After half a century of fishing, 65-year-old Fuat, a retired Turkish civil servant, is nostalgic for the good old days when the Bosphorus Strait in Istanbul teemed with fish.

Wearing a black woolly hat, Fuat is one of hundreds of amateur anglers passing their spare time on the Galata Bridge on the European side of Istanbul, trying to fill their buckets.

"I've been fishing since I was 15 years old," he told AFP as he cast his line over the waters at the confluence of the Bosphorus with the Golden Horn, overlooked by the Hagia Sophia and Blue Mosque.

"In the past, there were many fish, the human population was lower," he said.

"Those fish are gone now. Those beautiful fish are gone because of the increasing population and careless fishing."

- Traditions preserved -

The sight of thousands of amateur anglers crammed shoulder-to-shoulder on the Galata Bridge and on the banks of the Bosphorus all the way from the Marmara to the Black Sea is, for many, one of the iconic images of Istanbul.

The Bosphorus' position connecting the Mediterranean to the Black Sea system makes it a hub for fish and, according to the time of year, can be crammed with prized delicacies like lufer (bluefish), levrek (bass) and palamut (bonito).

Many anglers come for the day and night, lighting fires and bringing samovars for making tea. Small stallholders sell bait, hooks and flies.

While Istanbul is changing at breakneck speed with unimpeded developments, the scenes of fishing are hardly different from those taken in grainy black-and-white pictures from the 1950s.

But the bucolic images hide an uncomfortable truth, experts say. Fish stocks in the Bosphorus have plummeted and this is in no small measure due to the indiscriminate fishing of the hobby anglers.

The careless bycatch of fish species and keeping juvenile fish after they are caught -- officially illegal -- have put the Bosphorus ecosystem in a perilous condition.

- 'Not legal'-

Erol Orkcu, head of the amateur and sports fishing association in Istanbul, said there has been a significant increase in the number of amateur fishermen compared to the past as the city's population boomed.

Fish stocks have decreased by around 50 percent compared to the 1980s and 90s, he said.

"Things are deteriorating. The fish population is in decline. Marine conservation is needed," he told AFP.

Pollution and destructive fishing practices are among the major factors behind the reduction in fish stocks.

"90 percent of the fish caught on the Galata Bridge are juveniles, unfortunately. That is not legal," he said.

Tomris Deniz, associate professor at Istanbul University faculty of fisheries, described the blatant overfishing -- without any genuine attempt at inspection -- as alarming.

"Could you imagine the stocks if, let's say, 100,000 fishermen each catch one kilogramme in the Bosphorus during the migration period?" she asked, emphasising there was no sound data on Turkey's fish reserves.

And while the anglers on the Galata Bridge look like amateurs, many are selling the fish caught in the Bosphorus illegally, pushed by the troubles of the economy and the double-digit unemployment rate.

A study carried out by Deniz's department showed 16 percent of the anglers on the bridge are not true amateurs but are actually selling the fish they catch.

"There is a lack of inspection in big cities. There is no official recording," she said.

"Fishing is apparently becoming a source of income for the unemployed, given the economic circumstances."

- 'Therapy'-

But the anglers -- mainly men but also some women -- see themselves as the proud hallmark of Istanbul.

Serife Dogan, 56, wearing a headscarf and sunglasses, is trying to catch fish with some help from fellow fishermen.

She said she was diabetic and started fishing only two months ago as a hobby on her doctor's advice.

"I am very much an amateur. Men are showing me how to cast a line or how to remove the fish from the hook," she said, while learning some tricks to catch fish from a fisherman at Karakoy near Galata Bridge.

"I lose track of time here."

"I come in the morning and stay up to seven hours... It's just like therapy. But of course, when I get back home, my head gets full again," she said.

Dogan said she had enjoyed beginner's luck.

"They say it's sheer luck. I am catching nearly half a kilogramme of fish. I take them home, sharing with family and friends," she said.

- 'Juvenile fish'-

But back on Galata Bridge, Fuat fumes over the unchecked fishing in the Bosphorus.

"They are catching all the juvenile schools of fish, causing their extinction," he claimed.

"In the past, I used to catch 8-9 kilogrammes of bonito and bluefish the size of my leg," he said.

But he still keeps coming on to Galata, spending up to 10 hours a day.

"Instead of playing backgammon in a coffee house, I catch enough fish to feed my family," he said.

"And if it is more than enough, I sell it," he added, filling one bucket with fish he caught for a "special customer".