POS is pretty much correct. Most steelhead outmigrate and smolt as two year olds with some residual 3 and 4 year olds. Just about all less than a foot in length, most less then 8 inches. A 14 inch resident trout has got to be an oldster that has spawned several times.

Also many streams have river specific regs that supercede the general regs where further protection is necessary (e.g., Yakima R; other streams with sea-run cutt populations). Bottom line, if you're not going to restrict steelheaders from incidentally catching smolts, you can't restrict trout anglers. Size and seasonal restrictions are the best things that can be done.