Toxic metals threatening endangered species of eels: Study

The endangered species of European eels is under threat from toxic metals that are polluting the rivers and lakes where they live, a study has found.

According to the researchers from University of Saskatchewan (USask) in Canada, eels eat up their own skeleton in their journey to the sprawling grounds where they lay eggs.

During this process they divert their energy to the reproductive system. However, the unique process is also concentrating toxic metals in eels' ovaries, researchers said.

The study, published in the Proceedings of the National Academy of Sciences (PNAS), found metals -- such as mercury, copper and other toxic industrial by-products -- in European eels that were about to lay eggs.

"Few people realise just how precarious the European eel population is," said Markus Brinkmann, a researcher at USask.

There has been a dramatic reduction in the numbers of young eels returning to Europe's rivers, lakes and coastal areas in the past 40 years, to the point that they are now critically endangered, according to Brinkmann.

"We need to act swiftly to save this species. Restoring environmental quality to rivers and lakes where they live should be an urgent priority," he said.

European eels can live up to the age of 80 years. They attain gleaming silver colour when reaching sexual maturity at around 15 years of age.

To breed, the eels swim 6,000 kilometres to their breeding ground in the Sargasso Sea, near Bermuda, consuming their own body as a source of energy before spawning and dying.

The research team, including scientists from RWTH Aachen University in Germany and Ghent University in Belgium, discovered that toxic metals stored in eels' bone and muscle are also 'mobilised' during their metamorphosis.

Brinkmann said toxic metals could hinder the eels' reproductive success, damaging eggs produced from the ovaries, and the health of eel larvae.

"The eels undergo dramatic changes to their bodies during their journey to their spawning grounds. The females look very different by the time they are ready to spawn. They look like just a sack of eggs," said Brinkmann.

The toxic metals in their ovaries were in relatively high concentrations, researcher said. These then transfer into the eggs, potentially impairing the survival and health of the young eel larvae and their ability to complete the long journey to home.

European eels were once an abundant source of food in Europe, and later a delicacy that was exported to many places, mostly Asia.

However, their population has declined sharply and European eels are now listed as critically endangered on the red list of the International Union for Conservation of Nature.

Since the 1980s, the number of eel larvae returning to Europe from their spawning grounds in the Sargasso Sea, has declined by over 90 per cent.