21,000 Fish Die in ‘Catastrophic Failure’ at California Research Center

About 21,000 fish at an aquatic research center at the University of California, Davis, died from chlorine exposure in what the university described as a “catastrophic failure” that had shocked researchers and would significantly delay their studies.

The university said in a statement that it would investigate “where our process failed” and initiate an independent external review.

“We share the grief of the faculty, staff and students who worked to care for, study and conserve these animals,” U.C. Davis said.

The fish were found dead on Tuesday in several tanks at the Center for Aquatic Biology and Aquaculture, which sits on five acres and is home to research programs that focus on sustaining California’s aquatic species and supporting sustainable aquaculture production, according to the center’s website.

Laurie Brignolo, executive director of the Research and Teaching Animal Care Program at U.C. Davis, said on Sunday that university officials believed that the source of the chlorine was a chlorination system used to decontaminate water with fish pathogens.

If that was indeed the source, university officials were not sure how the chlorine ended up in the fish tanks. One possible explanation would be that there was a backup in the waterline system that caused the chlorine to move in the wrong direction, Ms. Brignolo said.

U.C. Davis said it was committed “to understanding what happened and making changes to the facility” to prevent such a failure from happening again.

The university said that while many of its other facilities for aquatic research “do not have similar potential for chlorine exposure, there are some that do,” and that it would evaluate the risk.

The center, which was built in the 1950s, had never before had such “an all-encompassing loss” of fish, Ms. Brignolo said. Workers complete “daily quality assurance on the pump and the water going through,” she added. On the night before the loss, she said, the roughly 21,000 fish had been checked on.

Overnight, however, enough chlorine had entered the tanks for there to be a similar amount to that in tap water — a dangerously high amount for fish, Ms. Brignolo said. Fish are not supposed to be kept in water containing even small quantities of the chemical.

The chlorine damaged the sensitive gills and skin of the center’s various fish species, which included green and white sturgeon and Chinook salmon, which is endangered.

Within 12 hours, almost all of the fish were dead.

Ms. Brignolo said she received an email on Tuesday morning from the center’s manager, who was one of the first people there that day. The manager saw that thousands of fish were dead, Ms. Brignolo said, and called it a “tragic loss.”

Workers at the center went tank by tank and tallied the losses. Only about 100 fish had survived.

“It’s absolutely devastating,” she said.

Some of the researchers and graduate students had been using the fish to study the effects of disease and environmental changes on certain species.

The huge loss of fish at the center won’t completely shut down researchers’ studies, but it will significantly set them back, some for years, Ms. Brignolo said.

The loss has also taken an emotional toll on those who work there. The university has set up a grief management program for the students and staff members who were affected.

“Their role is to provide a safe environment for several fish that are being used for research purposes,” Ms. Brignolo said. “And it’s an absolute sense of failure.”