The bagel with sturgeon is the premium top of the appetizing scale, and the defining element is the firmness of the fish. Smoked sturgeon does not flake or fold like the salmon and sablefish below it: it slices into firm, dense, almost meaty sheets, ivory-colored and assertively smoky. That structure changes how the sandwich is built. A firm fish does not need the cream cheese to hold it together the way a slippery cure does, so the cheese steps back toward a flavor role and the build leans on the fish's own body and clean smoke rather than on mortar.
The craft is the same boiled-then-baked bagel, assembled to show off a fish with real bite. A bagel is boiled before baking, which sets a tight, chewy crumb and a glossy crust strong enough to carry a substantial load without tearing, and it is left untoasted so the crumb keeps its pull against the firm flesh. The sturgeon is sliced clean and laid in even sheets rather than draped or flaked, because its texture is part of the appeal and folding it would waste it. The cream cheese is spread thinner than a delicate-fish build would require, present as a cool, tangy counter rather than as glue. The accents are kept deliberately spare, thin red onion and a little caper or lemon, because an expensive, clean-smoked fish is meant to be tasted, not buried under brine and acid.
The variations are positions on a graded scale of cured and smoked fish on the same bagel. Below sturgeon, sable is smoked, rich, and oily; below that, nova is mild and cold-smoked and lean; and whitefish salad is bound and mayonnaise-dressed rather than sliced into sheets. The carrier can shift to a softer onion bialy. Each of those sits on the same appetizing counter and deserves its own article rather than being crowded in here.