I wondered about the ending, too - because everything was told from the father's perspective, given what happened to him I think maybe it's a story he told himself about what happens after he goes, to give him hope. I'm not sure if it really was that simple, ultimately.

What really killed me was the short paragraph about the trout at the very end. When I read that, I basically broke down with the full weight of everything that had been lost. Not just the life, or the ecology of the system, but that ecology in the context of everything that had come before, with remnants of impossibly ancient processes manifested against one another. Ultimately, it's the end of evolution, and the loss of all of those products of deep time...an inexorable END, that killed me.