Chinook Salmon ESUs
Oncorhynchus tshawytscha

The largest of all salmon, Chinook—or King—Salmon routinely weigh more than 40 pounds and can reach upwards of 120. Not surprisingly, Chinook prefer to spawn in bigger streams and rivers than other species, making their redds (a salmon "nest") in larger gravel and tolerating swifter flows than their smaller relatives.

Chinook Salmon are anadromous, which means they live part of their lives in saltwater, but begin and end their lives in fresh water streams. Chinook fry (a juvenile that is still developing in a stream) will spend anywhere between three months to two years in fresh water. Likewise, they will remain at sea from one to six years before making the run back to their home rivers to spawn.

The Endangered Species Act permits the federal government to protect imperiled species, subspecies, and "distinct population segments." The term "distinct population segment" is a term of art that allows the government to protect portions of an entire species before a particular threat or population decline becomes so severe that the entire species is placed in jeopardy. For Pacific salmonids, the National Marine Fisheries Service has attempted to standardize how salmon populations are considered for protection by defining Evolutionarily Significant Units (ESUs) for each species of salmon. There are two federally protected Evolutionarily Significant Units of Chinook Salmon in the GGNRA: both are transient in the Park, present only when they swim through the GGNRA's marine waters to and from the ocean and their natal spawning streams.

Sacramento River Winter-Run Chinook Salmon ESU

This Chinook Salmon ESU was once abundant in California, with spawning populations in the Upper Sacramento River and several of its tributaries. Scientists believe that there may have been up to 200,000 fish in this population alone.

However, Shasta Dam blocked access to all of the ESU's historic spawning habitat. When the dam was completed, it was not expected that this ESU would survive.

Fortunately, cold-water releases from Shasta Dam created suitable spawning conditions for the ESU for roughly 100 km downstream from the dam. The Sacramento River Winter-run Chinook Salmon are now entirely dependent on this artificially created conditions for their survival.

For many years after the dam was constructed, these artificial conditions did not seem sufficient to maintain the ESU. The population declined from 100,000 in the 1960s to perhaps several hundred individuals in the 1990s. In addition, The Sacramento River Sacramento River Winter-Run Chinook Salmon ESU Population Graph Winter-Run Chinook Salmon ESU was protected as threatened in 1990; then protected as endangered in 1994. Its endangered status was reaffirmed in 2005.

There has been some hope for this population in recent years. Since the late 1990s, the population has seen a population increase, and has hovered steadily at just under 10,000 individuals. But if the average rate of growth in the population does not change, some biologists believe that this ESU is certain to become extinct.

Central Valley Spring-Run Chinook Salmon ESU

This ESU of Chinook Salmon once numbered more than 700,000 individuals. But by the late 1980s, the population declined to a handful of runs containing only a few hundred individuals. The remaining runs are only on small tributaries to the Sacramento River.

The Spring-Run Chinook require cool freshwater while they mature over the summer. In the hot Central Valley, summer water temperatures are only suitable above 150-500 m elevations. Unfortunately, most of this habitat is now upstream of impassable dams.

Because of its location in the Central Valley, pesticides are also a major concern for this ESU. Pesticides can affect the entire ecosystem that the salmon need to survive, and even cause male salmon to become feminized, i.e., affect the male salmon's hormonal system in a way that may affect the male's fecundity.

Moreover, biologists are concerned that the Feather River Hatchery has cross-bred different salmon populations, and now these hatchery fish are considered a major threat to the genetic integrity of the Central Valley Spring-Run Chinook Salmon ESU.

In 1999, this ESU was protected as a threatened species under the Endangered Species Act. This decision was affirmed in 2005.

Conservation Action Item

Chinook Salmon need cool, clean waters to reproduce successfully. Water diversions, dams, and water pollution are all lethal to their continued existence.

There is an action item for each Chinook ESU that uses the GGNRA:

1.Sacramento River Winter Run ESU - Salmon require strong federal protections to survive. The Endangered Species Act is our nation's best safety net for salmon on the brink of extinction. Call your congressional delegation and tell them you support a strong Endangered Species Act so future generations can enjoy Chinook Salmon running in California's rivers and streams.

2. Central Valley Spring-Run ESU - Help reduce the amount of pesticides poured into salmon habitats in the Central Valley. Eat local, organic foods for every meal for one week in 2008.

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Golden Gate National Recreation Area

Chinook Salmon ESUs Oncorhynchus tshawytscha