As many as 300,000 fall-run Chinook salmon died Wednesday at a fish hatchery near Lake Oroville due to a pump failure.
The California Department of Fish and Wildlife says a faulty wire is to blame.
As a result, water levels drastically dropped in a portion of the hatchery, greatly reducing oxygen levels for the fish.
The department says a rapid response when the problem was discovered likely saved thousands, if not millions of salmon.
These are the same fish that were evacuated during the Oroville spillway emergency back in February.
Staff is developing additional redundancy measures to prevent future pump failures.
More than two million remaining salmon at the Thermalito Facility on the Feather River will be released over the next month.
-Capital Public Radio Staff