You could be right mate. On my local river, there used to be a few really good stretches of bank either side, that you could guarantee a couple of kills from practically every time you took the dogs for a walk there. The last maybe close to 20 years, I've not seen one rat, or signs of, there at all. Seen a few mink in the same space of time though. But strangely enough, there's more ducks, mallards, widgeon, teal, even little grebes, and all sorts on there now the last few years than there's ever been ?