‘Cocaine sharks’ found in Brazil coastal waters sparking fears over increased aggression

Scientists have raised concerns that cocaine discarded into the ocean by drug traffickers could be impacting sharks and altering their behavior.

The alarming discovery was made after researchers suggested that sharks might be consuming the drug when illegal drug labs dispose of their chemical waste into the sea. The team also considered the possibility that the marine creatures were feeding on bales of cocaine that had been lost or thrown overboard by drug smugglers, although they deemed this unlikely.

However, the most probable explanation was that the sharks were absorbing the cocaine from sewage dumped into the ocean by drug users. British scientist Rachel Ann Hauser-Davis, a member of the research team from the Oswaldo Cruz Foundation in Rio de Janeiro, stated that the findings indicated "chronic exposure due to human use of cocaine in Rio de Janeiro and the discharge of human urine and faeces by sewage outfalls, as well as from illegal labs".

The scientists examined 13 Brazilian sharpnose sharks caught by local fishermen in the coastal waters surrounding Rio de Janeiro. All of the specimens were found to have high levels of cocaine in their systems.

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The study, which was published in the journal Science of the Total Environment, suggested that the cocaine-exposed sharks might be becoming more aggressive due to the effects of the addictive substance. "Cocaine targets the brain, and hyperactive and erratic behaviour has been noted in other animals. It's a possibility and further studies are required," explained Dr Enrico Mendes Saggioro, an ecotoxicologist from the Oswaldo Cruz Institute, reports the Mirror .

The shark species was selected for the study due to its lifelong habitation in coastal waters, where cocaine traces are believed to be most concentrated. Astonishingly, researchers discovered cocaine concentrations up to 100 times higher than previously found in other marine creatures in the sharks' muscles and livers.

While there's currently little evidence to suggest that the drug is causing the sharks to go into wild frenzies, it could have long-term effects on their health, warns one expert. Dr Tracy Fanara, a specialist in ecotoxicology and environmental engineering from the University of Florida, suggested that it might affect the sharks' growth rates and breeding levels.

"They may not be going nuts from the cocaine but it could reduce their life expectancy," she shared with the Telegraph. She has urged for more research into how man-made chemicals influence ecosystems and impact animals both on land and sea.