I could list many rivers like the Ivel Terry...
I was talking to a river keeper on the Windrush not so long ago, he looked after a stretch that once had double figured barbel, big chub, big pike and dace, the otters moved in and took the lot very quickly, in less than a year or so, they then decided to make part of the stretch a trout fly only water, because the coarse anglers didn't buy tickets any more, big rainbows and browns being were stocked, it wasn't long before the otters made in roads into the trout, so to keep an even balance between enough trout for fee paying anglers to fish for (not cheap) and the otters, he has to stock 30% more trout to basically buy the otters off, but as he said this from a financial point of view wasn't sustainable, now before some talk of pollution, loss of habitat for the fishes demise, this is a most beautiful stretch of river, with spawning shallows, gravel beds and supreme water quality, its the otters that have gone in and took the fish, he said for a period of time he would be greeted most mornings with the sight of big barbel, chub and pike with just their entrails and offal taken, not the actions of starving otters.