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Delta fish populations rebound, vindicating DOI scientists

Doug Obegi

Posted October 12, 2011

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“Just add water.”  For several years, fishermen, conservationists, and scientists have argued that if we provide adequate freshwater flows to the Bay-Delta, native fish populations would begin to rebound.  In 2007, a federal court required pumping restrictions to protect native fisheries in the Delta, and this year, the CVP and SWP provided sufficient flows in September and October to restore habitat for delta smelt (what’s known as the Fall X2 action). 

Not surprisingly, it worked – fish populations rebounded.  Last week, the California Department of Fish and Game quietly announced that the September surveys for Delta fisheries showed a huge rebound for delta smelt, as well as substantial increases for most of the other species assessed by the survey.  The Fall Midwater Trawl survey provides the best estimate of the abundance of delta smelt and the September value of 50 was the highest level seen in more than a decade.  Indeed, this year’s September index was higher than the annual index (combined values of the Sept-Dec monthly indices) since 2005.  This big increase in the population of delta smelt is great news for a species that just a few years ago many biologists predicted might go extinct in the very near future. 

It also provides evidence that we can reverse fisheries declines and restore the health of the Bay-Delta estuary.  While the ongoing extensive monitoring and scientific studies will continue to refine our understanding of the relationships between flows, habitat and fish populations, I think this year’s results speak for themselves.  Delta smelt population abundance increased only after the protections of the 2008 biological opinion were implemented.  These results vindicate agency scientists who testified that providing adequate fall habitat (Fall X2) and reducing entrainment at the pumps would allow this native fish to begin to recover.  For the men and women at the Department of the Interior who have toiled under incredible political pressure for the past several years, this year’s September FMWT results show that these protections are paying off. 

We are grateful to the scientists at the Department of the Interior, DFG, and other state and federal agencies who have had to bear the brunt of these attacks; to the agency managers who have stood up for their scientists; and to their lawyers at the Department of Justice who have defended the agency from unjust attacks.  In particular, these data should put to rest the unjustified and unreasonable attacks on two Department of the Interior scientists, attacks that former federal court judge Oliver Wanger has acknowledged, “have been somewhat misconstrued and blown out of proportion,” and were made on “exceedingly limited grounds.”

We have a long way to go in restoring the Bay-Delta ecosystem and its imperiled fish.   But if we stay the course on implementing needed Delta protections, we’re hopeful that monitoring surveys will continue to show improvement in the population of delta smelt and other local species.  We also expect that this data will strengthen the resolve of the Department of the Interior to stand by its scientists and continue to implement the biological opinions to protect and restore the Bay-Delta estuary.  

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MikeOct 13 2011 01:42 PM

The high fish numbers detected during the trawl is no surprise. Months ago when individuals and groups were claiming the Delta pumps were killing millions of fish, biologists explained that the pump salvage was not unexpected because the weather conditions were producing the higher populations. Despite the claims of pushing certain fish species to extinction because of the pumps, the opposite has taken place.

Any attempt to portray X2 as a vindication of two federal scientists who were recently chastised by a federal judge is a fallacy. The scientists testified that Fall X2 needed to be moved in order to provide a greater habitat for fish. The judge rejected their testimony and declined to order the shifting of Fall X2. Contrary to the federal scientists, Fall X2 was not moved and the fish populations have rebounded.

As explained by biologists months ago, weather conditions experienced this year resulted in higher fish numbers. These conditions were the result of Mother Nature and the combined operation of the State Water Project and the Central Valley Project cannot duplicate these conditions.

Mike Wade
California Farm Water Coalition

Doug ObegiOct 13 2011 02:42 PM


You're not the only person who has misunderstood what the Court did this year with respect to Fall X2. A Fall X2 action is being implemented this year, and outflow has met the X2 requirements in the Biological Opinion since September 1; DWR has told the agencies that the X2 standard in the biological opinion will be met in the month of October as well, and November will probably come very close to meeting what was required in the BiOp. So it's simply not true that "Fall X2 was not moved." The Fall X2 study predicted that delta smelt populations would rebound, and that's what we're seeing. To use your words, Fall X2 was implemented, and the fish populations rebounded.

2006 was the last major wet year, but we didn't see a rebound like what we're seeing this year. And the spring numbers for delta smelt were much lower than these fall numbers, suggesting that it was actions in the summer and Fall (like the Fall X2 action) that caused the rebound in their numbers. Your comments about splittail populations and take at the pumps really aren't relevant to this conversation; for delta smelt, the requirements of the biological opinions on flows and pumping were met and delta smelt entrainment was low this year.

We don't know for certain whether and to what extent the Fall X2 action was responsible for the rebound in delta smelt numbers, but the initial indications are very encouraging and we'll know more next year. Science marches on.


Brandon MiddletonOct 13 2011 05:34 PM


I have to disagree with you. I think you are confusing the Fall X2 action (which is in the delta smelt biological opinion) with the Fall X2 location (which is simply a geographical point measured by salinty). The Fall X2 action mandates the Fall X2 location at 74 km east of the Golden Gate Bridge wet years such as this one. The Fall X2 action was enjoined about a month ago because, according to the Court, “[t]here is essentially no biological evidence to support the necessity of the specific 74 km requirement set to be triggered in this ‘wet’ water year.”

It was then recognized that the injunction could be suspended as a matter of course because the Fall X2 location was going to remain at 74 km under natural conditions. As DWR emphasized to the Court on September 8, “without the implementation of the Fall X2 Action this year, the monthly average for X2 in September will be 74 km and that the monthly average for October will be 75 to 77 km.” The Court subsequently agreed to suspend the injunction until October 15.

So it is a fortunate coincidence that the 74 km location was achieved without implementation of the Fall X2 action, allowing for the suspension of the injunction. The question is, had natural conditions been different and the X2 location begun to move significantly eastward, would implementing the Fall X2 action to keep the X2 location at 74 km make sense? Would the delta smelt suffer irreparable harm if this location were not maintained through the curtailment of water deliveries?

Of course, the Court has found that “there will be no irreparable injury by maintaining fall X2 at 79 kilometers” and that the federal government’s suggestion that “the failure to
implement X2 at 74 kilometers, that that’s going to end the delta smelt existence on the face of our planet is false [and] is outrageous.”


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