Catching fishy imports to tackle seafood fraud

Next time you plate up your favourite seafood, there’s a fair chance it could have been illegally fished. At risk of quashing your appetite, estimates suggest one in five fish caught every year is fished illegally or from unreported or unregulated sources.

There’s also no real guarantee that the seafood you’re buying is what the label says it is. Sure, some supermarket seafood might be certified sustainable. But a 2020 analysis of 44 studies in 30 countries exposed rampant seafood fraud on a global scale: more than one in three seafood samples from restaurants, shops and fishmongers were mislabelled as another species.

If those numbers are hard to swallow, determining the true extent of illicit and fraudulent seafood entering Australian markets is harder still.

“It’s an incredibly hard thing to quantify because by its very nature, illegal, unreported and unregulated fishing is essentially hidden from view,” says Kendra Thomas Travaille, a marine scientist at the Minderoo Foundation who has been considering how tightening Australia’s import policies could help combat illegal seafood.

Around two-thirds of the seafood Australians eat is imported, mostly from three countries – Thailand, China and Vietnam – where poor regulations allow illegal fishers to run rife. Some slippery operators also have links to forced labour and human rights violations on fishing vessels.

Australia, however, collects hardly any data on imported seafood, not nearly enough to work out what species it is, where it was caught, if it was legal, where it was processed and who produced it, says Travaille.

“The concern comes with the fact that we can’t trace a lot of the products coming in,” she explains. “Because of that, it means that operators that are fishing illegally can sell their product in Australia, which means as an industry, it remains viable and profitable for them [to do so].”

Seafood supply chains are also extremely convoluted and murky. Small fishing boats often offload their catch to big cargo ships at sea, which enables ‘fish laundering’ of millions of tonnes of fish each year, and seafood products pass through multiple ports to be processed, packaged and shipped around the world – all of which makes it easy for fishy products to slip through the net and practically impossible to trace seafood from catch to plate.

But scientists like Zoe Doubleday, a marine ecologist at the University of South Australia, are on the case, developing technologies that could be used to pinpoint the origins of the seafood we eat and to detect instances of seafood fraud, which takes many forms.

“People might deliberately mislabel where seafood comes from, but also what species it is or how it was fished – for profit,” explains Doubleday.

Not only is this misleading to customers with good intentions of buying sustainable seafood, but swapping one species for another can pose serious health risks if they contain contaminants, pathogens or allergens.

Lax regulation of imported products also poses biosecurity risks to Australian fisheries, while mislabelling illegal catch sabotages fisheries management practices that aim to sustain or restore the health of vulnerable fish stocks. It also devalues stock from local producers. 

“When you get fraudulent seafood saying this has been sustainably fished, and it’s not – it could be illegally fished – it undermines sustainable fishing practices, the health of our oceans and our ability to prevent overfishing,” Doubleday says.

Catch-all trade names can also obscure seafood sales. One recent investigation of fish labelled as “snapper” and sold at supermarkets, by fishmongers and in restaurants in six countries including Australia found that 40% of fish tested had been mislabelled. On closer inspection, those fish represented no less than 50 different species.

This kind of seafood fraud, which may be unintentional, is easily exposed with DNA barcoding, a technique that authorities use to authenticate species identity. It involves comparing the DNA profile of a seafood sample against a library of known species, similar to the way barcodes identify shop products, says Travaille.

And it’s these DNA barcoding techniques that Travaille and the Minderoo Foundation are considering using for a national study on the extent of seafood fraud in Australia, the likes of which has never before been attempted.

But genetic testing is expensive, and verifying where seafood products come from – whether they are wild-caught or farmed, from sustainable stocks or not – is a tougher task.

“Seafood provenance can be a much trickier problem [than species authentication] because you can have the same species swimming around in two different water bodies or one stock has been fished sustainably and one hasn’t,” says Doubleday.

But as vast as the oceans may be, seawater contains trace minerals and elements that leave some clues in seafood, if you know where to look.

Doubleday is looking at chemical markers in the shells of shellfish, and in the teeny ear bones of fish and octopus, which are called otoliths and statoliths, respectively. These bony structures, made of calcium carbonate, absorb elements such as oxygen from seawater. The elements are present in various forms, called isotopes.

In the ocean, oxygen isotopes vary with sea surface temperature and salinity, so much so that these chemical markers entrapped in bone can be used to figure out whether an animal was caught in Asia’s tropical waters or sourced from southern Australia’s temperate seas.

“It’s going back to some basics of fundamental research,” Doubleday says. “But the beauty of this [approach] is that it can help track where an animal has come from.”

Unlike trace elements, which are easy to measure in fleshy tissues but fluctuate over time and between species, Doubleday says oxygen isotopes locked away in bony, mineralised tissues are very stable, and therefore predictable, chemical markers of seafood provenance – which makes them particularly useful for testing a smorgasbord of species.

The first step is to map ocean chemistry, starting with oxygen isotopes, after which Doubleday plans to plot oceanic variations in other, more stable trace elements that also accumulate in bony tissues. Overlaying these maps could more precisely geolocate seafood products along latitudinal and longitudinal lines. “A resolution of hundreds of kilometres is what we’re aiming for,” she says.

Like a lot of traceability tools being developed, the technology is still in its infancy, and Doubleday and her team are working on validating their maps by testing seafood samples sourced directly from local fishers before investigating products of unknown or suspect origin.

She says the technique could be used to audit seafood products at the processing stage, where bones are usually discarded, but other tools would be needed to verify the origins of fish fillets sold in store or abalone shucked at sea.

One possibility is a portable scanner that detects levels of up to 32 trace elements in seafood flesh that indicate what the animal ate and where it lived, whether it was farm-fed or lived in open ocean. The hand-held scanner is on par with lab testing for accuracy, so it could be used to quickly verify the source of seafood sold in marketplaces and restaurants, where wild-caught products may fetch a higher price.

So far, nuclear scientist Debashish Mazumder and his team at ANSTO have compared farmed and wild-caught tiger prawn, snapper, barramundi, oyster and yellow fin tuna from around Australia and parts of Asia.  

But it’s painstaking work. For each species, seafood samples need to be collected and tested and elemental profiles combined with isotopic analyses, in order to build a reference database that feeds into a computer model to generate a prediction of the seafood’s source.

Mazumder has also worked with Doubleday to trace the origins of octopus from Tasmania to Vietnam, looking at stable isotopes in their poppy-seed-sized statoliths and the elemental profile of their muscle tissue.

With consumer interest in seafood provenance growing fast, Mazumder says the industry and its regulators will probably need to use a toolkit of techniques to verify where seafood comes from, how it was sourced and what species it is. “No one particular technology, no one analytical method, is sufficient to determine the provenance source of seafood,” he says.

Doubleday adds that beefing up Australia’s seafood import policies could help to incentivise the development of technologies for testing seafood provenance, in that seafood suppliers, distributors and wholesalers would need to report where their seafood comes from.

Introducing stricter reporting requirements for the roughly 230,000 tonnes of seafood imported into Australia each year would also help to deter illegal fishers who trade on seafood fraud and give fisheries a fighting chance, says Travaille.

“Seafood fraud is something that occurs as a result of poor traceability, transparency and accountability in seafood supply chains,” she says.

But if you shut off the market access to fraudulent operators, as the US and European Union have done, Travaille says, “it eliminates them having a place to sell their product, which makes it unprofitable to carry on fishing the way that they are.

“While [Australia] might not be a huge global player, it’s about systematically closing those doors… so that there is eventually nowhere to sell that product.”