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Grote Eikapseljacht: an update!

Several species: spotted, thornback, smallspotted catshark!

It has been three years since the start of De Grote Eikapseljacht.

More than 1000 eggcases are registered now! There is a small increase in the number of undulate rays, spotted rays and blonde ray, but when checking entries, we have also noticed that at least  10 percent is wrongly determined: it is often assumed that it is a blonde ray eggcase, because the whole egg capsule is measured, and not just the capsule, but also the tendrils.
With catshark eggcase, many people think the colour makes the difference, but it is actually the size and the thick ridges that are different between the two catshark species.
And when an eggcase is not soaked, the measurements can differ… sometimes, the difference in length can be 3 centimeters. Registrations without photographs are processed, but not as ‘determined’.

Smallspotted catshark eggcases

A website with results has been on the website for a long time:

Several species: smallspotted catshark, spotted, thornback…

Furthermore, we are still working on examing eggcases. This work is done by interns at the hatchery Blue Linked ( and… one eggcase at the time. We have decided two focus on two species: the thornback ray (Raja clavata) and the smallspotted catshark (Scyliorhinus canicula. For each species, we need 200 to 400 eggcases.

When those are all examined,  the results will be collected and evaluated by Michael Laterveer of Blue Linked and two marine biologists.


Undtulate ray and thornback ray case



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