Farmers vs. Fish: The Story of Delta Smelt

Featured Image: Illustration by Rene Reyes, US Bureau of Reclamation.

Reference: Moyle, P. B., Hobbs, J. A. and Durand, J. R. (2018), Delta Smelt and Water Politics in California. Fisheries, 43: 42-50. doi:10.1002/fsh.10014

Delta Smelt vs. California Agriculture

Delta smelt and the California agriculture industry have one thing in common: the need for freshwater. In California, agriculture accounts for about 62% of net water use, while urban and industrial use is approximately 16%. The remaining 22% of water are designated for environmental uses, such as maintaining streamflows and wetlands, and to protect wildlife. To move water around, over 1,400 dams and miles of aqueducts have been constructed. A tidal wetland-turned-agricultural land, the Sacramento – San Joaquin Delta is the center of California’s water distribution system. About half of California’s developed water moves through the delta via two pumping plants: Central Valley Project (CVP) and the State Water Project.

Map of the Sacramento-San Joaquin Delta. Source: USGS.

Also within the Sacramento- San Joaquin Delta reside the native delta smelt. Delta smelt are small free-swimming fish that are exceptionally vulnerable to environmental change. These fish are unable to swim against the currents of the pumping plants, easily subjected to the competition of invasive species, and commonly preyed upon by larger fish. In 1993, the delta smelt population was listed as threatened by state and federal governments and by the early 2000s their population was in severe decline. A research team led by Peter Moyle from the University of California, Davis explored the controversy between the protection of delta smelt and the livelihood of California farmers, and further analyzed the outcomes for current water use within the Sacramento-San Joaquin Delta.

The Controversy

When delta smelt were listed as a threatened species, the biggest cause of their population decline was identified as reduced freshwater flow into the estuary. This makes the water saltier, which leads to dehydration. This is similar to the reason humans shouldn’t drink saltwater when they’re thirsty. Because of this, a recovery plan was made that mandated increased freshwater flow for the smelt, which meant less water for agriculture. This incited a debate on whether freshwater flow was actually the cause for the decline – because delta smelt are a relatively fragile species, there were likely other effects that were also contributing to the population decline. Therefore, the recovery plan was generally ignored. In 1994, state and federal agencies who were co-managing the delta entered into an agreement called the Delta-Bay Accord. This agreement led to many scientific studies that explored alternative hypotheses of why the delta smelt population was in decline. Unfortunately, no clear fix for the delta smelt population was found. This prompted the California Natural Resources Agency to develop the Delta Smelt Resiliency Strategy (2016) – a series of actions that can help recover the smelt population. This Strategy proposed actions for controlling aquatic weeds, increasing water turbidity, creating spawning habitat, and lastly, increasing the outflow into the delta by 250,000 acre-feet. One acre-foot equals about one 8-lane, 25-meter swimming pool. Imagine 250,000 swimming pools full of water entering the delta per year.

Photo of a delta smelt. Source: Wikimedia Commons
The Real Story

Though many believe that the increase of freshwater flow through the delta is a waste of water to protect smelt, the main reason for the freshwater outflow is to decrease salinity in the delta in general, not just for delta smelt. In fact, maintaining proper salinity is helpful to the farmers as well, as it prevents saltwater from being pumped into agricultural land. High salinity values are common when freshwater is exported through pumps to agricultural land. From 2011 to 2016, freshwater outflow used to protect Endangered Species Act-listed species only accounted for 6.5% of the freshwater outflow.

However, delta smelt continue to take the blame for the water controversy in California, often scapegoated when farmers face challenges involving water. Delta smelt are often portrayed in the media as the useless fish responsible for farmers losing crops and jobs.

What’s next for smelt?

Unfortunately, due to the likely irreversible large-scale changes that have occurred in the Sacramento-San Joaquin Delta ecosystem, it is likely that delta smelt are headed for extinction within the next few years. It’s possible that other native species, such as winter-run Chinook salmon and longfin smelt, will be the next ones to face challenges. Large-scale changes in water and land management must occur in order to prevent extinction, but it is unlikely that this will happen quickly enough. Because only a small portion of freshwater outflow is used for delta smelt protection, the extinction of this fish along with a reversal in water outflow rulings will not actually solve the water crisis for the farmers in the delta. Saltwater intrusion will continue, and freshwater outflow will be needed at great volumes to mediate it.



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Lauren Bonatakis

I'm a second year Master's student at LSU studying the commercial freshwater fisheries in Louisiana. I am interested in pursing a career focused on the intersection of fisheries science, policy, and management. Outside of science I enjoy going to as many concerts as I can, hanging with my dog, and traveling.

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