Chicago's Brookfield Zoo Investigating Oxygen Drop in Stingray Exhibit

Fifty-four stingrays died on Friday at Chicago's Brookfield Zoo, when their tank in the Stingray Bay area experienced a sudden drop in oxygen, according to a release.

An alarm sounded and veterinary staff rushed into provide treatment for the stingrays. However, 50 cownose rays and 4 southern stingrays succumbed.
The zoo said an equipment malfunction caused the change in oxygen levels, the release said.

"We are devastated by the tragic loss of these animals," said Bill Zeigler, senior vice president of animal programs for the Chicago Zoological Society, which runs the zoo, their release stated. "Our staff did everything possible to try and save the animals, but the situation could not be reversed."

The exhibit has been closed for the summer, and staff are working to figure out what went wrong, the release said.

The stingrays were in a shallow saltwater pool in which guests could touch and feed the animals. The pool is oblong, measuring about 80-by-26 feet long and 3 feet deep, the Chicago Tribune reported.

This isn't the first time that stingrays have died in a group at the Chicago Brookfield Zoo because of an equipment malfunction. The Tribune reported that in 2008, 19 stingrays died when a heater malfunctioned, increasing temperatures by about 10 degrees in a tank.