Severe drought spells catastrophe for California salmon populations

Audio: a conversation with John McManus president of the Golden State Salmon Association

After swimming over 300 miles from the Pacific Ocean up the Sacramento River and into Battle Creek, the adult fall Chinook salmon gather at the Coleman National Fish Hatchery fish ladder entrance on September 28, 2012 - photo: USFWS Fish and Aquatic Conservation, licensed with CC BY-NC-ND 2.0.

Last Wednesday, the California State Water Resources Control Board (CSWRCB) got bad news.

In 2020, precipitation for much of northern California ranged between 50 and 70 percent of historical average, and last year marked the ninth driest summer on record. Following the driest December and January in recorded history, 2021 is shaping up to be even worse.

This year has been deemed a “Shasta Critical” year based on inflow to Shasta Lake. Contracted diversions to the Central Valley Project and the State Water Project have been reduced by 25 percent across the board, though compliance is voluntary, according to the Sacramento River Settlement Contractors.

Several who made presentations to the board last Wednesday contend that 75 percent for ag and municipal uses leaves too little cold water for salmon to successfully spawn. Biologists predict up to 90 percent salmon egg mortality this year.

Between 1920 and 1930, California lost 80 percent of its commercial fishing industry when flood control systems were first constructed on watersheds around the Central Valley.

Water deliveries to the Central Valley Project and the State Water Project pull water from northern watersheds and pipe it to giant farms and populated urban areas, the backbone of the the state’s renowned agricultural production and economy.

But as dams have been constructed over the past century on every major river around the Central Valley, as much as 95 percent of the salmonid spawning habitat has been lost, according to the National Oceanographic and Atmospheric Administration, Fisheries.

Must see: in the story map below, see a striking pair of interactive maps that compare Central Valley salmon spawning habits before and after the construction of dams. Also, take a tour of all the major dams around the Central Valley.

The Sacramento River was once a million-fish river, and now an optimistically successful year would see 100,000 spawning fish. The winter-run Chinook salmon has been protected under the Endangered Species Act since 1994, but a Trump-era rule change circumvented some of those protections. Litigation is now pending that would overturn the rule revision.

Last week, the U.S. Bureau of Reclamation released its management plan for Shasta Dam and associated power station. As of Friday April 23, 2021, Shasta Dam has fully bypassed its power generation station, which will enable better control of water temperature released into the Sacramento River, now and later in the season.

Water temperatures greater than 56F have proven to be fatal for salmon eggs (see details below). 

As calculated through the end of May, the Bureau of Reclamation estimates up to $7 million dollars in losses from the sale of electricity. 

But U.S. Bureau of Reclamation records show, over the last month, deliveries have ramped up to meet 2021 contract demands for agriculture and municipal uses, and some who spoke to the CSWRCB last Wednesday said the chance to make a difference for the salmon could be slipping away. 

“Within a few weeks, too much water will have been released from Shasta, and the damage will be done,” said John McManus, president of the Golden State Salmon Association.

To learn more about California salmon fisheries in 2021, we spoke with John McManus by phone.

See sound design credits below.

Why Temperature Matters

State Water Board Order 90-5 mandates that the U.S. Bureau of Reclamation “shall operate Keswick Dam, Shasta Dam, and the Spring Creek Power Plant to meet daily average water temperature of 56F in the Sacramento River at Red Bluff Diversion Dam during periods when higher temperatures will be detrimental to the fishery.”

Adult Chinook salmon can begin the fall upstream migration as soon as June and peak in August. The fish spawn from October through December.

Spring-run Chinook salmon begin their upstream journey in the Sacramento River in late March. According to the California Department of Fish and Wildlife, adults spend the summer in cool water habitats and then spawn from sometime in August through early October. 

Spawning takes roughly 92 days until the fry begin to emerge from eggs laid and fertilized in redds in river gravel.

Some Central Valley hatcheries have the ability to chill water in limited spawning areas, which may help bolster the 2021 salmon population, but when river water exceeds 62F, almost all the salmon eggs die. Water managers predict critically warm water temperatures when the fall Chinook salmon run would otherwise be in full swing.

Stephen Maurano is a biologist with the National Marine Fisheries Service, Central Valley office. Maurano made a presentation to the CSWRCB last Wednesday in which he described that it is difficult for aquatic organisms to get oxygen from water, particularly if you’re a fish egg. Fish have gills to harvest oxygen, but when the surrounding water begins to warm for a salmon egg, the metabolism of the embryonic fish increases, which increases the demand for oxygen, beyond its ability to pull the oxygen from the water, according to Maurano.

A committee has been formed, and a Temperature Management Plan is being written that the CSWRCB will consider and vote on by the end of April.


Music credits as reported to the Public Radio Exchange, in order of appearance:

Song: Left Over Sea Running
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 5:02

Song: Drifting Off
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 1:47

Song: Whales Charging A Boat
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 00:55

Song: Blue Whales in Range
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 00:57

Song: Right Whales
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 1:12

Song: Herd Noises
Artist: Dr. Roger Payne
Album: Deep Voices – Recordings of Humpback, Blue, and Right Whales
Label: Living Music
Date: 2007
Duration: 00:42


Brian Bahouth is editor of the Ally and a career public media reporter. Support his work in the Ally.