otters are weasels. just another member of the whole stinking family. skunks, weasels, ferrets, mink, martins, badgers, wolverines, otters. they are all the same. kill for fun half the time. #2 steel traps around the bank baited with eggs. set 4 or 5 in a cluster. stake them down. if you put a drag on them they will drag it into the pond and you will lose it when it hooks something. beaver traps work well too. just stake them in the water around slides and they drown. a good rifle and patience works too. they are hard to live trap. it can be done but it's hard. set the trap in the edge of the water and bait it with eggs. if you have ducks that nest around the pond they will eat the eggs and the ducks if they can catch them.
another option is a mid sized gator. most fish (except bottom feeders) are too fast for it. the otters are too for the most part, but you try catching a fish while something 2 or 3x your size is trying to eat you.