"I have been here since 6am but a trawler came and dropped its nets. That blocked us completely," said Mehmet Dogan, fed up at having caught only one fish all day, a 40cm bonito.

It is high season for the popular variety of tuna, with shoals teeming through the Bosphorus on their way from the Black Sea to the Mediterranean.

But pulled taut across the strait are fishing nets more than a kilometre long.