Promises of "responsibly-sourced" and "planet-friendly" on cans of the go-to source of cheap protein are not always backed up with evidence.
The findings of the Marine Stewardship Council-commissioned study cast light on the way brands communicate to consumers rather than their actual efforts to avoid bycatch and source fish from healthy populations.
Indeed, the commercial tuna fishing industry has made inroads on environmental performance, with more than half the tuna caught and sold in supermarkets worldwide wearing the international not-for-profit's sustainability badge.
Associate Professor Dan Daugaard, lead researcher at the University of Tasmania, said the industry was at the start of a "healthy discussion" about clear and direct eco-labelling.
All businesses are under pressure to prove they are not making misleading environmental claims, as the Australian Competition and Consumer Commission cracks down on the widespread practice known as 'green-washing'.
Assoc Prof Daugaard said imprecise or opaque wording, such as "eco-friendly", was fairly common across the 14 brands he assessed against ACCC guidelines for businesses hoping to avoid accusations of green deceit.
At the other end of the spectrum was the use of scientific terms consumers struggled to understand.
Brands that scored highest relied on concrete, clear phrases such as "line-caught to reduce bycatch" on their labels.
What separated the top performers from the rest was evidence to support claims, with brands getting around lack of space on packaging with third-party certification markers.
QR codes and website links were also used to provide more detailed information about supply chains.
"If that's not existing, then that's where the ACCC is saying 'it could well just be a greenwash'," Assoc Prof Daugaard told AAP.
Coles, John West, The Stock Merchant, Little Tuna, Walker's Tuna and Safcol emerged as leaders for their credible and clear packaging communication.
Even the best examples failed to execute on one of the ACCC's more aspirational asks, calling on brands to communicate their future plans to become more sustainable as a business.
"It's a very interesting area of almost pushing the brands to new levels of norms of what is expected by consumers," Assoc Prof Daugaard said.
Marine Stewardship Council Oceania program director Anne Gabriel said the report underscored the need for clearer sustainability messaging and evidence to support claims.
"Every purchasing and sourcing decision is a chance to protect our oceans and secure a healthier future for people and planet," she said.
Canned tuna is growing in popularity, new YouGov polling suggests, with one in four Australians eating more than they were two years ago
Health, convenience and affordability were common reasons cited by consumers for eating more of the tinned fish.Â
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