Swedes are obsessed with crayfish. In August, when the annual fishing season starts, families up and down the nation hold parties to celebrate. But what's so special about the tasty crustaceans? Feast ...

In many North American lakes, a tiny clawed creature has become a big bully. The invasive rusty crayfish roams lakebeds, snapping up snails, bivalves, and water plants, cutting off food supplies for ...