Wow, I never heard of using a whole opossum for bait, much less a large adult ‘possum! However, I suppose a 100 lb. blue catfish could swallow a large adult opossum. Very large blue catfish are generally piscivores, consuming mainly live fish, but most sources indicate a monster blue would one go after a rotting opossum.
Tough parts make good bait for smaller, table fare catfish. I’ve done that a couple times. (I don’t keep catfish over 8 lbs. or so - becoming piscivores means they accumulate more toxins.)
As for the possum, oh, he was dead - he stopped breathing seconds after the head shot. But then something else dragged him off later.
I stopped eating tinned fish. Purines and gout. I do understand that anchovies make good bait though!
(If I were in Wisconsin I might eat perch or walleye if it came from a clean lake!)