Sharks taken from the waters off the coast of Brazil have tested positive for cocaine, with wild theories emerging about how they came to ingest the drug.
Researchers bought thirteen sharpnose sharks from fishermen operating near Rio de Janerio.
The sharks were dissected and their liver and muscle tissue tested for cocaine with all the samples coming back as positive.
The concentration of cocaine was as much as 100 times higher than had been previously recorded in other marine animals.
The results have confirmed long held fears that drugs are affecting sea life.
Alamy Stock Photo
The research was taken out by six Brazilian research groups, alongside the Cape Eleuthera Institute in the Bahamas and published in the science journal Science of the Total Environment.
Theories of where the cocaine comes from include a spillover from an illegal drug lab or from the excrement of drug users.
Another theory is that they could have been feeding off bundles of cocaine that were lost or dumped in the sea by drug traffickers.
While it is not known how the drug affected the sharks it is possible it made them more aggressive and unpredictable.
“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,” said Dr Enrico Mendes Saggioro, an ecotoxicologist.
The results showed “chronic exposure due to human use of cocaine in Rio de Janerio and the discharge of human urine and faeces by sewage outfalls, as well as from illegal labs,” said Dr Rachel Ann Hauser-Davis, a British scientist and member of the research team from the Oswaldo Cruz Foundation in Rio de Janerio.
Scientists said their findings were “worrying” for the marine ecosystem.
There are also fears that exposure to cocaine will damage sharks’ eyesight, affecting their ability to hunt.
Dr. Tracy Fanara, an expert in ecotoxicology and environmental engineering from the University of Florida, said the drugs could also affect sharks’ life-expectancy.
“They might not be going nuts from the cocaine but it could reduce their life-expectancy,” she said.
The findings comes after a 2023 documentary called Cocaine Sharks in which filmmakers tried to establish whether sharks in The Gulf of Mexico were consuming the hundreds of packages of cocaine lost or dumped in the sea every year by drug smugglers.
They found that if they dumped dummy packages of drugs in the ocean the sharks would swim up and take bites but it was not known if they had consumed actual drugs.
