The Great Boto Botch Job

There are many local legends about the magical powers possessed by botos, or the pink river dolphins of the Amazon. Don’t swim alone, parents warn their children, or a boto will kidnap you and take you to the underwater city of Encante. Look one in the eye and you’ll have nightmares for the rest of your life. Leave your wife unattended at night and a shape-shifting dolphin, disguised as a handsome man, will seduce and impregnate her. Yikes.

Folklore like this has long protected these South American river dolphins. People are both reverent and also little afraid of the creatures, which can grow more than eight feet long. So killing or eating the world’s largest freshwater cetaceans has long held a powerful taboo. Unfortunately, those protections seem to be breaking down. Botos are now being killed by the thousands for a ridiculous reason: Fishermen are slaying them to use as bait for a type of catfish absolutely no one wants to eat.

Allow me to explain.

The catfish in question is called Calophysus macropterus—known as “water vultures” in Brazil because they eat dead flesh. Unsurprisingly, because of this reputation, the catfish are considered revolting. Nevertheless, fishmongers have managed to create a market for the meat over the last decade thanks to an age-old branding trick: They simply changed the name. Hey, it worked for Chilean sea bass, dried plums, and soy milk—why not the water vulture? Sure enough, these days in the city of Manaus, frozen water vulture fillets sell like hotcakes under the name douradinha, with consumers none the wiser.

To prove there was something, ahem, fishy going on, Haydée Cunha, a biologist at the Federal University of Rio de Janeiro, tested DNA taken from fillets at six Brazilian markets. Each claimed to be douradinha or one of several other made-up kinds of fish. Genetic analyses revealed that 60 percent of the fillets were actually from water vultures. Cunha, whose research is published in this month’s issue of the Journal of Heredity, also discovered that discarded catfish stomachs contained the flesh of botos.

Clearly this is a case of grievous consumer deception—but why murder a legendary dolphin as part of the fraud? Especially when doing so is punishable by two to five years in prison, fines, and the forfeiture of your boat under Brazil’s Environmental Crime Law?

Because boto meat is stinky—really stinky—and the reek, or pitiú, is the key to catching loads of catfish. “Fishermen leave the carcasses rotting before using them,” says Cunha, “precisely to improve their scent.” Water vultures will bite on myriad types of bait, he says, such as other catfish, cattle guts, or pig fat, but the fishermen are adamant that dead dolphins catch the most water vulture per pound. In fact, the practice is now so entwined with the douradinha industry that some fishermen have started to specialize as dolphin hunters, selling 200-pound boto carcasses to the catfish fishermen for $50 a pop. That one carcass is apparently enough bait to catch more than a metric ton of catfish in a single night.

Trapping the dolphins isn’t particularly challenging—fishermen simply target lagoons where females nurse their calves, says Cunha. Once they’re cornered, the hunters encircle the dolphins with nets and harpoon them. There’s even some graphic video of hunters butchering a pregnant female (warning: not for the faint of heart).

In 1994, scientists started traveling the central Amazon to see if they could pin down how many botos are out there and what may be hurting their populations. From small fishing villages to larger cities, the researchers found permanent boxes built into the riverbank where catfish are lured with bait and then trapped. Interviews revealed that not only was the use of dolphin bait common, but some communities routinely killed hundreds of botos each year. The city of Tefé alone is responsible for killing some 1,650 dolphins annually.

Meanwhile, standardized visual surveys have revealed that the Amazon river dolphin population has been dropping by about 10 percent each year since 2000. The decline, says Cunha, is “three times the highest sustainable rate.” How much of this is a direct result of the catfish trade is difficult to measure, especially since dams and other forms of development have been disrupting the dolphin’s habitat. The boto also competes with fishermen for fish, bringing them into conflicts that can end in death.

Interestingly, what may end up saving the dolphins is that water vultures are even more revolting than Brazilians realized—they are full of mercury. A 2014 study found that the average total mercury concentrations in water vultures caught in Brazil and sold in Colombia (where the douradinha industry has now spread) exceed safety limits set by the World Health Organization. As top predators, dolphins also accumulate high levels of mercury in their meat.

Worse still, some Brazilians don’t get to choose whether they dine on water vulture. One processing-plant owner cited in Cunha’s paper says that he’s sold douradinha—at an excellent price point—to the state of Amazonas. That means the mercury-laden catfish has likely found its way onto the plates of public school kids, hospital patients, prisoners, and the army.

Blessedly, there is some good news. Thanks to Cunha’s smoking-gun genetic evidence, the Brazilian Ministry of the Environment and Ministry of Fisheries kicked off a temporary moratorium on fishing for and selling water vultures. The ban went into effect this past January and is supposed to last for five years, at which point the government may reopen the fishery as long as dolphins aren’t used as bait.

Cunha says regular DNA analysis of catfish stomachs will be crucial to make sure fishermen don’t go back to their dolphin-killing ways. Meanwhile, enforcing the moratorium for the next half-decade is a whole other ball of pig fat. “Dolphins and caimans [which are also used for bait] are easily available,” says Cunha. "And although killing them is illegal, there is no surveillance in the vast Amazon.”

Still, unless they want to enter into a neurotoxin nightmare, they should beware the boto.