I don't think that the ethics are any different in the Great Lakes regarding what fish are targeted.
We have a totally different situation here for fishing than in the PNW. Our fish generally come in big/gigantic pushes that are dependent on rainfall. It's a very short time frame, with the fish going in and out of the river system in short order. I can not think of many systems in the entire Great Lakes that has a run of steelheads in it for the entire year. This is mainly dependent on water temps, flow levels during the late spring/summer months
We like freshies just like you do, but the fact of the matter, is that in dry springs, our fish have loose eggs when they hit the river. It is totally common, to catch chrome bright hens in the spring that are running loose eggs when you unhook them. Yes, alot of the guys like myself release most of the brats they catch too.
We have many places where sanctuaries exist to protect fish that are spawning. Certain sections of rivers are off limits to fishing. Some rivers have closed seasons while the fish are in the wintering over mode, so they aren't harassed prior to spawning in the spring. This is somewhat common on rivers that have good poplulations of wild fish. It is also prevalent in areas where there are hatchery terminals or wiers for egg collection.
We catch a fair share of post spawn fish, but they generally blow out in to the lake after doing their thing, as water temps rise dramatically. Our fisheries are largely put and take. The DNR plants them, they grow up, and the fisherman catch them. I can tell you that some rivers with about 4 miles of fishable water , get in excess of 125,000 plants per year. Our wild fish are treated with the utmost care, as they are not as prevalent as the brats.
As a conversation piece, I will pose the following question. What is the difference in targeting fish that are coming in to the river to spawn, vs targeting a fish that has already spawned? In the purest sense, we would not fish at all, as all fish are either a pre spawner (whether in the salt or in the river) or a post spawner. Is it more ethical to chase a pregnant woman, or one that just gave birth?