Eels were once so abundant they were considered a pest, but today the ancient creature is threatened by human activity and is in danger of disappearing altogether, scientists and environmentalists warn.
How have eel populations changed?
Eels appear in human mythology and ancient art, and their bones have been found in graves dating back thousands of years.
Barely thirty years ago, they were so frequent that in France they were even classified as nuisance, accused of damaging salmon stocks and destroying fishing lines.
“When I was young, eels were in every river and estuary,” said French researcher Eric Feunteun, a leading expert on the creature.
“My grandmother had a coffee… and sometimes the unlucky customers would bring a bucket of young eels to pay for their coffee,” he said.
In less than half a century, the situation has radically changed: the European eel population has only reached 10% of its level in the 1960s and 1970s.
“We sounded the alarm in the 1980s”, explained Feunteun, professor of marine ecology at the National Museum of Natural History in France, but it was not until 2007 that the European Union asked its members to protect the species.
The European eel is now on the International Union for the Conservation of Nature’s critically endangered species list, with its Japanese and American cousins just behind a category, on the endangered species list.
What threatens eel populations?
The eel’s complex life cycle makes it vulnerable to a wide range of human activities, including overfishing of a species that is a popular delicacy in Asia.
But this pressure is far from being the only cause of the eel’s decline.
“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 the pollution of waterways with contaminants like pesticides, drugs and plasticizers has a much greater effect, including on the reproductive capacity of eels.
Habitat destruction also plays an important role, according to Andrew Kerr, chairman of the Sustainable Eel Group.
He points to the “drainage of three quarters of Europe’s wetlands. And then more than a million obstacles to the migration of fish in rivers, such as dams ”.
“So we basically destroyed the habitat of the eel. And that’s what really killed it,” he told AFP.
Climate change is also a factor, shifting ocean currents that carry eels from their spawning grounds in tropical waters to rivers and estuaries where they will spend most of their lives.
Longer, slower routes mean higher death rates for young eels as they drift toward the coast.
How are eels protected?
Since 2012, Japan, China, Taiwan and South Korea have cooperated in the conservation of the Japanese eel found in their waters, including with fishing quotas.
But fishing limits alone are insufficient, experts say.
Other efforts include programs that range from helping eels overcome migratory barriers, to moving young eels from areas where they are abundant to places where they are in decline.
Elsewhere, roadblocks that can trap, injure and kill eels as they migrate have been adapted, and systems to trace them and stop traffic have also been put in place.
However, more is needed, experts say, including habitat protection.
“It won’t be long before the other 16 eel species are on the endangered list. So we need to take a holistic approach to protect the eel, ”Kerr said.
What about artificial reproduction?
The eel has been shown to be resistant to natural reproduction in captivity and artificial fertilization is possible but expensive.
“The reproduction rate is low and it takes a long time for the elvers (juveniles) to develop,” said Ryusuke Sudo of the Japan Fisheries Research and Education Agency in the Izu region, in southwest of Tokyo.
Scientists have also never observed eel larvae eating in the wild, so their favorite food remains a mystery. They grow more slowly in captivity, and each eel requires individual human intervention to reproduce.
Could the eel disappear?
Eels are believed to have existed for 60 to 70 million years and have not diversified much, with only 19 species and subspecies in the genus Anguilla.
Despite their longevity, much about them remains a mystery, as scientists have only recently located the first spawning grounds.
In some ways, eels are “super-adapted,” Feunteun said. They are able to reproduce in areas where most fish cannot find food, as young eels can feed on “sea snow”, dead and decaying plant and animal material that drift in the water column. .
But the long distances over which they migrate and disperse make them vulnerable.
“Seventy million years of existence and 40 years of decline”, as Feunteun puts it.
However, he keeps a little hope.
“This is a species that has shown in previous climate changes that it can bounce back from very few individuals,” he said.