In Taipei we observed a dual Dutch fish auction, like a conventional Dutch auction with bundling but with the roles of quantity and price reversed, and fish the numeraire rather than money. This paper uses a symmetric independent private values framework to study how duality interacts with auction form when agents' utility functions are linear in money but strictly concave in fish. With known buyers' values, conventional and dual auctions, English or Dutch, are equivalent. With values known to buyers but not the seller, the seller prefers conventional to dual auctions. With privately known values, the seller can prefer either a dual Dutch auction or a conventional English or Dutch auction, but he prefers all three to a dual English auction