Not sure on the bug.
The size of the gill in that perch doesn't surprise me a bit. I have found several types of fish with large prey in them. After a few finds like that I started using bigger baits at times. 2inch plastics find their way down my ice holes quite regular tense days. Go back there and anchor some 2-3inch gills to bottom and see what you get!
Another bait people don't use in winter is crawdads. I find them in bass at times so they are worth a try too.