Study finds cocaine, caffeine and painkillers in sharks off Eleuthera, Bahamas

Sharks off the coast of Eleuthera have been found with traces of cocaine, caffeine and common painkillers in their blood, according to a new study highlighting the growing impact of human pollution on marine life in The Bahamas.

The peer-reviewed research, published in Environmental Pollution, detected what scientists describe as “contaminants of emerging concern” in several shark species inhabiting nearshore waters. The study marks the first recorded presence of caffeine and acetaminophen in sharks globally, and the first detection of diclofenac and cocaine in sharks in The Bahamas.

Researchers analysed blood samples from 85 sharks, including tiger, blacktip, Caribbean reef, Atlantic nurse and lemon sharks. Four substances — caffeine, cocaine, acetaminophen and diclofenac — were identified in 28 sharks across three species: Caribbean reef sharks, Atlantic nurse sharks and lemon sharks.

Caffeine was the most frequently detected compound, found in multiple individuals across all three affected species. Cocaine appeared in two sharks, while acetaminophen and diclofenac were detected in smaller numbers but across multiple species.

Scientists say the findings are particularly concerning because sharks are apex predators that play a critical role in maintaining marine ecosystems. In The Bahamas, they also support a significant tourism industry centered on shark diving and conservation.

The study focused on coastal sites in south and central Eleuthera, with the highest concentrations of contaminants recorded near an aquaculture cage. Researchers suggest the pattern reflects human activity, including vessel traffic and wastewater discharge, particularly in areas popular for shark-diving excursions.

While the study does not confirm that these substances are directly harming sharks, it identified differences in biological markers between contaminated and uncontaminated animals. These variations may point to changes in metabolism or stress responses, though researchers caution that no direct cause-and-effect relationship has been established.

They also noted that the contaminants were found only in some animals and that blood samples mainly indicate recent exposure rather than long-term buildup.

Even so, the presence of these substances underscores the expanding reach of human-derived pollution in Bahamian waters. Researchers point to tourism development, coastal housing and wastewater discharge as likely sources, with caffeine identified as a key indicator of human contamination.

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The study was conducted by scientists from the Cape Eleuthera Institute and international partners, using non-lethal methods to collect and analyse shark blood samples before releasing the animals back into the wild.