Fish ingesting microplastics is bad enough, but new analysis points to additional humanmade issues. According to a study published on July 15 in Science of the Total Environment, researchers at Brazil’s Oswaldo Cruz Foundation have confirmed trace amounts of cocaine and its main metabolite, benzoylecgonine, in at least 13 Brazilian sharpnose sharks purchased from commercial fishers in Rio de Janeiro. As IFL Science notes, this marks the first-ever detection of the drug in wild sharks.
Like countless other human-generated pollutants, drugs discarded or lost during illegal international trafficking efforts often wind up in the ocean, where they may then poison wildlife and contaminate ecosystems. Just last year, for example, authorities recovered large bales of cocaine floating in the waters off New Zealand’s coast. But although researchers have previously investigated the stimulant’s effects on animals like eels and zebrafish, experts knew very little about sharks’ interactions with the drug (apart from some nebulous Shark Week-related experiments in 2023).
Thanks to investigators in Brazil, however, marine biologists have a definitive, if unfortunate, answer: sharks are definitely open to sampling abandoned cocaine if they happen across it in their natural habitat. Between 2021 and 2023, researchers purchased over a dozen Brazilian sharpnose sharks from local fishing boats near Rio de Janeiro. The threatened species is most often found in the area’s coastal waters, and generally ranges between 1.7- and 2.3-feet-long while weighing as much as 6.6 lbs. After weighing and measuring their samples, the team then conducted necropsies analyzing muscle and liver tissues. The results were conclusive—every single shark tested positive for trace amounts of cocaine averaging 23 micrograms per fish. More specifically, 92 percent of muscle samples and 23 percent of liver samples contained benzoylecgonine, one of the drug’s main metabolites. (To be fair, one microgram is one-millionth of a gram, so there’s a heavy emphasis on the “trace” in “trace amounts.”)
[Related: Baby sharks stick to the shallows.]
What’s equally disconcerting is that, although experts now possess concrete proof of sharks ingesting cocaine, they have yet to study how its chemistry may interact with the fish. The previous studies on zebrafish and eels, however, showed cocaine altered their skin, disrupted hormonal functions, and changed important proteins within their systems. And like all environmental pollution issues, these problems don’t necessarily remain in concentrated areas—they often spread far beyond their points of origin.
“Although no maximum permissible concentrations for [cocaine] or [benzoylecgonine] have been established in foodstuffs, these findings are indicative of potential human health risks, as sharks are highly consumed in the state of Rio de Janeiro,” the study’s authors write. “In fact, [they are eaten] throughout the entire Brazilian territory and indeed, worldwide.”