"Slippery as an eel," they say.
But it’s not just this slimy fish’s body
that’s hard to get a grip on.
Humans have grappled with the mystery
of the eel’s life cycle for centuries.
Every American and European eel’s life
begins and ends in the Sargasso Sea.
Stay tuned as we dive into the mysterious life
of the Atlantic eel.
There are over 800 species
of snake-like eels throughout the world.
But no one has ever seen the American
and European eels spawn.
The American eel lives all along the Atlantic coasts of
North and Central America, from Greenland
down to Trinidad and Tobago.
The Sargasso Sea is the only sea in the world
that has no land boundaries.
A year-long system of ocean currents forms its borders.
All American and European eels will head there
once they reach the last quarter of their lives.
Every eel, no matter which American river
or Italian canal it has been swimming in,
will travel up to 5,500 km (3,418 mi)
to get to the Sargasso Sea and find a mate.
Strangely, you won’t see any sexual organs on this
secretive fish
until it is en route to its mating site.
And that would be why the question of eel's origin has
plagued our finest minds for centuries.
Ancient Egyptians believed
eels manifested when sunlight warmed the Nile.
Aw, that's lovely.
And Aristotle proposed
that they were made spontaneously
from mud and rainwater.
While we now know that eels, like all fish, come from eggs,
scientists still aren’t quite sure
why the Sargasso Sea
is the exclusive spawning site for the entire population
of Atlantic eels.
There seems to be no specific features or climate in this sea
that could explain the eels’ strange draw toward it.
It was 2015 when scientists confirmed
that once the American eels reach the Sargasso Sea,
they mate, spawn
and all the mothers immediately die.
But scientists have never seen an adult eel
in its former freshwater home
after breeding in the Sargasso Sea.
Each eel lays an average of 500,000
to 4 million eggs.
But only some larvae survive the turbulent
ocean-current ride
to Europe and America.
In their new continental homes,
the larvae will feed and grow
until it is time to make their trip back to the Sargasso Sea.
And the cycle of life and death continues.
But what if you trap American eels like other animals
in a zoo or a lab?
Could you watch them mate and spawn?
This is where it gets even crazier.
Eels refuse to breed in captivity.
They don’t mature, or more commonly, slip away.
What sort of mass hypnosis
is driving this bizarre mating exodus?
How do the eels know when and where to go?
First, it is not a synchronized or mass migration at all.
According to one popular theory,
a combination of physical, chemical, geological
or biological signals
triggers each mature eel’s decision
to head to the Sargasso Sea.
And then it’s up to some highly accurate magnetic cues
that each eel follows to end up in the same spawning site.
Still kind of bizarre.
But it’s not all smooth sailing for this mysterious
and intelligent fish.
Climate change is altering ocean currents,
messing up the Atlantic eel's navigation signals.
To make things worse,
overfishing to keep Japanese markets supplied,
dam-building
and pollution have led to a 99% decline
in the American eel population in some areas.
It is now on the list of critically endangered animals.
Spawning in complete secrecy
and reproducing exclusively in the Saragossa Sea
is what some eels do.
And that’s why they’re Crazy Creatures.