Ken Whelan

At the end of the day, their ability to be able to use the magnetic fields, we think, when they're in the open ocean.

But this ability to smell or taste what they're doing is amazing.

That makes most sense to me.

So it's what I call the Swiss roll effect.

And I imagine, I assume, that inside those mermaids' purses, as the development happens...

So when they're in fresh water, let's imagine you have a little salmon at the top of the Liffey here in Dublin.

There is the actual facility and indeed the units that will actually feed those creatures.

When that salmon gets uncomfortable and starts to move down, genetically, it imprints then the taste or smell of the spot it has been spawned.

But the interesting thing about the sharks and the rays is the fact that they have so many different ways of actually reproducing.

And as it comes down, it imprints then the other smells in sequence.

So most of the bigger sharks reproduce young.

And it unrolls the Swiss roll when it comes back into the estuary and follows that trail of smell the whole way back up to where it spawns.

live young.

And I think we've all probably seen photographs of this lovely underwater shots of the baby sharks coming out and immediately starting to feed.

But then they have a lovely intermediate stage.

So laying them is called viviparous.

And then you have ovoviviparous.

And ovoviviparous, basically the egg actually stays inside the female and then it hatches inside the female.

Yeah, it could very well, particularly that whole situation in terms of pollution.

And it seems as if the young are coming out of the female.