You'll remember that over half term I took the children to the South Coast to visit their Grandad. Whilst there we enjoyed many beach walks and found plenty of treasures, including lots of eggcases, washed up on the strand line. A few weeks later I took the children to Devon and we found some more.
This week we have been busy recording all of our eggcase finds as part of The Great Eggcase Hunt. The database of eggcase records provides crucial information about the distribution of British sharks, skates and rays along the UK coastline.
An eggcase, or mermaid’s purse, is a tough leathery case that protects the embryo of a shark, skate or ray. Each eggcase contains one embryo which will develop over several months into a miniature version of the adult.
There are over ten species of skate and ray, and only a few species of shark in UK waters that reproduce by laying eggcases on the seabed. Each species’ eggcase is different in shape and size. Eggcases remain safely on the seabed until the juvenile has hatched, and then the empty eggcases often get washed up on beaches and can be found amongst the seaweed in the strandline.
The distribution of different shark, skate and ray species is changing and a number of species are in decline. The Great Eggcase Hunt helps the Shark Trust to identify areas of the coast where eggcases regularly wash up.
Reported findings allow the Trust to identify potential shark, skate and ray nursery grounds, providing valuable data that aids conservation. This process can help with the management of UK sharks, skates and rays, as well as help designate Marine Conservation Zones which should provide protection for some species from particularly damaging human activities. Eggcase records are a crucial element of this conservation work.
We began by preparing our eggcases for identification:
- Fill a waterproof container with fresh water.
- Submerge the eggcase in water.
- Leave for an hour or two. The longer an eggcase has been out of water, the longer it will need to be soaked to fully rehydrate.
- Remove the eggcase from water. Now it’s ready to be identified.
We used the chart below to help us identify the different eggcase species we had.
Identification can be done based on colour, shape, texture, size, whether there are any keels present and the length of the horns.
With all those key methods of identification to work with you'd think it would be easy - far from it! I spent quite some time toiling over various eggsacks that all looked much the same. Jenson was more cut throat and simply laid various different eggcases over the pictures. I quickly adopted his approach.
We submitted all of our recordings online on the Shark Trust website. Along with the online form we also attached photographs of the eggcases against a scale so they will be able to verify our records. I'd love to say that Jenson diligently helped input the data online with me, but his attention span still isn't that long. I did make sure he watched at least one entry so he could understand what I was doing and by means of a substitute, Jenson did leave me with his best friend Bunny for company because, "he wants to learn about things!!"
Selsey Marine Parade Beach
Pagham Harbour Beach
No project of ours would ever be complete without LEGO making some sort of appearance. You'd struggle to imagine how Jenson could even find a way to make it relevant to this topic - but he did!
Towards the end of the session he scuttled off to his bedroom with an eggcase firmly clutched in his hand. A few minutes later he emerged with a LEGO mermaid's purse!!