Sharks Test Positive for Cocaine: New Study Reveals Human Impact on Marine Life.
Recent research has uncovered a disturbing new dimension of human impact on marine ecosystems: the presence of cocaine in sharks. A study published on July 15 in Science of the Total Environment by researchers from Brazil’s Oswaldo Cruz Foundation has identified trace amounts of cocaine and its principal metabolite, benzoylecgonine, in at least 13 Brazilian sharpnose sharks.
These sharks were acquired from commercial fishers in Rio de Janeiro, marking the first documented instance of cocaine detection in wild sharks.
The presence of drugs in the marine environment is a growing concern. As with other pollutants, substances discarded or lost during illegal drug trafficking can end up in the ocean, posing risks to wildlife and ecosystems. For example, authorities recovered large bales of cocaine floating off the coast of New Zealand last year.
While previous studies have explored the effects of stimulants on species such as eels and zebrafish, there has been limited research on how such substances affect sharks.
The Brazilian study provides clear evidence that sharks can ingest cocaine if it is present in their habitat. Between 2021 and 2023, researchers purchased over a dozen Brazilian sharpnose sharks from local fisheries near Rio de Janeiro.
This species, which is typically found in the coastal waters of the region, averages between 1.7 and 2.3 feet in length and weighs up to 6.6 pounds.
After conducting necropsies on the sharks, including analysis of muscle and liver tissues, the researchers found that all the sharks tested positive for trace amounts of cocaine, averaging 23 micrograms per fish. Specifically, 92 percent of muscle samples and 23 percent of liver samples contained benzoylecgonine.
The study underscores a significant concern: while concrete evidence of cocaine ingestion in sharks is now available, the potential biochemical effects on these animals remain unexplored. Previous research on zebrafish and eels has demonstrated that cocaine can alter skin structure, disrupt hormonal functions, and impact critical proteins.
Moreover, pollutants like these often spread beyond their initial contamination sites, potentially affecting broader environmental and food chain dynamics.
The study's authors highlight the potential human health risks associated with these findings, noting that sharks are a commonly consumed species in Rio de Janeiro and across Brazil.
As there are currently no established maximum permissible concentrations for cocaine or benzoylecgonine in foodstuffs, the implications of these results warrant further investigation to assess their impact on both marine life and human health.
