THE Thames’ journey from being biologically dead in the 1950s to a thriving waterway has been recognised with an award of the world’s largest environmental prize.

Its transformation from a river polluted by heavy industry into one teaming with fish, including salmon and sea trout populations, plus otters, has seen the Thames chosen from hundreds of waterways across every continent as the winner of the International Theiss River Prize.

The iconic symbol of the capital beat the Yellow River in China, Hattah Lakes in Australia and Japan’s Smirnykh River Partnership in the finals of the competition that celebrates outstanding achievement in river management and restoration.

The Environment Agency said the chemical quality of the Thames has improved from 53 per cent in 1990 to 80 per cent in 2008, while the estuary supports shell fisheries and is a nursery ground for commercial sole and bass stocks.

There are 125 different fish species, including internationally important smelt and shad.

Peter Quarmby, the Agency’s Flood Coastal Risk Manager, said: “The Thames’ remarkable recovery over the past 50 years is a testament to the dedication and hard work of many people and organisations.

“Tighter regulation of polluting industries and our work with farmers, businesses and water companies to reduce pollution and improve water quality, have all helped to make the Thames a living river once again.’’

But, he added, “the recovery is fragile, and under increasing pressure from a growing population, ageing infrastructure and climate change. Through innovative projects such as the Thames Tideway tunnels and the London Rivers Action Plan, we and all of the people and organisations we work with are proving that we are tackling these challenges head-on to ensure that the Thames remains an iconic river for many centuries to come.”

The Agency launched an electro-fishing boat in the Lower Lea oearlier this month to survey fish species.

An electronic pulse transmitted into the water causes the fish to come to the surface and a large number of eels were also found.