, peer reviewed manuscripts in scientific journals from five different sets of authors that have not been able to demonstrate a benefit of the Fall X2 action to delta smelt. It is understandable that conservation managers needing to protect delta smelt want to err on the side of being overprotective to save the species. But there must be honest adherence to rigorous science. There must be some ability to say, “ Okay, this action doesn’t seem to be working, let’s try something else.” But instead, a Fall X2 action was included again in the 2019 Biological Opinion. The action was last implemented in 2019. The State Water Contractors estimated that quantity of water lost to the action that year was 1.2 million acre-feet. If that water had been kept in the reservoirs for the dry year of 2020 or this year’s drought, and let’s say it is worth $1,000 per acre foot in these dry times, that is roughly $1.2 billion worth of water. People would question if that was worth it even if there was a proven benefit to the fish, but there is no demonstrated benefit to the fish, just opinions lacking scientific support. With wells going dry, farmland being fallowed, and less income for working families in communities throughout the Valley, can we not ask agency leadership to reexamine the action with an open mind? 

The author has coauthored five manuscripts on delta smelt which have been published in national and international scientific journals. He can be contacted at:

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