Who is Grand Old Trout from Richard Brautigan's Trout Fishing in America ; the Pill Versus the Springhill Mine Disaster ; and, in Watermelon Sugar and what is their importance?

Grand Old Trout is the wise old fish who tends to stay upstream from iDEATH. He does, however, make his way downstream to observe the construction of a tomb that collapses. The trout recognizes the narrator, gives him a good look, and then proceeds to turn his attention back to the reconstruction of the tomb.