There are both resident rainbow trout and juvenile steelhead that have yet undergone smoltification in the river. The difference is hard to tell, but one just have to remember that all wild trout and char have to be released. A wild trout or char will have its adipose fin intact while a hatchery-raised trout or char's adipose fin is missing and a healed scar is in place. If you fish the lower section, particularly in the canal area, you may also encounter cutthroat trout this time of the year. Most of the bull trout/dolly varden are caught further upstream.
Float fishing with bait such as roe or dew worm is of course very productive but rather ineffective if one chooses to catch and release since the fish tend to swallow the hook this way. An alternative would be to replace the baited hook with a small fly such as a leech or stonefly nymph. Small spinners or spoons should also work very well. For spinners, choose them with a size 2 or 3 blade. For spoons, 1/8oz or less are best. Preference in colour does not really matter, as trout and char are usually aggressive and will strike on anything that move in the water.
Good luck Sandy, maybe you'll hook a coho too.