At the Eaton Street Seafood Market in the historic district of Key West, Fla., a long glass case displayed a who’s who of the city’s seafood scene: plump piles of pinks (the local shrimp) snuggled next to a yellowtail snapper, a mound of stone crab claws and fresh slabs of grouper. I’d come to eat my way through Key West’s delicacies, and here was my map.