by Valerie Wong (’24) | November 17, 2023

This August, a leak in a Pacific Gas & Electric Company (PG&E) canal released sediment into Butte Creek, an important habitat for Chinook salmon and steelhead trout in Central California. The creek provides a vital pathway for these endangered species as they migrate to and from the Pacific Ocean. 

Chinook salmon undergo “salmon runs” every year from their breeding grounds in Northern Californian creeks to the Pacific Ocean at varying times of the year. The dangerous journey is an essential part of their life cycle, as they live and grow in saltwater oceans before returning upstream to spawn and die in freshwater creeks. However, the number of fish completing the journey has steadily declined due to environmental conditions, human impact, and other factors. Of the four main salmon run populations, spring-run Chinook salmon are most at risk, having been listed as threatened under the federal Endangered Species Act since 1999. 

This year, the Chinook population has diminished even further, with a couple hundred out of two thousand returning to the creeks to spawn. This is due in part to California’s severe droughts from 2019 to 2022, which resulted in migration mortality rates decreasing almost five times from around 15% to around 3%. Additionally, dams threaten salmon and steelhead trout because they maintain dangerously warm temperatures and restrict access to important spawning grounds upstream. 

PG&E came under fire for violating the Endangered Species Act in May of this year due to its mismanagement of dams in the Sacramento River basin. Several fishing and conservation groups have filed suit against the electric company, charging it with maltreatment of the area’s Chinook salmon and steelhead trout.

The organizations claimed that PG&E’s Potter Valley Hydroelectric Project, which consists of Scott Dam and Cape Horn Dam on the Eel River, harmed the Chinook population by blocking access to hundreds of miles of spawning grounds and important habitat. Additionally, PG&E illegally maintained the dam in a manner that hindered the migration of both juveniles and adults while promoting high stream temperatures—the opposite of what Chinook salmon need to thrive. The drought, combined with interference from the dams, has stripped the Eel River of its once-prolific salmon population. 

While PG&E plans to put the two facilities out of use within the next few years in light of expensive operating costs, the National Marine Fisheries Service says that the company needs to change their operational procedures as well in order to conserve salmon populations. 

Now, PG&E’s sediment spill in Butte Creek threatens even more of the already depleted salmon population. Surveys found that the sediment increased the creek’s level of turbidity, which is the amount of suspended sediment, or particles, in the water. This sediment could harm fish and wildlife in the creek by blocking light for algae to grow, injuring fish gills, draining important habitats, and reducing visibility and mobility for the fish. Butte Creek is crucial to the spring-run Chinook population, being one of the only three creeks that harbor them. 

Because of the sudden plummet in Chinook numbers, state and federal organizations have been forced to take unprecedented measures. Less than five percent of adult spring-run salmon have returned to the other two creeks compared to in 2022. In fact, their population has become so low that spring-run Chinook salmon may be soon reclassified as endangered instead of threatened. The California Department of Fish and Wildlife and the National Oceanic and Atmospheric Administration are taking action by collecting the fish to breed in captivity. 

Salmon are first collected from the spring-run population. Biologists target juveniles that remain in the spawning grounds for a year after spawning rather than fish that migrate to the Pacific. Then, the salmon will be raised in captivity until they are ready to spawn. Lastly, the eggs will be returned to the creeks. 

While conservationists and biologists are seeking solutions to the drastic loss of Chinook salmon, experts note that the crisis could have been avoided in the first place with better federal water management. In the future, state and federal organizations need to be more cognizant of their effects on local species if we are to preserve biodiversity as climate change continues.