How can you tell a catfish bite from a alligator gar bite?

im fishing about a foot off the bottom near a fallen tree using chicken liver. and every time the fish takes off with my pole and i atempt to set the hook i miss him, this has happened like 5 times in a row, same spot, and i know a gar is hard to mouth hook. can anyone tell me? i know for a fact its not a turtle because when it hits my bait, if im not there to hold it then my pole will go in the watER.