The crayfish murders - another victim...

Last month, I wrote a post on about a mutilated crayfish corpse on the river.  Having considered several suspects I concluded the most likely culprit was an otter.
In the comments section David suggest that it may be a badger - something I hadn't considered.  Badgers are surprisingly common, with an estimated 250,000 living in the UK and I have seen them near Abingdon last year: http://viewsoftheock.blogspot.com/2009/11/badger.html
Whilst walking to work and pondering the circumstances which a badger and crayfish are likely to meet I came across another dead crayfish:
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This one was found in a different part of the river, the lower ock along the ock valley walk in a place that is popular for people to fish.  It also has different wounds, the first one was ripped in half by what seemed like a frenzied attack, whilst this one has a smaller wound in the tail:
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Having examined the area, there are no obvious spraints, but it does make sense for otters to spend most of their time in the nearby Thames and occasionally coming into the shallower Ock to feed. 
Although if it had been an otter, it is  more likely the entire tail would have been consumed rather than just a small bite, unless it was disturbed.
Later in the day, there was evidence of more crayfish abuse, this time the culprit is obvious:
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Would a moorhen kill a crayfish? I doubt it, I suspect  this bird is just being opportunistic.
So if it wasn't the moorhen, then what was it? Although I still think the first crayfish victim was the result of an otter attack, I doubt this one was.  But to be honest, I'm not sure what did it, maybe it was just the accidental victim of an errant fishing hook.
Needless to say, I will be keeping an eye open for more evidence and as always, suggestions are welcome.