Emily Chan
Off the coast of Brazil, sharks have tested positive for cocaine. It is the first time that the substance has been identified in free-ranging sharks. So, how did these sharks get access to the drug?
Cocaine can enter the ocean through sewage discharge from humans who use the substance, as well as the illegal laboratories that produce it. Smugglers also drop stray packets in the water that ultimately get bitten open by marine creatures.
Previous studies have shown the presence of the drug in mollusks, crustaceans, and bony fish. Between 2011 and 2017, traces of cocaine were detected in the sewage and surface waters of at least 37 countries.
In recent decades, cocaine consumption has increased significantly all over the world. Around 22 percent of cocaine users live in South America. Brazil is the second-largest consumer market in the region. The combination of increased cocaine consumption and inadequate sewage treatment infrastructure has led to higher levels of cocaine in the sea.
Scientists tested 13 Brazilian sharpnose sharks from the waters off the coast of Rio de Janeiro. The species measures under three feet in length and feeds mainly on squid and small fish. When the scientists analyzed tissue samples of the sharks’ muscles and livers, they found the presence of cocaine in all 13 specimens.
The species was chosen for this study due to its small size and the fact that it lives in an area where it is exposed to contaminants throughout its entire life. Cocaine levels were about three times higher in muscle tissue than in liver tissue.
Female sharks had higher concentrations of cocaine in their muscle tissue than males. All the sharks except one had benzoylecgonine in their systems, which is a chemical that is produced when cocaine is filtered through the liver.
In this part of the world, the high levels of cocaine contamination were not from traffickers dumping the substance into the sea. Researchers say that phenomenon is not as prevalent in Brazil as it is in Mexico and Florida.
The study focused on Brazilian sharpnose sharks, but other species may have been exposed to the drug as well. The study authors noted that many species of sharks are facing declines in their populations because of overfishing.
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