I m with Augie, I dont think theres any way to keep them out of your pond. it all depends on what you do with them when they arrive. With the introduction of CC in QAs pond I think he will see a drastic drop in their numbers.
I got some of the craws from QA only to discover there were already a ton of them in my new pond. every one the young CC I caught were full of crawfish, they love them and I suppose can catch them pretty easily, I opened the stomachs of the CC to see what they were consuming and pretty much 100% of them had crawfish present.
That being said, It seems like I read somewhere on a thread on this sight that they are inferior quality of a food source, I dont know about that but my CC are doing extremely well, also in an older strip pit that I fished in a lot we would catch huge bass, we never did check any of the large bass but any bass we culled had craws in them and a Strike King rubber craw was their favorite lure, I still fish a lot with them to this day. but that was before the otters cleaned that pit out. they are slowly coming back and we are being able to catch a few again.