Caviar, made from sturgeon eggs, is appreciated as the height of luxury, and the expensive delicacy is likely to feature on many menus over the upcoming festive season.
But how can consumers be certain whether the caviar on their plate has been legally produced - or is even authentic?
The answer seems to be that they can't.
A recent study by a German-led expert team of biologists specialising in sturgeon found that half of the commerical caviar products they sampled contained illegal caviar, while some of them contained no trace of sturgeon at all.
Wild caviar is illegal, with all caviar-producing European sturgeon species - Beluga, Russian, stellate, and sterlet - designated as endangered since 1998. The last remaining wild populations of these species in the European Union are found in the Danube River and the Black Sea.
Today, legal caviar can only be produced through aquaculture, while a strict international labeling system exists for all caviar products in an effort to prevent illegal trade.
That doesn't seem to have stopped poachers and seafood fraudsters, however, as the results of this latest study shows.
The caviar samples used in the study came from Bulgaria, Romania, Serbia, and Ukraine - all countries bordering the remaining wild sturgeon populations.
In an effort to discover the true source of commercially-available caviar products, the researchers purchased samples online and in person from a wide variety of sources including local markets, shops, restaurants, bars, and aquaculture facilities. In total, they collected 149 samples of caviar and sturgeon meat, analysing their DNA and isotope patterns, including five samples that had been seized by authorities.
The research team found that 21% of the samples originated from illegally wild-caught sturgeons, which were on sale in all of the countries studied.
Meanwhile, 29% of the samples violated international regulations and trade laws, for example by listing the wrong species of sturgeon or incorrect country of origin.
A further 32% of samples were categorized as committing "customer deception", for example, products labelled as "wild" that were actually produced from aquaculture.
Three of the samples, which were served in Romania as “sturgeon soup,” contained no trace of sturgeon. The researchers instead identified the fish ingredients as European catfish and Nile perch.
The researchers suggest that continuing consumer demand for wild caviar products encourages the illegal trade. Low incomes for seafood vendors, combined with sturgeon poaching being seen as "low priority" for law enforcement, contribute to the problem. In addition, the researchers note, local authorities may lack the resources or technology to establish whether fish products have an illegal origin.
“Our results indicate an ongoing demand for wild sturgeon products, which is alarming, since these products endanger wild sturgeon populations,” write the researchers.
“The persistent demand fuels poaching and indicates that consumers do not fully accept aquaculture products as a substitute. In addition, caviar being sold in violation of CITES and EU obligations questions the effectiveness of controls in general and the labelling system in particular.”
“Although poaching and illegal wildlife trade are often considered a problem in developing countries, these findings bear evidence that a high ratio of poached sturgeon products originates from EU and accession candidate states,” the authors write.
“The control of caviar and sturgeon trade in the EU and candidate member states urgently needs improvement to ensure that Danube sturgeon populations will have a future.”
The research, led by Professor Arne Ludwig of the Leibniz-Institute for Zoo & Wildlife Research, was supported by funding from an EU-LIFE project, and is published as Ludwig et al. “Poaching and illegal trade of Danube sturgeons" in the journal Current Biology.