This is how I fed whole large sardines this weekend...
However.. someone told me to be careful with trout.. apparently they can be parasitic even when frozen. I can't say for sure though, as far as feeding it whole...well I can't see there being a problem but I would wait and see if any one else comments on the parasite thing before feeding it whole.
I think that you only have to worry about parasites in fish from the Pacific Northwest. If it from stream anywhere else you should be fine. I would probably let it thaw some before feeding it. The only frozen meat I feed my dogs is ground meat and liver/organs for Lola because she wouldn't eat them otherwise.
I leave the bones in. Whole sardines were Max's very first whole prey with blood, brain and all the rest of the animal. I also cut those 3 ounce sardines in half and introduced them a little at a time. If trout is new he may not want to eat a whole meal of it. I pushed the issue with a salmon head and Max didn't eat a bite of food for three days but he will eat a bit of new with mostly familiar food. Weird dog!
I live in Pennsylvania. My husband and his buddies went camping a few years ago. They were dressing their freshly caught trout and saw parasites. Yech, how gross. I think they were flukes or something. I am a little weary to feed them now