Mongolian terror trout
In the north of Mongolia there are unspoiled rivers where Trout grow to enormous sizes, this guy's an Ichthyologist from America, he's been all over the world studying and tagging fish from the Mekong to Alaska.
I've seen him on TV wrestling with catfish 9 foot long, he always tries to catch the fish unharmed and returns them after tagging and weighing them.
The Mongolian Trout grow to 6 foot in length because there are no predators or poachers, it lets you see how the fish in our country used to be before we poisoned the rivers here and fished the species almost to extinction.