Cocaine flushed into rivers is making critically endangered eels “hyperactive” and threatening their survival, new research suggests.
Traces of the drug routinely make their way into Britain’s waters after passing through users’ bodies. And could be causing serious health problems for some fish, according to the study.
Previous research has found residues of illegal drugs. Including cocaine, amphetamines, and ecstasy in European lakes and rivers, including the Thames.
The drugs end up in surface waters in highly populated areas after passing through sewage treatment plants, but scientists say little is known about the ecological impact.
In the new study, biologists at the University of Naples Federico II put European eels in water containing a small dose of cocaine – similar to the amount found in rivers – for 50 days.
They found the fish “appeared hyperactive” compared to eels which had not been kept in waters containing cocaine.
The drug accumulated on the brain, muscles, gills, skin and other tissues of the cocaine-exposed eels, researchers said.
The eels’ skeletal muscle showed evidence of serious injury, including muscle breakdown and swelling. Which had not healed 10 days after they were removed from the drug-contaminated water?
“This study shows that even low environmental concentrations of cocaine cause severe damage. To the morphology and physiology of the skeletal muscle of the silver eel. Confirming the harmful impact of cocaine in the environment that potentially affects the survival of this species,” said the authors of the study, published in Science of the Total Environment.
European eels spend their first five to 20 years in fresh or brackish water. Before migrating more than 3,700 miles to their breeding ground in the Sargasso Sea, a region of the North Atlantic Ocean. From there, the eels’ larvae drift for nearly a year back towards Europe.
But numbers of young eels arriving in the continent have dwindled by more than 90 percent since the 1980s, according to the IUCN “red list” of threatened species.
Anna Capaldo, a research biologist and lead author of the study, said the increased dopamine levels caused by cocaine may stop eels reaching sexual maturity.
“It is likely that in this condition, the reproduction of the eels could be impaired,” she told National Geographic.
She added: “All the main functions of these animals could be altered.”
Scientists In 2015 at the European Monitoring Centre for Drugs and Drug Addiction revealed London to have Europe’s highest concentration of cocaine in sewage, with the average daily concentration of the substance in wastewater at 737mg per 1,000 people.
In 2005, a team of researchers in Italy found large quantities of a cocaine by-product called benzoylecgonine – found in the urine of the drug users. In the River Po in northern Italy, carrying the equivalent of nearly 4kg (8.8lb) of cocaine on a daily basis.
What do WE know about EUROPEAN EELS?
Eels begin life as larvae called Leptocephalus, but despite the efforts of modern science, virtually nothing is known about how they reproduce.
European eels reproduce in the North Atlantic’s the Sargasso Sea, about 5,000 km (3,100 miles) from Europe’s shores.
The larvae travel to coasts and grow into small transparent fish called ‘glass eels.’
Glass eels grow into golden yellow ‘elvers’ and make their way into rivers. Streams, and creeks to feed on insects, worms, and smaller water organisms. They can be found anywhere on the coasts between Norway and Egypt.
They can take 10 to 15 years to mature, and eventually become ‘silver eels’ about three feet (one meter long). With a dark-grey coloring on their back and silver bellies.
The European eel is classified ‘critically endangered’ by the International Union for Conservation of Nature and Natural Resources.
The cause for the decline in eel population is not known, but excessive fishing, the presence of polychlorinated biphenyl pollutants. Used in industry, and a viral infection is suspected by the scientific community.