main stem is pretty good sized down near the mouth but gets smaller upstream pretty quick. the north fork, which is where i fish mostly, is real small...almost like a little trout stream, as is the south fork. north fork is fly only except for mid-winter, december or january for a month or 2, not really too sure, when you can fish bait for hatchery brat steel. it's very fun fishing, almost like spot and stalk, and the summer steelhead are known for eating surface flies...skating wakers or big caddis flies in a downstream swing across the water and a fresh chromer steelhead explodes on it.
you are right..it doesn't take much fish to crowd a small river, and i also don't think too many salmon or steelhead head up the south fork at all, so most that go up the main stem end up in the north fork.
the kings we do see are big!!
it's cool to be standing over one of those pools looking in and see 4 or 5 different species all in the same pool at the same time...you can really tell who the bullys are.