I have no doubt there are not so many silver fish showing in the Ironbridge/Shrewsbury town centre winter holding spots which were the traditional match stretches. This imo can be attributed to two major changes which have occurred in the last 20 years.
The first and most obvious is increase in fish eating birds, in particular the ubiquitous black death. These birds have ravaged the adult stocks leaving once prolific areas virtually devoid of fish. Three winters ago I counted over forty of them roosting in the trees covering the gorge just downstream of the power station and feeding in Ironbridge on the Dawley match stretch. No fishery can withstand that amount of predation and over the next couple of years as the fishing declined so did the amount of Cormorants until this winter where I've not seen one, probably because there is nothing left worth hunting.
The other contributing factor to the decline is the loss of the weed in the river.
20 years ago you could literally walk across the river in the ranunculus without hardly getting your feet wet and in high summer there would be solid white flowers from bank to bank in shallow areas. This prolific weed growth not only provided a medium for the fish to attach their spawn it also provided a refuge for the fry from predators and flood, a natural larder, and helped slow down the rivers race to the sea holding summer levels at a reasonable level rather than letting the river drop to it's bare bones during dry spells as it does now.
There have been several suggested reasons for the decline in the weed growth, many people suggest the reason is the high summer floods ripping it out, this could be a contributing factor but I think the changes in farming practices and the improvement in long range weather forecasting have allot to do with it. Farmers today are allot more carefully about what they spread on the land and when they do it. A few years ago adding nitrogen to growing crops was done with a scatter gun approach, everywhere got a bit whether it needed it or not and if it rained the next day it all ended up washing through into the water table or direct into the river. Nowadays soil samples are taken at various points through the field and plotted onto a sat nav system and an intelligent spreader delivered a measured dose where needed, if heavy rain is forecast that is factored in and the dose is adjusted accordingly.
This is a good thing really but it does have an effect on the whole river which we anglers might just have to get used to.