Eel migration study tells 'romantic' tale

By Helen Briggs BBC News

5 October 2016

Scientists are a step closer to solving the mystery of one of the great animal migrations.

Each autumn, eels leave European rivers to travel across the Atlantic Ocean to breed for a single time, then die.

Tagging studies show that the fish swim more than 3,000 miles (4,800 km) to the Sargasso Sea.

But, rather than one mass spawning in the spring - an idea held for a century - their arrival is staggered, UK researchers say.

"Eel migration is a rather romantic tale," said lead researcher David Righton, head of the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) in Lowestoft.

"Eels only spawn once in their lifetime and then they die, so they're making this final journey of their life, towards the Sargasso Sea, to meet their life's goals, if you like.

"And so the fact that we've got a little bit of insight into that - but we've also got some new questions about how eels tackle that really fundamental problem of meeting that life goal - is really, really fascinating."

Mysterious life cycle

The life cycle of the eel has long puzzled scientists.

Even the Greek philosopher Aristotle pondered the question of where eels came from, deciding that they sprang up spontaneously from the mud.

Almost 100 years ago, it was discovered that their destination was the Sargasso Sea, in the western Atlantic near the Bahamas.

This led to the assumption that all eels took the shortest and quickest route across the ocean from freshwater rivers and streams.

"What we've found is that [some] eels actually take a more convoluted route to the Sargasso Sea," said Dr Righton.

"We propose that eels probably have a strategy that enables some eels to arrive in a very short period of time but others to take a longer, more meandering journey and perhaps arrive up to a year later and spawn in the subsequent seasons."

Eels arrive around the European coast as tiny glass eels, having drifted across the Atlantic for two or three years from the Sargasso Sea.

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Conservationist's claims that European eels are 'critically endangered' challenged by trader

The conservation body that assesses the level of threat to animal species has been reported to the Advertising Standards Agency (ASA) by a company that sells eels – for describing the fish as "critically endangered".

The classification, by the International Union for Conservation of Nature (IUCN), suggests the European eel is at greater risk of extinction than giant pandas, blue whales and mountain gorillas, all considered to be merely "endangered".

Peter Wood, who owns the Gloucester-based UK Glass Eels, which sells eels as food, said that since the designation in 2010 the European market for eels had shrunk by 50 per cent.

"There's a lot at stake," he said. "The eel classification is damaging. It's not a balanced view and it's not evidence-based. The giant panda is 'endangered', but it's at far greater risk than the eel – there are only 2,000 of them left. For the eel, we are talking about a population of hundreds of thousands of millions."

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Whales Gobble Up Endangered European Eels

By Megan Gannon, News Editor | February 10, 2014 01:51pm ET

Rare European eels are thought to cross the Atlantic Ocean to breed, but not all of them finish the ambitious voyage. Some meet their end in the bellies of deep-diving whales, new research reveals.

Not only does the finding underscore the risks European eels face during their epic migration, but it also shows that whales may have a previously unknown appetite for eels.

Considered critically endangered, European eels (Anguilla anguilla) are found in increasingly small numbers in rivers, lakes and brackish waters across the continent from the Mediterranean to Scandinavia. Scientists think the fish travel thousands of miles each year to get to the Sargasso Sea, a calm expanse in the middle of the North Atlantic that is warmer, saltier, bluer and clearer than the surrounding waters. 

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Mysterious Eels' Mating Migration Tracked

Rare European eels from the Mediterranean to Scandinavia make an epic journey when it's time to mate. They leave rivers and brackish habitats, swimming hundreds of miles across the Atlantic to the Sargasso Sea, an open ocean region that is warmer, saltier, bluer and clearer than the surrounding waters.

This trek had remained a mystery to science since no eggs or adult eels have ever been caught in the Sargasso Sea. But researchers recently attached satellite tags to about 600 eels from different places in Europe and were finally able to map the route of the spawning fish.

"We could track the satellite tags as far away as the Azores. This suggests that the eels take a different route to the Sargasso Sea than previously thought. It seems as if they’re saving energy by hitching a ride on the Azores Current," researcher Kim Aarestrup, of the Technical University of Denmark, told youris.com.

Continued:  http://www.livescience.com/26201-mysterious-eels-mating-migration-tracked.html