Big Fish is ancient and enormous. In her 177 years she's brushed against death more than once -- stalked by panners in the gold rush of 1858, nearly crushed in a rock slide in 1913, almost stranded when the lake drained into the river in 1924, and threatened by a mysterious disease that killed many other sturgeons in the early 1990s. Since then, sport fishers have hooked her several times, and she's led them through quite a chase. But today scientists...