Shark Eggcases Survey Results for 11 March 2022

thornback rays egg cases

What a Wet Day!  After the last two beautiful days, and despite the misty murky rain, we were determined to complete another day of Shark Eggcase Surveying of Area 2: Small Hope Beach to Tradewinds Cafe – Shanklin.  Plus, we thought, would a wet day make a difference to the number of Mermaid’s Purses we found? 

Friday 11 Mar 2022 was cold, wet and a low thick sea mist filled the air so it was impossible to see Culver Cliffs and Luccumbe Cliffs (which are at either end of Sandown Bay, Isle of Wight), from Small Hope Beach. The survey times were aimed for the low tide, to enable a full survey of each beach section before the tide headed back in. When at last the rain stopped, the sun came out but the sea mist continued to hang in the air, refracting the light into a beautiful multicoloured sky!   

Interestingly, we found 256 eggcases today even though it was slightly uncomfortable to ‘hunt for the Mermaid’s Purses’ so this would usually make you less observant. Because of the wet weather and the short tide time, we tried to conduct the survey quickly, due to being ‘wet’ and in order to get into the next survey section as the tide in Small Hope Beach sections appeared to be very fast coming back in…and yet this day’s hunt gathered the most ‘daily eggcase total’ found in one go for the whole of March 2022’s Survey! 

So… was the Weather a factor in this?  The waves were rolling in fast and relatively high, as the groynes and sea wall are strictly regimented and ‘funnel’ the waves, making them swirl into the corners of the sea wall where the groynes attach.  The action of the sea waves being funneled into the sea wall groyne corners was mesmerising, when suddenly we witnessed an amazing natural spectacle!

On top of the funneled swirling white foam waves, which were like a conveyor belt, came a Convoy of Surfing Mermaid’s Purses right before our eyes.  We were actually witnessing the delivery of Mermaid’s Purses to the Sea Shore in Real Time…fabulous!  In excitement, we began plucking fresh plump Mermaid’s Purses directly from the conveyor belt of funneled wavelets.

Is this a good way to survey?  Should we wait until the Mermaid’s Purses actually become stranded on the sea shore before counting them? ETHICALLY…WERE THERE STILL LIVE SKATE PUPS INSIDE?…No, they were all empty – PHEW!  But it left me wondering, the design of the Mermaid’s Purse is incredible: it’s buoyant even though it is technically empty and sometimes filled with water – so here’s a question for all you Citizen Scientists:

Why do Mermaid’s Purses Float and Surf the Waves?  

Why has nature made the Mermaid’s Purse so buoyant AFTER it has expelled the baby Skate Pup hatchling? 

Or, is the Mermaid’s Purse buoyant with the Skate Pup still in it, as they can take up to 18 months to hatch?

What is the point of this buoyancy, surely the eggcase should be encouraged to stay under the sea, not on top of it?…is it just a coincidence, an unintended consequence OR is there a benefit to a buoyant discarded eggcase? 

Is it a deliberate way to confuse predators who may eat a live pup in its eggcase – perhaps by flooding the sea with empty eggcases, eventually the predators will be ‘trained’ not to bother to eat a live one? 

And, one last one, Why doesn’t the eggcase disintegrate and biodegrade quickly once it is no longer needed…the eggcases are super tough even after the hatchling pup has left…WHY!?

Let me know your thoughts on these Scientific Conundrums!

1 Undulate Skate Eggcase

19 Small Spotted Catsharks

27 Spotted Skate Eggcases


209 Thornback Skate Eggcases!!

Top Tip for Hunting Mermaid’s Purses

How to spot a Surfing Mermaid’s Purse!

Look for ‘Surfing Mermaid’s Purses’ on top of the waves, especially if you can view the sea from a vantage point high above the waves, such as from a boat, an esplanade at high tide, or where groynes meet the sea wall esplanade creating that ‘conveyor belt convoy of Mermaid’s Purses’ mentioned in the Fri 11MAR22 Survey results.  It’s an amazing natural phenomenon to witness, but don’t be tempted to dive in to fish them out if the waves are high or turbulent, just enjoy the spectacle and ponder on why or how they are surfing the waves in the first place!

We’d love to see your Mermaid’s Purses images via Facebook or email for identification and we will add them to our local database and The Sharks Trust global database.

Happy Shark Hunting!


SharkLab Technician


Blue Seas Protection