The national study, by the Minderoo Foundation, has exposed a serious problem with labelling and species substitution.
Researchers who DNA tested 672 seafood products sold at Australian supermarkets, fish markets and restaurants found 11.8 per cent didn't match what was on the label.
Shark and snapper species, and imported seafood, were most likely to be incorrectly labelled.
In Tasmania, a supermarket that purported to be selling imported stingray was actually selling critically endangered spotback skate from South America.
At a restaurant in Western Australia, something generically labelled as shark was actually a piece of smooth hammerhead, a species classed as vulnerable globally.
Minderoo's Dr Chris Wilcox, who co-authored the study, said vague labelling was a serious problem alongside incorrect labelling.
Only a quarter of the products named a particular species, with most using vague or umbrella terms such as flake and snapper.
"Flake, for instance, officially refers to gummy shark but is often misused to describe any type of shark meat," Dr Wilcox said.
"Fifteen of the mislabelled flake products were actually elephant fish, which are only distantly related to sharks.
"In one instance, we found flake served as battered fish and chips was actually school shark, which is classified as critically endangered by the International Union for Conservation of Nature red list of threatened species."
Not knowing what's ending up on dinner plates is not just a consumer rights issue, but a conservation one too.
"Australians are increasingly aware of the need to protect our ocean from unsustainable fishing and want better information about the seafood on offer so they can be confident in their purchase," said co-author Emily Harrison, who works on ocean policies at Minderoo.
"We know from previous research that consumers assume the checks and balances have already been done before the point of sale."
Dr Wilcox said the results were timely, with the Australian government considering measures to prevent the importation of illegal, unreported and unregulated seafood.
"Overall, the research confirms the mislabelling rates in Australia are similar to other wealthy countries like the United States, but points to a problem that really needs to be addressed," he said.
"Consumers should be able to rely on the labels to represent what's actually in the package.
"We wouldn't accept that in other products so we shouldn't have to accept it in seafood."
The research has been published in the peer-reviewed journal Scientific Reports.
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