A Dubuque, Iowa museum and aquarium has closed an exhibit as staff investigates the death of eight stingrays today.

Five cownose rays, two yellow stingrays and one Atlantic stingray are among the animals that died today at the National Mississippi River Museum & Aquarium in Dubuque. According to a press release from the Dubuque museum, an additional cownose ray remains in stable condition

The official cause of death will not be confirmed until necropsy results, water quality testing and toxicology reports are completed, which could take several weeks.

The stingray exhibit is closed as staff investigates the death of the stingrays. Stingray feedings and touch tank capabilities at the Delta in the National River Center are on hold until further notice

The release states that staff "noticed animals in distress" when they arrived this morning. Tthe release states:

"The exhibit appeared to have experienced a supersaturation event, following a malfunction in the life support system, causing gas embolisms, or gas bubble disease, in the animals," . "The exhibit’s monitoring system showed a spike in oxygen levels late Wednesday night but did not send an alarm notification to staff as expected. The cause of the malfunction and lack of alarm notification is still under investigation."

The release also included comments from Andy Allison, vice president of living collections and education:

"Our staff is heartbroken over this loss and are taking steps to ensure this does not happen in the future,”. “We are reevaluating our life support and monitoring systems for all exhibits, including new systems being constructed within the Rivers to the Sea exhibit space."

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The Delta is expected to reopen on Friday, December 23, according to the release, but touching and stingray feedings will not take place until further notice. Visitors should check the River museum's website for updates related to the Delta exhibit.

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