Was about to say the same thing as coeus, feeding a cat to fish is a no-no but everyone will happily feed fish to their cat with no complaints.
So the next arguement would be that fish fed to cats is normally dead and prepared. So then what would be the problem with killing the kittens first (drowning in a sack i think is an old favorite) preparing them (de-furring, filleting, etc) and then feeding them to the fish?
(please note, i'm not in favour of feeding cats to fish, just pointing something out.......not sure what that is either though!...........besides, i'm sure puppies taste nicer)