Cocaine sharks: Brazilian study shows marine predators 'high' on drug

Sharks off the coast of Brazil tested positive for cocaine, leading scientists to believe that the drug may be affecting their behaviour. Marine biologists studying 13 Brazilian sharpnose sharks from waters near Rio de Janeiro discovered high levels of cocaine in their muscles and livers.

While the exact source of the cocaine remains unclear, theories suggest it could be from the drainage of illegal drug labs or untreated sewage from drug users as per officials. Another possibility is that the sharks might have ingested cocaine bundles lost or discarded by smugglers, though experts say this is unlikely in this region compared to places like Mexico and Florida.

The study found "chronic exposure" to cocaine in the sharks, with concentrations up to 100 times higher than previously observed in other marine animals. The research revealed that all shark samples tested positive for cocaine, with 92 percent of muscle samples and 23 percent of liver samples also showing traces of benzoylecgonine, a main metabolite of the drug.


Dr Enrico Mendes Saggioro, an ecotoxicologist, noted that while cocaine is likely harmful to the sharks, its exact impact on their behaviour remains unknown. “This may be the case, as cocaine targets the brain, and hyperactive and erratic behaviour has been noted in other animals. It's a possibility and further studies are required,” he said.

The sharks were collected during fishing trips near Rio de Janeiro, and researchers worry that the cocaine could be impairing their vision and hunting abilities, potentially reducing their life expectancy. While the full extent of the drug's impact on these marine predators is still under investigation, the findings mark the first evidence of cocaine in free-ranging sharks