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Enlarge By Kamran Jebreili, AP Sammy the whale shark swims inside the aquarium at Dubai's Atlantis hotel in this 2008 photo. Whale sharks are considered a threatened species.

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.

The huge fish also brought the luxury marine-themed hotel's centerpiece aquarium considerable publicity. A hotel gift shop continued to sell Atlantis-branded toy models of the whale shark late Thursday afternoon.

Environmentalists' concerns centered on keeping a young, potentially reproducing female shark in a confined space and out of its natural habitat. A local newspaper, Gulf News, has called the confinement "cruel, beyond belief," and launched a campaign urging freedom for the shark it nicknamed "Sammy."

Emirates Wildlife Society/World Wildlife Fund spokeswoman Lisa Perry said she was glad to hear the shark had been freed, but questioned the lack of information about its release.

"The chances of its survival are better now when it's in the wild than when it's in captivity," Perry said. "But I'm concerned of what the condition of the animal was before its release."

Whale sharks, considered harmless to humans, can live up to 100 years and grow to 46 feet (14 meters) long. They are normally found in parts of the Atlantic and Pacific oceans.

Atlantis' Dubai outpost has been targeted by environmentalists in the past. In 2007, activists protested the sale of dolphins that were shipped 30 hours by plane from the Solomon Islands in the South Pacific. The dolphins are now housed in a man-made lagoon where they swim with hotel guests.