For the first time, scientists have detected the presence of cocaine in sharks, according to a new study published in Science of The Total Environment.
Knowing that Cocaine (COC) and benzoylecgonine (BE) have been detected in aquatic environments before, researchers at the Oswaldo Cruz Institute tested muscle and liver samples from 13 Brazilian sharpnose sharks (Rhizoprionodon lalandii). They found cocaine in all 13 sharks and BE (which comes from the metabolisation of cocaine) present in 12.
“The result is stunning. We found the substance in all 13 sharks analysed, and only one of them did not detect benzoylecgonine, which is the main metabolite of the drug," says pharmacist Enrico Mendes Saggioro.
- More than Jaws: 34 incredible, hard to believe shark facts that celebrate this fascinating, yet much-maligned fish
- Weirdest sharks: We take a deep dive into the ocean to discover some of its strangest creatures
Brazilian sharpnose sharks (top image) live near the coast so the researchers believe the contamination would have occurred close to where the samples were collected, not far from Rio de Janeiro. The drug could have got into the marine environment through sewage releases into the sea.
“The data draws attention to the high amount of the drug that is consumed in the city and discarded into the sea via sanitary sewage,” says the Oswaldo Cruz Institute in a press statement.
Surprisingly, they found a higher concentration of cocaine in the muscles than the livers. This could mean that the substance is abundant in their environment, and accumulating in their tissues, rather than that they’re ingesting it.
“Everything that is ingested is transformed by the liver to be excreted,” explains Mendes Saggioro. Finding higher concentrations of cocaine in the muscle “may signal the abundance of the substance's presence in the marine environment. The sharks would be contaminated in various ways, either by the fact that they inhabit the region or feed on other contaminated animals," he says.
In the movies, a cocaine-fuelled shark would wreak havoc on unsuspecting swimmers (in a low-budget 2023 movie, the cocaine creates mutant sharks that – spoiler – escape the lab) but, in reality, scientists are worried by what this could mean for the species, which is already listed as vulnerable to extinction by the IUCN Red List.
"Specific studies need to be carried out to determine the exact consequences of this contamination on animals,” says biologist Rachel Ann Hauser-Davis. “It is believed that there may be an impact on the growth, maturation and, potentially, fecundity of sharks, since the liver plays a role in the development of embryos."
Sharks play an important part in the ecosystem, she adds, so if this substance is harmful to them, there could be ripple effects throughout the food chain.
More research is needed to find out whether this could also harm human health – shark meat is often eaten (often called dogfish) and so “the health of one is linked to the health of the other,” says Hauser-Davis.
Main image: D Ross Robertson, Public domain, via Wikimedia Commons
