Excellent suggestions, those are remarkably good California sparkling wines, better than most champagnes. The Roederer would be better with cold fish, and the Ferrer with hot fish, fwiw. But isn't akvavit the traditional drink with gravad salmon?

If wanting to spend a lot more and get a nice champagne, try Perrier Jouet Belle Epoque. It has a floral, apple scent and light taste that would go well with most fish. By far the lightest of the "serious" champagnes (and so good that I recommend it, despite my taste running to heavy champagnes).