"The past ten years has seen huge improvements in the quality of the river water and many people are not really aware of that. They still retain memories of how it was decades ago,"

Pat O'Brien is talking about the River Aire, the waterway that plays a major role in his work.

As fisheries and recreation technical team leader (rivers) with the Environment Agency (EA), he has for 28 years overseen programmes of work to improve the Aire. And he is delighted with the results.

The water is clean and clear and supports a wide variety of wildlife.

"The water chemistry is very good, it has improved dramatically," he says. "Now there are brown trout all along the river, from top to bottom."

Trout dominate above Keighley, while below coarse fish are more prevalent, with a mix of grayling, chub, barbel, dace and gudgeon.

The EA is midway through a three-year stocking plan for all the coarse fish species. "Grayling, for instance, do not spawn successfully every year, so we stock the river to fill in any gaps and help develop a sustainable population in the river."

In March this year about 2,000 year-old grayling were released into the Aire at Bingley and Silsden Bridge.

Sampling is carried out to check the size and health of the fish, and identify any problems. The effects of pollution manifest themselves in fish scales, so can be picked up during an examination.

Other activities blighting the river include livestock having access to a watercourse. "They can trample the stream bed, cause damage to it, and cause pollution," says Mr O'Brien.

Water quality tests are also carried out.

A massive overhaul of Yorkshire Water's sewage treatment works at Esholt has been a major contributing factor in cleaning the river and tempting river life to return.

A £110 million programme of work has been carried out under the EU's Fresh Water Fish Directive, as part of Yorkshire Water's River Life scheme.

River activist Kevin Sunderland is full of praise for the company's efforts.

One of the main barriers to fish migration are the weirs - a legacy of the area's industrial past. The River Aire has more than 30, at intervals from its upper headwaters near Malham in the Yorkshire Dales to Chapel Haddlesey near Selby, and fish passes are being installed at many.

"We are working on about half a dozen passes at the moment," says Mr O'Brien. "We are targeting five or six weirs in the Leeds/Bradford areas. Our priority is to make the obstruction passable. We have to adapt them to make them more fish-friendly."

These include weirs at Hirst Wood, Saltaire, Baildon and Rodley.

In Bingley the EA has been working in partnership with riverside developers to allow fish to negotiate the weir at Ireland Bridge.

"The more fish, the more opportunity to go fishing. The focus is not to make the River Aire a salmon river, it is to improve the river as a coarse fishery. Most fish, like barbel, chub and dace, need to be able to move up and down the river - some species travel distances of up to 30km as they migrate upstream to their spawning grounds."

Salmon are back in the Aire in the lower reaches downstream of Knottingley Weir.

Otters and water voles are also making the riverbanks their home - returning due to the increased food supply Maintaining the quality of the river, and other rivers in the region, is a task that requires a commitment from many different agencies. The EA works with local authorities, wildlife groups and developers.

Paul Tullett, Ridings (West, South and East Yorkshire ) area manager for the EA, stresses that the agency's work in regulating industry had been a major factor in the improvement of the river.

"The River Aire is a huge asset in the district. We have made massive inroads in improving water quality."

Says Pat O'Brien: "Anyone who looks off a bridge now - particularly those who have not looked over a bridge for a long time - will tell you the river looks cleaner than it has for ages.

"It has been extremely satisfying to witness these massive improvements, with changes over the past decade being the most significant."

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