For decades, most cans of tuna sold in the United States have carried a symbol on the label. Featuring a silhouette of a leaping cetacean and the words “dolphin-safe,” it assures buyers that no dolphins were harmed in the production of that lunch.

While consumers have been aware of the need to protect marine mammals from fishing vessels since before the first dolphin-safe label appeared in 1990 — as it became widely known that dolphins were caught intentionally along with tuna — there is a human cost that has been mostly obscured.

A recent investigation by The Associated Press found that shrimp processors in Thailand often rely on what is essentially slave labor. The AP depicted children in tears as they peeled shrimp alongside adults and a woman who miscarried at eight months and was forced to continue working. There were also reported beatings, threats and generally horrific work conditions. The investigation tracked shrimp from these facilities into supply chains that reach almost every major grocery chain in the U.S.

Other investigations published by The New York Times and U.K. newspaper The Guardian have reported the practice of capturing workers for fishing fleets, which keep the workers captive far out at sea in international waters around Southeast Asia.

But human-rights and environmental groups say the situation may not improve anytime soon, even as consumers become more aware of the real cost of cheap protein from the ocean.

“It’s really only been a few years now that these scandals have started to emerge,” said John Hocevar, a marine biologist with Greenpeace USA who directs the group’s oceans campaign. “I think that people have been aware of environment problems with fisheries and seafood for at least a couple decades.”

That visibility is reflected in the grocery aisle. Whole Foods Market, for example, labels its seafood with sustainability ratings and country-of-origin information so consumers can make informed choices.

At the same time, the chain still sells shrimp from Thailand, often for lower prices than the U.S.-sourced shrimp on ice next to it in the display case. When asked about the issue, Whole Foods spokeswoman McKinzey Crossland said that the company “has zero tolerance for human rights abuses” and that it already investigated its supply chain and was satisfied with it.

With retailers pressured by market forces and with certification programs lacking legal backing, some activists say a stronger regulatory regime is needed.

But it’s not clear that certification is the answer. Nongovernmental labeling initiatives in other industries have had mixed results. GoodWeave International (formerly RugMark), a nongovernmental licensing program meant to ensure that carpets are made without child labor, recently joined with a major American retailer. But the Kimberly Process, aimed at preventing conflict diamonds from entering mainstream markets was repudiated four years ago by the organization that started it.

“Most of our evidence shows that [voluntary] certification doesn’t necessarily work,” said Kevin Cassidy of the International Labor Organization. “Who is verifying their statements? I think the government is the only entity that is well positioned to do that.”

Northern California’s Monterey Bay Aquarium, widely seen as an institutional authority on the environmental sustainability of seafood, hopes to have a guide on labor and human-rights issues available for concerned consumers available sometime in 2016 to complement its popular environmental one.

“We recognize the severity of the problem and the importance of finding solutions to protect people and the environment,” Jennifer Dianto Kemmerly, the director of the Monterey Bay Aquarium Seafood Watch program, said in an email. “Accordingly, we are working with human rights experts to better identify abuses and what you can do.”

If the labor-rights program it is building can become as comprehensive as Seafood Watch’s environmental one, it could help put market pressure on companies and regulators. Seafood Watch provides environmental sustainability information tailored to seafood found in all 50 states on its website, in wallet-size cards and an app. It even has a guide for sushi menus.

Still, the increase in labor rights awareness is well behind environmental awareness, even as organizations try to close the gap.

“People can’t walk into Walmart or Safeway and wonder if the seafood they’re buying is processed by slaves. That’s just not OK,” Hocevar said. “It’s not just farmed shrimp, and it’s not just Thailand … It’s a global problem.”