Cats will be a problem. I would make a V and place bait at the tip of the V with a leg hold trap before the bait, but that is a sure way to get cats, too. You can use sizes 1 1/2 or mink, 2 for fisher, I think. I have not trapped a lot of fisher, two is all, so I am a long ways from an expert. I would use the double spring jump trap on them to try and get higher on the leg. BUT with cats, that you like or even kind of care for, you could be forced into a live trap, or a box trap like was described for weasels, (just a bigger hole) But that may not keep out all cats either. As much as I like Cyrus's coop, the one thing I would change is the ramp, just to make it harder for a fur bearing critter to get up to the roosts. ( Sorry Cyrus) Do you have a ramp in your coop? I would take it down and make the birds fly up there. Can you lock the cats up? Without knowing the terrain you live on, it could be just a single male passing through. (but you will never know and that can be worse than having one you get rid of.) Needless to say, if and when you get rid of him, the best thing you can say is "he is gone" or "he has moved on" and do not elaborate. No sense inviting a visit from a Deputy or the local warden, even if you are in the right. On the other hand, If you know the local wardens well, and if he seems like a square shooter, you could ask him what he thinks before hand. I kind of think he would say if the mink/fisher has not done any damage you have to leave him alone. ( your call) Maybe if you have a place surrounded by water you could set a trap there, if a cat cannot get there. That however, could be seen by the local warden as trapping a mink/fisher that is in it's natural element and not threatening your animals. Predators are such a pain, good luck.