On some Oregon streams and off our coast the clipped adipose is definitive evidence of a hatchery fish (usually used for steelhead and salmon). Other fins and jaw hinges may be clipped to code source hatcheries and release points or dates. Those injuries must be completely healed over. Looking both ways and pulling out a pair of clippers is not going to generate a legal keeper.
Over all fin condition is an excellent indicator of a fishes birth place and a watchfull eye can separate hatchery and wild stocks even with the adipose present. In the crowded hatchery tanks, there is constant bickering over space, and each appendage serves as a handy bite target. That being, nearly all fins will exhibit irregularities along the edges, curved and inconsistent veination, and will be generally shorter than wild fish. The flattened lower surface of a tail is also evidence of life in a cement tank, but it can also be evidence of spawning activity in mature fish. Some of the hatchery stock may also be carrying PIT tags about the size of a grain of rice. Those can be read via sensors in fish ladders or narrower constrictions in streams. I've lost my favorites list due to a PC crash, but there is an Oregon/Washington web site somewhere that publishes daily counts of PIT tagged fish. Fairly helpful for establishing when given runs begin, end, or peak. Here's one link that I found with a brief search:
PIT tag data Stream born fish have ample space and experience less intraspecific competition or aggression. With the exception of aged spawners, their fins are typically perfect in every way, with the dorsals being up to 30 or 40% longer than hatchery stock. That being, the white fin tips are usually present too on stream born rainbow related stocks.
