This is damn near a yearly problem growing rice near a river. The easiest way I found to catch them in the south is with a 330 conibear. Just find where they have a ditch dammed up. Dig a ditch through the top of the dam just wide enough to get your trap in and deep enough that they can hear water running down the backside of the dam. Funnel them into it with sticks stuck in the dam and don't forget the top of the trap to keep them going over the top. You'll get damn near one a day until they leave or you kill them all.
I never snared one this way but if that's what I had to use, this is how I'd start. You'll catch a otter every now and then doing this so if that's a problem, you've been warned
