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Marine biologists from the Oswaldo Cruz Foundation in Rio de Janeiro have discovered that thirteen Brazilian sharpnose sharks caught off the coast of Rio de Janeiro tested positive for cocaine. Researchers identified high concentrations of cocaine in the sharks' muscles and livers. They also detected benzoylecgonine, a byproduct of cocaine metabolism.

Key Point:

• Have any other marine animals or fish been impacted by cocaine in the ocean?
• Past Research on Cocaine's Impact on Sharks

Courtesy Source : Dwanye Oxford

Courtesy Photo : on

Study Findings

The study examined 13 sharks, consisting of three males and ten females, five of which were pregnant. These sharks were captured by fishing boats off the coast of Rio de Janeiro between September 2021 and August 2022. Samples taken from the sharks showed cocaine concentrations more than 100 times higher than previously reported in any other aquatic animals. Additionally, the study found that cocaine levels were three times higher in the sharks' muscles compared to their livers.

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Reasons for Sharks Testing Positive for Cocaine

Further research is needed, but the study suggests that the primary reason is the increase in cocaine use among people.

The rise in cocaine consumption in the region, combined with inadequate drainage systems, has led to higher quantities of cocaine being present in seawater.

The study states: “Global cocaine consumption has increased exponentially in the last decades, as highlighted in the United Nations World Drug Report. About 22 percent (4.8 million) of the estimated 22 million cocaine users worldwide reside in South America as of 2021, with Brazil emerging as the second largest consumer market in this area.”

The study also noted that sewage analysis, covering 60 million people in 37 countries from 2011 to 2017, consistently revealed the presence of cocaine in aquatic environments.

Previous Studies on the Effect of Cocaine on Sharks

In 2023, the documentary "Cocaine Sharks" followed marine biologist Tom Hird and environmental scientist Tracy Fanara as they investigated what happens when sharks come into contact with cocaine in the Florida Keys.

The Florida Keys is a known hotspot for drug trafficking. In July, federal authorities reported that former police officer and Tampa Mayor Jane Castor found the fifth-largest load of illegal drugs ever while on a fishing trip off the Florida Keys. Castor reported the discovery to the United States Border Patrol. According to Chief Patrol Agent Walter Slosar with the Border Patrol’s Miami sector, the 32 kg (70 lb) of cocaine had an estimated street value of $1.1 million.

Last month, a recreational boater in the Florida Keys found 30 kg (65 lb) of cocaine with a street value of $1 million floating in the sea.

The documentary was inspired by rumors among fishermen that sharks were encountering bales of cocaine due to drug traffickers frequently dumping cocaine from planes off the Florida coastline. The belief was that the cocaine was leaking into the sea.

Additionally, drug traffickers are known to dump cargoes of illegal drugs into the sea if they fear being caught by the coastguard.

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Other Instances of Drug Trafficking and its Effects on Sharks

Drug traffickers often use a delivery system where they wrap cocaine in multiple layers of plastic and other waterproof materials and drop it into the water to be picked up by another boat. For instance, in February 2023, police in New Zealand discovered 3.2 tonnes of cocaine worth $300 million floating in the sea. Similarly, in 2019, authorities intercepted a submarine carrying 3 tonnes of cocaine worth $110 million off the coast of Spain.

In one experiment conducted by Hird and Fanara, fake cocaine bales and plastic swans were dumped into the water to see which the sharks would approach first. The sharks appeared to attack the bundles first, but the reasons for this behavior remain unclear.

Experts also remain uncertain about how cocaine affects sharks physiologically. According to Florida International University biological scientist Laura Garcia Barcia, who spoke in July last year on National Geographic’s "When Sharks Attack and Why," a few studies show that cocaine affects fish very differently than it affects humans. In sharks, cocaine acts as an anesthetic, while it acts as a stimulant in humans.

A 2016 study by toxicology researchers from the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and Zurich University found that giving cocaine to zebrafish did not produce the same stimulating effect as it does in humans. Using a sophisticated imaging method to analyze tissue samples, researchers discovered that cocaine accumulated in the eyes of zebrafish rather than in their brains, as it does in humans.

“If we want to have a better understanding of the effects of such chemicals on the ecosystem, we need a more detailed understanding of the processes of uptake through water. These processes are quite different from when drugs are inhaled or injected,” said Eawag environmental toxicologist Kristin Schirmer, co-author of the study.

Impact of Cocaine on Other Aquatic Animals

Biologists at the University of Naples Federico II conducted a study in 2018 where they submerged European eels in water containing small quantities of cocaine, similar to the levels found in many rivers. After living in this environment for 50 days, the eels exhibited hyperactive behavior.

This finding has raised concerns among environmentalists and biologists that the presence of cocaine in rivers could pose significant health problems for certain fish species.

In 2021, researchers from the Universidade Estadual Paulista and the Universidade de São Paulo in Brazil conducted another study on the presence of cocaine and benzoylecgonine in the seawater, sediment, and mussels of Santos Bay, Brazil. The researchers discovered widespread contamination by cocaine and its main human metabolite, benzoylecgonine, in Santos Bay. They also found that mussels were able to accumulate cocaine as a result.

Courtesy Source: www.aljazeera.com/news/2024/7/26/why-have-brazilian-sharks-tested-positive-for-cocaine