Here's a pic of a similar sky fish from two summers ago that at least touched saltwater... I helped a guy land his first steelie and thought to myself that it was the smallest saddest looking summer run id ever seen. Then I stepped out and hooked one myself. Both fish were perfectly chrome sea liced bucks and both hatchery.
Congrats on a very nice fish! Which with its adipose fin a wild one.
The fish in question is not a half-pounder. The center of the half pounder steelhead life history is the Klamath river basin with them common in northern California and southern Oregon. A half pounder is a steelhead that after smolting spends 2 to 4 months rearing in the estuary or near shore areas only to return as immature fish to over winter in freshwater before returning to the salt for additional growth before returning as an adult steelhead. This behavior is very similar to what we see here on the larger north sound rivers with sea-run cutthroat and bull trout; that is immature sub-adult fish after a short period of marine residency return to freshwater (may or may not be their natal system) to over winter. While half-pounder have been seen in Puget Sound such fish are exceedingly rare.
Daniel's fish clearly is in a post spawn condition indicating that it is an adult thus not a half-pounder. There are 3 life histories that might account for an O. mykiss adult of that size that would be found in a north Sound river. The first would be a 1 salt summer steelhead. Such fish are usually 24/25 inches long though they can vary from as little as 19 inches to more than 30 inches long. Some years quite a few of those one-salt fish in our local rivers are in the 19 to 21 inch range. This time of year a fresh run fish would be chrome bright; the spawning of the wild summer fish is from March to about mid-May so encountering an post spawn adult this time of year is not very likely.
The second life history would be winter fish that returned as a "jack". A male fish that matures a year early returning typically at a size of 15 to 17 inches. These fish are capable spawners and occasionally will survive to return to spawn a second time. Such fish would often be in the size range of Daniel's fish and would expect a small handful of such fish to be found in a health wild population of significant abundances.
The third life history as all ready referred to is the resident form/rainbow. Resident rainbows are becoming more common on some of our north Sound rivers and such fish can reach the size of the one pictured more often than some would think. Our resident rainbows in our steelhead rivers typically mature at age 4 at a length of 14 or 15 inches. They experience much higher post spawn survival than their anadromous cousins (repeat spawner rates at 50% or so). They will often grow 2 to 3 inches between spawning and may survive to spawn 6 or more times achieving lengths of more than 24 inches in the process.
It is most likely the fish in question is a resident rainbow but without a scale sample it would be impossible to say with certainty.
I guess it is possible that it was not a little A run but I'm not going to kill the high Daniel was on after catching it. I pulled the fly out of it's mouth myself and was pretty sure onsite and in person it was steel. Chalk it up as the first landed Steelhead of your career and move on to the next!! Good job Daniel!!