Paris authorities have moved tens of thousands of fish to clean up the Canal Saint-Martin, a popular waterway commissioned by Napoleon that attracts hordes of tourists and revellers.

The three-month clean-up has seen the fish -- ranging from catfish to a 16-kilogram (35 pound) carp -- transported to the River Seine as the canal in the trendy 10th district was emptied on Monday.

"The haul has been good," said Marion Escarpit from a local anglers' association, emptying a bucketful of fish and rubbish.

"We have found very few fish that are sick or malformed. That's surprising when you see what's there at the bottom of the canal."

The dredging also allows authorities to repair the canal's walls and renovate the locks.

The rubbish tossed into the canal includes beer bottles, bicycles, toilet bowls, rolled-up carpets and weapons, including a sawn-off gun.

"We haven't found the body yet," joked hydrobiologist Romain Zeiller, one of the officials involved in the project.

The last clean-up in 2001 yielded a formidable amount of detritus including motorbikes and bathtubs.

But the quality of the water has improved over the years and marine life in the canal has burgeoned.

"In the 1980s, there were only two varieties of fish in Paris," said Escarpit. "Now there are 35."

The operation will last until early April and will cost the city 9.5 million euros ($10 million).

The waterway was commissioned in 1804 to transport goods into the capital as well as provide it with fresh water.