The oyster Crassostrea gigas has wide geographic distribution and, for many years, represents the highest annual production of any aquatic organism.
The economic importance of oysters motivates a great deal of biological research, which provides the most immediate scientific rationales for sequencing ESTs.
Strong rationales also come from membership of oyster to the Lophotrochozoa, an understudied branch of bilaterian animals with limited molecular data today. With high fecundity and concomitantly high DNA polymorphism, this species also constitutes a good model for population and genetic studies.
Finally, oysters play an important sentinel role in estuarine and coastal marine habitats, where increasing human activities interfere with exploited populations that may suffer from mortality related to diseases and stress.