Coho or Chinook – it’s in the gum line

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.


Coho salmon: white gum line.

Coho salmon:  white gum line.


Chinook salmon black gum line.

Chinook salmon:  black gum line.

I hope this helps anyone who has this question, and my best to you all.

Jay Nicholas, October 2019

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5 Responses to Coho or Chinook – it’s in the gum line

  1. Pat says:

    Another way to distinguish coho from chinook is on the tail. Coho have ridges on their tails that you can feel with your thumbnail, similar to the ridges on a quarter; chinook don’t. The gum line is the easiest method; the tail method can be a confirmation.

  2. Oregon Fly Fishing Blog says:

    Rodger that and thank you. The coho’s tail will also “collapse” whereas the Chinook’s tail retains its shape and remains “firm”if you grasp it. JN

  3. Erik Stowell says:

    Great post Jay! I’ve faced this dilemma a couple of times, once almost pulling an ~18 lbs coho out of the water to take home on Lake Creek a few years back. Fortunately took a second a second look at the mouth and noticed the white gums.

  4. Oregon Fly Fishing Blog says:

    I’ve certainly been there — thinking a fish is so large that of course it must be a Chinook, and after all, it isn’t spinning up in my line or leaping like a coho …. so it is always a good idea to make sure sure sure …. thanks for your note Erik. JN

  5. Ted says:

    Thank you for this!
    It is a frustrating dilemma for a beginner to be tossed around with a net in one hand, getting soaked with waves, leaning over the side of the boat and trying to see a gum line inside a fish’s mouth under their lip.
    But this helps a lot.

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