In Taipei we observed a dual Dutch fish auction, like a conventional Dutch auction with bundling, but with reversed roles of price and quantity. We study dual and conventional auctions with symmetric, independent private values, when agents’ utilities 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 auctions. With private values, the seller can prefer a dual Dutch or a conventional English or Dutch auction, but prefers all three to a dual English auction.