John, for what it's worth, I fish a river that has been very hit and miss over the last several years. People have been blaming otters for the demise of the barbel, yet the otters have always been in the river, the barbel were illegally introduced 35 to 40yrs ago with the otters present as always and over the last 30yrs the barbels numbers exploded. Only four or five years ago, maybe less I could go float fishing and be confident of catching 10 to 20 barbel everytime. My best days trotting was 43, plus numerous chub, dace and trout. Anyhow, over the last several years things have slowed down quite dramatically and I myself have only been catching an average of one to three barbel in a session, sometimes non at all, however there have been lots of everything else being caught.
At the back end of last year I had my best catch of the year, it was either 13 or 15 barbel, I really have forgotton.
I knew the fish were still there in numbers because I could see them now and again and they just wouldn't entertain my trotted baits. I often switched to touch legering and I would usually pick one or two up, but, the fish just weren't having it! I really have no idea why. It was frustrating watching my bunches of maggots trotted down to them only to see the maggots slide over the fishes backs, or down their flanks and the fish paid it no attention whatsoever.
Now this year, although not brilliant for me as I haven't been out much, I do know of a lot of good numbers of barbel being caught by people I know.
Those same people were really adamant that the lack of barbel being caught was because of otters. Now those same people are having to eat their words!
Just to show how much barbel are frightened of otters, last autumn I was stood mid river, casting across to the far side, maybe trotti g the float about ten foot from the bank. An otter suddenly appeared porpoising up the opposite side and hung about diving around right in my swim!!
Within a couple of trotts through while the otter was in my swim I struck into a nice barbel. I had two more barbel out of the swim while the otter was still actually mooching in it.
Same thing happened to me a few years ago but on a small river, an otter popped up very much as a seal does, neck stuck up and head looking around, it saw me and vanished. I caught a dace a chuck after that!
Imo, pollution is the main problem, rather than predators. Lets be realistic, predators are the first things to be affected if their food source is deminished, so if there are still predators around there must be something to feed them, and enough of it to keep them coming back.
The above does look a little random and out of place on your thread, but, i'm trying to say that in all probability the fish are more than likely still there, something is just making them harder to catch....jmo mind ?.