There have been a lot of posts on high lake food forms lately, and although very interesting and informative they pertain yo North American practises and rules. Here in Scotland, winter is the closed season for trout. So! most high loch (lake) fishing is done between March and October, thus the commonest target for them are chironomids, but a good selection of beetle and other land based insects are needed. Ours are a bit different, but I am sure anything related to the Coch-y-Bondhu, i.e. a nice plump peacock herl body and a selection of black buzzers will do the job. This is probably true on your high lakes as on our lochs.