Sharks and cocaine may seem like a ludicrous combo, but some experts say it might not be as insane as it sounds—particularly not in the waters around Brazil. There are several ways that cocaine enters the ocean: it can enter through leaky sewage treatment plants or by smugglers’ errant packages that end up in the sea and are chewed open by wildlife. Recent research from Brazil’s Oswaldo Cruz Foundation has found that sharks are testing positive for cocaine, providing evidence that drug contamination in the water is affecting these marine predators.
Researchers report this week in Science of the Total Environment that drug residues were found in the muscles and livers of 13 Sharpnose sharks from coastal waters close to Rio de Janeiro.
With a length of less than three feet (0.9 metres), the species is quite tiny and mostly consumes small fish and squid for food. Following the sharks’ capture, the researchers dissected them to extract samples of their livers and muscles, which were subsequently examined for the presence of cocaine and other related substances.
Shockingly, all 13 sharks tested positive for cocaine and 12 of them also contained benzoylecgonine in their systems, a substance that is created when cocaine passes through the liver. Additionally, the amounts were up to 100 times more than those previously documented for other aquatic animals.
Although the study was limited to Brazilian Sharpnose sharks, it is possible that other species were also exposed to drugs found in the water. Researchers mentioned that overfishing is causing a significant reduction in several shark species.
Cocaine exposure may cause serious health problems for sharks, such as damage to their DNA, disruption of their fat-metabolizing processes or behavioural abnormalities.
The researchers noted that because of the psychotropic effects of drugs of abuse on vertebrates, behavioural changes may arise. These changes, while not fatal, may have an impact on the survival of the species in ways that are still unknown.
According to the authors, these results point to possible health dangers for humans because sharks are widely consumed not just in Rio de Janeiro but also across the entirety of Brazil and the world.