x3 on finding their toilets. Look for their terds filled with remains of fish - bones, scales, crawdad and snail shells, etc...
They will frequent abandoned beaver huts too, and sometimes live in them for a while. Many a toilet will be nearby these huts too. Check your regs for setting on these, some states have setback from beaver huts as far as trap placement.
Otters are very curious. I have heard from some old timers that they wrap a brick in aluminum foil, shiny side out and it grabs their attention, maybe that sort of thing up on the bank could draw them? Of course it will attract curious people too if they happen to be around.
If you have backwaters and beaver ponds, just target the beavers and eventually you will be happily surprised with a bonus otter, focus especially on channel sets and spillways
