A resort hotel on one of Dubai’s manmade islands said Thursday it has freed a whale shark whose captivity had been criticized by environmentalists.

The Atlantis hotel on the city-state’s Palm Jumeirah island said it released the 13-foot (4-meter) female shark into the Persian Gulf, but did not provide documentation.

Whale sharks, the largest fish in the world, are considered a threatened species.

Atlantis Vice President Steve Kaiser said in a written response to questions the animal has been fitted with a satellite tracking tag to record its position for research purposes.

He said the shark was in good health when it was released Thursday morning off the east side of the palm-shaped island, one of several artificial islands off the city-state’s coast. Outsiders were not invited for the safety of the shark, he said.

“The health and well being of the animal has always been our number one priority,” Kaiser said in response to questions from The Associated Press about the release. “The seasonal elements affecting water temperature, salinity and migratory patterns were perfect for enhancing her survival in the open ocean.”

Employees outside the hotel’s massive aquarium, which contains 65,000 fish, stingrays and other sea creatures, said they had been instructed not to speak to the media about the shark.

The hotel is run by Bahamas-based Kerzner International in partnership with a division of Dubai’s struggling state-run conglomerate Dubai World.

Environmentalists began calling for the shark’s release shortly after the hotel announced it had rescued it from the shallow waters off Dubai’s coast in 2008.