I'll pile on with congrats on some excellent photo work on the Sierra trout. It doesn't get a lot better than 'bows--brookies--and browns from the same water! My wife loves to sit at the bridge you featured, she calls it "watching trout TV".
The large head relative to body size is brought on by stunting due to feed insufficiency. It is seen more often in higher lakes that are ice-free fewer months of the year than lower-elevation lakes.