Environmental authorities there have asked Costa Rica to help track down those responsible.
The slaughter around Malpelo Island was reported by Russian scuba divers who were visiting the UNESCO Natural World Heritage Site because of its famed large gathering of sharks.
Those divers told authorities that they had seen about 10 Costa Rican fishing boats in the area where the dead sharks littered the ocean floor.
Killing sharks for their fins, the main ingredient in shark fin soup, is illegal in Colombian waters but the remote island is rarely patrolled by navy ships.
Shark fin soup is considered a delicacy in Chinese cuisine. Hong Kong restaurants charge up to $100 per bowl for it.
Photo: Justin Ebert