Not a fish bio, but I have friends with with the forest service who told me that on stocking lakes, usually it's by chopper. They used to drop brookies in those remote lakes with no outlet. One time I horsepacked some trout into a lake in the high country near the town of Merritt BC. Had a pretty good survival rate since the water sloshed around a lot in the boxes we were using. Since it was a relatively short pack, it didn't get too warm.

I understand there are other species that do well in some of those lakes as well. I found the best way to catch those trout is to cast a a dry fly or small rooster tail with a clear casting bobber as far out as you can. I have seen big trout caught by guys who brought small rafts up on their pack horses. Most of the brookies I have caught up there were pretty small. There is an excellent lake system in the Cascades that can be accessed from the Pacific Crest trail.

This area is called the William O. Douglas wilderness. Go north from the white pass trailhead at Leach Lake. Between White Pass and Chinnok Pass, there are a lot of great lakes and good hiking. The trails should be accessible by early to mid July. I hope this helps.