Officials warn heat wave could kill nearly all young endangered salmon in Sacramento River

California officials are raising concerns that the intense heat waves across the state may cause nearly all young endangered salmon in the Sacramento River to die.

The California Department of Fish and Wildlife (CDFW) told CNN that there could be a “near-complete loss” of juvenile chinook salmon because temperatures have reached higher than 100 degrees for prolonged periods of time, which causes the river to overheat.

Those conditions, according to the department, create an environment where the fish are not able to grow beyond their egg stage.

“This persistent heat dome over the West Coast will likely result in earlier loss of ability to provide cool water and subsequently, it is possible that all in-river juveniles will not survive this season,” CDFW said in a statement to CNN.

The CDFW confirmed in a statement to The Hill that the possibility of a “near-complete loss” of young in-river Chinook salmon does exist, based on potential water and weather outlooks.

“Modeling of monthly operations predicts high levels of mortality for Chinook salmon during egg incubation in the Sacramento River due to limited cold-water pool in Lake Shasta and downstream water deliveries. Unanticipated depletions downstream have resulted in increased releases from numerous reservoirs in the Central Valley,” the CDFW said in a statement to The Hill. 

“The State Water Project and Central Valley Water Project are attempting to balance many beneficial uses, including municipal drinking water. Chinook salmon mortality during egg incubation could be higher than originally predicted. It’s an extreme set of cascading climate events pushing us into this crisis situation,” the department added.

California is one of a number of Western states that has experienced extremely high temperatures in recent weeks, according to the network.

A study out last week determined that the heat wave and drought are continued symptoms of climate change. The study suggested that such a heat wave would not be possible if human activity did not play a role in Earth’s temperatures increasing.

As temperatures continue to rise, a number of reservoirs in California’s Central Valley have rerouted water to cities and farmers, according to CNN. That move, however, has caused rivers to become more shallow and too hot for fish to develop from eggs, which can on average take at least 60 days to happen.

The salmon are losing their insulation layer because the temperature of the water is increasing, which leads to evaporation, according to CNN. The insulation blanket usually makes the bottom of the river colder.

Officials said the salmon eggs will die if they are in water that has a temperature higher than 56 degrees.

Authorities are now saying that only a few thousand winter-run chinook salmon remain, according to CNN.

“It’s an extreme set of cascading climate events pushing us into this crisis situation,” CDFW spokesman Jordan Traverso said, according to the network.

The CDFW announced on Tuesday that it successfully relocated 1.1 million juvenile, fall-run chinook salmon from its Iron Gate Fish Hatchery in Siskiyou County.

The fish were transported to a nearby satellite facility and to the Trinity River Hatchery, where they will stay until conditions in the Klamath River improve.

“Due to warm water temperatures, low water flow and an exceedingly high probability of succumbing to disease in the river, CDFW decided to retain these salmon within its hatchery system over the summer until Klamath River conditions improve,” the department wrote.

The CDFW told The Hill that it has taken the “proactive measure” of moving millions of hatchery-raised juvenile Central Valley fall-run Chinook salmon to San Pablo Bay, San Francisco Bay and seaside net pens “due to projected poor river conditions in the Central Valley.”

“The massive trucking operation is designed to ensure the highest level of survival for the young salmon on their hazardous journey to the Pacific Ocean and will transport around 20 percent more salmon around the Central Valley rivers and Delta than in typical water years,” the department added.

The CDFW also emphasized California Gov. Gavin Newsom’s (D) request last week that residents in the state cut their water use by 15 percent amid the drought, writing “Every drop counts.”

“This underscores the importance of Governor Newsom’s announcement last week calling on Californians to voluntarily reduce their water use by 15 percent with simple measures to protect water reserves and to help maintain critical flows for fish and wildlife wherever possible,” the department added.

This story was updated at 3:29 p.m.