Way back in the early fifties, I used to fish the Otanabee in the late evening/nighttime for smallmouths with surface plugs...we threw them in the freezer and gutted them the next day or so while they were still frozen, chopped the heads off, and once thawed we would then fillet them...the guts stayed in one frozen clump so there was no contamination...must of been ok as we ain't died yet...