'Cocaine Sharks' discovered: Scientists expect 'erratic behaviour' as marine animals taste narcotic substances

Sharks off the coast of Brazil have been found to contain cocaine and which the scientists suspect may be altering their behaviour. In a study conducted on 13 Brazilian sharpnose sharks near Rio de Janeiro, marine biologists found that they all had high levels of cocaine in their muscles and livers.

In a paper for the journal ‘Science of the Total Environment’, the marine biologists said the drug probably originated in drainage from illicit labs where cocaine is manufactured, or from the excrement of drug users, via untreated sewage.

“It might even have come from the sharks feeding on bales of cocaine that were lost or dumped overboard by drug smugglers – but that was less likely.”

According to The Telegraph report, citing Dr Rachel Ann Hauser-Davis, a British scientist and member of the research team said the results showed “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.”

She also told The Telegraph that there usually aren't many bales of coke dumped or lost at sea in Rio de Janeiro, unlike in Mexico and Florida.

Dr Rachel said the cocaine was probably harmful to the health of the animals, however, it is not known if it affected their behaviour, rendering them more aggressive and unpredictable or making feeding frenzies more likely.

“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 from the Oswaldo Cruz Institute.

One of the ways cocaine may damage the health of sharks, according to the experts, is by affecting their eyesight, affecting their capacity to hunt.

“You might start to see lower fecundity and growth rates,” Dr Tracy Fanara, an expert in ecotoxicology and environmental engineering from the University of Florida, told The Telegraph. However, she agreed that there was no evidence, as yet, to suggest that cocaine encouraged crazed behaviour or feeding frenzies in sharks.