This is a curious and concerning story. Later this month data will be released that underpin this. Are we seeing similar impacts elsewhere?
http://www.independent.co.uk/voices/comment/the-loss-of-scottish-salmon-is-a-cultural-catastrophe-10158356.html
Just to give some background information for those who are unfamiliar with recreational fishing (angling) in Britain. It is a very popular leisure activity, and still practiced widely. Once you have some basic equipment then it costs very little to sit for several hours, in wind, rain or sunshine, immersed in deeper thoughts.
The link below is a very thorough paper, but does not include Scotland ~ you can get a good idea though. [General population figures are 5 million in Scotland; 3 million for Wales; and around 50 million for England. Scotland, Wales and northern England are mostly rural; southern England is densely populated but still has some rivers and canals].
http://www.fao.org/docrep/005/w0318e/W0318E20.htm