The run-up to Turkey Day means one thing in San Francisco: local Dungeness. And when crab makes its annual reappearance here, things get frantic at Swan Oyster Depot on Polk, which gets daily deliveries from Pier 45 at Fisherman's Wharf. Save your crab cakes, your avocado and blood orange salads, and your bisques for later in the season. At the very start, when the Dungeness are at their sweetest and most succulent, aficionados want the crustacean unadorned, boiled and cracked, served with lemon and a glob of mayo, with sourdough and butter. Photographer Gil Riego Jr. scoped out Saturday's Dungeness faithful at space-challenged Swan's, which is both café and seafood market, to witness a local tradition.