Humminbird 565 help

At Tims in TN I set up the 565 so it would see a 1/8 oz jig to 20 feet of water and turned the fish sensitivity down so it did not call it a fish. the water temp was 50 deg. I was in 12 foot of water. My question is every so often I would see a 5 foot oval with 1 or 2 fish at the back side and it would be about 3 to 4 foot from the top of the water. I think this is shad but I have not seen them in a small ball like this. Dose any one have any other ideas? Or do I not have it set up correctly?

it is shad because i run a 1197c si and a 565 and have seen the same more then once...they will run in small groups like that but dont see if offen...

Bait fish.

Thanks, for the info