In article .com,
says...
My friend and I are going rent a cabin on a private lake in Michigan's
UP. The owner was giving me details about the lake, saying that most
of it is 120 feet deep, but it goes as deep as 450 feet in some
parts. That lead me to believe that there must be some monster bottom
feeding fish in the lake. ...

I don't think you're going to find much of anything past about 50'.
Generally not enough dissolved oxygen in fresh water past that depth.
Further, bottom fish don't generally stay suspended in water, meaning,
they will be very near the bottom at 50' or less.

MM