Two sushi chefs who worked at a Santa Monica, Calif., restaurant pleaded guilty Monday to buying and serving illegally imported whale parts in a stomach-turning case that began four years ago, when staff from the Oceanic Preservation Society and their boss, The Cove director Louie Psihoyos, launched a series of sting operations against the now-defunct establishment.

In a plea deal with federal officials, Kiyoshiro Yamamoto and Susumu Ueda each agreed to three misdemeanor charges in exchange for providing evidence against the owners of the restaurant, the Hump, which went out of business in 2010.

The chefs pleaded guilty to conspiracy and to selling illegally imported meat from sei whales caught off the coast of Japan, a violation of the federal Marine Mammal Protection Act. Sei whales are protected by the U.S. Endangered Species Act.

Each defendant could receive up to three years in federal prison, and prosecutors are recommending a $5,000 fine in addition to 200 hours of community service.

Court documents show that between 2007 and 2010, the two men procured about 11 pounds of the contraband product from a local seafood dealer, Ginichi Ohira. Ohira bought the sei—nearly $15,400 worth of “red meat,” “tail meat,” and “whale bacon”—from a Japanese supplier and imported it with an invoice marked “fatty tuna.” Ohira has pleaded guilty to selling whale meat to Los Angeles–area sushi restaurants and awaits sentencing.

The Hump sold the illegal meat off-menu, and the entire enterprise may never have come to light if not for the intrepid snooping of Psihoyos and members of his staff, who produce films and photography about the oceans and the need to protect them.

“The first time we went in [in the fall of 2009] we ordered omakase or ‘chef's choice,’ ” a collection of dishes that included “blowfish without a license, horse meat, and whale,” Psihoyos wrote in an email. Later the team discovered it needed to have federal officials “witness the buy,” he wrote, for arrests to be made. “It was too expensive for us to come back from out of town and do it again for the feds.”

But in early February 2010, The Cove was nominated for the best documentary feature Academy Award, which it won.

“The whole team was in town [in late February 2010] and we organized the sting literally right before the awards. While everyone else was going to the celebrity parties our team was busting the Hump,” Psihoyos wrote. This time, federal officials were standing by.

Because Psihoyos and the group’s director of operations, Charles Hambleton, had become too recognizable since their first visit to the restaurant, they enlisted the help of two activists to place the bust-worthy orders, Psihoyos recalled.

The whale meat was bad enough, but they were “also killing live turtles at the table and draining blood into wine glasses for customers,” he wrote. “The evil that went on in that kitchen was beyond comprehension. They even had a sign on the door warning that if you didn't want to see animals suffer—don't sit at the sushi bar.”

After a third sting operation by the group, in March 2010, law enforcement officials busted the Hump. In their plea deal, the two chefs named Brian Vidor, owner of the Hump’s parent company, Typhoon Restaurant Inc., and manager Chris Schaefer as coconspirators in the sei-meat scheme.

Vidor, according to Psihoyos, thinks he can buy his way out of his crimes. “After he got caught he gave a few bucks to an animal shelter and his lawyer thought that was price enough,” Psihoyos wrote. “He's still in business. I’d like to see him do time and have to pay a fine so steep he has to close.”

Those involved “were all selling endangered animals and torturing live beings for entertainment,” Psihoyos continued. “If there is a God, I hope all of them sustain the wrath reserved for such inhumane behavior. What I would like to see done to all of them would not be suitable for print.”