Something bright flashed near the surface of the murky James River. Will McCahill swung at it with a net and caught a piece of living history. "Gentlemen, this is what it's all about," said boating partner Chip Augustine, eyeing a handsome 18-inch fish with silvery, iridescent scales. The prize was an American shad -- probably the most important fish you've never seen. The shad, which migrates from the sea to freshwater rivers in the spring to spawn, once fed hungry Indians and settlers at winter's end. It supported a huge Virginia fishing industry. Thomas Jefferson caught shad. Legend has it that migrating shad saved George Washington's troops from starvation at Valley Forge. "This country was founded on American shad," said Augustine, with a nod toward a 2002 book by outdoor writer John McPhee, "The Founding Fish." How did Americans express their thanks to shad? We built dams that blocked them from spawning territory, polluted their waters, and caught way too many to obtain their roe and tasty-but-bony flesh. The shad responded by nearly dying out. McCahill and Augustine, employees of the state Department of Game and Inland Fisheries, were catching shad near the Mayo Bridge in Richmond early this month to check on their numbers. The men are part of a $200,000-plus yearly effort to bring back the shad. But for reasons that mystify scientists, the shad aren't coming back.