Technically ear sand of the fish, these small stones are being sold separately from the fish, priced at four to 10 liras each.

"A fish that gets sold for 70 liras per kilo can have two stones," vendor İlker Keklik said. "The price of the stone varies from 600 to a thousand liras."

The stones are also thought to prevent kidney disease, which prompts customers to get them from the fish even if they have the vendors clean it out, Keklik added. 

The size of a fingernail, these stones are comprised of calcium carbonate, Akdeniz University expert Prof. Mehmet Gökoğlu said.