Fifty-four rays are dead after a fatal malfunction at Chicago's Brookfield Zoo on Thursday.
The zoo, which also features captive dolphins, polar bears and gorillas, announced the accident their Facebook page on Sunday.
"On July 10, there was a drop in the oxygen level at Brookfield Zoo's Stingray Bay habitat ... Despite tireless efforts by staff, all the animals, which included four southern stingrays and 50 cownose rays, succumbed."
"'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 operates the zoo. 'Our staff did everything possible to try and save the animals, but the situation could not be reversed.'"
This isn't the only case of an accident killing off captive marine animals - back in April, a Texas Aquarium lost almost 400 fish after a treatment meant to help kill a parasite in their tank.
The Brookfield Zoo announced that their Ray exhibit would remain closed for the rest of the summer season. This situation is tragic both for the animals who lost their lives and the caretakers who will no doubt mourn them. It can also serve as yet another reminder of the dangers involved when captive animals are forced to rely on machines and humans instead of their own instincts in the wild.