Chicago Brookfield Zoo is investigating the death of all 54 of its stingrays after oxygen levels in the tank suddenly dropped. Officials are blaming an equipment malfunction for the oxygen dip in the shallow Stingray Bay habitat. The zoo stated that veterinary staff rushed to the scene but were unable to raise the oxygen levels in time to save any of the stingrays. Senior vice president of animal programs for the Chicago Zoological Society, Bill Zeigler, said that the zoo was "devastated by the tragic loss of these animals" adding that "staff did everything possible to try and save the animals". The exhibit has been running every summer since 2007, but will remain closed for the remainder of the season while staff members investigate the cause of the malfunction.
An "equipment malfunction" was also to blame in 2008, when 19 stingrays died at the same zoo after water temperatures suddenly rose by about ten degrees. Not all of the zoo's stingrays died in this particular accident, and the exhibit reopened that summer with the remaining animals.
Zoo spokeswoman Sondra Katzen stated that the stingrays were each born into captivity and were kept in a 16,000 gallon, saltwater pool, with open access to allow visitors to touch and feed them. The exhibit used to be operated by Living Exhibits, a company from San Diego, but is now run by SeaWorld.
See the statement from Chicago Brookfield Zoo below.