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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