The question always, always comes up this time of the year, and is especially common this year because the coho salmon run is more abundant than usual, and people are catching more of these fish than they do in other years when the run to the rivers is smaller.
How can I best distinguish coho (silver) salmon from Chinook (king) salmon?
Size isn’t a good test, and features like spots on the tail and tail-firmness are elusive to many people, especially when large bright coho and small bright chinook are concerned.
Here is the diagnostic feature I suggest to classify a salmon as coho or chinook.
I look closely at the gum line, the channel where the teeth are embedded. The Chinook have a black gum line and the coho have a white gum line – without exception, and this is true whether the salmon are chrome fresh from the sea or in a well advanced state of maturity and full of bright colors.
Here are two images to show the feature I refer to. with coho on top and chinook on the bottom.
FYI both of these salmon are males, bucks, and have the characteristic kype (hooked snout) that develops as the fish mature sexually.
I hope this helps anyone who has this question, and my best to you all.
Jay Nicholas, October 2019