Amazon’s pink river dolphins reveal the bizarre impacts of seafood fraud

This month, marine conservation NGO Oceana released a major report on seafood fraud, which reviewed more than 200 scientific studies that had collectively examined over 25,000 fish samples from around the world. Through its analysis, Oceana was able to show that an astonishing one in five seafood samples globally is mislabelled to represent other species and mislead consumers. Nestled within that report was the case of the Amazon river dolphins – a peculiar testimony to the often bizarre, trickle-down effects of seafood fraud.

These freshwater dolphins occupy the Amazon and Orinoco river basins that stretch across the northern half of South America. They have historically been abundant across this vast watery network, and are protected by law, making it illegal to kill them. But for years, poachers have been targeting the dolphins and using them as bait to catch a much smaller type of catfish.

Two species – the tucuxi and boto dolphins, the latter also recognisable as the charismatic ‘pink river dolphin’ – are at the centre of this trade. But what’s truly peculiar about this situation isn’t just the strange juxtaposition of dolphins being exploited to feed much smaller fish: it’s the identity of the fish they’re being killed to catch in the first place.

In South America, Haydée Cunha, a conservation geneticist at the Rio de Janeiro State University, has been investigating this problem ever since a mystery fish first started appearing in Brazilian grocery stores and street markets in 2008. In 2015 when she was at the Federal University of Rio de Janeiro, she produced a research paper on seafood fraud that was featured in the Oceana report: it detailed the findings of a survey carried out in Manaus, the capital of Brazil’s Amazonas state, which showed that a series of fictitious species names – ‘douradinha’, ‘douradinho’, and ‘piratinga’ – were all being used to describe the same type of fish. Using DNA tissue analysis, Cunha identified this species as a common catfish, known as C. macropterus.

“We found that 60% of fillets being sold as ‘douradinha’, ‘douradinho’ and ‘piratinga’ were actually C. macropterus,” Cunha says. The fraudulent names were deemed necessary to cover up the catfish’s true identity, she explains, because it is a scavenger fish that would repel buyers if they knew. “Brazilians find this catfish disgusting, because they know that it is necrophagous [carrion-feeding]. They refer to it as ‘water vulture’,” she says.

The original driver for this fraudulent trade was the overfishing of another, much preferred catfish species, the ‘capaz’, a regional delicacy that fetched a high price from consumers before its population began to dwindle. To replace the diminishing supply, fishers have since turned to C. macropterus, also known as ‘mota’. Because this particular species is drawn to carrion, large river dolphin carcasses – especially the larger pink boto dolphin – provide the ideal bait for attracting large numbers of these fish.

Boto and tucuxi dolphins aren’t currently listed as endangered; the International Union for Conservation of Nature describes their cases as ‘data-deficient’, meaning it can’t make a definitive estimate about how threatened they are. But there’s evidence of an increasingly sophisticated industry that’s sprung up around these creatures. “There are reports of dolphin hunters that supply the fishermen, and also of freezing plant owners that keep dolphin carcasses to supply fishermen,” Cunha says.

The trade has undoubtedly also grown over the years. Vera da Silva, an aquatic mammal researcher with the National Institute of Amazonian Research, who has been surveying boto dolphin populations for over 20 years, says that over the last decade its population has declined by 60% in one part of the Central Amazon. “The curve went down dramatically after 2000,” she notes – around the same time fishermen started to target the scavenging catfish.

Last year, a moratorium on fishing the C. macropterus catfish came into force, largely motivated by potential health impacts on humans, because the scavenging fish are also exposed to high levels of mercury. But despite the ban it’s suspected that the trade continues: enforcement is weak, Da Silva says, and in her research Cunha notes that it’s easy enough to invent new names for the species to hide its true identity.

Now Cunha and Da Silva are working together to use DNA analysis to identify signs of seafood fraud and track its spread. “We need to check markets regularly in search of new disguises –new fictitious names – for C. macropterus, and to use DNA to identify fillets,” Cunha says. She and her team are also currently developing a rapid diagnostic test that will be used to identify the stomach contents of mystery fish for traces of dolphin or caiman DNA (these reptiles are less favoured, but also targeted by fishers as bait.) This could help environmental officials pinpoint hotspots of illegal activity.

This month, Da Silva and other researchers will begin a new survey to monitor the densities of dolphins in parts of the Amazon. But from her point of view, the fishing moratorium, which will end in 2018, is too short. “Five years is not enough for the recovery for any kind of mammal,” she says; the boto breeds in three-year cycles, so population surveys won’t be able to provide a full picture of the how well or poorly the dolphins have fared in this time. But, she adds, “No matter how much [fishermen] are killing now, they are killing less than they were before the moratorium. So we need to show that it’s important to continue it for a longer period to allow the population to recover.”

Whatever the dolphins’ fate, their case reveals that far from simple name switching, seafood fraud is a front for a backlog of crimes being perpetrated against aquatic and marine life. How many other fraudulent species names might hide stories just like this one?