Thanks all for the responses! You are right mink do have a taste muskrats. When I was a teenager and trapped them the colony traps were the most efficient method I found. I still have some of those traps!
The trouble is that it is deep enough that I can't figure out which runs are active and some of them I can't reach.
I might have found a solution for deeper ponds like mine. I just ordered a floating colony trap from an animal control supply company. You basically anchor the trap away from the bank, bait it and add some muskrat lure. The rat is attracted by the lure, sees the bait, climbs on the trap and goes through the "colony" style door and can't get back out. The cool part is that there is a hole in the center of the trap that leads to a submerged compartment. The rat dives in because it thinks it is open water but instead it drowns. The trap is ready for the next excavator!
