It is temptingly easy for anglers to blame loss of sport on obvious targets like otters or cormorants, but I think our community often does so without any actual evidence beyond anecdote and rumour . Even getting data on past catches is hard and some anglers of my age (f***ing ancient ) don rose tinted specs about their salad days on the river , when rivers were cleaner and fish were more numerous . My own diaries go back almost 50 years now and on the waters I fish reveal sport which was often, but not always ,far worse than it is now .
For many years I have been involved in invertebrate sampling as part of the Riverfly Partnership and it is a very useful tool to evaluate water quality and food availability - a sort of canary in a coalmine if you like. But if I mention this to some primarily coarse angling clubs, I tend to get blank looks and indifference . Some of that is down to ignorance, but as often as not is the fact that minds have already been made up - it's otters , or (in one local case ) it was , apparently , a source of pollution which they had been told about but which was being hushed up by 'certain people'. The reality , I suspect, is much more nuanced - rivers can decline because of a whole host of factors , often in combination - abstraction, pollution , drought, flooding , predation , climate change , agricultural run off, invasive species, disease , habitat loss , new industry and God knows what else .
But oh how we love the quick and dirty (and crowd pleasing ) diagnosis - " It's effing East Europeans/ otters/mink / zander/ Sooty's fault" and the facile solution '"restocking !" . Really , in a river with a problem - how does that work?
One thing I am getting involved in this year , and I'd encourage others to do so , is the 'Citizens Science' Water Quality Monitoring Network - the more hard data we have about pollution the better placed we are to act on it .More on Angling Trust website about this