Here's a reliable one for prawns (and crab too): Hoonah Sound, to the NW off Peril Strait, some 50nm north of Sitka. And there's a very nice anchorage (except in strong S wind) there at Half Tide Neck.
We've also done quite well on prawns in Tlevak Strait, south of Hydaburg.
Neka Bay, off Port Frederick, south of Hoonah, is very good for dungies - especially early in the summer before the commercial folks have taken too many. You can see a zillion pot floats there, and still be able to find a spot for a pot or two and pick up some nice ones. I set a single pot there once, and in the morning had 11 dungies, 9 of which were keepers. Lovely anchorage too.
Another favorite anchorage that used to have good crabbing near the NW head of the inlet is Blunden Harbour, on the BC mainland north of Port Hardy. Haven't been there in a few years though.
Anyone have more to share?
Dream Catcher (Nordic Tug 37)
New Moon (Bounty 257, Volvo KAD44P)
"Cruising in a Big Way"