I had otter problems a few years ago. The otters will have slides into your pond. I used chicken wire and fenced off 10-15 feet on both sides of the slide and put my trap where they had no choice but to enter. Otters come and go. In my area they might be gone for a week or more before they return, but this setup is no fail. I do the same with toilets, giving otters one way in. You can also make a fence with sticks that are poked into the mud, not laid down, but vertical.