Science Interviews


Thu, 9th Sep 2010

The Great Egg Case Hunt

John Richardson, The Shark Trust, and Sonia Revelley, Natural England

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Also known as "Mermaid's purses", the empty egg cases of skates and rays wash up on beaches all around the world, leaving a useful calling card to help track down these threatened relatives of sharks.

The Great Egg Case hunt is a project pioneered by The Shark Trust, with individual hunts run by various other conservation groups around the UK.

We join a Great Egg Case Hunt at Hunstanton Beach on the north Norfolk coast organised by Natural England and Borough Council of King's Lynn and West Norfolk. Sonia Revelley from Natural England introduces us to the beachside hunt, while John Richardson from The Shark Trust tells us more about the science and conservation messages behind the project.

Skate egg case


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The Great Egg Case Hunt

The Shark Trust

Natural England

Helen – Sonia, tell us, what are we looking for today?

Sonia – Today we’re going to go down to the beach and we’re going to look for mermaids’ purses. They resemble big black giant ravioli cases and basically they are the egg cases of skates found living in UK waters. So, that’s what we’re doing today.

Helen – And we just look around on the beach. Is there anywhere that’s particularly good to look for these things?

Sonia – Best place to look for egg cases is basically on the strand line, the highest point where the tide deposits all the seaweed and debris from the ocean. Against the base of the cliff at Hunstanton and against the base of the sea wall.

Helen – That sounds fantastic. Let’s go see what we can find.

Have you guys found anything? What have you got?

That definitely looks like an egg case to me. Where did you find it? At the top of the beach?

Egg case hunter – Yes, at the top, near the wall.

Egg case hunter 2 – And I found lots of mussels for tea tonight.

Helen – Excellent. So you’ve got your dinner as well. Are they easy to find, the egg cases?

Egg case hunter 2 – Noooo.

Helen – Where’s the best place to look for them, do you think?

Egg case hunter 2 – Near the edge, in the sea weed. 

Helen – In the sea weed? Excellent, because I haven’t found any yet. I’m not very good at this.

Oh my goodness. Look at this! There’s a whole box full of them! Who found them? Did you find these?

Egg case hunter 3 – I found a fossil.

Helen – And a fossil. This is fantastic. What a great trove, a great treasure trove. You must have, there must be about thirty in there. Keep up the good work. 

So, has today been a success? Did you find what you were looking for Sonia?

Sonia – Yes, today has definitely been a success. We’ve had quite a few mermaids’ purses brought back. With two separate families we’ve managed to identify.  One definitely spotted ray mermaids’ purse, and one definite thornback ray mermaid’s purse. 

We’re very happy. I’ve now got to go back home and try and identify all the others and then send them back to the shark trust. But no, it’s been a very successful day. 


John – The prime reason behind it is to really raise the profile of skates and rays in the UK. For adults of a lot of the marine species they do have issues facing them in terms of conservation, they probably get the least press of all. People know very little about them. And is a great chance for the shark trust and everyone who takes part in it to raise their profile in the public eye, get people thinking about them and the issues facing them. 

Helen – What kind of issues are these species facing?

John – Overfishing tends to be the problem. They don’t have a very high reproductive rate and when you get bottom trawlers and other commercial fishing operations in the area, if we’re not careful and don’t have a sufficient amount of research on these populations it would be very easy to wipe out regional populations or to make a real dint in their numbers to the point where they struggle to reproduce.

Helen – What are you finding with this data, and how do you hope ideally this will actually help to protect these species?

John – We’re still piecing it together. We do have over 17,000 individual records so we have a lot of data. We’re still working with government organisations such as Cefas, which is more of a fisheries science group. Where we identify areas where skates and rays are perhaps breeding, where there are nursery areas that are really important to future populations of these species, once we’ve identified these perhaps we can look at getting some protection in there, perhaps from fishing, from recreational angling. We can stop, well, we can try and stop aggregate mining and dumping of dredge spoil, all these things that really do have impacts on skate and ray populations. 

Helen – And this isn’t just in the UK is it? You’re collecting egg case sightings from other countries too. Can we find these egg cases all over the world?

John – Absolutely. I think, off the top of my head, there is about 600 species of skate and ray throughout the world. So there’s egg cases washing up all over the place. We get a few. We’ve had egg cases from Angola, South Africa, France, Ireland, even Argentina, the US. So there’s egg cases out there everywhere it’s just a matter of getting your eye in and looking for them.

Helen – You’re also asking people to report sightings of egg case not just from the coast but also in the underwater realm. How are scuba divers helping to build a picture of these species?

John – They are kind of the next step in the Great Egg Case Hunt. Beach hunts are always going to be important. But again, we’re really looking to verify what we’re finding and when they’re down if divers see egg cases, live egg cases, which are what we call in situ, when they’re actually attached to the sea floor with a juvenile skate or ray in them then we know for a fact that could well be a nursery ground, an egg laying ground, a really, really important area to protect for these species. 


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