JOHANNESBURG — A medal-winning Paralympian from South Africa lost part of his right leg in a great white shark attack a decade ago. This week, he is an ambassador for sharks at a U.N. wildlife conference.

Achmat Hassiem on Wednesday called for tighter controls on trade in some shark species as well as in mobula rays, saying their numbers are in sharp decline. Sharks get a “bad rap” in a popular culture that portrays them as killing machines, when in fact they are increasingly vulnerable, he said.

“I personally have no grudges against the shark,” said the 34-year-old Hassiem.

Sharks “kind of keep the ocean’s balance in order,” he said. “It’s really, really tragic, the rate that they’re being wiped out.”

Tens of millions of sharks are killed annually to meet the demand for shark fin soup and other products, according to Hassiem.

The U.S.-based Pew Charitable Trusts asked Hassiem six years ago to campaign for shark conservation. He has since traveled widely as a conservationist and motivational speaker while pursuing his athletic career.

Hassiem competed at the Beijing Paralympics in 2008 and won bronze in the 100-meter butterfly at the London Paralympics in 2012. He recently returned to South Africa from the Rio games, where he finished eighth in the same race. It was his last Paralympic competition.

He is attending the Johannesburg meeting of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES.

Conservationists hope the wildlife conference will ban trade on threatened silky sharks, thresher sharks and mobula rays.

“It’s my right to give back to the shark for all the opportunities it has given me,” Hassiem said. “The way I can do that is just stand up for sharks.”

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