Salmon are a keystone species. They play a very important role in the health of an ecosystem. Some swim as much as 900 miles to return to the stream in which they were born to spawn. Why they do it remains a mystery. Joan Cartan-Hansen and her guests Jeff Heindel, Fish HatcheriesSupervisor, and Adare Evans, Wildlife Educator, both from Idaho Department of Fish and Game, answer students' questions about salmon.