CRAVEN anglers could be reporting the capture of fine, fresh run salmon from the River Aire in five to 10 years time if forecasts from the Environment Agency prove accurate, (writes John Preston).

At a time when anglers are lamenting the deterioration in fish stocks in local rivers, the return of 'the king' for the first time in 180 years seems a strange prediction, but it comes from a curious set of circumstances.

The chance to fish for salmon in the Aire is, on the face of it, a mouth-watering prospect, but the presence of the species comes at a price some anglers may not be entirely happy to pay. For the return of the salmon in most Yorkshire rivers comes at the expense of coarse fish.

Ironically, while the work done by the Agency in clearing pollution and sewage from Yorkshire rivers has brought the improvement which has tempted salmon to return, it has conversely led to a decline in coarse fishing stocks.

At the Environment Agency's Fisheries Forum in Leeds last week, it was more or less confirmed that the coarse fish population in Yorkshire's rivers is unlikely ever to equal those of, say, 40 years ago.

All of the rivers - the Ure, Swale, Nidd, Wharfe, Derwent, Don and Calder - have seen their coarse fishing deteriorate gradually since the 1960s, with the loss of the small fish first and then the bigger ones.

The upper reaches of the River Aire above Bingley are the same, although further downstream, the coarse fishing is still quite good, with all fish present in the river around Leeds.

The reason for the loss of the coarse fish has been blamed on the gradual cleaning up of the rivers. Industrial pollution has been substantially reduced by either factory closure or by stricter discharge consents.

Sewage treatment works have undergone massive investment, resulting in much cleaner discharges, and this work is continuing to clean up the few remaining waters such as Bradford Beck, where pollution through storm water outlets still kills fish.

It is the cleaning up of the sewage outlets that has had the biggest effect on coarse fish populations. Apparently, some sewage in the water has been beneficial to them in providing food for both the fish and insects etc., thus increasing the food chain even more.

The River Calder is the latest water to suffer a drastic reduction in coarse fish and follows the trend experienced on what was one of England's finest coarse fishery, the River Trent.

The lower reaches of the River Aire still feature some sewage in the water, but are likely to become cleaner over the next few years.

Yet while the coarse fish population is in decline, other species are in the ascendancy, with trout and grayling now very numerous on the Calder and most of the other Yorkshire rivers now seeing the beginning of salmon runs.