google 'mink trap' you will see tons of pics on there... as for bait, some things that have worked for me are fish, rabbit, game, tinned sardine, another thing that worked well for me is that potted meat paste(fishy type) you get in the wee jars... leave opened in a warm place for a couple days or so, you will smell when its ripened lol, then hey presto mink bait, just smear on back of trap and a bit on the back of footplate.
Cover trap with either natural materials or make a wooden cover, so that it looks dark and inviting and easily accesible from the riverbank . good luck and good on you f