Delta Smelt Q & A

Top Questions and Answers

Q: What is the current status of the Delta Smelt?

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A:The relative abundance of Delta smelt has reached very low numbers for a small fish in an ecosystem the size of the Bay-Delta. Record-low abundance reflects decades of habitat change, competition and predation from non-native species and multiple years of extreme drought. We estimated that there were 48,000 adult Delta smelt based on survey data from January and February 2017. The 2017 estimate is much higher than the estimate 16,000 adult Delta smelt in early 2016. This represents the first year-to-year increase in adult numbers just before spawning season since 2012.

The historically low numbers of Delta smelt is emblematic of an ecosystem under duress and why we have also seen significant declines in many of the native fish species that call the delta home during their life cycles.

The historically low numbers of Delta smelt is emblematic of an ecosystem under duress and why we have also seen significant declines in many of the native fish species that call the delta home during their life cycles.

Q: Does the USFWS now have the ability to estimate population numbers of Delta Smelt?

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A: Yes, we can estimate population numbers using data from consistent survey points and a complex set of calculations for the Delta. While it is impossible to know the exact number of Delta Smelt or any fish currently in the Delta, the Service uses data from the California Department of Fish and Wildlife's Spring Kodiak Trawl to calculate the best estimates of how many adults were alive at the start of each spawning season in January and February. The estimates have uncertainty—they are not exact numbers, but rather a range of likely numbers.

Q: Why is it difficult to estimate population numbers?

A: It is not possible to survey the entire Delta. There are differences in how "catchable" the fish are at different times and places, and we are unable to tag large numbers of small fish like Delta Smelt without killing them. The Service continues to work with other agencies to find methods that will result in improved confidence in population estimates of adult Delta Smelt.

Q: It's still estimated there are several thousand Delta Smelt in the system. Why, then, is the situation so dire?

A: The current population estimates are alarmingly small for a fish that only lives for one year in a body of water as large as the Bay Delta. Future projections are lower when considering only about half of the population estimate are females that may reproduce to create next year's population. Ensuring survival of this year's offspring is critical to the future existence of the species.

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Q: What are the overall trends for Delta Smelt populations?

A: Estimates for Delta Smelt since 2002 have varied between the current low and 623,000. The overall trend is downward. Delta Smelt rapidly declined between 2012 and 2013, and then again between 2015 and 2016.

Q: Are Delta Smelt going extinct?

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A: We are not able to determine when or if Delta Smelt will go extinct, but we are concerned about the species' ongoing decline. Delta Smelt abundance indices have trended downward since the early 1980s and are now at their lowest numbers ever recorded.

Q: Isn't Delta Smelt just a bait fish? Why should we protect them?

A: Delta smelt are considered an "indicator" species used to gauge the overall health of the Delta's aquatic environment. As the smelt fares so fares the Delta. When the smelt aren't doing well, the entire ecosystem suffers, as is the current situation. There are many prominent species dependent on the health of the Delta ecosystem. Others species that rely on the Delta have also seen steep declines in recent years include multiple runs of Chinook salmon, steelhead, longfin smelt, green sturgeon, and many others. Effectively restoring these fish populations will require restoring the Bay-Delta ecosystem. We can't do one without the other. A healthier, more resilient Bay-Delta ecosystem will better serve all the important functions of this vital resource including agriculture, water supply, habitat, recreation, and commerce.

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Declines of species like Delta Smelt indicate that the ecosystem is stressed and that, at some point, it may no longer provide recreational and commercial goods and services the people of California expect. The Delta Smelt is an essential part of the complex ecosystem of the Bay-Delta estuary.

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Q: If the Delta Smelt weren't listed under the ESA, would water users south of Delta get their full contract amounts?

A: Not necessarily. Only in the wettest of years do all water users south of the Delta receive their full contract amounts. There are two federal biological opinions as well as the State Water Resources Control Board's Water Rights Decision D-1641 that can influence operations of the State and Federal water projects. The Service issued its biological opinion for Delta Smelt in December 2008.

In June 2009, The National Marine Fisheries Service issued a biological opinion for Sacramento River Winter-run and Central Valley Spring-run Chinook Salmon, Central Valley Steelhead and Southern Distinct Population Segment (DPS) of Green Sturgeon. Both concluded that water projects are putting these Delta fish species at risk of extinction.

If there were no Delta Smelt protections, there would continue to be protections for the fishes covered under the other opinions, and for water quality and flow standards.

Q: Why is outflow important for Delta Smelt?

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A:Studies have demonstrated that outflow has a strong effect on the distribution of young Delta Smelt and that increasing outflow improves the quality of Delta Smelt's habitat in some parts of the Bay-Delta estuary. Delta Smelt is a fish that only lives one year and high quality habitat is needed throughout its short life cycle.

Q: Is the water that's moving through the Delta being wasted if it runs out to the ocean?

A: Water passing through the Delta and out to the ocean is not being wasted. Water flowing from our rivers through the Bay and the Delta performs many important functions for people and the environment. If flow into and out of the Delta is too low it becomes too salty for growing crops or drinking and habitat values for native fish diminish. The water also carries sediment and nutrients that are important for not only the Bay and the Delta but also to coastal communities and beaches.

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Q: Wasn't the FWS 2008 biological opinion overturned in federal court?

A: No. While there have been court challenges, in September 2014 the Ninth Circuit court issued its mandate to those challenges and consequently, the 2008 biological opinion continues to be implemented.