More than 150,000 Eagle Lake trout died at American River Hatchery during September after routine maintenance on a pipe caused a surge of dirty water to flood the facility. The surge of sludge caused a chiller to fail and, according to the California Department of Fish and Wildlife (CDFW), the fish died owing to rising temperatures in the hatchery water.
“We already had less inventory than we wanted for this hatchery,” CDFW hatchery systems manager Bill Cox told The Sacramento Bee. “Now, if we lose those fish, that’s a big hit.”
Officials speculated that the incident may have been exacerbated by a nearby dredging operation.
The US Bureau of Reclamation, which owns the hatchery, was conducting maintenance on a pipe connected to the Nimbus Dam when some sort of failure occurred and allowed sludge from the pipe to flow into the hatchery. The thick substance clogged the hatchery’s cooling and filtration system, which caused the fish to overheat and suffocate in their holding ponds.
The incident killed off more than 78% of the hatchery’s Eagle Lake trout and did minor damage to populations of Shasta and Lahontan cutthroat trout. Officials said that due to the fish kill, the hatchery will likely be unable to stock streams and lakes in the Sacramento region at an ideal level.
“Additional losses are expected because of stress to the fish and continuing elevated water temperatures,” stated a press release from the CDFW.
Last year, rainbow trout and steelhead were evacuated from two hatcheries on the American River amid concern California's drought will cause the water to become too warm to sustain the fish. The chillers were brought in to prevent this from happening. Unfortunately when inundated with dirty sludge, these systems failed.
- Erich Lueuning