I have a chance to get a number of 12"-14" x 4' black plastic culvert pieces. I was wonder if I drilled holes in them and sunk / stalked them down in the river and had conibears at each end would that alone attract the otters swimming by. I have a couple spots I could put them in the river right at my house. I have an otter toilet on the river bank but its on the shallow flow of water only a couple inches deep where they exit to the toilet.

Try it and report back. Might work.

A few yrs ago there was an article and pics of building a float set for otter with those culvert pieces. Maybe Trapper and Predator? Hopefully someone else will chim in.

I watched a YouTube video once where the guy made something like what you are describing. He used 12 inch pvc pipe and some square tube. He claimed to have good luck with it. If I remember correctly he stated it worked best if located where the otters would be hunting for food. Search Otter trapping on YouTube, it may still be on there.

Bottom edge sounds like the right place for them......jk

Contact Eagleye, he has posted pics of his. Work great.

There is a you tube video on someone using big pvc pipe for underwater sets. Try looking that up.

I've used them for several years. But I'm trapping them in my pond. 12" x 4'. 220 fits right in. Also I stick a soft plastic fish on the trigger. The fake fish isn't necessary all the time but why not? They'll dive through on their own but I don't want to miss any.

Here is a link to the float set: https://trapperman.com/forum/ubbthreads.php/topics/7079774/1

A large plastic shad lure dangled in the middle of a floating pipe will help to talk a hesitant otter to see if his head will fit a 220.