I stumbled across this. It's rather good. Never heard of black finned trout before :)
https://www.youtube.com/watch?v=bV2YXWHckKY
Nice wee video. Drops a lot of fish that boy...
It's good although I'm sceptical about the black finned trout. I've caught a lot of large tailed, dark fish but can't say I noted the fin colour. One high loch I know the fish are very dark, always in great condition ad fight like hell.
Trout are considered to be about the most varied fish there is ... "polymorphism" ... many forms. Every one a bit different and some a lot different!! Half the fun is the lovely variation.