mystery eggs

I saw a couple of these egg clusters some time ago and asked my friends at the British Marine Life Study Society Facebook page what they could be. Unfortunately I have not had any suggestions yet. Do you know who laid these eggs?

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Aha, Bert Roos from the Dutch ‘Noordzee en Koud Zeewater Forum’ reckons these are eggs laid by the Long-spined Bullhead Taurulus bubalis!