Even though bluegills don't get as large as most fish, they can be very aggressive amongst themselves and other fish if they think the other fish will give in.
I don't think catfish should be counted out. When my brown bullhead gets irritated because the other fish are taking the same exact piece of food he was about to eat and this happens 3-4 times, all hell breaks loose. He will go on a biting attack on half of the tank. If the fish keep stealing the exact piece of food the bullhead was about to eat, he goes on biting rampage over the whole tank at least 5 or 6 times.
After this, the fish know to allow the catfish to eat his food. The only other time the catfish goes on a biting rampage, there is too much chaos is happening with the other fish in the tank. The bluegills will be sparring off, or fighting over territory, the catfish will stop resting peacefully and take off mouth open.
Any fish he finds he will bite and if they don't move, he continues to bite and chase. Most of the bluegills get away without a bite, but a few get bit once, only two get bit two times. People think that you can scare a catfish away from it's home, look carefully, it will come back and bite your pole or even stab with it's fins.