13 Sharks Off Brazil Coast Test Positive for Cocaine; Scientists Unsure About the Source of the Drug

In a study conducted on sharks off the coast of Brazil, marine biologists discovered high levels of cocaine in their muscles and livers. They believe the drug may be affecting the sharks’ behaviour.

The study, carried out by the Oswaldo Cruz Foundation in Brazil, involved 13 wild sharpnose sharks near Rio de Janeiro that tested positive for cocaine.

Theories on the Source

While the exact source of the drug is unknown, several theories exist. According to a paper published in the journal Science of the Total Environment, researchers suspect that the cocaine may come from drains connected to illicit drug labs. Another theory is that the drug might be entering the ocean from untreated sewage containing waste from drug users.

It is also suspected that sharks could be feeding on bales of cocaine dumped into the sea by drug smugglers. However, this scenario is considered less likely, as researchers note that the amount of cocaine bales dumped or lost at sea near Brazil is relatively low compared to places like Mexico and Florida.

Study Findings

The researchers found high concentrations of cocaine in them, up to 100 times higher than previously detected in other marine animals. This study marks the first evidence of cocaine found in free-ranging sharks. 

The 13 small wild sharpnose sharks, who were collected during fishing trips in the waters near Rio de Janeiro, were dissected, and their muscle and liver tissues were tested. The drug was found to be more prevalent in the muscle tissue than the liver.

The test results of the study found “chronic exposure” to cocaine in the sharks. Traces of benzoylecgonine, a major metabolite of the drug, were also found in 92 percent of the muscle samples and 23 percent of the liver samples.

Potential Impact on Sharks

While the extent of the effects of the drug on the sharks isn’t known, scientists worry that it could be causing damage to them by impairing their vision and hunting abilities and potentially reducing their life expectancy.