Cocaine sharks off Rio de Janeiro found with cocaine levels 100 times higher

Marine biologists examined 13 Brazilian sandbar sharks caught off the coast of Rio de Janeiro. Scientists from the Oswaldo Cruz Institute in Brazil bought the sharks from small fishing boats that caught these and other species and then conducted tests on them. According to the BBC, all samples tested positive, and the concentration of cocaine was even 100 times higher than previously reported in other aquatic species.

Scientists point out that the drug enters the water primarily from illegal laboratories, where cocaine is produced, as well as through the excrement of people using this drug. The source of cocaine in the water may also be packages thrown by smugglers.

Sara Novais, a marine ecotoxicologist at the Center for Marine and Environmental Sciences at the Polytechnic Institute of Leiria, told the journal "Science" that the discoveries are "very important and potentially concerning."

These findings are indicative of potential human health risks, as sharks are highly consumed in the state of Rio de Janeiro, in fact, throughout the entire Brazilian territory and indeed, worldwide – scientists add.

Last year, the media reported strange shark behaviour near the Florida Keys archipelago. American environmental engineer Tracy Fanara and British marine biologist Tom Hird described them. Their concern was raised by a sand shark swimming in circles as if trying to catch something researchers couldn't see. Equally disturbing was the behaviour of a hammerhead shark, which approached divers, although it usually avoids contact with humans.

Scientists began to suspect that drugs might influence the unusual behaviour of the sharks. This cannot be ruled out as Florida is on the drug trafficking route. Scientists then experimented with throwing identical packages meant to imitate drug packages into the water. No shortage of sharks tore the packages apart.