Across the globe, shellfish are becoming increasingly relied upon as a source of healthy proteins and fats. In 2010, more than a third of world aquaculture was composed of mollusks and crustaceans, two important classes of shellfish. In the U.S., burgeoning aquaculture industries in the Pacific Northwest threaten expansion into open ocean waters as marine and estuarine environments are already occupied or unsuitable for shellfish production.
While current shellfish aquaculture produces less environmental damage than factory fish farming, this is likely to change as the industry expands to meet high demands. Shellfish monocultures can lead to reduced biodiversity, altered and endangered marine ecosystems via consumption of nutrients and attraction of predators, introduction of non-native species and disease, and biological and chemical pollution.
 Shellfish, New World Encyclopedia, http://www.newworldencyclopedia.org/entry/Shellfish (last modified Oct. 16, 2008).