Why go
Fish offers a useful alternative to the usual meat-centered picture of German food. A Fischbrötchen can be a quick coastal-style bite; Rollmops and Brathering show different preserved herring preparations. Farther inland, check for trout, carp or perch rather than expecting a sea-fish specialty.
The full story
Northern coastal cooking has long made room for herring and other sea fish. Pickled herring also traveled beyond the coast. It may appear in a Fischbrötchen, a fish-filled bread roll, as Rollmops, herring rolled around a filling, or as Brathering, fried and then marinated herring. Those names describe quite different textures and flavors, so they are worth distinguishing on a menu. Inland waters support another tradition: trout, pike, carp and European perch all appear as freshwater choices. Modern menus may also offer fish from farther afield, so the presence of salmon or tuna alone does not identify a local specialty. The contrast between preserved coastal fish and freshly prepared freshwater fish is the more useful clue when deciding what to try in a particular region.