We've all probably been through a breakup, Mike accepted.

Thank you.

Been married to the same person forever.

I love you, baby.

We've all at least had a friend go through a difficult breakup,

and one thing you say to them is, you know know there are plenty of fish in the sea.

But wouldn't it be more comforting if you could be more accurate?

Exactly accurate.

Tom Webb is a Royal Society University Research Fellow at the University of Sheffield and he studies marine biodiversity.

So Tom, exactly how many fish are there in the sea?

Okay, if I had to put a number on it, I've been doing some back of the envelope calculations

based on some really good recent studies and I think we're into the quadrillions so a quadrillion is one

followed by 15 zeros. So I guess I mean that you know we use that phrase to comfort someone who's just

just just been dumped that is a very comforting number. It is there's a lot of fish in the sea. Most of them are fish that we're not particularly

interested in though. So I've pulled that number from a study which was looking at what we call mezzo pelagic fish. So these are fish that live in the open

ocean. They live usually between about 200 and a thousand meters depth and they're pretty small but these really dominate the

biomass of fish in the world and they are probably well almost certainly the most

abundant vertebrates on Earth as well.

So I guess as far as the metaphor is concerned these are sort of the the undatable fish.

Yeah, yeah. So I can give you an estimate for the good catches as well.

So if you want to know about fish, which are sort of in the range of sizes of things that we might like to see on our plate.

So 10 grams to 100 kilogram range and these are all of the familiar, the familiar fish

...