Today and tomorrow only, Aquarium of the Bay at Pier 39 is playing host to a 25-foot-long, two-ton salmon called "Fin." It's part of the travelling road show by an organization called "Save Our Wild Salmon" that hopes to curtail the depletion of endangered salmon in the Northwest by building support to remove the four lower Snake River dams in Washington State. The road show, called "Extinction Stops Here!" has in recent days been in Marin, Vallejo, Oakland, and Berkeley....