A fisherman prepares fishing net on his boat before going out to fish close to the shore of the Shkodra's lake.

Weary after a day's work on the water, Albanian fisherman Ilir Neziri peers down with disappointment at his small haul of carp from Shkodra, the largest lake in southern Europe.

"Big ones are becoming rarer and rarer," sighs the 47-year-old as his small dinghy powered by an old engine glides across Shkodra.

Overfishing and poaching are to blame, according to Albanian fishermen and experts who have sounded the alarm over threats to the glistening body of water that straddles Albania and Montenegro.

A jewel of the Balkan region, the lake spans up to 530 square kilometres (205 square miles), two thirds of which lie in Montenegrin territory, where it is called Lake Skadar.

A fisherman prepares fishing net on his boat before going out to fish close to the shore of the Shkodra's lake.

The waters are renowned for their rich biodiversity but fish stocks have been shrinking, Albanians say, threatening the ecosystem and the livelihood of hundreds of fishermen.

Neziri, who uses fishing rods, blames "illegal" electrofishing for his small catch of 10 kilogrammes (22 pounds), which earns him around 28 euros ($30) at the market.

Poachers are using electrofishing in "both Albania and Montenegro to the detriment of honest fishermen," he says.

Bleak picture

But poachers remain undeterred, according to locals.

"All you have to do is come at night to see that the electric fishing continues," said Rasim Taraboshi, a 75-year-old Albanian fisherman who returned empty-handed after an entire night out on the lake.

He explains how poachers stun the fish to death using electric currents that flow underwater through electrodes that are connected to generators or batteries.

The fish are then scooped up after they float to the surface.

A jewel of the Balkan region, the lake spans up to 530 square kilometres (330 miles).

There are no reliable statistics on fish stocks but scientists paint a bleak picture.

"Today, we are confronted with the fact that the quantities of fish in Shkodra Lake are considerably reduced," says Djana Bejko, an Albanian professor of biology.

The sturgeon disappeared from Shkodra 30 years ago and the European eel and the bleak are facing a similar fate.

Wastewater discharge

Experts also warn pollution could soon pose a new threat to the lake's ecosystem, with contamination spilling in from chaotic urbanisation and wastewater discharge near the lake's shores.

On the Montenegrin side, the lake is fed by the Moraca River and its tributaries, which carry the wastewater of some 300,000 inhabitants half the population of the small Balkan country.

Fisherman Ilir Neziri stands next his boat close to the shore of the Shkodra's lake.

Currently, the lake is able to "successfully combat pollution thanks to lush vegetation," said Montenegrin environmental specialist Darko Saveljic.

"The question is, until when?"

Albanians say they have also seen heavy rain sweep pollutants into the lake from their side.

"Bad weather makes the lake overflow and carries in garbage and debris such as plastics," says Idriz Kurtelaj, a former fisherman and environmental expert in Albania.

Specialists on both sides of the border agree on the need for the two countries to coordinate.

However, one point of contention is the use of wooden and metal traps known as "daljani" fish weirs set up at the mouth of the lake. They allowed in Albania but banned in Montenegro, which says they deplete stocks.

Agence France-Presse