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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 mobula rays, saying their numbers are in sharp decline.

The U.S.-based Pew Charitable Trusts asked Hassiem six years ago to campaign for shark conservation.

Hassiem won bronze in the 100-meter butterfly at the London Paralympics. He recently returned to South Africa from the Rio Olympics, where he finished eighth in the same race.

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