Delta fish populations rebound, vindicating DOI scientists

“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.  

About the Authors

Doug Obegi

Senior Attorney, Water program

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