The Founding Fish

John McPhee's twenty-sixth book is a braid of personal history, natural history, and American history, in descending order of volume. Each spring, American shad-Alosa sapidissima-leave the ocean in hundreds of thousands and run heroic distances upriver to spawn.

McPhee—a shad fisherman himself—recounts the shad's cameo role in the lives of George Washington and Henry David Thoreau. He fishes with and visits the laboratories of famous ichthyologists; he takes instruction in the making o…