Arjan Palstra

Well, no, not that close.

Well, for European eel, I don't know exactly.

For Japanese eel, they're like around 150 meters of depth.

So that's still quite deep.

And the eels are supposed to spawn even deeper, maybe about 300 meters deep.

Well, everything that happens on the continent, we know a lot about it.

But what I say, the moment that they disappear into the ocean, and like almost a year later, we get small transparent eels back, that was always a black box.

So eels are born in the Sargasso Sea.

These larvae, they turn into willow leaf-shaped larvae, leptosafely larvae.

They're about just a few centimeters.

And by the currents, they're taken to the European continent.

There they metamorphose into tiny transparent glaciers, and they swim up the rivers.

Actually, the moment that they swim into the freshwater, then they start to pigment.

Wow.

And then they spend a long life basically growing.

Yeah, there is a big difference between the sexes.

I mean, when the densities are high, many fish become males and they're quite small.

They only have to produce sperm and make sure that diversity is maintained.

The females, that's a different story.

When the densities are low, so mostly in upstream areas, you get more females.