If the pond has channel cats and they are breading successfully (or overstocked to begin with), then you may have an overpopulated pond that needs to have a bunch of them removed to make more room and, hence, more available food for the remaining fish.
That fish looks real healthy, so it's not too bad of a situation to be in.
Get some pics of the smaller ones to identify. If bullheads are present, it may be time to do some trapping and really get their numbers down.
There's allot of things that can be considered and you are in the right place to get great advise. Stick around and welcome to the club!
