BOSPHORUS - Despondent Sunday anglers watch crestfallen as a trawler winches an enormous net out of the waters of the Bosphorus.
"Clear off!" they shout from the shore, impatient to get their hooks back into the depths of the strait that runs through Istanbul.
"I have been here since 6am but a trawler came and dropped its nets. That blocked us completely," grumbled Mehmet Dogan, fed up at only having caught 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.
Anglers like Dogan who cram shoulder to shoulder along the banks say the nets leave them with little chance -- and the fish with even less.
Fish stocks in the Bosphorus have plummeted, according to Saadet Karakulak of Istanbul University. In the space of a few years, hauls have fallen from 500,000 to 600,000 tonnes a year to 328,000 tonnes, she said, saying it is "proof that stocks are diminishing".
"Because of these boats, the fish can't enter the Bosphorus," rued angler Murat Ayhanoglu, standing at Kirecburnu cove on the European side. "They can't leave their eggs here."
- 'Race to overfish' -
But the dramatic fall in stocks didn't stop the government trying to close the strait to traffic for half a day this month to give free rein to commercial fishing boats.
The transport ministry later backed down after protests from scientists and campaigners about the "race to overfish" what they term is a biologically important "corridor".
Plastic waste, pollution and heavy maritime traffic are also blighting fish stocks in one of the world's business shipping lanes, warned Ozturk, who is also director of the Turkish Marine Research Foundation.
From container ships to tankers to bulk carriers transporting badly needed Ukrainian cereals to world markets, more than 200 ships a day pass through the Bosphorus.
With the strait only 760 metres wide at its narrowest point, Ozturk said fish stocks need to be managed by the region's nations.