I tried for 2 weeks about ten years ago putting live fish in the bottom of a 5 gallon bucket in a clear stream guarded by a 220. That did not work. I caught a bunch of otters, but they were in standard sets after I took out the buckets in the same stream. I know of others that it did not work for, also. One of those is George Wacha from Alabama.
I have caught them on a couple occasions using live fish in shallow water using live fish for bait in a Koro at a crossover.
I tried fish on the 330 trigger with no luck on otter.
I know of several instances, recently, where otters were entering tanks at fish hatcheries and submerged cage traps with live fish, on a stringer in the trap, was used for bait and otters caught. They prefer catfish, trout, or an oily fish.
The larger the more open the better. Traps were set on the bottom.
Grandpas trading post makes a cage that has a simple push door the otter find the door to get in and can,t get out. You just put fish in and submerge trap. Bill Weeks, the original maker of the trap, said he had best luck using crawfish or frogs for bait. The frogs would be used when the trap was floated.
I would think as beaverfoot said that a hoop net would work, but in the years trapping turtles I never caught an otter in my hoop nets or new I had one in the trap. Plenty of alligators, but no otters. I really see little difference than a cage when submerged. I would think I would want heavy netting on the hoop net.
I forgot, I have a relatively recent picture of one caught in a cage in Tenn., at a dock, but I don,t know how it was baited.
Dave Vinke would be a good one to respond to this one.