15 sharks die at Indianapolis Zoo - 13 WTHR Indianapolis

15 sharks die at Indianapolis Zoo

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Bonnethead shark (photo courtesy Indyzoo.org) Bonnethead shark (photo courtesy Indyzoo.org)
More bonnethead sharks (Indianapolis Zoo photo) More bonnethead sharks (Indianapolis Zoo photo)

Emily Longnecker/Eyewitness News

Indianapolis - Fifteen sharks are dead after a mistake at the Indianapolis Zoo.

Officials say their 15 bonnethead sharks died Monday night. They were held in the first tank visitors saw when they entered the Ocean's Building. Now that tank is nearly empty.

Zoo officials say employees first noticed a problem around 7 p.m. Monday.

"They saw fish that were giving clear indications that they were in distress and they immediately called aquarists and vets," said Paul Grayson, the zoo's deputy director and senior VP of Conservation and Science. "But by the time everyone was here, it was too far along for the fish. There was very little that could be done at that point."

The sharks were then examined to figure out what killed them.

"We discovered that their gills had some damage that were very consistent with what we would believe would be caused by high levels of ozone," said Grayson.

Grayson said with damaged gills, the sharks basically suffocated.

According to Grayson, the problem started with a shut down of the tank's skimmer system for repairs.  With that system down, a probe that monitored the water's ozone levels was shut off too.

"Early afternoon, some staff believed that they could turn the ozone generator back on," said Grayson.

But with the ozone sensor still off-line, that wasn't the case and too much ozone got into the water.

"That's ultimately what caused a very slow, but deadly, build-up for the bonnethead sharks that were in that exhibit," explained Grayson.

Two emperor snappers that were also in the same tank were luckier. They survived the high ozone levels.

"The vets say their prognosis is good," said Grayson.

And so, too, is the prognosis for the future of the exhibit and the lessons employees learned from the death of these sharks.

"We'll make sure that this kind of error is never repeated again," Grayson promised.

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