Fifty years ago, the Thames was declared biologically dead. In October, Britain's most famous watercourse was awarded an international conservation prize for rivers that have undergone outstanding restoration.
The award of the Theiss River Prize is further confirmation of a remarkable transformation in the fortunes of the Thames river environment and the wildlife that it supports. Back in 1957, oxygen levels in the river were so low that no creature could live beneath its surface. The Thames was dead, the culmination of decades of neglect, with the river treated as little more than a drain for industrial waste, chemical effluent and London's sewage.
Today, the Environment Agency can paint a very different picture of the Thames. More than 120 species of fish thrive beneath its surface; salmon have been reintroduced, trout spawn in the tributaries near London, and large nurseries of sea bass and Dover sole tempt anglers in the lower reaches. Birdlife spotted regularly includes kingfishers, grey herons and numerous species of waterfowl, waders and sea birds. Seals have been spotted resting on the river's banks as far up as Richmond, while dolphins and porpoises regularly make diversions from the North Sea, chasing schools of fish. The Environment Agency says that the Thames is the cleanest that it has been in more than 150 years.
RETURN OF THE OTTER
Although the transformation of the Thames has been widely recognised here and abroad, the bigger picture is of an entire national river system that is now cleaner and more able to support wildlife. One key species that symbolises the degree of improvement in England's rivers is the otter. Less than a week after the award of the Theiss River Prize, the Environment Agency reported that otters had returned to every English county except Kent. The Agency's fifth otter survey, conducted between July 2009 and March 2010, examined 3,327 river sites across England and found that the number of locations with evidence of otter life had increased tenfold since the first survey 30 years ago.
The presence of otters is an excellent indicator of a river's health, as these sleek and beautiful mammals are at the top of the food chain, with a voracious appetite for fish. Like the River Thames, England's otter population has come back from the brink. And according to the Environment Agency, it's the River Thames that has seen the biggest rise in otter sightings since 2002.
Although the chances of seeing an otter have clearly improved in recent years, luck still has to be on your side if you're going to see one. However, a river that is frequented by otters will also be a river that supports many other, less elusive species. Swans are among the most conspicuous and abundant birds to be found on our rivers and are a favourite subject for photographers. The graceful curve of their long necks and clean white plumage stand out on even the greyest of days.
Another large bird to look out for is the grey heron. Its numbers have increased as more and more fish return and spawn in British rivers and tributaries, and it's now regularly sighted on the banks of urban rivers in major UK cities, including London. Herons are wonderful subjects for the camera because they stand perfectly still for long periods, with their long, stick-thin legs steadfast in the water and their eyes staring down the length of their razor-like bills for fish. Nothing moves, which makes the sudden strike into the water and emergence of fish firmly trapped in the bill all the more surprising. Look out, too, for smaller varieties of waders, such as moorhens and coots, and the many species of goose and duck, both native and introduced.
The recovery of Britain's river habitats in recent years means many species that were threatened with extinction are now slowly but surely rediscovering their habitats of old. …