Routine pipe maintenance at the American River Fish hatchery Tuesday resulted in the suffocation of 150,000 Eagle Trout.
State officials say an abundance of excess dirt in the water coming from Lake Natoma caused the filtration system to shut down. The 150,000 fish lost would have been planted in spring 2016.
Shane Hunt with the Bureau of Reclamation says the incident was not a mistake.
"We aren't sure why it happened. We've used that other pipeline in the past," he told FOX40 Wednesday.
State officials now have another problem on their hands, when the filtration system shutdown Tuesday, the cooling system broke.
The surviving trout are currently swimming in 70 degree water.
"Ideal water temperature for them is 55 degrees," Department of Fish and Wildlife Spokesperson Andrew Hughan said. "Seventy degrees is really pushing it."
Maintenance crews arrived Wednesday afternoon to try to fix the coolers.
Meanwhile, wildlife officials say the loss will be minimal as the hatchery supplies fish for more than 1,200 waterways across the state of California.