When Denmark realized a few years ago that it had an oyster invasion, it turned the problem into a tourism opportunity, inciting people to gather up the pests and eat them. It wasn’t too difficult: Danes and oyster-eating go way back, at least to the Stone Age, as evidenced by ancient heaps of discarded shells called kjökkenmödding. In 1587, King Frederick II made oyster fishing a royal monopoly—those who broke the law three times risked the death penalty.
For most of their history, Danes ate the Ostrea edulis, a flat species indigenous to Europe that also goes by the name Belon (though this appellation is normally reserved for those that come from an estuary in France). But overfishing, pollution and disease have driven the flat oyster nearly to extinction, so the Pacific oyster, or Crassostrea gigas, is now the type most people eat the world over. Introduced from Asia to the United States in the early 20th century and to France in the 1960s, the Pacific is more resistant to parasites and variations in temperature. However, in some places—including the western coast of Denmark—it has become an invasive species, blanketing the sea floor like beds of concrete. MORE