At the end of their arduous trek across the country, Lewis and Clark were sitting around their campfire with the roar of the surf of the Pacific in the background when Lewis said, “I’ve been thinking.”

Clark replied, “Not again. What are you thinking about this time?”

“Well” Lewis said, “I’ve been thinking about these remarkable fish, the salmon. They are beautiful and good to eat. And they regularly come into the rivers from the ocean. Then they are so easy to catch. They swim from the ocean up to tiny streams where they started life, dig their eggs into the gravel and th...