ZHUHAI, China — The polar bears pace back and forth in their enclosure, heads lolling as they turn, their distress apparent. Chinese tourists crowd around display windows to snap quick close-ups on their phones.

Beluga whales nod in time to loud music, “kiss” children or spit plumes of water toward the gasping crowd. A walrus blows a trumpet, seals catch Frisbees and dolphins propel their trainers through the water on their beaks.

Chimelong Ocean Kingdom here is the largest of China’s 39 ocean theme parks, the flagship of a booming industry that is capturing some of the world’s most magnificent and intelligent animals from the wild and keeping many of them in cramped, inadequate conditions.

Attendance has been dropping at some of the roughly 30 ocean parks in the United States in the wake of reports about the welfare of sea mammals in captivity.

But here in China, the industry cannot expand rapidly enough to satisfy the nation’s apparent hunger to watch animals perform: Sixteen more parks are under construction, and Chimelong’s park in Zhuhai, close to Macao on China’s southern coast, recorded 80,000 visitors on one day alone last year.

A new report by the China Cetacean Alliance (CCA), a coalition of international animal protection groups, says the parks house a total of 491 cetaceans, including 279 bottlenose dolphins and 114 belugas, as well as seven orcas, or killer whales.

Most of those animals were caught in the waters of Russia, Japan and the Solomon Islands, by methods that are “known to cause stress and fear in free-ranging individuals,” the report said.

“Such captures also disrupt normal social groups,” it said, adding that for some species the disruption is “definitely contributing to population decline.”

In captivity, the report says, many animals are likely to be living in conditions that are “inadequate to meet the complex physical and behavioral needs of cetaceans.”

Belugas, or white whales, are listed as “near threatened” under CITES, an international treaty drawn up in 1973 to protect wildlife against over-exploitation. Virtually all the belugas in China are imported from Russia, where the population is falling, the CCA said, at a reported price of $125,000 to $240,000 each.

Intensely social animals, belugas can swim up to 100 miles a day in the wild and routinely dive 30 to 1,000 feet in arctic and subarctic waters. In captivity, they circle back and forth in shallow, featureless tanks and are taught to perform tricks that conflict with their natural behaviors.

Chinese media reported the first birth of a beluga in captivity here in 2014. The calf died within a month, the CCA said, citing park staff members who said it is believed to have died because the tank was too small to allow its mother to nurse it.

“The situation in China is far worse regarding captive marine mammal welfare than in the United States,” said Naomi Rose, a marine mammal scientist with the Animal Welfare Institute in Washington, part of the CCA. “China is at the stage the U.S. was 50 years ago.”

The parks, the CCA report says, depict the animals as entertainers, impart little or no information to the public during shows and are unlikely to leave visitors motivated to preserve habitats.