Hatchery fish spawn in the wild all the time - generally not too successfully, and particularly not on the Penninsula, where winter rains typically wipe out redds - most natives spawn April - June for this reason.

I caught and released one of those today on the 'Nooch - adipose clipped spawned out summer hen about 30" long - fun while it lasted.
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The fishing was GREAT! The catching could have used some improvement however........