Fishermen have been known to tell the odd tall tale of the one that got away, but it's much harder for consumers to get to the truth of exactly what fish might be on their dinner plate.
A university academic is sounding the alarm on the biodiversity and health risks associated with the sale of 'fish substitutions'.
Professor Shokoofeh Shamsi from the Graham Centre at Charles Sturt University said research showed up to 75 per cent of some fish sales in Australia are substitutions.
"When we talk about fish substitution, we're talking about when one fish, crustacean or shellfish species is being sold as another species," Professor Shamsi said.
"It's unfortunately very common around the world. It's not unique to Australia."
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Professor Shamsi says research also shows that up to 31 per cent of sales of what is being sold as Australian barramundi are actually examples of other species, many of which have been imported and some are from a completely different genus.
"There are consequences for animal welfare. Let's say you're concerned about a particular species being endangered so you don't want to buy that species," she said.
While the prevalence of commercial fish substitutions is something that has been researched before, Professor Shamsi and her team are beginning the first Australian-based study into how these sales impact the health of consumers.
"Say you go to a restaurant and you order Australian barramundi from the menu, but what you're actually eating could be Nile perch from Vietnam," she said.
"You end up getting sick and you go to the doctor and say 'all I ate was Australian barramundi'.
"What we know about barramundi is very different from what we know about what you've eaten and the pathogens that might be in it."
Besides misleading consumers, Professor Shamsi has also pointed to the potential biosecurity ramifications of these impostor fish sales. Potentially harmful parasites can often be found inside the imported fish species.
"In the long term, we need a review of biosecurity protocols when it comes to importing seafood," Professor Shamsi said.
"We also need to raise awareness that this [substitution] is common, and it can cause diseases in humans."
But, Professor Shamsi says, it is also paramount to allay the fears of consumers in the short term.
"It's important to always ask where it comes from when you're buying it, and make a decision on that. If the label does not say enough, do some further research," she said.
Proper preparation of fish when cooking and freezing can also safeguard against harmful effects.