Intrek
Interestingly a surprising number of pocket waters in the Sierras have black bullheads, presumeably brought up from the Sacramento area by birds. Lakes with resident free range cattle often have no remaining native species, but the bullheads do well in the polluted water.

However any wild fish in the Sierra, or remaining plant, should be carefully released, because there are so few and their existence is threatened, especially the Golden, which I have only been fortunate enough to see a few of and never caught one.
Jim
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These are my own opinions based on wisdom earned through many wrong decisions. Your mileage may vary.