NEW YORK: The suppliers of leading brands of canned tuna have committed to making their products fully traceable and to avoiding illegal fishing methods, a development the UN has described as "a big achievement".

At the UN's Ocean Conference in New York this week, the Tuna 2020 Traceability Declaration was endorsed by 50 companies and a group of non-governmental organisations.

"Illegal catches that aren't registered distort the information and in turn threaten the very existence of the fish stocks and the communities that rely on them," said Arni Mathiesen, assistant director-general of the Food & Agricultural Organization's Fisheries and Aquaculture Department.

"We as administrators and regulators know that we can set all kinds of rules and standards, but the ones out in the field make the next move, so getting an initiative like this, where the stakeholders are pledging to uphold transparency and follow the rules … is a big achievement."

The list of signatories included the owners of three of the top brands in the US, the South China Morning Post reported: South Korea's Dongwon Industries (StarKist), Thailand's Thai Union (Chicken of the Sea) and California-based Bumble Bee Seafoods.

But these three, which account for around 80% of the US market, are also in the bottom quarter of the latest Greenpeace ranking of 20 canned tuna brands based on how sustainable, ethical, and fair their tuna products are for the world's oceans—and for the workers that help get the products to store shelves.

They have also been accused of price-fixing, with the US Department of Justice investigating allegations against the three since 2015.

All of which suggests there may be a whiff of "greenwash" about the brands' actions at the UN.

But with grocery chains like Whole Foods Market and Hy-Vee taking a stronger stance on this issue, campaigners hope that major manufacturers will have to step up – and labelling will become an important area.

"Dolphin-safe isn't enough anymore," said Ryan Bigelow, program engagement manager with Seafood Watch.

"Look for pole and line caught, labels that say FAD free, and some kind of certification is usually a helpful guide," he told Southern California Public Radio. "Those are the big ones."

Data sourced from South China Morning Post, Greenpeace, Fox Business, Southern California Public Radio; additional content by WARC staff