I am no expert but it makes me wonder what happened to the fish you stocked. With a lake that big it is hard to believe they are all gone. Putting in more fish without knowing is a big gamble. Is there a predator species you may not know is in there, is there a creek or channel or over flow that allowed them to escape? You haven't seen any floaters? I'm assuming you stocked a mix of known males and females. Like I said I'm no pro just some thoughts.
Currently on the lake we know of Otters, Beavers, Loons, Cormorans and Cranes. Of those, The worst would be the Otters and the Cormorans for eating the bigger trout. One thing we did as well was stock it in the spring and not in the fall or right before it iced over. If we had to redo it, I would stock in the fall right before it freezes to give them at least a chance to stay clear of the birds. Even some folks up here cut a hole in the winter and stock it once it is iced over. There is an outlet creek but it dries up when the water is low and it dumps into another Smaller lake we have access to and that one is full of Rock Bass and Smallmouth. The landowners there have never told us they caught trout.
