"We are starting it as an experiment, but we believe this could be the solution we have been looking for," said Moulvi Manzoor, deputy director of Jammu and Kashmir state's fisheries department.

A small number of the Chinese fish, which only eat water plants, had been released in pens at a few places in the lake in tests, he said.

The grass carp is a voracious herbivore and an adult fish can grow up to 30 kg (66 lb).

"It will be able to control the growth of weeds, but the plants won't completely vanish from the whole lake," Manzoor said.

The lake, which once covered 30 square km (12 sq miles), has shrunk to half that size over the past four decades because of silt, weeds and development.

Many areas on the periphery have been reclaimed and converted into floating gardens.

The lake is in the heart of Kashmir's summer capital, Srinagar, and has more than 1,500 timber houseboats that are popular with tourists, who also take trips in smaller boats.

Disputed Kashmir, with its meadows, pine forests and snow-capped peaks, was one of Asia's main tourist attractions before a revolt broke out in 1989. Tens of thousands of Muslim separatist rebels, troops and civilians have been killed.

Despite the violence, thousands have travelled to Kashmir this year as regional peace moves have gathered pace and Dal Lake is always a popular destination.

BREAD AND BUTTER

"The lake is like our mother, it gives us bread and butter, we survive on this. I wish and pray the lake gets healthier, cleaner ... that will attract more tourists," said houseboat owner Mohammad Ramzan, 55.

Weeds have flourished in the lake because of the large amounts of waste flowing into it.

Civic authorities say they will build six sewage treatment plants around the lake to stop the waste being discharged from the houseboats, hotels and houses on its banks.

Houseboats will be equipped with sewage tanks and the owners have been warned against discharging waste into the lake, an urban development official said.

Each year, civic authorities remove more than 6,500 metric tonnes of weeds using floating de-weeding machines. Labourers also manually remove the plant menance from the lake.

Manzoor said the UN Food and Agriculture Organisation had identified the grass carp for biological weed control and it had been successfully used in the United States and Europe.

The fisheries department has imported more than 10,000 fish from China and also set up a breeding centre in Kashmir.

But one expert said the fish would affect the lake's ecosystem and might not be able to attack all of the 25 different kinds of weeds that thrive in the polluted lake.