Sharks off the coast of Brazil have cocaine in them and scientists believe the drug may be altering their behaviour. In a study conducted on 13 Brazilian sharpnose sharks from waters near Rio de Janeiro, marine biologists found high levels of cocaine in their muscles and livers.
While it is not known how the sharks have been feeding on the drug, some theories exist. Scientists believe that the cocaine likely came from the drainage of illegal labs that produce drugs or from the excrement of drug users through untreated sewage.
It could also be that the sharks fed on bundles of cocaine that were lost or dumped in the sea by drug smugglers. “We don't usually see many bales of coke dumped or lost at sea here, unlike in Mexico and Florida,” a scientist told The Telegraph, asserting that it was highly unlikely the sharks had been eating cocaine from dumped packages.
According to scientists, the test results showed “chronic exposure" to cocaine in the sharks.
While they estimate that the cocaine was harmful to them, it is not known to what degree the drug could have affected their behaviour or if 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 researchers, who picked the small sharks from the water on fishing near Rio de Janeiro, dissected them and tested their organs. In a worrying finding, they found concentrations of cocaine up to 100 times higher than previously found in other marine animals.
The results of those tests revealed that every single sample from the sharks tested positive for cocaine, with 92 percent of muscle samples and 23 percent of liver samples also testing positive for one of the drug's main metabolites, benzoylecgonine. This marks the first evidence of cocaine being identified in free-ranging sharks.
While the extent of the damage to the animals from the cocaine is not known, scientists suspect that one way the drug can affect the sharks is by damaging their eyesight, affecting their capacity to hunt.
They may not be going nuts from the cocaine but it could reduce their life expectancy, a scientist said.
