Can someone help me with this fish and pond situation?

Alright there is this pond I have been fishing at my whole life. It's a natural structure the size of a football field deep in southeast TX. A large creek runs into it. My grandpa and dad have caught a 12lb b and large catfish it a good decade ago. But I cant catch any catfish larger than a pound mud cat. The b are still there, very large gar,I still see them. I noticed that there are a whole lot of snakes and turtles in there. the pond is about 12ft deepest and good structure for fish, why cant I catch large catfish? I wanna know if the sankes and turtles could be affecting the fish. I have even seen logger head turtles in there as big as table tops,soft shell too. If they are the problem then I can take em out with my 22, just say the word. I do put trot lines and drop lines in there and the next day the bait is gone, entire perch and shad. I know turtle do this, but I just cant see how they could have dissapated large catfish throughout the years. Help me please.