The smelts at "Wonder" Lake that I went were decent sized about 8" average size. Minnesota has recently outlawed use rainbow smelts as bait due to VHS regulations and the smelt being invasives so I can't use the smelts as bait. However you can use Hooligans (larger smelt species) as dead bait for northerns, lake trout and catfish. Catfish should be biting soon in the Mississippi River very soon, caught a 12lbs channel catfish last spring which is a big catfish up north of Minnesota.