Mark,question first on your under ice beaver sets?Is there a feedbed showing?If there is where are your sets?Mike and I have taken several beaver in the last week or so,but we set around the feedbed.
As far as avoiding otter goes,they will come to castor mounds.I usually do not even make otter sets,as I fill my tags at my castor mounds.You may want to go with baited sets in open water.
I started my beaver career with only baited sets,I looked like a tree farmer driving down the road ,with a roof covered by popple limbs.
Tom