When talking about mesh size I will add an experience I had, was keeping some 4' to 6" fish in a cage to be used for catfish bait so obviously didn't need a real fine mesh, we had several snakes slide in thru the mesh and gorge themselves with fish, they obviously couldn't get back out with fish inside them but the did a number on our bait fish.
I have had them do the same thing in minnow traps.
