Feeding on dead Kokanee while also seemingly stirring up the bottom probably looking for fish eggs.
To me, this looks just like the drawing in The Laws Field Guide to the Sierra Nevada, with the "exclamation points" and the "hourglass mark" (but doesn't look like the photos in the iNaturalist species account). So I hope someone can confirm or set me straight.
Somewhat worse for wear...
The spawn is on! This little waterfall was a fun obstacle to watch.