Being that I only have a midrange fish finder, I seem to have difficulty distinguishing from small and large fish in deep water. Sure, I see fish, or what appear to be large fish, but how do I know if they're not large carp, or something else? My guess is that they're catfish in most instances, but I am curious as to what others may see or have on there finders? So, if you currently have a picture or snapshot of a deep hole with please post up, as I'd like to compare between depth finders? AND no, you don't have to show a GPS location, or anything like that, that would subject your honey hole or favorite spot at risk of us finding out. Any spot will do, just for comparison. I have a Hummingbird 545 or 645 and will post some picks next time I am out. I suppose when I read someone as saying, "I see big fish" how do you know they're big catfish? Maybe I or others will be able to understand their own depth finders clearly if we see different read outs or examples.