I picked up a couple really funny looking humpies out at Sekiu recently, really large fish and the tails were overlain with silver radience like a coho - was actually releasing the first one as it of course had an adipose fin until I noticed the maxilary, which has a straight edge on humpies, chum, and sockeye and is curved downward on kings and coho. After I got it in the boat and subdued it I was able to finally see the faint tail spots under all the silver radience, but it was really tough to pick up until the fish was dead. Anyway, that maxilary bone is a great indicator - if it was straight it was not a coho.