I thought the interesting point of the article was underplayed like a buried lead: In the Kol, the majority of the population is resident, while in the more barren Utkholok, the majority are anadromous. At a conference on steelhead anadromy we held in Yakima two years ago, http://ykfp.org/steelheadworkshop/ there seemed to be two competing ideas about the reasons for anadromy: 1.) Fry in severe freshwater habitats head to the ocean. 2.) Fry in favorable freshwater habitats grew quickly to a size that made anadromy a better option. I tend to believe 1. because of the examples I'm familiar with. Using the old strontium in the otolith trick, Investigators in our region have found quite a range in degree of genetic exchange between resident and anadromous forms. Maybe it's because of the differences in the systems. In the Deschutes, most of the anadromous forms spawn in the small side streams, while most of the residents live and spawn in the main river. Is that because the small streams in the basin drastically dry up in the summer, leaving not much for a resident fish? And maybe that's why the degree of genetic separation between anadromous and resident was pretty high in the Deschutes. Genetic separation is lower but significant in the Walla Walla but not detectable in the Touchet. Cedar River steelhead and residents were also found to be closely related.