[CA] Blue spheres RV-100

Hi, I am running an Axiom Pro with an RV-100 transducer. While running I see a big stream of blue spheres on the screen behind the boat. I am wondering if the spheres could be aeration under the boat from improper transducer placement? The boat is a twin outboard with the RV-100, placement 3" starboard of the keel, no strakes inline, a B 60 thruhull a few inches further starboard.The mid-line of the transducer is level with the bottom of the hull. Could this be a placement problem? Can't believe I'm seeing that many fish.
Thanks,
Mark