It’s the Herons on my river that are doing for the mallard chicks.I don't mind seeing the odd otter but numbers are going through the roof. You can see them across the whole river system. The predator prey balance is getting top heavy. I'm not talking about the fish they take but more the wildfowl, when I was a kid you could find dozens of moorhen nests, stretches of the upper ribble near where I grew up had hundreds of mallard on them but not anymore. Many years ago before the massive decline in otter numbers due to pesticides otters were hunted. I think hunting creates a healthy population, removing the old and weak, reducing numbers without big declines, just keeping a healthy balance.
The same applies for FEBs. If they were added to the general licence they would be controlled not eradicated.