CHINOOK — It’s a good thing the area at the mouth of the Columbia River known as Buoy 10 actually is a couple of miles wide and 16 miles long. Salmon fishing at Buoy 10 is good most years. But in 2015, it was record-setting with 36,535 chinook kept and 22,179 released. “Last year was just epic,’’ said Robert Moxley of Wilsonville, Ore., a serious Buoy 10 angler and member of the bistate Columbia River Recreation Advisory Group. No doubt, boat ramps and fish-cleaning stations will be crowded, camping spots and hotel rooms scarce, and the prime angling spots jammed with vessels in August for the 2016 version of the popular late-summer salmon fishery. Fishing at Buoy 10 — the water between red Buoy No.