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TOKYO: Eels were once so common they were considered a pest, but today the ancient creature is threatened by human activity and about to disappear entirely, scientists and environmentalists warn.

Eels are found in human mythology and ancient art, and their bones have been found in graves thousands of years old.
Thirty years ago they were so widespread that they were even considered a nuisance in France, as they were accused of damaging salmon stocks and destroying fishing lines.
“When I was young, eels were found in all rivers and estuaries,” says French researcher Eric Feunteun, a leading expert on the creature.
“My grandmother had a coffee shop … and sometimes lucky customers would bring a bucket of young eel to pay for their coffee,” he said.
In less than half a century the situation has changed radically: the European eel population is now only 10 percent of the level in the 1960s-70s.
“We sounded the alarm in the 1980s,” said Feunteun, professor of marine ecology at the French National Museum of Natural History, but it wasn’t until 2007 that the European Union asked its members to protect the species.
The European eel is now on the Endangered List of the International Union for Conservation of Nature, with its Japanese and American cousins ​​just one category behind on the Endangered Species list.

This October 25, 2021 image shows an eel in a tank for the Japan Fisheries Research and Education Agency in the suburbs of Minamiizu, Shizuoka Prefecture. (AFP)

The eel’s complex life cycle makes it prone to a wide variety of human activities, including overfishing of a species that is a popular delicacy in Asia.
But these pressures are far from the only reason the eels are declining.
“We have known since the 1980s that there are multiple reasons and that fishing is probably not the main factor,” Feunteun said.
He points out that water pollution with pollutants such as pesticides, medicines and plasticizers has a much greater impact, including on eel reproductive capabilities.
Habitat destruction also plays an important role, according to Andrew Kerr, President of the Sustainable Eel Group.
He points to the “drainage of three-quarters of Europe’s wetlands. And then the over a million barriers to fish migration in the rivers, like dams. “
“So we basically destroyed the eel habitat. And that really killed it, ”he told AFP.
Climate change is also a factor that shifts ocean currents that bring eels from their spawning grounds in tropical waters to the rivers and estuaries where they will spend most of their lives.
Longer and slower routes mean higher juvenile eel death rates as they drift towards coastlines.

Japan, China, Taiwan and South Korea have been cooperating since 2012 in protecting the Japanese eel found in their waters, including when it comes to catch quotas.
But the catch limits alone are not enough, say experts.
Other efforts include programs ranging from helping eels to migration barriers to moving young eels from areas where they are abundant to places where they are declining.
Elsewhere, dams that can catch, injure and kill eels as they migrate have been adjusted, and systems have also been put in place to track them down and disrupt trade.
However, experts say more is needed, including to protect habitats.
“It won’t be long before the other 16 eel species get on the critically endangered list. So we need to have a global approach to eel conservation, ”said Kerr.

The eel has been shown to be resistant to natural reproduction in captivity and artificial insemination is possible but expensive.
“The rate of reproduction is low and it takes a long time for the (juvenile) glass eels to grow,” said Ryusuke Sudo of the Japan Fisheries Research and Education Agency in the Izu region, southwest of Tokyo.
Scientists have also never observed eel larvae feeding in the wild, so their preferred diet remains a mystery. They grow more slowly in captivity and each eel requires individual human intervention to reproduce.

It is believed that eels have existed for 60-70 million years and have not diversified very much with only 19 species and subspecies of the Anguilla genus.
Despite their longevity, much about them remains a mystery, as scientists have only recently located the first spawning grounds.
In a way, eels are “super-adapted,” Feunteun said. They are able to breed in areas where most fish could not find food, as eel pups can feed on “sea snow”, dead and decaying plant and animal matter that drifts down the water column.
But the long distances they wander and disperse make them vulnerable.
“70 million years of existence and 40 years of decline,” as Feunteun puts it.
Nevertheless, he makes himself hopeful.
“It’s a species that has shown during previous climatic changes that very few individuals can recover,” he said.

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