The original rainbow trout come from Oakland; did you know that? The species Salmo iridia was first described, in 1855, from San Leandro Creek. Redwood Creek is a branch of San Leandro Creek that still contains good spawning grounds for rainbow trout, and this nicely maintained fish ladder is here to help them upstream.
The rainbow trout has been spread all over the world, of course. This wasn’t the only locality in the Coast Ranges they came from. The Oakland fish aren’t superior to other local strains. Their only distinction is artificial: they’re merely the first to come to scientific attention. Naturalists name species simply by picking an individual and describing it in detail in the literature. It’s arbitrary, but the only way to begin.
That’s as arbitrary as the creationist’s crude notion that the species is simply something uttered by God and named by Adam. Creationists don’t care to ask why populations vary in their genetic makeup—or if they do they regard it as the necessary decay from perfection of all earthly things. Variation is useless in their theory. But to naturalists, the reality of the species includes precisely the variation that the creationist downplays. Variation is the first rung in the ladder of evidence showing how the tree of life fits together as the result of evolution. The creationist’s interest in that project is only to suppress it.
Today we lump Salmo iridia as a subspecies under the larger species Oncorhynchus mykiss. Maybe God isn’t clear, or maybe our ideas need work. Maybe both statements mean the same thing.