calicreekcatcher's Identifications

This is the fish that shut down Atascadero Creek in 2013. You can't see it in the photo, but it's hovering over its nest.

Lisa Thompson (UC Davis) told me this about the sacred fish:

Rainbow trout and steelhead (trout) are the same species, Oncorhynchus mykiss. The only difference is that steelhead migrate to the ocean, where food is generally more abundant, so when they return to freshwater to spawn they are larger than the "resident" rainbow trout who spend their whole life in freshwater. The trade-off for the steelhead is that they have to brave the more dangerous ocean conditions, with larger predators, in order to gain the size and reproductive advantage. The larger the female, the more eggs she produces.

Interestingly, steelhead mothers can produce rainbow trout offspring, and vice versa. In southern California, where long droughts have occurred historically, this flexibility in life history probably helped the trout to survive. If the creeks didn't flow enough to break through the lagoon sandbars for many years in a row, any steelhead out in the ocean would have died without reproducing, but the population could have been maintained by the resident rainbow trout in the creek headwaters (e.g., Rattlesnake Creek up above Mission Creek - the first place I saw southern steelhead trout). Once a good rain finally arrived, some of the rainbow trout offspring would have converted to being steelhead, migrated to the ocean, and returned to freshwater large and able to rapidly increase the population size.

In California the steelhead between Santa Cruz and Santa Maria are listed as threatened under the federal ESA, and between Santa Maria and the Mexico border they are listed as endangered. There are steelhead as far south in California as Camp Pendleton, near Oceanside, and I've seen rainbow trout in the Tijuana River east of San Diego. There are also a few isolated populations of trout in the highlands of Baja California, and east of the Gulf of California in Mexico.