Days before the Whale Festival in Ulsan, South Korea, last month, authorities raided a cold storage unit and found more than 27 tons—about 40 whales’ worth—of whale meat worth $3.4 million.

The meat belonged to minke whales, which can grow to 35 feet long and swim as fast as 20 miles an hour.

While Japan, Norway, and Iceland get most of the heat for whaling, conservationists say South Korea engages in controversial whaling practices too. South Korean fishermen are known to take advantage of a loophole that allows them to legally sell whale meat from animals that are accidentally caught in fishing nets.

South Korea reports an average of 80 to 100 whales as bycatch annually to the International Whaling Commission, the body that regulates whaling and whale conservation.

A number that high has led conservationists and scientists to conclude that something’s fishy.

“That bycatch is about 10 times higher than that of other countries,” with the exception of Japan, says Astrid Fuchs at the Massachusetts-based nonprofit group Whale and Dolphin Conservation. According to Fuchs, those reported numbers are likely an understatement and that experts and NGOs in country estimate bycatch numbers are at least double what’s reported.

Whale hunting is banned both by South Korean law and by the International Whaling Commission, which put a moratorium on commercial whaling in 1986, but whale meat remains popular in several coastal cities. Ulsan, home to the Whale Festival, has been involved in whaling since the Korean Empire and Russia joined forces in the late 19th century to establish whaling bases. In this city of little more than a million people, more than a hundred restaurants served whale, the Korea Times reported in 2011.

“Ulsan is the place to be if you are craving a plate of whale meat,” the article says.

Douglas MacMillan of the University of Kent and Jeonghee Han, now with the Tiger and Leopard Conservation Fund in Korea, published a study in 2011 examining bycatch trends in South Korea. “The high level of cetacean bycatch in Korean waters has allowed a thriving business and culture based on the consumption of whale meat to develop,” they wrote.

If a whale is caught as bycatch, fishermen must report the incident to the Coast Guard. The body is then inspected to make sure there aren’t any harpoon marks and a permit is issued allowing the whale to be auctioned.

“Under the current system of monitoring and control, it’s easy to launder illegally hunted minke meat from bycatch,” MacMillan told National Geographic.

One minke whale can earn a fisherman up to $85,000, according to the Hankyoreh, a progressive, English-language newspaper in South Korea. Restaurants can mark it up and sell it for a bigger profit.

“During our interviews with local fishermen and whale restaurant owners, it became clear that some fishermen were supplying fresh minke meat to restaurants at premium prices—but bycatch is rarely fresh,” MacMillan said. The researchers pushed for answers. It turned out that fishermen weren’t declaring their whales to the Coast Guard at all: “They told us that some fishermen who were struggling to make a living had converted their boats to fire harpoons and hunted minke at night.”

Aside from the bycatch loophole, under-the-radar illegal hunting is a problem in South Korea too. MacMillan and Han’s economic analysis found that the price of whale meat was falling even though demand was rising and official bycatch numbers weren’t changing.

“This suggests strongly that additional supply was coming from an illegal source,” MacMillan said.

In 2012, South Korea proposed to begin a “scientific” whaling program, but after pressure from the international community, it backed down. Japan already takes advantage of this loophole, claiming that its whaling program is for scientific purposes, but critics, conservationists, and even the International Court of Justice challenge the scientific legitimacy of Japan’s whaling program.

Check out the slide show above to learn more about how dolphins and whales are killed, legally and illegally, around the world.

July 11, 2016: This story has been corrected to reflect Jeonghee Han's current work.