Sharks test positive for cocaine-contamination off Brazilian coast, scientists unsure of origin

Marine biologists have discovered significant levels of cocaine in the muscles and livers of Brazilian sharpnose sharks near Rio de Janeiro, raising concerns about the potential impact of the drug on marine life. The study, conducted on 13 sharks, revealed that all tested positive for cocaine, with concentrations up to 100 times higher than those previously found in other marine animals.

The origins of the cocaine contamination remain unclear, though scientists propose several theories. It is speculated that the drug could have entered the marine ecosystem through the drainage of illegal drug production labs or from untreated sewage containing excrement from drug users. Another possibility is that the sharks ingested the drug from bundles of cocaine lost or dumped at sea by drug smugglers. However, one scientist noted that sightings of such bales are rare off the coast of Brazil, unlike in areas such as Mexico and Florida.

The test results indicated “chronic exposure” to cocaine in the sharks. Dr Enrico Mendes Saggioro, an ecotoxicologist, commented on the findings, stating, “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.” The degree to which the drug affects the sharks' behaviour and health remains uncertain, though it is suspected to be harmful.

Researchers who captured the sharks for the study discovered that 92 percent of muscle samples and 23 percent of liver samples tested positive for benzoylecgonine, a primary metabolite of cocaine. This marks the first evidence of cocaine being identified in free-ranging sharks.