What is this red and black fish?

Just this year I have seen two odd fish in a pond that I've fished for many years in south eastern Ontario. The fish have a black back and fins, and orange/red side and belly. they are about a foot long and have a slim body similar to a trout or pike. Pond has a short inlet from the St. Lawrence so many types of fish come into the pond but I've never seen these before. I have tried to catch them with all types of baits but they're not even interested. I thought they might be brown trout but my dad who is an experienced fisherman said he has never seen any fish like it. The water is high this year and unusually weedy, maybe this has something to do with the sudden appearance? They fish have been in there for a couple of weeks.