New Pacific Institute Report Finds California Drought Worsening Long-Term Decline of Fish Populations

Report Makes Policy and Management Recommendations to Prioritize Freshwater Ecosystems Before and During Future Droughts

Oakland, California, Sept. 07, 2022 (GLOBE NEWSWIRE) -- FOR IMMEDIATE RELEASE  

Oakland, California — September 7, 2022 — The Pacific Institute, a global nonpartisan water think tank working to catalyze the transformation to water resilience, today released a new report highlighting how California’s current drought has threatened fish and their freshwater ecosystems. The report, “Left Out in Drought: California Fish,” finds warmer water temperatures, increasing algal blooms, and lower stream flows associated with the 2020-present drought have exacerbated the long-term decline of California’s fish populations and threatened the continued survival of some native fish species, many of which face extinction. Fish population health is recognized as a major indicator of freshwater ecosystem health more broadly.  

More than 97% of California is now experiencing severe drought. While California is known for extreme hydrologic variability, climate change has increased the severity and frequency of droughts.  

“The current drought has significantly intensified the crisis many fish species face in California, resulting in deadly conditions for some during the past two years and impacts on the state’s communities, economies, and ecosystems,” said Morgan Shimabuku, Senior Researcher at the Pacific Institute and lead author of the report. “When informed by science, the policy and management decisions we make today can help ensure better outcomes in the future for California’s fish, aquatic ecosystems, and those who rely on and benefit from them.” 

The report synthesizes and summarizes US Geological Survey (USGS) flow data, state and federal fish counts, reports from state and federal agencies, and peer-reviewed literature. While the report focuses on data from the Sacramento River, San Joaquin River, and San Francisco Bay-Delta, the findings illuminate broader trends for drought-related impacts to fish and freshwater ecosystems across California and beyond. The report finds: 

  • Water temperatures in the Sacramento and San Joaquin rivers exceeded the lethal limit for salmon during multiple months in 2020 and 2021, decreasing fish survival rates. For example, the egg-to-fry survival rate for endangered Sacramento River winter-run Chinook salmon reached a historic low of 2.6% in 2021, largely due to high water temperatures. During the same year, in addition to experiencing historically high water temperatures, river flows reached an 11-year low of 6.4 million acre-feet. 
  • San Francisco Bay-Delta ecosystem conditions have worsened as the drought has progressed. Due to stagnant water, high water temperatures, and high nutrient levels, harmful algal blooms in the Bay-Delta were nearly twice as extensive in 2021 as they were in 2020, reducing oxygen levels and threatening fish. 
  • During droughts, smaller side streams and lakes are particularly vulnerable to loss of runoff from low rain and snowmelt. In some places, native fish species have adapted to these specific aquatic habitats, increasing their risk of extinction if these waterways don't have enough flow. For example, the Lost River sucker and shortnose sucker, both federally listed endangered species, have native habitat in Tule Lake, a National Wildlife Refuge in northern California. In 2022, these fish had to be hand caught and transported to nearby holding ponds to survive, as the lake completely dried up over the summer. 

The report also highlights that human-caused degradation and alterations to California’s rivers and streams, including approximately 1,500 dams, thousands of miles of levees, and millions of acre-feet of water transfers out of the environment to satisfy human water demands, have reduced freshwater fish species’ ability to withstand drought impacts. It additionally recognizes that fish species have been negatively impacted as freshwater ecosystems have been de-prioritized in policy decisions during droughts.   

The report includes six recommendations for California decisionmakers to build drought resilience for freshwater ecosystems. To improve ecosystem management during drought, the report recommends: 

  • making water management institutions nimbler during drought to improve cooperation and coordination between federal, state, tribal, and other actors;  
  • creating drought plans for freshwater ecosystems that are proactive rather than depending on emergency declarations that often come after damage has already occurred; and  
  • maintaining minimum instream flow requirements during emergency drought declarations. 

To improve ongoing ecosystem management, the report also recommends: 

  • prioritizing broader freshwater ecosystem protection, including not only providing volumetric requirements for instream flows but also water quality considerations such as temperature and dissolved oxygen concentrations, considerations for the timing of instream flows, restoring natural flow and connectivity, and creating freshwater protected areas;  
  • expediting projects to restore floodplain connectivity and health; and 
  • standardizing and coordinating research and data collection, while improving information on lesser-known species. 

To highlight an example of a freshwater ecosystem management success, the report provides a case study from Putah Creek, a tributary of the Sacramento River, where appropriately timed instream flows, cooperation and partnerships among multiple stakeholders, the removal of fish passage barriers, and on-going monitoring have led to some restoration success and longer-term fish population recovery despite periods of recurring and intensifying drought. 

Read the full report here

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Founded in 1987, the Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts in developing sustainable water policies. Its mission is to create and advance solutions to the world’s most pressing water challenges. From working with Fortune 500 companies to disenfranchised communities, the Pacific Institute leads local, national, and international efforts in developing sustainable water policies and delivering meaningful results. To learn more about the Pacific Institute, visit 


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