Worm,Otter are not difficult to catch.I never use bait for otter,I do catch several a year in my lured castor mound sets for beaver.
Gang setting is a very good idea,otter travel together a good portion of the time.I did have several doubles this last season.The last double was 2 large males,the pelts were 73 inches and 72 inches long(this was from nose to tip of tail before stretching).
If you can set beaver dam crossovers,do so.These are otter hot spots.Narrow channels,crossovers from one body of water to another are also dynamite.Body grippers are my trap of choice.I did take 1 in a 220 this past season,but I do prefer the 330.Many trappers like the 280,but I do so much beaver work,that the 330 is just easier for me to use on both animals.
I spend more time trying to avoid catching otter,than I do catching them.
Our limit is only 4,so any accidental catches over this number,must be turned in to our DNR.
Tom