A first class IDing guide for mermaid's purses compiled by the 'Sharks Trust' is supplied below by Graham (Gramandy).
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With so many Raja species to pick from I thought it might be difficult to bring to species? Can you give any more info on why this is clavata and not one of the many others? Eg Blonde or Painted. It'd be good if there was a chart of IDed purses!
To ID properly you need to rehydrate in water - however, I think you'll see there is enough evidence to point to Thornback.
Painted/undulate - unequal length of horns at same end - much browner in colour (ok admit this is old specimen), no apparent extra appendage marks along edges of eggcase. Horns usually splay outwards.
Blonde - completely different as is keeled around all edges of the eggcase. Equal sized horns at either end and a larger egg capsule (9cm) area.
Cuckoo - horns curve inwards
Spotted - eggcase too big for this sp.
Here is your eggcase ID chart that you wanted :-
Thanks for the link, thats the ticket. What exactly do you mean by extra appendages along the edges? I pulled quite a few wispy bits of stuff from this case to make it look tidier, I didnt realise I was making an IDing mistake. It had tough feathery growths all along its edges in which small stones and bits of sea weed were trapped. I thought it would look better without its messy adornments. Shouldve took one before I trimmed it!!
...the adornments are how the eggcase attaches to kelp/stones/other algae. However, looking closely it doesn't look like you've removed anything other than the attachment filaments. Check out the extra bits on painted and I'm sure you weren't that vicious to have removed these and not leave some sort of evidence behind. Horns are still not right for painted.
Yip they were only attachment filaments similar to those you pull from a mussel, anchoring fibres.
Thanks for sharing that first class ID guide. The very first case used in the guide is -I believe, exactly the same as mine. The others shown all do differ enough to be almost unconfusable.
I think you are absolutely right and this is Raja clavata. I didnt think such a good ID guide would be available. I have found a fair number of this particular case in the past and always just thought -yes a ray but it could be any one of a large number.
Thanks for this.
...helps for next time - I guess if you're really keen - you can help the shark trust by sending in IDed eggcases from your area. Fun to rehydrate while you're fishing and nothing else is happening. A bit of water and heyho you can ID them all.
It will certainly help Graham, it is excellent. I noticed on the guide that Cuckoo Ray are considered a deep water fish and their cases are rarely found. This last few summers they have been appearing in shore anglers catches close to here in water that is no more than 20 foot deep. I hope to find one of those.
Lat/Lng: 55.088, -6.0506
OS grid ref: NW416845