This weekend, fisherman herded approximately 250 bottlenose dolphins into Japan's Taiji Cove and selected about a dozen, including an extremely rare albino dolphin, for possible sale to marine parks and aquariums.

Defenders of the drive-hunt method say that the roundup is part of a cultural tradition, but demand for these animals also comes from aquariums and marine parks, which are part of a billion-dollar industry worldwide. Discovery News investigated where US marine park facilities get their dolphins and if any of them have come from Taiji Cove.

Japanese Fisherman Capture Rare, Albino Dolphin in Taiji Cove

Among the dolphins housed at marine parks and aquariums in the United States, 100 were caught in the wild and are on display at 23 facilities nationwide, according to Ceta-Base, a database of captive-held cetaceans around the world.

The Alliance of Marine Mammal Parks and Aquariums says that approximately 64 percent of the dolphins in its member facilities are not wild, but were born in a park or aquarium.

Some of those dolphins live for decades, such as Toad, who has been with the U.S. Navy for 45 years, and Nellie, who is at Augustine, FL-based Marineland Dolphin Adventure and has lived in captivity for 60 years.

But others do not survive that long. In the 2009 study The Case Against Marine Mammals in Captivity, co-published by The Humane Society of the United States and the World Society for the Protection of Animals, the authors write:

Fierce debate continues over the issue of mortality rates and longevity, especially of whales and dolphins. The mortality data related to live captures are more straightforward -- capture is undeniably stressful and, in dolphins, results in a six-fold increase in mortality risk during and immediately after capture.

Despite this, the Marine Mammal Protection Act (MMPA), enacted in 1972, makes it legal to capture dolphins from the wild for entertainment purposes, although no permits to do so have been issued since 1989. One explanation, notes the World Society for the Protection of Animals, is the unprecedented number of dolphin strandings over the last couple of decades that have made it unnecessary to take these marine mammals from the wild.

Two dolphins jump through hoops at a traveling dolphin circus in Indonesia. Over 72 bottlenose and stenella dolphins are frequently hauled out of their plastic performing pools and loaded into the back of trucks as the circuses move from town to town.Arief Priyono/LightRocket via Getty Images

Another reason that US-based facilities may not need to capture wild dolphins is that it's legal to import them from other countries, as long as those dolphins were caught according to US regulations.

“A provision in the MMPA requires that imports cannot come from inhumane capture methods or unsustainable populations,” David Phillips, executive director at Earth Island Institute and director of the International Marine Mammal Project, told Discovery News. But, he said, record keeping is not very good, making it possible for other countries to justify their methods even if they may not be meeting our standards.

Japanese Fisherman Capture Rare, Albino Dolphin in Taiji Cove

Even the phrase “unsustainable population” is loaded when applied to animals such as bottlenose dolphins. These marine mammals are not listed as threatened or endangered under the Endangered Species Act.

“But bottlenose dolphins are classified as ‘data deficient’ on the International Union for Conservation of Nature's Red List and population trends for U.S. stocks are currently unknown,” Ric O’Barry, campaign director of the Dolphin Project, told Discovery News while monitoring the weekend's dolphin roundup at Taiji Cove.

Captain Paul Watson of the Sea Shepherd Conservation Society and his team were also observing the Taiji event. Their team reports that, based on information from previous years, many of the Taiji dolphins get shipped to Mexico, Turkey, Dubai, China, Hong Kong, Taiwan, Korea and other parts of Japan.

But aquariums in the United States still attempt to import dolphins from places like Japan and Russia, where reports of inhumane treatment of animals are common. In 2012, for example, SeaWorld attempted to obtain a permit to import a Pacific white-sided dolphin from Japan that was identified to have been born in captivity.

It can't be confirmed whether or not this dolphin or others being imported from Japan come directly Taiji Cove. Lisa Agabian, a Sea Shepherd spokesperson, said to Discovery News, however, "Documents in other countries can be falsified as to the marine mammal's true source of origin. It is then difficult for anyone to prove otherwise."

The increased publicity of the drive-hunt methods such as those used at Taiji Cove is increasing awareness of the plight of dolphins taken from the wild to serve in the entertainment industry. Even the US ambassador to Japan, Caroline Kennedy, sent a tweet over the weekend about her concern at the Japanese dolphin hunt.

For now, the billion-dollar-per-year marine park industry seems to have the upper hand.