I wouldn't call it a partial clip. I think it is an endemic hatchery fish, which means a hatchery raised steelhead spawned from one or usually both wild parents, raised for just one generation in a hatchery, then released without an adipose clip. Any wear on the adipose you see is likely incurred by early life in a concrete holding pen. These fish are marked behind the eye with a florescent dot to alert the biologists which strain and year class the fish is. The idea is that this fish will spawn with wild fish, and because its genetics are "pure" it will add its genes to wild stocks to help bolster populations. Because hatcheries are more efficient than nature in offspring production, this is the states attempt to increase wild fish numbers.
Only BS is thinking we'd have SH and Salmon if there weren't hatcheries. With all of the man made stress put on these fish if there where no hatcheries there would be no wild fish, they did not evolve the ability to deal with the stress humans put on them through in so many ways. Commercial fishing, dams, polution etc. etc. etc.