Delta Smelt

Smelt Plan Calls for More Water Release

Dan Environment, Industry News Release

Strategies Aimed at Improving Survival of Endangered Fish, But Call for New Summer Water Release

Delta Smelt

Image provided by UC Davis Center for Watershed Sciences

The California Department of Natural Resources has released a new multi-part strategy for the sole purpose of saving the Delta smelt. It says under this comprehensive strategy, state and federal agencies will work to rapidly improve conditions for Delta smelt.

Parts of the strategy include additional water releases during summer months, in an effort to decrease salinity in areas where the smelt spend summer months. These releases would flow out to the ocean rather than to California farms, many of which are also in dire need of water.


From the Delta Smelt Plan:

Outflow Augmentation

Linkage to Conceptual Models: The CMs suggest that seasonally augmented outflows could affect two Environmental Drivers: Turbidity and Hydrology. Habitat Attributes that could be affected include Predation Risk, Harmful Algal Blooms, and Food Availability and Quality. This management action would also test the recent hypothesis that the location of the Low Salinity Zone (LSZ) is important at times of year besides fall. The extent to which these Environmental Drivers and Habitat Attributes can be positively affected through outflow augmentation will be the subject of a targeted research action.

Summary of Action: This adaptive management effort will occur in the spring and summer of 2017 and 2018. In 2016, Reclamation will provide 85 thousand acre-feet (TAF) to 200TAF additional outflow above what is required under D-1641 for release in the summer. In the spring and summer of 2017 and 2018, DWR and/or Reclamation will provide up to an additional 250TAF of outflow above D-1641 requirements. A variety of methods may be used to augment outflow, including transfers from willing sellers, changes in export or other CVP/SWP Delta operations, and/or storage releases. These flows must be consistent with the 2009 salmon biological opinion as determined by NMFS and CDFW.

To read the full plan, click here.


Cont. from the Department of Natural Resources:

The strategy represents a management shift for state and federal water and wildlife agencies, which are addressing multiple stressors on Delta smelt in a systematic way while studying the synergy of the actions.

One action already underway is the release of water drained from Sacramento Valley farm fields into the Yolo Bypass to boost production of the zooplankton that smelt eat.  Also planned is the treatment of invasive aquatic weeds in important smelt habitat in the Sacramento-San Joaquin Delta.

Other actions include:

  • Generating more brackish water habitat by providing additional outflows at certain times of the year;
  • The potential reoperation of salinity control gates in Suisun Marsh in order to attract smelt into high-quality habitat;
  • Assessing the feasibility of adding sediment to certain zones in the Delta to create the turbidity smelt use to hide from predators;
  • And studying whether to add sand – used by smelt for spawning — in areas of the Suisun Marsh and Cache Slough.

The Delta Smelt Resiliency Strategy is available here.

“This drought has pushed a struggling species too close to extinction,” said California Department of Fish and Wildlife Director Charlton H. Bonham.  “With the best available science as our guide, we’re moving fast to improve conditions so that more young Delta smelt survive this year and reproduce.”

Recent Delta smelt surveys by Fish and Wildlife have found the lowest-ever abundance levels in decades of measurements.  The small, slender fish live a single year and are found only in the Delta, where rivers draining nearly half of California empty into San Francisco Bay.  Once plentiful, Delta smelt inhabit the brackish zone in the western Delta where fresh and saltwater mix, and move upstream into fresher water to spawn.  Factors implicated in the decline of the species include non-native predators and competitors, water project pumping, altered flow patterns, aquatic weeds that reduce water turbidity, pollution, and diminished habitat.

The Delta Smelt Resiliency Strategy released today aims to generate a positive population growth trend for the species by reducing mortality and boosting the rate at which the fish grow, reproduce, and survive.  It focuses on creating better habitat, more food, higher turbidity, and reduced levels of weeds, predators, and harmful algal blooms.

Not all the measures in the strategy may prove successful, but government scientists intend to learn as much as possible from the effort.

“This strategy is about more than taking swift action to reverse the decline of the Delta smelt population,” said Mark Cowin, Director of the California Department of Water Resources.  “We intend to learn a great deal about the ecological needs of the species and the effects of our inter-related actions. Better understanding will help bring about better conditions for Delta smelt and, in turn, better management of our water resources.”

The strategy will be implemented by Fish and Wildlife, the California Department of Water Resources, the Division of Boating and Waterways, the U.S. Fish and Wildlife Service, and the U.S. Bureau of Reclamation.  The smelt food production action also involves partnering with local agricultural water agencies and farmers.

The overall strategy relies on science and conceptual models developed by the Interagency Ecological Program’s Management, Analysis, and Synthesis Team (MAST).  The conceptual models have a tiered structure with Delta smelt performance determined by habitat attributes, environmental drivers, and landscape attributes.  There are individual models for each smelt life stage.

Some ecological drivers are not well-understood or monitored and therefore have substantial uncertainty associated with actions intended to address them. However, the strategy is meant to address as many drivers as possible, with acknowledgement that some actions may not yield expected results.

In addition to the measures in the strategy, a number of habitat restoration projects that are highly likely to benefit Delta smelt are planned or underway.  Details on the projects can be found at

To learn more about Fish and Wildlife’s efforts to protect and preserve the state’s fish and wildlife through drought, please visit