Probable Chlorine Exposure Kills 21,000 Fish at UC Davis

Threatened and endangered species were among the dead, likely poisoned overnight by a chlorination system used to decontaminate the animals’ tank water.

Written byCatherine Offord
| 2 min read
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Roughly 21,000 fish have died at a University of California, Davis, research center after apparently being exposed to toxic levels of chlorine released by the tanks’ decontamination system. The fish, which were discovered dead in their tanks at the Center for Aquatic Biology and Aquaculture (CABA) last Tuesday (August 9), included Chinook salmon (Oncorhynchus tshawytscha) and green and white sturgeon (Acipenser medirostris and A. transmontanus), species that are threatened or endangered in some parts of their ranges. Their deaths, experts say, could set back research at the center by years.

“We are devastated to report that a catastrophic failure has resulted in the loss of about 21,000 fish” at CABA, UC Davis said in a statement last Thursday. “The loss appears to be due to chlorine exposure, to which fish are especially sensitive,” it added, noting that an internal investigation and external review were underway to figure out exactly what ...

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Meet the Author

  • After undergraduate research with spiders at the University of Oxford and graduate research with ants at Princeton University, Catherine left arthropods and academia to become a science journalist. She has worked in various guises at The Scientist since 2016. As Senior Editor, she wrote articles for the online and print publications, and edited the magazine’s Notebook, Careers, and Bio Business sections. She reports on subjects ranging from cellular and molecular biology to research misconduct and science policy. Find more of her work at her website.

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