This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
I spent most of the month of May in Alaska, and most of that sitting in an AirBnB in North Pole abiding by the required 2-week indoor quarantine for travelers from out-of-state due to Covid-19. After the quarantine came a frantic sequence of fieldwork to train the technician we hired to complete our second summer of data collection on a study of food resources for juvenile Chinook Salmon in the Chena River. However, our weather-dependent sampling schedule allowed for a break from May 29th-31st, and I drove south to chase rainbow trout.