Dominic, welcome to the forum.
I have a quarter acre pond with many species of fish, LMB, SMB, YP, BG, GSF, HBG, BCP, and TGC. I've kept rainbow, brown, and tiger trout somewhat successfully for 15 years. Trout mortality approaches 50% each year.
It's very likely the trout eat some of my other fish. Except that they may be preying on my yellow perch, I'm fine with them grabbing any of the others.
If you haven't seen it yet, read Mark Cornwall's article in the latest Pond Boss magazine titled Stocking Trout-Some Questions Answered. He is quite thorough in his discussion. His opinion is that 50% loss per year is to be expected without perfect conditions. I'm very careful to avoid catching our trout when the surface water temp is above 70 even though the fish want to come up for a fly. I've had 7 pound rainbows float belly up a day or two after being caught and released in the summer.
Our pond is fed by Dolores River water through an irrigation canal system. The Dolores is a trout stream. My pond surface water temp yesterday was 78 degrees; incoming cold water stays on the bottom providing great habitat for the trout. So, you could say my pond is stratified in a manner different from a pond without the cold inflow.
