Yep I did wonder about the amount of scoff the Otter needed. But evidence regarding Otter kills and Mink kills is to say the least a bit confusing when I have tried to research the subject. In fact some say the mink is more picky than the Otter but on reflection I believe that you are right in that the Otter will just take a few nurtitional organs and leave the rest.
The Mink is related to the Polecat and is a very efficient scavenger, so it would be feasible that they would devour the whole lot.
Sure the Otter has a wide choice on it's menu including crayfish , mussel etc and I believe other mammals too,. But I fish areas where there are Otter, nothing exclusive about that, and yet despite actually seeing the occasional Otter, and certainly seeing the footprints, I have yet to see the bankside littered with fish corpses, I know there has been 'evidence' as such such as Adams Mill, but as a layman I would expect to see this in some numbers if we are really blaming the Otter for declining fish stocks, and considering it's rather picky eating nature.
So there is a great deal of circumstantial evidence but nothing that would stand up in Court, but I will keep an open mind about the subject, but I do believe we should leave
no stone unturned in seeking the truth about declining fish stocks.
However I suspect the truth is out there and would be a very unpalatable dish indeed, the Government have dragged it's feet over protecting our Coastal Fisheries, ignoring several reccomendations, and that is a commercial need where jobs are at stake, so any study into decline in freshwater fish stocks for leisure pursuits I imagine will be way down the list of priorties.
Oh! and thanks