By the time Ishi arrived on the scene, game in California had already been seriously depleted by westward migration of settlers during the 1800’s. Because he was starving, plus the personal pressure he felt from seeing his own people hunted almost to extinction by soldiers, he was about ready to throw in the towel. I'm sure it was always difficult, even in the best of times, to survive on a diet of wild game plus whatever nuts and berries could be scrounged, but by Ishi's time it had become impossible. Which is to say that Ishi's own hunting skills may have been somewhat degraded from those of the generations before him.