Researchers found traces of cocaine in every Brazilian sharpnose shark they examined.
Fish ingesting microplastics is bad enough, but a new analysis points to additional man-made problems. According to a study published July 15, 2024 in the journal Science of the Total Environment, scientists from Brazil's Oswaldo Cruz Foundation have confirmed traces of cocaine and its main metabolite, benzoylecgonine, in at least 13 Brazilian sharpnose sharks purchased from commercial fishermen in Rio de Janeiro. As IFL Science notes, this is the first ever detection of the drug in wild sharks.
Like countless other man-made pollutants, drugs discarded or lost in illegal international trade often end up in the ocean, where they can poison wildlife and contaminate ecosystems.
Just last 2023, for example, authorities discovered large bales of cocaine floating in the waters off the coast of New Zealand. But while researchers had previously studied the stimulant's effects on animals such as eels and zebra fish, experts knew almost nothing about sharks' interactions with the drug (aside from some vague experiments related to "Shark Week" in 2023).
Thanks to researchers from Brazil, however, marine biologists now have a definitive, albeit sad, answer: sharks definitely don't mind trying abandoned cocaine if they happen to stumble upon it in their natural habitat.
Researchers acquired more than a dozen Brazilian sharpnose sharks from local fishing boats around Rio de Janeiro between 2021 and 2023. This endangered species is most commonly found in the region's coastal waters and typically reaches between 0.5 and 0.7 meters in length and weighs up to 3 kilograms.
After weighing and measuring the samples, the team performed a necropsy, analyzing muscle and liver tissue. The results were conclusive - all of the sharks had traces of cocaine, an average of 23 micrograms per fish. What's more, 92 percent of the muscle samples and 23 percent of the liver samples contained benzoylecgonine, one of the drug's main metabolites.
Equally discouraging is that while experts now have concrete evidence that sharks ingest cocaine, they have yet to study how its chemical makeup might interact with the fish. Previous studies on zebra fish and eels, have shown that cocaine alters their skin, disrupts hormonal functions and changes important proteins in their systems. As with pollution, these problems don't necessarily stay in concentrated areas - they often spread far beyond where they originate.
"Although maximum allowable concentrations of cocaine and benzoylecgonine in food have not been established, these data indicate a potential risk to human health because sharks are widely eaten in the state of Rio de Janeiro," the study authors wrote. "In fact, they are eaten throughout Brazil and even worldwide."