Very true Baz, mink are ruthless killers, often killing in excess of their needs, hence the discarded corpses.
Eels are considered otters' favourite food for otters to kill and consume.
Mink will attack animals superior in size and it was considered this aggressive competition, was partly responsible for the decline in otter numbers, as well as other aquatic dependants.
Assuming mink took the otters' place in the predatory chain, their activities received a burst of frenzied publicity, (remember the hysterical pieces in the Sun etc late 60's & 70's) unlike the concerted efforts currently 'directed' against otters, .......... why?
If the trapping of mink is encouraging the return of the otter, are they co-existing rather than competing?
I have heard it suggested, that mink have driven otters away from running water onto still, but don't both animals range in their hunt for food?
That being the case, as you say, without actually witnessing incidents, how can these 'kills' be attributed solely to one, or other of these animals.
If the extent of the problem, warrants the consideration of 'specialist' (expensive)fencing around fisheries, would not a discreet cull, every so often, be a more financially viable option?
Is the increase in commercial 'coarse' fisheries and a paranoid owners reaction, actually behind the attention this issue is receiving, rather than a rampant explosion in the otter, or mink population?
A radically in-expensive alternative, might be to name all valuable fish. Predators would then know not to eat them and they'd have immunity from other afflictions to boot!
Do you think I'd get a fencing grant for my pond?