IT was the reappearance of the otters which made people realise how much the River Wear had changed. Photogenic and much loved, the creatures inevitably grabbed all the headlines as the ultimate symbol of the waterway's welcome return to health after decades of abuse.

But while it is certainly true that a river's health can be gauged by the presence of animals at the head of the food chain, it was perhaps a wholly more unspectacular creature which truly confirmed the renaissance.

Most people have not even heard of the banded demoiselle damselfly but, largely unnoticed by everyone but the most ardent naturalists, it has been steadily colonising the river for the past five years. A beautiful insect blessed with a brilliant blue/green body, banded demoiselle is common in southern England but its previous Northern strongholds were small wetland pockets south of Middlesbrough and the Lake District.

Now the insect is on the Wear which is remarkable because banded demoiselle are notoriously vulnerable to pollution.

Their presence even ten years ago would have been unthinkable for a river poisoned by sewage and industrial waste along its highly-populated mouth at Sunderland and by toxic minewater and run-off from gravel workings upstream.

Such industries may have been the lifeblood of the region's economy but they spelled death for wildlife.

However, as heavy industries closed and surviving companies assumed greater responsibility for protecting the environment in line with tough new British Government and European Union legislation, pollution decreased and the wildlife began to thrive once more.

Stuart Priestley can clearly see the results. Last August, he became the Otters and Rivers Project Officer for the Wear in an initiative backed by the Durham and Northumberland Wildlife Trusts, Northumbrian Water, Northumbrian Water Environmental Trust, the Environment Agency and Blue Circle, the cement company with a plant in Weardale.

Leaning against a bridge parapet at Witton-le-Wear near Bishop Auckland, and surveying a dipper flitting low and fast beneath trees overhanging the water, Stuart says: "The Wear was in an appalling state due to the level of pollution. Today, it is a lot better and its health is good although we are still tackling some problems in the tributaries. Some of the coastal streams, for example, are still quite polluted. However, what we are seeing now are small pockets rather than a widescale problem.

"We have good numbers of wildlife again, including insects such as dragonflies and the banded demoiselle, which is very sensitive to pollution. There are salmon and trout throughout the catchment. The improvement in water quality has been incredible. It has been the most important factor," says Stuart, who is based at Durham Wildlife Trust's reserve at Witton-le-Wear.

Remarkably, the Wear has also recorded the nathusius pipistrelle bat, which was only added to the list of breeding mammals in the UK when a roost was discovered in Lincolnshire in 1994. The first record in County Durham was on the River Wear. The presence of bats suggests a strong insect population and there are plenty of wildflowers along the banks.

Stuart cites partnership as the reason for the improvements, bringing together naturalists, organisations responsible for improving water quality, primarily Northumbrian Water, the Environment Agency and industry, and landowners who can create the right type of bankside vegetation favoured by wildlife.

The ultimate symbol of their success is the return of the otter to old haunts because the presence of the top predators means the food chain is intact further down.

Otter numbers nationally crashed during the 1950s and 1960s due to the introduction of highly-toxic new pesticides and the creatures found it difficult to fight back once the chemicals were banned because rivers like the Wear were badly polluted.

Now otters are streaming south from their over-populated strongholds in Northumberland and are once more present on all the main rivers in County Durham.

Stuart says: "A survey of the Wear in 1992-93 showed no signs of the otter - the animal had the potential for extinction - but now they are back on all the watercourses in the catchment, including the tributaries, although probably not in large numbers. The situation is definitely improving. There have been rumours that they are breeding but they have proved difficult to confirm."

Further north, it was the appearance of otter cubs beneath the Tyne Bridge which made local people realise how much their river had been transformed.

At one time the clash and clatter of the shipyards, factories and engineering plants ranged along the banks of the Tyne drove the animals away and they only returned when traditional industries began to close during the dying embers of the 20th Century. Formerly polluted sites fell silent and became derelict wastelands which were once more colonised by otters who liked the peace and quiet.

Dramatic improvements in water quality also helped because it allowed an increase in fish numbers; the loss of heavy industry's toxins and Northumbrian Water's moves dramatically to reduce sewage pollution mean the Tyne is now one of England's finest salmon rivers.

Kevin O'Hara, Stuart Priestley's counterpart at the Northumberland Wildlife Trust in Newcastle, says: "The decline of the heavy industries along the Tyne came at the same time as the general need to improve the quality of the water. The otter has begun to flourish again on the Tyne and will keep expanding as long as it does not face barriers - being killed or suffering from pollution."

Mr O'Hara says a mother and cubs has been spotted close to the Tyne Bridge and naturalists, agencies and industry are working together to ensure that commercial redevelopment of the riverbank allowed for the otters' needs.

He says: "We are trying to ensure that the riverbanks remain ideal for otters. Man has a tendency to want to tidy everything up but the otter does not look at the river in aesthetic terms. People may be surprised to hear that otters are happy to live amongst us but all they want is clean water, food and somewhere to shelter and have babies. Business has to be on the riverbanks. What we are trying to do is look at ways to also protect the landscape for otters."

The presence of otter cubs just metres from bustling city centre streets suggests that the battle is being won.

l In the next article in the series, John Dean heads south to the Tees, the river which came back from the dead