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A research has found sharks living off the coast of Brazil positive for cocaine after they were tested. 13 Brazilian sharpnose sharks in the waters off the city of Rio de Janeiro were tested. The scientists found cocaine present in both the liver and muscle tissue of all 13 specimens.
The species was chosen due to its small size and the fact that it lives in a small area of coastal waters, where it is exposed to significant contaminant discharges for its entire life cycle, according to the study. Cocaine levels were around three times higher in muscle tissue than liver tissue, according to the study, while female sharks had higher cocaine concentrations in muscle tissue compared to males.
Around 22% of users live in South America, the paper added, with Brazil the second largest consumer market in the region. Increased consumption and poor sewage treatment infrastructure has made for increased cocaine levels in the sea.
Previous research suggested that cocaine dumped at sea by traffickers could be responsible for contamination, but that is not the case here, said Mendes Saggioro.
“We don’t usually see many bales of coke dumped or lost at sea here, unlike what is reported in Mexico and Florida,” he said.
Studies have not been conducted to determine whether cocaine damages the sharks’ health but previous research has shown that the drug harms other animals such as fish and mussels.
Sara Novais, a marine eco-toxicologist at the Marine and Environmental Sciences Centre of the Polytechnic University of Leiria, told Science magazine that the findings are “very important and potentially worrying".
All females in the study were pregnant, but the consequences of cocaine exposure for the foetuses are unknown, experts say. Further research is required to ascertain whether cocaine is changing the behaviour of the sharks.
Previous research has shown that drugs were likely to have similar effects on animals as they do on humans.
Lewis Musonye
