FORT LAUDERDALE, Fla. — They’ve entertained millions at marine parks and aquariums — whales, dolphins and other sea mammals spinning and splashing to the delight of audiences for decades.

But the recent death of a SeaWorld trainer by a killer whale in Orlando and the Oscar-winning documentary “The Cove,” about dolphin captures in Japan, have cast unprecedented attention on the industry that brought us Shamu and Flipper.

A congressional committee has scheduled an oversight hearing April 27 to hear testimony on marine mammals in captivity. The Sun Sentinel confirmed the hearing by the House Subcommittee on Insular Affairs, Oceans and Wildlife through federal officials who have been asked to testify.

Animal welfare advocates are hoping for tighter regulation of a multibillion-dollar business that they say has profited at the expense of sea animals.

“There’s a whole other side to the industry that I think the public is beginning to understand,” said Courtney Vail, a spokeswoman for the Whale and Dolphin Conservation Society, which opposes keeping marine mammals in captivity. “It’s not all sunshine and happiness.”

The Sun Sentinel explored the world behind marine parks in a 2004 investigative series. It found that over the previous three decades, about 1,500 sea lions, seals, dolphins and whales in marine parks had died at a young age, some from human hazards such as capture shock and ingestion of coins and foreign objects.

The industry took root in Florida when the first marine park, Marineland of Florida, opened in 1938, and began an international trade with killer whales now worth up to $5 million each.

Until the 1980s, many of the marine stars came from the wild, with Florida waters supplying bottlenose dolphins that ended up at parks in Europe, Israel and Canada. U.S. attractions stopped capturing marine mammals more than 15 years ago and now rely on breeding.

Today, of the 1,243 marine mammals in the nation’s parks, zoos and aquariums, only 15 percent were caught in the wild, a Sun Sentinel analysis of federal data shows. Another 14 percent were found stranded on beaches, and the rest were born in captivity.

Florida still leads the nation with 391 marine mammals at 14 attractions. SeaWorld in Orlando has the most, 207. Miami Seaquarium, the country’s fourth-largest facility, has the oldest living killer whale in captivity, Lolita, captured in 1970 and about 43 years old.

Marine parks say they educate and expose visitors to animals they might never see in the wild. Congress recognized that value in 1972, exempting “public display” facilities from a ban on capturing and importing marine mammals as long as they provide education or conservation programs.