I don't really have an answer for OP, who obviously has a large, deep enough pond that raccoons aren't a problem. I know common goldfish will get 12-18". Grass carp get huge, but are considered invasive - I think they need to be sterile to import them to the US.
I would guess you quarantine new arrivals? I would if I had fish that expensive. Well, I don't have expensive fish and I still quarantine.
For smaller pond owners, I'm told that to be raccoon safe you need to have an area of your pond that is at least four feet deep. I removed my pond due to raccoons - they cleaned out my fish every year, and at the time I could not put in a pond that deep. Around here, herons are also an issue, but for some reason they do not like my yard nearly as well as my neighbors.