Trout caught in London again after river is transformed

It sounds an ecological impossibility, a trout stream in the middle of London. But trout are flourishing in the river Wandle, one of the capital's largely forgotten rivers such as the Fleet, the Walbrook and the Tyburn.

It sounds an ecological impossibility, a trout stream in the middle of London. But trout are flourishing in the river Wandle, one of the capital's largely forgotten rivers such as the Fleet, the Walbrook and the Tyburn.

The Wandle has been reborn in one of the most remarkable environmental transformations seen in Britain. In 25 years, what was a lifeless drain through industrial estates and dense Victorian housing, entering the Thames just down from Clap-ham Junction, has come alive with substantial fish such as dace, roach, chub and barbel. Most astonishing is the population of brown trout, fish which need clear, well-oxygenated water. They are the surest sign of river health.

Last year, a fly-fisherman caught a 2 ¹/ ₂lb trout in a section of the river next to Wandsworth council's bin lorry depot. This is believed to have been the first trout caught in London for 70 years, and the first caught on the fly for more than a century.

The Wandle runs for nine miles, from Croydon and Carshalton, at the foot of the North Downs. Even in its lower reaches, where it joins the Thames, fish can be seen. Under the bridge carrying the South Circular Road, in the Wandsworth one-way system, shoals of dace dimple the surface of the clear water.

All along the river, beside factories and derelict sites and housing estates and shopping centres, there are fish: gudgeon, roach and, most notably, pods of big chub, some of which are three-pounders, or even heavier.

Every few hundred yards or so, a fisherman was after them. The guide was Alan Suttie, a former illustrator and local resident who has perhaps done more than anyone to raise the Wandle's profile, running projects involving fund-raising, restoration and cleaning work, and the education of local children in the wonders of their recovering river.

A keen fisherman for 47 of his 53 years, Mr Suttie speaks with passion of the Wandle's rebirth, and with humour of the obstacles to it, such as the rubbish still regularly dumped in the water, supermarket trolleys being a special bugbear. "I'm sure the supermarket trolley is becoming an indigenous species and will eventually breed," he said.

But later, standing on a bridge on a lovely stretch of the river in Morden Hall Park, he said: "One day this will be a salmon pool." And it was difficult not to believe him.

The rebirth of the Wandle has been possible because it is the most prolific sort of trout river, a chalk stream, fed by pure water from springs in the North Downs chalk, the same sort of watercourse as celebrated trout rivers such as the Test and the Itchen in Hampshire, and the Kennet in Berkshire.

Wandle trout were famous. Frederick Halford, the Victorian angler whose writings gave birth to modern fly-fishing, was a Wandle regular in the 1860s and 1870s. But London industry was drawn to the river to take advantage of the powerful flow caused by its relatively steep incline; it falls 100ft in its nine-mile course. Eventually, its banks were lined by 90 mills, producing goods from dyed cotton and leather to gunpowder and snuff. The once-pristine chalk stream ended up brightly coloured, foam-flecked, stinking and dead.

But the industry has dwindled and in 1995 Thames Water mounted a multimillion-pound clean-up after a sewage spill killed thousands of fish. As water quality has improved, aquatic insects and other small invertebrates, crucial fish food such as shrimps and water snails, have returned, and the Environment Agency has restocked it with several fish species.

Chris Dutton, the agency's local fisheries officer who has overseen the restocking, said that in 1980 when he came to the river, electro-fishing of several miles of it might produce one fish, and all the first restocked fish disappeared. But the trout that the agency stocked it with in 1996 are still there. "I think it's brilliant," Mr Dutton said "And it can only get better."