Went out today in the Cumberland River..Tried out my HumminBird 525..Never used a fish finder before..Thing works GREAT..I was fishing water in the 35 to 50 ft range...I saw lots of fish at the 25 ft range..They showed up as fish icons with the beep..Now I also saw lots of BIG fish on the bottom in the 35 to 50 ft range around humps and ridges.....I was using frozen skip and I never like bait after its been froze but I was marking the hole,,anchoring out and putting the bait right in the middle of them...NOT A SINGLE BITE?????????????Could this have been carp????Is there any way to tell the difference on a fish finder?