Researchers in Brazil have found traces of cocaine in over a dozen sharks near Rio de Janeiro, alarming activists.
Researchers reported finding traces of cocaine in the muscles and livers of thirteen Brazilian sharpnose sharks collected from coastal waters near Rio de Janeiro, with concentrations up to 100 times higher than those reported in other aquatic species.
The findings in the latest issue of Science of the Total Environment are “very important and potentially worrying”, said Sara Novais, a marine ecotoxicologist at the Marine and Environmental Sciences Centre of the Polytechnic University of Leiria told Science.
There has been concern among wildlife activists that drugs dumped into the ocean by smugglers could affect marine life, especially given the large quantities of cocaine found around Florida and in South and Central America.
Around Rio de Janeiro, cocaine likely enters the sea through drainage from illegal labs where the drug is processed, as well as from untreated sewage from drug users.
Researchers from the Oswaldo Cruz Institute in Brazil bought the sharks from small fishing vessels that target the species and others and then conducted tests on them. All samples tested positive, with cocaine concentrations up to 100 times higher than those previously reported in other aquatic species.
Exposure to cocaine could severely impact shark health, potentially damaging their DNA, impairing their ability to metabolise fats, and causing behavioural changes, the findings revealed.
“Considering the psychotropic effects of drugs of abuse on vertebrates, behavioural changes may occur, which, although sub-lethal, could impact the species’ survival in ways that remain unexplored,” the researchers wrote.
The sharpnose shark is relatively small, growing to under three feet (0.9m) in length, and primarily feeds on small fish and squid.
“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,” the researchers noted.